Use %A and %B in more error messages

[deliverable/binutils-gdb.git] / bfd / elf-eh-frame.c

/* .eh_frame section optimization.
   Copyright (C) 2001-2017 Free Software Foundation, Inc.
   Written by Jakub Jelinek <jakub@redhat.com>.

   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.  */

#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"
#include "elf-bfd.h"
#include "dwarf2.h"

#define EH_FRAME_HDR_SIZE 8

struct cie
{
  unsigned int length;
  unsigned int hash;
  unsigned char version;
  unsigned char local_personality;
  char augmentation[20];
  bfd_vma code_align;
  bfd_signed_vma data_align;
  bfd_vma ra_column;
  bfd_vma augmentation_size;
  union {
    struct elf_link_hash_entry *h;
    struct {
      unsigned int bfd_id;
      unsigned int index;
    } sym;
    unsigned int reloc_index;
  } personality;
  struct eh_cie_fde *cie_inf;
  unsigned char per_encoding;
  unsigned char lsda_encoding;
  unsigned char fde_encoding;
  unsigned char initial_insn_length;
  unsigned char can_make_lsda_relative;
  unsigned char initial_instructions[50];
};



/* If *ITER hasn't reached END yet, read the next byte into *RESULT and
   move onto the next byte.  Return true on success.  */

static inline bfd_boolean
read_byte (bfd_byte **iter, bfd_byte *end, unsigned char *result)
{
  if (*iter >= end)
    return FALSE;
  *result = *((*iter)++);
  return TRUE;
}

/* Move *ITER over LENGTH bytes, or up to END, whichever is closer.
   Return true it was possible to move LENGTH bytes.  */

static inline bfd_boolean
skip_bytes (bfd_byte **iter, bfd_byte *end, bfd_size_type length)
{
  if ((bfd_size_type) (end - *iter) < length)
    {
      *iter = end;
      return FALSE;
    }
  *iter += length;
  return TRUE;
}

/* Move *ITER over an leb128, stopping at END.  Return true if the end
   of the leb128 was found.  */

static bfd_boolean
skip_leb128 (bfd_byte **iter, bfd_byte *end)
{
  unsigned char byte;
  do
    if (!read_byte (iter, end, &byte))
      return FALSE;
  while (byte & 0x80);
  return TRUE;
}

/* Like skip_leb128, but treat the leb128 as an unsigned value and
   store it in *VALUE.  */

static bfd_boolean
read_uleb128 (bfd_byte **iter, bfd_byte *end, bfd_vma *value)
{
  bfd_byte *start, *p;

  start = *iter;
  if (!skip_leb128 (iter, end))
    return FALSE;

  p = *iter;
  *value = *--p;
  while (p > start)
    *value = (*value << 7) | (*--p & 0x7f);

  return TRUE;
}

/* Like read_uleb128, but for signed values.  */

static bfd_boolean
read_sleb128 (bfd_byte **iter, bfd_byte *end, bfd_signed_vma *value)
{
  bfd_byte *start, *p;

  start = *iter;
  if (!skip_leb128 (iter, end))
    return FALSE;

  p = *iter;
  *value = ((*--p & 0x7f) ^ 0x40) - 0x40;
  while (p > start)
    *value = (*value << 7) | (*--p & 0x7f);

  return TRUE;
}

/* Return 0 if either encoding is variable width, or not yet known to bfd.  */

static
int get_DW_EH_PE_width (int encoding, int ptr_size)
{
  /* DW_EH_PE_ values of 0x60 and 0x70 weren't defined at the time .eh_frame
     was added to bfd.  */
  if ((encoding & 0x60) == 0x60)
    return 0;

  switch (encoding & 7)
    {
    case DW_EH_PE_udata2: return 2;
    case DW_EH_PE_udata4: return 4;
    case DW_EH_PE_udata8: return 8;
    case DW_EH_PE_absptr: return ptr_size;
    default:
      break;
    }

  return 0;
}

#define get_DW_EH_PE_signed(encoding) (((encoding) & DW_EH_PE_signed) != 0)

/* Read a width sized value from memory.  */

static bfd_vma
read_value (bfd *abfd, bfd_byte *buf, int width, int is_signed)
{
  bfd_vma value;

  switch (width)
    {
    case 2:
      if (is_signed)
        value = bfd_get_signed_16 (abfd, buf);
      else
        value = bfd_get_16 (abfd, buf);
      break;
    case 4:
      if (is_signed)
        value = bfd_get_signed_32 (abfd, buf);
      else
        value = bfd_get_32 (abfd, buf);
      break;
    case 8:
      if (is_signed)
        value = bfd_get_signed_64 (abfd, buf);
      else
        value = bfd_get_64 (abfd, buf);
      break;
    default:
      BFD_FAIL ();
      return 0;
    }

  return value;
}

/* Store a width sized value to memory.  */

static void
write_value (bfd *abfd, bfd_byte *buf, bfd_vma value, int width)
{
  switch (width)
    {
    case 2: bfd_put_16 (abfd, value, buf); break;
    case 4: bfd_put_32 (abfd, value, buf); break;
    case 8: bfd_put_64 (abfd, value, buf); break;
    default: BFD_FAIL ();
    }
}

/* Return one if C1 and C2 CIEs can be merged.  */

static int
cie_eq (const void *e1, const void *e2)
{
  const struct cie *c1 = (const struct cie *) e1;
  const struct cie *c2 = (const struct cie *) e2;

  if (c1->hash == c2->hash
      && c1->length == c2->length
      && c1->version == c2->version
      && c1->local_personality == c2->local_personality
      && strcmp (c1->augmentation, c2->augmentation) == 0
      && strcmp (c1->augmentation, "eh") != 0
      && c1->code_align == c2->code_align
      && c1->data_align == c2->data_align
      && c1->ra_column == c2->ra_column
      && c1->augmentation_size == c2->augmentation_size
      && memcmp (&c1->personality, &c2->personality,
                 sizeof (c1->personality)) == 0
      && (c1->cie_inf->u.cie.u.sec->output_section
          == c2->cie_inf->u.cie.u.sec->output_section)
      && c1->per_encoding == c2->per_encoding
      && c1->lsda_encoding == c2->lsda_encoding
      && c1->fde_encoding == c2->fde_encoding
      && c1->initial_insn_length == c2->initial_insn_length
      && c1->initial_insn_length <= sizeof (c1->initial_instructions)
      && memcmp (c1->initial_instructions,
                 c2->initial_instructions,
                 c1->initial_insn_length) == 0)
    return 1;

  return 0;
}

static hashval_t
cie_hash (const void *e)
{
  const struct cie *c = (const struct cie *) e;
  return c->hash;
}

static hashval_t
cie_compute_hash (struct cie *c)
{
  hashval_t h = 0;
  size_t len;
  h = iterative_hash_object (c->length, h);
  h = iterative_hash_object (c->version, h);
  h = iterative_hash (c->augmentation, strlen (c->augmentation) + 1, h);
  h = iterative_hash_object (c->code_align, h);
  h = iterative_hash_object (c->data_align, h);
  h = iterative_hash_object (c->ra_column, h);
  h = iterative_hash_object (c->augmentation_size, h);
  h = iterative_hash_object (c->personality, h);
  h = iterative_hash_object (c->cie_inf->u.cie.u.sec->output_section, h);
  h = iterative_hash_object (c->per_encoding, h);
  h = iterative_hash_object (c->lsda_encoding, h);
  h = iterative_hash_object (c->fde_encoding, h);
  h = iterative_hash_object (c->initial_insn_length, h);
  len = c->initial_insn_length;
  if (len > sizeof (c->initial_instructions))
    len = sizeof (c->initial_instructions);
  h = iterative_hash (c->initial_instructions, len, h);
  c->hash = h;
  return h;
}

/* Return the number of extra bytes that we'll be inserting into
   ENTRY's augmentation string.  */

static INLINE unsigned int
extra_augmentation_string_bytes (struct eh_cie_fde *entry)
{
  unsigned int size = 0;
  if (entry->cie)
    {
      if (entry->add_augmentation_size)
        size++;
      if (entry->u.cie.add_fde_encoding)
        size++;
    }
  return size;
}

/* Likewise ENTRY's augmentation data.  */

static INLINE unsigned int
extra_augmentation_data_bytes (struct eh_cie_fde *entry)
{
  unsigned int size = 0;
  if (entry->add_augmentation_size)
    size++;
  if (entry->cie && entry->u.cie.add_fde_encoding)
    size++;
  return size;
}

/* Return the size that ENTRY will have in the output.  */

static unsigned int
size_of_output_cie_fde (struct eh_cie_fde *entry)
{
  if (entry->removed)
    return 0;
  if (entry->size == 4)
    return 4;
  return (entry->size
          + extra_augmentation_string_bytes (entry)
          + extra_augmentation_data_bytes (entry));
}

/* Return the offset of the FDE or CIE after ENT.  */

static unsigned int
next_cie_fde_offset (struct eh_cie_fde *ent,
                     struct eh_cie_fde *last,
                     asection *sec)
{
  while (++ent < last)
    {
      if (!ent->removed)
        return ent->new_offset;
    }
  return sec->size;
}

