[09/11] elf: Add glibc-hwcaps subdirectory support to ld.so cache processing
Commit Message
This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
the supported cache entry with the highest priority.
---
elf/Makefile | 18 ++
elf/dl-cache.c | 182 +++++++++++++++++-
elf/dl-hwcaps.c | 78 ++++++++
elf/dl-hwcaps.h | 19 ++
elf/tst-glibc-hwcaps-cache.c | 45 +++++
.../etc/ld.so.conf | 2 +
elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
elf/tst-glibc-hwcaps-cache.script | 2 +
elf/tst-glibc-hwcaps-prepend-cache.c | 133 +++++++++++++
.../postclean.req | 0
10 files changed, 476 insertions(+), 3 deletions(-)
create mode 100644 elf/tst-glibc-hwcaps-cache.c
create mode 100644 elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
create mode 100644 elf/tst-glibc-hwcaps-cache.root/postclean.req
create mode 100644 elf/tst-glibc-hwcaps-cache.script
create mode 100644 elf/tst-glibc-hwcaps-prepend-cache.c
create mode 100644 elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
Comments
* Florian Weimer via Libc-alpha:
> diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
> new file mode 100644
> index 0000000000..46cb5fd553
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-cache.script
> @@ -0,0 +1,2 @@
> +# test-container does not support scripts in sysdeps directories, so
> +# collect everything in one file.
This file is missing installation of the default libraries, like this:
cp $B/elf/libmarkermod2-1.so $L/libmarkermod2.so
cp $B/elf/libmarkermod3-1.so $L/libmarkermod3.so
cp $B/elf/libmarkermod4-1.so $L/libmarkermod4.so
Thanks,
Florian
On 09/11/2020 15:41, Florian Weimer via Libc-alpha wrote:
> This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
> the supported cache entry with the highest priority.
Maybe add a brief description of what DL_CACHE_HWCAP_EXTENSION aims to do?
Patch looks good in general, some comments below.
> ---
> elf/Makefile | 18 ++
> elf/dl-cache.c | 182 +++++++++++++++++-
> elf/dl-hwcaps.c | 78 ++++++++
> elf/dl-hwcaps.h | 19 ++
> elf/tst-glibc-hwcaps-cache.c | 45 +++++
> .../etc/ld.so.conf | 2 +
> elf/tst-glibc-hwcaps-cache.root/postclean.req | 0
> elf/tst-glibc-hwcaps-cache.script | 2 +
> elf/tst-glibc-hwcaps-prepend-cache.c | 133 +++++++++++++
> .../postclean.req | 0
> 10 files changed, 476 insertions(+), 3 deletions(-)
> create mode 100644 elf/tst-glibc-hwcaps-cache.c
> create mode 100644 elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
> create mode 100644 elf/tst-glibc-hwcaps-cache.root/postclean.req
> create mode 100644 elf/tst-glibc-hwcaps-cache.script
> create mode 100644 elf/tst-glibc-hwcaps-prepend-cache.c
> create mode 100644 elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
>
> diff --git a/elf/Makefile b/elf/Makefile
> index e26ac16b44..80e94b9ee2 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -171,6 +171,12 @@ tests-container := \
> tst-ldconfig-bad-aux-cache \
> tst-ldconfig-ld_so_conf-update
>
> +ifeq (no,$(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-prepend-cache
> +endif
> +
> tests := tst-tls9 tst-leaks1 \
> tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
> tst-auxv tst-stringtable
Ok.
> @@ -1859,6 +1865,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
> $< > $@; \
> $(evaluate-test)
>
> +# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
> +# library via ld.so.cache. Test setup is contained in the test
> +# itself.
> +$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
> +$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
> + $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
> + $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
> +
> # tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
> # suppress all auto-detected subdirectories.
> $(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
> @@ -1870,3 +1884,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
> --glibc-hwcaps-mask does-not-exist \
> $< > $@; \
> $(evaluate-test)
> +
> +# Generic dependency for sysdeps implementation of
> +# tst-glibc-hwcaps-cache.
> +$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
Ok.
> diff --git a/elf/dl-cache.c b/elf/dl-cache.c
> index 02c46ffb0c..13efc6f95f 100644
> --- a/elf/dl-cache.c
> +++ b/elf/dl-cache.c
> @@ -35,6 +35,132 @@ static struct cache_file *cache;
> static struct cache_file_new *cache_new;
> static size_t cachesize;
>
> +#ifdef SHARED
> +/* This is used to cache the priorities of glibc-hwcaps
> + subdirectories. The elements of _dl_cache_priorities correspond to
> + the strings in the cache_extension_tag_glibc_hwcaps section. */
> +static uint32_t *glibc_hwcaps_priorities;
> +static uint32_t glibc_hwcaps_priorities_length;
> +static uint32_t glibc_hwcaps_priorities_allocated;
> +
> +/* True if the full malloc was used to allocated the array. */
> +static bool glibc_hwcaps_priorities_malloced;
> +
> +/* Deallocate the glibc_hwcaps_priorities array. */
> +static void
> +glibc_hwcaps_priorities_free (void)
> +{
> + /* When the minimal malloc is in use, free does not do anything,
> + so it does not make sense to call it. */
> + if (glibc_hwcaps_priorities_malloced)
> + free (glibc_hwcaps_priorities);
> + glibc_hwcaps_priorities = NULL;
> + glibc_hwcaps_priorities_allocated = 0;
> +}
> +
> +/* Return the priority of the cache_extension_tag_glibc_hwcaps section
> + entry at INDEX. Zero means do not use. Otherwise, lower values
> + indicate greater preference. */
> +static uint32_t __attribute__ ((noinline, noclone))
I have a feeling I have asked it before, but why does it need noclone/noinline
here?
