diff mbox series

elf: Fix elf_get_dynamic_info() for bootstrap

Message ID 20211015174123.2305597-1-adhemerval.zanella@linaro.org
State Committed
Commit 5118dcac68c4eadfd6304bb33adde63d062dc07f
Headers
Series elf: Fix elf_get_dynamic_info() for bootstrap |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent
dj/TryBot-32bit success Build for i686

Commit Message

Adhemerval Zanella Netto Oct. 15, 2021, 5:41 p.m. UTC 
  THe d6d89608ac8c broke powerpc for --enable-bind-now because it turned
out that different than patch assumption rtld elf_get_dynamic_info()
does require to handle RTLD_BOOTSTRAP to avoid DT_FLAGS and
DT_RUNPATH (more specially the GLRO usage which is not reallocate
yet).

This patch fixes by passing two arguments to elf_get_dynamic_info()
to inform that by rtld (bootstrap) or static pie initialization
(static_pie_bootstrap).  I think using explicit argument is way more
clear and burried C preprocessor, and compiler should remove the
dead code.

I checked on x86_64 and i686 with default options, --enable-bind-now,
and --enable-bind-now and --enable--static-pie.  I also check on
aarch64, armhf, powerpc64, and powerpc with default and
--enable-bind-now.
---
 elf/dl-load.c             |  2 +-
 elf/dl-reloc-static-pie.c |  3 +-
 elf/get-dynamic-info.h    | 95 +++++++++++++++++++++++----------------
 elf/rtld.c                |  4 +-
 elf/setup-vdso.h          |  2 +-
 5 files changed, 61 insertions(+), 45 deletions(-)

Comments

Adhemerval Zanella Netto Oct. 15, 2021, 5:42 p.m. UTC | #1 
On 15/10/2021 14:41, Adhemerval Zanella wrote:
> THe d6d89608ac8c broke powerpc for --enable-bind-now because it turned
> out that different than patch assumption rtld elf_get_dynamic_info()
> does require to handle RTLD_BOOTSTRAP to avoid DT_FLAGS and
> DT_RUNPATH (more specially the GLRO usage which is not reallocate
> yet).
> 
> This patch fixes by passing two arguments to elf_get_dynamic_info()
> to inform that by rtld (bootstrap) or static pie initialization
> (static_pie_bootstrap).  I think using explicit argument is way more
> clear and burried C preprocessor, and compiler should remove the
> dead code.
> 
> I checked on x86_64 and i686 with default options, --enable-bind-now,
> and --enable-bind-now and --enable--static-pie.  I also check on
> aarch64, armhf, powerpc64, and powerpc with default and
> --enable-bind-now.

Manuel and Szabolcs,

If you could check if this breaks something in your environment I would
be grateful. I really want to fix this nasty regression...
Manuel Lauss Oct. 15, 2021, 6:49 p.m. UTC | #2 
On Fri, Oct 15, 2021 at 7:42 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
[...]
> Manuel and Szabolcs,
>
> If you could check if this breaks something in your environment I would
> be grateful. I really want to fix this nasty regression...

I've tested this on i386, x64 and mips32elsf, all without issues.

Manuel
Szabolcs Nagy Oct. 18, 2021, 12:46 p.m. UTC | #3 
The 10/15/2021 14:42, Adhemerval Zanella wrote:
> 
> 
> On 15/10/2021 14:41, Adhemerval Zanella wrote:
> > THe d6d89608ac8c broke powerpc for --enable-bind-now because it turned
> > out that different than patch assumption rtld elf_get_dynamic_info()
> > does require to handle RTLD_BOOTSTRAP to avoid DT_FLAGS and
> > DT_RUNPATH (more specially the GLRO usage which is not reallocate
> > yet).
> > 
> > This patch fixes by passing two arguments to elf_get_dynamic_info()
> > to inform that by rtld (bootstrap) or static pie initialization
> > (static_pie_bootstrap).  I think using explicit argument is way more
> > clear and burried C preprocessor, and compiler should remove the
> > dead code.
> > 
> > I checked on x86_64 and i686 with default options, --enable-bind-now,
> > and --enable-bind-now and --enable--static-pie.  I also check on
> > aarch64, armhf, powerpc64, and powerpc with default and
> > --enable-bind-now.
> 
> Manuel and Szabolcs,
> 
> If you could check if this breaks something in your environment I would
> be grateful. I really want to fix this nasty regression...

