[PATCH v2 9/9] ld: Add glibc dependency for DT_RELR
H.J. Lu
hjl.tools@gmail.com
Sat Jan 8 18:38:38 GMT 2022
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.
---
bfd/elflink.c | 86 +++++++++++++++++++++++++
ld/ld.texi | 6 +-
ld/testsuite/ld-elf/dt-relr-glibc-1.c | 11 ++++
ld/testsuite/ld-elf/dt-relr-glibc-1a.rd | 4 ++
ld/testsuite/ld-elf/dt-relr-glibc-1b.rd | 7 ++
ld/testsuite/ld-elf/dt-relr.exp | 44 +++++++++++++
6 files changed, 156 insertions(+), 2 deletions(-)
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1.c
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1a.rd
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1b.rd
create mode 100644 ld/testsuite/ld-elf/dt-relr.exp
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 31b13f5df7a..05ac1cb7a63 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -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
diff --git a/ld/ld.texi b/ld/ld.texi
index 36113723c9b..bf26f8cd3bf 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -1438,8 +1438,10 @@ and shared library. It adds @code{DT_RELR}, @code{DT_RELRSZ} and
@code{DT_RELRENT} entries to the dynamic section. It is ignored when
building position-dependent executable and relocatable output. This
option also implies @option{combreloc}. @option{nopack-relative-relocs}
-is the default, which disables compact relative relocation. Supported
-for i386 and x86-64.
+is the default, which disables compact relative relocation. When linked
+against the GNU C Library, a GLIBC_ABI_DT_RELR symbol version dependency
+on the shared C Library is added to the output. Supported for i386 and
+x86-64.
@item relro
@itemx norelro
diff --git a/ld/testsuite/ld-elf/dt-relr-glibc-1.c b/ld/testsuite/ld-elf/dt-relr-glibc-1.c
new file mode 100644
index 00000000000..beacffe29e7
--- /dev/null
+++ b/ld/testsuite/ld-elf/dt-relr-glibc-1.c
@@ -0,0 +1,11 @@
+#define REL(n) \
+ static int data##n; \
+ void *p##n = &data##n;
+
+REL(1)
+REL(2)
+REL(3)
+REL(4)
+REL(5)
+REL(6)
+REL(7)
diff --git a/ld/testsuite/ld-elf/dt-relr-glibc-1a.rd b/ld/testsuite/ld-elf/dt-relr-glibc-1a.rd
new file mode 100644
index 00000000000..51bda5d70a1
--- /dev/null
+++ b/ld/testsuite/ld-elf/dt-relr-glibc-1a.rd
@@ -0,0 +1,4 @@
+#failif
+#...
+ 0x[a-f0-9]+: Name: GLIBC_ABI_DT_RELR Flags: none Version: [0-9]+
+#...
diff --git a/ld/testsuite/ld-elf/dt-relr-glibc-1b.rd b/ld/testsuite/ld-elf/dt-relr-glibc-1b.rd
new file mode 100644
index 00000000000..6556a6d939e
--- /dev/null
+++ b/ld/testsuite/ld-elf/dt-relr-glibc-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-elf/dt-relr.exp b/ld/testsuite/ld-elf/dt-relr.exp
new file mode 100644
index 00000000000..51d21e400ab
--- /dev/null
+++ b/ld/testsuite/ld-elf/dt-relr.exp
@@ -0,0 +1,44 @@
+# Expect script for DT_RELR.
+# Copyright (C) 2022 Free Software Foundation, Inc.
+#
+# This file is part of the GNU Binutils.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+#
+
+# Linux tests.
+if { ![istarget "*-*-linux*"] } {
+ return
+}
+
+run_cc_link_tests [list \
+ [list \
+ "Build dt-relr-glibc-1a.so" \
+ "-shared $NO_DT_RELR_CC_LDFLAGS" \
+ "-fPIC" \
+ { dt-relr-glibc-1.c } \
+ {{readelf {--version-info} dt-relr-glibc-1a.rd}} \
+ "glibc-relr-1a.so" \
+ ] \
+ [list \
+ "Build dt-relr-glibc-1b.so" \
+ "-shared $DT_RELR_CC_LDFLAGS" \
+ "-fPIC" \
+ { dt-relr-glibc-1.c } \
+ {{readelf {-W --version-info} dt-relr-glibc-1b.rd}} \
+ "dt-relr-glibc-1b.so" \
+ ] \
+]
--
2.33.1
More information about the Binutils
mailing list