aboutsummaryrefslogtreecommitdiff
path: root/bfd/elf64-x86-64.c
diff options
context:
space:
mode:
authorH.J. Lu <hjl.tools@gmail.com>2015-06-24 10:13:55 -0700
committerH.J. Lu <hjl.tools@gmail.com>2015-06-24 10:20:41 -0700
commit59cab532835904f368b0aa99267afba5fda5ded2 (patch)
tree8fb4af8a6efb9bbe553be48d6ab564eb15ee0f97 /bfd/elf64-x86-64.c
parent602a67cbeaf6b42bc513a873aec82e53235b8754 (diff)
downloadgdb-59cab532835904f368b0aa99267afba5fda5ded2.zip
gdb-59cab532835904f368b0aa99267afba5fda5ded2.tar.gz
gdb-59cab532835904f368b0aa99267afba5fda5ded2.tar.bz2
Don't convert R_X86_64_GOTPCREL if it will overflow
When converting "mov foo@GOTPCREL(%rip), %reg" to "lea foo(%rip), %reg" with R_X86_64_PC32 relocation, it may overflow if the target section is more than 2GB away. This patch estimates distance between mov instruction and the target section. We convert R_X86_64_GOTPCREL to R_X86_64_PC32 only if their distance is less than 2GB. PR ld/18591 * elf64-x86-64.c (elf_x86_64_convert_mov_to_lea): Don't convert R_X86_64_GOTPCREL to R_X86_64_PC32 if it will cause relocation overflow.
Diffstat (limited to 'bfd/elf64-x86-64.c')
-rw-r--r--bfd/elf64-x86-64.c175
1 files changed, 144 insertions, 31 deletions
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 072c00b..f7aea98 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -2901,6 +2901,7 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
bfd_boolean changed_contents;
bfd_boolean changed_relocs;
bfd_signed_vma *local_got_refcounts;
+ bfd_vma maxpagesize;
/* Don't even try to convert non-ELF outputs. */
if (!is_elf_hash_table (link_info->hash))
@@ -2925,6 +2926,7 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
changed_contents = FALSE;
changed_relocs = FALSE;
local_got_refcounts = elf_local_got_refcounts (abfd);
+ maxpagesize = get_elf_backend_data (abfd)->maxpagesize;
/* Get the section contents. */
if (elf_section_data (sec)->this_hdr.contents != NULL)
@@ -2942,10 +2944,27 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
unsigned int r_symndx = htab->r_sym (irel->r_info);
unsigned int indx;
struct elf_link_hash_entry *h;
+ asection *tsec;
+ char symtype;
+ bfd_vma toff, roff;
+ enum {
+ none, local, global
+ } convert_mov_to_lea;
if (r_type != R_X86_64_GOTPCREL)
continue;
+ roff = irel->r_offset;
+
+ /* Don't convert R_X86_64_GOTPCREL relocation if it isn't for mov
+ instruction. */
+ if (roff < 2
+ || bfd_get_8 (abfd, contents + roff - 2) != 0x8b)
+ continue;
+
+ tsec = NULL;
+ convert_mov_to_lea = none;
+
/* Get the symbol referred to by the reloc. */
if (r_symndx < symtab_hdr->sh_info)
{
@@ -2954,46 +2973,140 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
isym = bfd_sym_from_r_symndx (&htab->sym_cache,
abfd, r_symndx);
- /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation. */
- if (ELF_ST_TYPE (isym->st_info) != STT_GNU_IFUNC
- && irel->r_offset >= 2
- && bfd_get_8 (abfd, contents + irel->r_offset - 2) == 0x8b)
+ symtype = ELF_ST_TYPE (isym->st_info);
+
+ /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation and
+ skip relocation against undefined symbols. */
+ if (symtype != STT_GNU_IFUNC && isym->st_shndx != SHN_UNDEF)
{
- bfd_put_8 (abfd, 0x8d, contents + irel->r_offset - 2);
- irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
- if (local_got_refcounts != NULL
- && local_got_refcounts[r_symndx] > 0)
- local_got_refcounts[r_symndx] -= 1;
- changed_contents = TRUE;
- changed_relocs = TRUE;
+ if (isym->st_shndx == SHN_ABS)
+ tsec = bfd_abs_section_ptr;
+ else if (isym->st_shndx == SHN_COMMON)
+ tsec = bfd_com_section_ptr;
+ else if (isym->st_shndx == SHN_X86_64_LCOMMON)
+ tsec = &_bfd_elf_large_com_section;
+ else
+ tsec = bfd_section_from_elf_index (abfd, isym->st_shndx);
+
+ toff = isym->st_value;
+ convert_mov_to_lea = local;
}
- continue;
}
+ else
+ {
+ indx = r_symndx - symtab_hdr->sh_info;
