/* ELF STT_GNU_IFUNC support.
- Copyright 2009
- Free Software Foundation, Inc.
+ Copyright (C) 2009-2015 Free Software Foundation, Inc.
This file is part of BFD, the Binary File Descriptor library.
return TRUE;
}
+
+/* Allocate space in .plt, .got and associated reloc sections for
+ dynamic relocs against a STT_GNU_IFUNC symbol definition. */
+
+bfd_boolean
+_bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
+ struct elf_link_hash_entry *h,
+ struct elf_dyn_relocs **head,
+ unsigned int plt_entry_size,
+ unsigned int plt_header_size,
+ unsigned int got_entry_size)
+{
+ asection *plt, *gotplt, *relplt;
+ struct elf_dyn_relocs *p;
+ unsigned int sizeof_reloc;
+ const struct elf_backend_data *bed;
+ struct elf_link_hash_table *htab;
+
+ /* When a shared library references a STT_GNU_IFUNC symbol defined
+ in executable, the address of the resolved function may be used.
+ But in non-shared executable, the address of its .plt slot may
+ be used. Pointer equality may not work correctly. PIE should
+ be used if pointer equality is required here. */
+ if (!info->shared
+ && (h->dynindx != -1
+ || info->export_dynamic)
+ && h->pointer_equality_needed)
+ {
+ info->callbacks->einfo
+ (_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
+ "equality in `%B' can not be used when making an "
+ "executable; recompile with -fPIE and relink with -pie\n"),
+ h->root.root.string,
+ h->root.u.def.section->owner);
+ bfd_set_error (bfd_error_bad_value);
+ return FALSE;
+ }
+
+ htab = elf_hash_table (info);
+
+ /* When building shared library, we need to handle the case where it is
+ marked with regular reference, but not non-GOT reference since the
+ non-GOT reference bit may not be set here. */
+ if (info->shared && !h->non_got_ref && h->ref_regular)
+ for (p = *head; p != NULL; p = p->next)
+ if (p->count)
+ {
+ h->non_got_ref = 1;
+ goto keep;
+ }
+
+ /* Support garbage collection against STT_GNU_IFUNC symbols. */
+ if (h->plt.refcount <= 0 && h->got.refcount <= 0)
+ {
+ h->got = htab->init_got_offset;
+ h->plt = htab->init_plt_offset;
+ *head = NULL;
+ return TRUE;
+ }
+
+ /* Return and discard space for dynamic relocations against it if
+ it is never referenced in a non-shared object. */
+ if (!h->ref_regular)
+ {
+ if (h->plt.refcount > 0
+ || h->got.refcount > 0)
+ abort ();
+ h->got = htab->init_got_offset;
+ h->plt = htab->init_plt_offset;
+ *head = NULL;
+ return TRUE;
+ }
+
+keep:
+ bed = get_elf_backend_data (info->output_bfd);
+ if (bed->rela_plts_and_copies_p)
+ sizeof_reloc = bed->s->sizeof_rela;
+ else
+ sizeof_reloc = bed->s->sizeof_rel;
+
+ /* When building a static executable, use .iplt, .igot.plt and
+ .rel[a].iplt sections for STT_GNU_IFUNC symbols. */
+ if (htab->splt != NULL)
+ {
+ plt = htab->splt;
+ gotplt = htab->sgotplt;
+ relplt = htab->srelplt;
+
+ /* If this is the first .plt entry, make room for the special
+ first entry. */
+ if (plt->size == 0)
+ plt->size += plt_header_size;
+ }
+ else
+ {
+ plt = htab->iplt;
+ gotplt = htab->igotplt;
+ relplt = htab->irelplt;
+ }
+
+ /* Don't update value of STT_GNU_IFUNC symbol to PLT. We need
+ the original value for R_*_IRELATIVE. */
+ h->plt.offset = plt->size;
+
+ /* Make room for this entry in the .plt/.iplt section. */
+ plt->size += plt_entry_size;
+
+ /* We also need to make an entry in the .got.plt/.got.iplt section,
+ which will be placed in the .got section by the linker script. */
+ gotplt->size += got_entry_size;
+
+ /* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
+ section. */
+ relplt->size += sizeof_reloc;
+ relplt->reloc_count++;
+
+ /* We need dynamic relocation for STT_GNU_IFUNC symbol only when
+ there is a non-GOT reference in a shared object. */
+ if (!info->shared
+ || !h->non_got_ref)
+ *head = NULL;
+
+ /* Finally, allocate space. */
+ p = *head;
+ if (p != NULL)
+ {
+ bfd_size_type count = 0;
+ do
+ {
+ count += p->count;
+ p = p->next;
+ }
+ while (p != NULL);
+ htab->irelifunc->size += count * sizeof_reloc;
+ }
+
+ /* For STT_GNU_IFUNC symbol, .got.plt has the real function address
+ and .got has the PLT entry adddress. We will load the GOT entry
+ with the PLT entry in finish_dynamic_symbol if it is used. For
+ branch, it uses .got.plt. For symbol value,
+ 1. Use .got.plt in a shared object if it is forced local or not
+ dynamic.
+ 2. Use .got.plt in a non-shared object if pointer equality isn't
+ needed.
+ 3. Use .got.plt in PIE.
+ 4. Use .got.plt if .got isn't used.
+ 5. Otherwise use .got so that it can be shared among different
+ objects at run-time.
