xref: /third_party/elfutils/libdw/dwarf_getaranges.c

/* Return list address ranges.
   Copyright (C) 2000-2010, 2016, 2017 Red Hat, Inc.
   This file is part of elfutils.
   Written by Ulrich Drepper <drepper@redhat.com>, 2000.

   This file is free software; you can redistribute it and/or modify
   it under the terms of either

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at
       your option) any later version

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at
       your option) any later version

   or both in parallel, as here.

   elfutils 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 copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <stdlib.h>
#include <assert.h>
#include "libdwP.h"
#include <dwarf.h>

struct arangelist
{
  Dwarf_Arange arange;
  struct arangelist *next;
};

/* Compare by Dwarf_Arange.addr, given pointers into an array of pointeers.  */
static int
compare_aranges (const void *a, const void *b)
{
  struct arangelist *const *p1 = a, *const *p2 = b;
  struct arangelist *l1 = *p1, *l2 = *p2;
  if (l1->arange.addr != l2->arange.addr)
    return (l1->arange.addr < l2->arange.addr) ? -1 : 1;
  return 0;
}

int
dwarf_getaranges (Dwarf *dbg, Dwarf_Aranges **aranges, size_t *naranges)
{
  if (dbg == NULL)
    return -1;

  if (dbg->aranges != NULL)
    {
      *aranges = dbg->aranges;
      if (naranges != NULL)
	*naranges = dbg->aranges->naranges;
      return 0;
    }

  if (dbg->sectiondata[IDX_debug_aranges] == NULL)
    {
      /* No such section.  */
      *aranges = NULL;
      if (naranges != NULL)
	*naranges = 0;
      return 0;
    }

  if (dbg->sectiondata[IDX_debug_aranges]->d_buf == NULL)
    return -1;

  struct arangelist *arangelist = NULL;
  unsigned int narangelist = 0;

  const unsigned char *readp = dbg->sectiondata[IDX_debug_aranges]->d_buf;
  const unsigned char *readendp
    = readp + dbg->sectiondata[IDX_debug_aranges]->d_size;

  while (readp < readendp)
    {
      const unsigned char *hdrstart = readp;

      /* Each entry starts with a header:

	 1. A 4-byte or 12-byte length containing the length of the
	 set of entries for this compilation unit, not including the
	 length field itself. [...]

	 2. A 2-byte version identifier containing the value 2 for
	 DWARF Version 2.1.

	 3. A 4-byte or 8-byte offset into the .debug_info section. [...]

	 4. A 1-byte unsigned integer containing the size in bytes of
	 an address (or the offset portion of an address for segmented
	 addressing) on the target system.

	 5. A 1-byte unsigned integer containing the size in bytes of
	 a segment descriptor on the target system.  */
      if (unlikely (readp + 4 > readendp))
	goto invalid;

      Dwarf_Word length = read_4ubyte_unaligned_inc (dbg, readp);
      unsigned int length_bytes = 4;
      if (length == DWARF3_LENGTH_64_BIT)
	{
	  if (unlikely (readp + 8 > readendp))
	    goto invalid;

	  length = read_8ubyte_unaligned_inc (dbg, readp);
	  length_bytes = 8;
	}
      else if (unlikely (length >= DWARF3_LENGTH_MIN_ESCAPE_CODE
			 && length <= DWARF3_LENGTH_MAX_ESCAPE_CODE))
	goto invalid;

      if (unlikely (readp + 2 > readendp))
	goto invalid;

      unsigned int version = read_2ubyte_unaligned_inc (dbg, readp);
      if (version != 2)
	{
	invalid:
	  __libdw_seterrno (DWARF_E_INVALID_DWARF);
	fail:
	  while (arangelist != NULL)
	    {
	      struct arangelist *next = arangelist->next;
	      free (arangelist);
	      arangelist = next;
	    }
	  return -1;
	}

      Dwarf_Word offset = 0;
      if (__libdw_read_offset_inc (dbg,
				   IDX_debug_aranges, &readp,
				   length_bytes, &offset, IDX_debug_info, 4))
	goto fail;

