[PATCH v2 1/2] elf: Add elf_backend_add_glibc_version_dependency

["H.J. Lu" <hjl.tools@gmail.com>]

When -z mark-plt is used to add DT_X86_64_PLT, DT_X86_64_PLTSZ and
DT_X86_64_PLTENT, the r_addend field of the R_X86_64_JUMP_SLOT relocation
stores the offset of the indirect branch instruction.  However, glibc
versions which don't have this commit in 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

    According to x86-64 psABI, r_addend should be ignored for R_X86_64_GLOB_DAT
    and R_X86_64_JUMP_SLOT.  Since linkers always set their r_addends to 0, we
    can ignore their r_addends.

    Reviewed-by: Fangrui Song <maskray@google.com>

won't ignore the r_addend value in the R_X86_64_JUMP_SLOT relocation.
Although this commit has been backported to glibc 2.33/2.34/2.35 release
branches, it is safer to require glibc 2.36 for such binaries.

Extend the glibc version dependency of GLIBC_ABI_DT_RELR for DT_RELR to
also add GLIBC_2.36 version dependency for -z mark-plt on the the shared C
library if it provides a GLIBC_2.XX symbol version.

	* elflink.c (elf_find_verdep_info): Moved to ...
	* elf-bfd.h (elf_find_verdep_info): Here.
	(elf_backend_data): Add elf_backend_add_glibc_version_dependency.
	(_bfd_elf_link_add_glibc_version_dependency): New function.
	(_bfd_elf_link_add_dt_relr_dependency): Likewise.
	* elf64-x86-64.c (elf_x86_64_add_glibc_version_dependency):
	Likewise.
	(elf_backend_add_glibc_version_dependency): New.
	* elflink.c (elf_link_add_dt_relr_dependency): Renamed to ...
	(elf_link_add_glibc_verneed): This.  Modified to support other
	glibc dependencies.
	(_bfd_elf_link_add_glibc_version_dependency): Likewise.
	(_bfd_elf_link_add_dt_relr_dependency): Likewise.
	(bfd_elf_size_dynamic_sections): Call
	elf_backend_add_glibc_version_dependency instead of
	elf_link_add_dt_relr_dependency.
	* elfxx-target.h (elf_backend_add_glibc_version_dependency): New.
	(elfNN_bed): Add elf_backend_add_glibc_version_dependency.

ld/

	* testsuite/ld-x86-64/mark-plt-1a.rd: New file.
	* testsuite/ld-x86-64/mark-plt-1b.rd: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run -z mark-plt test for
	GLIBC_2.36 dependency.
---
 bfd/elf-bfd.h                         |  23 ++++
 bfd/elf64-x86-64.c                    |  27 +++++
 bfd/elflink.c                         | 146 +++++++++++++++-----------
 bfd/elfxx-target.h                    |   5 +
 ld/testsuite/ld-x86-64/mark-plt-1a.rd |   7 ++
 ld/testsuite/ld-x86-64/mark-plt-1b.rd |   7 ++
 ld/testsuite/ld-x86-64/x86-64.exp     |  14 +++
 7 files changed, 167 insertions(+), 62 deletions(-)
 create mode 100644 ld/testsuite/ld-x86-64/mark-plt-1a.rd
 create mode 100644 ld/testsuite/ld-x86-64/mark-plt-1b.rd

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index a611349e3d9..3ed22fa6c52 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -957,6 +957,19 @@ typedef struct elf_property_list
   struct elf_property property;
 } elf_property_list;
 
+/* This structure is used to pass information to
+   elf_backend_add_glibc_version_dependency.  */
+
+struct elf_find_verdep_info
+{
+  /* General link information.  */
+  struct bfd_link_info *info;
+  /* The number of dependencies.  */
+  unsigned int vers;
+  /* Whether we had a failure.  */
+  bool failed;
+};
+
 struct bfd_elf_section_reloc_data;
 
 struct elf_backend_data
@@ -1488,6 +1501,10 @@ struct elf_backend_data
   bool (*elf_backend_write_section)
     (bfd *, struct bfd_link_info *, asection *, bfd_byte *);
 
