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authorAlan Modra <amodra@gmail.com>2016-12-26 00:30:45 +1030
committerAlan Modra <amodra@gmail.com>2016-12-26 13:47:51 +1030
commit5474d94f03aedba2f832006dc7d680cc15792a7b (patch)
tree8fdd2bb1d2a32f1f35ef76199f9d92da95c0ec27 /bfd/elf32-tic6x.c
parent9d19e4fdb7c684329c8b1b72796a0071708dabc7 (diff)
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dynrelro section for read-only dynamic symbols copied into executable
Variables defined in shared libraries are copied into an executable's .bss section when code in the executable is non-PIC and thus would require dynamic text relocations to access the variable directly in the shared library. Recent x86 toolchains also copy variables into the executable to gain a small speed improvement. The problem is that if the variable was originally read-only, the copy in .bss is writable, potentially opening a security hole. This patch cures that problem by putting the copy in a section that becomes read-only after ld.so relocation, provided -z relro is in force. The patch also fixes a microblaze linker segfault on attempting to use dynamic bss variables. bfd/ PR ld/20995 * elf-bfd.h (struct elf_link_hash_table): Add sdynrelro and sreldynrelro. (struct elf_backend_data): Add want_dynrelro. * elfxx-target.h (elf_backend_want_dynrelro): Define. (elfNN_bed): Update initializer. * elflink.c (_bfd_elf_create_dynamic_sections): Create sdynrelro and sreldynrelro sections. * elf32-arm.c (elf32_arm_adjust_dynamic_symbol): Place variables copied into the executable from read-only sections into sdynrelro. (elf32_arm_size_dynamic_sections): Handle sdynrelro. (elf32_arm_finish_dynamic_symbol): Select sreldynrelro for dynamic relocs in sdynrelro. (elf_backend_want_dynrelro): Define. * elf32-hppa.c (elf32_hppa_adjust_dynamic_symbol) (elf32_hppa_size_dynamic_sections, elf32_hppa_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-i386.c (elf_i386_adjust_dynamic_symbol) (elf_i386_size_dynamic_sections, elf_i386_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-metag.c (elf_metag_adjust_dynamic_symbol) (elf_metag_size_dynamic_sections, elf_metag_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-microblaze.c (microblaze_elf_adjust_dynamic_symbol) (microblaze_elf_size_dynamic_sections) (microblaze_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-nios2.c (nios2_elf32_finish_dynamic_symbol) (nios2_elf32_adjust_dynamic_symbol) (nios2_elf32_size_dynamic_sections) (elf_backend_want_dynrelro): As above. * elf32-or1k.c (or1k_elf_finish_dynamic_symbol) (or1k_elf_adjust_dynamic_symbol, or1k_elf_size_dynamic_sections) (elf_backend_want_dynrelro): As above. * elf32-ppc.c (ppc_elf_adjust_dynamic_symbol) (ppc_elf_size_dynamic_sections, ppc_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-s390.c (elf_s390_adjust_dynamic_symbol) (elf_s390_size_dynamic_sections, elf_s390_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-tic6x.c (elf32_tic6x_adjust_dynamic_symbol) (elf32_tic6x_size_dynamic_sections) (elf32_tic6x_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-tilepro.c (tilepro_elf_adjust_dynamic_symbol) (tilepro_elf_size_dynamic_sections) (tilepro_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol) (ppc64_elf_size_dynamic_sections, ppc64_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-s390.c (elf_s390_adjust_dynamic_symbol) (elf_s390_size_dynamic_sections, elf_s390_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-x86-64.c (elf_x86_64_adjust_dynamic_symbol) (elf_x86_64_size_dynamic_sections) (elf_x86_64_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfnn-aarch64.c (elfNN_aarch64_adjust_dynamic_symbol) (elfNN_aarch64_size_dynamic_sections) (elfNN_aarch64_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfnn-riscv.c (riscv_elf_adjust_dynamic_symbol) (riscv_elf_size_dynamic_sections, riscv_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfxx-mips.c (_bfd_mips_elf_adjust_dynamic_symbol) (_bfd_mips_elf_size_dynamic_sections) (_bfd_mips_vxworks_finish_dynamic_symbol): As above. * elfxx-sparc.c (_bfd_sparc_elf_adjust_dynamic_symbol) (_bfd_sparc_elf_size_dynamic_sections) (_bfd_sparc_elf_finish_dynamic_symbol): As above. * elfxx-tilegx.c (tilegx_elf_adjust_dynamic_symbol) (tilegx_elf_size_dynamic_sections) (tilegx_elf_finish_dynamic_symbol): As above. * elf32-mips.c (elf_backend_want_dynrelro): Define. * elf64-mips.c (elf_backend_want_dynrelro): Define. * elf32-sparc.c (elf_backend_want_dynrelro): Define. * elf64-sparc.c (elf_backend_want_dynrelro): Define. * elf32-tilegx.c (elf_backend_want_dynrelro): Define. * elf64-tilegx.c (elf_backend_want_dynrelro): Define. * elf32-microblaze.c (microblaze_elf_adjust_dynamic_symbol): Tidy. (microblaze_elf_size_dynamic_sections): Handle sdynbss. * elf32-nios2.c (nios2_elf32_size_dynamic_sections): Make use of linker shortcuts to dynamic sections rather than comparing names. Correctly set "got" flag. ld/ PR ld/20995 * testsuite/ld-arm/farcall-mixed-app-v5.d: Update to suit changed stub hash table traversal caused by section id increment. Accept the previous output too. * testsuite/ld-arm/farcall-mixed-app.d: Likewise. * testsuite/ld-arm/farcall-mixed-lib-v4t.d: Likewise. * testsuite/ld-arm/farcall-mixed-lib.d: Likewise. * testsuite/ld-elf/pr20995a.s, * testsuite/ld-elf/pr20995b.s, * testsuite/ld-elf/pr20995.r: New test. * testsuite/ld-elf/elf.exp: Run it.