> +glibc_hwcaps_priority (uint32_t index)
> +{
> + /* Using a zero-length array as an indicator that nothing has been
> + loaded is not a problem: It does not lead to repeated
> + initialization attempts because caches without an extension
> + section are processed without calling this function (unless the
> + file is corrupted). */
> + if (glibc_hwcaps_priorities_length == 0)
Maybe an early exit here? It allow move the code one identation left
and makes it more readable.
> + {
> + struct cache_extension_all_loaded ext;
> + if (!cache_extension_load (cache_new, cache, cachesize, &ext))
> + return 0;
> +
> + uint32_t length
> + = (ext.sections[cache_extension_tag_glibc_hwcaps].size
> + / sizeof (uint32_t));
> + if (length > glibc_hwcaps_priorities_allocated)
> + {
> + glibc_hwcaps_priorities_free ();
> +
> + glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
> + if (glibc_hwcaps_priorities == NULL)
> + /* Disable hwcaps on memory allocation error. */
> + return 0;
> +
> + glibc_hwcaps_priorities_allocated = length;
> + glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
> + }
> +
> + /* Compute the priorities for the subdirectories by merging the
> + array in the cache with the dl_hwcaps_priorities array. */
> + const uint32_t *left
> + = ext.sections[cache_extension_tag_glibc_hwcaps].base;
> + const uint32_t *left_end = left + length;
> + struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
> + struct dl_hwcaps_priority *right_end
> + = right + _dl_hwcaps_priorities_length;
> + uint32_t *result = glibc_hwcaps_priorities;
> +
> + while (left < left_end && right < right_end)
> + {
> + uint32_t string_table_index = *left;
> + if (string_table_index < cachesize)
> + {
> + const char *left_name
> + = (const char *) cache + string_table_index;
> + uint32_t left_name_length = strlen (left_name);
> + uint32_t to_compare;
> + if (left_name_length < right->name_length)
> + to_compare = left_name_length;
> + else
> + to_compare = right->name_length;
> + int cmp = memcmp (left_name, right->name, to_compare);
> + if (cmp == 0)
> + {
> + if (left_name_length < right->name_length)
> + cmp = -1;
> + else if (left_name_length > right->name_length)
> + cmp = 1;
> + }
> + if (cmp == 0)
> + {
> + *result = right->priority;
> + ++result;
> + ++left;
> + ++right;
> + }
Maybe add as the 'else' within the 'cmp == 0' below?
> + else if (cmp < 0)
> + {
> + *result = 0;
> + ++result;
> + ++left;
> + }
> + else
> + ++right;
> + }
> + else
> + {
> + *result = 0;
> + ++result;
> + }
> + }
> + while (left < left_end)
> + {
> + *result = 0;
> + ++result;
> + ++left;
> + }
> +
> + glibc_hwcaps_priorities_length = length;
> + }
> +
> + if (index < glibc_hwcaps_priorities_length)
> + return glibc_hwcaps_priorities[index];
> + else
> + return 0;
> +}
> +#endif /* SHARED */
> +
Ok.
> /* True if PTR is a valid string table index. */
> static inline bool
> _dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
> @@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
> int left = 0;
> int right = nlibs - 1;
> const char *best = NULL;
> +#ifdef SHARED
> + uint32_t best_priority = 0;
> +#endif
>
> while (left <= right)
> {
> @@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
> {
> if (best == NULL || flags == GLRO (dl_correct_cache_id))
> {
> + /* Named/extension hwcaps get slightly different
> + treatment: We keep searching for a better
> + match. */
> + bool named_hwcap = false;
> +
> if (entry_size >= sizeof (struct file_entry_new))
> {
> /* The entry is large enough to include
Ok.
> @@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
> struct file_entry_new *libnew
> = (struct file_entry_new *) lib;
>
> - if (libnew->hwcap & hwcap_exclude)
> +#ifdef SHARED
> + named_hwcap = dl_cache_hwcap_extension (libnew);
> +#endif
> +
> + /* The entries with named/extension hwcaps
> + have been exhausted. Return the best
> + match encountered so far if there is
> + one. */
> + if (!named_hwcap && best != NULL)
> + break;
> +
> + if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
> continue;
> if (GLRO (dl_osversion)
> && libnew->osversion > GLRO (dl_osversion))
Ok.
> @@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
> && ((libnew->hwcap & _DL_HWCAP_PLATFORM)
> != platform))
> continue;
> +
> +#ifdef SHARED
> + /* For named hwcaps, determine the priority
> + and see if beats what has been found so
> + far. */
> + if (named_hwcap)
> + {
> + uint32_t entry_priority
> + = glibc_hwcaps_priority (libnew->hwcap);
> + if (entry_priority == 0)
> + /* Not usable at all. Skip. */
> + continue;
> + else if (best == NULL
> + || entry_priority < best_priority)
> + /* This entry is of higher priority
> + than the previous one, or it is the
> + first entry. */
> + best_priority = entry_priority;
> + else
> + /* An entry has already been found,
> + but it is a better match. */
> + continue;
> + }
> +#endif /* SHARED */
> }
Ok.
>
> best = string_table + lib->value;
>
> - if (flags == GLRO (dl_correct_cache_id))
> + if (flags == GLRO (dl_correct_cache_id)
> + && !named_hwcap)
> /* We've found an exact match for the shared
> object and no general `ELF' release. Stop
> - searching. */
> + searching, but not if a named (extension)
> + hwcap is used. In this case, an entry with
> + a higher priority may come up later. */
> break;
> }
> }
Ok.
