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/* IBM S/390-specific support for ELF 32 and 64 bit functions
Copyright (C) 2000-2015 Free Software Foundation, Inc.
Contributed by Andreas Krebbel.
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. */
/* Return TRUE if H is an IFUNC symbol. Simply checking for the
symbol type might not be enough since it might get changed to
STT_FUNC for pointer equality reasons. */
static inline bfd_boolean
s390_is_ifunc_symbol_p (struct elf_link_hash_entry *h)
{
struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
return h->type == STT_GNU_IFUNC || eh->ifunc_resolver_address != 0;
}
/* Create sections needed by STT_GNU_IFUNC symbol. */
static bfd_boolean
s390_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
{
flagword flags;
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->iplt != NULL)
return TRUE;
flags = bed->dynamic_sec_flags;
if (info->shared)
{
s = bfd_make_section_with_flags (abfd, ".rela.ifunc",
flags | SEC_READONLY);
if (s == NULL
|| ! bfd_set_section_alignment (abfd, s,
bed->s->log_file_align))
return FALSE;
htab->irelifunc = s;
}
/* Create .iplt, .rel[a].iplt, and .igot.plt. */
s = bfd_make_section_with_flags (abfd, ".iplt",
flags | SEC_CODE | SEC_READONLY);
if (s == NULL
|| ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
return FALSE;
htab->iplt = s;
s = bfd_make_section_with_flags (abfd, ".rela.iplt", flags | SEC_READONLY);
if (s == NULL
|| ! bfd_set_section_alignment (abfd, s,
bed->s->log_file_align))
return FALSE;
htab->irelplt = s;
s = bfd_make_section_with_flags (abfd, ".igot.plt", flags);
if (s == NULL
|| !bfd_set_section_alignment (abfd, s,
bed->s->log_file_align))
return FALSE;
htab->igotplt = s;
return TRUE;
}
/* Allocate space in .plt, .got and associated reloc sections for
dynamic relocs against a STT_GNU_IFUNC symbol definition. */
static bfd_boolean
s390_elf_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
struct elf_link_hash_entry *h,
struct elf_dyn_relocs **head)
{
struct elf_dyn_relocs *p;
struct elf_link_hash_table *htab;
struct elf_s390_link_hash_entry *eh = (struct elf_s390_link_hash_entry*)h;
htab = elf_hash_table (info);
eh->ifunc_resolver_address = h->root.u.def.value;
eh->ifunc_resolver_section = h->root.u.def.section;
/* Support garbage collection against STT_GNU_IFUNC symbols. */
if (h->plt.refcount <= 0 && h->got.refcount <= 0)
{
/* When building shared library, we need to handle the case
where it is marked with regular reference, but not non-GOT
reference. It may happen if we didn't see STT_GNU_IFUNC
symbol at the time when checking relocations. */
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;
}
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:
/* Without checking h->plt.refcount here we allocate a PLT slot.
When setting plt.refcount in check_relocs it might not have been
known that this will be an IFUNC symol. */
h->plt.offset = htab->iplt->size;
h->needs_plt = 1;
htab->iplt->size += PLT_ENTRY_SIZE;
htab->igotplt->size += GOT_ENTRY_SIZE;
htab->irelplt->size += RELA_ENTRY_SIZE;
htab->irelplt->reloc_count++;
/* In order to make pointer equality work with IFUNC symbols defined
in a non-PIE executable and referenced in a shared lib, we turn
the symbol into a STT_FUNC symbol and make the symbol value to
point to the IPLT slot. That way the referencing shared lib will
always get the PLT slot address when resolving the respective
R_390_GLOB_DAT/R_390_64 relocs on that symbol. */
if (info->executable && !info->shared && h->def_regular && h->ref_dynamic)
{
h->root.u.def.section = htab->iplt;
h->root.u.def.value = h->plt.offset;
h->size = PLT_ENTRY_SIZE;
h->type = STT_FUNC;
}
/* 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 * RELA_ENTRY_SIZE;
}
/* Decide whether the got.iplt slot can be used. This has to be
avoided if the values in the GOT slots could differ for pointer
equality reasons. */
if (h->got.refcount <= 0
|| (info->shared
&& (h->dynindx == -1 || h->forced_local))
|| (info->executable && info->shared)
|| htab->sgot == NULL)
{
/* Use .got.iplt. */
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 += RELA_ENTRY_SIZE;
}
return TRUE;
}
static bfd_boolean
elf_s390_allocate_local_syminfo (bfd *abfd, Elf_Internal_Shdr *symtab_hdr)
{
bfd_size_type size;
size = symtab_hdr->sh_info;
size *= (sizeof (bfd_signed_vma) /* local got */
+ sizeof (struct plt_entry) /* local plt */
+ sizeof(char)); /* local tls type */
elf_local_got_refcounts (abfd) = ((bfd_signed_vma *)
bfd_zalloc (abfd, size));
if (elf_local_got_refcounts (abfd) == NULL)
return FALSE;
elf_s390_local_plt (abfd)
= (struct plt_entry*)(elf_local_got_refcounts (abfd)
+ symtab_hdr->sh_info);
elf_s390_local_got_tls_type (abfd)
= (char *) (elf_s390_local_plt (abfd) + symtab_hdr->sh_info);
return TRUE;
}
/* Pick ELFOSABI_GNU if IFUNC symbols are used. */
static bfd_boolean
elf_s390_add_symbol_hook (bfd *abfd,
struct bfd_link_info *info,
Elf_Internal_Sym *sym,
const char **namep ATTRIBUTE_UNUSED,
flagword *flagsp ATTRIBUTE_UNUSED,
asection **secp ATTRIBUTE_UNUSED,
bfd_vma *valp ATTRIBUTE_UNUSED)
{
if ((ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC
|| ELF_ST_BIND (sym->st_info) == STB_GNU_UNIQUE)
&& (abfd->flags & DYNAMIC) == 0
&& bfd_get_flavour (info->output_bfd) == bfd_target_elf_flavour)
elf_tdata (info->output_bfd)->has_gnu_symbols = TRUE;
return TRUE;
}
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