mirror of
https://github.com/KolibriOS/kolibrios.git
synced 2024-12-12 09:57:05 +03:00
3b53803119
git-svn-id: svn://kolibrios.org@6324 a494cfbc-eb01-0410-851d-a64ba20cac60
401 lines
12 KiB
C
401 lines
12 KiB
C
/* ELF STT_GNU_IFUNC support.
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Copyright (C) 2009-2015 Free Software Foundation, Inc.
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This file is part of BFD, the Binary File Descriptor library.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "sysdep.h"
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#include "bfd.h"
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#include "bfdlink.h"
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#include "libbfd.h"
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#define ARCH_SIZE 0
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#include "elf-bfd.h"
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#include "safe-ctype.h"
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#include "libiberty.h"
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#include "objalloc.h"
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/* Create sections needed by STT_GNU_IFUNC symbol. */
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bfd_boolean
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_bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
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{
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flagword flags, pltflags;
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asection *s;
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const struct elf_backend_data *bed = get_elf_backend_data (abfd);
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struct elf_link_hash_table *htab = elf_hash_table (info);
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if (htab->irelifunc != NULL || htab->iplt != NULL)
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return TRUE;
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flags = bed->dynamic_sec_flags;
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pltflags = flags;
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if (bed->plt_not_loaded)
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/* We do not clear SEC_ALLOC here because we still want the OS to
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allocate space for the section; it's just that there's nothing
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to read in from the object file. */
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pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
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else
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pltflags |= SEC_ALLOC | SEC_CODE | SEC_LOAD;
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if (bed->plt_readonly)
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pltflags |= SEC_READONLY;
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if (bfd_link_pic (info))
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{
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/* We need to create .rel[a].ifunc for shared objects. */
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const char *rel_sec = (bed->rela_plts_and_copies_p
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? ".rela.ifunc" : ".rel.ifunc");
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s = bfd_make_section_with_flags (abfd, rel_sec,
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flags | SEC_READONLY);
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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return FALSE;
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htab->irelifunc = s;
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}
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else
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{
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/* We need to create .iplt, .rel[a].iplt, .igot and .igot.plt
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for static executables. */
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s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
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return FALSE;
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htab->iplt = s;
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s = bfd_make_section_with_flags (abfd,
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(bed->rela_plts_and_copies_p
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? ".rela.iplt" : ".rel.iplt"),
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flags | SEC_READONLY);
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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return FALSE;
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htab->irelplt = s;
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/* We don't need the .igot section if we have the .igot.plt
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section. */
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if (bed->want_got_plt)
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s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
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else
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s = bfd_make_section_with_flags (abfd, ".igot", flags);
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if (s == NULL
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|| !bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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return FALSE;
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htab->igotplt = s;
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}
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return TRUE;
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}
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/* Allocate space in .plt, .got and associated reloc sections for
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dynamic relocs against a STT_GNU_IFUNC symbol definition. */
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bfd_boolean
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_bfd_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
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struct elf_link_hash_entry *h,
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struct elf_dyn_relocs **head,
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unsigned int plt_entry_size,
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unsigned int plt_header_size,
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unsigned int got_entry_size)
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{
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asection *plt, *gotplt, *relplt;
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struct elf_dyn_relocs *p;
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unsigned int sizeof_reloc;
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const struct elf_backend_data *bed;
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struct elf_link_hash_table *htab;
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/* When a shared library references a STT_GNU_IFUNC symbol defined
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in executable, the address of the resolved function may be used.
