/* ELF STT_GNU_IFUNC support.
- Copyright (C) 2009-2014 Free Software Foundation, Inc.
+ Copyright (C) 2009-2020 Free Software Foundation, Inc.
This file is part of BFD, the Binary File Descriptor library.
if (bed->plt_readonly)
pltflags |= SEC_READONLY;
- if (info->shared)
+ if (bfd_link_pic (info))
{
- /* We need to create .rel[a].ifunc for shared objects. */
+ /* We need to create .rel[a].ifunc for PIC 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))
+ || !bfd_set_section_alignment (s, bed->s->log_file_align))
return FALSE;
htab->irelifunc = s;
}
for static executables. */
s = bfd_make_section_with_flags (abfd, ".iplt", pltflags);
if (s == NULL
- || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
+ || !bfd_set_section_alignment (s, bed->plt_alignment))
return FALSE;
htab->iplt = s;
? ".rela.iplt" : ".rel.iplt"),
flags | SEC_READONLY);
if (s == NULL
- || ! bfd_set_section_alignment (abfd, s,
- bed->s->log_file_align))
+ || !bfd_set_section_alignment (s, bed->s->log_file_align))
return FALSE;
htab->irelplt = s;
else
s = bfd_make_section_with_flags (abfd, ".igot", flags);
if (s == NULL
- || !bfd_set_section_alignment (abfd, s,
- bed->s->log_file_align))
+ || !bfd_set_section_alignment (s, bed->s->log_file_align))
return FALSE;
htab->igotplt = s;
}
struct elf_dyn_relocs **head,
unsigned int plt_entry_size,
unsigned int plt_header_size,
- unsigned int got_entry_size)
+ unsigned int got_entry_size,
+ bfd_boolean avoid_plt)
{
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
+ /* If AVOID_PLT is TRUE, don't use PLT if possible. */
+ bfd_boolean use_plt = !avoid_plt || h->plt.refcount > 0;
+ bfd_boolean need_dynreloc = !use_plt || bfd_link_pic (info);
+
+ /* When a PIC object references a STT_GNU_IFUNC symbol defined
+ in executable or it isn't referenced via PLT, the address of
+ the resolved function may be used. But in non-PIC executable,
+ the address of its .plt slot may be used. Pointer equality may
+ not work correctly. PIE or non-PLT reference should be used if
+ pointer equality is required here.
+
+ If STT_GNU_IFUNC symbol is defined in position-dependent executable,
+ backend should change it to the normal function and set its address
+ to its PLT entry which should be resolved by R_*_IRELATIVE at
+ run-time. All external references should be resolved to its PLT in
+ executable. */
+ if (!need_dynreloc
+ && !(bfd_link_pde (info) && h->def_regular)
&& (h->dynindx != -1
|| info->export_dynamic)
&& h->pointer_equality_needed)
{
info->callbacks->einfo
+ /* xgettext:c-format */
(_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
- "equality in `%B' can not be used when making an "
+ "equality in `%pB' 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);
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;
- }
+ /* When the symbol is marked with regular reference, if PLT isn't used
+ or we are building a PIC object, we must keep dynamic relocation
+ if there is non-GOT reference and use PLT if there is PC-relative
+ reference. */
+ if (need_dynreloc && h->ref_regular)
+ {
+ bfd_boolean keep = FALSE;
+ for (p = *head; p != NULL; p = p->next)
+ if (p->count)
+ {
+ h->non_got_ref = 1;
+ /* Need dynamic relocations for non-GOT reference. */
+ keep = TRUE;
+ if (p->pc_count)
+ {
+ /* Must use PLT for PC-relative reference. */
+ use_plt = TRUE;
+ need_dynreloc = bfd_link_pic (info);
+ break;
+ }
+ }
+ if (keep)
+ goto keep;
+ }
/* Support garbage collection against STT_GNU_IFUNC symbols. */
if (h->plt.refcount <= 0 && h->got.refcount <= 0)
}
/* Return and discard space for dynamic relocations against it if
- it is never referenced in a non-shared object. */