/* Assume that the bytes between *ITER and END are CFA instructions.
   Try to move *ITER past the first instruction and return true on
   success.  ENCODED_PTR_WIDTH gives the width of pointer entries.  */

static bfd_boolean
skip_cfa_op (bfd_byte **iter, bfd_byte *end, unsigned int encoded_ptr_width)
{
  bfd_byte op;
  bfd_vma length;

  if (!read_byte (iter, end, &op))
    return FALSE;

  switch (op & 0xc0 ? op & 0xc0 : op)
    {
    case DW_CFA_nop:
    case DW_CFA_advance_loc:
    case DW_CFA_restore:
    case DW_CFA_remember_state:
    case DW_CFA_restore_state:
    case DW_CFA_GNU_window_save:
      /* No arguments.  */
      return TRUE;

    case DW_CFA_offset:
    case DW_CFA_restore_extended:
    case DW_CFA_undefined:
    case DW_CFA_same_value:
    case DW_CFA_def_cfa_register:
    case DW_CFA_def_cfa_offset:
    case DW_CFA_def_cfa_offset_sf:
    case DW_CFA_GNU_args_size:
      /* One leb128 argument.  */
      return skip_leb128 (iter, end);

    case DW_CFA_val_offset:
    case DW_CFA_val_offset_sf:
    case DW_CFA_offset_extended:
    case DW_CFA_register:
    case DW_CFA_def_cfa:
    case DW_CFA_offset_extended_sf:
    case DW_CFA_GNU_negative_offset_extended:
    case DW_CFA_def_cfa_sf:
      /* Two leb128 arguments.  */
      return (skip_leb128 (iter, end)
              && skip_leb128 (iter, end));

    case DW_CFA_def_cfa_expression:
      /* A variable-length argument.  */
      return (read_uleb128 (iter, end, &length)
              && skip_bytes (iter, end, length));

    case DW_CFA_expression:
    case DW_CFA_val_expression:
      /* A leb128 followed by a variable-length argument.  */
      return (skip_leb128 (iter, end)
              && read_uleb128 (iter, end, &length)
              && skip_bytes (iter, end, length));

    case DW_CFA_set_loc:
      return skip_bytes (iter, end, encoded_ptr_width);

    case DW_CFA_advance_loc1:
      return skip_bytes (iter, end, 1);

    case DW_CFA_advance_loc2:
      return skip_bytes (iter, end, 2);

    case DW_CFA_advance_loc4:
      return skip_bytes (iter, end, 4);

    case DW_CFA_MIPS_advance_loc8:
      return skip_bytes (iter, end, 8);

    default:
      return FALSE;
    }
}

/* Try to interpret the bytes between BUF and END as CFA instructions.
   If every byte makes sense, return a pointer to the first DW_CFA_nop
   padding byte, or END if there is no padding.  Return null otherwise.
   ENCODED_PTR_WIDTH is as for skip_cfa_op.  */

static bfd_byte *
skip_non_nops (bfd_byte *buf, bfd_byte *end, unsigned int encoded_ptr_width,
               unsigned int *set_loc_count)
{
  bfd_byte *last;

  last = buf;
  while (buf < end)
    if (*buf == DW_CFA_nop)
      buf++;
    else
      {
        if (*buf == DW_CFA_set_loc)
          ++*set_loc_count;
        if (!skip_cfa_op (&buf, end, encoded_ptr_width))
          return 0;
        last = buf;
      }
  return last;
}

/* Convert absolute encoding ENCODING into PC-relative form.
   SIZE is the size of a pointer.  */

static unsigned char
make_pc_relative (unsigned char encoding, unsigned int ptr_size)
{
  if ((encoding & 0x7f) == DW_EH_PE_absptr)
    switch (ptr_size)
      {
      case 2:
        encoding |= DW_EH_PE_sdata2;
        break;
      case 4:
        encoding |= DW_EH_PE_sdata4;
        break;
      case 8:
        encoding |= DW_EH_PE_sdata8;
        break;
      }
  return encoding | DW_EH_PE_pcrel;
}

/*  Examine each .eh_frame_entry section and discard those
    those that are marked SEC_EXCLUDE.  */

static void
bfd_elf_discard_eh_frame_entry (struct eh_frame_hdr_info *hdr_info)
{
  unsigned int i;
  for (i = 0; i < hdr_info->array_count; i++)
    {
      if (hdr_info->u.compact.entries[i]->flags & SEC_EXCLUDE)
        {
          unsigned int j;
          for (j = i + 1; j < hdr_info->array_count; j++)
            hdr_info->u.compact.entries[j-1] = hdr_info->u.compact.entries[j];

          hdr_info->array_count--;
          hdr_info->u.compact.entries[hdr_info->array_count] = NULL;
          i--;
        }
    }
}

/* Add a .eh_frame_entry section.  */

static void
bfd_elf_record_eh_frame_entry (struct eh_frame_hdr_info *hdr_info,
                                 asection *sec)
{
  if (hdr_info->array_count == hdr_info->u.compact.allocated_entries)
    {
      if (hdr_info->u.compact.allocated_entries == 0)
        {
          hdr_info->frame_hdr_is_compact = TRUE;
          hdr_info->u.compact.allocated_entries = 2;
          hdr_info->u.compact.entries =
            bfd_malloc (hdr_info->u.compact.allocated_entries
                        * sizeof (hdr_info->u.compact.entries[0]));
        }
      else
        {
          hdr_info->u.compact.allocated_entries *= 2;
          hdr_info->u.compact.entries =
            bfd_realloc (hdr_info->u.compact.entries,
                         hdr_info->u.compact.allocated_entries
                           * sizeof (hdr_info->u.compact.entries[0]));
        }

      BFD_ASSERT (hdr_info->u.compact.entries);
    }

  hdr_info->u.compact.entries[hdr_info->array_count++] = sec;
}

/* Parse a .eh_frame_entry section.  Figure out which text section it
   references.  */

bfd_boolean
_bfd_elf_parse_eh_frame_entry (struct bfd_link_info *info,
                               asection *sec, struct elf_reloc_cookie *cookie)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  unsigned long r_symndx;
  asection *text_sec;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;

  if (sec->size == 0
      || sec->sec_info_type != SEC_INFO_TYPE_NONE)
    {
      return TRUE;
    }

  if (sec->output_section && bfd_is_abs_section (sec->output_section))
    {
      /* At least one of the sections is being discarded from the
         link, so we should just ignore them.  */
      return TRUE;
    }

  if (cookie->rel == cookie->relend)
    return FALSE;

  /* The first relocation is the function start.  */
  r_symndx = cookie->rel->r_info >> cookie->r_sym_shift;
  if (r_symndx == STN_UNDEF)
    return FALSE;

  text_sec = _bfd_elf_section_for_symbol (cookie, r_symndx, FALSE);

  if (text_sec == NULL)
    return FALSE;

  elf_section_eh_frame_entry (text_sec) = sec;
  if (text_sec->output_section
      && bfd_is_abs_section (text_sec->output_section))
    sec->flags |= SEC_EXCLUDE;

  sec->sec_info_type = SEC_INFO_TYPE_EH_FRAME_ENTRY;
  elf_section_data (sec)->sec_info = text_sec;
  bfd_elf_record_eh_frame_entry (hdr_info, sec);
  return TRUE;
}

/* Try to parse .eh_frame section SEC, which belongs to ABFD.  Store the
   information in the section's sec_info field on success.  COOKIE
   describes the relocations in SEC.  */

void
_bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
                         asection *sec, struct elf_reloc_cookie *cookie)
{
#define REQUIRE(COND)                                   \
  do                                                    \
    if (!(COND))                                        \
      goto free_no_table;                               \
  while (0)

  bfd_byte *ehbuf = NULL, *buf, *end;
  bfd_byte *last_fde;
  struct eh_cie_fde *this_inf;
  unsigned int hdr_length, hdr_id;
  unsigned int cie_count;
  struct cie *cie, *local_cies = NULL;
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  struct eh_frame_sec_info *sec_info = NULL;
  unsigned int ptr_size;
  unsigned int num_cies;
  unsigned int num_entries;
  elf_gc_mark_hook_fn gc_mark_hook;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;

  if (sec->size == 0
      || sec->sec_info_type != SEC_INFO_TYPE_NONE)
    {
      /* This file does not contain .eh_frame information.  */
      return;
    }

  if (bfd_is_abs_section (sec->output_section))
    {
      /* At least one of the sections is being discarded from the
         link, so we should just ignore them.  */
      return;
    }

  /* Read the frame unwind information from abfd.  */

  REQUIRE (bfd_malloc_and_get_section (abfd, sec, &ehbuf));

  if (sec->size >= 4
      && bfd_get_32 (abfd, ehbuf) == 0
      && cookie->rel == cookie->relend)
    {
      /* Empty .eh_frame section.  */
      free (ehbuf);
      return;
    }

  /* If .eh_frame section size doesn't fit into int, we cannot handle
     it (it would need to use 64-bit .eh_frame format anyway).  */
  REQUIRE (sec->size == (unsigned int) sec->size);

  ptr_size = (get_elf_backend_data (abfd)
              ->elf_backend_eh_frame_address_size (abfd, sec));
  REQUIRE (ptr_size != 0);

  /* Go through the section contents and work out how many FDEs and
     CIEs there are.  */
  buf = ehbuf;
  end = ehbuf + sec->size;
  num_cies = 0;
  num_entries = 0;
  while (buf != end)
    {
      num_entries++;

      /* Read the length of the entry.  */
      REQUIRE (skip_bytes (&buf, end, 4));
      hdr_length = bfd_get_32 (abfd, buf - 4);

      /* 64-bit .eh_frame is not supported.  */
      REQUIRE (hdr_length != 0xffffffff);
      if (hdr_length == 0)
        break;

      REQUIRE (skip_bytes (&buf, end, 4));
      hdr_id = bfd_get_32 (abfd, buf - 4);
      if (hdr_id == 0)
        num_cies++;

      REQUIRE (skip_bytes (&buf, end, hdr_length - 4));
    }

  sec_info = (struct eh_frame_sec_info *)
      bfd_zmalloc (sizeof (struct eh_frame_sec_info)
                   + (num_entries - 1) * sizeof (struct eh_cie_fde));
  REQUIRE (sec_info);

  /* We need to have a "struct cie" for each CIE in this section.  */
  local_cies = (struct cie *) bfd_zmalloc (num_cies * sizeof (*local_cies));
  REQUIRE (local_cies);

  /* FIXME: octets_per_byte.  */
#define ENSURE_NO_RELOCS(buf)                           \
  while (cookie->rel < cookie->relend                   \
         && (cookie->rel->r_offset                      \
             < (bfd_size_type) ((buf) - ehbuf)))        \
    {                                                   \
      REQUIRE (cookie->rel->r_info == 0);               \
      cookie->rel++;                                    \
    }

  /* FIXME: octets_per_byte.  */
#define SKIP_RELOCS(buf)                                \
  while (cookie->rel < cookie->relend                   \
         && (cookie->rel->r_offset                      \
             < (bfd_size_type) ((buf) - ehbuf)))        \
    cookie->rel++

