x86-64: Improve GOTPCREL relocation conversion
When GOTPCREL relocation conversion leads to relocation overflow, we may get a mysterious linker message, like relocation truncated to fit: R_X86_64_32S against symbol `foo' This patch changes the linker message to failed to convert GOTPCREL relocation; relink with --no-relax bfd/ * elf64-x86-64.c (elf_x86_64_convert_load_reloc): Remove the sec argument. Don't check relocation overflow. Avoid relocation overflow if --no-relax is used. Set converted_reloc on symbol if a GOTPCREL relocation is converted. (elf_x86_64_relocate_section): Issue a fatal error and suggest --no-relax if GOTPCREL relocation conversion leads to relocation overflow. * elfxx-x86.h (elf_x86_link_hash_entry): Add converted_reloc. ld/ * testsuite/ld-x86-64/pr19609-4e.d: Updated. * testsuite/ld-x86-64/pr19609-6a.d: Likewise.
This commit is contained in:
H.J. Lu
parent
5eb5f85062
commit
8b43e45688
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@ -1,3 +1,14 @@
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2017-09-05 H.J. Lu <hongjiu.lu@intel.com>
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* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Remove the sec
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argument. Don't check relocation overflow. Avoid relocation
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overflow if --no-relax is used. Set converted_reloc on symbol
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if a GOTPCREL relocation is converted.
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(elf_x86_64_relocate_section): Issue a fatal error and suggest
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--no-relax if GOTPCREL relocation conversion leads to relocation
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overflow.
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* elfxx-x86.h (elf_x86_link_hash_entry): Add converted_reloc.
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2017-09-05 Alexander Fedotov <alexander.fedotov@nxp.com>
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Edmar Wienskoski <edmar.wienskoski@nxp.com
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@ -1438,7 +1438,7 @@ elf_x86_64_need_pic (struct bfd_link_info *info,
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instructions. */
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static bfd_boolean
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elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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elf_x86_64_convert_load_reloc (bfd *abfd,
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bfd_byte *contents,
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Elf_Internal_Rela *irel,
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struct elf_link_hash_entry *h,
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@ -1447,17 +1447,15 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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{
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struct elf_x86_link_hash_table *htab;
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bfd_boolean is_pic;
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bfd_boolean require_reloc_pc32;
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bfd_boolean no_overflow;
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bfd_boolean relocx;
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bfd_boolean to_reloc_pc32;
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asection *tsec;
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char symtype;
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bfd_signed_vma raddend;
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unsigned int opcode;
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unsigned int modrm;
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unsigned int r_type = ELF32_R_TYPE (irel->r_info);
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unsigned int r_symndx;
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bfd_vma toff;
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bfd_vma roff = irel->r_offset;
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if (roff < (r_type == R_X86_64_REX_GOTPCRELX ? 3 : 2))
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@ -1474,10 +1472,8 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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relocx = (r_type == R_X86_64_GOTPCRELX
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|| r_type == R_X86_64_REX_GOTPCRELX);
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/* TRUE if we can convert only to R_X86_64_PC32. Enable it for
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--no-relax. */
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require_reloc_pc32
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= link_info->disable_target_specific_optimizations > 1;
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/* TRUE if --no-relax is used. */
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no_overflow = link_info->disable_target_specific_optimizations > 1;
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r_symndx = htab->r_sym (irel->r_info);
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@ -1496,12 +1492,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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/* We convert only to R_X86_64_PC32:
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1. Branch.
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2. R_X86_64_GOTPCREL since we can't modify REX byte.
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3. require_reloc_pc32 is true.
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3. no_overflow is true.
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4. PIC.
