/* ELF STT_GNU_IFUNC support.
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/* ELF STT_GNU_IFUNC support.
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Copyright 2009
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Copyright 2009
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Free Software Foundation, Inc.
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Free Software Foundation, Inc.
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This file is part of BFD, the Binary File Descriptor library.
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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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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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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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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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(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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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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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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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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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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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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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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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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MA 02110-1301, USA. */
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MA 02110-1301, USA. */
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|
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#include "sysdep.h"
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#include "sysdep.h"
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#include "bfd.h"
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#include "bfd.h"
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#include "bfdlink.h"
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#include "bfdlink.h"
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#include "libbfd.h"
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#include "libbfd.h"
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#define ARCH_SIZE 0
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#define ARCH_SIZE 0
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#include "elf-bfd.h"
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#include "elf-bfd.h"
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#include "safe-ctype.h"
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#include "safe-ctype.h"
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#include "libiberty.h"
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#include "libiberty.h"
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#include "objalloc.h"
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#include "objalloc.h"
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|
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/* Create sections needed by STT_GNU_IFUNC symbol. */
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/* Create sections needed by STT_GNU_IFUNC symbol. */
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bfd_boolean
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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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_bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
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{
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{
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flagword flags, pltflags;
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flagword flags, pltflags;
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asection *s;
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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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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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struct elf_link_hash_table *htab = elf_hash_table (info);
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|
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if (htab->irelifunc != NULL || htab->iplt != NULL)
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if (htab->irelifunc != NULL || htab->iplt != NULL)
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return TRUE;
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return TRUE;
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|
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flags = bed->dynamic_sec_flags;
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flags = bed->dynamic_sec_flags;
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pltflags = flags;
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pltflags = flags;
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if (bed->plt_not_loaded)
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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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/* 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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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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to read in from the object file. */
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pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
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pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
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else
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else
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pltflags |= SEC_ALLOC | SEC_CODE | SEC_LOAD;
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pltflags |= SEC_ALLOC | SEC_CODE | SEC_LOAD;
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if (bed->plt_readonly)
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if (bed->plt_readonly)
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pltflags |= SEC_READONLY;
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pltflags |= SEC_READONLY;
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if (info->shared)
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if (info->shared)
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{
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{
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/* We need to create .rel[a].ifunc for shared objects. */
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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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const char *rel_sec = (bed->rela_plts_and_copies_p
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? ".rela.ifunc" : ".rel.ifunc");
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? ".rela.ifunc" : ".rel.ifunc");
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|
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s = bfd_make_section_with_flags (abfd, rel_sec,
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s = bfd_make_section_with_flags (abfd, rel_sec,
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flags | SEC_READONLY);
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flags | SEC_READONLY);
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if (s == NULL
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s,
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|| ! bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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bed->s->log_file_align))
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return FALSE;
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return FALSE;
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htab->irelifunc = s;
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htab->irelifunc = s;
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}
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}
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else
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else
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{
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{
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/* We need to create .iplt, .rel[a].iplt, .igot and .igot.plt
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/* We need to create .iplt, .rel[a].iplt, .igot and .igot.plt
|
for static executables. */
|
for static executables. */
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s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
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s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
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if (s == NULL
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
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|| ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
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return FALSE;
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return FALSE;
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htab->iplt = s;
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htab->iplt = s;
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|
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s = bfd_make_section_with_flags (abfd,
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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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(bed->rela_plts_and_copies_p