  /* FIXME: octets_per_byte.  */
#define GET_RELOC(buf)                                  \
  ((cookie->rel < cookie->relend                        \
    && (cookie->rel->r_offset                           \
        == (bfd_size_type) ((buf) - ehbuf)))            \
   ? cookie->rel : NULL)

  buf = ehbuf;
  cie_count = 0;
  gc_mark_hook = get_elf_backend_data (abfd)->gc_mark_hook;
  while ((bfd_size_type) (buf - ehbuf) != sec->size)
    {
      char *aug;
      bfd_byte *start, *insns, *insns_end;
      bfd_size_type length;
      unsigned int set_loc_count;

      this_inf = sec_info->entry + sec_info->count;
      last_fde = buf;

      /* Read the length of the entry.  */
      REQUIRE (skip_bytes (&buf, ehbuf + sec->size, 4));
      hdr_length = bfd_get_32 (abfd, buf - 4);

      /* The CIE/FDE must be fully contained in this input section.  */
      REQUIRE ((bfd_size_type) (buf - ehbuf) + hdr_length <= sec->size);
      end = buf + hdr_length;

      this_inf->offset = last_fde - ehbuf;
      this_inf->size = 4 + hdr_length;
      this_inf->reloc_index = cookie->rel - cookie->rels;

      if (hdr_length == 0)
        {
          /* A zero-length CIE should only be found at the end of
             the section.  */
          REQUIRE ((bfd_size_type) (buf - ehbuf) == sec->size);
          ENSURE_NO_RELOCS (buf);
          sec_info->count++;
          break;
        }

      REQUIRE (skip_bytes (&buf, end, 4));
      hdr_id = bfd_get_32 (abfd, buf - 4);

      if (hdr_id == 0)
        {
          unsigned int initial_insn_length;

          /* CIE  */
          this_inf->cie = 1;

          /* Point CIE to one of the section-local cie structures.  */
          cie = local_cies + cie_count++;

          cie->cie_inf = this_inf;
          cie->length = hdr_length;
          start = buf;
          REQUIRE (read_byte (&buf, end, &cie->version));

          /* Cannot handle unknown versions.  */
          REQUIRE (cie->version == 1
                   || cie->version == 3
                   || cie->version == 4);
          REQUIRE (strlen ((char *) buf) < sizeof (cie->augmentation));

          strcpy (cie->augmentation, (char *) buf);
          buf = (bfd_byte *) strchr ((char *) buf, '\0') + 1;
          ENSURE_NO_RELOCS (buf);
          if (buf[0] == 'e' && buf[1] == 'h')
            {
              /* GCC < 3.0 .eh_frame CIE */
              /* We cannot merge "eh" CIEs because __EXCEPTION_TABLE__
                 is private to each CIE, so we don't need it for anything.
                 Just skip it.  */
              REQUIRE (skip_bytes (&buf, end, ptr_size));
              SKIP_RELOCS (buf);
            }
          if (cie->version >= 4)
            {
              REQUIRE (buf + 1 < end);
              REQUIRE (buf[0] == ptr_size);
              REQUIRE (buf[1] == 0);
              buf += 2;
            }
          REQUIRE (read_uleb128 (&buf, end, &cie->code_align));
          REQUIRE (read_sleb128 (&buf, end, &cie->data_align));
          if (cie->version == 1)
            {
              REQUIRE (buf < end);
              cie->ra_column = *buf++;
            }
          else
            REQUIRE (read_uleb128 (&buf, end, &cie->ra_column));
          ENSURE_NO_RELOCS (buf);
          cie->lsda_encoding = DW_EH_PE_omit;
          cie->fde_encoding = DW_EH_PE_omit;
          cie->per_encoding = DW_EH_PE_omit;
          aug = cie->augmentation;
          if (aug[0] != 'e' || aug[1] != 'h')
            {
              if (*aug == 'z')
                {
                  aug++;
                  REQUIRE (read_uleb128 (&buf, end, &cie->augmentation_size));
                  ENSURE_NO_RELOCS (buf);
                }

              while (*aug != '\0')
                switch (*aug++)
                  {
                  case 'L':
                    REQUIRE (read_byte (&buf, end, &cie->lsda_encoding));
                    ENSURE_NO_RELOCS (buf);
                    REQUIRE (get_DW_EH_PE_width (cie->lsda_encoding, ptr_size));
                    break;
                  case 'R':
                    REQUIRE (read_byte (&buf, end, &cie->fde_encoding));
                    ENSURE_NO_RELOCS (buf);
                    REQUIRE (get_DW_EH_PE_width (cie->fde_encoding, ptr_size));
                    break;
                  case 'S':
                    break;
                  case 'P':
                    {
                      int per_width;

                      REQUIRE (read_byte (&buf, end, &cie->per_encoding));
                      per_width = get_DW_EH_PE_width (cie->per_encoding,
                                                      ptr_size);
                      REQUIRE (per_width);
                      if ((cie->per_encoding & 0x70) == DW_EH_PE_aligned)
                        {
                          length = -(buf - ehbuf) & (per_width - 1);
                          REQUIRE (skip_bytes (&buf, end, length));
                          if (per_width == 8)
                            this_inf->u.cie.per_encoding_aligned8 = 1;
                        }
                      this_inf->u.cie.personality_offset = buf - start;
                      ENSURE_NO_RELOCS (buf);
                      /* Ensure we have a reloc here.  */
                      REQUIRE (GET_RELOC (buf));
                      cie->personality.reloc_index
                        = cookie->rel - cookie->rels;
                      /* Cope with MIPS-style composite relocations.  */
                      do
                        cookie->rel++;
                      while (GET_RELOC (buf) != NULL);
                      REQUIRE (skip_bytes (&buf, end, per_width));
                    }
                    break;
                  default:
                    /* Unrecognized augmentation. Better bail out.  */
                    goto free_no_table;
                  }
            }

          /* For shared libraries, try to get rid of as many RELATIVE relocs
             as possible.  */
          if (bfd_link_pic (info)
              && (get_elf_backend_data (abfd)
                  ->elf_backend_can_make_relative_eh_frame
                  (abfd, info, sec)))
            {
              if ((cie->fde_encoding & 0x70) == DW_EH_PE_absptr)
                this_inf->make_relative = 1;
              /* If the CIE doesn't already have an 'R' entry, it's fairly
                 easy to add one, provided that there's no aligned data
                 after the augmentation string.  */
              else if (cie->fde_encoding == DW_EH_PE_omit
                       && (cie->per_encoding & 0x70) != DW_EH_PE_aligned)
                {
                  if (*cie->augmentation == 0)
                    this_inf->add_augmentation_size = 1;
                  this_inf->u.cie.add_fde_encoding = 1;
                  this_inf->make_relative = 1;
                }

              if ((cie->lsda_encoding & 0x70) == DW_EH_PE_absptr)
                cie->can_make_lsda_relative = 1;
            }

          /* If FDE encoding was not specified, it defaults to
             DW_EH_absptr.  */
          if (cie->fde_encoding == DW_EH_PE_omit)
            cie->fde_encoding = DW_EH_PE_absptr;

          initial_insn_length = end - buf;
          cie->initial_insn_length = initial_insn_length;
          memcpy (cie->initial_instructions, buf,
                  initial_insn_length <= sizeof (cie->initial_instructions)
                  ? initial_insn_length : sizeof (cie->initial_instructions));
          insns = buf;
          buf += initial_insn_length;
          ENSURE_NO_RELOCS (buf);

          if (!bfd_link_relocatable (info))
            {
              /* Keep info for merging cies.  */
              this_inf->u.cie.u.full_cie = cie;
              this_inf->u.cie.per_encoding_relative
                = (cie->per_encoding & 0x70) == DW_EH_PE_pcrel;
            }
        }
      else
        {
          /* Find the corresponding CIE.  */
          unsigned int cie_offset = this_inf->offset + 4 - hdr_id;
          for (cie = local_cies; cie < local_cies + cie_count; cie++)
            if (cie_offset == cie->cie_inf->offset)
              break;

          /* Ensure this FDE references one of the CIEs in this input
             section.  */
          REQUIRE (cie != local_cies + cie_count);
          this_inf->u.fde.cie_inf = cie->cie_inf;
          this_inf->make_relative = cie->cie_inf->make_relative;
          this_inf->add_augmentation_size
            = cie->cie_inf->add_augmentation_size;

          ENSURE_NO_RELOCS (buf);
          if ((sec->flags & SEC_LINKER_CREATED) == 0 || cookie->rels != NULL)
            {
              asection *rsec;

              REQUIRE (GET_RELOC (buf));

              /* Chain together the FDEs for each section.  */
              rsec = _bfd_elf_gc_mark_rsec (info, sec, gc_mark_hook,
                                            cookie, NULL);
              /* RSEC will be NULL if FDE was cleared out as it was belonging to
                 a discarded SHT_GROUP.  */
              if (rsec)
                {
                  REQUIRE (rsec->owner == abfd);
                  this_inf->u.fde.next_for_section = elf_fde_list (rsec);
                  elf_fde_list (rsec) = this_inf;
                }
            }

          /* Skip the initial location and address range.  */
          start = buf;
          length = get_DW_EH_PE_width (cie->fde_encoding, ptr_size);
          REQUIRE (skip_bytes (&buf, end, 2 * length));

          SKIP_RELOCS (buf - length);
          if (!GET_RELOC (buf - length)
              && read_value (abfd, buf - length, length, FALSE) == 0)
            {
              (*info->callbacks->minfo)
                /* xgettext:c-format */
                (_("discarding zero address range FDE in %B(%A).\n"),
                 abfd, sec);
              this_inf->u.fde.cie_inf = NULL;
            }

          /* Skip the augmentation size, if present.  */
          if (cie->augmentation[0] == 'z')
            REQUIRE (read_uleb128 (&buf, end, &length));
          else
            length = 0;

          /* Of the supported augmentation characters above, only 'L'
             adds augmentation data to the FDE.  This code would need to
             be adjusted if any future augmentations do the same thing.  */
          if (cie->lsda_encoding != DW_EH_PE_omit)
            {
              SKIP_RELOCS (buf);
              if (cie->can_make_lsda_relative && GET_RELOC (buf))
                cie->cie_inf->u.cie.make_lsda_relative = 1;
              this_inf->lsda_offset = buf - start;
              /* If there's no 'z' augmentation, we don't know where the
                 CFA insns begin.  Assume no padding.  */
              if (cie->augmentation[0] != 'z')
                length = end - buf;
            }

