diff options
Diffstat (limited to 'bfd/elf32-i386.c')
| -rw-r--r-- | bfd/elf32-i386.c | 222 |
1 files changed, 194 insertions, 28 deletions
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c index 64cdece..5c35d65 100644 --- a/bfd/elf32-i386.c +++ b/bfd/elf32-i386.c @@ -580,6 +580,24 @@ static const bfd_byte elf_i386_pic_plt_entry[PLT_ENTRY_SIZE] = 0, 0, 0, 0 /* replaced with offset to start of .plt. */ }; +/* Entries in the GOT procedure linkage table look like this. */ + +static const bfd_byte elf_i386_got_plt_entry[8] = +{ + 0xff, 0x25, /* jmp indirect */ + 0, 0, 0, 0, /* replaced with offset of this symbol in .got. */ + 0x66, 0x90 /* xchg %ax,%ax */ +}; + +/* Entries in the PIC GOT procedure linkage table look like this. */ + +static const bfd_byte elf_i386_pic_got_plt_entry[8] = +{ + 0xff, 0xa3, /* jmp *offset(%ebx) */ + 0, 0, 0, 0, /* replaced with offset of this symbol in .got. */ + 0x66, 0x90 /* xchg %ax,%ax */ +}; + /* .eh_frame covering the .plt section. */ static const bfd_byte elf_i386_eh_frame_plt[] = @@ -736,6 +754,10 @@ struct elf_i386_link_hash_entry (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type)) unsigned char tls_type; + /* Information about the GOT PLT entry. Filled when there are both + GOT and PLT relocations against the same function. */ + union gotplt_union plt_got; + /* Offset of the GOTPLT entry reserved for the TLS descriptor, starting at the end of the jump table. */ bfd_vma tlsdesc_got; @@ -785,6 +807,7 @@ struct elf_i386_link_hash_table asection *sdynbss; asection *srelbss; asection *plt_eh_frame; + asection *plt_got; union { @@ -854,6 +877,7 @@ elf_i386_link_hash_newfunc (struct bfd_hash_entry *entry, eh = (struct elf_i386_link_hash_entry *) entry; eh->dyn_relocs = NULL; eh->tls_type = GOT_UNKNOWN; + eh->plt_got.offset = (bfd_vma) -1; eh->tlsdesc_got = (bfd_vma) -1; } @@ -922,6 +946,7 @@ elf_i386_get_local_sym_hash (struct elf_i386_link_hash_table *htab, ret->elf.indx = sec->id; ret->elf.dynstr_index = ELF32_R_SYM (rel->r_info); ret->elf.dynindx = -1; + ret->plt_got.offset = (bfd_vma) -1; *slot = ret; } return &ret->elf; @@ -1418,6 +1443,7 @@ elf_i386_check_relocs (bfd *abfd, const Elf_Internal_Rela *rel; const Elf_Internal_Rela *rel_end; asection *sreloc; + bfd_boolean use_plt_got; if (info->relocatable) return TRUE; @@ -1428,6 +1454,10 @@ elf_i386_check_relocs (bfd *abfd, if (htab == NULL) return FALSE; + use_plt_got = (!get_elf_i386_backend_data (abfd)->is_vxworks + && (get_elf_i386_backend_data (abfd) + == &elf_i386_arch_bed)); + symtab_hdr = &elf_symtab_hdr (abfd); sym_hashes = elf_sym_hashes (abfd); @@ -1819,6 +1849,39 @@ do_size: default: break; } + + if (use_plt_got + && h != NULL + && h->plt.refcount > 0 + && h->got.refcount > 0 + && htab->plt_got == NULL) + { + /* Create the GOT procedure linkage table. */ + unsigned int plt_got_align; + const struct elf_backend_data *bed; + + bed = get_elf_backend_data (info->output_bfd); + BFD_ASSERT (sizeof (elf_i386_got_plt_entry) == 8 + && (sizeof (elf_i386_got_plt_entry) + == sizeof (elf_i386_pic_got_plt_entry))); + plt_got_align = 3; + + if (htab->elf.dynobj == NULL) + htab->elf.dynobj = abfd; + htab->plt_got + = bfd_make_section_anyway_with_flags (htab->elf.dynobj, + ".plt.got", + (bed->dynamic_sec_flags + | SEC_ALLOC + | SEC_CODE + | SEC_LOAD + | SEC_READONLY)); + if (htab->plt_got == NULL + || !bfd_set_section_alignment (htab->elf.dynobj, + htab->plt_got, + plt_got_align)) + return FALSE; + } } return TRUE; @@ -2191,6 +2254,24 @@ elf_i386_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf) plt_entry_size = GET_PLT_ENTRY_SIZE (info->output_bfd); + /* We can't use the GOT PLT if pointer equality is needed since + finish_dynamic_symbol won't clear symbol value and the dynamic + linker