the patch works for me too.
Adhemerval Zanella Netto Oct. 18, 2021, 12:49 p.m. UTC | #4 
On 18/10/2021 09:46, Szabolcs Nagy wrote:
> The 10/15/2021 14:42, Adhemerval Zanella wrote:
>>
>>
>> On 15/10/2021 14:41, Adhemerval Zanella wrote:
>>> THe d6d89608ac8c broke powerpc for --enable-bind-now because it turned
>>> out that different than patch assumption rtld elf_get_dynamic_info()
>>> does require to handle RTLD_BOOTSTRAP to avoid DT_FLAGS and
>>> DT_RUNPATH (more specially the GLRO usage which is not reallocate
>>> yet).
>>>
>>> This patch fixes by passing two arguments to elf_get_dynamic_info()
>>> to inform that by rtld (bootstrap) or static pie initialization
>>> (static_pie_bootstrap).  I think using explicit argument is way more
>>> clear and burried C preprocessor, and compiler should remove the
>>> dead code.
>>>
>>> I checked on x86_64 and i686 with default options, --enable-bind-now,
>>> and --enable-bind-now and --enable--static-pie.  I also check on
>>> aarch64, armhf, powerpc64, and powerpc with default and
>>> --enable-bind-now.
>>
>> Manuel and Szabolcs,
>>
>> If you could check if this breaks something in your environment I would
>> be grateful. I really want to fix this nasty regression...
> 
> the patch works for me too.
> 

Thanks, I will commit this shortly and check if something breaks. I hope
this will be the last one to wrap this up.
diff mbox series

Patch

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 18d3e8fe64..a1f1682188 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1298,7 +1298,7 @@  _dl_map_object_from_fd (const char *name, const char *origname, int fd,
   else
     l->l_ld = (ElfW(Dyn) *) ((ElfW(Addr)) l->l_ld + l->l_addr);
 
-  elf_get_dynamic_info (l);
+  elf_get_dynamic_info (l, false, false);
 
   /* Make sure we are not dlopen'ing an object that has the
      DF_1_NOOPEN flag set, or a PIE object.  */
diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
index 40a031f2e9..5b85df8a2e 100644
--- a/elf/dl-reloc-static-pie.c
+++ b/elf/dl-reloc-static-pie.c
@@ -25,7 +25,6 @@ 
 
 #include <dl-machine.h>
 
-#define STATIC_PIE_BOOTSTRAP
 #define RESOLVE_MAP(map, scope, sym, version, flags) map
 #include "dynamic-link.h"
 #include "get-dynamic-info.h"
@@ -52,7 +51,7 @@  _dl_relocate_static_pie (void)
 	break;
       }
 
-  elf_get_dynamic_info (main_map);
+  elf_get_dynamic_info (main_map, false, true);
 
 # ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
   ELF_MACHINE_BEFORE_RTLD_RELOC (main_map, main_map->l_info);
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index 1ac0663d1f..f63e07dc6d 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -26,7 +26,8 @@ 
 #include <libc-diag.h>
 
 static inline void __attribute__ ((unused, always_inline))
-elf_get_dynamic_info (struct link_map *l)
+elf_get_dynamic_info (struct link_map *l, bool bootstrap,
+		      bool static_pie_bootstrap)
 {
 #if __ELF_NATIVE_CLASS == 32
   typedef Elf32_Word d_tag_utype;
@@ -35,7 +36,7 @@  elf_get_dynamic_info (struct link_map *l)
 #endif
 
 #ifndef STATIC_PIE_BOOTSTRAP
-  if (l->l_ld == NULL)
+  if (!bootstrap && l->l_ld == NULL)
     return;
 #endif
 