> @@ -346,5 +518,9 @@ _dl_unload_cache (void)
> __munmap (cache, cachesize);
> cache = NULL;
> }
> +#ifdef SHARED
> + /* This marks the glibc_hwcaps_priorities array as out-of-date. */
> + glibc_hwcaps_priorities_length = 0;
> +#endif
> }
> #endif
Ok.
> diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
> index f611f3a1a6..51cc787b54 100644
> --- a/elf/dl-hwcaps.c
> +++ b/elf/dl-hwcaps.c
> @@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
> }
> }
>
> +struct dl_hwcaps_priority *_dl_hwcaps_priorities;
> +uint32_t _dl_hwcaps_priorities_length;
> +
> +/* Allocate _dl_hwcaps_priorities and fill it with data. */
> +static void
> +compute_priorities (size_t total_count, const char *prepend,
> + int32_t bitmask, const char *mask)
I think bitmask should be a 'uint32' here.
> +{
> + _dl_hwcaps_priorities = malloc (total_count
> + * sizeof (*_dl_hwcaps_priorities));
> + if (_dl_hwcaps_priorities == NULL)
> + _dl_signal_error (ENOMEM, NULL, NULL,
> + N_("cannot create HWCAP priorities"));
> + _dl_hwcaps_priorities_length = total_count;
> +
> + /* First the prepended subdirectories. */
> + size_t i = 0;
> + {
> + struct dl_hwcaps_split sp;
> + _dl_hwcaps_split_init (&sp, prepend);
> + while (_dl_hwcaps_split (&sp))
> + {
> + _dl_hwcaps_priorities[i].name = sp.segment;
> + _dl_hwcaps_priorities[i].name_length = sp.length;
> + _dl_hwcaps_priorities[i].priority = i + 1;
> + ++i;
> + }
> + }
> +
Ok.
> + /* Then the built-in subdirectories that are actually active. */
> + {
> + struct dl_hwcaps_split_masked sp;
> + _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
> + while (_dl_hwcaps_split_masked (&sp))
> + {
> + _dl_hwcaps_priorities[i].name = sp.split.segment;
> + _dl_hwcaps_priorities[i].name_length = sp.split.length;
> + _dl_hwcaps_priorities[i].priority = i + 1;
> + ++i;
> + }
> + }
> + assert (i == total_count);
> +}
> +
Ok.
> +/* Sort the _dl_hwcaps_priorities array by name. */
> +static void
> +sort_priorities_by_name (void)
> +{
> + /* Insertion sort. There is no need to link qsort into the dynamic
> + loader for such a short array. */
> + for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
> + for (size_t j = i; j > 0; --j)
> + {
> + struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
> + struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
> +
> + /* Bail out if current is greater or equal to the previous
> + value. */
> + uint32_t to_compare;
> + if (current->name_length < previous->name_length)
> + to_compare = current->name_length;
> + else
> + to_compare = previous->name_length;
> + int cmp = memcmp (current->name, previous->name, to_compare);
> + if (cmp >= 0
> + || (cmp == 0 && current->name_length >= previous->name_length))
> + break;
> +
> + /* Swap *previous and *current. */
> + struct dl_hwcaps_priority tmp = *previous;
> + *previous = *current;
> + *current = tmp;
> + }
> +}
> +
Ok.
> /* Return an array of useful/necessary hardware capability names. */
> const struct r_strlenpair *
> _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
> @@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
> update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
> update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
> hwcaps_subdirs_active, glibc_hwcaps_mask);
> + compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
> + hwcaps_subdirs_active, glibc_hwcaps_mask);
> + sort_priorities_by_name ();
>
> /* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
> and a "/" suffix once stored in the result. */
Ok.
> diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
> index ab39d8a46d..ddfdde278e 100644
> --- a/elf/dl-hwcaps.h
> +++ b/elf/dl-hwcaps.h
> @@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
> return mask ^ ((1U << inactive) - 1);
> }
>
> +/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
> + dl-cache.c to quickly find the proprities for the stored HWCAP
> + names. */
> +struct dl_hwcaps_priority
> +{
> + /* The name consists of name_length bytes at name (not necessarily
> + null-terminated). */
> + const char *name;
> + uint32_t name_length;
> +
> + /* Priority of this name. A positive number. */
> + uint32_t priority;
> +};
> +
> +/* Pre-computed hwcaps priorities. Set up by
> + _dl_important_hwcaps. */
> +extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
> +extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
> +
> #endif /* _DL_HWCAPS_H */
Ok.
> diff --git a/elf/tst-glibc-hwcaps-cache.c b/elf/tst-glibc-hwcaps-cache.c
> new file mode 100644
> index 0000000000..4bad56afc0
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-cache.c
> @@ -0,0 +1,45 @@
> +/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
> + 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. 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);
> + }
> +
> + /* 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", support_objdir_root);
> + execv (path, argv);
> + printf ("error: execv of %s failed: %m\n", path);
> + return 1;
> +}
Ok, it should be simple enough to require use libsupport fork/timeout check.
> diff --git a/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf b/elf/tst-glibc-hwcaps-cache.root/etc/ld.so.conf
> new file mode 100644
> index 0000000000..e1e74dbda2
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-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-cache.root/postclean.req b/elf/tst-glibc-hwcaps-cache.root/postclean.req
> new file mode 100644
> index 0000000000..e69de29bb2
Ok.
> diff --git a/elf/tst-glibc-hwcaps-cache.script b/elf/tst-glibc-hwcaps-cache.script
> new file mode 100644
> index 0000000000..46cb5fd553
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-cache.script
> @@ -0,0 +1,2 @@
> +# test-container does not support scripts in sysdeps directories, so
> +# collect everything in one file.
Ok.