won't update the GOT slot. We will get into an infinite + loop at run-time. */ + if (htab->plt_got != NULL + && h->type != STT_GNU_IFUNC + && !h->pointer_equality_needed + && h->plt.refcount > 0 + && h->got.refcount > 0) + { + /* Don't use the regular PLT if there are both GOT and GOTPLT + reloctions. */ + h->plt.offset = (bfd_vma) -1; + + /* Use the GOT PLT. */ + eh->plt_got.refcount = 1; + } + /* Since STT_GNU_IFUNC symbol must go through PLT, we handle it here if it is defined and referenced in a non-shared object. */ if (h->type == STT_GNU_IFUNC @@ -2199,8 +2280,10 @@ elf_i386_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf) plt_entry_size, plt_entry_size, 4); else if (htab->elf.dynamic_sections_created - && h->plt.refcount > 0) + && (h->plt.refcount > 0 || eh->plt_got.refcount > 0)) { + bfd_boolean use_plt_got = eh->plt_got.refcount > 0; + /* Make sure this symbol is output as a dynamic symbol. Undefined weak syms won't yet be marked as dynamic. */ if (h->dynindx == -1 @@ -2214,13 +2297,17 @@ elf_i386_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf) || WILL_CALL_FINISH_DYNAMIC_SYMBOL (1, 0, h)) { asection *s = htab->elf.splt; + asection *got_s = htab->plt_got; /* If this is the first .plt entry, make room for the special first entry. */ if (s->size == 0) s->size = plt_entry_size; - h->plt.offset = s->size; + if (use_plt_got) + eh->plt_got.offset = got_s->size; + else + h->plt.offset = s->size; /* If this symbol is not defined in a regular file, and we are not generating a shared library, then set the symbol to this @@ -2230,20 +2317,36 @@ elf_i386_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf) if (! info->shared && !h->def_regular) { - h->root.u.def.section = s; - h->root.u.def.value = h->plt.offset; + if (use_plt_got) + { + /* We need to make a call to the entry of the GOT PLT + instead of regular PLT entry. */ + h->root.u.def.section = got_s; + h->root.u.def.value = eh->plt_got.offset; + } + else + { + h->root.u.def.section = s; + h->root.u.def.value = h->plt.offset; + } } /* Make room for this entry. */ - s->size += plt_entry_size; + if (use_plt_got) + got_s->size += sizeof (elf_i386_got_plt_entry); + else + { + s->size += plt_entry_size; - /* We also need to make an entry in the .got.plt section, which - will be placed in the .got section by the linker script. */ - htab->elf.sgotplt->size += 4; + /* We also need to make an entry in the .got.plt section, + which will be placed in the .got section by the linker + script. */ + htab->elf.sgotplt->size += 4; - /* We also need to make an entry in the .rel.plt section. */ - htab->elf.srelplt->size += sizeof (Elf32_External_Rel); - htab->elf.srelplt->reloc_count++; + /* We also need to make an entry in the .rel.plt section. */ + htab->elf.srelplt->size += sizeof (Elf32_External_Rel); + htab->elf.srelplt->reloc_count++; + } if (get_elf_i386_backend_data (info->output_bfd)->is_vxworks && !info->shared) @@ -2886,6 +2989,7 @@ elf_i386_size_dynamic_sections (bfd *output_bfd, struct bfd_link_info *info) else if (s == htab->elf.sgotplt || s == htab->elf.iplt || s == htab->elf.igotplt + || s == htab->plt_got || s == htab->plt_eh_frame || s == htab->sdynbss) { @@ -3183,15 +3287,17 @@ elf_i386_relocate_section (bfd *output_bfd, reloc_howto_type *howto; unsigned long r_symndx; struct elf_link_hash_entry *h; + struct elf_i386_link_hash_entry *eh; Elf_Internal_Sym *sym; asection *sec; - bfd_vma off, offplt; + bfd_vma off, offplt, plt_offset; bfd_vma relocation; bfd_boolean unresolved_reloc; bfd_reloc_status_type r; unsigned int indx; int tls_type; bfd_vma st_size; + asection *resolved_plt; r_type = ELF32_R_TYPE (rel->r_info); if (r_type == R_386_GNU_VTINHERIT @@ -3665,7 +3771,9 @@ elf_i386_relocate_section (bfd *output_bfd, if (h == NULL) break; - if (h->plt.offset == (bfd_vma) -1 + eh = (struct elf_i386_link_hash_entry *) h; + if ((h->plt.offset == (bfd_vma) -1 + && eh->plt_got.offset == (bfd_vma) -1) || htab->elf.splt == NULL) { /* We didn't make a PLT entry for this symbol. This @@ -3674,9 +3782,20 @@ elf_i386_relocate_section (bfd *output_bfd, break; } - relocation = (htab->elf.splt->output_section->vma - + htab->elf.splt->output_offset - + h->plt.offset); + if (h->plt.offset != (bfd_vma) -1) + { + resolved_plt = htab->elf.splt; + plt_offset = h->plt.offset; + } + else + { + resolved_plt = htab->plt_got; + plt_offset = eh->plt_got.offset; + } + + relocation = (resolved_plt->output_section->vma + + resolved_plt->output_offset + + plt_offset); unresolved_reloc = FALSE; break; @@ -4427,6 +4546,7 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd, struct elf_i386_link_hash_table *htab; unsigned plt_entry_size; const struct elf_i386_backend_data *abed; + struct elf_i386_link_hash_entry *eh; htab = elf_i386_hash_table (info); if (htab == NULL) @@ -4435,6 +4555,8 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd, abed = get_elf_i386_backend_data (output_bfd); plt_entry_size = GET_PLT_ENTRY_SIZE (output_bfd); + eh = (struct elf_i386_link_hash_entry *) h; + if (h->plt.offset != (bfd_vma) -1) { bfd_vma plt_index; @@ -4599,21 +4721,65 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd, plt->contents + h->plt.offset + abed->plt->plt_plt_offset); } + } + else if (eh->plt_got.offset != (bfd_vma) -1) + { + bfd_vma got_offset, plt_offset; + asection *plt, *got, *gotplt; + const bfd_byte *got_plt_entry; + + /* Offset of displacement of the indirect jump. */ + bfd_vma plt_got_offset = 2; - if (!h->def_regular) + /* Set the entry in the GOT procedure linkage table. */ + plt = htab->plt_got; + got = htab->elf.sgot; + gotplt = htab->elf.sgotplt; + got_offset = h->got.offset; + + if (got_offset == (bfd_vma) -1 + || plt == NULL + || got == NULL + || gotplt == NULL) + abort (); + + /* Fill in the entry in the GOT procedure linkage table. */ + if (! info->shared) { - /* Mark the symbol as undefined, rather than as defined in - the .plt section. Leave the value if there were any - relocations where pointer equality matters (this is a clue - for the dynamic linker, to make function pointer - comparisons work between an application and shared - library), otherwise set it to zero. If a function is only - called from a binary, there is no need to slow down - shared libraries because of that. */ - sym->st_shndx = SHN_UNDEF; - if (!h->pointer_equality_needed) - sym->st_value = 0; + got_plt_entry = elf_i386_got_plt_entry; + got_offset += got->output_section->vma + got->output_offset; } + else + { + got_plt_entry = elf_i386_pic_got_plt_entry; + got_offset += (got->output_section->vma + + got->output_offset + - gotplt->output_section->vma + - gotplt->output_offset); + } + + plt_offset = eh->plt_got.offset; + memcpy (plt->contents + plt_offset, got_plt_entry, + sizeof (elf_i386_got_plt_entry)); + bfd_put_32 (output_bfd, got_offset, + plt->contents + plt_offset + plt_got_offset); + } + + if (!h->def_regular + && (h->plt.offset != (bfd_vma) -1 + || eh->plt_got.offset != (bfd_vma) -1)) + { + /* Mark the symbol as undefined, rather than as defined in + the .plt section. Leave the value if there were any + relocations where pointer equality matters (this is a clue + for the dynamic linker, to make function pointer + comparisons work between an application and shared + library), otherwise set it to zero. If a function is only + called from a binary, there is no need to slow down + shared libraries because of that. */ + sym->st_shndx = SHN_UNDEF; + if (!h->pointer_equality_needed) + sym->st_value = 0; } if (h->got.offset != (bfd_vma) -1 |