xref: /external/libunwind/src/dwarf/Gfde.c

/* libunwind - a platform-independent unwind library
   Copyright (c) 2003-2005 Hewlett-Packard Development Company, L.P.
	Contributed by David Mosberger-Tang <davidm@hpl.hp.com>

This file is part of libunwind.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */

#include "dwarf_i.h"

static inline int
is_cie_id (unw_word_t val, int is_debug_frame)
{
  /* The CIE ID is normally 0xffffffff (for 32-bit ELF) or
     0xffffffffffffffff (for 64-bit ELF).  However, .eh_frame
     uses 0.  */
  if (is_debug_frame)
    /* ANDROID support update. */
    return (val == (uint32_t) -1 || val == (unw_word_t) (uint64_t) -1);
    /* End of ANDROID update. */
  else
    return (val == 0);
}

/* Note: we don't need to keep track of more than the first four
   characters of the augmentation string, because we (a) ignore any
   augmentation string contents once we find an unrecognized character
   and (b) those characters that we do recognize, can't be
   repeated.  */
static inline int
parse_cie (unw_addr_space_t as, unw_accessors_t *a, unw_word_t addr,
	   const unw_proc_info_t *pi, struct dwarf_cie_info *dci,
	   unw_word_t base, void *arg)
{
  uint8_t version, ch, augstr[5], fde_encoding, handler_encoding;
  unw_word_t len, cie_end_addr, aug_size;
  uint32_t u32val;
  uint64_t u64val;
  size_t i;
  int ret;
# define STR2(x)	#x
# define STR(x)		STR2(x)

  /* Pick appropriate default for FDE-encoding.  DWARF spec says
     start-IP (initial_location) and the code-size (address_range) are
     "address-unit sized constants".  The `R' augmentation can be used
     to override this, but by default, we pick an address-sized unit
     for fde_encoding.  */
  switch (dwarf_addr_size (as))
    {
    case 4:	fde_encoding = DW_EH_PE_udata4; break;
    case 8:	fde_encoding = DW_EH_PE_udata8; break;
    default:	fde_encoding = DW_EH_PE_omit; break;
    }

  dci->lsda_encoding = DW_EH_PE_omit;
  dci->handler = 0;

  if ((ret = dwarf_readu32 (as, a, &addr, &u32val, arg)) < 0)
    return ret;

  if (u32val != 0xffffffff)
    {
      /* the CIE is in the 32-bit DWARF format */
      uint32_t cie_id;
      /* DWARF says CIE id should be 0xffffffff, but in .eh_frame, it's 0 */
      const uint32_t expected_id = (base) ? 0xffffffff : 0;

      len = u32val;
      cie_end_addr = addr + len;
      if ((ret = dwarf_readu32 (as, a, &addr, &cie_id, arg)) < 0)
	return ret;
      if (cie_id != expected_id)
	{
	  Debug (1, "Unexpected CIE id %x\n", cie_id);
	  return -UNW_EINVAL;
	}
    }
  else
    {
      /* the CIE is in the 64-bit DWARF format */
      uint64_t cie_id;
      /* DWARF says CIE id should be 0xffffffffffffffff, but in
	 .eh_frame, it's 0 */
      const uint64_t expected_id = (base) ? 0xffffffffffffffffull : 0;

      if ((ret = dwarf_readu64 (as, a, &addr, &u64val, arg)) < 0)
	return ret;
      len = u64val;
      cie_end_addr = addr + len;
      if ((ret = dwarf_readu64 (as, a, &addr, &cie_id, arg)) < 0)
	return ret;
      if (cie_id != expected_id)
	{
	  Debug (1, "Unexpected CIE id %llx\n", (long long) cie_id);
	  return -UNW_EINVAL;
	}
    }
  dci->cie_instr_end = cie_end_addr;

  if ((ret = dwarf_readu8 (as, a, &addr, &version, arg)) < 0)
    return ret;

  if (version != 1 && version != 3 && version != 4)
    {
      Debug (1, "Got CIE version %u, expected version 1, 3 or 4\n", version);
      return -UNW_EBADVERSION;
    }