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But in non-shared executable, the address of its .plt slot may
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be used. Pointer equality may not work correctly. PIE should
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be used if pointer equality is required here. */
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if (!bfd_link_pic (info)
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&& (h->dynindx != -1
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|| info->export_dynamic)
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&& h->pointer_equality_needed)
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{
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info->callbacks->einfo
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(_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
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"equality in `%B' can not be used when making an "
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"executable; recompile with -fPIE and relink with -pie\n"),
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h->root.root.string,
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h->root.u.def.section->owner);
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bfd_set_error (bfd_error_bad_value);
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return FALSE;
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}
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htab = elf_hash_table (info);
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/* When building shared library, we need to handle the case where it is
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marked with regular reference, but not non-GOT reference since the
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non-GOT reference bit may not be set here. */
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if (bfd_link_pic (info) && !h->non_got_ref && h->ref_regular)
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for (p = *head; p != NULL; p = p->next)
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if (p->count)
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{
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h->non_got_ref = 1;
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goto keep;
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}
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/* Support garbage collection against STT_GNU_IFUNC symbols. */
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if (h->plt.refcount <= 0 && h->got.refcount <= 0)
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{
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h->got = htab->init_got_offset;
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h->plt = htab->init_plt_offset;
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*head = NULL;
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return TRUE;
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}
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/* Return and discard space for dynamic relocations against it if
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it is never referenced in a non-shared object. */
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if (!h->ref_regular)
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{
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if (h->plt.refcount > 0
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|| h->got.refcount > 0)
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abort ();
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h->got = htab->init_got_offset;
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h->plt = htab->init_plt_offset;
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*head = NULL;
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return TRUE;
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}
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keep:
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bed = get_elf_backend_data (info->output_bfd);
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if (bed->rela_plts_and_copies_p)
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sizeof_reloc = bed->s->sizeof_rela;
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else
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sizeof_reloc = bed->s->sizeof_rel;
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/* When building a static executable, use .iplt, .igot.plt and
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.rel[a].iplt sections for STT_GNU_IFUNC symbols. */
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if (htab->splt != NULL)
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{
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plt = htab->splt;
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gotplt = htab->sgotplt;
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relplt = htab->srelplt;
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/* If this is the first .plt entry, make room for the special
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first entry. */
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if (plt->size == 0)
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plt->size += plt_header_size;
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}
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else
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{
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plt = htab->iplt;
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gotplt = htab->igotplt;
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relplt = htab->irelplt;
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}
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/* Don't update value of STT_GNU_IFUNC symbol to PLT. We need
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the original value for R_*_IRELATIVE. */
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h->plt.offset = plt->size;
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/* Make room for this entry in the .plt/.iplt section. */
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plt->size += plt_entry_size;
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/* We also need to make an entry in the .got.plt/.got.iplt section,
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which will be placed in the .got section by the linker script. */
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gotplt->size += got_entry_size;
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/* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
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section. */
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relplt->size += sizeof_reloc;
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relplt->reloc_count++;
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/* We need dynamic relocation for STT_GNU_IFUNC symbol only when
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there is a non-GOT reference in a shared object. */
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if (!bfd_link_pic (info)
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|| !h->non_got_ref)
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*head = NULL;
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/* Finally, allocate space. */
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p = *head;
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if (p != NULL)
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{
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bfd_size_type count = 0;
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do
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{
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count += p->count;
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p = p->next;
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}
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while (p != NULL);
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htab->irelifunc->size += count * sizeof_reloc;
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}
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/* For STT_GNU_IFUNC symbol, .got.plt has the real function address
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and .got has the PLT entry adddress. We will load the GOT entry
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with the PLT entry in finish_dynamic_symbol if it is used. For
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branch, it uses .got.plt. For symbol value,
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1. Use .got.plt in a shared object if it is forced local or not
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dynamic.
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2. Use .got.plt in a non-shared object if pointer equality isn't
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needed.
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3. Use .got.plt in PIE.
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4. Use .got.plt if .got isn't used.
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5. Otherwise use .got so that it can be shared among different
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objects at run-time.
