diff mbox series

V2 [PATCH] ldconfig/x86: Store ISA level in cache and aux cache

Message ID CAMe9rOrBF8=pJn-VEQC9_cS_uzithBmo_ggeCFfAKnFfpjAfHw@mail.gmail.com
State Committed
Headers show
Series V2 [PATCH] ldconfig/x86: Store ISA level in cache and aux cache | expand

Commit Message

H.J. Lu Jan. 12, 2021, 11:32 p.m. UTC
On Tue, Jan 12, 2021 at 8:25 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 09/12/2020 00:27, H.J. Lu via Libc-alpha wrote:
> > On Tue, Dec 8, 2020 at 7:31 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>
> >> On Tue, Dec 8, 2020 at 7:16 AM Florian Weimer <fweimer@redhat.com> wrote:
> >>>
> >>> * H. J. Lu:
> >>>
> >>>>>> For each file entry for a shared object, the hwcap field has been used by
> >>>>>> DL_CACHE_HWCAP_EXTENSION for glibc-hwcaps.  Are you suggesting
> >>>>>> to add another file entry for the same shared object to store ISA level
> >>>>>> requirement?
> >>>>>
> >>>>> It's a 64-bit field.  We do this:
> >>>>>
> >>>>> /* This bit in the hwcap field of struct file_entry_new indicates that
> >>>>>    the lower 32 bits contain an index into the
> >>>>>    cache_extension_tag_glibc_hwcaps section.  Older glibc versions do
> >>>>>    not know about this HWCAP bit, so they will ignore these
> >>>>>    entries.  */
> >>>>> #define DL_CACHE_HWCAP_EXTENSION (1ULL << 62)
> >>>>>
> >>>>> /* Return true if the ENTRY->hwcap value indicates that
> >>>>>    DL_CACHE_HWCAP_EXTENSION is used.  */
> >>>>> static inline bool
> >>>>> dl_cache_hwcap_extension (struct file_entry_new *entry)
> >>>>> {
> >>>>>   /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
> >>>>>      is a different kind of extension.  */
> >>>>>   return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
> >>>>> }
> >>>>>
> >>>>> So we can use a different bit pattern involving DL_CACHE_HWCAP_EXTENSION
> >>>>> to express something else.  In particular, only the lower 32 bits are
> >>>>> currently used as an index.
> >>>>
> >>>> So bits 33-47 can be used for ISA level requirement.  This should support
> >>>> 65536 ISA levels.
> >>>
> >>> The question is whether the ISA levels and the glibc-hwcaps name are
> >>> used in parallel.  If not, we can use  (1ULL << 62) | (1ULL << 32) as
> >>> the marker bits and a 32-bit index in the lower half.
> >>>
> >>> (I do not think this is necessarily relevant for levels, but it could be
> >>> used for locating objects according to other criteria.)
> >>>
> >>
> >> I think ISA level and glibc-hwcaps should go together.
> >>
> >
> > Here is the patch to store ISA level in the portion of the unused
> > upper 32 bits of the hwcaps field in cache and the unused pad
> > field in aux cache.
> >
> >
> > From f5053fabd1e8a5567b487ef4054793e043a7b817 Mon Sep 17 00:00:00 2001
> > From: "H.J. Lu" <hjl.tools@gmail.com>
> > Date: Sat, 5 Dec 2020 07:01:58 -0800
> > Subject: [PATCH] ldconfig/x86: Store ISA level in cache and aux cache
> >
> > Store ISA level in the portion of the unused upper 32 bits of the hwcaps
> > field in cache and the unused pad field in aux cache.  ISA level is stored
> > and checked only for shared objects in glibc-hwcaps subdirectories.  The
> > shared objects in the default directories aren't checked since there are
> > no fallbacks for these shared objects.
>
> Some comments below, most minor changes and code organization.  The main
> change I would like is to improve test coverage, as for the first patch.
>
> > ---
> >  elf/cache.c                                   | 34 +++++---
> >  elf/dl-cache.c                                |  4 +
> >  elf/ldconfig.c                                | 18 +++--
> >  elf/readelflib.c                              | 81 ++++++++++++++++++-
> >  elf/readlib.c                                 |  7 +-
> >  elf/tst-glibc-hwcaps-2-cache.c                | 45 +++++++++++
> >  .../etc/ld.so.conf                            |  2 +
> >  .../postclean.req                             |  0
> >  elf/tst-glibc-hwcaps-2-cache.script           |  6 ++
> >  sysdeps/generic/dl-cache.h                    | 15 +++-
> >  sysdeps/generic/dl-isa-level.h                | 26 ++++++
> >  sysdeps/generic/ldconfig.h                    | 22 +++--
> >  sysdeps/generic/read-prop.h                   | 35 ++++++++
> >  sysdeps/unix/sysv/linux/arm/readelflib.c      | 22 ++---
> >  sysdeps/unix/sysv/linux/ia64/readelflib.c     | 22 ++---
> >  sysdeps/unix/sysv/linux/mips/readelflib.c     | 22 ++---
> >  sysdeps/unix/sysv/linux/powerpc/readelflib.c  | 22 ++---
> >  sysdeps/unix/sysv/linux/riscv/readelflib.c    | 22 ++---
> >  sysdeps/unix/sysv/linux/s390/readelflib.c     | 22 ++---
> >  sysdeps/unix/sysv/linux/sparc/readelflib.c    | 22 ++---
> >  sysdeps/unix/sysv/linux/x86/read-prop.h       | 61 ++++++++++++++
> >  sysdeps/unix/sysv/linux/x86/readelflib.c      | 23 +++---
> >  sysdeps/unix/sysv/linux/x86_64/Makefile       | 31 +++++++
> >  .../sysv/linux/x86_64/tst-glibc-hwcaps-2.c    | 61 ++++++++++++++
> >  .../linux/x86_64/x86-64-isa-level-VALUE.c     |  4 +
> >  sysdeps/x86/dl-isa-level.h                    | 32 ++++++++
> >  26 files changed, 550 insertions(+), 111 deletions(-)
> >  create mode 100644 elf/tst-glibc-hwcaps-2-cache.c
> >  create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
> >  create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/postclean.req
> >  create mode 100644 elf/tst-glibc-hwcaps-2-cache.script
> >  create mode 100644 sysdeps/generic/dl-isa-level.h
> >  create mode 100644 sysdeps/generic/read-prop.h
> >  create mode 100644 sysdeps/unix/sysv/linux/x86/read-prop.h
> >  create mode 100644 sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
> >  create mode 100644 sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> >  create mode 100644 sysdeps/x86/dl-isa-level.h
> >
> > diff --git a/elf/cache.c b/elf/cache.c
> > index b03c5319f8..91a72381ae 100644
> > --- a/elf/cache.c
> > +++ b/elf/cache.c
> > @@ -145,6 +145,7 @@ struct cache_entry
> >    struct stringtable_entry *path; /* Path to find library.  */
> >    int flags;                 /* Flags to indicate kind of library.  */
> >    unsigned int osversion;    /* Required OS version.  */
> > +  unsigned int isa_level;    /* Required ISAL level.  */
>
> Maybe a typo here 'ISAL'?

Fixed.

> >    uint64_t hwcap;            /* Important hardware capabilities.  */
> >    int bits_hwcap;            /* Number of bits set in hwcap.  */
> >
> > @@ -660,8 +661,14 @@ save_cache (const char *cache_name)
> >         if (entry->hwcaps == NULL)
> >           file_entries_new->libs[idx_new].hwcap = entry->hwcap;
> >         else
> > -         file_entries_new->libs[idx_new].hwcap
> > -           = DL_CACHE_HWCAP_EXTENSION | entry->hwcaps->section_index;
> > +         {
> > +           if (entry->isa_level > (1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT))
>
> Maybe wrap this on a macro at dl-cache.h? It already does it for
> DL_CACHE_HWCAP_ISA_LEVEL_MASK.
> > +             abort ();
>
> Maybe use 'error (...)' to print a proper error message?

I changed it to

+  if (entry->isa_level > DL_CACHE_HWCAP_ISA_LEVEL_MASK)
+    error (EXIT_FAILURE, 0, _("%s: ISA level is too high (%d > %d)"),
+          entry->path->string, entry->isa_level,
+          DL_CACHE_HWCAP_ISA_LEVEL_MASK);

since DL_CACHE_HWCAP_ISA_LEVEL_MASK is the maximum ISA
level.

> > +           file_entries_new->libs[idx_new].hwcap
> > +             = (DL_CACHE_HWCAP_EXTENSION
> > +                | (((uint64_t) entry->isa_level) << 32)
> > +                | entry->hwcaps->section_index);
> > +         }
>
> Would be better to wrap this on a inline function at dl-cache.h?
>
>  static inline unsigned int dl_cache_hwcap_isa_level (struct file_entry_new *entry)
>  {
>    return DL_CACHE_HWCAP_EXTENSION
>           | ((uint64_t) entry->isa_level << 32)
>           | entry->hwcaps->sections_index;
>  }

This function takes "struct cache_entry *entry" which is private to cache.c
I added compute_hwcap_value to cache.c instead.

> >         file_entries_new->libs[idx_new].key
> >           = str_offset + entry->lib->offset;
> >         file_entries_new->libs[idx_new].value
> > @@ -776,7 +783,8 @@ save_cache (const char *cache_name)
> >  /* Add one library to the cache.  */
> >  void
> >  add_to_cache (const char *path, const char *filename, const char *soname,
> > -           int flags, unsigned int osversion, uint64_t hwcap,
> > +           int flags, unsigned int osversion,
> > +           unsigned int isa_level, uint64_t hwcap,
> >             struct glibc_hwcaps_subdirectory *hwcaps)
> >  {
> >    struct cache_entry *new_entry = xmalloc (sizeof (*new_entry));
> > @@ -794,6 +802,7 @@ add_to_cache (const char *path, const char *filename, const char *soname,
> >    new_entry->path = path_interned;
> >    new_entry->flags = flags;
> >    new_entry->osversion = osversion;
> > +  new_entry->isa_level = isa_level;
> >    new_entry->hwcap = hwcap;
> >    new_entry->hwcaps = hwcaps;
> >    new_entry->bits_hwcap = 0;
>
> Ok.
>
> > @@ -850,6 +859,7 @@ struct aux_cache_entry
> >    struct aux_cache_entry_id id;
> >    int flags;
> >    unsigned int osversion;
> > +  unsigned int isa_level;
> >    int used;
> >    char *soname;
> >    struct aux_cache_entry *next;
> > @@ -863,7 +873,7 @@ struct aux_cache_file_entry
> >    int32_t flags;             /* This is 1 for an ELF library.  */
> >    uint32_t soname;           /* String table indice.  */
> >    uint32_t osversion;                /* Required OS version.  */
> > -  int32_t pad;
> > +  uint32_t isa_level;                /* Required ISA level.   */
> >  };
> >
>
> I think it would be good to have a _Static_assert with the
> expected aux_cache_entry size.

What would that be?  aux_cache_entry_id size is increased
by 4 bytes with my patch.

> >  /* ldconfig maintains an auxiliary cache file that allows
> > @@ -914,7 +924,8 @@ init_aux_cache (void)
> >
> >  int
> >  search_aux_cache (struct stat64 *stat_buf, int *flags,
> > -               unsigned int *osversion, char **soname)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname)
> >  {
> >    struct aux_cache_entry_id id;
> >    id.ino = (uint64_t) stat_buf->st_ino;
> > @@ -932,6 +943,7 @@ search_aux_cache (struct stat64 *stat_buf, int *flags,
> >        {
> >       *flags = entry->flags;
> >       *osversion = entry->osversion;
> > +     *isa_level = entry->isa_level;
> >       if (entry->soname != NULL)
> >         *soname = xstrdup (entry->soname);
> >       else
>
> Ok.
>
> > @@ -945,7 +957,8 @@ search_aux_cache (struct stat64 *stat_buf, int *flags,
> >
> >  static void
> >  insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
> > -                  unsigned int osversion, const char *soname, int used)
> > +                  unsigned int osversion, unsigned int isa_level,
> > +                  const char *soname, int used)
> >  {
> >    size_t hash = aux_cache_entry_id_hash (id) % aux_hash_size;
> >    struct aux_cache_entry *entry;
> > @@ -961,6 +974,7 @@ insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
> >    entry->id = *id;
> >    entry->flags = flags;
> >    entry->osversion = osversion;
> > +  entry->isa_level = isa_level;
> >    entry->used = used;
> >    if (soname != NULL)
> >      entry->soname = memcpy ((char *) (entry + 1), soname, len);
>
> Ok.
>
> > @@ -972,14 +986,15 @@ insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
> >
> >  void
> >  add_to_aux_cache (struct stat64 *stat_buf, int flags,
> > -               unsigned int osversion, const char *soname)
> > +               unsigned int osversion, unsigned int isa_level,
> > +               const char *soname)
> >  {
> >    struct aux_cache_entry_id id;
> >    id.ino = (uint64_t) stat_buf->st_ino;
> >    id.ctime = (uint64_t) stat_buf->st_ctime;
> >    id.size = (uint64_t) stat_buf->st_size;
> >    id.dev = (uint64_t) stat_buf->st_dev;
> > -  insert_to_aux_cache (&id, flags, osversion, soname, 1);
> > +  insert_to_aux_cache (&id, flags, osversion, isa_level, soname, 1);
> >  }
> >
> >  /* Load auxiliary cache to search for unchanged entries.   */
> > @@ -1025,6 +1040,7 @@ load_aux_cache (const char *aux_cache_name)
> >      insert_to_aux_cache (&aux_cache->libs[i].id,
> >                        aux_cache->libs[i].flags,
> >                        aux_cache->libs[i].osversion,
> > +                      aux_cache->libs[i].isa_level,
> >                        aux_cache->libs[i].soname == 0
> >                        ? NULL : aux_cache_data + aux_cache->libs[i].soname,
> >                        0);
> > @@ -1093,7 +1109,7 @@ save_aux_cache (const char *aux_cache_name)
> >             str_offset += len;
> >           }
> >         file_entries->libs[idx].osversion = entry->osversion;
> > -       file_entries->libs[idx++].pad = 0;
> > +       file_entries->libs[idx++].isa_level = entry->isa_level;
> >       }
> >
> >    /* Write out auxiliary cache file.  */
>
> Ok.
>
> > diff --git a/elf/dl-cache.c b/elf/dl-cache.c
> > index 97093bb700..edeff7ccc1 100644
> > --- a/elf/dl-cache.c
> > +++ b/elf/dl-cache.c
> > @@ -25,6 +25,7 @@
> >  #include <stdint.h>
> >  #include <_itoa.h>
> >  #include <dl-hwcaps.h>
> > +#include <dl-isa-level.h>
> >
> >  #ifndef _DL_PLATFORMS_COUNT
> >  # define _DL_PLATFORMS_COUNT 0
> > @@ -284,6 +285,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
> >
> >  #ifdef SHARED
> >                         named_hwcap = dl_cache_hwcap_extension (libnew);
> > +                       if (named_hwcap
> > +                           && !dl_cache_hwcap_isa_level_compatible (libnew))
> > +                         continue;
> >  #endif
> >
> >                         /* The entries with named/extension hwcaps
>
> Ok, so it skips non compatible ISA shared libraries.
>
> > diff --git a/elf/ldconfig.c b/elf/ldconfig.c
> > index 10927a8c7f..9dceac38aa 100644
> > --- a/elf/ldconfig.c
> > +++ b/elf/ldconfig.c
> > @@ -655,6 +655,7 @@ manual_link (char *library)
> >    struct stat64 stat_buf;
> >    int flag;
> >    unsigned int osversion;
> > +  unsigned int isa_level;
> >
> >    /* Prepare arguments for create_links call.  Split library name in
> >       directory and filename first.  Since path is allocated, we've got
> > @@ -721,7 +722,7 @@ manual_link (char *library)
> >      }
> >
> >    if (process_file (real_library, library, libname, &flag, &osversion,
> > -                 &soname, 0, &stat_buf))
> > +                 &isa_level, &soname, 0, &stat_buf))
> >      {
> >        error (0, 0, _("No link created since soname could not be found for %s"),
> >            library);
> > @@ -768,6 +769,7 @@ struct dlib_entry
> >    int flag;
> >    int is_link;
> >    unsigned int osversion;
> > +  unsigned int isa_level;
> >    struct dlib_entry *next;
> >  };
> >
>
> Ok.
>
> > @@ -980,17 +982,21 @@ search_dir (const struct dir_entry *entry)
> >        library already and it's not changed.  */
> >        char *soname;
> >        unsigned int osversion;
> > -      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &soname))
> > +      unsigned int isa_level;
> > +      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &isa_level,
> > +                          &soname))
> >       {
> >         if (process_file (real_name, file_name, direntry->d_name, &flag,
> > -                         &osversion, &soname, is_link, &lstat_buf))
> > +                         &osversion, &isa_level, &soname, is_link,
> > +                         &lstat_buf))
> >           {
> >             if (real_name != real_file_name)
> >               free (real_name);
> >             continue;
> >           }
> >         else if (opt_build_cache)
> > -         add_to_aux_cache (&lstat_buf, flag, osversion, soname);
> > +         add_to_aux_cache (&lstat_buf, flag, osversion, isa_level,
> > +                           soname);
> >       }
> >
> >        if (soname == NULL)
>
> Ok.
>
> > @@ -1096,6 +1102,7 @@ search_dir (const struct dir_entry *entry)
> >                 dlib_ptr->name = xstrdup (direntry->d_name);
> >                 dlib_ptr->is_link = is_link;
> >                 dlib_ptr->osversion = osversion;
> > +               dlib_ptr->isa_level = isa_level;
> >               }
> >             /* Don't add this library, abort loop.  */
> >             /* Also free soname, since it's dynamically allocated.  */
> > @@ -1112,6 +1119,7 @@ search_dir (const struct dir_entry *entry)
> >         dlib_ptr->flag = flag;
> >         dlib_ptr->is_link = is_link;
> >         dlib_ptr->osversion = osversion;
> > +       dlib_ptr->isa_level = isa_level;
> >         /* Add at head of list.  */
> >         dlib_ptr->next = dlibs;
> >         dlibs = dlib_ptr;
> > @@ -1149,7 +1157,7 @@ search_dir (const struct dir_entry *entry)
> >        if (opt_build_cache)
> >       add_to_cache (entry->path, filename, dlib_ptr->soname,
> >                     dlib_ptr->flag, dlib_ptr->osversion,
> > -                   hwcap, entry->hwcaps);
> > +                   dlib_ptr->isa_level, hwcap, entry->hwcaps);
> >      }
> >
> >    /* Free all resources.  */
>
> Ok.
>
> > diff --git a/elf/readelflib.c b/elf/readelflib.c
> > index 5905f6d344..abb1ac61fa 100644
> > --- a/elf/readelflib.c
> > +++ b/elf/readelflib.c
> > @@ -17,6 +17,8 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > +#include <read-prop.h>
> > +
> >  /* This code is a heavily simplified version of the readelf program
> >     that's part of the current binutils development version.  For architectures
> >     which need to handle both 32bit and 64bit ELF libraries,  this file is
> > @@ -40,8 +42,8 @@ do                                                          \
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    int i;
> >    unsigned int j;
> > @@ -86,6 +88,9 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >       libc5/libc6.  */
> >    *flag = FLAG_ELF;
> >
> > +  /* The default ISA level is 0.  */
> > +  *isa_level = 0;
> > +
> >    dynamic_addr = 0;
> >    dynamic_size = 0;
> >    program_interpreter = NULL;
> > @@ -164,6 +169,78 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >           }
> >         break;
> >
> > +     case PT_GNU_PROPERTY:
> > +       /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes
> > +          in 32-bit objects and to 8 bytes in 64-bit objects.  Skip
> > +          notes with incorrect alignment.  */
> > +       if (segment->p_align == (__ELF_NATIVE_CLASS / 8))
> > +         {
> > +           const ElfW(Nhdr) *note = (const void *) (file_contents
> > +                                                    + segment->p_offset);
> > +           const ElfW(Addr) size = segment->p_filesz;
> > +           const ElfW(Addr) align = segment->p_align;
> > +
> > +           const ElfW(Addr) start = (ElfW(Addr)) (uintptr_t) note;
> > +           unsigned int last_type = 0;
> > +
> > +           while ((ElfW(Addr)) (uintptr_t) (note + 1) - start < size)
> > +             {
> > +               /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
> > +               if (note->n_namesz == 4
> > +                   && note->n_type == NT_GNU_PROPERTY_TYPE_0
> > +                   && memcmp (note + 1, "GNU", 4) == 0)
> > +                 {
> > +                   /* Check for invalid property.  */
> > +                   if (note->n_descsz < 8
> > +                       || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
> > +                     goto done;
> > +
> > +                   /* Start and end of property array.  */
> > +                   unsigned char *ptr = (unsigned char *) (note + 1) + 4;
> > +                   unsigned char *ptr_end = ptr + note->n_descsz;
> > +
> > +                   do
> > +                     {
> > +                       unsigned int type = *(unsigned int *) ptr;
> > +                       unsigned int datasz = *(unsigned int *) (ptr + 4);
> > +
> > +                       /* Property type must be in ascending order.  */
> > +                       if (type < last_type)
> > +                         goto done;
> > +
> > +                       ptr += 8;
> > +                       if ((ptr + datasz) > ptr_end)
> > +                         goto done;
> > +
> > +                       last_type = type;
> > +
> > +                       /* Target specific property processing.
> > +                          Return value:
> > +                            false: Continue processing the properties.
> > +                            true : Stop processing the properties.
> > +                        */
> > +                       if (read_gnu_property (isa_level, type,
> > +                                              datasz, ptr))
> > +                         goto done;
> > +
> > +                       /* Check the next property item.  */
> > +                       ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
> > +                     }
> > +                   while ((ptr_end - ptr) >= 8);
> > +
> > +                   /* Only handle one NT_GNU_PROPERTY_TYPE_0.  */
> > +                   goto done;
> > +                 }
> > +
> > +               note = ((const void *) note
> > +                       + ELF_NOTE_NEXT_OFFSET (note->n_namesz,
> > +                                               note->n_descsz,
> > +                                               align));
> > +             }
> > +         }
> > +done:
> > +       break;
> > +
> >       default:
> >         break;
> >       }
>
> Ok, although this is quite similar to the _dl_process_pt_gnu_property
> (maybe a future work to try refactor both to use a common code).