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? ".rela.iplt" : ".rel.iplt"),
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? ".rela.iplt" : ".rel.iplt"),
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flags | SEC_READONLY);
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flags | SEC_READONLY);
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if (s == NULL
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if (s == NULL
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|| ! bfd_set_section_alignment (abfd, s,
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|| ! bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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bed->s->log_file_align))
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return FALSE;
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return FALSE;
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htab->irelplt = s;
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htab->irelplt = s;
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|
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/* We don't need the .igot section if we have the .igot.plt
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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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section. */
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if (bed->want_got_plt)
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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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s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
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else
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else
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s = bfd_make_section_with_flags (abfd, ".igot", flags);
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s = bfd_make_section_with_flags (abfd, ".igot", flags);
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if (s == NULL
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if (s == NULL
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|| !bfd_set_section_alignment (abfd, s,
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|| !bfd_set_section_alignment (abfd, s,
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bed->s->log_file_align))
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bed->s->log_file_align))
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return FALSE;
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return FALSE;
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htab->igotplt = s;
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htab->igotplt = s;
|
}
|
}
|
|
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return TRUE;
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return TRUE;
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}
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}
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|
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/* For a STT_GNU_IFUNC symbol, create a dynamic reloc section, SRELOC,
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/* For a STT_GNU_IFUNC symbol, create a dynamic reloc section, SRELOC,
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for the input section, SEC, and append this reloc to HEAD. */
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for the input section, SEC, and append this reloc to HEAD. */
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|
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asection *
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asection *
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_bfd_elf_create_ifunc_dyn_reloc (bfd *abfd, struct bfd_link_info *info,
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_bfd_elf_create_ifunc_dyn_reloc (bfd *abfd, struct bfd_link_info *info,
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asection *sec, asection *sreloc,
|
asection *sec, asection *sreloc,
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struct elf_dyn_relocs **head)
|
struct elf_dyn_relocs **head)
|
{
|
{
|
struct elf_dyn_relocs *p;
|
struct elf_dyn_relocs *p;
|
struct elf_link_hash_table *htab = elf_hash_table (info);
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struct elf_link_hash_table *htab = elf_hash_table (info);
|
|
|
if (sreloc == NULL)
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if (sreloc == NULL)
|
{
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{
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const struct elf_backend_data *bed = get_elf_backend_data (abfd);
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const struct elf_backend_data *bed = get_elf_backend_data (abfd);
|
|
|
if (htab->dynobj == NULL)
|
if (htab->dynobj == NULL)
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htab->dynobj = abfd;
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htab->dynobj = abfd;
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|
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sreloc = _bfd_elf_make_dynamic_reloc_section (sec, htab->dynobj,
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sreloc = _bfd_elf_make_dynamic_reloc_section (sec, htab->dynobj,
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bed->s->log_file_align,
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bed->s->log_file_align,
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abfd,
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abfd,
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bed->rela_plts_and_copies_p);
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bed->rela_plts_and_copies_p);
|
if (sreloc == NULL)
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if (sreloc == NULL)
|
return NULL;
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return NULL;
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}
|
}
|
|
|
p = *head;
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p = *head;
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if (p == NULL || p->sec != sec)
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if (p == NULL || p->sec != sec)
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{
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{
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bfd_size_type amt = sizeof *p;
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bfd_size_type amt = sizeof *p;
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|
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p = ((struct elf_dyn_relocs *) bfd_alloc (htab->dynobj, amt));
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p = ((struct elf_dyn_relocs *) bfd_alloc (htab->dynobj, amt));
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if (p == NULL)
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if (p == NULL)
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return NULL;
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return NULL;
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p->next = *head;
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p->next = *head;
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*head = p;
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*head = p;
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p->sec = sec;
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p->sec = sec;
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p->count = 0;
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p->count = 0;
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p->pc_count = 0;
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p->pc_count = 0;
|
}
|
}
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p->count += 1;
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p->count += 1;
|
|
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return sreloc;
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return sreloc;
|
}
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}
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|
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/* Allocate space in .plt, .got and associated reloc sections for
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/* Allocate space in .plt, .got and associated reloc sections for
|
dynamic relocs against a STT_GNU_IFUNC symbol definition. */
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dynamic relocs against a STT_GNU_IFUNC symbol definition. */
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|
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bfd_boolean
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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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_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_link_hash_entry *h,
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struct elf_dyn_relocs **head,
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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_entry_size,
|
unsigned int got_entry_size)
|
unsigned int got_entry_size)
|
{
|
{
|
asection *plt, *gotplt, *relplt;
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asection *plt, *gotplt, *relplt;
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struct elf_dyn_relocs *p;
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struct elf_dyn_relocs *p;
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unsigned int sizeof_reloc;
|
unsigned int sizeof_reloc;
|
const struct elf_backend_data *bed;
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const struct elf_backend_data *bed;
|
struct elf_link_hash_table *htab;
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struct elf_link_hash_table *htab;
|
|
|
/* When a shared library references a STT_GNU_IFUNC symbol defined
|
/* When a shared library references a STT_GNU_IFUNC symbol defined
|
in executable, the address of the resolved function may be used.
|
in executable, the address of the resolved function may be used.
