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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-microblaze.c
parent9d19e4fdb7c684329c8b1b72796a0071708dabc7 (diff)
downloadbinutils-gdb-5474d94f03aedba2f832006dc7d680cc15792a7b.tar.gz
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-microblaze.c')
-rw-r--r--bfd/elf32-microblaze.c42
1 files changed, 26 insertions, 16 deletions
diff --git a/bfd/elf32-microblaze.c b/bfd/elf32-microblaze.c
index 33c6026e853..31527d5a455 100644
--- a/bfd/elf32-microblaze.c
+++ b/bfd/elf32-microblaze.c
@@ -2557,9 +2557,8 @@ microblaze_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
struct elf32_mb_link_hash_table *htab;
struct elf32_mb_link_hash_entry * eh;
struct elf32_mb_dyn_relocs *p;
- asection *sdynbss, *s;
+ asection *s, *srel;
unsigned int power_of_two;
- bfd *dynobj;
htab = elf32_mb_hash_table (info);
if (htab == NULL)
@@ -2658,11 +2657,19 @@ microblaze_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
/* We must generate a R_MICROBLAZE_COPY reloc to tell the dynamic linker
to copy the initial value out of the dynamic object and into the
runtime process image. */
- dynobj = elf_hash_table (info)->dynobj;
- BFD_ASSERT (dynobj != NULL);
+ 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)
{
- htab->elf.srelbss->size += sizeof (Elf32_External_Rela);
+ srel->size += sizeof (Elf32_External_Rela);
h->needs_copy = 1;
}
@@ -2672,21 +2679,20 @@ microblaze_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
if (power_of_two > 3)
power_of_two = 3;
- sdynbss = htab->elf.sdynbss;
/* Apply the required alignment. */
- sdynbss->size = BFD_ALIGN (sdynbss->size, (bfd_size_type) (1 << power_of_two));
- if (power_of_two > bfd_get_section_alignment (dynobj, sdynbss))
+ s->size = BFD_ALIGN (s->size, (bfd_size_type) (1 << power_of_two));
+ if (power_of_two > s->alignment_power)
{
- if (! bfd_set_section_alignment (dynobj, sdynbss, power_of_two))
+ if (!bfd_set_section_alignment (s->owner, s, power_of_two))
return FALSE;
}
/* Define the symbol as being at this point in the section. */
- h->root.u.def.section = sdynbss;
- h->root.u.def.value = sdynbss->size;
+ h->root.u.def.section = s;
+ h->root.u.def.value = s->size;
/* Increment the section size to make room for the symbol. */
- sdynbss->size += h->size;
+ s->size += h->size;
return TRUE;
}
@@ -3050,7 +3056,9 @@ microblaze_elf_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
}
else if (s != htab->elf.splt
&& s != htab->elf.sgot
- && s != htab->elf.sgotplt)
+ && s != htab->elf.sgotplt
+ && s != htab->elf.sdynbss
+ && s != htab->elf.sdynrelro)
{
/* It's not one of our sections, so don't allocate space. */
continue;
@@ -3256,14 +3264,15 @@ microblaze_elf_finish_dynamic_symbol (bfd *output_bfd,
BFD_ASSERT (h->dynindx != -1);
- s = bfd_get_linker_section (htab->elf.dynobj, ".rela.bss");
- BFD_ASSERT (s != NULL);
-
rela.r_offset = (h->root.u.def.value
+ h->root.u.def.section->output_section->vma
+ h->root.u.def.section->output_offset);
rela.r_info = ELF32_R_INFO (h->dynindx, R_MICROBLAZE_COPY);
rela.r_addend = 0;
+ if ((h->root.u.def.section->flags & SEC_READONLY) != 0)
+ s = htab->elf.sreldynrelro;
+ else
+ s = htab->elf.srelbss;
loc = s->contents + s->reloc_count++ * sizeof (Elf32_External_Rela);
bfd_elf32_swap_reloca_out (output_bfd, &rela, loc);
}
@@ -3439,6 +3448,7 @@ microblaze_elf_add_symbol_hook (bfd *abfd,
#define elf_backend_want_got_plt 1
#define elf_backend_plt_readonly 1
#define elf_backend_got_header_size 12
+#define elf_backend_want_dynrelro 1
#define elf_backend_rela_normal 1
#define elf_backend_dtrel_excludes_plt 1