That is a future possibility.

> > diff --git a/elf/readlib.c b/elf/readlib.c
> > index 994a4426a1..def0eafbeb 100644
> > --- a/elf/readlib.c
> > +++ b/elf/readlib.c
> > @@ -75,7 +75,8 @@ is_gdb_python_file (const char *name)
> >  int
> >  process_file (const char *real_file_name, const char *file_name,
> >             const char *lib, int *flag, unsigned int *osversion,
> > -           char **soname, int is_link, struct stat64 *stat_buf)
> > +           unsigned int *isa_level, char **soname, int is_link,
> > +           struct stat64 *stat_buf)
> >  {
> >    FILE *file;
> >    struct stat64 statbuf;
> > @@ -173,8 +174,8 @@ process_file (const char *real_file_name, const char *file_name,
> >    /* Libraries have to be shared object files.  */
> >    else if (elf_header->e_type != ET_DYN)
> >      ret = 1;
> > -  else if (process_elf_file (file_name, lib, flag, osversion, soname,
> > -                          file_contents, statbuf.st_size))
> > +  else if (process_elf_file (file_name, lib, flag, osversion, isa_level,
> > +                          soname, file_contents, statbuf.st_size))
> >      ret = 1;
> >
> >   done:
>
> Ok.
>
> > diff --git a/elf/tst-glibc-hwcaps-2-cache.c b/elf/tst-glibc-hwcaps-2-cache.c
> > new file mode 100644
> > index 0000000000..2c30a2c911
> > --- /dev/null
> > +++ b/elf/tst-glibc-hwcaps-2-cache.c
> > @@ -0,0 +1,45 @@
> > +/* Wrapper to invoke tst-glibc-hwcaps-2 in a container to test ldconfig.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +/* This program is just a wrapper that runs ldconfig followed by
> > +   tst-glibc-hwcaps-2.  The actual test is provided via an
> > +   implementation in a sysdeps subdirectory.  */
> > +
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <support/support.h>
> > +#include <unistd.h>
> > +
> > +int
> > +main (int argc, char **argv)
> > +{
> > +  /* Run ldconfig to populate the cache.  */
> > +  {
> > +    char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
> > +    if (system (command) != 0)
> > +      return 1;
> > +    free (command);
> > +  }
>
> Maybe use support_capture_subprogram here?
>
>   char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
>   struct support_capture_subprocess result =
>     support_capture_subprogram (command,  &((char *) { NULL }));
>   support_capture_subprocess_check (&result, "ldconfig", 0, sc_allow_none);
>   free (command);

Fixed.

> > +
> > +  /* Reuse tst-glibc-hwcaps.  Since this code is running in a
> > +     container, we can launch it directly.  */
> > +  char *path = xasprintf ("%s/elf/tst-glibc-hwcaps-2", support_objdir_root);
> > +  execv (path, argv);
> > +  printf ("error: execv of %s failed: %m\n", path);
> > +  return 1;
> > +}
>
> Ok.
>
> > diff --git a/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
> > new file mode 100644
> > index 0000000000..e1e74dbda2
> > --- /dev/null
> > +++ b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
> > @@ -0,0 +1,2 @@
> > +# This file was created to suppress a warning from ldconfig:
> > +# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
> > diff --git a/elf/tst-glibc-hwcaps-2-cache.root/postclean.req b/elf/tst-glibc-hwcaps-2-cache.root/postclean.req
> > new file mode 100644
> > index 0000000000..e69de29bb2
>
> Ok.
>
> > diff --git a/elf/tst-glibc-hwcaps-2-cache.script b/elf/tst-glibc-hwcaps-2-cache.script
> > new file mode 100644
> > index 0000000000..29ccfc3b49
> > --- /dev/null
> > +++ b/elf/tst-glibc-hwcaps-2-cache.script
> > @@ -0,0 +1,6 @@
> > +# test-container does not support scripts in sysdeps directories, so
> > +# collect everything in one file.
> > +
> > +mkdirp 0770 $L/glibc-hwcaps/x86-64-v2
>
> Ok.
>
> > +cp $B/elf/libx86-64-isa-level-1.so $L/libx86-64-isa-level.so
> > +cp $B/elf/libx86-64-isa-level-4.so $L/glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so
> > diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h
> > index 72a66b45ee..1138228e5c 100644
> > --- a/sysdeps/generic/dl-cache.h
> > +++ b/sysdeps/generic/dl-cache.h
> > @@ -106,14 +106,23 @@ struct file_entry_new
> >     entries.  */
> >  #define DL_CACHE_HWCAP_EXTENSION (1ULL << 62)
> >
> > +/* The number of the ISA level bits in the upper 32 bits of the hwcap
> > +   field.  */
> > +#define DL_CACHE_HWCAP_ISA_LEVEL_COUNT 10
> > +
> > +/* The mask of the ISA level bits in the hwcap field.  */
> > +#define DL_CACHE_HWCAP_ISA_LEVEL_MASK \
> > +  ((1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT) -1)
> > +
>
> Space after '-'.

Fixed.

> >  /* Return true if the ENTRY->hwcap value indicates that
> >     DL_CACHE_HWCAP_EXTENSION is used.  */
> >  static inline bool
> >  dl_cache_hwcap_extension (struct file_entry_new *entry)
> >  {
> > -  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
> > -     is a different kind of extension.  */
> > -  return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
> > +  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits, except for the
> > +     ISA level bits, as well, this is a different kind of extension.  */
> > +  return (((entry->hwcap >> 32) & ~DL_CACHE_HWCAP_ISA_LEVEL_MASK)
> > +       == (DL_CACHE_HWCAP_EXTENSION >> 32));
> >  }
> >
> >  /* See flags member of struct cache_file_new below.  */
>
> The comment sounds confusing.

I changed it to

  /* This is an hwcap extension if only the DL_CACHE_HWCAP_EXTENSION bit
     is set, ignoring the lower 32 bits as well as the ISA level bits in
     the upper 32 bits.  */

> > diff --git a/sysdeps/generic/dl-isa-level.h b/sysdeps/generic/dl-isa-level.h
> > new file mode 100644
> > index 0000000000..77735775b9
> > --- /dev/null
> > +++ b/sysdeps/generic/dl-isa-level.h
> > @@ -0,0 +1,26 @@
> > +/* Support for reading ISA level in /etc/ld.so.cache files written by
> > +   Linux ldconfig.  Generic version.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
>
> s/2020/2021

Fixed.

> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +/* Return true if the ISA level in ENTRY is compatible with CPU.  */
> > +
>
> My understanding is for function comment there is no need to add an
> extra newline.

Fixed.

> > +static inline bool
> > +dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
> > +{
> > +  return true;
> > +}
>
> Ok.
>
> > diff --git a/sysdeps/generic/ldconfig.h b/sysdeps/generic/ldconfig.h
> > index 1ad1528890..a5ed350237 100644
> > --- a/sysdeps/generic/ldconfig.h
> > +++ b/sysdeps/generic/ldconfig.h
> > @@ -70,8 +70,9 @@ const char *glibc_hwcaps_subdirectory_name
> >    (const struct glibc_hwcaps_subdirectory *);
> >
> >  extern void add_to_cache (const char *path, const char *filename,
> > -                       const char *soname,
> > -                       int flags, unsigned int osversion, uint64_t hwcap,
> > +                       const char *soname, int flags,
> > +                       unsigned int osversion, unsigned int isa_level,
> > +                       uint64_t hwcap,
> >                         struct glibc_hwcaps_subdirectory *);
> >
> >  extern void init_aux_cache (void);
> > @@ -79,23 +80,28 @@ extern void init_aux_cache (void);
> >  extern void load_aux_cache (const char *aux_cache_name);
> >
> >  extern int search_aux_cache (struct stat64 *stat_buf, int *flags,
> > -                          unsigned int *osversion, char **soname);
> > +                          unsigned int *osversion,
> > +                          unsigned int *isa_level, char **soname);
> >
> >  extern void add_to_aux_cache (struct stat64 *stat_buf, int flags,
> > -                           unsigned int osversion, const char *soname);
> > +                           unsigned int osversion,
> > +                           unsigned int isa_level, const char *soname);
> >
> >  extern void save_aux_cache (const char *aux_cache_name);
> >
> >  /* Declared in readlib.c.  */
> >  extern int process_file (const char *real_file_name, const char *file_name,
> > -                      const char *lib, int *flag, unsigned int *osversion,
> > -                      char **soname, int is_link, struct stat64 *stat_buf);
> > +                      const char *lib, int *flag,
> > +                      unsigned int *osversion, unsigned int *isa_level,
> > +                      char **soname, int is_link,
> > +                      struct stat64 *stat_buf);
> >
> >  extern char *implicit_soname (const char *lib, int flag);
> >
> >  /* Declared in readelflib.c.  */
> > -extern int process_elf_file (const char *file_name, const char *lib, int *flag,
> > -                          unsigned int *osversion, char **soname,
> > +extern int process_elf_file (const char *file_name, const char *lib,
> > +                          int *flag, unsigned int *osversion,
> > +                          unsigned int *isa_level, char **soname,
> >                            void *file_contents, size_t file_length);
> >
> >  /* Declared in chroot_canon.c.  */
>
>
> Ok.
>
> > diff --git a/sysdeps/generic/read-prop.h b/sysdeps/generic/read-prop.h
> > new file mode 100644
> > index 0000000000..091bd2f6c1
> > --- /dev/null
> > +++ b/sysdeps/generic/read-prop.h
>
> Maybe elf-read-prop.h to add more information on exactly this
> file intends to?

Renamed to elf-read-prop.h.

