From 8b43e456886c5b3aaba1ef93195ed888b15de242 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Tue, 5 Sep 2017 11:24:01 -0700 Subject: 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. --- bfd/elf64-x86-64.c | 132 ++++++++++------------------------------------------- 1 file changed, 25 insertions(+), 107 deletions(-) (limited to 'bfd/elf64-x86-64.c') diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c index fa295a5..ddbf133 100644 --- a/bfd/elf64-x86-64.c +++ b/bfd/elf64-x86-64.c @@ -1438,7 +1438,7 @@ elf_x86_64_need_pic (struct bfd_link_info *info, instructions. */ static bfd_boolean -elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, +elf_x86_64_convert_load_reloc (bfd *abfd, bfd_byte *contents, Elf_Internal_Rela *irel, struct elf_link_hash_entry *h, @@ -1447,17 +1447,15 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, { struct elf_x86_link_hash_table *htab; bfd_boolean is_pic; - bfd_boolean require_reloc_pc32; + bfd_boolean no_overflow; bfd_boolean relocx; bfd_boolean to_reloc_pc32; asection *tsec; - char symtype; bfd_signed_vma raddend; unsigned int opcode; unsigned int modrm; unsigned int r_type = ELF32_R_TYPE (irel->r_info); unsigned int r_symndx; - bfd_vma toff; bfd_vma roff = irel->r_offset; if (roff < (r_type == R_X86_64_REX_GOTPCRELX ? 3 : 2)) @@ -1474,10 +1472,8 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, relocx = (r_type == R_X86_64_GOTPCRELX || r_type == R_X86_64_REX_GOTPCRELX); - /* TRUE if we can convert only to R_X86_64_PC32. Enable it for - --no-relax. */ - require_reloc_pc32 - = link_info->disable_target_specific_optimizations > 1; + /* TRUE if --no-relax is used. */ + no_overflow = link_info->disable_target_specific_optimizations > 1; r_symndx = htab->r_sym (irel->r_info); @@ -1496,12 +1492,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, /* We convert only to R_X86_64_PC32: 1. Branch. 2. R_X86_64_GOTPCREL since we can't modify REX byte. - 3. require_reloc_pc32 is true. + 3. no_overflow is true. 4. PIC. */ to_reloc_pc32 = (opcode == 0xff || !relocx - || require_reloc_pc32 + || no_overflow || is_pic); /* Get the symbol referred to by the reloc. */ @@ -1514,8 +1510,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, if (isym->st_shndx == SHN_UNDEF) return TRUE; - symtype = ELF_ST_TYPE (isym->st_info); - if (isym->st_shndx == SHN_ABS) tsec = bfd_abs_section_ptr; else if (isym->st_shndx == SHN_COMMON) @@ -1524,8 +1518,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, tsec = &_bfd_elf_large_com_section; else tsec = bfd_section_from_elf_index (abfd, isym->st_shndx); - - toff = isym->st_value; } else { @@ -1545,7 +1537,7 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, { /* Skip for branch instructions since R_X86_64_PC32 may overflow. */ - if (require_reloc_pc32) + if (no_overflow) return TRUE; } else if (relocx) @@ -1586,13 +1578,11 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, && h->root.u.def.section == bfd_und_section_ptr)))) { /* Skip since R_X86_64_32/R_X86_64_32S may overflow. */ - if (require_reloc_pc32) + if (no_overflow) return TRUE; goto convert; } tsec = h->root.u.def.section; - toff = h->root.u.def.value; - symtype = h->type; } else return TRUE; @@ -1603,92 +1593,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec, && (elf_section_flags (tsec) & SHF_X86_64_LARGE) != 0) return TRUE; - /* We can only estimate relocation overflow for R_X86_64_PC32. */ - if (!to_reloc_pc32) - goto convert; - - 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 += raddend; - - toff = _bfd_merged_section_offset (abfd, &tsec, - elf_section_data (tsec)->sec_info, - toff); - - if (symtype != STT_SECTION) - toff += raddend; - } - else - toff += raddend; - - /* Don't convert if R_X86_64_PC32 relocation overflows. */ - if (tsec->output_section == sec->output_section) - { - if ((toff - roff + 0x80000000) > 0xffffffff) - return TRUE; - } - else - { - bfd_signed_vma distance; - - /* At this point, we don't know the load addresses of TSEC - section nor SEC section. We estimate the distrance between - SEC and TSEC. We store the estimated distances in the - compressed_size field of the output section, which is only - used to decompress the compressed input section. */ - if (sec->output_section->compressed_size == 0) - { - asection *asect; - bfd_size_type size = 0; - for (asect = link_info->output_bfd->sections; - asect != NULL; - asect = asect->next) - /* Skip debug sections since compressed_size is used to - compress debug sections. */ - if ((asect->flags & SEC_DEBUGGING) == 0) - { - asection *i; - for (i = asect->map_head.s; - i != NULL; - i = i->map_head.s) - { - size = align_power (size, i->alignment_power); - size += i->size; - } - asect->compressed_size = size; - } - } - - /* Don't convert GOTPCREL relocations if TSEC isn't placed - after SEC. */ - distance = (tsec->output_section->compressed_size - - sec->output_section->compressed_size); - if (distance < 0) - return TRUE; + /* Skip since R_X86_64_PC32/R_X86_64_32/R_X86_64_32S may overflow. */ + if (no_overflow) + return TRUE; - /* Take PT_GNU_RELRO segment into account by adding - maxpagesize. */ - if ((toff + distance + get_elf_backend_data (abfd)->maxpagesize - - roff + 0x80000000) > 0xffffffff) - return TRUE; - } + if (h != NULL) + ((struct elf_x86_link_hash_entry *) h)->converted_reloc = 1; convert: if (opcode == 0xff) @@ -2467,7 +2377,7 @@ _bfd_x86_64_elf_convert_load (bfd *abfd, asection *sec, continue; converted = FALSE; - if (!elf_x86_64_convert_load_reloc (abfd, sec, contents, irel, h, + if (!elf_x86_64_convert_load_reloc (abfd, contents, irel, h, &converted, link_info)) goto error_return; @@ -4099,9 +4009,17 @@ check_relocation_error: } if (r == bfd_reloc_overflow) - (*info->callbacks->reloc_overflow) - (info, (h ? &h->root : NULL), name, howto->name, - (bfd_vma) 0, input_bfd, input_section, rel->r_offset); + { + if (eh != NULL && eh->converted_reloc) + { + info->callbacks->einfo + (_("%F%P: failed to convert GOTPCREL relocation; relink with --no-relax\n")); + return FALSE; + } + (*info->callbacks->reloc_overflow) + (info, (h ? &h->root : NULL), name, howto->name, + (bfd_vma) 0, input_bfd, input_section, rel->r_offset); + } else { _bfd_error_handler -- cgit v1.1