From 72aa81732b3aff00e5bf1f69bb794513b3b37464 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Wed, 5 Jan 2022 19:21:45 -0800 Subject: [PATCH] ld: Add glibc dependency for DT_RELR 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 | 4 +- 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, 155 insertions(+), 1 deletion(-) 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 1613bc74819..107480286f3 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 1b42c6b562a..fc75e9b3625 100644 --- a/ld/ld.texi +++ b/ld/ld.texi @@ -1437,7 +1437,9 @@ 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. @option{nopack-relative-relocs} is the default, which disables compact -relative relocation. Supported for i386 and x86-64. +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" \ + ] \ +] -- 2.30.2