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ld: Add glibc dependency for DT_RELR

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When DT_RELR is enabled, to avoid random run-time crash with older glibc
binaries without DT_RELR support, add a GLIBC_ABI_DT_RELR symbol version,
which is provided by glibc with DT_RELR support, dependency on the shared
C library if it provides a GLIBC_2.XX symbol version.

bfd/

	* elflink.c (elf_link_add_dt_relr_dependency): New function.
	(bfd_elf_size_dynamic_sections): Call
	elf_link_add_dt_relr_dependency if DT_RELR is enabled.

ld/

	* ld.texi: Mention GLIBC_ABI_DT_RELR in -z pack-relative-relocs
	entry.
	* testsuite/ld-elf/dt-relr-glibc-1.c: New file.
	* testsuite/ld-elf/dt-relr-glibc-1a.rd: Likewise.
	* testsuite/ld-elf/dt-relr-glibc-1b.rd: Likewise.
	* testsuite/ld-elf/dt-relr.exp: Likewise.
This commit is contained in:
H.J. Lu
2022-01-05 19:21:45 -08:00
parent 4d9e2e53b9
commit 72aa81732b
6 changed files with 155 additions and 1 deletions
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86
bfd/elflink.c
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@@ -2213,6 +2213,85 @@ _bfd_elf_export_symbol (struct elf_link_hash_entry *h, void *data)
return true;
}
/* 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. */
static bool
elf_link_add_dt_relr_dependency (struct elf_find_verdep_info *rinfo)
{
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)
{
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;
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;
}
break;
}
/* Skip if it isn't linked against glibc. */
if (glibc_bfd == NULL)
return true;
/* 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);
if (t == NULL)
{
rinfo->failed = true;
return false;
}
t->vn_bfd = glibc_bfd;
t->vn_nextref = elf_tdata (rinfo->info->output_bfd)->verref;
elf_tdata (rinfo->info->output_bfd)->verref = t;
}
amt = sizeof *a;
a = (Elf_Internal_Vernaux *) bfd_zalloc (rinfo->info->output_bfd, amt);
if (a == NULL)
{
rinfo->failed = true;
return false;
}
a->vna_nodename = relr;
a->vna_flags = 0;
a->vna_nextptr = t->vn_auxptr;
a->vna_other = rinfo->vers + 1;
++rinfo->vers;
t->vn_auxptr = a;
return true;
}
/* Look through the symbols which are defined in other shared
libraries and referenced here. Update the list of version
dependencies. This will be put into the .gnu.version_r section.
@@ -6940,6 +7019,13 @@ 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;
}
if (elf_tdata (output_bfd)->verref == NULL)
s->flags |= SEC_EXCLUDE;
else