> > @@ -0,0 +1,35 @@
> > +/* Support for GNU properties in ldconfig.  Generic version.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#ifndef _READ_PROP_H
> > +#define _READ_PROP_H
> > +
> > +/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
> > +   Return value:
> > +     false: Continue processing the properties.
> > +     true : Stop processing the properties.
> > + */
> > +
> > +static inline bool __attribute__ ((always_inline))
> > +read_gnu_property (unsigned int *isal_level, uint32_t type, uint32_t
> > +                datasz, void *data)
> > +{
> > +  return true;
> > +}
> > +
> > +#endif
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/arm/readelflib.c b/sysdeps/unix/sysv/linux/arm/readelflib.c
> > index 9d03fa6405..7f444add14 100644
> > --- a/sysdeps/unix/sysv/linux/arm/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/arm/readelflib.c
> > @@ -18,18 +18,20 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret;
> > @@ -38,8 +40,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >      {
> >        Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
> >
> > -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >
> >        if (!ret && EF_ARM_EABI_VERSION (elf32_header->e_flags) == EF_ARM_EABI_VER5)
> >       {
> > @@ -57,8 +59,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >      }
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* AArch64 libraries are always libc.so.6+.  */
> >        if (!ret)
> >       *flag = FLAG_AARCH64_LIB64|FLAG_ELF_LIBC6;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/ia64/readelflib.c b/sysdeps/unix/sysv/linux/ia64/readelflib.c
> > index d24a934351..19d37b438e 100644
> > --- a/sysdeps/unix/sysv/linux/ia64/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/ia64/readelflib.c
> > @@ -16,29 +16,31 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname,
> > -               void *file_contents, size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret;
> >
> >    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> > -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                            file_contents, file_length);
> > +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                            soname, file_contents, file_length);
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* Intel 64bit libraries are always libc.so.6+.  */
> >        if (!ret)
> >       *flag = FLAG_IA64_LIB64|FLAG_ELF_LIBC6;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/mips/readelflib.c b/sysdeps/unix/sysv/linux/mips/readelflib.c
> > index 8363b8afcc..a3399961c9 100644
> > --- a/sysdeps/unix/sysv/linux/mips/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/mips/readelflib.c
> > @@ -20,18 +20,20 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    union
> >      {
> > @@ -45,8 +47,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >    elf_header.eh = file_contents;
> >    if (elf_header.eh->e_ident [EI_CLASS] == ELFCLASS32)
> >      {
> > -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        if (!ret)
> >       {
> >         Elf32_Word flags = elf_header.eh32->e_flags;
> > @@ -62,8 +64,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >      }
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* n64 libraries are always libc.so.6+.  */
> >        if (!ret)
> >       {
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/powerpc/readelflib.c b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> > index eb20680418..ce01658fb3 100644
> > --- a/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> > @@ -17,29 +17,31 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret;
> >
> >    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> > -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                            file_contents, file_length);
> > +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                            soname, file_contents, file_length);
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* PowerPC 64bit libraries are always libc.so.6+.  */
> >        if (!ret)
> >       *flag = FLAG_POWERPC_LIB64|FLAG_ELF_LIBC6;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/riscv/readelflib.c b/sysdeps/unix/sysv/linux/riscv/readelflib.c
> > index 1e70735cc0..98ae3c0b2b 100644
> > --- a/sysdeps/unix/sysv/linux/riscv/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/riscv/readelflib.c
> > @@ -17,11 +17,13 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* The ELF flags supported by our current glibc port:
> > @@ -38,8 +40,8 @@ int process_elf64_file (const char *file_name, const char *lib, int *flag,
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
> > @@ -52,14 +54,14 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
> >
> >    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> >      {
> > -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        flags = elf32_header->e_flags;
> >      }
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        flags = elf64_header->e_flags;
> >      }
> >
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/s390/readelflib.c b/sysdeps/unix/sysv/linux/s390/readelflib.c
> > index 1718efc9f9..6d19e351ba 100644
> > --- a/sysdeps/unix/sysv/linux/s390/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/s390/readelflib.c
> > @@ -16,29 +16,31 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret;
> >
> >    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> > -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                            file_contents, file_length);
> > +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                            soname, file_contents, file_length);
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* S/390 64bit libraries are always libc.so.6+.  */
> >        if (!ret)
> >       *flag = FLAG_S390_LIB64|FLAG_ELF_LIBC6;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/sparc/readelflib.c b/sysdeps/unix/sysv/linux/sparc/readelflib.c
> > index e027a11a37..3768003925 100644
> > --- a/sysdeps/unix/sysv/linux/sparc/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/sparc/readelflib.c
> > @@ -18,29 +18,31 @@
> >     <https://www.gnu.org/licenses/>.  */
> >
> >
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret;
> >
> >    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> > -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                            file_contents, file_length);
> > +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                            soname, file_contents, file_length);
> >    else
> >      {
> > -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                             file_contents, file_length);
> > +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                             soname, file_contents, file_length);
> >        /* Sparc 64bit libraries are always libc.so.6+.  */
> >        if (!ret)
> >       *flag = FLAG_SPARC_LIB64|FLAG_ELF_LIBC6;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/x86/read-prop.h b/sysdeps/unix/sysv/linux/x86/read-prop.h
> > new file mode 100644
> > index 0000000000..ac37fbc449
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/x86/read-prop.h
> > @@ -0,0 +1,61 @@
> > +/* Support for GNU properties in ldconfig.  x86 version.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
>
> s/2020/2021.

Fixed,

> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#ifndef _READ_PROP_H
> > +#define _READ_PROP_H
> > +
> > +#include <dl-cache.h>
> > +
> > +/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
> > +   Return value:
> > +     false: Continue processing the properties.
> > +     true : Stop processing the properties.
> > + */
> > +
> > +static inline bool __attribute__ ((always_inline))
> > +read_gnu_property (unsigned int *isal_level, uint32_t type,
> > +                uint32_t datasz, void *data)
> > +{
> > +  /* Property type must be in ascending order.  */
> > +  if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
> > +    return true;
> > +
> > +  if (type == GNU_PROPERTY_X86_ISA_1_NEEDED)
> > +    {
> > +      if (datasz == 4)
> > +     {
> > +       /* The size of GNU_PROPERTY_X86_ISA_1_NEEDED must be 4 bytes.
> > +          There is no point to continue if this type is ill-formed.  */
> > +       unsigned int isa_1_needed = *(unsigned int *) data;
> > +       _Static_assert (((sizeof (isa_1_needed) * 8)
> > +                        <= (1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT)),
> > +                       "DL_CACHE_HWCAP_ISA_LEVEL_COUNT is too small");
> > +       if (isa_1_needed)
>
> Implicit check.

Fixed.

> > +         {
> > +           unsigned int level;
> > +           asm ("bsr %1, %0" : "=r" (level) : "g" (isa_1_needed));
> > +           *isal_level = level;
> > +         }
> > +     }
> > +      return true;
> > +    }
> > +
> > +  return false;
> > +}
> > +
> > +#endif
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/x86/readelflib.c b/sysdeps/unix/sysv/linux/x86/readelflib.c
> > index 3e83419f5b..716629bf10 100644
> > --- a/sysdeps/unix/sysv/linux/x86/readelflib.c
> > +++ b/sysdeps/unix/sysv/linux/x86/readelflib.c
> > @@ -17,19 +17,20 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -
> > -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf32_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> > -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> > -                     unsigned int *osversion, char **soname,
> > +int process_elf64_file (const char *file_name, const char *lib,
> > +                     int *flag, unsigned int *osversion,
> > +                     unsigned int *isa_level, char **soname,
> >                       void *file_contents, size_t file_length);
> >
> >  /* Returns 0 if everything is ok, != 0 in case of error.  */
> >  int
> >  process_elf_file (const char *file_name, const char *lib, int *flag,
> > -               unsigned int *osversion, char **soname, void *file_contents,
> > -               size_t file_length)
> > +               unsigned int *osversion, unsigned int *isa_level,
> > +               char **soname, void *file_contents, size_t file_length)
> >  {
> >    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
> >    int ret, file_flag = 0;
> > @@ -68,11 +69,11 @@ failed:
> >      }
> >
> >    if (elf_header->e_ident[EI_CLASS] == ELFCLASS32)
> > -    ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> > -                           file_contents, file_length);
> > +    ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> > +                           soname, file_contents, file_length);
> >    else
> > -    ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> > -                           file_contents, file_length);
> > +    ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> > +                           soname, file_contents, file_length);
> >
> >    if (!ret && file_flag)
> >      *flag = file_flag;
>
> Ok.
>
> > diff --git a/sysdeps/unix/sysv/linux/x86_64/Makefile b/sysdeps/unix/sysv/linux/x86_64/Makefile
> > index 9b82155393..9a7b3cd8e5 100644
> > --- a/sysdeps/unix/sysv/linux/x86_64/Makefile
> > +++ b/sysdeps/unix/sysv/linux/x86_64/Makefile
> > @@ -13,3 +13,34 @@ endif
> >  ifeq ($(subdir),misc)
> >  gen-as-const-headers += sigaltstack-offsets.sym
> >  endif
> > +
> > +ifeq ($(subdir),elf)
> > +ifeq (yesyes,$(enable-x86-isa-level)$(config-cflags-skylake-avx512))
>
> As for first patch, I think we should extend the test coverage to check not
> only for config-cflags-skylake-avx512.  It means to build at least one
> shared object with different ISA levels and run the ldconfig and check the
> output against the system supported ISA level.

I removed $(config-cflags-skylake-avx512) and added more tests.

> > +tests += tst-glibc-hwcaps-2
> > +ifeq (no,$(build-hardcoded-path-in-tests))
> > +# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
> > +# interferes with its test objectives.
> > +tests-container += tst-glibc-hwcaps-2-cache
> > +endif
> > +modules-names += libx86-64-isa-level-1 libx86-64-isa-level-4
> > +
> > +$(objpfx)tst-glibc-hwcaps-2: $(objpfx)libx86-64-isa-level.so
> > +
> > +$(objpfx)tst-glibc-hwcaps-2.out: \
> > +  $(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so
> > +$(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so: \
> > +  $(objpfx)libx86-64-isa-level-4.so
> > +     cp $< $@
> > +
> > +CFLAGS-libx86-64-isa-level-1.os += -march=x86-64
> > +CFLAGS-libx86-64-isa-level-4.os += -march=skylake-avx512
> > +
> > +# The test modules are parameterized by preprocessor macros.
> > +LDFLAGS-libx86-64-isa-level-1.so += -Wl,-soname,libx86-64-isa-level.so
> > +LDFLAGS-libx86-64-isa-level-4.so += -Wl,-soname,libx86-64-isa-level.so
> > +$(objpfx)libx86-64-isa-level%.os: $(..)/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> > +     $(compile-command.c) -DVALUE=$(lastword $(subst -, ,$*))
> > +$(objpfx)libx86-64-isa-level.so: $(objpfx)libx86-64-isa-level-1.so
> > +     cp $< $@
> > +endif
> > +endif # $(subdir) == elf
> > diff --git a/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
> > new file mode 100644
> > index 0000000000..8d6b17d658
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
> > @@ -0,0 +1,61 @@
> > +/* Check ISA level on shared object in glibc-hwcaps subdirectories.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include <stdlib.h>
> > +#include <stdio.h>
> > +#include <elf.h>
> > +#include <get-isa-level.h>
> > +#include <support/check.h>
> > +#include <support/test-driver.h>
> > +
> > +extern int dso_isa_level (void);
> > +
> > +static int
> > +do_test (void)
> > +{
> > +  const struct cpu_features *cpu_features
> > +    = __x86_get_cpu_features (COMMON_CPUID_INDEX_MAX);
> > +  unsigned int isa_level = get_isa_level (cpu_features);
> > +  int level = dso_isa_level ();
> > +  int ret;
> > +  switch (level)
> > +    {
> > +    case 1:
> > +      /* The default libx86-64-isa-level.so should be used.  */
> > +      printf ("The default shared library is used.\n");
> > +      if ((isa_level & GNU_PROPERTY_X86_ISA_1_V4) != 0)
> > +     ret = EXIT_FAILURE;
> > +      else
> > +     ret = EXIT_SUCCESS;
> > +      break;
> > +    case 4:
> > +      /* libx86-64-isa-level.so marked as x86-64 ISA level 4 needed in
> > +      x86-64-v2 should be ignored on lesser CPU.  */
> > +      printf ("x86-64 ISA level 4 shared library in x86-64-v2 is used.\n");
> > +      if ((isa_level & GNU_PROPERTY_X86_ISA_1_V4) != 0)
> > +     ret = EXIT_SUCCESS;
> > +      else
> > +     ret = EXIT_FAILURE;
> > +      break;
> > +    default:
> > +      abort ();
> > +    }
> > +  return ret;
> > +}
> > +
> > +#include <support/test-driver.c>
> > diff --git a/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> > new file mode 100644
> > index 0000000000..2813d627cc
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> > @@ -0,0 +1,4 @@
> > +#define INCLUDE_X86_ISA_LEVEL
> > +#define MARKER dso_isa_level
> > +#include <isa-level.c>
> > +#include <markermodMARKER-VALUE.c>
> > diff --git a/sysdeps/x86/dl-isa-level.h b/sysdeps/x86/dl-isa-level.h
> > new file mode 100644
> > index 0000000000..c6ed8fb9d2
> > --- /dev/null
> > +++ b/sysdeps/x86/dl-isa-level.h
> > @@ -0,0 +1,32 @@
> > +/* Support for reading ISA level in /etc/ld.so.cache files written by
> > +   Linux ldconfig.  x86 version.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include <sys/platform/x86.h>
> > +
> > +/* Return true if the ISA level in ENTRY is compatible with CPU.  */
> > +
> > +static inline bool
> > +dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
> > +{
> > +  const struct cpu_features *cpu_features = __get_cpu_features ();
> > +  unsigned int isa_level
> > +    = 1 << ((entry->hwcap >> 32) & DL_CACHE_HWCAP_ISA_LEVEL_MASK);
> > +
> > +  return (isa_level & cpu_features->isa_1) == isa_level;
> > +}
>
> Ok.

Here is the updated patch.  OK for master?

Thanks.

Comments

Adhemerval Zanella Jan. 13, 2021, 1:47 p.m. UTC | #1
On 12/01/2021 20:32, H.J. Lu wrote:
> On Tue, Jan 12, 2021 at 8:25 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 09/12/2020 00:27, H.J. Lu via Libc-alpha wrote:
>>> On Tue, Dec 8, 2020 at 7:31 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>> @@ -850,6 +859,7 @@ struct aux_cache_entry
>>>    struct aux_cache_entry_id id;
>>>    int flags;
>>>    unsigned int osversion;
>>> +  unsigned int isa_level;
>>>    int used;
>>>    char *soname;
>>>    struct aux_cache_entry *next;
>>> @@ -863,7 +873,7 @@ struct aux_cache_file_entry
>>>    int32_t flags;             /* This is 1 for an ELF library.  */
>>>    uint32_t soname;           /* String table indice.  */
>>>    uint32_t osversion;                /* Required OS version.  */
>>> -  int32_t pad;
>>> +  uint32_t isa_level;                /* Required ISA level.   */
>>>  };
>>>
>>
>> I think it would be good to have a _Static_assert with the
>> expected aux_cache_entry size.
> 
> What would that be?  aux_cache_entry_id size is increased
> by 4 bytes with my patch.

My understanding is aux_cache_entry_id keeps the same and you are using
an unused field on *aux_cache_file_entry* to add the isa_level.  Their
sizes should kept the same (since isa_level is the same size of the
previous pad).

But the _Static_assert might indeed unrequired, the load_aux_cache already
check if the aux_cache_file_entry does match the file size and uses an
empty auxiliary cache otherwise (init_aux_cache).

elf/cache.c

1008   if (aux_cache == MAP_FAILED
1009       || aux_cache_size < sizeof (struct aux_cache_file)
1010       || memcmp (aux_cache->magic, AUX_CACHEMAGIC, sizeof AUX_CACHEMAGIC - 1)
1011       || aux_cache_size != (sizeof (struct aux_cache_file)
1012                             + aux_cache->nlibs * sizeof (struct aux_cache_file_entry)
1013                             + aux_cache->len_strings))
1014     { 
1015       close (fd);
1016       init_aux_cache ();
1017       return;
1018     }


>>>  /* Return true if the ENTRY->hwcap value indicates that
>>>     DL_CACHE_HWCAP_EXTENSION is used.  */
>>>  static inline bool
>>>  dl_cache_hwcap_extension (struct file_entry_new *entry)
>>>  {
>>> -  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
>>> -     is a different kind of extension.  */
>>> -  return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
>>> +  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits, except for the
>>> +     ISA level bits, as well, this is a different kind of extension.  */
>>> +  return (((entry->hwcap >> 32) & ~DL_CACHE_HWCAP_ISA_LEVEL_MASK)
>>> +       == (DL_CACHE_HWCAP_EXTENSION >> 32));
>>>  }
>>>
>>>  /* See flags member of struct cache_file_new below.  */
>>
>> The comment sounds confusing.
> 
> I changed it to
> 
>   /* This is an hwcap extension if only the DL_CACHE_HWCAP_EXTENSION bit
>      is set, ignoring the lower 32 bits as well as the ISA level bits in
>      the upper 32 bits.  */

Thanks.

---
> From 40bacb7470f0c8d8eabd4d3b24057566d45ca5dd Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Sat, 5 Dec 2020 07:01:58 -0800
> Subject: [PATCH] ldconfig/x86: Store ISA level in cache and aux cache
> 
> Store ISA level in the portion of the unused upper 32 bits of the hwcaps
> field in cache and the unused pad field in aux cache.  ISA level is stored
> and checked only for shared objects in glibc-hwcaps subdirectories.  The
> shared objects in the default directories aren't checked since there are
> no fallbacks for these shared objects.
> 
> Tested on x86-64-v2, x86-64-v3 and x86-64-v4 machines with
> --disable-hardcoded-path-in-tests and --enable-hardcoded-path-in-tests.

LGTM, thanks.  

