--- /dev/null
+/* ELF STT_GNU_IFUNC support.
+ Copyright 2009
+ Free Software Foundation, Inc.
+
+ This file is part of BFD, the Binary File Descriptor library.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+ MA 02110-1301, USA. */
+
+#include "sysdep.h"
+#include "bfd.h"
+#include "bfdlink.h"
+#include "libbfd.h"
+#define ARCH_SIZE 0
+#include "elf-bfd.h"
+#include "safe-ctype.h"
+#include "libiberty.h"
+#include "objalloc.h"
+
+/* Create sections needed by STT_GNU_IFUNC symbol. */
+
+bfd_boolean
+_bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
+{
+ flagword flags, pltflags;
+ asection *s;
+ const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+ struct elf_link_hash_table *htab = elf_hash_table (info);
+
+ if (htab->irelifunc != NULL || htab->iplt != NULL)
+ return TRUE;
+
+ flags = bed->dynamic_sec_flags;
+ pltflags = flags;
+ if (bed->plt_not_loaded)
+ /* We do not clear SEC_ALLOC here because we still want the OS to
+ allocate space for the section; it's just that there's nothing
+ to read in from the object file. */
+ pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
+ else
+ pltflags |= SEC_ALLOC | SEC_CODE | SEC_LOAD;
+ if (bed->plt_readonly)
+ pltflags |= SEC_READONLY;
+
+ if (info->shared)
+ {
+ /* We need to create .rel[a].ifunc for shared objects. */
+ const char *rel_sec = (bed->rela_plts_and_copies_p
+ ? ".rela.ifunc" : ".rel.ifunc");
+
+ s = bfd_make_section_with_flags (abfd, rel_sec,
+ flags | SEC_READONLY);
+ if (s == NULL
+ || ! bfd_set_section_alignment (abfd, s,
+ bed->s->log_file_align))
+ return FALSE;
+ htab->irelifunc = s;
+ }
+ else
+ {
+ /* We need to create .iplt, .rel[a].iplt, .igot and .igot.plt
+ for static executables. */
+ s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
+ if (s == NULL
+ || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
+ return FALSE;
+ htab->iplt = s;
+
+ s = bfd_make_section_with_flags (abfd,
+ (bed->rela_plts_and_copies_p
+ ? ".rela.iplt" : ".rel.iplt"),
+ flags | SEC_READONLY);
+ if (s == NULL
+ || ! bfd_set_section_alignment (abfd, s,
+ bed->s->log_file_align))
+ return FALSE;
+ htab->irelplt = s;
+
+ /* We don't need the .igot section if we have the .igot.plt
+ section. */
+ if (bed->want_got_plt)
+ s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
+ else
+ s = bfd_make_section_with_flags (abfd, ".igot", flags);
+ if (s == NULL
+ || !bfd_set_section_alignment (abfd, s,
+ bed->s->log_file_align))
+ return FALSE;
+ htab->igotplt = s;
+ }
+
+ return TRUE;
+}
+
+/* For a STT_GNU_IFUNC symbol, create a dynamic reloc section, SRELOC,
+ for the input section, SEC, and append this reloc to HEAD. */
+
+asection *
+_bfd_elf_create_ifunc_dyn_reloc (bfd *abfd, struct bfd_link_info *info,
+ asection *sec, asection *sreloc,
+ struct elf_dyn_relocs **head)
+{
+ struct elf_dyn_relocs *p;
+ struct elf_link_hash_table *htab = elf_hash_table (info);
+
+ if (sreloc == NULL)
+ {
+ const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+
+ if (htab->dynobj == NULL)
+ htab->dynobj = abfd;
+
+ sreloc = _bfd_elf_make_dynamic_reloc_section (sec, htab->dynobj,
+ bed->s->log_file_align,
+ abfd,
+ bed->rela_plts_and_copies_p);
+ if (sreloc == NULL)
+ return NULL;
+ }
+
+ p = *head;
+ if (p == NULL || p->sec != sec)
+ {
+ bfd_size_type amt = sizeof *p;
+
+ p = ((struct elf_dyn_relocs *) bfd_alloc (htab->dynobj, amt));
+ if (p == NULL)
+ return NULL;
+ p->next = *head;
+ *head = p;
+ p->sec = sec;
+ p->count = 0;
+ p->pc_count = 0;
+ }
+ p->count += 1;
+
+ return sreloc;
+}
+
+/* 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 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);
+
+ /* 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;
+ }
+
+ 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_entry_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. */
+ for (p = *head; p != NULL; p = p->next)
+ htab->irelifunc->size += p->count * sizeof_reloc;
+
+ /* For STT_GNU_IFUNC symbol, .got.plt has the real function addres
+ 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 ((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;
+}
projects / msp430-binutils.git / blobdiff