          /* Skip over the augmentation data.  */
          REQUIRE (skip_bytes (&buf, end, length));
          insns = buf;

          buf = last_fde + 4 + hdr_length;

          /* For NULL RSEC (cleared FDE belonging to a discarded section)
             the relocations are commonly cleared.  We do not sanity check if
             all these relocations are cleared as (1) relocations to
             .gcc_except_table will remain uncleared (they will get dropped
             with the drop of this unused FDE) and (2) BFD already safely drops
             relocations of any type to .eh_frame by
             elf_section_ignore_discarded_relocs.
             TODO: The .gcc_except_table entries should be also filtered as
             .eh_frame entries; or GCC could rather use COMDAT for them.  */
          SKIP_RELOCS (buf);
        }

      /* Try to interpret the CFA instructions and find the first
         padding nop.  Shrink this_inf's size so that it doesn't
         include the padding.  */
      length = get_DW_EH_PE_width (cie->fde_encoding, ptr_size);
      set_loc_count = 0;
      insns_end = skip_non_nops (insns, end, length, &set_loc_count);
      /* If we don't understand the CFA instructions, we can't know
         what needs to be adjusted there.  */
      if (insns_end == NULL
          /* For the time being we don't support DW_CFA_set_loc in
             CIE instructions.  */
          || (set_loc_count && this_inf->cie))
        goto free_no_table;
      this_inf->size -= end - insns_end;
      if (insns_end != end && this_inf->cie)
        {
          cie->initial_insn_length -= end - insns_end;
          cie->length -= end - insns_end;
        }
      if (set_loc_count
          && ((cie->fde_encoding & 0x70) == DW_EH_PE_pcrel
              || this_inf->make_relative))
        {
          unsigned int cnt;
          bfd_byte *p;

          this_inf->set_loc = (unsigned int *)
              bfd_malloc ((set_loc_count + 1) * sizeof (unsigned int));
          REQUIRE (this_inf->set_loc);
          this_inf->set_loc[0] = set_loc_count;
          p = insns;
          cnt = 0;
          while (p < end)
            {
              if (*p == DW_CFA_set_loc)
                this_inf->set_loc[++cnt] = p + 1 - start;
              REQUIRE (skip_cfa_op (&p, end, length));
            }
        }

      this_inf->removed = 1;
      this_inf->fde_encoding = cie->fde_encoding;
      this_inf->lsda_encoding = cie->lsda_encoding;
      sec_info->count++;
    }
  BFD_ASSERT (sec_info->count == num_entries);
  BFD_ASSERT (cie_count == num_cies);

  elf_section_data (sec)->sec_info = sec_info;
  sec->sec_info_type = SEC_INFO_TYPE_EH_FRAME;
  if (!bfd_link_relocatable (info))
    {
      /* Keep info for merging cies.  */
      sec_info->cies = local_cies;
      local_cies = NULL;
    }
  goto success;

 free_no_table:
  (*info->callbacks->einfo)
    /* xgettext:c-format */
    (_("%P: error in %B(%A); no .eh_frame_hdr table will be created.\n"),
     abfd, sec);
  hdr_info->u.dwarf.table = FALSE;
  if (sec_info)
    free (sec_info);
 success:
  if (ehbuf)
    free (ehbuf);
  if (local_cies)
    free (local_cies);
#undef REQUIRE
}

/* Order eh_frame_hdr entries by the VMA of their text section.  */

static int
cmp_eh_frame_hdr (const void *a, const void *b)
{
  bfd_vma text_a;
  bfd_vma text_b;
  asection *sec;

  sec = *(asection *const *)a;
  sec = (asection *) elf_section_data (sec)->sec_info;
  text_a = sec->output_section->vma + sec->output_offset;
  sec = *(asection *const *)b;
  sec = (asection *) elf_section_data (sec)->sec_info;
  text_b = sec->output_section->vma + sec->output_offset;

  if (text_a < text_b)
    return -1;
  return text_a > text_b;

}

/* Add space for a CANTUNWIND terminator to SEC if the text sections
   referenced by it and NEXT are not contiguous, or NEXT is NULL.  */

static void
add_eh_frame_hdr_terminator (asection *sec,
                             asection *next)
{
  bfd_vma end;
  bfd_vma next_start;
  asection *text_sec;

  if (next)
    {
      /* See if there is a gap (presumably a text section without unwind info)
         between these two entries.  */
      text_sec = (asection *) elf_section_data (sec)->sec_info;
      end = text_sec->output_section->vma + text_sec->output_offset
            + text_sec->size;
      text_sec = (asection *) elf_section_data (next)->sec_info;
      next_start = text_sec->output_section->vma + text_sec->output_offset;
      if (end == next_start)
        return;
    }

  /* Add space for a CANTUNWIND terminator.  */
  if (!sec->rawsize)
    sec->rawsize = sec->size;

  bfd_set_section_size (sec->owner, sec, sec->size + 8);
}

/* Finish a pass over all .eh_frame_entry sections.  */

bfd_boolean
_bfd_elf_end_eh_frame_parsing (struct bfd_link_info *info)
{
  struct eh_frame_hdr_info *hdr_info;
  unsigned int i;

  hdr_info = &elf_hash_table (info)->eh_info;

  if (info->eh_frame_hdr_type != COMPACT_EH_HDR
      || hdr_info->array_count == 0)
    return FALSE;

  bfd_elf_discard_eh_frame_entry (hdr_info);

  qsort (hdr_info->u.compact.entries, hdr_info->array_count,
         sizeof (asection *), cmp_eh_frame_hdr);

  for (i = 0; i < hdr_info->array_count - 1; i++)
    {
      add_eh_frame_hdr_terminator (hdr_info->u.compact.entries[i],
                                   hdr_info->u.compact.entries[i + 1]);
    }

  /* Add a CANTUNWIND terminator after the last entry.  */
  add_eh_frame_hdr_terminator (hdr_info->u.compact.entries[i], NULL);
  return TRUE;
}

/* Mark all relocations against CIE or FDE ENT, which occurs in
   .eh_frame section SEC.  COOKIE describes the relocations in SEC;
   its "rel" field can be changed freely.  */

static bfd_boolean
mark_entry (struct bfd_link_info *info, asection *sec,
            struct eh_cie_fde *ent, elf_gc_mark_hook_fn gc_mark_hook,
            struct elf_reloc_cookie *cookie)
{
  /* FIXME: octets_per_byte.  */
  for (cookie->rel = cookie->rels + ent->reloc_index;
       cookie->rel < cookie->relend
         && cookie->rel->r_offset < ent->offset + ent->size;
       cookie->rel++)
    if (!_bfd_elf_gc_mark_reloc (info, sec, gc_mark_hook, cookie))
      return FALSE;

  return TRUE;
}

/* Mark all the relocations against FDEs that relate to code in input
   section SEC.  The FDEs belong to .eh_frame section EH_FRAME, whose
   relocations are described by COOKIE.  */

bfd_boolean
_bfd_elf_gc_mark_fdes (struct bfd_link_info *info, asection *sec,
                       asection *eh_frame, elf_gc_mark_hook_fn gc_mark_hook,
                       struct elf_reloc_cookie *cookie)
{
  struct eh_cie_fde *fde, *cie;

  for (fde = elf_fde_list (sec); fde; fde = fde->u.fde.next_for_section)
    {
      if (!mark_entry (info, eh_frame, fde, gc_mark_hook, cookie))
        return FALSE;

      /* At this stage, all cie_inf fields point to local CIEs, so we
         can use the same cookie to refer to them.  */
      cie = fde->u.fde.cie_inf;
      if (cie != NULL && !cie->u.cie.gc_mark)
        {
          cie->u.cie.gc_mark = 1;
          if (!mark_entry (info, eh_frame, cie, gc_mark_hook, cookie))
            return FALSE;
        }
    }
  return TRUE;
}

/* Input section SEC of ABFD is an .eh_frame section that contains the
   CIE described by CIE_INF.  Return a version of CIE_INF that is going
   to be kept in the output, adding CIE_INF to the output if necessary.

   HDR_INFO is the .eh_frame_hdr information and COOKIE describes the
   relocations in REL.  */

static struct eh_cie_fde *
find_merged_cie (bfd *abfd, struct bfd_link_info *info, asection *sec,
                 struct eh_frame_hdr_info *hdr_info,
                 struct elf_reloc_cookie *cookie,
                 struct eh_cie_fde *cie_inf)
{
  unsigned long r_symndx;
  struct cie *cie, *new_cie;
  Elf_Internal_Rela *rel;
  void **loc;

  /* Use CIE_INF if we have already decided to keep it.  */
  if (!cie_inf->removed)
    return cie_inf;

  /* If we have merged CIE_INF with another CIE, use that CIE instead.  */
  if (cie_inf->u.cie.merged)
    return cie_inf->u.cie.u.merged_with;

  cie = cie_inf->u.cie.u.full_cie;

  /* Assume we will need to keep CIE_INF.  */
  cie_inf->removed = 0;
  cie_inf->u.cie.u.sec = sec;

  /* If we are not merging CIEs, use CIE_INF.  */
  if (cie == NULL)
    return cie_inf;

  if (cie->per_encoding != DW_EH_PE_omit)
    {
      bfd_boolean per_binds_local;