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*/
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to_reloc_pc32 = (opcode == 0xff
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|| !relocx
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|| require_reloc_pc32
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|| no_overflow
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|| is_pic);
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/* Get the symbol referred to by the reloc. */
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@ -1514,8 +1510,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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if (isym->st_shndx == SHN_UNDEF)
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return TRUE;
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symtype = ELF_ST_TYPE (isym->st_info);
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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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@ -1524,8 +1518,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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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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}
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else
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{
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@ -1545,7 +1537,7 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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{
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/* Skip for branch instructions since R_X86_64_PC32
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may overflow. */
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if (require_reloc_pc32)
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if (no_overflow)
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return TRUE;
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}
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else if (relocx)
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@ -1586,13 +1578,11 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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&& h->root.u.def.section == bfd_und_section_ptr))))
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{
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/* Skip since R_X86_64_32/R_X86_64_32S may overflow. */
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if (require_reloc_pc32)
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if (no_overflow)
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return TRUE;
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goto convert;
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}
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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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}
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else
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return TRUE;
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@ -1603,92 +1593,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
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&& (elf_section_flags (tsec) & SHF_X86_64_LARGE) != 0)
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return TRUE;
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/* We can only estimate relocation overflow for R_X86_64_PC32. */
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if (!to_reloc_pc32)
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goto convert;
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/* Skip since R_X86_64_PC32/R_X86_64_32/R_X86_64_32S may overflow. */
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if (no_overflow)
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return TRUE;
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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 += raddend;
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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 += raddend;
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}
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else
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toff += raddend;
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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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return TRUE;
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}
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else
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{
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bfd_signed_vma distance;
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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. We store the estimated distances in the
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compressed_size field of the output section, which is only
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used to decompress the compressed input section. */
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if (sec->output_section->compressed_size == 0)
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{
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asection *asect;
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bfd_size_type size = 0;
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for (asect = link_info->output_bfd->sections;
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asect != NULL;
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asect = asect->next)
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/* Skip debug sections since compressed_size is used to
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compress debug sections. */
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if ((asect->flags & SEC_DEBUGGING) == 0)
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{
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asection *i;
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for (i = asect->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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asect->compressed_size = size;
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}
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}
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/* Don't convert GOTPCREL relocations if TSEC isn't placed
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after SEC. */
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distance = (tsec->output_section->compressed_size
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- sec->output_section->compressed_size);
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if (distance < 0)
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return TRUE;
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/* Take PT_GNU_RELRO segment into account by adding
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maxpagesize. */
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if ((toff + distance + get_elf_backend_data (abfd)->maxpagesize
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- roff + 0x80000000) > 0xffffffff)
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return TRUE;
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}
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if (h != NULL)
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((struct elf_x86_link_hash_entry *) h)->converted_reloc = 1;
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convert:
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if (opcode == 0xff)
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@ -2467,7 +2377,7 @@ _bfd_x86_64_elf_convert_load (bfd *abfd, asection *sec,
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continue;
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converted = FALSE;
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if (!elf_x86_64_convert_load_reloc (abfd, sec, contents, irel, h,
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if (!elf_x86_64_convert_load_reloc (abfd, contents, irel, h,
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&converted, link_info))
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goto error_return;
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@ -4099,9 +4009,17 @@ check_relocation_error:
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}
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if (r == bfd_reloc_overflow)
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(*info->callbacks->reloc_overflow)
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(info, (h ? &h->root : NULL), name, howto->name,
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(bfd_vma) 0, input_bfd, input_section, rel->r_offset);
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{
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if (eh != NULL && eh->converted_reloc)
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{
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info->callbacks->einfo
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(_("%F%P: failed to convert GOTPCREL relocation; relink with --no-relax\n"));
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return FALSE;
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}
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(*info->callbacks->reloc_overflow)
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(info, (h ? &h->root : NULL), name, howto->name,
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(bfd_vma) 0, input_bfd, input_section, rel->r_offset);
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}
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else
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{
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_bfd_error_handler
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@ -110,6 +110,11 @@ struct elf_x86_link_hash_entry
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is only used by x86-64. */
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unsigned int needs_copy : 1;
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/* TRUE if a symbol with GOTPCREL relocations which have been converted
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to R_X86_64_PC32, R_X86_64_32 or R_X86_64_32S. This is only used by
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x86-64 for now. */
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unsigned int converted_reloc : 1;
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/* Reference count of C/C++ function pointer relocations in read-write
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section which can be resolved at run-time. */
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bfd_signed_vma func_pointer_refcount;
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@ -1,3 +1,8 @@
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2017-09-05 H.J. Lu <hongjiu.lu@intel.com>
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* testsuite/ld-x86-64/pr19609-4e.d: Updated.
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* testsuite/ld-x86-64/pr19609-6a.d: Likewise.
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2017-09-03 H.J. Lu <hongjiu.lu@intel.com>
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PR ld/22071
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@ -9,5 +9,5 @@
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Disassembly of section .text:
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0+70000000 <_start>:
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[ ]*[a-f0-9]+: 48 8d 05 f9 ff ff 2f lea 0x2ffffff9\(%rip\),%rax # a0000000 <foo>
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[ ]*[a-f0-9]+: 4c 8d 1d f2 ff ff 2f lea 0x2ffffff2\(%rip\),%r11 # a0000000 <foo>
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[ ]*[a-f0-9]+: 48 8b 05 ([0-9a-f]{2} ){4} * mov [-]?0x[a-f0-9]+\(%rip\),%rax # [a-f0-9]+ <.got>
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[ ]*[a-f0-9]+: 4c 8b 1d ([0-9a-f]{2} ){4} * mov [-]?0x[a-f0-9]+\(%rip\),%r11 # [a-f0-9]+ <.got>
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@ -1,4 +1,4 @@
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#source: pr19609-6.s
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#as: --64 -mrelax-relocations=yes
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#ld: -melf_x86_64 --defsym foobar=0x80000000
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#error: .*relocation truncated to fit: R_X86_64_32S .*
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#error: failed to convert GOTPCREL relocation; relink with --no-relax
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