> diff --git a/elf/tst-glibc-hwcaps-prepend-cache.c b/elf/tst-glibc-hwcaps-prepend-cache.c
> new file mode 100644
> index 0000000000..eedbf5f6df
> --- /dev/null
> +++ b/elf/tst-glibc-hwcaps-prepend-cache.c
> @@ -0,0 +1,133 @@
> +/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
> + 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 <dlfcn.h>
> +#include <stddef.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/xdlfcn.h>
> +#include <support/xunistd.h>
> +
> +/* Invoke /sbin/ldconfig with some error checking. */
> +static void
> +run_ldconfig (void)
> +{
> + char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
> + TEST_COMPARE (system (command), 0);
> + free (command);
> +}
> +
> +/* The library under test. */
> +#define SONAME "libmarkermod1.so"
> +
> +static int
> +do_test (void)
> +{
> + if (dlopen (SONAME, RTLD_NOW) != NULL)
> + FAIL_EXIT1 (SONAME " is already on the search path");
> +
> + /* Install the default implementation of libmarkermod1.so. */
> + xmkdirp ("/etc", 0777);
> + support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
> + xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
> + xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
> + {
> + char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
> + support_copy_file (src, "/glibc-test/lib/" SONAME);
> + free (src);
> + }
Ok.
> + run_ldconfig ();
> + {
> + /* The default implementation can now be loaded. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 1);
> + xdlclose (handle);
> + }
Ok.
> +
> + /* Add the first override to the directory that is searched last. */
> + {
> + char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
> + support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
> + SONAME);
> + free (src);
> + }
> + {
> + /* This is still the first implementation. The cache has not been
> + updated. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 1);
> + xdlclose (handle);
> + }
Ok.
> + run_ldconfig ();
> + {
> + /* After running ldconfig, it is the second implementation. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 2);
> + xdlclose (handle);
> + }
> +
Ok.
> + /* Add the second override to the directory that is searched first. */
> + {
> + char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
> + support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
> + SONAME);
> + free (src);
> + }
> + {
> + /* This is still the second implementation. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 2);
> + xdlclose (handle);
> + }
Ok.
> + run_ldconfig ();
> + {
> + /* After running ldconfig, it is the third implementation. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 3);
> + xdlclose (handle);
> + }
> +
Ok.
Should we test the case of shared memory removal, for instance:
1. Remove second override, without ldconfig
2. Remove third override, run ldconfig
3. Add both second and third back, run ldconfig, remove third
4. Keep second, run ldconfig
> + return 0;
> +}
> +
> +static void
> +prepare (int argc, char **argv)
> +{
> + const char *no_restart = "no-restart";
> + if (argc == 2 && strcmp (argv[1], no_restart) == 0)
> + return;
> + /* Re-execute the test with an explicit loader invocation. */
> + execl (support_objdir_elf_ldso,
> + support_objdir_elf_ldso,
> + "--glibc-hwcaps-prepend", "prepend3:prepend2",
> + argv[0], no_restart,
> + NULL);
> + printf ("error: execv of %s failed: %m\n", argv[0]);
> + _exit (1);
> +}
> +
> +#define PREPARE prepare
> +#include <support/test-driver.c>
> diff --git a/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req b/elf/tst-glibc-hwcaps-prepend-cache.root/postclean.req
> new file mode 100644
> index 0000000000..e69de29bb2
>
Ok.
* Adhemerval Zanella via Libc-alpha:
> On 09/11/2020 15:41, Florian Weimer via Libc-alpha wrote:
>> This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
>> the supported cache entry with the highest priority.
>
> Maybe add a brief description of what DL_CACHE_HWCAP_EXTENSION aims to
> do?
It's documented in sysdeps/generic/dl-cache.h, added in the previous
commit:
/* 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 the priority of the cache_extension_tag_glibc_hwcaps section
>> + entry at INDEX. Zero means do not use. Otherwise, lower values
>> + indicate greater preference. */
>> +static uint32_t __attribute__ ((noinline, noclone))
>> +glibc_hwcaps_priority (uint32_t index)
>
> I have a feeling I have asked it before, but why does it need noclone/noinline
> here?
I don't recall such a discussion. It's a leftover from previous
debugging efforts.
>> +{
>> + /* Using a zero-length array as an indicator that nothing has been
>> + loaded is not a problem: It does not lead to repeated
>> + initialization attempts because caches without an extension
>> + section are processed without calling this function (unless the
>> + file is corrupted). */
>> + if (glibc_hwcaps_priorities_length == 0)
>
> Maybe an early exit here? It allow move the code one identation left
> and makes it more readable.
I've moved this into a separate initialization function.
>> + while (left < left_end && right < right_end)
>> + {
>> + uint32_t string_table_index = *left;
>> + if (string_table_index < cachesize)
>> + {
>> + const char *left_name
>> + = (const char *) cache + string_table_index;
>> + uint32_t left_name_length = strlen (left_name);
>> + uint32_t to_compare;
>> + if (left_name_length < right->name_length)
>> + to_compare = left_name_length;
>> + else
>> + to_compare = right->name_length;
>> + int cmp = memcmp (left_name, right->name, to_compare);
>> + if (cmp == 0)
>> + {
>> + if (left_name_length < right->name_length)
>> + cmp = -1;
>> + else if (left_name_length > right->name_length)
>> + cmp = 1;
>> + }
>> + if (cmp == 0)
>> + {
>> + *result = right->priority;
>> + ++result;
>> + ++left;
>> + ++right;
>> + }
>
> Maybe add as the 'else' within the 'cmp == 0' below?
>
>> + else if (cmp < 0)
>> + {
>> + *result = 0;
>> + ++result;
>> + ++left;
>> + }
>> + else
>> + ++right;
You mean like this?
if (cmp == 0)
{
*result = right->priority;
++result;
++left;
}
if (cmp < 0)
{
*result = 0;
++result;
++left;
}
if (cmp >= 0)
++right;
I don't think that's an improvement.