      /* Work out the address of personality routine, or at least
         enough info that we could calculate the address had we made a
         final section layout.  The symbol on the reloc is enough,
         either the hash for a global, or (bfd id, index) pair for a
         local.  The assumption here is that no one uses addends on
         the reloc.  */
      rel = cookie->rels + cie->personality.reloc_index;
      memset (&cie->personality, 0, sizeof (cie->personality));
#ifdef BFD64
      if (elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64)
        r_symndx = ELF64_R_SYM (rel->r_info);
      else
#endif
        r_symndx = ELF32_R_SYM (rel->r_info);
      if (r_symndx >= cookie->locsymcount
          || ELF_ST_BIND (cookie->locsyms[r_symndx].st_info) != STB_LOCAL)
        {
          struct elf_link_hash_entry *h;

          r_symndx -= cookie->extsymoff;
          h = cookie->sym_hashes[r_symndx];

          while (h->root.type == bfd_link_hash_indirect
                 || h->root.type == bfd_link_hash_warning)
            h = (struct elf_link_hash_entry *) h->root.u.i.link;

          cie->personality.h = h;
          per_binds_local = SYMBOL_REFERENCES_LOCAL (info, h);
        }
      else
        {
          Elf_Internal_Sym *sym;
          asection *sym_sec;

          sym = &cookie->locsyms[r_symndx];
          sym_sec = bfd_section_from_elf_index (abfd, sym->st_shndx);
          if (sym_sec == NULL)
            return cie_inf;

          if (sym_sec->kept_section != NULL)
            sym_sec = sym_sec->kept_section;
          if (sym_sec->output_section == NULL)
            return cie_inf;

          cie->local_personality = 1;
          cie->personality.sym.bfd_id = abfd->id;
          cie->personality.sym.index = r_symndx;
          per_binds_local = TRUE;
        }

      if (per_binds_local
          && bfd_link_pic (info)
          && (cie->per_encoding & 0x70) == DW_EH_PE_absptr
          && (get_elf_backend_data (abfd)
              ->elf_backend_can_make_relative_eh_frame (abfd, info, sec)))
        {
          cie_inf->u.cie.make_per_encoding_relative = 1;
          cie_inf->u.cie.per_encoding_relative = 1;
        }
    }

  /* See if we can merge this CIE with an earlier one.  */
  cie_compute_hash (cie);
  if (hdr_info->u.dwarf.cies == NULL)
    {
      hdr_info->u.dwarf.cies = htab_try_create (1, cie_hash, cie_eq, free);
      if (hdr_info->u.dwarf.cies == NULL)
        return cie_inf;
    }
  loc = htab_find_slot_with_hash (hdr_info->u.dwarf.cies, cie,
                                  cie->hash, INSERT);
  if (loc == NULL)
    return cie_inf;

  new_cie = (struct cie *) *loc;
  if (new_cie == NULL)
    {
      /* Keep CIE_INF and record it in the hash table.  */
      new_cie = (struct cie *) malloc (sizeof (struct cie));
      if (new_cie == NULL)
        return cie_inf;

      memcpy (new_cie, cie, sizeof (struct cie));
      *loc = new_cie;
    }
  else
    {
      /* Merge CIE_INF with NEW_CIE->CIE_INF.  */
      cie_inf->removed = 1;
      cie_inf->u.cie.merged = 1;
      cie_inf->u.cie.u.merged_with = new_cie->cie_inf;
      if (cie_inf->u.cie.make_lsda_relative)
        new_cie->cie_inf->u.cie.make_lsda_relative = 1;
    }
  return new_cie->cie_inf;
}

/* This function is called for each input file before the .eh_frame
   section is relocated.  It discards duplicate CIEs and FDEs for discarded
   functions.  The function returns TRUE iff any entries have been
   deleted.  */

bfd_boolean
_bfd_elf_discard_section_eh_frame
   (bfd *abfd, struct bfd_link_info *info, asection *sec,
    bfd_boolean (*reloc_symbol_deleted_p) (bfd_vma, void *),
    struct elf_reloc_cookie *cookie)
{
  struct eh_cie_fde *ent;
  struct eh_frame_sec_info *sec_info;
  struct eh_frame_hdr_info *hdr_info;
  unsigned int ptr_size, offset, eh_alignment;

  if (sec->sec_info_type != SEC_INFO_TYPE_EH_FRAME)
    return FALSE;

  sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info;
  if (sec_info == NULL)
    return FALSE;

  ptr_size = (get_elf_backend_data (sec->owner)
              ->elf_backend_eh_frame_address_size (sec->owner, sec));

  hdr_info = &elf_hash_table (info)->eh_info;
  for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent)
    if (ent->size == 4)
      /* There should only be one zero terminator, on the last input
         file supplying .eh_frame (crtend.o).  Remove any others.  */
      ent->removed = sec->map_head.s != NULL;
    else if (!ent->cie && ent->u.fde.cie_inf != NULL)
      {
        bfd_boolean keep;
        if ((sec->flags & SEC_LINKER_CREATED) != 0 && cookie->rels == NULL)
          {
            unsigned int width
              = get_DW_EH_PE_width (ent->fde_encoding, ptr_size);
            bfd_vma value
              = read_value (abfd, sec->contents + ent->offset + 8 + width,
                            width, get_DW_EH_PE_signed (ent->fde_encoding));
            keep = value != 0;
          }
        else
          {
            cookie->rel = cookie->rels + ent->reloc_index;
            /* FIXME: octets_per_byte.  */
            BFD_ASSERT (cookie->rel < cookie->relend
                        && cookie->rel->r_offset == ent->offset + 8);
            keep = !(*reloc_symbol_deleted_p) (ent->offset + 8, cookie);
          }
        if (keep)
          {
            if (bfd_link_pic (info)
                && (((ent->fde_encoding & 0x70) == DW_EH_PE_absptr
                     && ent->make_relative == 0)
                    || (ent->fde_encoding & 0x70) == DW_EH_PE_aligned))
              {
                static int num_warnings_issued = 0;

                /* If a shared library uses absolute pointers
                   which we cannot turn into PC relative,
                   don't create the binary search table,
                   since it is affected by runtime relocations.  */
                hdr_info->u.dwarf.table = FALSE;
                if (num_warnings_issued < 10)
                  {
                    (*info->callbacks->einfo)
                      /* xgettext:c-format */
                      (_("%P: FDE encoding in %B(%A) prevents .eh_frame_hdr"
                         " table being created.\n"), abfd, sec);
                    num_warnings_issued ++;
                  }
                else if (num_warnings_issued == 10)
                  {
                    (*info->callbacks->einfo)
                      (_("%P: Further warnings about FDE encoding preventing .eh_frame_hdr generation dropped.\n"));
                    num_warnings_issued ++;
                  }
              }
            ent->removed = 0;
            hdr_info->u.dwarf.fde_count++;
            ent->u.fde.cie_inf = find_merged_cie (abfd, info, sec, hdr_info,
                                                  cookie, ent->u.fde.cie_inf);
          }
      }

  if (sec_info->cies)
    {
      free (sec_info->cies);
      sec_info->cies = NULL;
    }

  /* It may be that some .eh_frame input section has greater alignment
     than other .eh_frame sections.  In that case we run the risk of
     padding with zeros before that section, which would be seen as a
     zero terminator.  Alignment padding must be added *inside* the
     last FDE instead.  For other FDEs we align according to their
     encoding, in order to align FDE address range entries naturally.  */
  offset = 0;
  for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent)
    if (!ent->removed)
      {
        eh_alignment = 4;
        if (ent->size == 4)
          ;
        else if (ent->cie)
          {
            if (ent->u.cie.per_encoding_aligned8)
              eh_alignment = 8;
          }
        else
          {
            eh_alignment = get_DW_EH_PE_width (ent->fde_encoding, ptr_size);
            if (eh_alignment < 4)
              eh_alignment = 4;
          }
        offset = (offset + eh_alignment - 1) & -eh_alignment;
        ent->new_offset = offset;
        offset += size_of_output_cie_fde (ent);
      }

  /* Pad the last FDE out to the output section alignment if there are
     following sections, in order to ensure no padding between this
     section and the next.  (Relies on the output section alignment
     being the maximum of all input sections alignments, which is the
     case unless someone is overriding alignment via scripts.)  */
  eh_alignment = 4;
  if (sec->map_head.s != NULL
      && (sec->map_head.s->size != 4
          || sec->map_head.s->map_head.s != NULL))
    eh_alignment = 1 << sec->output_section->alignment_power;
  offset = (offset + eh_alignment - 1) & -eh_alignment;
  sec->rawsize = sec->size;
  sec->size = offset;
  return offset != sec->rawsize;
}

/* This function is called for .eh_frame_hdr section after
   _bfd_elf_discard_section_eh_frame has been called on all .eh_frame
   input sections.  It finalizes the size of .eh_frame_hdr section.  */

bfd_boolean
_bfd_elf_discard_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  asection *sec;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;

  if (!hdr_info->frame_hdr_is_compact && hdr_info->u.dwarf.cies != NULL)
    {
      htab_delete (hdr_info->u.dwarf.cies);
      hdr_info->u.dwarf.cies = NULL;
    }

  sec = hdr_info->hdr_sec;
  if (sec == NULL)
    return FALSE;

  if (info->eh_frame_hdr_type == COMPACT_EH_HDR)
    {
      /* For compact frames we only add the header.  The actual table comes
         from the .eh_frame_entry sections.  */
      sec->size = 8;
    }
  else
    {
      sec->size = EH_FRAME_HDR_SIZE;
      if (hdr_info->u.dwarf.table)
        sec->size += 4 + hdr_info->u.dwarf.fde_count * 8;
    }

  elf_eh_frame_hdr (abfd) = sec;
  return TRUE;
}

/* Return true if there is at least one non-empty .eh_frame section in
   input files.  Can only be called after ld has mapped input to
   output sections, and before sections are stripped.  */

bfd_boolean
_bfd_elf_eh_frame_present (struct bfd_link_info *info)
{
  asection *eh = bfd_get_section_by_name (info->output_bfd, ".eh_frame");

  if (eh == NULL)
    return FALSE;

  /* Count only sections which have at least a single CIE or FDE.
     There cannot be any CIE or FDE <= 8 bytes.  */
  for (eh = eh->map_head.s; eh != NULL; eh = eh->map_head.s)
    if (eh->size > 8)
      return TRUE;

  return FALSE;
}

/* Return true if there is at least one .eh_frame_entry section in
   input files.  */

bfd_boolean
_bfd_elf_eh_frame_entry_present (struct bfd_link_info *info)
{
  asection *o;
  bfd *abfd;

  for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link.next)
    {
      for (o = abfd->sections; o; o = o->next)
        {
          const char *name = bfd_get_section_name (abfd, o);

          if (strcmp (name, ".eh_frame_entry")
              && !bfd_is_abs_section (o->output_section))
            return TRUE;
        }
    }
  return FALSE;
}

