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.
This commit is contained in:
H.J. Lu
parent
602a67cbea
commit
59cab53283
@ -1,3 +1,10 @@
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2015-06-24 H.J. Lu <hongjiu.lu@intel.com>
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PR ld/18591
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* elf64-x86-64.c (elf_x86_64_convert_mov_to_lea): Don't convert
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R_X86_64_GOTPCREL to R_X86_64_PC32 if it will cause relocation
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overflow.
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2015-06-23 Jiong Wang <jiong.wang@arm.com>
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* elfnn-aarch64.c (aarch64_readonly_dynrelocs): New function.
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@ -2901,6 +2901,7 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
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bfd_boolean changed_contents;
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bfd_boolean changed_relocs;
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bfd_signed_vma *local_got_refcounts;
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bfd_vma maxpagesize;
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/* Don't even try to convert non-ELF outputs. */
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if (!is_elf_hash_table (link_info->hash))
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@ -2925,6 +2926,7 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
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changed_contents = FALSE;
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changed_relocs = FALSE;
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local_got_refcounts = elf_local_got_refcounts (abfd);
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maxpagesize = get_elf_backend_data (abfd)->maxpagesize;
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/* Get the section contents. */
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if (elf_section_data (sec)->this_hdr.contents != NULL)
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@ -2942,10 +2944,27 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
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unsigned int r_symndx = htab->r_sym (irel->r_info);
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unsigned int indx;
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struct elf_link_hash_entry *h;
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asection *tsec;
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char symtype;
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bfd_vma toff, roff;
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enum {
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none, local, global
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} convert_mov_to_lea;
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if (r_type != R_X86_64_GOTPCREL)
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continue;
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roff = irel->r_offset;
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/* Don't convert R_X86_64_GOTPCREL relocation if it isn't for mov
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instruction. */
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if (roff < 2
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|| bfd_get_8 (abfd, contents + roff - 2) != 0x8b)
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continue;
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tsec = NULL;
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convert_mov_to_lea = none;
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/* Get the symbol referred to by the reloc. */
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if (r_symndx < symtab_hdr->sh_info)
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{
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@ -2954,22 +2973,27 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
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isym = bfd_sym_from_r_symndx (&htab->sym_cache,
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abfd, r_symndx);
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/* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation. */
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if (ELF_ST_TYPE (isym->st_info) != STT_GNU_IFUNC
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&& irel->r_offset >= 2
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&& bfd_get_8 (abfd, contents + irel->r_offset - 2) == 0x8b)
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{
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bfd_put_8 (abfd, 0x8d, contents + irel->r_offset - 2);
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irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
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if (local_got_refcounts != NULL
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&& local_got_refcounts[r_symndx] > 0)
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local_got_refcounts[r_symndx] -= 1;
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changed_contents = TRUE;
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changed_relocs = TRUE;
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}
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continue;
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}
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symtype = ELF_ST_TYPE (isym->st_info);
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/* STT_GNU_IFUNC must keep R_X86_64_GOTPCREL relocation and
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skip relocation against undefined symbols. */
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if (symtype != STT_GNU_IFUNC && isym->st_shndx != SHN_UNDEF)
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{
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if (isym->st_shndx == SHN_ABS)
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tsec = bfd_abs_section_ptr;
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else if (isym->st_shndx == SHN_COMMON)
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tsec = bfd_com_section_ptr;
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else if (isym->st_shndx == SHN_X86_64_LCOMMON)
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tsec = &_bfd_elf_large_com_section;
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else
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tsec = bfd_section_from_elf_index (abfd, isym->st_shndx);
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toff = isym->st_value;
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convert_mov_to_lea = local;
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}
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}
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else
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{
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indx = r_symndx - symtab_hdr->sh_info;
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h = elf_sym_hashes (abfd)[indx];
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BFD_ASSERT (h != NULL);
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@ -2984,16 +3008,105 @@ elf_x86_64_convert_mov_to_lea (bfd *abfd, asection *sec,
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if (h->def_regular
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&& h->type != STT_GNU_IFUNC
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&& h != htab->elf.hdynamic
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&& SYMBOL_REFERENCES_LOCAL (link_info, h)
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&& irel->r_offset >= 2
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&& bfd_get_8 (abfd, contents + irel->r_offset - 2) == 0x8b)
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&& SYMBOL_REFERENCES_LOCAL (link_info, h))
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{
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bfd_put_8 (abfd, 0x8d, contents + irel->r_offset - 2);
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tsec = h->root.u.def.section;
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toff = h->root.u.def.value;
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symtype = h->type;
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convert_mov_to_lea = global;
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}
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}
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if (convert_mov_to_lea == none)
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continue;
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if (tsec->sec_info_type == SEC_INFO_TYPE_MERGE)
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{
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/* At this stage in linking, no SEC_MERGE symbol has been
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adjusted, so all references to such symbols need to be
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passed through _bfd_merged_section_offset. (Later, in
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relocate_section, all SEC_MERGE symbols *except* for
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section symbols have been adjusted.)
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gas may reduce relocations against symbols in SEC_MERGE
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sections to a relocation against the section symbol when
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the original addend was zero. When the reloc is against
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a section symbol we should include the addend in the
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offset passed to _bfd_merged_section_offset, since the
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location of interest is the original symbol. On the
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other hand, an access to "sym+addend" where "sym" is not
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a section symbol should not include the addend; Such an
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access is presumed to be an offset from "sym"; The
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location of interest is just "sym". */
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if (symtype == STT_SECTION)
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toff += irel->r_addend;
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toff = _bfd_merged_section_offset (abfd, &tsec,
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elf_section_data (tsec)->sec_info,
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toff);
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if (symtype != STT_SECTION)
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toff += irel->r_addend;
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}
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else
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toff += irel->r_addend;
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/* Don't convert if R_X86_64_PC32 relocation overflows. */
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if (tsec->output_section == sec->output_section)
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{
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if ((toff - roff + 0x80000000) > 0xffffffff)
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continue;
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}
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else
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{
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asection *asect;
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bfd_size_type size;
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/* At this point, we don't know the load addresses of TSEC
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section nor SEC section. We estimate the distrance between
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SEC and TSEC. */
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size = 0;
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for (asect = sec->output_section;
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asect != NULL && asect != tsec->output_section;
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asect = asect->next)
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{
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asection *i;
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for (i = asect->output_section->map_head.s;
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i != NULL;
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i = i->map_head.s)
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{
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size = align_power (size, i->alignment_power);
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size += i->size;
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}
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}
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/* Don't convert R_X86_64_GOTPCREL if TSEC isn't placed after
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SEC. */
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if (asect == NULL)
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continue;
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/* Take PT_GNU_RELRO segment into account by adding
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maxpagesize. */
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if ((toff + size + maxpagesize - roff + 0x80000000)
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> 0xffffffff)
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continue;
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}
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bfd_put_8 (abfd, 0x8d, contents + roff - 2);
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irel->r_info = htab->r_info (r_symndx, R_X86_64_PC32);
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if (h->got.refcount > 0)
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h->got.refcount -= 1;
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changed_contents = TRUE;
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changed_relocs = TRUE;
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if (convert_mov_to_lea == local)
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{
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if (local_got_refcounts != NULL
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&& local_got_refcounts[r_symndx] > 0)
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local_got_refcounts[r_symndx] -= 1;
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}
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else
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{
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if (h->got.refcount > 0)
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h->got.refcount -= 1;
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}
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}
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