+  /* This function adds glibc version dependency.  */
+  void (*elf_backend_add_glibc_version_dependency)
+    (struct elf_find_verdep_info *);
+
   /* This function, if defined, returns TRUE if it is section symbols
      only that are considered local for the purpose of partitioning the
      symbol table into local and global symbols.  This should be NULL
@@ -2583,6 +2600,12 @@ 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
+  (struct elf_find_verdep_info *, const char *[]);
+
+extern void _bfd_elf_link_add_dt_relr_dependency
+  (struct elf_find_verdep_info *);
+
 extern bool _bfd_elf_adjust_dynamic_copy
   (struct bfd_link_info *, struct elf_link_hash_entry *, asection *);
 
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index ec001599cc1..1a2e64c031f 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -5568,6 +5568,31 @@ elf_x86_64_link_setup_gnu_properties (struct bfd_link_info *info)
   return _bfd_x86_elf_link_setup_gnu_properties (info, &init_table);
 }
 
+static void
+elf_x86_64_add_glibc_version_dependency
+  (struct elf_find_verdep_info *rinfo)
+{
+  unsigned int i = 0;
+  const char *version[3] = { NULL, NULL, NULL };
+  struct elf_x86_link_hash_table *htab;
+
+  if (rinfo->info->enable_dt_relr)
+    {
+      version[i] = "GLIBC_ABI_DT_RELR";
+      i++;
+    }
+
+  htab = elf_x86_hash_table (rinfo->info, X86_64_ELF_DATA);
+  if (htab != NULL && htab->params->mark_plt)
+    {
+      version[i] = "GLIBC_2.36";
+      i++;
+    }
+
+  if (i != 0)
+    _bfd_elf_link_add_glibc_version_dependency (rinfo, version);
+}
+
 static const struct bfd_elf_special_section
 elf_x86_64_special_sections[]=
 {
@@ -5652,6 +5677,8 @@ elf_x86_64_special_sections[]=
   elf_x86_64_link_setup_gnu_properties
 #define elf_backend_hide_symbol \
   _bfd_x86_elf_hide_symbol
+#define elf_backend_add_glibc_version_dependency \
+  elf_x86_64_add_glibc_version_dependency
 
 #undef	elf64_bed
 #define elf64_bed elf64_x86_64_bed
diff --git a/bfd/elflink.c b/bfd/elflink.c
index a577c957514..c2494b3e12e 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -46,19 +46,6 @@ struct elf_info_failed
   bool failed;
 };
 
-/* This structure is used to pass information to
-   _bfd_elf_link_find_version_dependencies.  */
-
-struct elf_find_verdep_info
-{
-  /* General link information.  */
-  struct bfd_link_info *info;
-  /* The number of dependencies.  */
-  unsigned int vers;
-  /* Whether we had a failure.  */
-  bool failed;
-};
-
 static bool _bfd_elf_fix_symbol_flags
   (struct elf_link_hash_entry *, struct elf_info_failed *);
 
@@ -2217,64 +2204,64 @@ _bfd_elf_export_symbol (struct elf_link_hash_entry *h, void *data)
   return true;
 }
 \f
-/* Return true if GLIBC_ABI_DT_RELR is added to the list of version
-   dependencies successfully.  GLIBC_ABI_DT_RELR will be put into the
-   .gnu.version_r section.  */
+/* Return the glibc version reference if VERSION_DEP is added to the
+   list of glibc version dependencies successfully.  VERSION_DEP will
+   be put into the .gnu.version_r section.  */
 
-static bool
-elf_link_add_dt_relr_dependency (struct elf_find_verdep_info *rinfo)
+static Elf_Internal_Verneed *
+elf_link_add_glibc_verneed (struct elf_find_verdep_info *rinfo,
+			    Elf_Internal_Verneed *glibc_verref,
+			    const char *version_dep)
 {
-  bfd *glibc_bfd = NULL;
   Elf_Internal_Verneed *t;
   Elf_Internal_Vernaux *a;
   size_t amt;
-  const char *relr = "GLIBC_ABI_DT_RELR";
 