/* This function is called from size_dynamic_sections.
   It needs to decide whether .eh_frame_hdr should be output or not,
   because when the dynamic symbol table has been sized it is too late
   to strip sections.  */

bfd_boolean
_bfd_elf_maybe_strip_eh_frame_hdr (struct bfd_link_info *info)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  struct bfd_link_hash_entry *bh = NULL;
  struct elf_link_hash_entry *h;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;
  if (hdr_info->hdr_sec == NULL)
    return TRUE;

  if (bfd_is_abs_section (hdr_info->hdr_sec->output_section)
      || info->eh_frame_hdr_type == 0
      || (info->eh_frame_hdr_type == DWARF2_EH_HDR
          && !_bfd_elf_eh_frame_present (info))
      || (info->eh_frame_hdr_type == COMPACT_EH_HDR
          && !_bfd_elf_eh_frame_entry_present (info)))
    {
      hdr_info->hdr_sec->flags |= SEC_EXCLUDE;
      hdr_info->hdr_sec = NULL;
      return TRUE;
    }

  /* Add a hidden symbol so that systems without access to PHDRs can
     find the table.  */
  if (! (_bfd_generic_link_add_one_symbol
         (info, info->output_bfd, "__GNU_EH_FRAME_HDR", BSF_LOCAL,
          hdr_info->hdr_sec, 0, NULL, FALSE, FALSE, &bh)))
    return FALSE;

  h = (struct elf_link_hash_entry *) bh;
  h->def_regular = 1;
  h->other = STV_HIDDEN;
  get_elf_backend_data
    (info->output_bfd)->elf_backend_hide_symbol (info, h, TRUE);

  if (!hdr_info->frame_hdr_is_compact)
    hdr_info->u.dwarf.table = TRUE;
  return TRUE;
}

/* Adjust an address in the .eh_frame section.  Given OFFSET within
   SEC, this returns the new offset in the adjusted .eh_frame section,
   or -1 if the address refers to a CIE/FDE which has been removed
   or to offset with dynamic relocation which is no longer needed.  */

bfd_vma
_bfd_elf_eh_frame_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED,
                                  struct bfd_link_info *info ATTRIBUTE_UNUSED,
                                  asection *sec,
                                  bfd_vma offset)
{
  struct eh_frame_sec_info *sec_info;
  unsigned int lo, hi, mid;

  if (sec->sec_info_type != SEC_INFO_TYPE_EH_FRAME)
    return offset;
  sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info;

  if (offset >= sec->rawsize)
    return offset - sec->rawsize + sec->size;

  lo = 0;
  hi = sec_info->count;
  mid = 0;
  while (lo < hi)
    {
      mid = (lo + hi) / 2;
      if (offset < sec_info->entry[mid].offset)
        hi = mid;
      else if (offset
               >= sec_info->entry[mid].offset + sec_info->entry[mid].size)
        lo = mid + 1;
      else
        break;
    }

  BFD_ASSERT (lo < hi);

  /* FDE or CIE was removed.  */
  if (sec_info->entry[mid].removed)
    return (bfd_vma) -1;

  /* If converting personality pointers to DW_EH_PE_pcrel, there will be
     no need for run-time relocation against the personality field.  */
  if (sec_info->entry[mid].cie
      && sec_info->entry[mid].u.cie.make_per_encoding_relative
      && offset == (sec_info->entry[mid].offset + 8
                    + sec_info->entry[mid].u.cie.personality_offset))
    return (bfd_vma) -2;

  /* If converting to DW_EH_PE_pcrel, there will be no need for run-time
     relocation against FDE's initial_location field.  */
  if (!sec_info->entry[mid].cie
      && sec_info->entry[mid].make_relative
      && offset == sec_info->entry[mid].offset + 8)
    return (bfd_vma) -2;

  /* If converting LSDA pointers to DW_EH_PE_pcrel, there will be no need
     for run-time relocation against LSDA field.  */
  if (!sec_info->entry[mid].cie
      && sec_info->entry[mid].u.fde.cie_inf->u.cie.make_lsda_relative
      && offset == (sec_info->entry[mid].offset + 8
                    + sec_info->entry[mid].lsda_offset))
    return (bfd_vma) -2;

  /* If converting to DW_EH_PE_pcrel, there will be no need for run-time
     relocation against DW_CFA_set_loc's arguments.  */
  if (sec_info->entry[mid].set_loc
      && sec_info->entry[mid].make_relative
      && (offset >= sec_info->entry[mid].offset + 8
                    + sec_info->entry[mid].set_loc[1]))
    {
      unsigned int cnt;

      for (cnt = 1; cnt <= sec_info->entry[mid].set_loc[0]; cnt++)
        if (offset == sec_info->entry[mid].offset + 8
                      + sec_info->entry[mid].set_loc[cnt])
          return (bfd_vma) -2;
    }

  /* Any new augmentation bytes go before the first relocation.  */
  return (offset + sec_info->entry[mid].new_offset
          - sec_info->entry[mid].offset
          + extra_augmentation_string_bytes (sec_info->entry + mid)
          + extra_augmentation_data_bytes (sec_info->entry + mid));
}

/* Write out .eh_frame_entry section.  Add CANTUNWIND terminator if needed.
   Also check that the contents look sane.  */

bfd_boolean
_bfd_elf_write_section_eh_frame_entry (bfd *abfd, struct bfd_link_info *info,
                                       asection *sec, bfd_byte *contents)
{
  const struct elf_backend_data *bed;
  bfd_byte cantunwind[8];
  bfd_vma addr;
  bfd_vma last_addr;
  bfd_vma offset;
  asection *text_sec = (asection *) elf_section_data (sec)->sec_info;

  if (!sec->rawsize)
    sec->rawsize = sec->size;

  BFD_ASSERT (sec->sec_info_type == SEC_INFO_TYPE_EH_FRAME_ENTRY);

  /* Check to make sure that the text section corresponding to this eh_frame_entry
     section has not been excluded.  In particular, mips16 stub entries will be
     excluded outside of the normal process.  */
  if (sec->flags & SEC_EXCLUDE
      || text_sec->flags & SEC_EXCLUDE)
    return TRUE;

  if (!bfd_set_section_contents (abfd, sec->output_section, contents,
                                 sec->output_offset, sec->rawsize))
      return FALSE;

  last_addr = bfd_get_signed_32 (abfd, contents);
  /* Check that all the entries are in order.  */
  for (offset = 8; offset < sec->rawsize; offset += 8)
    {
      addr = bfd_get_signed_32 (abfd, contents + offset) + offset;
      if (addr <= last_addr)
        {
          /* xgettext:c-format */
          _bfd_error_handler (_("%B: %A not in order"), sec->owner, sec);
          return FALSE;
        }

      last_addr = addr;
    }

  addr = text_sec->output_section->vma + text_sec->output_offset
         + text_sec->size;
  addr &= ~1;
  addr -= (sec->output_section->vma + sec->output_offset + sec->rawsize);
  if (addr & 1)
    {
      /* xgettext:c-format */
      _bfd_error_handler (_("%B: %A invalid input section size"),
                          sec->owner, sec);
      bfd_set_error (bfd_error_bad_value);
      return FALSE;
    }
  if (last_addr >= addr + sec->rawsize)
    {
      /* xgettext:c-format */
      _bfd_error_handler (_("%B: %A points past end of text section"),
                          sec->owner, sec);
      bfd_set_error (bfd_error_bad_value);
      return FALSE;
    }

  if (sec->size == sec->rawsize)
    return TRUE;

  bed = get_elf_backend_data (abfd);
  BFD_ASSERT (sec->size == sec->rawsize + 8);
  BFD_ASSERT ((addr & 1) == 0);
  BFD_ASSERT (bed->cant_unwind_opcode);

  bfd_put_32 (abfd, addr, cantunwind);
  bfd_put_32 (abfd, (*bed->cant_unwind_opcode) (info), cantunwind + 4);
  return bfd_set_section_contents (abfd, sec->output_section, cantunwind,
                                   sec->output_offset + sec->rawsize, 8);
}

/* Write out .eh_frame section.  This is called with the relocated
   contents.  */

bfd_boolean
_bfd_elf_write_section_eh_frame (bfd *abfd,
                                 struct bfd_link_info *info,
                                 asection *sec,
                                 bfd_byte *contents)
{
  struct eh_frame_sec_info *sec_info;
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  unsigned int ptr_size;
  struct eh_cie_fde *ent, *last_ent;

  if (sec->sec_info_type != SEC_INFO_TYPE_EH_FRAME)
    /* FIXME: octets_per_byte.  */
    return bfd_set_section_contents (abfd, sec->output_section, contents,
                                     sec->output_offset, sec->size);

  ptr_size = (get_elf_backend_data (abfd)
              ->elf_backend_eh_frame_address_size (abfd, sec));
  BFD_ASSERT (ptr_size != 0);

  sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info;
  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;

  if (hdr_info->u.dwarf.table && hdr_info->u.dwarf.array == NULL)
    {
      hdr_info->frame_hdr_is_compact = FALSE;
      hdr_info->u.dwarf.array = (struct eh_frame_array_ent *)
        bfd_malloc (hdr_info->u.dwarf.fde_count
                    * sizeof (*hdr_info->u.dwarf.array));
    }
  if (hdr_info->u.dwarf.array == NULL)
    hdr_info = NULL;

  /* The new offsets can be bigger or smaller than the original offsets.
     We therefore need to make two passes over the section: one backward
     pass to move entries up and one forward pass to move entries down.
     The two passes won't interfere with each other because entries are
     not reordered  */
  for (ent = sec_info->entry + sec_info->count; ent-- != sec_info->entry;)
    if (!ent->removed && ent->new_offset > ent->offset)
      memmove (contents + ent->new_offset, contents + ent->offset, ent->size);

  for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent)
    if (!ent->removed && ent->new_offset < ent->offset)
      memmove (contents + ent->new_offset, contents + ent->offset, ent->size);

  last_ent = sec_info->entry + sec_info->count;
  for (ent = sec_info->entry; ent < last_ent; ++ent)
    {
      unsigned char *buf, *end;
      unsigned int new_size;

      if (ent->removed)
        continue;

      if (ent->size == 4)
        {
          /* Any terminating FDE must be at the end of the section.  */
          BFD_ASSERT (ent == last_ent - 1);
          continue;
        }

      buf = contents + ent->new_offset;
      end = buf + ent->size;
      new_size = next_cie_fde_offset (ent, last_ent, sec) - ent->new_offset;