+ h = elf_sym_hashes (abfd)[indx];
+ BFD_ASSERT (h != NULL);
- indx = r_symndx - symtab_hdr->sh_info;
- h = elf_sym_hashes (abfd)[indx];
- BFD_ASSERT (h != NULL);
+ while (h->root.type == bfd_link_hash_indirect
+ || h->root.type == bfd_link_hash_warning)
+ h = (struct elf_link_hash_entry *) h->root.u.i.link;
- while (h->root.type == bfd_link_hash_indirect
- || h->root.type == bfd_link_hash_warning)
- h = (struct elf_link_hash_entry *) h->root.u.i.link;
+ /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation. We also
+ avoid optimizing _DYNAMIC since ld.so may use its link-time
+ address. */
+ if (h->def_regular
+ && h->type != STT_GNU_IFUNC
+ && h != htab->elf.hdynamic
+ && SYMBOL_REFERENCES_LOCAL (link_info, h))
+ {
+ tsec = h->root.u.def.section;
+ toff = h->root.u.def.value;
+ symtype = h->type;
+ convert_mov_to_lea = global;
+ }
+ }
- /* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation. We also
- avoid optimizing _DYNAMIC since ld.so may use its link-time
- address. */
- if (h->def_regular
- && h->type != STT_GNU_IFUNC
- && h != htab->elf.hdynamic
- && SYMBOL_REFERENCES_LOCAL (link_info, h)
- && irel->r_offset >= 2
- && bfd_get_8 (abfd, contents + irel->r_offset - 2) == 0x8b)
+ if (convert_mov_to_lea == none)
+ continue;
+
+ if (tsec->sec_info_type == SEC_INFO_TYPE_MERGE)
+ {
+ /* At this stage in linking, no SEC_MERGE symbol has been
+ adjusted, so all references to such symbols need to be
+ passed through _bfd_merged_section_offset. (Later, in
+ relocate_section, all SEC_MERGE symbols *except* for
+ section symbols have been adjusted.)
+
+ gas may reduce relocations against symbols in SEC_MERGE
+ sections to a relocation against the section symbol when
+ the original addend was zero. When the reloc is against
+ a section symbol we should include the addend in the
+ offset passed to _bfd_merged_section_offset, since the
+ location of interest is the original symbol. On the
+ other hand, an access to "sym+addend" where "sym" is not
+ a section symbol should not include the addend; Such an
+ access is presumed to be an offset from "sym"; The
+ location of interest is just "sym". */
+ if (symtype == STT_SECTION)
+ toff += irel->r_addend;
+
+ toff = _bfd_merged_section_offset (abfd, &tsec,
+ elf_section_data (tsec)->sec_info,
+ toff);
+
+ if (symtype != STT_SECTION)
+ toff += irel->r_addend;
+ }
+ else
+ toff += irel->r_addend;
+
+ /* Don't convert if R_X86_64_PC32 relocation overflows. */
+ if (tsec->output_section == sec->output_section)
+ {
+ if ((toff - roff + 0x80000000) > 0xffffffff)
+ continue;
+ }
+ else
+ {
+ asection *asect;
+ bfd_size_type size;
+
+ /* At this point, we don't know the load addresses of TSEC
+ section nor SEC section. We estimate the distrance between
+ SEC and TSEC. */
+ size = 0;
+ for (asect = sec->output_section;
+ asect != NULL && asect != tsec->output_section;
+ asect = asect->next)
+ {
+ asection *i;
+ for (i = asect->output_section->map_head.s;
+ i != NULL;
+ i = i->map_head.s)
+ {
+ size = align_power (size, i->alignment_power);
+ size += i->size;
+ }
+ }
+
+ /* Don't convert R_X86_64_GOTPCREL if TSEC isn't placed after
+ SEC. */
+ if (asect == NULL)
+ continue;
+
+ /* Take PT_GNU_RELRO segment into account by adding
+ maxpagesize. */
+ if ((toff + size + maxpagesize - roff + 0x80000000)
+ > 0xffffffff)
+ continue;
+ }
+
+ bfd_put_8 (abfd, 0x8d, contents + roff - 2);
+ irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
+ changed_contents = TRUE;
+ changed_relocs = TRUE;
+
+ if (convert_mov_to_lea == local)
+ {
+ if (local_got_refcounts != NULL
+ && local_got_refcounts[r_symndx] > 0)
+ local_got_refcounts[r_symndx] -= 1;
+ }
+ else
{
- bfd_put_8 (abfd, 0x8d, contents + irel->r_offset - 2);
- irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
if (h->got.refcount > 0)
h->got.refcount -= 1;
- changed_contents = TRUE;
- changed_relocs = TRUE;
}
}