-  /* See if we already know about GLIBC_PRIVATE_DT_RELR.  */
-  for (t = elf_tdata (rinfo->info->output_bfd)->verref;
-       t != NULL;
-       t = t->vn_nextref)
+  if (glibc_verref != NULL)
     {
-      const char *soname = bfd_elf_get_dt_soname (t->vn_bfd);
-      /* Skip the shared library if it isn't libc.so.  */
-      if (!soname || !startswith (soname, "libc.so."))
-	continue;
+      t = glibc_verref;
 
       for (a = t->vn_auxptr; a != NULL; a = a->vna_nextptr)
 	{
-	  /* Return if GLIBC_PRIVATE_DT_RELR dependency has been
-	     added.  */
-	  if (a->vna_nodename == relr
-	      || strcmp (a->vna_nodename, relr) == 0)
-	    return true;
-
-	  /* Check if libc.so provides GLIBC_2.XX version.  */
-	  if (!glibc_bfd && startswith (a->vna_nodename, "GLIBC_2."))
-	    glibc_bfd = t->vn_bfd;
+	  /* Return if VERSION_DEP dependency has been added.  */
+	  if (a->vna_nodename == version_dep
+	      || strcmp (a->vna_nodename, version_dep) == 0)
+	    return t;
 	}
-
-      break;
     }
+  else
+    {
+      bool is_glibc;
 
-  /* Skip if it isn't linked against glibc.  */
-  if (glibc_bfd == NULL)
-    return true;
+      for (t = elf_tdata (rinfo->info->output_bfd)->verref;
+	   t != NULL;
+	   t = t->vn_nextref)
+	{
+	  const char *soname = bfd_elf_get_dt_soname (t->vn_bfd);
+	  if (soname != NULL && startswith (soname, "libc.so."))
+	    break;
+	}
 
-  /* This is a new version.  Add it to tree we are building.  */
-  if (t == NULL)
-    {
-      amt = sizeof *t;
-      t = (Elf_Internal_Verneed *) bfd_zalloc (rinfo->info->output_bfd,
-					       amt);
+      /* Skip the shared library if it isn't libc.so.  */
       if (t == NULL)
+	return t;
+
+      is_glibc = false;
+      for (a = t->vn_auxptr; a != NULL; a = a->vna_nextptr)
 	{
-	  rinfo->failed = true;
-	  return false;
+	  /* Return if VERSION_DEP dependency has been added.  */
+	  if (a->vna_nodename == version_dep
+	      || strcmp (a->vna_nodename, version_dep) == 0)
+	    return t;
+
+	  /* Check if libc.so provides GLIBC_2.XX version.  */
+	  if (!is_glibc && startswith (a->vna_nodename, "GLIBC_2."))
+	    is_glibc = true;
 	}
 
-      t->vn_bfd = glibc_bfd;
-      t->vn_nextref = elf_tdata (rinfo->info->output_bfd)->verref;
-      elf_tdata (rinfo->info->output_bfd)->verref = t;
+      /* Skip if it isn't linked against glibc.  */
+      if (!is_glibc)
+	return NULL;
     }
 
   amt = sizeof *a;
@@ -2282,10 +2269,10 @@ elf_link_add_dt_relr_dependency (struct elf_find_verdep_info *rinfo)
   if (a == NULL)
     {
       rinfo->failed = true;
-      return false;
+      return NULL;
     }
 
-  a->vna_nodename = relr;
+  a->vna_nodename = version_dep;
   a->vna_flags = 0;
   a->vna_nextptr = t->vn_auxptr;
   a->vna_other = rinfo->vers + 1;
@@ -2293,7 +2280,45 @@ elf_link_add_dt_relr_dependency (struct elf_find_verdep_info *rinfo)
 
   t->vn_auxptr = a;
 