Please update the release page once you commit it.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/cache.c                                   | 39 +++++++--
>  elf/dl-cache.c                                |  4 +
>  elf/ldconfig.c                                | 18 ++--
>  elf/readelflib.c                              | 81 +++++++++++++++++-
>  elf/readlib.c                                 |  7 +-
>  elf/tst-glibc-hwcaps-2-cache.c                | 45 ++++++++++
>  .../etc/ld.so.conf                            |  2 +
>  .../postclean.req                             |  0
>  elf/tst-glibc-hwcaps-2-cache.script           |  8 ++
>  sysdeps/generic/dl-cache.h                    | 16 +++-
>  sysdeps/generic/dl-isa-level.h                | 25 ++++++
>  sysdeps/generic/elf-read-prop.h               | 34 ++++++++
>  sysdeps/generic/ldconfig.h                    | 22 +++--
>  sysdeps/unix/sysv/linux/arm/readelflib.c      | 22 ++---
>  sysdeps/unix/sysv/linux/ia64/readelflib.c     | 22 ++---
>  sysdeps/unix/sysv/linux/mips/readelflib.c     | 22 ++---
>  sysdeps/unix/sysv/linux/powerpc/readelflib.c  | 22 ++---
>  sysdeps/unix/sysv/linux/riscv/readelflib.c    | 22 ++---
>  sysdeps/unix/sysv/linux/s390/readelflib.c     | 22 ++---
>  sysdeps/unix/sysv/linux/sparc/readelflib.c    | 22 ++---
>  sysdeps/unix/sysv/linux/x86/elf-read-prop.h   | 60 +++++++++++++
>  sysdeps/unix/sysv/linux/x86/readelflib.c      | 23 ++---
>  sysdeps/unix/sysv/linux/x86_64/Makefile       | 51 +++++++++++
>  .../sysv/linux/x86_64/tst-glibc-hwcaps-2.c    | 84 +++++++++++++++++++
>  .../linux/x86_64/x86-64-isa-level-VALUE.c     |  4 +
>  sysdeps/x86/dl-isa-level.h                    | 31 +++++++
>  26 files changed, 598 insertions(+), 110 deletions(-)
>  create mode 100644 elf/tst-glibc-hwcaps-2-cache.c
>  create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
>  create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/postclean.req
>  create mode 100644 elf/tst-glibc-hwcaps-2-cache.script
>  create mode 100644 sysdeps/generic/dl-isa-level.h
>  create mode 100644 sysdeps/generic/elf-read-prop.h
>  create mode 100644 sysdeps/unix/sysv/linux/x86/elf-read-prop.h
>  create mode 100644 sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
>  create mode 100644 sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
>  create mode 100644 sysdeps/x86/dl-isa-level.h
> 
> diff --git a/elf/cache.c b/elf/cache.c
> index 11ce4ade8a..c01d302072 100644
> --- a/elf/cache.c
> +++ b/elf/cache.c
> @@ -146,6 +146,7 @@ struct cache_entry
>    struct stringtable_entry *path; /* Path to find library.  */
>    int flags;			/* Flags to indicate kind of library.  */
>    unsigned int osversion;	/* Required OS version.  */
> +  unsigned int isa_level;	/* Required ISA level.  */
>    uint64_t hwcap;		/* Important hardware capabilities.  */
>    int bits_hwcap;		/* Number of bits set in hwcap.  */
>  
> @@ -549,6 +550,19 @@ write_extensions (int fd, uint32_t str_offset,
>    free (ext);
>  }
>  
> +/* Compute the hwcap value from ENTRY.  */
> +static inline uint64_t
> +compute_hwcap_value (struct cache_entry *entry)
> +{
> +  if (entry->isa_level > DL_CACHE_HWCAP_ISA_LEVEL_MASK)
> +    error (EXIT_FAILURE, 0, _("%s: ISA level is too high (%d > %d)"),
> +	   entry->path->string, entry->isa_level,
> +	   DL_CACHE_HWCAP_ISA_LEVEL_MASK);
> +  return (DL_CACHE_HWCAP_EXTENSION
> +	  | (((uint64_t) entry->isa_level) << 32)
> +	  | entry->hwcaps->section_index);
> +}
> +
>  /* Save the contents of the cache.  */
>  void
>  save_cache (const char *cache_name)
> @@ -662,7 +676,7 @@ save_cache (const char *cache_name)
>  	    file_entries_new->libs[idx_new].hwcap = entry->hwcap;
>  	  else
>  	    file_entries_new->libs[idx_new].hwcap
> -	      = DL_CACHE_HWCAP_EXTENSION | entry->hwcaps->section_index;
> +	      = compute_hwcap_value (entry);
>  	  file_entries_new->libs[idx_new].key
>  	    = str_offset + entry->lib->offset;
>  	  file_entries_new->libs[idx_new].value

Ok.

> @@ -777,7 +791,8 @@ save_cache (const char *cache_name)
>  /* Add one library to the cache.  */
>  void
>  add_to_cache (const char *path, const char *filename, const char *soname,
> -	      int flags, unsigned int osversion, uint64_t hwcap,
> +	      int flags, unsigned int osversion,
> +	      unsigned int isa_level, uint64_t hwcap,
>  	      struct glibc_hwcaps_subdirectory *hwcaps)
>  {
>    struct cache_entry *new_entry = xmalloc (sizeof (*new_entry));
> @@ -795,6 +810,7 @@ add_to_cache (const char *path, const char *filename, const char *soname,
>    new_entry->path = path_interned;
>    new_entry->flags = flags;
>    new_entry->osversion = osversion;
> +  new_entry->isa_level = isa_level;
>    new_entry->hwcap = hwcap;
>    new_entry->hwcaps = hwcaps;
>    new_entry->bits_hwcap = 0;
> @@ -851,6 +867,7 @@ struct aux_cache_entry
>    struct aux_cache_entry_id id;
>    int flags;
>    unsigned int osversion;
> +  unsigned int isa_level;
>    int used;
>    char *soname;
>    struct aux_cache_entry *next;
> @@ -864,7 +881,7 @@ struct aux_cache_file_entry
>    int32_t flags;		/* This is 1 for an ELF library.  */
>    uint32_t soname;		/* String table indice.  */
>    uint32_t osversion;		/* Required OS version.	 */
> -  int32_t pad;
> +  uint32_t isa_level;		/* Required ISA level.	 */
>  };
>  
>  /* ldconfig maintains an auxiliary cache file that allows
> @@ -915,7 +932,8 @@ init_aux_cache (void)
>  
>  int
>  search_aux_cache (struct stat64 *stat_buf, int *flags,
> -		  unsigned int *osversion, char **soname)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname)
>  {
>    struct aux_cache_entry_id id;
>    id.ino = (uint64_t) stat_buf->st_ino;
> @@ -933,6 +951,7 @@ search_aux_cache (struct stat64 *stat_buf, int *flags,
>        {
>  	*flags = entry->flags;
>  	*osversion = entry->osversion;
> +	*isa_level = entry->isa_level;
>  	if (entry->soname != NULL)
>  	  *soname = xstrdup (entry->soname);
>  	else
> @@ -946,7 +965,8 @@ search_aux_cache (struct stat64 *stat_buf, int *flags,
>  
>  static void
>  insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
> -		     unsigned int osversion, const char *soname, int used)
> +		     unsigned int osversion, unsigned int isa_level,
> +		     const char *soname, int used)
>  {
>    size_t hash = aux_cache_entry_id_hash (id) % aux_hash_size;
>    struct aux_cache_entry *entry;
> @@ -962,6 +982,7 @@ insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
>    entry->id = *id;
>    entry->flags = flags;
>    entry->osversion = osversion;
> +  entry->isa_level = isa_level;
>    entry->used = used;
>    if (soname != NULL)
>      entry->soname = memcpy ((char *) (entry + 1), soname, len);
> @@ -973,14 +994,15 @@ insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
>  
>  void
>  add_to_aux_cache (struct stat64 *stat_buf, int flags,
> -		  unsigned int osversion, const char *soname)
> +		  unsigned int osversion, unsigned int isa_level,
> +		  const char *soname)
>  {
>    struct aux_cache_entry_id id;
>    id.ino = (uint64_t) stat_buf->st_ino;
>    id.ctime = (uint64_t) stat_buf->st_ctime;
>    id.size = (uint64_t) stat_buf->st_size;
>    id.dev = (uint64_t) stat_buf->st_dev;
> -  insert_to_aux_cache (&id, flags, osversion, soname, 1);
> +  insert_to_aux_cache (&id, flags, osversion, isa_level, soname, 1);
>  }
>  
>  /* Load auxiliary cache to search for unchanged entries.   */
> @@ -1026,6 +1048,7 @@ load_aux_cache (const char *aux_cache_name)
>      insert_to_aux_cache (&aux_cache->libs[i].id,
>  			 aux_cache->libs[i].flags,
>  			 aux_cache->libs[i].osversion,
> +			 aux_cache->libs[i].isa_level,
>  			 aux_cache->libs[i].soname == 0
>  			 ? NULL : aux_cache_data + aux_cache->libs[i].soname,
>  			 0);
> @@ -1094,7 +1117,7 @@ save_aux_cache (const char *aux_cache_name)
>  	      str_offset += len;
>  	    }
>  	  file_entries->libs[idx].osversion = entry->osversion;
> -	  file_entries->libs[idx++].pad = 0;
> +	  file_entries->libs[idx++].isa_level = entry->isa_level;
>  	}
>  
>    /* Write out auxiliary cache file.  */

Ok.

> diff --git a/elf/dl-cache.c b/elf/dl-cache.c
> index 935e3a60b4..32f3bef5ea 100644
> --- a/elf/dl-cache.c
> +++ b/elf/dl-cache.c
> @@ -25,6 +25,7 @@
>  #include <stdint.h>
>  #include <_itoa.h>
>  #include <dl-hwcaps.h>
> +#include <dl-isa-level.h>
>  
>  #ifndef _DL_PLATFORMS_COUNT
>  # define _DL_PLATFORMS_COUNT 0
> @@ -284,6 +285,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
>  
>  #ifdef SHARED
>  			  named_hwcap = dl_cache_hwcap_extension (libnew);
> +			  if (named_hwcap
> +			      && !dl_cache_hwcap_isa_level_compatible (libnew))
> +			    continue;
>  #endif
>  
>  			  /* The entries with named/extension hwcaps

Ok.

> diff --git a/elf/ldconfig.c b/elf/ldconfig.c
> index bbcf8f5c5c..28ed637a29 100644
> --- a/elf/ldconfig.c
> +++ b/elf/ldconfig.c
> @@ -655,6 +655,7 @@ manual_link (char *library)
>    struct stat64 stat_buf;
>    int flag;
>    unsigned int osversion;
> +  unsigned int isa_level;
>  
>    /* Prepare arguments for create_links call.  Split library name in
>       directory and filename first.  Since path is allocated, we've got
> @@ -721,7 +722,7 @@ manual_link (char *library)
>      }
>  
>    if (process_file (real_library, library, libname, &flag, &osversion,
> -		    &soname, 0, &stat_buf))
> +		    &isa_level, &soname, 0, &stat_buf))
>      {
>        error (0, 0, _("No link created since soname could not be found for %s"),
>  	     library);
> @@ -768,6 +769,7 @@ struct dlib_entry
>    int flag;
>    int is_link;
>    unsigned int osversion;
> +  unsigned int isa_level;
>    struct dlib_entry *next;
>  };
>  
> @@ -980,17 +982,21 @@ search_dir (const struct dir_entry *entry)
>  	 library already and it's not changed.  */
>        char *soname;
>        unsigned int osversion;
> -      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &soname))
> +      unsigned int isa_level;
> +      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &isa_level,
> +			     &soname))
>  	{
>  	  if (process_file (real_name, file_name, direntry->d_name, &flag,
> -			    &osversion, &soname, is_link, &lstat_buf))
> +			    &osversion, &isa_level, &soname, is_link,
> +			    &lstat_buf))
>  	    {
>  	      if (real_name != real_file_name)
>  		free (real_name);
>  	      continue;
>  	    }
>  	  else if (opt_build_cache)
> -	    add_to_aux_cache (&lstat_buf, flag, osversion, soname);
> +	    add_to_aux_cache (&lstat_buf, flag, osversion, isa_level,
> +			      soname);
>  	}
>  
>        if (soname == NULL)
> @@ -1096,6 +1102,7 @@ search_dir (const struct dir_entry *entry)
>  		  dlib_ptr->name = xstrdup (direntry->d_name);
>  		  dlib_ptr->is_link = is_link;
>  		  dlib_ptr->osversion = osversion;
> +		  dlib_ptr->isa_level = isa_level;
>  		}
>  	      /* Don't add this library, abort loop.  */
>  	      /* Also free soname, since it's dynamically allocated.  */
> @@ -1112,6 +1119,7 @@ search_dir (const struct dir_entry *entry)
>  	  dlib_ptr->flag = flag;
>  	  dlib_ptr->is_link = is_link;
>  	  dlib_ptr->osversion = osversion;
> +	  dlib_ptr->isa_level = isa_level;
>  	  /* Add at head of list.  */
>  	  dlib_ptr->next = dlibs;
>  	  dlibs = dlib_ptr;
> @@ -1149,7 +1157,7 @@ search_dir (const struct dir_entry *entry)
>        if (opt_build_cache)
>  	add_to_cache (entry->path, filename, dlib_ptr->soname,
>  		      dlib_ptr->flag, dlib_ptr->osversion,
> -		      hwcap, entry->hwcaps);
> +		      dlib_ptr->isa_level, hwcap, entry->hwcaps);
>      }
>  
>    /* Free all resources.  */

Ok.

> diff --git a/elf/readelflib.c b/elf/readelflib.c
> index cdea79d729..c09425a574 100644
> --- a/elf/readelflib.c
> +++ b/elf/readelflib.c
> @@ -17,6 +17,8 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> +#include <elf-read-prop.h>
> +
>  /* This code is a heavily simplified version of the readelf program
>     that's part of the current binutils development version.  For architectures
>     which need to handle both 32bit and 64bit ELF libraries,  this file is
> @@ -40,8 +42,8 @@ do								\
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    int i;
>    unsigned int j;
> @@ -86,6 +88,9 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>       libc5/libc6.  */
>    *flag = FLAG_ELF;
>  
> +  /* The default ISA level is 0.  */
> +  *isa_level = 0;
> +
>    dynamic_addr = 0;
>    dynamic_size = 0;
>    program_interpreter = NULL;
> @@ -164,6 +169,78 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>  	    }
>  	  break;
>  
> +	case PT_GNU_PROPERTY:
> +	  /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes
> +	     in 32-bit objects and to 8 bytes in 64-bit objects.  Skip
> +	     notes with incorrect alignment.  */
> +	  if (segment->p_align == (__ELF_NATIVE_CLASS / 8))
> +	    {
> +	      const ElfW(Nhdr) *note = (const void *) (file_contents
> +						       + segment->p_offset);
> +	      const ElfW(Addr) size = segment->p_filesz;
> +	      const ElfW(Addr) align = segment->p_align;
> +
> +	      const ElfW(Addr) start = (ElfW(Addr)) (uintptr_t) note;
> +	      unsigned int last_type = 0;
> +
> +	      while ((ElfW(Addr)) (uintptr_t) (note + 1) - start < size)
> +		{
> +		  /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
> +		  if (note->n_namesz == 4
> +		      && note->n_type == NT_GNU_PROPERTY_TYPE_0
> +		      && memcmp (note + 1, "GNU", 4) == 0)
> +		    {
> +		      /* Check for invalid property.  */
> +		      if (note->n_descsz < 8
> +			  || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
> +			goto done;
> +
> +		      /* Start and end of property array.  */
> +		      unsigned char *ptr = (unsigned char *) (note + 1) + 4;
> +		      unsigned char *ptr_end = ptr + note->n_descsz;
> +
> +		      do
> +			{
> +			  unsigned int type = *(unsigned int *) ptr;
> +			  unsigned int datasz = *(unsigned int *) (ptr + 4);
> +
> +			  /* Property type must be in ascending order.  */
> +			  if (type < last_type)
> +			    goto done;
> +
> +			  ptr += 8;
> +			  if ((ptr + datasz) > ptr_end)
> +			    goto done;
> +
> +			  last_type = type;
> +
> +			  /* Target specific property processing.
> +			     Return value:
> +			       false: Continue processing the properties.
> +			       true : Stop processing the properties.
> +			   */
> +			  if (read_gnu_property (isa_level, type,
> +						 datasz, ptr))
> +			    goto done;
> +
> +			  /* Check the next property item.  */
> +			  ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
> +			}
> +		      while ((ptr_end - ptr) >= 8);
> +
> +		      /* Only handle one NT_GNU_PROPERTY_TYPE_0.  */
> +		      goto done;
> +		    }
> +
> +		  note = ((const void *) note
> +			  + ELF_NOTE_NEXT_OFFSET (note->n_namesz,
> +						  note->n_descsz,
> +						  align));
> +		}
> +	    }
> +done:
> +	  break;
> +
>  	default:
>  	  break;
>  	}
> diff --git a/elf/readlib.c b/elf/readlib.c

Ok.

> index 3d52c9a980..7383c23249 100644
> --- a/elf/readlib.c
> +++ b/elf/readlib.c
> @@ -75,7 +75,8 @@ is_gdb_python_file (const char *name)
>  int
>  process_file (const char *real_file_name, const char *file_name,
>  	      const char *lib, int *flag, unsigned int *osversion,
> -	      char **soname, int is_link, struct stat64 *stat_buf)
> +	      unsigned int *isa_level, char **soname, int is_link,
> +	      struct stat64 *stat_buf)
>  {
>    FILE *file;
>    struct stat64 statbuf;
> @@ -173,8 +174,8 @@ process_file (const char *real_file_name, const char *file_name,
>    /* Libraries have to be shared object files.  */
>    else if (elf_header->e_type != ET_DYN)
>      ret = 1;
> -  else if (process_elf_file (file_name, lib, flag, osversion, soname,
> -			     file_contents, statbuf.st_size))
> +  else if (process_elf_file (file_name, lib, flag, osversion, isa_level,
> +			     soname, file_contents, statbuf.st_size))
>      ret = 1;
>  
>   done:

Ok.

