Patchwork [BZ,#19178] ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA conflict

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Submitter H.J. Lu
Date Oct. 28, 2015, 10:04 p.m.
Message ID <CAMe9rOqtF_9qSfftHHSd22ig7FwsSM_pK_9dOPufHd6zChAjcg@mail.gmail.com>
Download mbox | patch
Permalink /patch/9438/
State New
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Comments

H.J. Lu - Oct. 28, 2015, 10:04 p.m.
On Wed, Oct 28, 2015 at 6:42 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Oct 28, 2015 at 4:49 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> _dl_debug_bindings updates relocation type class with 4 and 8.  But
>> ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA may be defined to 4.  This patch
>> adds ELF_RTYPE_CLASS_TLS/ELF_RTYPE_CLASS_IFUNC and use them in
>> _dl_debug_bindings.
>>
>> Tested on i686 and x86-64.  OK for master and 2.22 branch?
>>
>>
>> H.J.
>> --
>>         [BZ #19178]
>>         * dl-lookup.c (_dl_debug_bindings): Replace 4 and 8 with
>>         ELF_RTYPE_CLASS_TLS and ELF_RTYPE_CLASS_IFUNC.
>>         * sysdeps/generic/ldsodefs.h (ELF_RTYPE_CLASS_TLS): New.
>>         (ELF_RTYPE_CLASS_IFUNC): Likewise.
>
>
> It doesn't work with prelink.
>

Here is the correct patch.  Verified with prelink.  OK for master
and 2.22 branch?

Patch

From 1ed43952877eb3183a8093849e33c8dab0cf7ddf Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 28 Oct 2015 07:49:44 -0700
Subject: [PATCH] Clear ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA for prelink

prelink runs ld.so with the environment variable LD_TRACE_PRELINKING
set to dump the relocation type class from _dl_debug_bindings.  prelink
has the following relocation type classes:

where ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA has a conflict with
RTYPE_CLASS_TLS.

Since prelink doesn't use ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA, we
should clear the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA bit when the
DL_DEBUG_PRELINK bit is set.

	[BZ #19178]
	* elf/dl-lookup.c (RTYPE_CLASS_VALID): New.
	(RTYPE_CLASS_PLT): Likewise.
	(RTYPE_CLASS_COPY): Likewise.
	(RTYPE_CLASS_TLS): Likewise.
	(_dl_debug_bindings): Use RTYPE_CLASS_TLS and RTYPE_CLASS_VALID
	to set relocation type class for DL_DEBUG_PRELINK.  Clear the
	ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA bit for DL_DEBUG_PRELINK.
---
 elf/dl-lookup.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index 581fb20..deb3754 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -1016,6 +1016,18 @@  _dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
 #ifdef SHARED
   if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK)
     {
+/* ELF_RTYPE_CLASS_XXX must match RTYPE_CLASS_XXX used by prelink with
+   LD_TRACE_PRELINKING.  */
+#define RTYPE_CLASS_VALID	8
+#define RTYPE_CLASS_PLT		(8|1)
+#define RTYPE_CLASS_COPY	(8|2)
+#define RTYPE_CLASS_TLS		(8|4)
+#if ELF_RTYPE_CLASS_PLT != 0 && ELF_RTYPE_CLASS_PLT != 1
+# error ELF_RTYPE_CLASS_PLT must be 0 or 1!
+#endif
+#if ELF_RTYPE_CLASS_COPY != 0 && ELF_RTYPE_CLASS_COPY != 2
+# error ELF_RTYPE_CLASS_COPY must be 0 or 2!
+#endif
       int conflict = 0;
       struct sym_val val = { NULL, NULL };
 
@@ -1071,12 +1083,17 @@  _dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
 
       if (value->s)
 	{
+	  /* Clear the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA bit since
+	     it isn't used by prelink.  */
+	  type_class &= ~ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA;
 	  if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
 				== STT_TLS))
-	    type_class = 4;
+	    /* Clear the RTYPE_CLASS_VALID bit in RTYPE_CLASS_TLS.  */
+	    type_class = RTYPE_CLASS_TLS & ~RTYPE_CLASS_VALID;
 	  else if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
 				     == STT_GNU_IFUNC))
-	    type_class |= 8;
+	    /* Set the RTYPE_CLASS_VALID bit.  */
+	    type_class |= RTYPE_CLASS_VALID;
 	}
 
       if (conflict
-- 
2.4.3