-  return true;
+  return t;
+}
+
+/* Add VERSION_DEP to the list of version dependencies when linked
+   against glibc.  */
+
+void
+_bfd_elf_link_add_glibc_version_dependency
+  (struct elf_find_verdep_info *rinfo,
+   const char *version_dep[])
+{
+  Elf_Internal_Verneed *t = NULL;
+
+  do
+    {
+      t = elf_link_add_glibc_verneed (rinfo, t, *version_dep);
+      /* Return if there is no glibc version reference.  */
+      if (t == NULL)
+	return;
+      version_dep++;
+    }
+  while (*version_dep != NULL);
+}
+
+/* Add GLIBC_ABI_DT_RELR to the list of version dependencies when
+   linked against glibc.  */
+
+void
+_bfd_elf_link_add_dt_relr_dependency (struct elf_find_verdep_info *rinfo)
+{
+  if (rinfo->info->enable_dt_relr)
+    {
+      const char *version[] =
+	{
+	  "GLIBC_ABI_DT_RELR",
+	  NULL
+	};
+      _bfd_elf_link_add_glibc_version_dependency (rinfo, version);
+    }
 }
 
 /* Look through the symbols which are defined in other shared
@@ -7047,12 +7072,9 @@ bfd_elf_size_dynamic_sections (bfd *output_bfd,
       if (sinfo.failed)
 	return false;
 
-      if (info->enable_dt_relr)
-	{
-	  elf_link_add_dt_relr_dependency (&sinfo);
-	  if (sinfo.failed)
-	    return false;
-	}
+      bed->elf_backend_add_glibc_version_dependency (&sinfo);
+      if (sinfo.failed)
+	return false;
 
       if (elf_tdata (output_bfd)->verref == NULL)
 	s->flags |= SEC_EXCLUDE;
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index d4b14a022e3..a7f2fc6e320 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -667,6 +667,10 @@
 #ifndef elf_backend_write_section
 #define elf_backend_write_section		NULL
 #endif
+#ifndef elf_backend_add_glibc_version_dependency
+#define elf_backend_add_glibc_version_dependency \
+  _bfd_elf_link_add_dt_relr_dependency
+#endif
 #ifndef elf_backend_elfsym_local_is_section
 #define elf_backend_elfsym_local_is_section	NULL
 #endif
@@ -897,6 +901,7 @@ static const struct elf_backend_data elfNN_bed =
   elf_backend_can_make_multiple_eh_frame,
   elf_backend_encode_eh_address,
   elf_backend_write_section,
+  elf_backend_add_glibc_version_dependency,
   elf_backend_elfsym_local_is_section,
   elf_backend_mips_irix_compat,
   elf_backend_mips_rtype_to_howto,
diff --git a/ld/testsuite/ld-x86-64/mark-plt-1a.rd b/ld/testsuite/ld-x86-64/mark-plt-1a.rd
new file mode 100644
index 00000000000..1234fbe038c
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mark-plt-1a.rd
@@ -0,0 +1,7 @@
+#...
+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]+
+#pass
diff --git a/ld/testsuite/ld-x86-64/mark-plt-1b.rd b/ld/testsuite/ld-x86-64/mark-plt-1b.rd
new file mode 100644
index 00000000000..6556a6d939e
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mark-plt-1b.rd
@@ -0,0 +1,7 @@
+#...
+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_ABI_DT_RELR  Flags: none  Version: [0-9]+
+#pass
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index 0af9f047600..d17bb9b7d7e 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -2257,4 +2257,18 @@ run_dump_test "mark-plt-1b-x32"
 run_dump_test "mark-plt-1c-x32"
 run_dump_test "mark-plt-1d-x32"
 
+if { [check_compiler_available] } {
+    run_cc_link_tests [list \
+	[list \
+	    "Build mark-plt-1.so" \
+	    "-shared -Wl,-z,mark-plt,-z,pack-relative-relocs" \
+	    "-fPIC" \
+	    { mark-plt-1.s } \
+	    {{readelf {-W --version-info} mark-plt-1a.rd} \
+	     {readelf {-W --version-info} mark-plt-1b.rd}} \
+	    "mark-plt-1.so" \
+	] \
+    ]
+}
+
 set ASFLAGS "$saved_ASFLAGS"
-- 
2.43.0