> diff --git a/elf/tst-glibc-hwcaps-2-cache.c b/elf/tst-glibc-hwcaps-2-cache.c
> new file mode 100644
> index 0000000000..97d9835ddb
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-2-cache.c
> @@ -0,0 +1,45 @@
> +/* Wrapper to invoke tst-glibc-hwcaps-2 in a container to test ldconfig.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* This program is just a wrapper that runs ldconfig followed by
> +   tst-glibc-hwcaps-2.  The actual test is provided via an
> +   implementation in a sysdeps subdirectory.  */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <support/support.h>
> +#include <support/capture_subprocess.h>
> +
> +int
> +main (int argc, char **argv)
> +{
> +  /* Run ldconfig to populate the cache.  */
> +  char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
> +  struct support_capture_subprocess result =
> +    support_capture_subprogram (command,  &((char *) { NULL }));
> +  support_capture_subprocess_check (&result, "ldconfig", 0, sc_allow_none);
> +  free (command);
> +
> +  /* Reuse tst-glibc-hwcaps.  Since this code is running in a
> +     container, we can launch it directly.  */
> +  char *path = xasprintf ("%s/elf/tst-glibc-hwcaps-2", support_objdir_root);
> +  execv (path, argv);
> +  printf ("error: execv of %s failed: %m\n", path);
> +  return 1;
> +}

Ok.

> diff --git a/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
> new file mode 100644
> index 0000000000..e1e74dbda2
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
> @@ -0,0 +1,2 @@
> +# This file was created to suppress a warning from ldconfig:
> +# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
> diff --git a/elf/tst-glibc-hwcaps-2-cache.root/postclean.req b/elf/tst-glibc-hwcaps-2-cache.root/postclean.req
> new file mode 100644
> index 0000000000..e69de29bb2
> diff --git a/elf/tst-glibc-hwcaps-2-cache.script b/elf/tst-glibc-hwcaps-2-cache.script
> new file mode 100644
> index 0000000000..8e4e9896ee
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-2-cache.script
> @@ -0,0 +1,8 @@
> +# test-container does not support scripts in sysdeps directories, so
> +# collect everything in one file.
> +
> +mkdirp 0770 $L/glibc-hwcaps/x86-64-v2
> +mkdirp 0770 $L/glibc-hwcaps/x86-64-v3
> +cp $B/elf/libx86-64-isa-level-1.so $L/libx86-64-isa-level.so
> +cp $B/elf/libx86-64-isa-level-3.so $L/glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so
> +cp $B/elf/libx86-64-isa-level-4.so $L/glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so

Ok.

> diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h
> index c7eca70d0c..964d50a486 100644
> --- a/sysdeps/generic/dl-cache.h
> +++ b/sysdeps/generic/dl-cache.h
> @@ -106,14 +106,24 @@ struct file_entry_new
>     entries.  */
>  #define DL_CACHE_HWCAP_EXTENSION (1ULL << 62)
>  
> +/* The number of the ISA level bits in the upper 32 bits of the hwcap
> +   field.  */
> +#define DL_CACHE_HWCAP_ISA_LEVEL_COUNT 10
> +
> +/* The mask of the ISA level bits in the hwcap field.  */
> +#define DL_CACHE_HWCAP_ISA_LEVEL_MASK \
> +  ((1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT) -1)
> +
>  /* Return true if the ENTRY->hwcap value indicates that
>     DL_CACHE_HWCAP_EXTENSION is used.  */
>  static inline bool
>  dl_cache_hwcap_extension (struct file_entry_new *entry)
>  {
> -  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
> -     is a different kind of extension.  */
> -  return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
> +  /* This is an hwcap extension if only the DL_CACHE_HWCAP_EXTENSION bit
> +     is set, ignoring the lower 32 bits as well as the ISA level bits in
> +     the upper 32 bits.  */
> +  return (((entry->hwcap >> 32) & ~DL_CACHE_HWCAP_ISA_LEVEL_MASK)
> +	  == (DL_CACHE_HWCAP_EXTENSION >> 32));
>  }
>  
>  /* See flags member of struct cache_file_new below.  */

Ok.

> diff --git a/sysdeps/generic/dl-isa-level.h b/sysdeps/generic/dl-isa-level.h
> new file mode 100644
> index 0000000000..6fcd319c49
> --- /dev/null
> +++ b/sysdeps/generic/dl-isa-level.h
> @@ -0,0 +1,25 @@
> +/* Support for reading ISA level in /etc/ld.so.cache files written by
> +   Linux ldconfig.  Generic version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* Return true if the ISA level in ENTRY is compatible with CPU.  */
> +static inline bool
> +dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
> +{
> +  return true;
> +}

Ok.

> diff --git a/sysdeps/generic/elf-read-prop.h b/sysdeps/generic/elf-read-prop.h
> new file mode 100644
> index 0000000000..98c3d2acb5
> --- /dev/null
> +++ b/sysdeps/generic/elf-read-prop.h
> @@ -0,0 +1,34 @@
> +/* Support for GNU properties in ldconfig.  Generic version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifndef _ELF_READ_PROP_H
> +#define _ELF_READ_PROP_H
> +
> +/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
> +   Return value:
> +     false: Continue processing the properties.
> +     true : Stop processing the properties.
> + */
> +static inline bool __attribute__ ((always_inline))
> +read_gnu_property (unsigned int *isal_level, uint32_t type, uint32_t
> +		   datasz, void *data)
> +{
> +  return true;
> +}
> +
> +#endif

Ok.

> diff --git a/sysdeps/generic/ldconfig.h b/sysdeps/generic/ldconfig.h
> index eb070fd259..3ab757077d 100644
> --- a/sysdeps/generic/ldconfig.h
> +++ b/sysdeps/generic/ldconfig.h
> @@ -70,8 +70,9 @@ const char *glibc_hwcaps_subdirectory_name
>    (const struct glibc_hwcaps_subdirectory *);
>  
>  extern void add_to_cache (const char *path, const char *filename,
> -			  const char *soname,
> -			  int flags, unsigned int osversion, uint64_t hwcap,
> +			  const char *soname, int flags,
> +			  unsigned int osversion, unsigned int isa_level,
> +			  uint64_t hwcap,
>  			  struct glibc_hwcaps_subdirectory *);
>  
>  extern void init_aux_cache (void);
> @@ -79,23 +80,28 @@ extern void init_aux_cache (void);
>  extern void load_aux_cache (const char *aux_cache_name);
>  
>  extern int search_aux_cache (struct stat64 *stat_buf, int *flags,
> -			     unsigned int *osversion, char **soname);
> +			     unsigned int *osversion,
> +			     unsigned int *isa_level, char **soname);
>  
>  extern void add_to_aux_cache (struct stat64 *stat_buf, int flags,
> -			      unsigned int osversion, const char *soname);
> +			      unsigned int osversion,
> +			      unsigned int isa_level, const char *soname);
>  
>  extern void save_aux_cache (const char *aux_cache_name);
>  
>  /* Declared in readlib.c.  */
>  extern int process_file (const char *real_file_name, const char *file_name,
> -			 const char *lib, int *flag, unsigned int *osversion,
> -			 char **soname, int is_link, struct stat64 *stat_buf);
> +			 const char *lib, int *flag,
> +			 unsigned int *osversion, unsigned int *isa_level,
> +			 char **soname, int is_link,
> +			 struct stat64 *stat_buf);
>  
>  extern char *implicit_soname (const char *lib, int flag);
>  
>  /* Declared in readelflib.c.  */
> -extern int process_elf_file (const char *file_name, const char *lib, int *flag,
> -			     unsigned int *osversion, char **soname,
> +extern int process_elf_file (const char *file_name, const char *lib,
> +			     int *flag, unsigned int *osversion,
> +			     unsigned int *isa_level, char **soname,
>  			     void *file_contents, size_t file_length);
>  
>  /* Declared in chroot_canon.c.  */

Ok.

> diff --git a/sysdeps/unix/sysv/linux/arm/readelflib.c b/sysdeps/unix/sysv/linux/arm/readelflib.c
> index 2d3ecb1eef..ade2f49aeb 100644
> --- a/sysdeps/unix/sysv/linux/arm/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/arm/readelflib.c
> @@ -18,18 +18,20 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret;
> @@ -38,8 +40,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>      {
>        Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
>  
> -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>  
>        if (!ret && EF_ARM_EABI_VERSION (elf32_header->e_flags) == EF_ARM_EABI_VER5)
>  	{
> @@ -57,8 +59,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>      }
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* AArch64 libraries are always libc.so.6+.  */
>        if (!ret)
>  	*flag = FLAG_AARCH64_LIB64|FLAG_ELF_LIBC6;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/ia64/readelflib.c b/sysdeps/unix/sysv/linux/ia64/readelflib.c
> index 7fb3ace359..2aa32666aa 100644
> --- a/sysdeps/unix/sysv/linux/ia64/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/ia64/readelflib.c
> @@ -16,29 +16,31 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname,
> -		  void *file_contents, size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret;
>  
>    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> -			       file_contents, file_length);
> +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +			       soname, file_contents, file_length);
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* Intel 64bit libraries are always libc.so.6+.  */
>        if (!ret)
>  	*flag = FLAG_IA64_LIB64|FLAG_ELF_LIBC6;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/mips/readelflib.c b/sysdeps/unix/sysv/linux/mips/readelflib.c
> index e50bc3ce23..d0e809d893 100644
> --- a/sysdeps/unix/sysv/linux/mips/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/mips/readelflib.c
> @@ -20,18 +20,20 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    union
>      {
> @@ -45,8 +47,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>    elf_header.eh = file_contents;
>    if (elf_header.eh->e_ident [EI_CLASS] == ELFCLASS32)
>      {
> -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        if (!ret)
>  	{
>  	  Elf32_Word flags = elf_header.eh32->e_flags;
> @@ -62,8 +64,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>      }
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* n64 libraries are always libc.so.6+.  */
>        if (!ret)
>  	{

Ok.

> diff --git a/sysdeps/unix/sysv/linux/powerpc/readelflib.c b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> index 4f9a9be254..51f8a9496a 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
> @@ -17,29 +17,31 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret;
>  
>    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> -			       file_contents, file_length);
> +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +			       soname, file_contents, file_length);
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* PowerPC 64bit libraries are always libc.so.6+.  */
>        if (!ret)
>  	*flag = FLAG_POWERPC_LIB64|FLAG_ELF_LIBC6;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/riscv/readelflib.c b/sysdeps/unix/sysv/linux/riscv/readelflib.c
> index 2aca6670a8..3822d63a05 100644
> --- a/sysdeps/unix/sysv/linux/riscv/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/riscv/readelflib.c
> @@ -17,11 +17,13 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* The ELF flags supported by our current glibc port:
> @@ -38,8 +40,8 @@ int process_elf64_file (const char *file_name, const char *lib, int *flag,
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
> @@ -52,14 +54,14 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
>  
>    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
>      {
> -      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        flags = elf32_header->e_flags;
>      }
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        flags = elf64_header->e_flags;
>      }
>  

Ok.

> diff --git a/sysdeps/unix/sysv/linux/s390/readelflib.c b/sysdeps/unix/sysv/linux/s390/readelflib.c
> index fc21af34d8..e190109e3d 100644
> --- a/sysdeps/unix/sysv/linux/s390/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/s390/readelflib.c
> @@ -16,29 +16,31 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret;
>  
>    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> -			       file_contents, file_length);
> +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +			       soname, file_contents, file_length);
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* S/390 64bit libraries are always libc.so.6+.  */
>        if (!ret)
>  	*flag = FLAG_S390_LIB64|FLAG_ELF_LIBC6;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/sparc/readelflib.c b/sysdeps/unix/sysv/linux/sparc/readelflib.c
> index d54b8dfd28..bbfc81337a 100644
> --- a/sysdeps/unix/sysv/linux/sparc/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/sparc/readelflib.c
> @@ -18,29 +18,31 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret;
>  
>    if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
> -    return process_elf32_file (file_name, lib, flag, osversion, soname,
> -			       file_contents, file_length);
> +    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +			       soname, file_contents, file_length);
>    else
>      {
> -      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -				file_contents, file_length);
> +      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +				soname, file_contents, file_length);
>        /* Sparc 64bit libraries are always libc.so.6+.  */
>        if (!ret)
>  	*flag = FLAG_SPARC_LIB64|FLAG_ELF_LIBC6;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/x86/elf-read-prop.h b/sysdeps/unix/sysv/linux/x86/elf-read-prop.h
> new file mode 100644
> index 0000000000..85affa2864
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86/elf-read-prop.h
> @@ -0,0 +1,60 @@
> +/* Support for GNU properties in ldconfig.  x86 version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifndef _ELF_READ_PROP_H
> +#define _ELF_READ_PROP_H
> +
> +#include <dl-cache.h>
> +
> +/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
> +   Return value:
> +     false: Continue processing the properties.
> +     true : Stop processing the properties.
> + */
> +static inline bool __attribute__ ((always_inline))
> +read_gnu_property (unsigned int *isal_level, uint32_t type,
> +		   uint32_t datasz, void *data)
> +{
> +  /* Property type must be in ascending order.  */
> +  if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
> +    return true;
> +
> +  if (type == GNU_PROPERTY_X86_ISA_1_NEEDED)
> +    {
> +      if (datasz == 4)
> +	{
> +	  /* The size of GNU_PROPERTY_X86_ISA_1_NEEDED must be 4 bytes.
> +	     There is no point to continue if this type is ill-formed.  */
> +	  unsigned int isa_1_needed = *(unsigned int *) data;
> +	  _Static_assert (((sizeof (isa_1_needed) * 8)
> +			   <= (1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT)),
> +			  "DL_CACHE_HWCAP_ISA_LEVEL_COUNT is too small");
> +	  if (isa_1_needed != 0)
> +	    {
> +	      unsigned int level;
> +	      asm ("bsr %1, %0" : "=r" (level) : "g" (isa_1_needed));
> +	      *isal_level = level;
> +	    }
> +	}
> +      return true;
> +    }
> +
> +  return false;
> +}
> +
> +#endif

Ok.

> diff --git a/sysdeps/unix/sysv/linux/x86/readelflib.c b/sysdeps/unix/sysv/linux/x86/readelflib.c
> index a4df70e7e6..4a9bcc82cb 100644
> --- a/sysdeps/unix/sysv/linux/x86/readelflib.c
> +++ b/sysdeps/unix/sysv/linux/x86/readelflib.c
> @@ -17,19 +17,20 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -
> -int process_elf32_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf32_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
> -int process_elf64_file (const char *file_name, const char *lib, int *flag,
> -			unsigned int *osversion, char **soname,
> +int process_elf64_file (const char *file_name, const char *lib,
> +			int *flag, unsigned int *osversion,
> +			unsigned int *isa_level, char **soname,
>  			void *file_contents, size_t file_length);
>  
>  /* Returns 0 if everything is ok, != 0 in case of error.  */
>  int
>  process_elf_file (const char *file_name, const char *lib, int *flag,
> -		  unsigned int *osversion, char **soname, void *file_contents,
> -		  size_t file_length)
> +		  unsigned int *osversion, unsigned int *isa_level,
> +		  char **soname, void *file_contents, size_t file_length)
>  {
>    ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
>    int ret, file_flag = 0;
> @@ -68,11 +69,11 @@ failed:
>      }
>  
>    if (elf_header->e_ident[EI_CLASS] == ELFCLASS32)
> -    ret = process_elf32_file (file_name, lib, flag, osversion, soname,
> -			      file_contents, file_length);
> +    ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
> +			      soname, file_contents, file_length);
>    else
> -    ret = process_elf64_file (file_name, lib, flag, osversion, soname,
> -			      file_contents, file_length);
> +    ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
> +			      soname, file_contents, file_length);
>  
>    if (!ret && file_flag)
>      *flag = file_flag;

Ok.