+ We only need to relocate .got entry in shared object. */
+ if (h->got.refcount <= 0
+ || (info->shared
+ && (h->dynindx == -1
+ || h->forced_local))
+ || (!info->shared
+ && !h->pointer_equality_needed)
+ || (info->executable && info->shared)
+ || htab->sgot == NULL)
+ {
+ /* Use .got.plt. */
+ h->got.offset = (bfd_vma) -1;
+ }
+ else
+ {
+ h->got.offset = htab->sgot->size;
+ htab->sgot->size += got_entry_size;
+ if (info->shared)
+ htab->srelgot->size += sizeof_reloc;
+ }
+
+ return TRUE;
+}
+
+/* Similar to _bfd_elf_get_synthetic_symtab, optimized for unsorted PLT
+ entries. PLT is the PLT section. PLT_SYM_VAL is a function pointer
+ which returns an array of PLT entry symbol values. */
+
+long
+_bfd_elf_ifunc_get_synthetic_symtab
+ (bfd *abfd, long symcount ATTRIBUTE_UNUSED,
+ asymbol **syms ATTRIBUTE_UNUSED, long dynsymcount, asymbol **dynsyms,
+ asymbol **ret, asection *plt,
+ bfd_vma *(*get_plt_sym_val) (bfd *, asymbol **, asection *, asection *))
+{
+ const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+ asection *relplt;
+ asymbol *s;
+ const char *relplt_name;
+ bfd_boolean (*slurp_relocs) (bfd *, asection *, asymbol **, bfd_boolean);
+ arelent *p;
+ long count, i, n;
+ size_t size;
+ Elf_Internal_Shdr *hdr;
+ char *names;
+ bfd_vma *plt_sym_val;
+
+ *ret = NULL;
+
+ if (plt == NULL)
+ return 0;
+
+ if ((abfd->flags & (DYNAMIC | EXEC_P)) == 0)
+ return 0;
+
+ if (dynsymcount <= 0)
+ return 0;
+
+ relplt_name = bed->relplt_name;
+ if (relplt_name == NULL)
+ relplt_name = bed->rela_plts_and_copies_p ? ".rela.plt" : ".rel.plt";
+ relplt = bfd_get_section_by_name (abfd, relplt_name);
+ if (relplt == NULL)
+ return 0;
+
+ hdr = &elf_section_data (relplt)->this_hdr;
+ if (hdr->sh_link != elf_dynsymtab (abfd)
+ || (hdr->sh_type != SHT_REL && hdr->sh_type != SHT_RELA))
+ return 0;
+
+ slurp_relocs = get_elf_backend_data (abfd)->s->slurp_reloc_table;
+ if (! (*slurp_relocs) (abfd, relplt, dynsyms, TRUE))
+ return -1;
+
+ count = relplt->size / hdr->sh_entsize;
+ size = count * sizeof (asymbol);
+ p = relplt->relocation;
+ for (i = 0; i < count; i++, p += bed->s->int_rels_per_ext_rel)
+ {
+ size += strlen ((*p->sym_ptr_ptr)->name) + sizeof ("@plt");
+ if (p->addend != 0)
+ {
+#ifdef BFD64
+ size += sizeof ("+0x") - 1 + 8 + 8 * (bed->s->elfclass == ELFCLASS64);
+#else
+ size += sizeof ("+0x") - 1 + 8;
+#endif
+ }
+ }
+
+ plt_sym_val = get_plt_sym_val (abfd, dynsyms, plt, relplt);
+ if (plt_sym_val == NULL)
+ return -1;
+
+ s = *ret = (asymbol *) bfd_malloc (size);
+ if (s == NULL)
+ {
+ free (plt_sym_val);
+ return -1;
+ }
+
+ names = (char *) (s + count);
+ p = relplt->relocation;
+ n = 0;
+ for (i = 0; i < count; i++, p += bed->s->int_rels_per_ext_rel)
+ {
+ size_t len;
+ bfd_vma addr;
+
+ addr = plt_sym_val[i];
+ if (addr == (bfd_vma) -1)
+ continue;
+
+ *s = **p->sym_ptr_ptr;
+ /* Undefined syms won't have BSF_LOCAL or BSF_GLOBAL set. Since
+ we are defining a symbol, ensure one of them is set. */
+ if ((s->flags & BSF_LOCAL) == 0)
+ s->flags |= BSF_GLOBAL;
+ s->flags |= BSF_SYNTHETIC;
+ s->section = plt;
+ s->value = addr - plt->vma;
+ s->name = names;
+ s->udata.p = NULL;
+ len = strlen ((*p->sym_ptr_ptr)->name);
+ memcpy (names, (*p->sym_ptr_ptr)->name, len);
+ names += len;
+ if (p->addend != 0)
+ {
+ char buf[30], *a;
+
+ memcpy (names, "+0x", sizeof ("+0x") - 1);
+ names += sizeof ("+0x") - 1;
+ bfd_sprintf_vma (abfd, buf, p->addend);
+ for (a = buf; *a == '0'; ++a)
+ ;
+ len = strlen (a);
+ memcpy (names, a, len);
+ names += len;
+ }
+ memcpy (names, "@plt", sizeof ("@plt"));
+ names += sizeof ("@plt");
+ ++s, ++n;
+ }
+
+ free (plt_sym_val);
+
+ return n;
+}
projects / deliverable / binutils-gdb.git / blobdiff