      /* Update the size.  It may be shrinked.  */
      bfd_put_32 (abfd, new_size - 4, buf);

      /* Filling the extra bytes with DW_CFA_nops.  */
      if (new_size != ent->size)
        memset (end, 0, new_size - ent->size);

      if (ent->cie)
        {
          /* CIE */
          if (ent->make_relative
              || ent->u.cie.make_lsda_relative
              || ent->u.cie.per_encoding_relative)
            {
              char *aug;
              unsigned int action, extra_string, extra_data;
              unsigned int per_width, per_encoding;

              /* Need to find 'R' or 'L' augmentation's argument and modify
                 DW_EH_PE_* value.  */
              action = ((ent->make_relative ? 1 : 0)
                        | (ent->u.cie.make_lsda_relative ? 2 : 0)
                        | (ent->u.cie.per_encoding_relative ? 4 : 0));
              extra_string = extra_augmentation_string_bytes (ent);
              extra_data = extra_augmentation_data_bytes (ent);

              /* Skip length, id and version.  */
              buf += 9;
              aug = (char *) buf;
              buf += strlen (aug) + 1;
              skip_leb128 (&buf, end);
              skip_leb128 (&buf, end);
              skip_leb128 (&buf, end);
              if (*aug == 'z')
                {
                  /* The uleb128 will always be a single byte for the kind
                     of augmentation strings that we're prepared to handle.  */
                  *buf++ += extra_data;
                  aug++;
                }

              /* Make room for the new augmentation string and data bytes.  */
              memmove (buf + extra_string + extra_data, buf, end - buf);
              memmove (aug + extra_string, aug, buf - (bfd_byte *) aug);
              buf += extra_string;
              end += extra_string + extra_data;

              if (ent->add_augmentation_size)
                {
                  *aug++ = 'z';
                  *buf++ = extra_data - 1;
                }
              if (ent->u.cie.add_fde_encoding)
                {
                  BFD_ASSERT (action & 1);
                  *aug++ = 'R';
                  *buf++ = make_pc_relative (DW_EH_PE_absptr, ptr_size);
                  action &= ~1;
                }

              while (action)
                switch (*aug++)
                  {
                  case 'L':
                    if (action & 2)
                      {
                        BFD_ASSERT (*buf == ent->lsda_encoding);
                        *buf = make_pc_relative (*buf, ptr_size);
                        action &= ~2;
                      }
                    buf++;
                    break;
                  case 'P':
                    if (ent->u.cie.make_per_encoding_relative)
                      *buf = make_pc_relative (*buf, ptr_size);
                    per_encoding = *buf++;
                    per_width = get_DW_EH_PE_width (per_encoding, ptr_size);
                    BFD_ASSERT (per_width != 0);
                    BFD_ASSERT (((per_encoding & 0x70) == DW_EH_PE_pcrel)
                                == ent->u.cie.per_encoding_relative);
                    if ((per_encoding & 0x70) == DW_EH_PE_aligned)
                      buf = (contents
                             + ((buf - contents + per_width - 1)
                                & ~((bfd_size_type) per_width - 1)));
                    if (action & 4)
                      {
                        bfd_vma val;

                        val = read_value (abfd, buf, per_width,
                                          get_DW_EH_PE_signed (per_encoding));
                        if (ent->u.cie.make_per_encoding_relative)
                          val -= (sec->output_section->vma
                                  + sec->output_offset
                                  + (buf - contents));
                        else
                          {
                            val += (bfd_vma) ent->offset - ent->new_offset;
                            val -= extra_string + extra_data;
                          }
                        write_value (abfd, buf, val, per_width);
                        action &= ~4;
                      }
                    buf += per_width;
                    break;
                  case 'R':
                    if (action & 1)
                      {
                        BFD_ASSERT (*buf == ent->fde_encoding);
                        *buf = make_pc_relative (*buf, ptr_size);
                        action &= ~1;
                      }
                    buf++;
                    break;
                  case 'S':
                    break;
                  default:
                    BFD_FAIL ();
                  }
            }
        }
      else
        {
          /* FDE */
          bfd_vma value, address;
          unsigned int width;
          bfd_byte *start;
          struct eh_cie_fde *cie;

          /* Skip length.  */
          cie = ent->u.fde.cie_inf;
          buf += 4;
          value = ((ent->new_offset + sec->output_offset + 4)
                   - (cie->new_offset + cie->u.cie.u.sec->output_offset));
          bfd_put_32 (abfd, value, buf);
          if (bfd_link_relocatable (info))
            continue;
          buf += 4;
          width = get_DW_EH_PE_width (ent->fde_encoding, ptr_size);
          value = read_value (abfd, buf, width,
                              get_DW_EH_PE_signed (ent->fde_encoding));
          address = value;
          if (value)
            {
              switch (ent->fde_encoding & 0x70)
                {
                case DW_EH_PE_textrel:
                  BFD_ASSERT (hdr_info == NULL);
                  break;
                case DW_EH_PE_datarel:
                  {
                    switch (abfd->arch_info->arch)
                      {
                      case bfd_arch_ia64:
                        BFD_ASSERT (elf_gp (abfd) != 0);
                        address += elf_gp (abfd);
                        break;
                      default:
                        (*info->callbacks->einfo)
                          (_("%P: DW_EH_PE_datarel unspecified"
                             " for this architecture.\n"));
                        /* Fall thru */
                      case bfd_arch_frv:
                      case bfd_arch_i386:
                        BFD_ASSERT (htab->hgot != NULL
                                    && ((htab->hgot->root.type
                                         == bfd_link_hash_defined)
                                        || (htab->hgot->root.type
                                            == bfd_link_hash_defweak)));
                        address
                          += (htab->hgot->root.u.def.value
                              + htab->hgot->root.u.def.section->output_offset
                              + (htab->hgot->root.u.def.section->output_section
                                 ->vma));
                        break;
                      }
                  }
                  break;
                case DW_EH_PE_pcrel:
                  value += (bfd_vma) ent->offset - ent->new_offset;
                  address += (sec->output_section->vma
                              + sec->output_offset
                              + ent->offset + 8);
                  break;
                }
              if (ent->make_relative)
                value -= (sec->output_section->vma
                          + sec->output_offset
                          + ent->new_offset + 8);
              write_value (abfd, buf, value, width);
            }

          start = buf;

          if (hdr_info)
            {
              /* The address calculation may overflow, giving us a
                 value greater than 4G on a 32-bit target when
                 dwarf_vma is 64-bit.  */
              if (sizeof (address) > 4 && ptr_size == 4)
                address &= 0xffffffff;
              hdr_info->u.dwarf.array[hdr_info->array_count].initial_loc
                = address;
              hdr_info->u.dwarf.array[hdr_info->array_count].range
                = read_value (abfd, buf + width, width, FALSE);
              hdr_info->u.dwarf.array[hdr_info->array_count++].fde
                = (sec->output_section->vma
                   + sec->output_offset
                   + ent->new_offset);
            }

          if ((ent->lsda_encoding & 0x70) == DW_EH_PE_pcrel
              || cie->u.cie.make_lsda_relative)
            {
              buf += ent->lsda_offset;
              width = get_DW_EH_PE_width (ent->lsda_encoding, ptr_size);
              value = read_value (abfd, buf, width,
                                  get_DW_EH_PE_signed (ent->lsda_encoding));
              if (value)
                {
                  if ((ent->lsda_encoding & 0x70) == DW_EH_PE_pcrel)
                    value += (bfd_vma) ent->offset - ent->new_offset;
                  else if (cie->u.cie.make_lsda_relative)
                    value -= (sec->output_section->vma
                              + sec->output_offset
                              + ent->new_offset + 8 + ent->lsda_offset);
                  write_value (abfd, buf, value, width);
                }
            }
          else if (ent->add_augmentation_size)
            {
              /* Skip the PC and length and insert a zero byte for the
                 augmentation size.  */
              buf += width * 2;
              memmove (buf + 1, buf, end - buf);
              *buf = 0;
            }

          if (ent->set_loc)
            {
              /* Adjust DW_CFA_set_loc.  */
              unsigned int cnt;
              bfd_vma new_offset;

              width = get_DW_EH_PE_width (ent->fde_encoding, ptr_size);
              new_offset = ent->new_offset + 8
                           + extra_augmentation_string_bytes (ent)
                           + extra_augmentation_data_bytes (ent);

              for (cnt = 1; cnt <= ent->set_loc[0]; cnt++)
                {
                  buf = start + ent->set_loc[cnt];

                  value = read_value (abfd, buf, width,
                                      get_DW_EH_PE_signed (ent->fde_encoding));
                  if (!value)
                    continue;

                  if ((ent->fde_encoding & 0x70) == DW_EH_PE_pcrel)
                    value += (bfd_vma) ent->offset + 8 - new_offset;
                  if (ent->make_relative)
                    value -= (sec->output_section->vma
                              + sec->output_offset
                              + new_offset + ent->set_loc[cnt]);
                  write_value (abfd, buf, value, width);
                }
            }
        }
    }

  /* FIXME: octets_per_byte.  */
  return bfd_set_section_contents (abfd, sec->output_section,
                                   contents, (file_ptr) sec->output_offset,
                                   sec->size);
}

/* Helper function used to sort .eh_frame_hdr search table by increasing
   VMA of FDE initial location.  */

static int
vma_compare (const void *a, const void *b)
{
  const struct eh_frame_array_ent *p = (const struct eh_frame_array_ent *) a;
  const struct eh_frame_array_ent *q = (const struct eh_frame_array_ent *) b;
  if (p->initial_loc > q->initial_loc)
    return 1;
  if (p->initial_loc < q->initial_loc)
    return -1;
  if (p->range > q->range)
    return 1;
  if (p->range < q->range)
    return -1;
  return 0;
}