+ it is never referenced. */
if (!h->ref_regular)
{
if (h->plt.refcount > 0
return TRUE;
}
-keep:
+ keep:
bed = get_elf_backend_data (info->output_bfd);
if (bed->rela_plts_and_copies_p)
sizeof_reloc = bed->s->sizeof_rela;
gotplt = htab->sgotplt;
relplt = htab->srelplt;
- /* If this is the first .plt entry, make room for the special
- first entry. */
- if (plt->size == 0)
+ /* If this is the first .plt entry and PLT is used, make room for
+ the special first entry. */
+ if (plt->size == 0 && use_plt)
plt->size += plt_header_size;
}
else
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;
+ if (use_plt)
+ {
+ /* 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;
+ /* 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 .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++;
+ section for GOTPLT relocation if PLT is used. */
+ if (use_plt)
+ {
+ 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)
+ there is a non-GOT reference in a PIC object or PLT isn't used. */
+ if (!need_dynreloc || !h->non_got_ref)
*head = NULL;
/* Finally, allocate space. */
p = p->next;
}
while (p != NULL);
- htab->irelifunc->size += count * sizeof_reloc;
+
+ htab->ifunc_resolvers = count != 0;
+
+ /* Dynamic relocations are stored in
+ 1. .rel[a].ifunc section in PIC object.
+ 2. .rel[a].got section in dynamic executable.
+ 3. .rel[a].iplt section in static executable. */
+ if (bfd_link_pic (info))
+ htab->irelifunc->size += count * sizeof_reloc;
+ else if (htab->splt != NULL)
+ htab->srelgot->size += count * sizeof_reloc;
+ else
+ {
+ relplt->size += count * sizeof_reloc;
+ relplt->reloc_count += count;
+ }
}
/* 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
+ branch, it uses .got.plt. For symbol value, if PLT is used,
+ 1. Use .got.plt in a PIC object if it is forced local or not
dynamic.
- 2. Use .got.plt in a non-shared object if pointer equality isn't
+ 2. Use .got.plt in a non-PIC 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)
+ If PLT isn't used, always use .got for symbol value.
+ We only need to relocate .got entry in PIC object or in dynamic
+ executable without PLT. */
+ if (use_plt
+ && (h->got.refcount <= 0
+ || (bfd_link_pic (info)
+ && (h->dynindx == -1
+ || h->forced_local))
+ || (!bfd_link_pic (info)
+ && !h->pointer_equality_needed)
+ || bfd_link_pie (info)
+ || 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)
+ if (!use_plt)
{
-#ifdef BFD64
- size += sizeof ("+0x") - 1 + 8 + 8 * (bed->s->elfclass == ELFCLASS64);
-#else
- size += sizeof ("+0x") - 1 + 8;
-#endif
+ /* PLT isn't used. */
+ h->plt.offset = (bfd_vma) -1;
}
- }
-
- 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)
+ if (h->got.refcount <= 0)
+ {
+ /* GOT isn't need when there are only relocations for static
+ pointers. */
+ h->got.offset = (bfd_vma) -1;
+ }
+ else
{
- 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;
+ h->got.offset = htab->sgot->size;
+ htab->sgot->size += got_entry_size;
+ /* Need to relocate the GOT entry in a PIC object or PLT isn't
+ used. Otherwise, the GOT entry will be filled with the PLT
+ entry and dynamic GOT relocation isn't needed. */
+ if (need_dynreloc)
+ {
+ /* For non-static executable, dynamic GOT relocation is in
+ .rel[a].got section, but for static executable, it is
+ in .rel[a].iplt section. */
+ if (htab->splt != NULL)
+ htab->srelgot->size += sizeof_reloc;
+ else
+ {
+ relplt->size += sizeof_reloc;
+ relplt->reloc_count++;
+ }
+ }
}
- memcpy (names, "@plt", sizeof ("@plt"));
- names += sizeof ("@plt");
- ++s, ++n;
}
- free (plt_sym_val);
-
- return n;
+ return TRUE;
}
projects / deliverable / binutils-gdb.git / blobdiff