>> +struct dl_hwcaps_priority *_dl_hwcaps_priorities;
>> +uint32_t _dl_hwcaps_priorities_length;
>> +
>> +/* Allocate _dl_hwcaps_priorities and fill it with data. */
>> +static void
>> +compute_priorities (size_t total_count, const char *prepend,
>> + int32_t bitmask, const char *mask)
>
> I think bitmask should be a 'uint32' here.
Right, fixed.
>> +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);
>> + }
>> +
>> + /* 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", support_objdir_root);
>> + execv (path, argv);
>> + printf ("error: execv of %s failed: %m\n", path);
>> + return 1;
>> +}
>
> Ok, it should be simple enough to require use libsupport fork/timeout
> check.
Yes, we run ldconfig without timeout elsewhere, and tst-glibc-hwcaps has
its own timeout check.
> Should we test the case of shared memory removal, for instance:
>
> 1. Remove second override, without ldconfig
> 2. Remove third override, run ldconfig
> 3. Add both second and third back, run ldconfig, remove third
> 4. Keep second, run ldconfig
I added this:
+ /* Remove the second override again, without running ldconfig.
+ Ideally, this would revert to implementation 2. However, in the
+ current implementation, the cache returns exactly one file name
+ which does not exist after unlinking, so the dlopen fails. */
+ xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME);
+ TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL);
+ run_ldconfig ();
+ system("/sbin/ldconfig -p");
+ {
+ /* After running ldconfig, the second implementation is available
+ once more. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
I think I know what I have to do to fix this in elf/dl-load.c.
I feel this is a pre-existing issue. It also applies to the legacy
hwcaps subdirectories. This only happens for ld.so.cache bringing in
libraries from a non-searched directory, otherwise the LD_LIBRARY_PATH
processing will find an implementation if it exists. I'd like to fix it
in a follow-up patch.
Thanks,
Florian
On 01/12/2020 17:45, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
>
>> On 09/11/2020 15:41, Florian Weimer via Libc-alpha wrote:
>>> This recognizes the DL_CACHE_HWCAP_EXTENSION flag and picks up
>>> the supported cache entry with the highest priority.
>>
>> Maybe add a brief description of what DL_CACHE_HWCAP_EXTENSION aims to
>> do?
>
> It's documented in sysdeps/generic/dl-cache.h, added in the previous
> commit:
>
> /* 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)
I meant to commit message, but I don't have a strong opinion about it.
>
>>> +/* Return the priority of the cache_extension_tag_glibc_hwcaps section
>>> + entry at INDEX. Zero means do not use. Otherwise, lower values
>>> + indicate greater preference. */
>>> +static uint32_t __attribute__ ((noinline, noclone))
>>> +glibc_hwcaps_priority (uint32_t index)
>>
>> I have a feeling I have asked it before, but why does it need noclone/noinline
>> here?
>
> I don't recall such a discussion. It's a leftover from previous
> debugging efforts.
Ack.
>
>>> +{
>>> + /* Using a zero-length array as an indicator that nothing has been
>>> + loaded is not a problem: It does not lead to repeated
>>> + initialization attempts because caches without an extension
>>> + section are processed without calling this function (unless the
>>> + file is corrupted). */
>>> + if (glibc_hwcaps_priorities_length == 0)
>>
>> Maybe an early exit here? It allow move the code one identation left
>> and makes it more readable.
>
> I've moved this into a separate initialization function.
Ack.
>
>>> + while (left < left_end && right < right_end)
>>> + {
>>> + uint32_t string_table_index = *left;
>>> + if (string_table_index < cachesize)
>>> + {
>>> + const char *left_name
>>> + = (const char *) cache + string_table_index;
>>> + uint32_t left_name_length = strlen (left_name);
>>> + uint32_t to_compare;
>>> + if (left_name_length < right->name_length)
>>> + to_compare = left_name_length;
>>> + else
>>> + to_compare = right->name_length;
>>> + int cmp = memcmp (left_name, right->name, to_compare);
>>> + if (cmp == 0)
>>> + {
>>> + if (left_name_length < right->name_length)
>>> + cmp = -1;
>>> + else if (left_name_length > right->name_length)
>>> + cmp = 1;
>>> + }
>>> + if (cmp == 0)
>>> + {
>>> + *result = right->priority;
>>> + ++result;
>>> + ++left;
>>> + ++right;
>>> + }
>>
>> Maybe add as the 'else' within the 'cmp == 0' below?
>>
>>> + else if (cmp < 0)
>>> + {
>>> + *result = 0;
>>> + ++result;
>>> + ++left;
>>> + }
>>> + else
>>> + ++right;
>
> You mean like this?
>
> if (cmp == 0)
> {
> *result = right->priority;
> ++result;
> ++left;
> }
> if (cmp < 0)
> {
> *result = 0;
> ++result;
> ++left;
> }
> if (cmp >= 0)
> ++right;
The v5 seems more readable in fact.
>
> I don't think that's an improvement.
>
>>> +struct dl_hwcaps_priority *_dl_hwcaps_priorities;
>>> +uint32_t _dl_hwcaps_priorities_length;
>>> +
>>> +/* Allocate _dl_hwcaps_priorities and fill it with data. */
>>> +static void
>>> +compute_priorities (size_t total_count, const char *prepend,
>>> + int32_t bitmask, const char *mask)
>>
>> I think bitmask should be a 'uint32' here.
>
> Right, fixed.