      /* Next up two bytes for address and segment size.  */
      if (readp + 2 > readendp)
	goto invalid;

      unsigned int address_size = *readp++;
      if (unlikely (address_size != 4 && address_size != 8))
	goto invalid;

      /* We don't actually support segment selectors.  */
      unsigned int segment_size = *readp++;
      if (segment_size != 0)
	goto invalid;

      /* Round the address to the next multiple of 2*address_size.  */
      readp += ((2 * address_size - ((readp - hdrstart) % (2 * address_size)))
		% (2 * address_size));

      while (1)
	{
	  Dwarf_Word range_address;
	  Dwarf_Word range_length;

	  if (__libdw_read_address_inc (dbg, IDX_debug_aranges, &readp,
					address_size, &range_address))
	    goto fail;

	  if (readp + address_size > readendp)
	    goto invalid;

	  if (address_size == 4)
	    range_length = read_4ubyte_unaligned_inc (dbg, readp);
	  else
	    range_length = read_8ubyte_unaligned_inc (dbg, readp);

	  /* Two zero values mark the end.  */
	  if (range_address == 0 && range_length == 0)
	    break;

	  /* We don't use alloca for these temporary structures because
	     the total number of them can be quite large.  */
	  struct arangelist *new_arange = malloc (sizeof *new_arange);
	  if (unlikely (new_arange == NULL))
	    {
	      __libdw_seterrno (DWARF_E_NOMEM);
	      goto fail;
	    }

	  new_arange->arange.addr = range_address;
	  new_arange->arange.length = range_length;

	  /* We store the actual CU DIE offset, not the CU header offset.  */
	  Dwarf_CU *cu = __libdw_findcu (dbg, offset, false);
	  if (unlikely (cu == NULL))
	    {
	      /* We haven't gotten a chance to link in the new_arange
		 into the arangelist, don't leak it.  */
	      free (new_arange);
	      goto fail;
	    }
	  new_arange->arange.offset = __libdw_first_die_off_from_cu (cu);

	  new_arange->next = arangelist;
	  arangelist = new_arange;
	  ++narangelist;

	  /* Sanity-check the data.  */
	  if (unlikely (new_arange->arange.offset
			>= dbg->sectiondata[IDX_debug_info]->d_size))
	    goto invalid;
	}
    }

  if (narangelist == 0)
    {
      assert (arangelist == NULL);
      if (naranges != NULL)
	*naranges = 0;
      *aranges = NULL;
      return 0;
    }

  /* Allocate the array for the result.  */
  void *buf = libdw_alloc (dbg, Dwarf_Aranges,
			   sizeof (Dwarf_Aranges)
			   + narangelist * sizeof (Dwarf_Arange), 1);

  /* First use the buffer for the pointers, and sort the entries.
     We'll write the pointers in the end of the buffer, and then
     copy into the buffer from the beginning so the overlap works.  */
  assert (sizeof (Dwarf_Arange) >= sizeof (Dwarf_Arange *));
  struct arangelist **sortaranges
    = (buf + sizeof (Dwarf_Aranges)
       + ((sizeof (Dwarf_Arange) - sizeof sortaranges[0]) * narangelist));

  /* The list is in LIFO order and usually they come in clumps with
     ascending addresses.  So fill from the back to probably start with
     runs already in order before we sort.  */
  unsigned int i = narangelist;
  while (i-- > 0)
    {
      sortaranges[i] = arangelist;
      arangelist = arangelist->next;
    }
  assert (arangelist == NULL);

  /* Sort by ascending address.  */
  qsort (sortaranges, narangelist, sizeof sortaranges[0], &compare_aranges);

  /* Now that they are sorted, put them in the final array.
     The buffers overlap, so we've clobbered the early elements
     of SORTARANGES by the time we're reading the later ones.  */
  *aranges = buf;
  (*aranges)->dbg = dbg;
  (*aranges)->naranges = narangelist;
  dbg->aranges = *aranges;
  if (naranges != NULL)
    *naranges = narangelist;
  for (i = 0; i < narangelist; ++i)
    {
      struct arangelist *elt = sortaranges[i];
      (*aranges)->info[i] = elt->arange;
      free (elt);
    }

  return 0;
}
INTDEF(dwarf_getaranges)