|
But in non-shared executable, the address of its .plt slot may
|
But in non-shared executable, the address of its .plt slot may
|
be used. Pointer equality may not work correctly. PIE should
|
be used. Pointer equality may not work correctly. PIE should
|
be used if pointer equality is required here. */
|
be used if pointer equality is required here. */
|
if (!info->shared
|
if (!info->shared
|
&& (h->dynindx != -1
|
&& (h->dynindx != -1
|
|| info->export_dynamic)
|
|| info->export_dynamic)
|
&& h->pointer_equality_needed)
|
&& h->pointer_equality_needed)
|
{
|
{
|
info->callbacks->einfo
|
info->callbacks->einfo
|
(_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
|
(_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
|
"equality in `%B' can not be used when making an "
|
"equality in `%B' can not be used when making an "
|
"executable; recompile with -fPIE and relink with -pie\n"),
|
"executable; recompile with -fPIE and relink with -pie\n"),
|
h->root.root.string,
|
h->root.root.string,
|
h->root.u.def.section->owner);
|
h->root.u.def.section->owner);
|
bfd_set_error (bfd_error_bad_value);
|
bfd_set_error (bfd_error_bad_value);
|
return FALSE;
|
return FALSE;
|
}
|
}
|
|
|
htab = elf_hash_table (info);
|
htab = elf_hash_table (info);
|
|
|
/* Support garbage collection against STT_GNU_IFUNC symbols. */
|
/* Support garbage collection against STT_GNU_IFUNC symbols. */
|
if (h->plt.refcount <= 0 && h->got.refcount <= 0)
|
if (h->plt.refcount <= 0 && h->got.refcount <= 0)
|
{
|
{
|
/* When building shared library, we need to handle the case
|
/* When building shared library, we need to handle the case
|
where it is marked with regular reference, but not non-GOT
|
where it is marked with regular reference, but not non-GOT
|
reference. It may happen if we didn't see STT_GNU_IFUNC
|
reference. It may happen if we didn't see STT_GNU_IFUNC
|
symbol at the time when checking relocations. */
|
symbol at the time when checking relocations. */
|
if (info->shared
|
if (info->shared
|
&& !h->non_got_ref
|
&& !h->non_got_ref
|
&& h->ref_regular)
|
&& h->ref_regular)
|
for (p = *head; p != NULL; p = p->next)
|
for (p = *head; p != NULL; p = p->next)
|
if (p->count)
|
if (p->count)
|
{
|
{
|
h->non_got_ref = 1;
|
h->non_got_ref = 1;
|
goto keep;
|
goto keep;
|
}
|
}
|
|
|
h->got = htab->init_got_offset;
|
h->got = htab->init_got_offset;
|
h->plt = htab->init_plt_offset;
|
h->plt = htab->init_plt_offset;
|
*head = NULL;
|
*head = NULL;
|
return TRUE;
|
return TRUE;
|
}
|
}
|
|
|
/* Return and discard space for dynamic relocations against it if
|
/* Return and discard space for dynamic relocations against it if
|
it is never referenced in a non-shared object. */
|
it is never referenced in a non-shared object. */
|
if (!h->ref_regular)
|
if (!h->ref_regular)
|
{
|
{
|
if (h->plt.refcount > 0
|
if (h->plt.refcount > 0
|
|| h->got.refcount > 0)
|
|| h->got.refcount > 0)
|
abort ();
|
abort ();
|
h->got = htab->init_got_offset;
|
h->got = htab->init_got_offset;
|
h->plt = htab->init_plt_offset;
|
h->plt = htab->init_plt_offset;
|
*head = NULL;
|
*head = NULL;
|
return TRUE;
|
return TRUE;
|
}
|
}
|
|
|
keep:
|
keep:
|
bed = get_elf_backend_data (info->output_bfd);
|
bed = get_elf_backend_data (info->output_bfd);
|
if (bed->rela_plts_and_copies_p)
|
if (bed->rela_plts_and_copies_p)
|
sizeof_reloc = bed->s->sizeof_rela;
|
sizeof_reloc = bed->s->sizeof_rela;
|
else
|
else
|
sizeof_reloc = bed->s->sizeof_rel;
|
sizeof_reloc = bed->s->sizeof_rel;
|
|
|
/* When building a static executable, use .iplt, .igot.plt and
|
/* When building a static executable, use .iplt, .igot.plt and
|
.rel[a].iplt sections for STT_GNU_IFUNC symbols. */
|
.rel[a].iplt sections for STT_GNU_IFUNC symbols. */
|
if (htab->splt != NULL)
|
if (htab->splt != NULL)
|
{
|
{
|
plt = htab->splt;
|
plt = htab->splt;
|
gotplt = htab->sgotplt;
|
gotplt = htab->sgotplt;
|
relplt = htab->srelplt;
|
relplt = htab->srelplt;
|
|
|
/* If this is the first .plt entry, make room for the special
|
/* If this is the first .plt entry, make room for the special