>
>>> +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);
>>> + }
>>> +
>>> + /* 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", support_objdir_root);
>>> + execv (path, argv);
>>> + printf ("error: execv of %s failed: %m\n", path);
>>> + return 1;
>>> +}
>>
>> Ok, it should be simple enough to require use libsupport fork/timeout
>> check.
>
> Yes, we run ldconfig without timeout elsewhere, and tst-glibc-hwcaps has
> its own timeout check.
>
>> Should we test the case of shared memory removal, for instance:
>>
>> 1. Remove second override, without ldconfig
>> 2. Remove third override, run ldconfig
>> 3. Add both second and third back, run ldconfig, remove third
>> 4. Keep second, run ldconfig
>
> I added this:
>
> + /* Remove the second override again, without running ldconfig.
> + Ideally, this would revert to implementation 2. However, in the
> + current implementation, the cache returns exactly one file name
> + which does not exist after unlinking, so the dlopen fails. */
> + xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME);
> + TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL);
> + run_ldconfig ();
> + system("/sbin/ldconfig -p");
I think this might a leftover of debugging.
> + {
> + /* After running ldconfig, the second implementation is available
> + once more. */
> + void *handle = xdlopen (SONAME, RTLD_NOW);
> + int (*marker1) (void) = xdlsym (handle, "marker1");
> + TEST_COMPARE (marker1 (), 2);
> + xdlclose (handle);
> + }
>
> I think I know what I have to do to fix this in elf/dl-load.c.
>
> I feel this is a pre-existing issue. It also applies to the legacy
> hwcaps subdirectories. This only happens for ld.so.cache bringing in
> libraries from a non-searched directory, otherwise the LD_LIBRARY_PATH
> processing will find an implementation if it exists. I'd like to fix it
> in a follow-up patch.
Fair enough.
* Adhemerval Zanella via Libc-alpha:
>> + /* Remove the second override again, without running ldconfig.
>> + Ideally, this would revert to implementation 2. However, in the
>> + current implementation, the cache returns exactly one file name
>> + which does not exist after unlinking, so the dlopen fails. */
>> + xunlink ("/glibc-test/lib/glibc-hwcaps/prepend3/" SONAME);
>> + TEST_VERIFY (dlopen (SONAME, RTLD_NOW) == NULL);
>> + run_ldconfig ();
>> + system("/sbin/ldconfig -p");
>
> I think this might a leftover of debugging.
Thanks, I've removed the ldconfig -p invocation.
Florian
@@ -171,6 +171,12 @@ tests-container := \
tst-ldconfig-bad-aux-cache \
tst-ldconfig-ld_so_conf-update
+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-prepend-cache
+endif
+
tests := tst-tls9 tst-leaks1 \
tst-array1 tst-array2 tst-array3 tst-array4 tst-array5 \
tst-auxv tst-stringtable
@@ -1859,6 +1865,14 @@ $(objpfx)tst-glibc-hwcaps-prepend.out: \
$< > $@; \
$(evaluate-test)
+# Like tst-glibc-hwcaps-prepend, but uses a container and loads the
+# library via ld.so.cache. Test setup is contained in the test
+# itself.
+$(objpfx)tst-glibc-hwcaps-prepend-cache: $(libdl)
+$(objpfx)tst-glibc-hwcaps-prepend-cache.out: \
+ $(objpfx)tst-glibc-hwcaps-prepend-cache $(objpfx)libmarkermod1-1.so \
+ $(objpfx)libmarkermod1-2.so $(objpfx)libmarkermod1-3.so
+
# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
# suppress all auto-detected subdirectories.
$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
@@ -1870,3 +1884,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
--glibc-hwcaps-mask does-not-exist \
$< > $@; \
$(evaluate-test)
+
+# Generic dependency for sysdeps implementation of
+# tst-glibc-hwcaps-cache.
+$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
@@ -35,6 +35,132 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
+#ifdef SHARED
+/* This is used to cache the priorities of glibc-hwcaps
+ subdirectories. The elements of _dl_cache_priorities correspond to
+ the strings in the cache_extension_tag_glibc_hwcaps section. */
+static uint32_t *glibc_hwcaps_priorities;
+static uint32_t glibc_hwcaps_priorities_length;
+static uint32_t glibc_hwcaps_priorities_allocated;
+
+/* True if the full malloc was used to allocated the array. */
+static bool glibc_hwcaps_priorities_malloced;
+
+/* Deallocate the glibc_hwcaps_priorities array. */
+static void
+glibc_hwcaps_priorities_free (void)
+{
+ /* When the minimal malloc is in use, free does not do anything,
+ so it does not make sense to call it. */
+ if (glibc_hwcaps_priorities_malloced)
+ free (glibc_hwcaps_priorities);
+ glibc_hwcaps_priorities = NULL;
+ glibc_hwcaps_priorities_allocated = 0;
+}
+
+/* Return the priority of the cache_extension_tag_glibc_hwcaps section
+ entry at INDEX. Zero means do not use. Otherwise, lower values
+ indicate greater preference. */
+static uint32_t __attribute__ ((noinline, noclone))
+glibc_hwcaps_priority (uint32_t index)
+{
+ /* Using a zero-length array as an indicator that nothing has been
+ loaded is not a problem: It does not lead to repeated
+ initialization attempts because caches without an extension
+ section are processed without calling this function (unless the
+ file is corrupted). */
+ if (glibc_hwcaps_priorities_length == 0)
+ {
+ struct cache_extension_all_loaded ext;
+ if (!cache_extension_load (cache_new, cache, cachesize, &ext))
+ return 0;
+
+ uint32_t length
+ = (ext.sections[cache_extension_tag_glibc_hwcaps].size
+ / sizeof (uint32_t));
+ if (length > glibc_hwcaps_priorities_allocated)
+ {