  /* read and parse the augmentation string: */
  memset (augstr, 0, sizeof (augstr));
  for (i = 0;;)
    {
      if ((ret = dwarf_readu8 (as, a, &addr, &ch, arg)) < 0)
	return ret;

      if (!ch)
	break;	/* end of augmentation string */

      if (i < sizeof (augstr) - 1)
	augstr[i++] = ch;
    }

  if (version == 4) {
    uint8_t address_size;
    if ((ret = dwarf_readu8(as, a, &addr, &address_size, arg)) < 0) {
      return ret;
    }
    if (address_size != sizeof(unw_word_t)) {
      return -UNW_EBADVERSION;
    }
    uint8_t segment_size;
    if ((ret = dwarf_readu8(as, a, &addr, &segment_size, arg)) < 0) {
      return ret;
    }
    // We don't support non-zero segment size.
    if (segment_size != 0) {
      return -UNW_EBADVERSION;
    }
  }
  if ((ret = dwarf_read_uleb128 (as, a, &addr, &dci->code_align, arg)) < 0
      || (ret = dwarf_read_sleb128 (as, a, &addr, &dci->data_align, arg)) < 0)
    return ret;

  /* Read the return-address column either as a u8 or as a uleb128.  */
  if (version == 1)
    {
      if ((ret = dwarf_readu8 (as, a, &addr, &ch, arg)) < 0)
	return ret;
      dci->ret_addr_column = ch;
    }
  else if ((ret = dwarf_read_uleb128 (as, a, &addr, &dci->ret_addr_column,
				      arg)) < 0)
    return ret;

  i = 0;
  if (augstr[0] == 'z')
    {
      dci->sized_augmentation = 1;
      if ((ret = dwarf_read_uleb128 (as, a, &addr, &aug_size, arg)) < 0)
	return ret;
      i++;
    }

  for (; i < sizeof (augstr) && augstr[i]; ++i)
    switch (augstr[i])
      {
      case 'L':
	/* read the LSDA pointer-encoding format.  */
	if ((ret = dwarf_readu8 (as, a, &addr, &ch, arg)) < 0)
	  return ret;
	dci->lsda_encoding = ch;
	break;

      case 'R':
	/* read the FDE pointer-encoding format.  */
	if ((ret = dwarf_readu8 (as, a, &addr, &fde_encoding, arg)) < 0)
	  return ret;
	break;

      case 'P':
	/* read the personality-routine pointer-encoding format.  */
	if ((ret = dwarf_readu8 (as, a, &addr, &handler_encoding, arg)) < 0)
	  return ret;
	if ((ret = dwarf_read_encoded_pointer (as, a, &addr, handler_encoding,
					       pi, &dci->handler, arg)) < 0)
	  return ret;
	break;

      case 'S':
	/* This is a signal frame. */
	dci->signal_frame = 1;

	/* Temporarily set it to one so dwarf_parse_fde() knows that
	   it should fetch the actual ABI/TAG pair from the FDE.  */
	dci->have_abi_marker = 1;
	break;

      default:
	Debug (1, "Unexpected augmentation string `%s'\n", augstr);
	if (dci->sized_augmentation)
	  /* If we have the size of the augmentation body, we can skip
	     over the parts that we don't understand, so we're OK. */
	  goto done;
	else
	  return -UNW_EINVAL;
      }
 done:
  dci->fde_encoding = fde_encoding;
  dci->cie_instr_start = addr;
  Debug (15, "CIE parsed OK, augmentation = \"%s\", handler=0x%lx\n",
	 augstr, (long) dci->handler);
  return 0;
}

/* Extract proc-info from the FDE starting at adress ADDR.

   Pass BASE as zero for eh_frame behaviour, or a pointer to
   debug_frame base for debug_frame behaviour.  */

HIDDEN int
dwarf_extract_proc_info_from_fde (unw_addr_space_t as, unw_accessors_t *a,
				  unw_word_t *addrp, unw_proc_info_t *pi,
				  int need_unwind_info, unw_word_t base,
				  void *arg)
{
  unw_word_t fde_end_addr, cie_addr, cie_offset_addr, aug_end_addr = 0;
  unw_word_t start_ip, ip_range, aug_size, addr = *addrp;
  int ret, ip_range_encoding;
  struct dwarf_cie_info dci;
  uint64_t u64val;
  uint32_t u32val;

  Debug (12, "FDE @ 0x%lx\n", (long) addr);

  memset (&dci, 0, sizeof (dci));

  if ((ret = dwarf_readu32 (as, a, &addr, &u32val, arg)) < 0)
    return ret;

  if (u32val != 0xffffffff)
    {
      int32_t cie_offset;