|
first entry. */
|
first entry. */
|
if (plt->size == 0)
|
if (plt->size == 0)
|
plt->size += plt_entry_size;
|
plt->size += plt_entry_size;
|
}
|
}
|
else
|
else
|
{
|
{
|
plt = htab->iplt;
|
plt = htab->iplt;
|
gotplt = htab->igotplt;
|
gotplt = htab->igotplt;
|
relplt = htab->irelplt;
|
relplt = htab->irelplt;
|
}
|
}
|
|
|
/* Don't update value of STT_GNU_IFUNC symbol to PLT. We need
|
/* Don't update value of STT_GNU_IFUNC symbol to PLT. We need
|
the original value for R_*_IRELATIVE. */
|
the original value for R_*_IRELATIVE. */
|
h->plt.offset = plt->size;
|
h->plt.offset = plt->size;
|
|
|
/* Make room for this entry in the .plt/.iplt section. */
|
/* Make room for this entry in the .plt/.iplt section. */
|
plt->size += plt_entry_size;
|
plt->size += plt_entry_size;
|
|
|
/* We also need to make an entry in the .got.plt/.got.iplt section,
|
/* 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. */
|
which will be placed in the .got section by the linker script. */
|
gotplt->size += got_entry_size;
|
gotplt->size += got_entry_size;
|
|
|
/* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
|
/* We also need to make an entry in the .rel[a].plt/.rel[a].iplt
|
section. */
|
section. */
|
relplt->size += sizeof_reloc;
|
relplt->size += sizeof_reloc;
|
relplt->reloc_count++;
|
relplt->reloc_count++;
|
|
|
/* We need dynamic relocation for STT_GNU_IFUNC symbol only when
|
/* We need dynamic relocation for STT_GNU_IFUNC symbol only when
|
there is a non-GOT reference in a shared object. */
|
there is a non-GOT reference in a shared object. */
|
if (!info->shared
|
if (!info->shared
|
|| !h->non_got_ref)
|
|| !h->non_got_ref)
|
*head = NULL;
|
*head = NULL;
|
|
|
/* Finally, allocate space. */
|
/* Finally, allocate space. */
|
p = *head;
|
p = *head;
|
if (p != NULL)
|
if (p != NULL)
|
{
|
{
|
bfd_size_type count = 0;
|
bfd_size_type count = 0;
|
do
|
do
|
{
|
{
|
count += p->count;
|
count += p->count;
|
p = p->next;
|
p = p->next;
|
}
|
}
|
while (p != NULL);
|
while (p != NULL);
|
htab->irelifunc->size += count * sizeof_reloc;
|
htab->irelifunc->size += count * sizeof_reloc;
|
}
|
}
|
|
|
/* For STT_GNU_IFUNC symbol, .got.plt has the real function address
|
/* 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
|
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
|
with the PLT entry in finish_dynamic_symbol if it is used. For
|
branch, it uses .got.plt. For symbol value,
|
branch, it uses .got.plt. For symbol value,
|
1. Use .got.plt in a shared object if it is forced local or not
|
1. Use .got.plt in a shared object if it is forced local or not
|
dynamic.
|
dynamic.
|
2. Use .got.plt in a non-shared object if pointer equality isn't
|
2. Use .got.plt in a non-shared object if pointer equality isn't
|
needed.
|
needed.
|
3. Use .got.plt in PIE.
|
3. Use .got.plt in PIE.
|
4. Use .got.plt if .got isn't used.
|
4. Use .got.plt if .got isn't used.
|
5. Otherwise use .got so that it can be shared among different
|
5. Otherwise use .got so that it can be shared among different
|
objects at run-time.
|
objects at run-time.
|
We only need to relocate .got entry in shared object. */
|
We only need to relocate .got entry in shared object. */
|
if ((info->shared
|
if (h->got.refcount <= 0
|
|
|| (info->shared
|
&& (h->dynindx == -1
|
&& (h->dynindx == -1
|
|| h->forced_local))
|
|| h->forced_local))
|
|| (!info->shared
|
|| (!info->shared
|
&& !h->pointer_equality_needed)
|
&& !h->pointer_equality_needed)
|
|| (info->executable && info->shared)
|
|| (info->executable && info->shared)
|
|| htab->sgot == NULL)
|
|| htab->sgot == NULL)
|
{
|
{
|
/* Use .got.plt. */
|
/* Use .got.plt. */
|
h->got.offset = (bfd_vma) -1;
|
h->got.offset = (bfd_vma) -1;
|
}
|
}
|
else
|
else
|
{
|
{
|
h->got.offset = htab->sgot->size;
|
h->got.offset = htab->sgot->size;
|
htab->sgot->size += got_entry_size;
|
htab->sgot->size += got_entry_size;
|
if (info->shared)
|
if (info->shared)
|
htab->srelgot->size += sizeof_reloc;
|
htab->srelgot->size += sizeof_reloc;
|
}
|
}
|
|
|
return TRUE;
|
return TRUE;
|
}
|
}
|
|
|
