X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=bfd%2Felf-ifunc.c;h=09cbf4a3761ec7097f52dcf65e89a61e454aef23;hb=c88960d081f0b37ec03c66a13115e2a68e40d1ad;hp=4bfc31b55cc108e53b4f5d399e875e9e66d329f9;hpb=6de2ae4a2a0020a827f05f30dedf8dcec7e77ee0;p=deliverable%2Fbinutils-gdb.git

diff --git a/bfd/elf-ifunc.c b/bfd/elf-ifunc.c
index 4bfc31b55c..09cbf4a376 100644
--- a/bfd/elf-ifunc.c
+++ b/bfd/elf-ifunc.c
@@ -1,6 +1,5 @@
 /* ELF STT_GNU_IFUNC support.
-   Copyright 2009
-   Free Software Foundation, Inc.
+   Copyright (C) 2009-2016 Free Software Foundation, Inc.
 
    This file is part of BFD, the Binary File Descriptor library.
 
@@ -54,9 +53,9 @@ _bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
   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");
 
@@ -103,3 +102,380 @@ _bfd_elf_create_ifunc_sections (bfd *abfd, struct bfd_link_info *info)
 
   return TRUE;
 }
+
+/* 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,
+				    bfd_boolean *readonly_dynrelocs_against_ifunc_p,
+				    unsigned int plt_entry_size,
+				    unsigned int plt_header_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;
+  bfd_boolean readonly_dynrelocs_against_ifunc;
+  /* 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 (!need_dynreloc
+      && (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);
+
+  /* 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)
+    {
+      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.  */
+  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:
+  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 and PLT is used, make room for
+	 the special first entry.  */
+      if (plt->size == 0 && use_plt)
+	plt->size += plt_header_size;
+    }
+  else
+    {
+      plt = htab->iplt;
+      gotplt = htab->igotplt;
+      relplt = htab->irelplt;
+    }
+
+  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;
+
+      /* 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 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 PIC object or PLT isn't used.  */
+  if (!need_dynreloc || !h->non_got_ref)
+    *head = NULL;
+
+  readonly_dynrelocs_against_ifunc = FALSE;
+
+  /* Finally, allocate space.  */
+  p = *head;
+  if (p != NULL)
+    {
+      bfd_size_type count = 0;
+      do
+	{
+	  if (!readonly_dynrelocs_against_ifunc)
+	    {
+	      asection *s = p->sec->output_section;
+	      if (s != NULL && (s->flags & SEC_READONLY) != 0)
+		readonly_dynrelocs_against_ifunc = TRUE;
+	    }
+	  count += p->count;
+	  p = p->next;
+	}
+      while (p != NULL);
+
+      /* 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;
+	}
+    }
+
+  if (readonly_dynrelocs_against_ifunc_p)
+    *readonly_dynrelocs_against_ifunc_p = readonly_dynrelocs_against_ifunc;
+
+  /* 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, 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-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.
+     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
+    {
+      if (!use_plt)
+	{
+	  /* PLT isn't used.  */
+	  h->plt.offset = (bfd_vma) -1;
+	}
+      if (h->got.refcount <= 0)
+	{
+	  /* GOT isn't need when there are only relocations for static
+	     pointers.  */
+	  h->got.offset = (bfd_vma) -1;
+	}
+      else
+	{
+	  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++;
+		}
+	    }
+	}
+    }
+
+  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)
+	{
+#ifdef BFD64
+	  size += sizeof ("+0x") - 1 + 8 + 8 * (bed->s->elfclass == ELFCLASS64);
+#else
+	  size += sizeof ("+0x") - 1 + 8;
+#endif
+	}
+    }
+
+  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)
+	{
+	  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;
+	}
+      memcpy (names, "@plt", sizeof ("@plt"));
+      names += sizeof ("@plt");
+      ++s, ++n;
+    }
+
+  free (plt_sym_val);
+
+  return n;
+}