@@ -112,47 +113,63 @@  elf_get_dynamic_info (struct link_map *l)
   if (info[DT_REL] != NULL)
     assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
 #endif
-#ifdef STATIC_PIE_BOOTSTRAP
-  assert (info[DT_RUNPATH] == NULL);
-  assert (info[DT_RPATH] == NULL);
-#endif
-  if (info[DT_FLAGS] != NULL)
+  if (bootstrap || static_pie_bootstrap)
     {
-      /* Flags are used.  Translate to the old form where available.
-	 Since these l_info entries are only tested for NULL pointers it
-	 is ok if they point to the DT_FLAGS entry.  */
-      l->l_flags = info[DT_FLAGS]->d_un.d_val;
-
-      if (l->l_flags & DF_SYMBOLIC)
-	info[DT_SYMBOLIC] = info[DT_FLAGS];
-      if (l->l_flags & DF_TEXTREL)
-	info[DT_TEXTREL] = info[DT_FLAGS];
-      if (l->l_flags & DF_BIND_NOW)
-	info[DT_BIND_NOW] = info[DT_FLAGS];
+      assert (info[DT_RUNPATH] == NULL);
+      assert (info[DT_RPATH] == NULL);
     }
-  if (info[VERSYMIDX (DT_FLAGS_1)] != NULL)
+  if (bootstrap)
     {
-      l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
-      if (l->l_flags_1 & DF_1_NODELETE)
-	l->l_nodelete_pending = true;
-
-      /* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
-	 to assert this, but we can't. Users have been setting
-	 unsupported DF_1_* flags for a long time and glibc has ignored
-	 them. Therefore to avoid breaking existing applications the
-	 best we can do is add a warning during debugging with the
-	 intent of notifying the user of the problem.  */
-      if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)
-	  && l->l_flags_1 & ~DT_1_SUPPORTED_MASK)
-	_dl_debug_printf ("\nWARNING: Unsupported flag value(s) of 0x%x in DT_FLAGS_1.\n",
-			  l->l_flags_1 & ~DT_1_SUPPORTED_MASK);
-
-      if (l->l_flags_1 & DF_1_NOW)
-	info[DT_BIND_NOW] = info[VERSYMIDX (DT_FLAGS_1)];
+      /* Only the bind now flags are allowed.  */
+      assert (info[VERSYMIDX (DT_FLAGS_1)] == NULL
+	      || (info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val & ~DF_1_NOW) == 0);
+      /* Flags must not be set for ld.so.  */
+      assert (info[DT_FLAGS] == NULL
+	      || (info[DT_FLAGS]->d_un.d_val & ~DF_BIND_NOW) == 0);
     }
-  if (info[DT_RUNPATH] != NULL)
-    /* If both RUNPATH and RPATH are given, the latter is ignored.  */
-    info[DT_RPATH] = NULL;
+  else
+    {
+      if (info[DT_FLAGS] != NULL)
+	{
+	  /* Flags are used.  Translate to the old form where available.
+	     Since these l_info entries are only tested for NULL pointers it
+	     is ok if they point to the DT_FLAGS entry.  */
+	  l->l_flags = info[DT_FLAGS]->d_un.d_val;
+
+	  if (l->l_flags & DF_SYMBOLIC)
+	    info[DT_SYMBOLIC] = info[DT_FLAGS];
+	  if (l->l_flags & DF_TEXTREL)
+	    info[DT_TEXTREL] = info[DT_FLAGS];
+	  if (l->l_flags & DF_BIND_NOW)
+	    info[DT_BIND_NOW] = info[DT_FLAGS];
+	}
+
+      if (info[VERSYMIDX (DT_FLAGS_1)] != NULL)
+	{
+	  l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
+	  if (l->l_flags_1 & DF_1_NODELETE)
+	    l->l_nodelete_pending = true;
+
+	  /* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
+	     to assert this, but we can't. Users have been setting
+	     unsupported DF_1_* flags for a long time and glibc has ignored
+	     them. Therefore to avoid breaking existing applications the
+	     best we can do is add a warning during debugging with the
+	     intent of notifying the user of the problem.  */
+	  if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)
+	      && l->l_flags_1 & ~DT_1_SUPPORTED_MASK)
+	    _dl_debug_printf ("\nWARNING: Unsupported flag value(s) of 0x%x "
+			      "in DT_FLAGS_1.\n",
+			     l->l_flags_1 & ~DT_1_SUPPORTED_MASK);
+
+	 if (l->l_flags_1 & DF_1_NOW)
+	   info[DT_BIND_NOW] = info[VERSYMIDX (DT_FLAGS_1)];
+       }
+
+    if (info[DT_RUNPATH] != NULL)
+      /* If both RUNPATH and RPATH are given, the latter is ignored.  */
+      info[DT_RPATH] = NULL;
+   }
 }
 
 #endif
diff --git a/elf/rtld.c b/elf/rtld.c
index 6cfb7cf672..c66a1d00bc 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -547,7 +547,7 @@  _dl_start (void *arg)
 
   /* Read our own dynamic section and fill in the info array.  */
   bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + elf_machine_dynamic ();
-  elf_get_dynamic_info (&bootstrap_map);
+  elf_get_dynamic_info (&bootstrap_map, true, false);
 
 #if NO_TLS_OFFSET != 0
   bootstrap_map.l_tls_offset = NO_TLS_OFFSET;
@@ -1615,7 +1615,7 @@  dl_main (const ElfW(Phdr) *phdr,
   if (! rtld_is_main)
     {
       /* Extract the contents of the dynamic section for easy access.  */
-      elf_get_dynamic_info (main_map);
+      elf_get_dynamic_info (main_map, false, false);
 
       /* If the main map is libc.so, update the base namespace to
 	 refer to this map.  If libc.so is loaded later, this happens
diff --git a/elf/setup-vdso.h b/elf/setup-vdso.h
index f44748bc98..3f20578046 100644
--- a/elf/setup-vdso.h
+++ b/elf/setup-vdso.h
@@ -64,7 +64,7 @@  setup_vdso (struct link_map *main_map __attribute__ ((unused)),
       l->l_map_end += l->l_addr;
       l->l_text_end += l->l_addr;
       l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr);
-      elf_get_dynamic_info (l);
+      elf_get_dynamic_info (l, false, false);
       _dl_setup_hash (l);
       l->l_relocated = 1;