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We only need to relocate .got entry in shared object. */
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if (h->got.refcount <= 0
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|| (bfd_link_pic (info)
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&& (h->dynindx == -1
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|| h->forced_local))
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|| (!bfd_link_pic (info)
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&& !h->pointer_equality_needed)
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|| bfd_link_pie (info)
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|| htab->sgot == NULL)
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{
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/* Use .got.plt. */
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h->got.offset = (bfd_vma) -1;
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}
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else
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{
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h->got.offset = htab->sgot->size;
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htab->sgot->size += got_entry_size;
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if (bfd_link_pic (info))
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htab->srelgot->size += sizeof_reloc;
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}
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return TRUE;
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}
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/* Similar to _bfd_elf_get_synthetic_symtab, optimized for unsorted PLT
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entries. PLT is the PLT section. PLT_SYM_VAL is a function pointer
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which returns an array of PLT entry symbol values. */
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long
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_bfd_elf_ifunc_get_synthetic_symtab
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(bfd *abfd, long symcount ATTRIBUTE_UNUSED,
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asymbol **syms ATTRIBUTE_UNUSED, long dynsymcount, asymbol **dynsyms,
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asymbol **ret, asection *plt,
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bfd_vma *(*get_plt_sym_val) (bfd *, asymbol **, asection *, asection *))
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{
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const struct elf_backend_data *bed = get_elf_backend_data (abfd);
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asection *relplt;
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asymbol *s;
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const char *relplt_name;
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bfd_boolean (*slurp_relocs) (bfd *, asection *, asymbol **, bfd_boolean);
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arelent *p;
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long count, i, n;
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size_t size;
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Elf_Internal_Shdr *hdr;
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char *names;
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bfd_vma *plt_sym_val;
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*ret = NULL;
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if (plt == NULL)
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return 0;
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if ((abfd->flags & (DYNAMIC | EXEC_P)) == 0)
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return 0;
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if (dynsymcount <= 0)
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return 0;
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relplt_name = bed->relplt_name;
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if (relplt_name == NULL)
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relplt_name = bed->rela_plts_and_copies_p ? ".rela.plt" : ".rel.plt";
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relplt = bfd_get_section_by_name (abfd, relplt_name);
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if (relplt == NULL)
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return 0;
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hdr = &elf_section_data (relplt)->this_hdr;
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if (hdr->sh_link != elf_dynsymtab (abfd)
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|| (hdr->sh_type != SHT_REL && hdr->sh_type != SHT_RELA))
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return 0;
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slurp_relocs = get_elf_backend_data (abfd)->s->slurp_reloc_table;
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if (! (*slurp_relocs) (abfd, relplt, dynsyms, TRUE))
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return -1;
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count = relplt->size / hdr->sh_entsize;
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size = count * sizeof (asymbol);
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p = relplt->relocation;
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for (i = 0; i < count; i++, p += bed->s->int_rels_per_ext_rel)
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{
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size += strlen ((*p->sym_ptr_ptr)->name) + sizeof ("@plt");
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if (p->addend != 0)
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{
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#ifdef BFD64
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size += sizeof ("+0x") - 1 + 8 + 8 * (bed->s->elfclass == ELFCLASS64);
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#else
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size += sizeof ("+0x") - 1 + 8;
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#endif
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}
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}
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plt_sym_val = get_plt_sym_val (abfd, dynsyms, plt, relplt);
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if (plt_sym_val == NULL)
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return -1;
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s = *ret = (asymbol *) bfd_malloc (size);
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if (s == NULL)
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{
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free (plt_sym_val);
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return -1;
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}
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names = (char *) (s + count);
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p = relplt->relocation;
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n = 0;
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for (i = 0; i < count; i++, p += bed->s->int_rels_per_ext_rel)
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{
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size_t len;
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bfd_vma addr;
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addr = plt_sym_val[i];
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if (addr == (bfd_vma) -1)
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continue;
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*s = **p->sym_ptr_ptr;
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/* Undefined syms won't have BSF_LOCAL or BSF_GLOBAL set. Since
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we are defining a symbol, ensure one of them is set. */
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if ((s->flags & BSF_LOCAL) == 0)
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s->flags |= BSF_GLOBAL;
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s->flags |= BSF_SYNTHETIC;
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s->section = plt;
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s->value = addr - plt->vma;
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s->name = names;
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s->udata.p = NULL;
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len = strlen ((*p->sym_ptr_ptr)->name);
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memcpy (names, (*p->sym_ptr_ptr)->name, len);
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names += len;
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if (p->addend != 0)
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{
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char buf[30], *a;
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memcpy (names, "+0x", sizeof ("+0x") - 1);
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names += sizeof ("+0x") - 1;
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bfd_sprintf_vma (abfd, buf, p->addend);
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for (a = buf; *a == '0'; ++a)
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;
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len = strlen (a);
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memcpy (names, a, len);
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names += len;
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}
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memcpy (names, "@plt", sizeof ("@plt"));
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names += sizeof ("@plt");
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++s, ++n;
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}
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free (plt_sym_val);
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return n;
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}
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