> diff --git a/sysdeps/unix/sysv/linux/x86_64/Makefile b/sysdeps/unix/sysv/linux/x86_64/Makefile
> index 9b82155393..5e19202ebf 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/Makefile
> +++ b/sysdeps/unix/sysv/linux/x86_64/Makefile
> @@ -13,3 +13,54 @@ endif
>  ifeq ($(subdir),misc)
>  gen-as-const-headers += sigaltstack-offsets.sym
>  endif
> +
> +ifeq ($(subdir),elf)
> +ifeq (yes,$(enable-x86-isa-level))
> +tests += \
> +  tst-glibc-hwcaps-2
> +ifeq (no,$(build-hardcoded-path-in-tests))
> +# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
> +# interferes with its test objectives.
> +tests-container += \
> +  tst-glibc-hwcaps-2-cache
> +endif
> +modules-names += \
> +  libx86-64-isa-level-1 \
> +  libx86-64-isa-level-2 \
> +  libx86-64-isa-level-3 \
> +  libx86-64-isa-level-4
> +
> +$(objpfx)tst-glibc-hwcaps-2: $(objpfx)libx86-64-isa-level.so
> +
> +$(objpfx)tst-glibc-hwcaps-2.out: \
> +  $(objpfx)glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so \
> +  $(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so \
> +  $(objpfx)glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so
> +$(objpfx)glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so: \
> +  $(objpfx)libx86-64-isa-level-2.so
> +	$(make-target-directory)
> +	cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so: \
> +  $(objpfx)libx86-64-isa-level-3.so
> +	$(make-target-directory)
> +	cp $< $@
> +$(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so: \
> +  $(objpfx)libx86-64-isa-level-4.so
> +	$(make-target-directory)
> +	cp $< $@
> +
> +CFLAGS-libx86-64-isa-level-1.os += -march=x86-64
> +CFLAGS-libx86-64-isa-level-2.os += -march=x86-64
> +CFLAGS-libx86-64-isa-level-3.os += -march=x86-64
> +CFLAGS-libx86-64-isa-level-4.os += -march=x86-64
> +
> +# The test modules are parameterized by preprocessor macros.
> +LDFLAGS-libx86-64-isa-level-1.so += -Wl,-soname,libx86-64-isa-level.so
> +LDFLAGS-libx86-64-isa-level-4.so += -Wl,-soname,libx86-64-isa-level.so
> +$(objpfx)libx86-64-isa-level%.os: $(..)/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> +	$(compile-command.c) -DVALUE=$(lastword $(subst -, ,$*)) \
> +	  -DISA_LEVEL="(1 << ($(lastword $(subst -, ,$*)) - 1))"
> +$(objpfx)libx86-64-isa-level.so: $(objpfx)libx86-64-isa-level-1.so
> +	cp $< $@
> +endif
> +endif # $(subdir) == elf

Ok.

> diff --git a/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
> new file mode 100644
> index 0000000000..fe91bfd224
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
> @@ -0,0 +1,84 @@
> +/* Check ISA level on shared object in glibc-hwcaps subdirectories.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdbool.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <elf.h>
> +#include <get-isa-level.h>
> +#include <support/check.h>
> +#include <support/test-driver.h>
> +
> +extern int dso_isa_level (void);
> +
> +static int
> +do_test (void)
> +{
> +  const struct cpu_features *cpu_features
> +    = __x86_get_cpu_features (COMMON_CPUID_INDEX_MAX);
> +  unsigned int isa_level = get_isa_level (cpu_features);
> +  bool has_isa_baseline = ((isa_level & GNU_PROPERTY_X86_ISA_1_BASELINE)
> +			   == GNU_PROPERTY_X86_ISA_1_BASELINE);
> +  bool has_isa_v2 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V2)
> +			   == GNU_PROPERTY_X86_ISA_1_V2);
> +  bool has_isa_v3 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V3)
> +			   == GNU_PROPERTY_X86_ISA_1_V3);
> +  bool has_isa_v4 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V4)
> +			   == GNU_PROPERTY_X86_ISA_1_V4);
> +
> +  if (!has_isa_baseline)
> +    return EXIT_FAILURE;
> +
> +  int level = dso_isa_level ();
> +  int ret;
> +  switch (level)
> +    {
> +    case 1:
> +    case 2:
> +      /* The default libx86-64-isa-level.so is used.  */
> +      printf ("The default shared library is used.\n");
> +      if (has_isa_v3 || has_isa_v4 || !has_isa_v2)
> +	ret = EXIT_FAILURE;
> +      else
> +	ret = EXIT_SUCCESS;
> +      break;
> +    case 3:
> +      /* libx86-64-isa-level.so marked as x86-64 ISA level 3 needed in
> +	 x86-64-v2 should be ignored on lesser CPU.  */
> +      printf ("x86-64 ISA level 3 shared library is used.\n");
> +      if (has_isa_v4 || !has_isa_v3)
> +	ret = EXIT_FAILURE;
> +      else
> +	ret = EXIT_SUCCESS;
> +      break;
> +    case 4:
> +      /* libx86-64-isa-level.so marked as x86-64 ISA level 4 needed in
> +	 x86-64-v3 should be ignored on lesser CPU.  */
> +      printf ("x86-64 ISA level 4 shared library is used.\n");
> +      if (has_isa_v4)
> +	ret = EXIT_SUCCESS;
> +      else
> +	ret = EXIT_FAILURE;
> +      break;
> +    default:
> +      abort ();
> +    }
> +  return ret;
> +}
> +
> +#include <support/test-driver.c>

Ok.

> diff --git a/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> new file mode 100644
> index 0000000000..2813d627cc
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
> @@ -0,0 +1,4 @@
> +#define INCLUDE_X86_ISA_LEVEL
> +#define MARKER dso_isa_level
> +#include <isa-level.c>
> +#include <markermodMARKER-VALUE.c>
> diff --git a/sysdeps/x86/dl-isa-level.h b/sysdeps/x86/dl-isa-level.h
> new file mode 100644
> index 0000000000..afe390c365
> --- /dev/null
> +++ b/sysdeps/x86/dl-isa-level.h
> @@ -0,0 +1,31 @@
> +/* Support for reading ISA level in /etc/ld.so.cache files written by
> +   Linux ldconfig.  x86 version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sys/platform/x86.h>
> +
> +/* Return true if the ISA level in ENTRY is compatible with CPU.  */
> +static inline bool
> +dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
> +{
> +  const struct cpu_features *cpu_features = __get_cpu_features ();
> +  unsigned int isa_level
> +    = 1 << ((entry->hwcap >> 32) & DL_CACHE_HWCAP_ISA_LEVEL_MASK);
> +
> +  return (isa_level & cpu_features->isa_1) == isa_level;
> +}
> -- 
> 2.29.2

Ok.
H.J. Lu Jan. 13, 2021, 2:12 p.m. UTC | #2
On Wed, Jan 13, 2021 at 5:47 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 12/01/2021 20:32, H.J. Lu wrote:
> > On Tue, Jan 12, 2021 at 8:25 AM Adhemerval Zanella
> > <adhemerval.zanella@linaro.org> wrote:
> >>
> >>
> >>
> >> On 09/12/2020 00:27, H.J. Lu via Libc-alpha wrote:
> >>> On Tue, Dec 8, 2020 at 7:31 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>> @@ -850,6 +859,7 @@ struct aux_cache_entry
> >>>    struct aux_cache_entry_id id;
> >>>    int flags;
> >>>    unsigned int osversion;
> >>> +  unsigned int isa_level;
> >>>    int used;
> >>>    char *soname;
> >>>    struct aux_cache_entry *next;
> >>> @@ -863,7 +873,7 @@ struct aux_cache_file_entry
> >>>    int32_t flags;             /* This is 1 for an ELF library.  */
> >>>    uint32_t soname;           /* String table indice.  */
> >>>    uint32_t osversion;                /* Required OS version.  */
> >>> -  int32_t pad;
> >>> +  uint32_t isa_level;                /* Required ISA level.   */
> >>>  };
> >>>
> >>
> >> I think it would be good to have a _Static_assert with the
> >> expected aux_cache_entry size.
> >
> > What would that be?  aux_cache_entry_id size is increased
> > by 4 bytes with my patch.
>
> My understanding is aux_cache_entry_id keeps the same and you are using
> an unused field on *aux_cache_file_entry* to add the isa_level.  Their
> sizes should kept the same (since isa_level is the same size of the
> previous pad).
>
> But the _Static_assert might indeed unrequired, the load_aux_cache already
> check if the aux_cache_file_entry does match the file size and uses an
> empty auxiliary cache otherwise (init_aux_cache).
>
> elf/cache.c
>
> 1008   if (aux_cache == MAP_FAILED
> 1009       || aux_cache_size < sizeof (struct aux_cache_file)
> 1010       || memcmp (aux_cache->magic, AUX_CACHEMAGIC, sizeof AUX_CACHEMAGIC - 1)
> 1011       || aux_cache_size != (sizeof (struct aux_cache_file)
> 1012                             + aux_cache->nlibs * sizeof (struct aux_cache_file_entry)
> 1013                             + aux_cache->len_strings))
> 1014     {
> 1015       close (fd);
> 1016       init_aux_cache ();
> 1017       return;
> 1018     }
>
>
> >>>  /* Return true if the ENTRY->hwcap value indicates that
> >>>     DL_CACHE_HWCAP_EXTENSION is used.  */
> >>>  static inline bool
> >>>  dl_cache_hwcap_extension (struct file_entry_new *entry)
> >>>  {
> >>> -  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
> >>> -     is a different kind of extension.  */
> >>> -  return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
> >>> +  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits, except for the
> >>> +     ISA level bits, as well, this is a different kind of extension.  */
> >>> +  return (((entry->hwcap >> 32) & ~DL_CACHE_HWCAP_ISA_LEVEL_MASK)
> >>> +       == (DL_CACHE_HWCAP_EXTENSION >> 32));
> >>>  }
> >>>
> >>>  /* See flags member of struct cache_file_new below.  */
> >>
> >> The comment sounds confusing.
> >
> > I changed it to
> >
> >   /* This is an hwcap extension if only the DL_CACHE_HWCAP_EXTENSION bit
> >      is set, ignoring the lower 32 bits as well as the ISA level bits in
> >      the upper 32 bits.  */
>
> Thanks.
>
> ---
> > From 40bacb7470f0c8d8eabd4d3b24057566d45ca5dd Mon Sep 17 00:00:00 2001
> > From: "H.J. Lu" <hjl.tools@gmail.com>
> > Date: Sat, 5 Dec 2020 07:01:58 -0800
> > Subject: [PATCH] ldconfig/x86: Store ISA level in cache and aux cache
> >
> > Store ISA level in the portion of the unused upper 32 bits of the hwcaps
> > field in cache and the unused pad field in aux cache.  ISA level is stored
> > and checked only for shared objects in glibc-hwcaps subdirectories.  The
> > shared objects in the default directories aren't checked since there are
> > no fallbacks for these shared objects.
> >
> > Tested on x86-64-v2, x86-64-v3 and x86-64-v4 machines with
> > --disable-hardcoded-path-in-tests and --enable-hardcoded-path-in-tests.
>
> LGTM, thanks.
>
> Please update the release page once you commit it.

Done.   Thanks.

> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>
>
diff mbox series

Patch

From 40bacb7470f0c8d8eabd4d3b24057566d45ca5dd Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 5 Dec 2020 07:01:58 -0800
Subject: [PATCH] ldconfig/x86: Store ISA level in cache and aux cache

Store ISA level in the portion of the unused upper 32 bits of the hwcaps
field in cache and the unused pad field in aux cache.  ISA level is stored
and checked only for shared objects in glibc-hwcaps subdirectories.  The
shared objects in the default directories aren't checked since there are
no fallbacks for these shared objects.

Tested on x86-64-v2, x86-64-v3 and x86-64-v4 machines with
--disable-hardcoded-path-in-tests and --enable-hardcoded-path-in-tests.
---
 elf/cache.c                                   | 39 +++++++--
 elf/dl-cache.c                                |  4 +
 elf/ldconfig.c                                | 18 ++--
 elf/readelflib.c                              | 81 +++++++++++++++++-
 elf/readlib.c                                 |  7 +-
 elf/tst-glibc-hwcaps-2-cache.c                | 45 ++++++++++
 .../etc/ld.so.conf                            |  2 +
 .../postclean.req                             |  0
 elf/tst-glibc-hwcaps-2-cache.script           |  8 ++
 sysdeps/generic/dl-cache.h                    | 16 +++-
 sysdeps/generic/dl-isa-level.h                | 25 ++++++
 sysdeps/generic/elf-read-prop.h               | 34 ++++++++
 sysdeps/generic/ldconfig.h                    | 22 +++--
 sysdeps/unix/sysv/linux/arm/readelflib.c      | 22 ++---
 sysdeps/unix/sysv/linux/ia64/readelflib.c     | 22 ++---
 sysdeps/unix/sysv/linux/mips/readelflib.c     | 22 ++---
 sysdeps/unix/sysv/linux/powerpc/readelflib.c  | 22 ++---
 sysdeps/unix/sysv/linux/riscv/readelflib.c    | 22 ++---
 sysdeps/unix/sysv/linux/s390/readelflib.c     | 22 ++---
 sysdeps/unix/sysv/linux/sparc/readelflib.c    | 22 ++---
 sysdeps/unix/sysv/linux/x86/elf-read-prop.h   | 60 +++++++++++++
 sysdeps/unix/sysv/linux/x86/readelflib.c      | 23 ++---
 sysdeps/unix/sysv/linux/x86_64/Makefile       | 51 +++++++++++
 .../sysv/linux/x86_64/tst-glibc-hwcaps-2.c    | 84 +++++++++++++++++++
 .../linux/x86_64/x86-64-isa-level-VALUE.c     |  4 +
 sysdeps/x86/dl-isa-level.h                    | 31 +++++++
 26 files changed, 598 insertions(+), 110 deletions(-)
 create mode 100644 elf/tst-glibc-hwcaps-2-cache.c
 create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
 create mode 100644 elf/tst-glibc-hwcaps-2-cache.root/postclean.req
 create mode 100644 elf/tst-glibc-hwcaps-2-cache.script
 create mode 100644 sysdeps/generic/dl-isa-level.h
 create mode 100644 sysdeps/generic/elf-read-prop.h
 create mode 100644 sysdeps/unix/sysv/linux/x86/elf-read-prop.h
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
 create mode 100644 sysdeps/x86/dl-isa-level.h

diff --git a/elf/cache.c b/elf/cache.c
index 11ce4ade8a..c01d302072 100644
--- a/elf/cache.c
+++ b/elf/cache.c
@@ -146,6 +146,7 @@  struct cache_entry
   struct stringtable_entry *path; /* Path to find library.  */
   int flags;			/* Flags to indicate kind of library.  */
   unsigned int osversion;	/* Required OS version.  */
+  unsigned int isa_level;	/* Required ISA level.  */
   uint64_t hwcap;		/* Important hardware capabilities.  */
   int bits_hwcap;		/* Number of bits set in hwcap.  */
 
@@ -549,6 +550,19 @@  write_extensions (int fd, uint32_t str_offset,
   free (ext);
 }
 
+/* Compute the hwcap value from ENTRY.  */
+static inline uint64_t
+compute_hwcap_value (struct cache_entry *entry)
+{
+  if (entry->isa_level > DL_CACHE_HWCAP_ISA_LEVEL_MASK)
+    error (EXIT_FAILURE, 0, _("%s: ISA level is too high (%d > %d)"),
+	   entry->path->string, entry->isa_level,
+	   DL_CACHE_HWCAP_ISA_LEVEL_MASK);
+  return (DL_CACHE_HWCAP_EXTENSION
+	  | (((uint64_t) entry->isa_level) << 32)
+	  | entry->hwcaps->section_index);
+}
+
 /* Save the contents of the cache.  */
 void
 save_cache (const char *cache_name)
@@ -662,7 +676,7 @@  save_cache (const char *cache_name)
 	    file_entries_new->libs[idx_new].hwcap = entry->hwcap;
 	  else
 	    file_entries_new->libs[idx_new].hwcap
-	      = DL_CACHE_HWCAP_EXTENSION | entry->hwcaps->section_index;
+	      = compute_hwcap_value (entry);
 	  file_entries_new->libs[idx_new].key
 	    = str_offset + entry->lib->offset;
 	  file_entries_new->libs[idx_new].value
@@ -777,7 +791,8 @@  save_cache (const char *cache_name)
 /* Add one library to the cache.  */
 void
 add_to_cache (const char *path, const char *filename, const char *soname,
-	      int flags, unsigned int osversion, uint64_t hwcap,
+	      int flags, unsigned int osversion,
+	      unsigned int isa_level, uint64_t hwcap,
 	      struct glibc_hwcaps_subdirectory *hwcaps)
 {
   struct cache_entry *new_entry = xmalloc (sizeof (*new_entry));
@@ -795,6 +810,7 @@  add_to_cache (const char *path, const char *filename, const char *soname,
   new_entry->path = path_interned;
   new_entry->flags = flags;
   new_entry->osversion = osversion;
+  new_entry->isa_level = isa_level;
   new_entry->hwcap = hwcap;
   new_entry->hwcaps = hwcaps;
   new_entry->bits_hwcap = 0;
@@ -851,6 +867,7 @@  struct aux_cache_entry
   struct aux_cache_entry_id id;
   int flags;
   unsigned int osversion;
+  unsigned int isa_level;
   int used;
   char *soname;
   struct aux_cache_entry *next;
@@ -864,7 +881,7 @@  struct aux_cache_file_entry
   int32_t flags;		/* This is 1 for an ELF library.  */
   uint32_t soname;		/* String table indice.  */
   uint32_t osversion;		/* Required OS version.	 */
-  int32_t pad;
+  uint32_t isa_level;		/* Required ISA level.	 */
 };
 
