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[PATCH 2/3] x86-64: Add GLIBC_ABI_DT_X86_64_PLT version dependency

H.J. Lu hjl.tools@gmail.com
Mon Aug 18 20:13:21 GMT 2025 
On Linux/x86-64, programs and shared libraries created with -z mark-plt
have the GLIBC_2.36 version tag dependency since -z mark-plt uses the
r_addend field of the R_X86_64_JUMP_SLOT relocation to store the offset
of the indirect branch instruction.  Glibc versions which don't have the
commit added to glibc 2.36:

commit f8587a61892cbafd98ce599131bf4f103466f084
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri May 20 19:21:48 2022 -0700

    x86-64: Ignore r_addend for R_X86_64_GLOB_DAT/R_X86_64_JUMP_SLOT

won't ignore the r_addend value in the R_X86_64_JUMP_SLOT relocation.  If
glibc versions defines GLIBC_ABI_DT_X86_64_PLT version tag with

commit 399384e0c8193e31aea014220ccfa24300ae5938
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Aug 14 07:03:20 2025 -0700

    x86-64: Add GLIBC_ABI_DT_X86_64_PLT [BZ #33212]

to indicate inclusion of the commit:

commit f8587a61892cbafd98ce599131bf4f103466f084
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri May 20 19:21:48 2022 -0700

    x86-64: Ignore r_addend for R_X86_64_GLOB_DAT/R_X86_64_JUMP_SLOT

we can add GLIBC_ABI_DT_X86_64_PLT version tag dependency, instead of
GLIBC_2.36 version tag dependency.

	PR ld/33213
	* elf-bfd.h (_bfd_elf_link_add_glibc_version_dependency): Change
	return type to bool.
	* elf64-x86-64.c (elf_x86_64_add_glibc_version_dependency): Add
	GLIBC_ABI_DT_X86_64_PLT version tag dependency, instead of,
	GLIBC_2.36 version tag dependency, for -z mark-plt if libc.so
	defines GLIBC_ABI_DT_X86_64_PLT version tag.
	* elflink.c (_bfd_elf_link_add_glibc_version_dependency): Change
	return type to bool.  Return false if elf_link_add_glibc_verneed
	returns false.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
---
 bfd/elf-bfd.h                         |  2 +-
 bfd/elf64-x86-64.c                    | 24 +++++++++++++++++++-----
 bfd/elflink.c                         |  6 ++++--
 ld/testsuite/ld-x86-64/mark-plt-1a.rd |  2 +-
 4 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index feb470fc477..de7cc410a99 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -2631,7 +2631,7 @@ extern bool _bfd_elf_link_output_relocs
   (bfd *, asection *, Elf_Internal_Shdr *, Elf_Internal_Rela *,
    struct elf_link_hash_entry **);
 
-extern void _bfd_elf_link_add_glibc_version_dependency
+extern bool _bfd_elf_link_add_glibc_version_dependency
   (struct elf_find_verdep_info *, const char *const [], bool *);
 
 extern void _bfd_elf_link_add_dt_relr_dependency
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index edfa608d2d7..31a4b0ce489 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -6246,7 +6246,7 @@ static void
 elf_x86_64_add_glibc_version_dependency
   (struct elf_find_verdep_info *rinfo)
 {
-  unsigned int i = 0;
+  int i = 0, mark_plt = -1;
   const char *version[4] = { NULL, NULL, NULL, NULL };
   bool auto_version[4] = { false, false, false, false };
   struct elf_x86_link_hash_table *htab;
@@ -6271,14 +6271,28 @@ elf_x86_64_add_glibc_version_dependency
 	}
       if (htab->params->mark_plt)
 	{
-	  version[i] = "GLIBC_2.36";
+	  mark_plt = i;
+	  auto_version[i] = true;
+	  version[i] = "GLIBC_ABI_DT_X86_64_PLT";
 	  i++;
 	}
     }
 
-  if (i != 0)
-    _bfd_elf_link_add_glibc_version_dependency (rinfo, version,
-						auto_version);
+  if (i == 0
+      || !_bfd_elf_link_add_glibc_version_dependency (rinfo, version,
+						      auto_version))
+    return;
+
+  if (mark_plt < 0 || auto_version[mark_plt])
+    return;
+
+  /* Add the GLIBC_2.36 version dependency if libc.so doesn't have
+     GLIBC_ABI_DT_X86_64_PLT.  */
+  version[0] = "GLIBC_2.36";
+  auto_version[0] = false;
+  version[1] = NULL;
+  _bfd_elf_link_add_glibc_version_dependency (rinfo, version,
+					      auto_version);
 }
 
 static const struct bfd_elf_special_section
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ac40423751f..98759a3dec6 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -2401,7 +2401,7 @@ elf_link_add_glibc_verneed (struct elf_find_verdep_info *rinfo,
 /* Add VERSION_DEP to the list of version dependencies when linked
    against glibc.  */
 
-void
+bool
 _bfd_elf_link_add_glibc_version_dependency
   (struct elf_find_verdep_info *rinfo,
    const char *const version_dep[],
@@ -2414,11 +2414,13 @@ _bfd_elf_link_add_glibc_version_dependency
       /* Return if not linked against glibc.  */
       if (!elf_link_add_glibc_verneed (rinfo, *version_dep,
 				       &glibc_minor_base, auto_version))
-	return;
+	return false;
       version_dep++;
       auto_version++;
     }
   while (*version_dep != NULL);
+
+  return true;
 }
 
 /* Add GLIBC_ABI_DT_RELR to the list of version dependencies when
diff --git a/ld/testsuite/ld-x86-64/mark-plt-1a.rd b/ld/testsuite/ld-x86-64/mark-plt-1a.rd
index 1234fbe038c..b0ed7024420 100644
--- a/ld/testsuite/ld-x86-64/mark-plt-1a.rd
+++ b/ld/testsuite/ld-x86-64/mark-plt-1a.rd
@@ -3,5 +3,5 @@ Version needs section '.gnu.version_r' contains 1 entry:
  Addr: 0x[0-9a-f]+ +Offset: 0x[0-9a-f]+ +Link: +[0-9]+ +\(.dynstr\)
  +0+: Version: 1 +File: libc\.so\.6(|\.1) +Cnt: +[0-9]+
 #...
-  0x[a-f0-9]+:   Name: GLIBC_2.36  Flags: none  Version: [0-9]+
+  0x[a-f0-9]+:   Name: (GLIBC_2.36|GLIBC_ABI_DT_X86_64_PLT)  Flags: none  Version: [0-9]+
 #pass
-- 
2.50.1
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