+ glibc_hwcaps_priorities_free ();
+
+ glibc_hwcaps_priorities = malloc (length * sizeof (uint32_t));
+ if (glibc_hwcaps_priorities == NULL)
+ /* Disable hwcaps on memory allocation error. */
+ return 0;
+
+ glibc_hwcaps_priorities_allocated = length;
+ glibc_hwcaps_priorities_malloced = __rtld_malloc_is_complete ();
+ }
+
+ /* Compute the priorities for the subdirectories by merging the
+ array in the cache with the dl_hwcaps_priorities array. */
+ const uint32_t *left
+ = ext.sections[cache_extension_tag_glibc_hwcaps].base;
+ const uint32_t *left_end = left + length;
+ struct dl_hwcaps_priority *right = _dl_hwcaps_priorities;
+ struct dl_hwcaps_priority *right_end
+ = right + _dl_hwcaps_priorities_length;
+ uint32_t *result = glibc_hwcaps_priorities;
+
+ while (left < left_end && right < right_end)
+ {
+ uint32_t string_table_index = *left;
+ if (string_table_index < cachesize)
+ {
+ const char *left_name
+ = (const char *) cache + string_table_index;
+ uint32_t left_name_length = strlen (left_name);
+ uint32_t to_compare;
+ if (left_name_length < right->name_length)
+ to_compare = left_name_length;
+ else
+ to_compare = right->name_length;
+ int cmp = memcmp (left_name, right->name, to_compare);
+ if (cmp == 0)
+ {
+ if (left_name_length < right->name_length)
+ cmp = -1;
+ else if (left_name_length > right->name_length)
+ cmp = 1;
+ }
+ if (cmp == 0)
+ {
+ *result = right->priority;
+ ++result;
+ ++left;
+ ++right;
+ }
+ else if (cmp < 0)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+ else
+ ++right;
+ }
+ else
+ {
+ *result = 0;
+ ++result;
+ }
+ }
+ while (left < left_end)
+ {
+ *result = 0;
+ ++result;
+ ++left;
+ }
+
+ glibc_hwcaps_priorities_length = length;
+ }
+
+ if (index < glibc_hwcaps_priorities_length)
+ return glibc_hwcaps_priorities[index];
+ else
+ return 0;
+}
+#endif /* SHARED */
+
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
@@ -74,6 +200,9 @@ search_cache (const char *string_table, uint32_t string_table_size,
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
+#ifdef SHARED
+ uint32_t best_priority = 0;
+#endif
while (left <= right)
{
@@ -129,6 +258,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
+ /* Named/extension hwcaps get slightly different
+ treatment: We keep searching for a better
+ match. */
+ bool named_hwcap = false;
+
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
@@ -136,7 +270,18 @@ search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
- if (libnew->hwcap & hwcap_exclude)
+#ifdef SHARED
+ named_hwcap = dl_cache_hwcap_extension (libnew);
+#endif
+
+ /* The entries with named/extension hwcaps
+ have been exhausted. Return the best
+ match encountered so far if there is
+ one. */
+ if (!named_hwcap && best != NULL)
+ break;
+
+ if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
@@ -146,14 +291,41 @@ search_cache (const char *string_table, uint32_t string_table_size,
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
+
+#ifdef SHARED
+ /* For named hwcaps, determine the priority
+ and see if beats what has been found so
+ far. */
+ if (named_hwcap)
+ {
+ uint32_t entry_priority
+ = glibc_hwcaps_priority (libnew->hwcap);
+ if (entry_priority == 0)
+ /* Not usable at all. Skip. */
+ continue;
+ else if (best == NULL
+ || entry_priority < best_priority)
+ /* This entry is of higher priority
+ than the previous one, or it is the
+ first entry. */
+ best_priority = entry_priority;
+ else
+ /* An entry has already been found,
+ but it is a better match. */
+ continue;
+ }
+#endif /* SHARED */
}
best = string_table + lib->value;
- if (flags == GLRO (dl_correct_cache_id))
+ if (flags == GLRO (dl_correct_cache_id)
+ && !named_hwcap)
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
- searching. */
+ searching, but not if a named (extension)
+ hwcap is used. In this case, an entry with
+ a higher priority may come up later. */
break;
}
}
@@ -346,5 +518,9 @@ _dl_unload_cache (void)
__munmap (cache, cachesize);
cache = NULL;
}
+#ifdef SHARED
+ /* This marks the glibc_hwcaps_priorities array as out-of-date. */
+ glibc_hwcaps_priorities_length = 0;
+#endif
}
#endif
@@ -89,6 +89,81 @@ copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
}
}
+struct dl_hwcaps_priority *_dl_hwcaps_priorities;
+uint32_t _dl_hwcaps_priorities_length;
+
+/* Allocate _dl_hwcaps_priorities and fill it with data. */
+static void
+compute_priorities (size_t total_count, const char *prepend,
+ int32_t bitmask, const char *mask)
+{
+ _dl_hwcaps_priorities = malloc (total_count
+ * sizeof (*_dl_hwcaps_priorities));
+ if (_dl_hwcaps_priorities == NULL)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ N_("cannot create HWCAP priorities"));
+ _dl_hwcaps_priorities_length = total_count;
+
+ /* First the prepended subdirectories. */
+ size_t i = 0;
+ {
+ struct dl_hwcaps_split sp;
+ _dl_hwcaps_split_init (&sp, prepend);
+ while (_dl_hwcaps_split (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+
+ /* Then the built-in subdirectories that are actually active. */
+ {
+ struct dl_hwcaps_split_masked sp;
+ _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
+ while (_dl_hwcaps_split_masked (&sp))
+ {
+ _dl_hwcaps_priorities[i].name = sp.split.segment;
+ _dl_hwcaps_priorities[i].name_length = sp.split.length;
+ _dl_hwcaps_priorities[i].priority = i + 1;
+ ++i;
+ }
+ }
+ assert (i == total_count);
+}
+
+/* Sort the _dl_hwcaps_priorities array by name. */
+static void
+sort_priorities_by_name (void)