 /* ldconfig maintains an auxiliary cache file that allows
@@ -915,7 +932,8 @@  init_aux_cache (void)
 
 int
 search_aux_cache (struct stat64 *stat_buf, int *flags,
-		  unsigned int *osversion, char **soname)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname)
 {
   struct aux_cache_entry_id id;
   id.ino = (uint64_t) stat_buf->st_ino;
@@ -933,6 +951,7 @@  search_aux_cache (struct stat64 *stat_buf, int *flags,
       {
 	*flags = entry->flags;
 	*osversion = entry->osversion;
+	*isa_level = entry->isa_level;
 	if (entry->soname != NULL)
 	  *soname = xstrdup (entry->soname);
 	else
@@ -946,7 +965,8 @@  search_aux_cache (struct stat64 *stat_buf, int *flags,
 
 static void
 insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
-		     unsigned int osversion, const char *soname, int used)
+		     unsigned int osversion, unsigned int isa_level,
+		     const char *soname, int used)
 {
   size_t hash = aux_cache_entry_id_hash (id) % aux_hash_size;
   struct aux_cache_entry *entry;
@@ -962,6 +982,7 @@  insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
   entry->id = *id;
   entry->flags = flags;
   entry->osversion = osversion;
+  entry->isa_level = isa_level;
   entry->used = used;
   if (soname != NULL)
     entry->soname = memcpy ((char *) (entry + 1), soname, len);
@@ -973,14 +994,15 @@  insert_to_aux_cache (struct aux_cache_entry_id *id, int flags,
 
 void
 add_to_aux_cache (struct stat64 *stat_buf, int flags,
-		  unsigned int osversion, const char *soname)
+		  unsigned int osversion, unsigned int isa_level,
+		  const char *soname)
 {
   struct aux_cache_entry_id id;
   id.ino = (uint64_t) stat_buf->st_ino;
   id.ctime = (uint64_t) stat_buf->st_ctime;
   id.size = (uint64_t) stat_buf->st_size;
   id.dev = (uint64_t) stat_buf->st_dev;
-  insert_to_aux_cache (&id, flags, osversion, soname, 1);
+  insert_to_aux_cache (&id, flags, osversion, isa_level, soname, 1);
 }
 
 /* Load auxiliary cache to search for unchanged entries.   */
@@ -1026,6 +1048,7 @@  load_aux_cache (const char *aux_cache_name)
     insert_to_aux_cache (&aux_cache->libs[i].id,
 			 aux_cache->libs[i].flags,
 			 aux_cache->libs[i].osversion,
+			 aux_cache->libs[i].isa_level,
 			 aux_cache->libs[i].soname == 0
 			 ? NULL : aux_cache_data + aux_cache->libs[i].soname,
 			 0);
@@ -1094,7 +1117,7 @@  save_aux_cache (const char *aux_cache_name)
 	      str_offset += len;
 	    }
 	  file_entries->libs[idx].osversion = entry->osversion;
-	  file_entries->libs[idx++].pad = 0;
+	  file_entries->libs[idx++].isa_level = entry->isa_level;
 	}
 
   /* Write out auxiliary cache file.  */
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 935e3a60b4..32f3bef5ea 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -25,6 +25,7 @@ 
 #include <stdint.h>
 #include <_itoa.h>
 #include <dl-hwcaps.h>
+#include <dl-isa-level.h>
 
 #ifndef _DL_PLATFORMS_COUNT
 # define _DL_PLATFORMS_COUNT 0
@@ -284,6 +285,9 @@  search_cache (const char *string_table, uint32_t string_table_size,
 
 #ifdef SHARED
 			  named_hwcap = dl_cache_hwcap_extension (libnew);
+			  if (named_hwcap
+			      && !dl_cache_hwcap_isa_level_compatible (libnew))
+			    continue;
 #endif
 
 			  /* The entries with named/extension hwcaps
diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index bbcf8f5c5c..28ed637a29 100644
--- a/elf/ldconfig.c
+++ b/elf/ldconfig.c
@@ -655,6 +655,7 @@  manual_link (char *library)
   struct stat64 stat_buf;
   int flag;
   unsigned int osversion;
+  unsigned int isa_level;
 
   /* Prepare arguments for create_links call.  Split library name in
      directory and filename first.  Since path is allocated, we've got
@@ -721,7 +722,7 @@  manual_link (char *library)
     }
 
   if (process_file (real_library, library, libname, &flag, &osversion,
-		    &soname, 0, &stat_buf))
+		    &isa_level, &soname, 0, &stat_buf))
     {
       error (0, 0, _("No link created since soname could not be found for %s"),
 	     library);
@@ -768,6 +769,7 @@  struct dlib_entry
   int flag;
   int is_link;
   unsigned int osversion;
+  unsigned int isa_level;
   struct dlib_entry *next;
 };
 
@@ -980,17 +982,21 @@  search_dir (const struct dir_entry *entry)
 	 library already and it's not changed.  */
       char *soname;
       unsigned int osversion;
-      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &soname))
+      unsigned int isa_level;
+      if (!search_aux_cache (&lstat_buf, &flag, &osversion, &isa_level,
+			     &soname))
 	{
 	  if (process_file (real_name, file_name, direntry->d_name, &flag,
-			    &osversion, &soname, is_link, &lstat_buf))
+			    &osversion, &isa_level, &soname, is_link,
+			    &lstat_buf))
 	    {
 	      if (real_name != real_file_name)
 		free (real_name);
 	      continue;
 	    }
 	  else if (opt_build_cache)
-	    add_to_aux_cache (&lstat_buf, flag, osversion, soname);
+	    add_to_aux_cache (&lstat_buf, flag, osversion, isa_level,
+			      soname);
 	}
 
       if (soname == NULL)
@@ -1096,6 +1102,7 @@  search_dir (const struct dir_entry *entry)
 		  dlib_ptr->name = xstrdup (direntry->d_name);
 		  dlib_ptr->is_link = is_link;
 		  dlib_ptr->osversion = osversion;
+		  dlib_ptr->isa_level = isa_level;
 		}
 	      /* Don't add this library, abort loop.  */
 	      /* Also free soname, since it's dynamically allocated.  */
@@ -1112,6 +1119,7 @@  search_dir (const struct dir_entry *entry)
 	  dlib_ptr->flag = flag;
 	  dlib_ptr->is_link = is_link;
 	  dlib_ptr->osversion = osversion;
+	  dlib_ptr->isa_level = isa_level;
 	  /* Add at head of list.  */
 	  dlib_ptr->next = dlibs;
 	  dlibs = dlib_ptr;
@@ -1149,7 +1157,7 @@  search_dir (const struct dir_entry *entry)
       if (opt_build_cache)
 	add_to_cache (entry->path, filename, dlib_ptr->soname,
 		      dlib_ptr->flag, dlib_ptr->osversion,
-		      hwcap, entry->hwcaps);
+		      dlib_ptr->isa_level, hwcap, entry->hwcaps);
     }
 
   /* Free all resources.  */
diff --git a/elf/readelflib.c b/elf/readelflib.c
index cdea79d729..c09425a574 100644
--- a/elf/readelflib.c
+++ b/elf/readelflib.c
@@ -17,6 +17,8 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <elf-read-prop.h>
+
 /* This code is a heavily simplified version of the readelf program
    that's part of the current binutils development version.  For architectures
    which need to handle both 32bit and 64bit ELF libraries,  this file is
@@ -40,8 +42,8 @@  do								\
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   int i;
   unsigned int j;
@@ -86,6 +88,9 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
      libc5/libc6.  */
   *flag = FLAG_ELF;
 
+  /* The default ISA level is 0.  */
+  *isa_level = 0;
+
   dynamic_addr = 0;
   dynamic_size = 0;
   program_interpreter = NULL;
@@ -164,6 +169,78 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
 	    }
 	  break;
 
+	case PT_GNU_PROPERTY:
+	  /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes
+	     in 32-bit objects and to 8 bytes in 64-bit objects.  Skip
+	     notes with incorrect alignment.  */
+	  if (segment->p_align == (__ELF_NATIVE_CLASS / 8))
+	    {
+	      const ElfW(Nhdr) *note = (const void *) (file_contents
+						       + segment->p_offset);
+	      const ElfW(Addr) size = segment->p_filesz;
+	      const ElfW(Addr) align = segment->p_align;
+
+	      const ElfW(Addr) start = (ElfW(Addr)) (uintptr_t) note;
+	      unsigned int last_type = 0;
+
+	      while ((ElfW(Addr)) (uintptr_t) (note + 1) - start < size)
+		{
+		  /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
+		  if (note->n_namesz == 4
+		      && note->n_type == NT_GNU_PROPERTY_TYPE_0
+		      && memcmp (note + 1, "GNU", 4) == 0)
+		    {
+		      /* Check for invalid property.  */
+		      if (note->n_descsz < 8
+			  || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
+			goto done;
+
+		      /* Start and end of property array.  */
+		      unsigned char *ptr = (unsigned char *) (note + 1) + 4;
+		      unsigned char *ptr_end = ptr + note->n_descsz;
+
+		      do
+			{
+			  unsigned int type = *(unsigned int *) ptr;
+			  unsigned int datasz = *(unsigned int *) (ptr + 4);
+
+			  /* Property type must be in ascending order.  */
+			  if (type < last_type)
+			    goto done;
+
+			  ptr += 8;
+			  if ((ptr + datasz) > ptr_end)
+			    goto done;
+
+			  last_type = type;
+
+			  /* Target specific property processing.
+			     Return value:
+			       false: Continue processing the properties.
+			       true : Stop processing the properties.
+			   */
+			  if (read_gnu_property (isa_level, type,
+						 datasz, ptr))
+			    goto done;
+
+			  /* Check the next property item.  */
+			  ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
+			}
+		      while ((ptr_end - ptr) >= 8);
+
+		      /* Only handle one NT_GNU_PROPERTY_TYPE_0.  */
+		      goto done;
+		    }
+
+		  note = ((const void *) note
+			  + ELF_NOTE_NEXT_OFFSET (note->n_namesz,
+						  note->n_descsz,
+						  align));
+		}
+	    }
+done:
+	  break;
+
 	default:
 	  break;
 	}
diff --git a/elf/readlib.c b/elf/readlib.c
index 3d52c9a980..7383c23249 100644
--- a/elf/readlib.c
+++ b/elf/readlib.c
@@ -75,7 +75,8 @@  is_gdb_python_file (const char *name)
 int
 process_file (const char *real_file_name, const char *file_name,
 	      const char *lib, int *flag, unsigned int *osversion,
-	      char **soname, int is_link, struct stat64 *stat_buf)
+	      unsigned int *isa_level, char **soname, int is_link,
+	      struct stat64 *stat_buf)
 {
   FILE *file;
   struct stat64 statbuf;
@@ -173,8 +174,8 @@  process_file (const char *real_file_name, const char *file_name,
   /* Libraries have to be shared object files.  */
   else if (elf_header->e_type != ET_DYN)
     ret = 1;
-  else if (process_elf_file (file_name, lib, flag, osversion, soname,
-			     file_contents, statbuf.st_size))
+  else if (process_elf_file (file_name, lib, flag, osversion, isa_level,
+			     soname, file_contents, statbuf.st_size))
     ret = 1;
 
  done:
diff --git a/elf/tst-glibc-hwcaps-2-cache.c b/elf/tst-glibc-hwcaps-2-cache.c
new file mode 100644
index 0000000000..97d9835ddb
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-2-cache.c
@@ -0,0 +1,45 @@ 
+/* Wrapper to invoke tst-glibc-hwcaps-2 in a container to test ldconfig.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* This program is just a wrapper that runs ldconfig followed by
+   tst-glibc-hwcaps-2.  The actual test is provided via an
+   implementation in a sysdeps subdirectory.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <support/support.h>
+#include <support/capture_subprocess.h>
+
+int
+main (int argc, char **argv)
+{
+  /* Run ldconfig to populate the cache.  */
+  char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+  struct support_capture_subprocess result =
+    support_capture_subprogram (command,  &((char *) { NULL }));
+  support_capture_subprocess_check (&result, "ldconfig", 0, sc_allow_none);
+  free (command);
+
+  /* Reuse tst-glibc-hwcaps.  Since this code is running in a
+     container, we can launch it directly.  */
+  char *path = xasprintf ("%s/elf/tst-glibc-hwcaps-2", support_objdir_root);
+  execv (path, argv);
+  printf ("error: execv of %s failed: %m\n", path);
+  return 1;
+}
diff --git a/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
new file mode 100644
index 0000000000..e1e74dbda2
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-2-cache.root/etc/ld.so.conf
@@ -0,0 +1,2 @@ 
+# This file was created to suppress a warning from ldconfig:
+# /sbin/ldconfig: Warning: ignoring configuration file that cannot be opened: /etc/ld.so.conf: No such file or directory
diff --git a/elf/tst-glibc-hwcaps-2-cache.root/postclean.req b/elf/tst-glibc-hwcaps-2-cache.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-glibc-hwcaps-2-cache.script b/elf/tst-glibc-hwcaps-2-cache.script
new file mode 100644
index 0000000000..8e4e9896ee
--- /dev/null
+++ b/elf/tst-glibc-hwcaps-2-cache.script
@@ -0,0 +1,8 @@ 
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
+
+mkdirp 0770 $L/glibc-hwcaps/x86-64-v2
+mkdirp 0770 $L/glibc-hwcaps/x86-64-v3
+cp $B/elf/libx86-64-isa-level-1.so $L/libx86-64-isa-level.so
+cp $B/elf/libx86-64-isa-level-3.so $L/glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so
+cp $B/elf/libx86-64-isa-level-4.so $L/glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so
diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h
index c7eca70d0c..964d50a486 100644
--- a/sysdeps/generic/dl-cache.h
+++ b/sysdeps/generic/dl-cache.h
@@ -106,14 +106,24 @@  struct file_entry_new
    entries.  */
 #define DL_CACHE_HWCAP_EXTENSION (1ULL << 62)
 
+/* The number of the ISA level bits in the upper 32 bits of the hwcap
+   field.  */
+#define DL_CACHE_HWCAP_ISA_LEVEL_COUNT 10
+
+/* The mask of the ISA level bits in the hwcap field.  */
+#define DL_CACHE_HWCAP_ISA_LEVEL_MASK \
+  ((1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT) -1)
+
 /* Return true if the ENTRY->hwcap value indicates that
    DL_CACHE_HWCAP_EXTENSION is used.  */
 static inline bool
 dl_cache_hwcap_extension (struct file_entry_new *entry)
 {
-  /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
-     is a different kind of extension.  */
-  return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
+  /* This is an hwcap extension if only the DL_CACHE_HWCAP_EXTENSION bit
+     is set, ignoring the lower 32 bits as well as the ISA level bits in
+     the upper 32 bits.  */
+  return (((entry->hwcap >> 32) & ~DL_CACHE_HWCAP_ISA_LEVEL_MASK)
+	  == (DL_CACHE_HWCAP_EXTENSION >> 32));
 }
 
 /* See flags member of struct cache_file_new below.  */
diff --git a/sysdeps/generic/dl-isa-level.h b/sysdeps/generic/dl-isa-level.h
new file mode 100644
index 0000000000..6fcd319c49
--- /dev/null
+++ b/sysdeps/generic/dl-isa-level.h
@@ -0,0 +1,25 @@ 
+/* Support for reading ISA level in /etc/ld.so.cache files written by
+   Linux ldconfig.  Generic version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Return true if the ISA level in ENTRY is compatible with CPU.  */
+static inline bool
+dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
+{
+  return true;
+}
diff --git a/sysdeps/generic/elf-read-prop.h b/sysdeps/generic/elf-read-prop.h
new file mode 100644
index 0000000000..98c3d2acb5
--- /dev/null
+++ b/sysdeps/generic/elf-read-prop.h
@@ -0,0 +1,34 @@ 
+/* Support for GNU properties in ldconfig.  Generic version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _ELF_READ_PROP_H
+#define _ELF_READ_PROP_H
+
+/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
+   Return value:
+     false: Continue processing the properties.
+     true : Stop processing the properties.
+ */
+static inline bool __attribute__ ((always_inline))
+read_gnu_property (unsigned int *isal_level, uint32_t type, uint32_t
+		   datasz, void *data)
+{
+  return true;
+}
+
+#endif
diff --git a/sysdeps/generic/ldconfig.h b/sysdeps/generic/ldconfig.h
index eb070fd259..3ab757077d 100644
--- a/sysdeps/generic/ldconfig.h
+++ b/sysdeps/generic/ldconfig.h
@@ -70,8 +70,9 @@  const char *glibc_hwcaps_subdirectory_name
   (const struct glibc_hwcaps_subdirectory *);
 
 extern void add_to_cache (const char *path, const char *filename,
-			  const char *soname,
-			  int flags, unsigned int osversion, uint64_t hwcap,
+			  const char *soname, int flags,
+			  unsigned int osversion, unsigned int isa_level,
+			  uint64_t hwcap,
 			  struct glibc_hwcaps_subdirectory *);
 
 extern void init_aux_cache (void);
@@ -79,23 +80,28 @@  extern void init_aux_cache (void);
 extern void load_aux_cache (const char *aux_cache_name);
 
 extern int search_aux_cache (struct stat64 *stat_buf, int *flags,
-			     unsigned int *osversion, char **soname);
+			     unsigned int *osversion,
+			     unsigned int *isa_level, char **soname);
 
 extern void add_to_aux_cache (struct stat64 *stat_buf, int flags,
-			      unsigned int osversion, const char *soname);
+			      unsigned int osversion,
+			      unsigned int isa_level, const char *soname);
 
 extern void save_aux_cache (const char *aux_cache_name);
 