Diffstat (limited to 'bfd/elf32-tic6x.c')
-rw-r--r--bfd/elf32-tic6x.c30
1 files changed, 23 insertions, 7 deletions
diff --git a/bfd/elf32-tic6x.c b/bfd/elf32-tic6x.c
index c2b22ee..1ccbf9c 100644
--- a/bfd/elf32-tic6x.c
+++ b/bfd/elf32-tic6x.c
@@ -1860,13 +1860,15 @@ elf32_tic6x_finish_dynamic_symbol (bfd * output_bfd,
if (h->needs_copy)
{
Elf_Internal_Rela rel;
+ asection *s;
/* This symbol needs a copy reloc. Set it up. */
if (h->dynindx == -1
|| (h->root.type != bfd_link_hash_defined
&& h->root.type != bfd_link_hash_defweak)
- || htab->elf.srelbss == NULL)
+ || htab->elf.srelbss == NULL
+ || htab->elf.sreldynrelro == NULL)
abort ();
rel.r_offset = (h->root.u.def.value
@@ -1874,8 +1876,12 @@ elf32_tic6x_finish_dynamic_symbol (bfd * output_bfd,
+ h->root.u.def.section->output_offset);
rel.r_info = ELF32_R_INFO (h->dynindx, R_C6000_COPY);
rel.r_addend = 0;
+ if ((h->root.u.def.section->flags & SEC_READONLY) != 0)
+ s = htab->elf.sreldynrelro;
+ else
+ s = htab->elf.srelbss;
- elf32_tic6x_install_rela (output_bfd, htab->elf.srelbss, &rel);
+ elf32_tic6x_install_rela (output_bfd, s, &rel);
}
/* Mark _DYNAMIC and _GLOBAL_OFFSET_TABLE_ as absolute. */
@@ -2061,7 +2067,7 @@ elf32_tic6x_adjust_dynamic_symbol (struct bfd_link_info *info,
{
struct elf32_tic6x_link_hash_table *htab;
bfd *dynobj;
- asection *s;
+ asection *s, *srel;
dynobj = elf_hash_table (info)->dynobj;
@@ -2146,14 +2152,22 @@ elf32_tic6x_adjust_dynamic_symbol (struct bfd_link_info *info,
/* We must generate a R_C6000_COPY reloc to tell the dynamic linker to
copy the initial value out of the dynamic object and into the
runtime process image. */
+ if ((h->root.u.def.section->flags & SEC_READONLY) != 0)
+ {
+ s = htab->elf.sdynrelro;
+ srel = htab->elf.sreldynrelro;
+ }
+ else
+ {
+ s = htab->elf.sdynbss;
+ srel = htab->elf.srelbss;
+ }
if ((h->root.u.def.section->flags & SEC_ALLOC) != 0 && h->size != 0)
{
- htab->elf.srelbss->size += sizeof (Elf32_External_Rela);
+ srel->size += sizeof (Elf32_External_Rela);
h->needs_copy = 1;
}
- s = htab->elf.sdynbss;
-
return _bfd_elf_adjust_dynamic_copy (info, h, s);
}
@@ -3376,7 +3390,8 @@ elf32_tic6x_size_dynamic_sections (bfd *output_bfd, struct bfd_link_info *info)
else if (s == htab->elf.splt
|| s == htab->elf.sgot
|| s == htab->elf.sgotplt
- || s == htab->elf.sdynbss)
+ || s == htab->elf.sdynbss
+ || s == htab->elf.sdynrelro)
{
/* Strip this section if we don't need it; see the
comment below. */
@@ -4369,6 +4384,7 @@ elf32_tic6x_write_section (bfd *output_bfd,
#define elf_backend_can_refcount 1
#define elf_backend_want_got_plt 1
#define elf_backend_want_dynbss 1
+#define elf_backend_want_dynrelro 1
#define elf_backend_plt_readonly 1
#define elf_backend_rela_normal 1
#define elf_backend_got_header_size 8