+{
+ /* Insertion sort. There is no need to link qsort into the dynamic
+ loader for such a short array. */
+ for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
+ for (size_t j = i; j > 0; --j)
+ {
+ struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
+ struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
+
+ /* Bail out if current is greater or equal to the previous
+ value. */
+ uint32_t to_compare;
+ if (current->name_length < previous->name_length)
+ to_compare = current->name_length;
+ else
+ to_compare = previous->name_length;
+ int cmp = memcmp (current->name, previous->name, to_compare);
+ if (cmp >= 0
+ || (cmp == 0 && current->name_length >= previous->name_length))
+ break;
+
+ /* Swap *previous and *current. */
+ struct dl_hwcaps_priority tmp = *previous;
+ *previous = *current;
+ *current = tmp;
+ }
+}
+
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
@@ -111,6 +186,9 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
hwcaps_subdirs_active, glibc_hwcaps_mask);
+ compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
+ hwcaps_subdirs_active, glibc_hwcaps_mask);
+ sort_priorities_by_name ();
/* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
and a "/" suffix once stored in the result. */
@@ -132,4 +132,23 @@ _dl_hwcaps_subdirs_build_bitmask (int subdirs, int active)
return mask ^ ((1U << inactive) - 1);
}
+/* Pre-computed glibc-hwcaps subdirectory priorities. Used in
+ dl-cache.c to quickly find the proprities for the stored HWCAP
+ names. */
+struct dl_hwcaps_priority
+{
+ /* The name consists of name_length bytes at name (not necessarily
+ null-terminated). */
+ const char *name;
+ uint32_t name_length;
+
+ /* Priority of this name. A positive number. */
+ uint32_t priority;
+};
+
+/* Pre-computed hwcaps priorities. Set up by
+ _dl_important_hwcaps. */
+extern struct dl_hwcaps_priority *_dl_hwcaps_priorities attribute_hidden;
+extern uint32_t _dl_hwcaps_priorities_length attribute_hidden;
+
#endif /* _DL_HWCAPS_H */
new file mode 100644
@@ -0,0 +1,45 @@
+/* Wrapper to invoke tst-glibc-hwcaps in a container, to test ld.so.cache.
+ 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. 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);
+ }
+
+ /* 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", support_objdir_root);
+ execv (path, argv);
+ printf ("error: execv of %s failed: %m\n", path);
+ return 1;
+}
new file mode 100644
@@ -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
new file mode 100644
new file mode 100644
@@ -0,0 +1,2 @@
+# test-container does not support scripts in sysdeps directories, so
+# collect everything in one file.
new file mode 100644
@@ -0,0 +1,133 @@
+/* Test that --glibc-hwcaps-prepend works, using dlopen and /etc/ld.so.cache.
+ 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 <dlfcn.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xunistd.h>
+
+/* Invoke /sbin/ldconfig with some error checking. */
+static void
+run_ldconfig (void)
+{
+ char *command = xasprintf ("%s/ldconfig", support_install_rootsbindir);
+ TEST_COMPARE (system (command), 0);
+ free (command);
+}
+
+/* The library under test. */
+#define SONAME "libmarkermod1.so"
+
+static int
+do_test (void)
+{
+ if (dlopen (SONAME, RTLD_NOW) != NULL)
+ FAIL_EXIT1 (SONAME " is already on the search path");
+
+ /* Install the default implementation of libmarkermod1.so. */
+ xmkdirp ("/etc", 0777);
+ support_write_file_string ("/etc/ld.so.conf", "/glibc-test/lib\n");
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend2", 0777);
+ xmkdirp ("/glibc-test/lib/glibc-hwcaps/prepend3", 0777);
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-1.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/" SONAME);
+ free (src);
+ }
+ run_ldconfig ();
+ {
+ /* The default implementation can now be loaded. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+
+ /* Add the first override to the directory that is searched last. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-2.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend2/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the first implementation. The cache has not been
+ updated. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 1);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+
+ /* Add the second override to the directory that is searched first. */
+ {
+ char *src = xasprintf ("%s/elf/libmarkermod1-3.so", support_objdir_root);
+ support_copy_file (src, "/glibc-test/lib/glibc-hwcaps/prepend3/"
+ SONAME);
+ free (src);
+ }
+ {
+ /* This is still the second implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 2);
+ xdlclose (handle);
+ }
+ run_ldconfig ();
+ {
+ /* After running ldconfig, it is the third implementation. */
+ void *handle = xdlopen (SONAME, RTLD_NOW);
+ int (*marker1) (void) = xdlsym (handle, "marker1");
+ TEST_COMPARE (marker1 (), 3);
+ xdlclose (handle);
+ }
+
+ return 0;
+}
+
+static void
+prepare (int argc, char **argv)
+{
+ const char *no_restart = "no-restart";
+ if (argc == 2 && strcmp (argv[1], no_restart) == 0)
+ return;
+ /* Re-execute the test with an explicit loader invocation. */
+ execl (support_objdir_elf_ldso,
+ support_objdir_elf_ldso,
+ "--glibc-hwcaps-prepend", "prepend3:prepend2",
+ argv[0], no_restart,
+ NULL);
+ printf ("error: execv of %s failed: %m\n", argv[0]);
+ _exit (1);
+}
+
+#define PREPARE prepare
+#include <support/test-driver.c>
new file mode 100644