 /* Declared in readlib.c.  */
 extern int process_file (const char *real_file_name, const char *file_name,
-			 const char *lib, int *flag, unsigned int *osversion,
-			 char **soname, int is_link, struct stat64 *stat_buf);
+			 const char *lib, int *flag,
+			 unsigned int *osversion, unsigned int *isa_level,
+			 char **soname, int is_link,
+			 struct stat64 *stat_buf);
 
 extern char *implicit_soname (const char *lib, int flag);
 
 /* Declared in readelflib.c.  */
-extern int process_elf_file (const char *file_name, const char *lib, int *flag,
-			     unsigned int *osversion, char **soname,
+extern int process_elf_file (const char *file_name, const char *lib,
+			     int *flag, unsigned int *osversion,
+			     unsigned int *isa_level, char **soname,
 			     void *file_contents, size_t file_length);
 
 /* Declared in chroot_canon.c.  */
diff --git a/sysdeps/unix/sysv/linux/arm/readelflib.c b/sysdeps/unix/sysv/linux/arm/readelflib.c
index 2d3ecb1eef..ade2f49aeb 100644
--- a/sysdeps/unix/sysv/linux/arm/readelflib.c
+++ b/sysdeps/unix/sysv/linux/arm/readelflib.c
@@ -18,18 +18,20 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret;
@@ -38,8 +40,8 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
     {
       Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
 
-      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
 
       if (!ret && EF_ARM_EABI_VERSION (elf32_header->e_flags) == EF_ARM_EABI_VER5)
 	{
@@ -57,8 +59,8 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
     }
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* AArch64 libraries are always libc.so.6+.  */
       if (!ret)
 	*flag = FLAG_AARCH64_LIB64|FLAG_ELF_LIBC6;
diff --git a/sysdeps/unix/sysv/linux/ia64/readelflib.c b/sysdeps/unix/sysv/linux/ia64/readelflib.c
index 7fb3ace359..2aa32666aa 100644
--- a/sysdeps/unix/sysv/linux/ia64/readelflib.c
+++ b/sysdeps/unix/sysv/linux/ia64/readelflib.c
@@ -16,29 +16,31 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname,
-		  void *file_contents, size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret;
 
   if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
-    return process_elf32_file (file_name, lib, flag, osversion, soname,
-			       file_contents, file_length);
+    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
+			       soname, file_contents, file_length);
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* Intel 64bit libraries are always libc.so.6+.  */
       if (!ret)
 	*flag = FLAG_IA64_LIB64|FLAG_ELF_LIBC6;
diff --git a/sysdeps/unix/sysv/linux/mips/readelflib.c b/sysdeps/unix/sysv/linux/mips/readelflib.c
index e50bc3ce23..d0e809d893 100644
--- a/sysdeps/unix/sysv/linux/mips/readelflib.c
+++ b/sysdeps/unix/sysv/linux/mips/readelflib.c
@@ -20,18 +20,20 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   union
     {
@@ -45,8 +47,8 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
   elf_header.eh = file_contents;
   if (elf_header.eh->e_ident [EI_CLASS] == ELFCLASS32)
     {
-      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       if (!ret)
 	{
 	  Elf32_Word flags = elf_header.eh32->e_flags;
@@ -62,8 +64,8 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
     }
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* n64 libraries are always libc.so.6+.  */
       if (!ret)
 	{
diff --git a/sysdeps/unix/sysv/linux/powerpc/readelflib.c b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
index 4f9a9be254..51f8a9496a 100644
--- a/sysdeps/unix/sysv/linux/powerpc/readelflib.c
+++ b/sysdeps/unix/sysv/linux/powerpc/readelflib.c
@@ -17,29 +17,31 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret;
 
   if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
-    return process_elf32_file (file_name, lib, flag, osversion, soname,
-			       file_contents, file_length);
+    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
+			       soname, file_contents, file_length);
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* PowerPC 64bit libraries are always libc.so.6+.  */
       if (!ret)
 	*flag = FLAG_POWERPC_LIB64|FLAG_ELF_LIBC6;
diff --git a/sysdeps/unix/sysv/linux/riscv/readelflib.c b/sysdeps/unix/sysv/linux/riscv/readelflib.c
index 2aca6670a8..3822d63a05 100644
--- a/sysdeps/unix/sysv/linux/riscv/readelflib.c
+++ b/sysdeps/unix/sysv/linux/riscv/readelflib.c
@@ -17,11 +17,13 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* The ELF flags supported by our current glibc port:
@@ -38,8 +40,8 @@  int process_elf64_file (const char *file_name, const char *lib, int *flag,
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
@@ -52,14 +54,14 @@  process_elf_file (const char *file_name, const char *lib, int *flag,
 
   if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
     {
-      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       flags = elf32_header->e_flags;
     }
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       flags = elf64_header->e_flags;
     }
 
diff --git a/sysdeps/unix/sysv/linux/s390/readelflib.c b/sysdeps/unix/sysv/linux/s390/readelflib.c
index fc21af34d8..e190109e3d 100644
--- a/sysdeps/unix/sysv/linux/s390/readelflib.c
+++ b/sysdeps/unix/sysv/linux/s390/readelflib.c
@@ -16,29 +16,31 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret;
 
   if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
-    return process_elf32_file (file_name, lib, flag, osversion, soname,
-			       file_contents, file_length);
+    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
+			       soname, file_contents, file_length);
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* S/390 64bit libraries are always libc.so.6+.  */
       if (!ret)
 	*flag = FLAG_S390_LIB64|FLAG_ELF_LIBC6;
diff --git a/sysdeps/unix/sysv/linux/sparc/readelflib.c b/sysdeps/unix/sysv/linux/sparc/readelflib.c
index d54b8dfd28..bbfc81337a 100644
--- a/sysdeps/unix/sysv/linux/sparc/readelflib.c
+++ b/sysdeps/unix/sysv/linux/sparc/readelflib.c
@@ -18,29 +18,31 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret;
 
   if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
-    return process_elf32_file (file_name, lib, flag, osversion, soname,
-			       file_contents, file_length);
+    return process_elf32_file (file_name, lib, flag, osversion, isa_level,
+			       soname, file_contents, file_length);
   else
     {
-      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-				file_contents, file_length);
+      ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+				soname, file_contents, file_length);
       /* Sparc 64bit libraries are always libc.so.6+.  */
       if (!ret)
 	*flag = FLAG_SPARC_LIB64|FLAG_ELF_LIBC6;
diff --git a/sysdeps/unix/sysv/linux/x86/elf-read-prop.h b/sysdeps/unix/sysv/linux/x86/elf-read-prop.h
new file mode 100644
index 0000000000..85affa2864
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/elf-read-prop.h
@@ -0,0 +1,60 @@ 
+/* Support for GNU properties in ldconfig.  x86 version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _ELF_READ_PROP_H
+#define _ELF_READ_PROP_H
+
+#include <dl-cache.h>
+
+/* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of SEGMENT.
+   Return value:
+     false: Continue processing the properties.
+     true : Stop processing the properties.
+ */
+static inline bool __attribute__ ((always_inline))
+read_gnu_property (unsigned int *isal_level, uint32_t type,
+		   uint32_t datasz, void *data)
+{
+  /* Property type must be in ascending order.  */
+  if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
+    return true;
+
+  if (type == GNU_PROPERTY_X86_ISA_1_NEEDED)
+    {
+      if (datasz == 4)
+	{
+	  /* The size of GNU_PROPERTY_X86_ISA_1_NEEDED must be 4 bytes.
+	     There is no point to continue if this type is ill-formed.  */
+	  unsigned int isa_1_needed = *(unsigned int *) data;
+	  _Static_assert (((sizeof (isa_1_needed) * 8)
+			   <= (1 << DL_CACHE_HWCAP_ISA_LEVEL_COUNT)),
+			  "DL_CACHE_HWCAP_ISA_LEVEL_COUNT is too small");
+	  if (isa_1_needed != 0)
+	    {
+	      unsigned int level;
+	      asm ("bsr %1, %0" : "=r" (level) : "g" (isa_1_needed));
+	      *isal_level = level;
+	    }
+	}
+      return true;
+    }
+
+  return false;
+}
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/x86/readelflib.c b/sysdeps/unix/sysv/linux/x86/readelflib.c
index a4df70e7e6..4a9bcc82cb 100644
--- a/sysdeps/unix/sysv/linux/x86/readelflib.c
+++ b/sysdeps/unix/sysv/linux/x86/readelflib.c
@@ -17,19 +17,20 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-
-int process_elf32_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf32_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
-int process_elf64_file (const char *file_name, const char *lib, int *flag,
-			unsigned int *osversion, char **soname,
+int process_elf64_file (const char *file_name, const char *lib,
+			int *flag, unsigned int *osversion,
+			unsigned int *isa_level, char **soname,
 			void *file_contents, size_t file_length);
 
 /* Returns 0 if everything is ok, != 0 in case of error.  */
 int
 process_elf_file (const char *file_name, const char *lib, int *flag,
-		  unsigned int *osversion, char **soname, void *file_contents,
-		  size_t file_length)
+		  unsigned int *osversion, unsigned int *isa_level,
+		  char **soname, void *file_contents, size_t file_length)
 {
   ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
   int ret, file_flag = 0;
@@ -68,11 +69,11 @@  failed:
     }
 
   if (elf_header->e_ident[EI_CLASS] == ELFCLASS32)
-    ret = process_elf32_file (file_name, lib, flag, osversion, soname,
-			      file_contents, file_length);
+    ret = process_elf32_file (file_name, lib, flag, osversion, isa_level,
+			      soname, file_contents, file_length);
   else
-    ret = process_elf64_file (file_name, lib, flag, osversion, soname,
-			      file_contents, file_length);
+    ret = process_elf64_file (file_name, lib, flag, osversion, isa_level,
+			      soname, file_contents, file_length);
 
   if (!ret && file_flag)
     *flag = file_flag;
diff --git a/sysdeps/unix/sysv/linux/x86_64/Makefile b/sysdeps/unix/sysv/linux/x86_64/Makefile
index 9b82155393..5e19202ebf 100644
--- a/sysdeps/unix/sysv/linux/x86_64/Makefile
+++ b/sysdeps/unix/sysv/linux/x86_64/Makefile
@@ -13,3 +13,54 @@  endif
 ifeq ($(subdir),misc)
 gen-as-const-headers += sigaltstack-offsets.sym
 endif
+
+ifeq ($(subdir),elf)
+ifeq (yes,$(enable-x86-isa-level))
+tests += \
+  tst-glibc-hwcaps-2
+ifeq (no,$(build-hardcoded-path-in-tests))
+# This is an ld.so.cache test, and RPATH/RUNPATH in the executable
+# interferes with its test objectives.
+tests-container += \
+  tst-glibc-hwcaps-2-cache
+endif
+modules-names += \
+  libx86-64-isa-level-1 \
+  libx86-64-isa-level-2 \
+  libx86-64-isa-level-3 \
+  libx86-64-isa-level-4
+
+$(objpfx)tst-glibc-hwcaps-2: $(objpfx)libx86-64-isa-level.so
+
+$(objpfx)tst-glibc-hwcaps-2.out: \
+  $(objpfx)glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so \
+  $(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so \
+  $(objpfx)glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so
+$(objpfx)glibc-hwcaps/x86-64-v2/libx86-64-isa-level.so: \
+  $(objpfx)libx86-64-isa-level-2.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v3/libx86-64-isa-level.so: \
+  $(objpfx)libx86-64-isa-level-3.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/x86-64-v4/libx86-64-isa-level.so: \
+  $(objpfx)libx86-64-isa-level-4.so
+	$(make-target-directory)
+	cp $< $@
+
+CFLAGS-libx86-64-isa-level-1.os += -march=x86-64
+CFLAGS-libx86-64-isa-level-2.os += -march=x86-64
+CFLAGS-libx86-64-isa-level-3.os += -march=x86-64
+CFLAGS-libx86-64-isa-level-4.os += -march=x86-64
+
+# The test modules are parameterized by preprocessor macros.
+LDFLAGS-libx86-64-isa-level-1.so += -Wl,-soname,libx86-64-isa-level.so
+LDFLAGS-libx86-64-isa-level-4.so += -Wl,-soname,libx86-64-isa-level.so
+$(objpfx)libx86-64-isa-level%.os: $(..)/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
+	$(compile-command.c) -DVALUE=$(lastword $(subst -, ,$*)) \
+	  -DISA_LEVEL="(1 << ($(lastword $(subst -, ,$*)) - 1))"
+$(objpfx)libx86-64-isa-level.so: $(objpfx)libx86-64-isa-level-1.so
+	cp $< $@
+endif
+endif # $(subdir) == elf
diff --git a/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
new file mode 100644
index 0000000000..fe91bfd224
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/tst-glibc-hwcaps-2.c
@@ -0,0 +1,84 @@ 
+/* Check ISA level on shared object in glibc-hwcaps subdirectories.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <elf.h>
+#include <get-isa-level.h>
+#include <support/check.h>
+#include <support/test-driver.h>
+
+extern int dso_isa_level (void);
+
+static int
+do_test (void)
+{
+  const struct cpu_features *cpu_features
+    = __x86_get_cpu_features (COMMON_CPUID_INDEX_MAX);
+  unsigned int isa_level = get_isa_level (cpu_features);
+  bool has_isa_baseline = ((isa_level & GNU_PROPERTY_X86_ISA_1_BASELINE)
+			   == GNU_PROPERTY_X86_ISA_1_BASELINE);
+  bool has_isa_v2 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V2)
+			   == GNU_PROPERTY_X86_ISA_1_V2);
+  bool has_isa_v3 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V3)
+			   == GNU_PROPERTY_X86_ISA_1_V3);
+  bool has_isa_v4 = ((isa_level & GNU_PROPERTY_X86_ISA_1_V4)
+			   == GNU_PROPERTY_X86_ISA_1_V4);
+
+  if (!has_isa_baseline)
+    return EXIT_FAILURE;
+
+  int level = dso_isa_level ();
+  int ret;
+  switch (level)
+    {
+    case 1:
+    case 2:
+      /* The default libx86-64-isa-level.so is used.  */
+      printf ("The default shared library is used.\n");
+      if (has_isa_v3 || has_isa_v4 || !has_isa_v2)
+	ret = EXIT_FAILURE;
+      else
+	ret = EXIT_SUCCESS;
+      break;
+    case 3:
+      /* libx86-64-isa-level.so marked as x86-64 ISA level 3 needed in
+	 x86-64-v2 should be ignored on lesser CPU.  */
+      printf ("x86-64 ISA level 3 shared library is used.\n");
+      if (has_isa_v4 || !has_isa_v3)
+	ret = EXIT_FAILURE;
+      else
+	ret = EXIT_SUCCESS;
+      break;
+    case 4:
+      /* libx86-64-isa-level.so marked as x86-64 ISA level 4 needed in
+	 x86-64-v3 should be ignored on lesser CPU.  */
+      printf ("x86-64 ISA level 4 shared library is used.\n");
+      if (has_isa_v4)
+	ret = EXIT_SUCCESS;
+      else
+	ret = EXIT_FAILURE;
+      break;
+    default:
+      abort ();
+    }
+  return ret;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
new file mode 100644
index 0000000000..2813d627cc
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/x86-64-isa-level-VALUE.c
@@ -0,0 +1,4 @@ 
+#define INCLUDE_X86_ISA_LEVEL
+#define MARKER dso_isa_level
+#include <isa-level.c>
+#include <markermodMARKER-VALUE.c>
diff --git a/sysdeps/x86/dl-isa-level.h b/sysdeps/x86/dl-isa-level.h
new file mode 100644
index 0000000000..afe390c365
--- /dev/null
+++ b/sysdeps/x86/dl-isa-level.h
@@ -0,0 +1,31 @@ 
+/* Support for reading ISA level in /etc/ld.so.cache files written by
+   Linux ldconfig.  x86 version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/platform/x86.h>
+
+/* Return true if the ISA level in ENTRY is compatible with CPU.  */
+static inline bool
+dl_cache_hwcap_isa_level_compatible (struct file_entry_new *entry)
+{
+  const struct cpu_features *cpu_features = __get_cpu_features ();
+  unsigned int isa_level
+    = 1 << ((entry->hwcap >> 32) & DL_CACHE_HWCAP_ISA_LEVEL_MASK);
+
+  return (isa_level & cpu_features->isa_1) == isa_level;
+}
-- 
2.29.2