/* Reorder .eh_frame_entry sections to match the associated text sections.
   This routine is called during the final linking step, just before writing
   the contents.  At this stage, sections in the eh_frame_hdr_info are already
   sorted in order of increasing text section address and so we simply need
   to make the .eh_frame_entrys follow that same order.  Note that it is
   invalid for a linker script to try to force a particular order of
   .eh_frame_entry sections.  */

bfd_boolean
_bfd_elf_fixup_eh_frame_hdr (struct bfd_link_info *info)
{
  asection *sec = NULL;
  asection *osec;
  struct eh_frame_hdr_info *hdr_info;
  unsigned int i;
  bfd_vma offset;
  struct bfd_link_order *p;

  hdr_info = &elf_hash_table (info)->eh_info;

  if (hdr_info->hdr_sec == NULL
      || info->eh_frame_hdr_type != COMPACT_EH_HDR
      || hdr_info->array_count == 0)
    return TRUE;

  /* Change section output offsets to be in text section order.  */
  offset = 8;
  osec = hdr_info->u.compact.entries[0]->output_section;
  for (i = 0; i < hdr_info->array_count; i++)
    {
      sec = hdr_info->u.compact.entries[i];
      if (sec->output_section != osec)
        {
          _bfd_error_handler
            (_("Invalid output section for .eh_frame_entry: %A"),
             sec->output_section);
          return FALSE;
        }
      sec->output_offset = offset;
      offset += sec->size;
    }


  /* Fix the link_order to match.  */
  for (p = sec->output_section->map_head.link_order; p != NULL; p = p->next)
    {
      if (p->type != bfd_indirect_link_order)
        abort();

      p->offset = p->u.indirect.section->output_offset;
      if (p->next != NULL)
        i--;
    }

  if (i != 0)
    {
      _bfd_error_handler
        (_("Invalid contents in %A section"), osec);
      return FALSE;
    }

  return TRUE;
}

/* The .eh_frame_hdr format for Compact EH frames:
   ubyte version                (2)
   ubyte eh_ref_enc             (DW_EH_PE_* encoding of typinfo references)
   uint32_t count               (Number of entries in table)
   [array from .eh_frame_entry sections]  */

static bfd_boolean
write_compact_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  asection *sec;
  const struct elf_backend_data *bed;
  bfd_vma count;
  bfd_byte contents[8];
  unsigned int i;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;
  sec = hdr_info->hdr_sec;

  if (sec->size != 8)
    abort();

  for (i = 0; i < sizeof (contents); i++)
    contents[i] = 0;

  contents[0] = COMPACT_EH_HDR;
  bed = get_elf_backend_data (abfd);

  BFD_ASSERT (bed->compact_eh_encoding);
  contents[1] = (*bed->compact_eh_encoding) (info);

  count = (sec->output_section->size - 8) / 8;
  bfd_put_32 (abfd, count, contents + 4);
  return bfd_set_section_contents (abfd, sec->output_section, contents,
                                   (file_ptr) sec->output_offset, sec->size);
}

/* The .eh_frame_hdr format for DWARF frames:

   ubyte version                (currently 1)
   ubyte eh_frame_ptr_enc       (DW_EH_PE_* encoding of pointer to start of
                                 .eh_frame section)
   ubyte fde_count_enc          (DW_EH_PE_* encoding of total FDE count
                                 number (or DW_EH_PE_omit if there is no
                                 binary search table computed))
   ubyte table_enc              (DW_EH_PE_* encoding of binary search table,
                                 or DW_EH_PE_omit if not present.
                                 DW_EH_PE_datarel is using address of
                                 .eh_frame_hdr section start as base)
   [encoded] eh_frame_ptr       (pointer to start of .eh_frame section)
   optionally followed by:
   [encoded] fde_count          (total number of FDEs in .eh_frame section)
   fde_count x [encoded] initial_loc, fde
                                (array of encoded pairs containing
                                 FDE initial_location field and FDE address,
                                 sorted by increasing initial_loc).  */

static bfd_boolean
write_dwarf_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  asection *sec;
  bfd_boolean retval = TRUE;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;
  sec = hdr_info->hdr_sec;
  bfd_byte *contents;
  asection *eh_frame_sec;
  bfd_size_type size;
  bfd_vma encoded_eh_frame;

  size = EH_FRAME_HDR_SIZE;
  if (hdr_info->u.dwarf.array
      && hdr_info->array_count == hdr_info->u.dwarf.fde_count)
    size += 4 + hdr_info->u.dwarf.fde_count * 8;
  contents = (bfd_byte *) bfd_malloc (size);
  if (contents == NULL)
    return FALSE;

  eh_frame_sec = bfd_get_section_by_name (abfd, ".eh_frame");
  if (eh_frame_sec == NULL)
    {
      free (contents);
      return FALSE;
    }

  memset (contents, 0, EH_FRAME_HDR_SIZE);
  /* Version.  */
  contents[0] = 1;
  /* .eh_frame offset.  */
  contents[1] = get_elf_backend_data (abfd)->elf_backend_encode_eh_address
    (abfd, info, eh_frame_sec, 0, sec, 4, &encoded_eh_frame);

  if (hdr_info->u.dwarf.array
      && hdr_info->array_count == hdr_info->u.dwarf.fde_count)
    {
      /* FDE count encoding.  */
      contents[2] = DW_EH_PE_udata4;
      /* Search table encoding.  */
      contents[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4;
    }
  else
    {
      contents[2] = DW_EH_PE_omit;
      contents[3] = DW_EH_PE_omit;
    }
  bfd_put_32 (abfd, encoded_eh_frame, contents + 4);

  if (contents[2] != DW_EH_PE_omit)
    {
      unsigned int i;
      bfd_boolean overlap, overflow;

      bfd_put_32 (abfd, hdr_info->u.dwarf.fde_count,
                  contents + EH_FRAME_HDR_SIZE);
      qsort (hdr_info->u.dwarf.array, hdr_info->u.dwarf.fde_count,
             sizeof (*hdr_info->u.dwarf.array), vma_compare);
      overlap = FALSE;
      overflow = FALSE;
      for (i = 0; i < hdr_info->u.dwarf.fde_count; i++)
        {
          bfd_vma val;

          val = hdr_info->u.dwarf.array[i].initial_loc
            - sec->output_section->vma;
          val = ((val & 0xffffffff) ^ 0x80000000) - 0x80000000;
          if (elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64
              && (hdr_info->u.dwarf.array[i].initial_loc
                  != sec->output_section->vma + val))
            overflow = TRUE;
          bfd_put_32 (abfd, val, contents + EH_FRAME_HDR_SIZE + i * 8 + 4);
          val = hdr_info->u.dwarf.array[i].fde - sec->output_section->vma;
          val = ((val & 0xffffffff) ^ 0x80000000) - 0x80000000;
          if (elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64
              && (hdr_info->u.dwarf.array[i].fde
                  != sec->output_section->vma + val))
            overflow = TRUE;
          bfd_put_32 (abfd, val, contents + EH_FRAME_HDR_SIZE + i * 8 + 8);
          if (i != 0
              && (hdr_info->u.dwarf.array[i].initial_loc
                  < (hdr_info->u.dwarf.array[i - 1].initial_loc
                     + hdr_info->u.dwarf.array[i - 1].range)))
            overlap = TRUE;
        }
      if (overflow)
        (*info->callbacks->einfo) (_("%P: .eh_frame_hdr entry overflow.\n"));
      if (overlap)
        (*info->callbacks->einfo)
          (_("%P: .eh_frame_hdr refers to overlapping FDEs.\n"));
      if (overflow || overlap)
        {
          bfd_set_error (bfd_error_bad_value);
          retval = FALSE;
        }
    }

  /* FIXME: octets_per_byte.  */
  if (!bfd_set_section_contents (abfd, sec->output_section, contents,
                                 (file_ptr) sec->output_offset,
                                 sec->size))
    retval = FALSE;
  free (contents);

  if (hdr_info->u.dwarf.array != NULL)
    free (hdr_info->u.dwarf.array);
  return retval;
}

/* Write out .eh_frame_hdr section.  This must be called after
   _bfd_elf_write_section_eh_frame has been called on all input
   .eh_frame sections.  */

bfd_boolean
_bfd_elf_write_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info)
{
  struct elf_link_hash_table *htab;
  struct eh_frame_hdr_info *hdr_info;
  asection *sec;

  htab = elf_hash_table (info);
  hdr_info = &htab->eh_info;
  sec = hdr_info->hdr_sec;

  if (info->eh_frame_hdr_type == 0 || sec == NULL)
    return TRUE;

  if (info->eh_frame_hdr_type == COMPACT_EH_HDR)
    return write_compact_eh_frame_hdr (abfd, info);
  else
    return write_dwarf_eh_frame_hdr (abfd, info);
}

/* Return the width of FDE addresses.  This is the default implementation.  */

unsigned int
_bfd_elf_eh_frame_address_size (bfd *abfd, asection *sec ATTRIBUTE_UNUSED)
{
  return elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64 ? 8 : 4;
}

/* Decide whether we can use a PC-relative encoding within the given
   EH frame section.  This is the default implementation.  */

bfd_boolean
_bfd_elf_can_make_relative (bfd *input_bfd ATTRIBUTE_UNUSED,
                            struct bfd_link_info *info ATTRIBUTE_UNUSED,
                            asection *eh_frame_section ATTRIBUTE_UNUSED)
{
  return TRUE;
}

/* Select an encoding for the given address.  Preference is given to
   PC-relative addressing modes.  */

bfd_byte
_bfd_elf_encode_eh_address (bfd *abfd ATTRIBUTE_UNUSED,
                            struct bfd_link_info *info ATTRIBUTE_UNUSED,
                            asection *osec, bfd_vma offset,
                            asection *loc_sec, bfd_vma loc_offset,
                            bfd_vma *encoded)
{
  *encoded = osec->vma + offset -
    (loc_sec->output_section->vma + loc_sec->output_offset + loc_offset);
  return DW_EH_PE_pcrel | DW_EH_PE_sdata4;
}