src/libdw/encoded-value.h

/* DW_EH_PE_* support for libdw unwinder.
   Copyright (C) 2009-2010 Red Hat, Inc.
   This file is part of Red Hat elfutils.

   Red Hat elfutils 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; version 2 of the License.

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   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 Red Hat elfutils; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.

   In addition, as a special exception, Red Hat, Inc. gives You the
   additional right to link the code of Red Hat elfutils with code licensed
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   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
   license is granted, either expressly or impliedly, by designation as an
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#ifndef _ENCODED_VALUE_H
#define _ENCODED_VALUE_H 1

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


static size_t __attribute__ ((unused))
encoded_value_size (const Elf_Data *data, const unsigned char e_ident[],
		    uint8_t encoding, const uint8_t *p)
{
  if (encoding == DW_EH_PE_omit)
    return 0;

  switch (encoding & 0x07)
    {
    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 e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;

    case DW_EH_PE_uleb128:
      if (p != NULL)
	{
	  const uint8_t *end = p;
	  while (end < (uint8_t *) data->d_buf + data->d_size)
	    if (*end++ & 0x80u)
	      return end - p;
	}

    default:
      abort ();
      return 0;
    }
}

static inline int __attribute__ ((unused))
__libdw_cfi_read_address_inc (const Dwarf_CFI *cache,
			      const unsigned char **addrp,
			      int width, Dwarf_Addr *ret)
{
  width = width ?: cache->e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;

  if (cache->dbg != NULL)
    return __libdw_read_address_inc (cache->dbg, IDX_debug_frame,
				     addrp, width, ret);

  /* Only .debug_frame might have relocation to consider.
     Read plain values from .eh_frame data.  */

  if (width == 4)
    *ret = read_4ubyte_unaligned_inc (cache, *addrp);
  else
    *ret = read_8ubyte_unaligned_inc (cache, *addrp);
  return 0;
}

static bool __attribute__ ((unused))
read_encoded_value (const Dwarf_CFI *cache, uint8_t encoding, const uint8_t **p,
		    Dwarf_Addr *result)
{
  *result = 0;
  switch (encoding & 0x70)
    {
    case DW_EH_PE_absptr:
      break;
    case DW_EH_PE_pcrel:
      *result = (cache->frame_vaddr
		 + (*p - (const uint8_t *) cache->data->d.d_buf));
      break;
    case DW_EH_PE_textrel:
      // ia64: segrel
      *result = cache->textrel;
      break;
    case DW_EH_PE_datarel:
      // i386: GOTOFF
      // ia64: gprel
      *result = cache->datarel;
      break;
    case DW_EH_PE_funcrel:	/* XXX */
      break;
    case DW_EH_PE_aligned:
      {
	const size_t size = encoded_value_size (&cache->data->d, cache->e_ident,
						encoding, *p);
	size_t align = ((cache->frame_vaddr
			 + (*p - (const uint8_t *) cache->data->d.d_buf))
			& (size - 1));
	if (align != 0)
	  *p += size - align;
	break;
      }

    default:
      abort ();
    }

  Dwarf_Addr value;
  switch (encoding & 0x0f)
    {
    case DW_EH_PE_udata2:
      value = read_2ubyte_unaligned_inc (cache, *p);
      break;

    case DW_EH_PE_sdata2:
      value = read_2sbyte_unaligned_inc (cache, *p);
      break;

    case DW_EH_PE_udata4:
      if (__libdw_cfi_read_address_inc (cache, p, 4, &value))
	return true;
      break;

    case DW_EH_PE_sdata4:
      if (__libdw_cfi_read_address_inc (cache, p, 4, &value))
	return true;
      value = (Dwarf_Sword) (Elf32_Sword) value; /* Sign-extend.  */
      break;

    case DW_EH_PE_udata8:
    case DW_EH_PE_sdata8:
      if (__libdw_cfi_read_address_inc (cache, p, 8, &value))
	return true;
      break;

    case DW_EH_PE_absptr:
      if (__libdw_cfi_read_address_inc (cache, p, 0, &value))
	return true;
      break;

    case DW_EH_PE_uleb128:
      get_uleb128 (value, *p);
      break;

    case DW_EH_PE_sleb128:
      get_sleb128 (value, *p);
      break;

    default:
      abort ();
    }

  *result += value;

  if (encoding & DW_EH_PE_indirect)
    {
      if (unlikely (*result < cache->frame_vaddr))
	return true;
      *result -= cache->frame_vaddr;
      if (unlikely (*result > (cache->data->d.d_size
			       - encoded_value_size (NULL, cache->e_ident,
						     DW_EH_PE_absptr, NULL))))
	return true;
      const uint8_t *ptr = cache->data->d.d_buf + *result;
      return __libdw_cfi_read_address_inc (cache, &ptr, 0, result);
    }

  return false;
}

#endif	/* encoded-value.h */