      /* In some configurations, an FDE with a 0 length indicates the
	 end of the FDE-table.  */
      if (u32val == 0)
	return -UNW_ENOINFO;

      /* the FDE is in the 32-bit DWARF format */

      *addrp = fde_end_addr = addr + u32val;
      cie_offset_addr = addr;

      if ((ret = dwarf_reads32 (as, a, &addr, &cie_offset, arg)) < 0)
	return ret;

      if (is_cie_id (cie_offset, base != 0))
	/* ignore CIEs (happens during linear searches) */
	return 0;

      if (base != 0)
        cie_addr = base + cie_offset;
      else
	/* DWARF says that the CIE_pointer in the FDE is a
	   .debug_frame-relative offset, but the GCC-generated .eh_frame
	   sections instead store a "pcrelative" offset, which is just
	   as fine as it's self-contained.  */
	cie_addr = cie_offset_addr - cie_offset;
    }
  else
    {
      int64_t cie_offset;

      /* the FDE is in the 64-bit DWARF format */

      if ((ret = dwarf_readu64 (as, a, &addr, &u64val, arg)) < 0)
	return ret;

      *addrp = fde_end_addr = addr + u64val;
      cie_offset_addr = addr;

      if ((ret = dwarf_reads64 (as, a, &addr, &cie_offset, arg)) < 0)
	return ret;

      if (is_cie_id (cie_offset, base != 0))
	/* ignore CIEs (happens during linear searches) */
	return 0;

      if (base != 0)
	cie_addr = base + cie_offset;
      else
	/* DWARF says that the CIE_pointer in the FDE is a
	   .debug_frame-relative offset, but the GCC-generated .eh_frame
	   sections instead store a "pcrelative" offset, which is just
	   as fine as it's self-contained.  */
	cie_addr = (unw_word_t) ((uint64_t) cie_offset_addr - cie_offset);
    }

  Debug (15, "looking for CIE at address %lx\n", (long) cie_addr);

  if ((ret = parse_cie (as, a, cie_addr, pi, &dci, base, arg)) < 0)
    return ret;

  /* IP-range has same encoding as FDE pointers, except that it's
     always an absolute value: */
  ip_range_encoding = dci.fde_encoding & DW_EH_PE_FORMAT_MASK;

  if ((ret = dwarf_read_encoded_pointer (as, a, &addr, dci.fde_encoding,
					 pi, &start_ip, arg)) < 0
      || (ret = dwarf_read_encoded_pointer (as, a, &addr, ip_range_encoding,
					    pi, &ip_range, arg)) < 0)
    return ret;
  pi->start_ip = start_ip;
  pi->end_ip = start_ip + ip_range;
  pi->handler = dci.handler;

  if (dci.sized_augmentation)
    {
      if ((ret = dwarf_read_uleb128 (as, a, &addr, &aug_size, arg)) < 0)
	return ret;
      aug_end_addr = addr + aug_size;
    }

  if ((ret = dwarf_read_encoded_pointer (as, a, &addr, dci.lsda_encoding,
					 pi, &pi->lsda, arg)) < 0)
    return ret;

  Debug (15, "FDE covers IP 0x%lx-0x%lx, LSDA=0x%lx\n",
	 (long) pi->start_ip, (long) pi->end_ip, (long) pi->lsda);

  if (need_unwind_info)
    {
      pi->format = UNW_INFO_FORMAT_TABLE;
      pi->unwind_info_size = sizeof (dci);
      pi->unwind_info = mempool_alloc (&dwarf_cie_info_pool);
      if (!pi->unwind_info)
	return -UNW_ENOMEM;

      if (dci.have_abi_marker)
	{
	  if ((ret = dwarf_readu16 (as, a, &addr, &dci.abi, arg)) < 0
	      || (ret = dwarf_readu16 (as, a, &addr, &dci.tag, arg)) < 0)
	    return ret;
	  Debug (13, "Found ABI marker = (abi=%u, tag=%u)\n",
		 dci.abi, dci.tag);
	}

      if (dci.sized_augmentation)
	dci.fde_instr_start = aug_end_addr;
      else
	dci.fde_instr_start = addr;
      dci.fde_instr_end = fde_end_addr;

      memcpy (pi->unwind_info, &dci, sizeof (dci));
    }
  return 0;
}