xref: /freebsd-10.1-release/contrib/gcc/unwind-pe.h

/* Exception handling and frame unwind runtime interface routines.
   Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.

   This file is part of GCC.

   GCC 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 2, or (at your option)
   any later version.

   In addition to the permissions in the GNU General Public License, the
   Free Software Foundation gives you unlimited permission to link the
   compiled version of this file into combinations with other programs,
   and to distribute those combinations without any restriction coming
   from the use of this file.  (The General Public License restrictions
   do apply in other respects; for example, they cover modification of
   the file, and distribution when not linked into a combined
   executable.)

   GCC 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 GCC; see the file COPYING.  If not, write to the Free
   Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301, USA.  */

/* @@@ Really this should be out of line, but this also causes link
   compatibility problems with the base ABI.  This is slightly better
   than duplicating code, however.  */

#ifndef GCC_UNWIND_PE_H
#define GCC_UNWIND_PE_H

/* If using C++, references to abort have to be qualified with std::.  */
#if __cplusplus
#define __gxx_abort std::abort
#else
#define __gxx_abort abort
#endif

/* Pointer encodings, from dwarf2.h.  */
#define DW_EH_PE_absptr         0x00
#define DW_EH_PE_omit           0xff

#define DW_EH_PE_uleb128        0x01
#define DW_EH_PE_udata2         0x02
#define DW_EH_PE_udata4         0x03
#define DW_EH_PE_udata8         0x04
#define DW_EH_PE_sleb128        0x09
#define DW_EH_PE_sdata2         0x0A
#define DW_EH_PE_sdata4         0x0B
#define DW_EH_PE_sdata8         0x0C
#define DW_EH_PE_signed         0x08

#define DW_EH_PE_pcrel          0x10
#define DW_EH_PE_textrel        0x20
#define DW_EH_PE_datarel        0x30
#define DW_EH_PE_funcrel        0x40
#define DW_EH_PE_aligned        0x50

#define DW_EH_PE_indirect	0x80


#ifndef NO_SIZE_OF_ENCODED_VALUE

/* Given an encoding, return the number of bytes the format occupies.
   This is only defined for fixed-size encodings, and so does not
   include leb128.  */

static unsigned int
size_of_encoded_value (unsigned char encoding)
{
  if (encoding == DW_EH_PE_omit)
    return 0;

  switch (encoding & 0x07)
    {
    case DW_EH_PE_absptr:
      return sizeof (void *);
    case DW_EH_PE_udata2:
      return 2;
    case DW_EH_PE_udata4:
      return 4;
    case DW_EH_PE_udata8:
      return 8;
    }
  __gxx_abort ();
}

#endif

#ifndef NO_BASE_OF_ENCODED_VALUE

/* Given an encoding and an _Unwind_Context, return the base to which
   the encoding is relative.  This base may then be passed to
   read_encoded_value_with_base for use when the _Unwind_Context is
   not available.  */

static _Unwind_Ptr
base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
{
  if (encoding == DW_EH_PE_omit)
    return 0;

  switch (encoding & 0x70)
    {
    case DW_EH_PE_absptr:
    case DW_EH_PE_pcrel:
    case DW_EH_PE_aligned:
      return 0;

    case DW_EH_PE_textrel:
      return _Unwind_GetTextRelBase (context);
    case DW_EH_PE_datarel:
      return _Unwind_GetDataRelBase (context);
    case DW_EH_PE_funcrel:
      return _Unwind_GetRegionStart (context);
    }
  __gxx_abort ();
}

#endif

/* Read an unsigned leb128 value from P, store the value in VAL, return
   P incremented past the value.  We assume that a word is large enough to
   hold any value so encoded; if it is smaller than a pointer on some target,
   pointers should not be leb128 encoded on that target.  */

static const unsigned char *
read_uleb128 (const unsigned char *p, _Unwind_Word *val)
{
  unsigned int shift = 0;
  unsigned char byte;
  _Unwind_Word result;

  result = 0;
  do
    {
      byte = *p++;
      result |= ((_Unwind_Word)byte & 0x7f) << shift;
      shift += 7;
    }
  while (byte & 0x80);

  *val = result;
  return p;
}

/* Similar, but read a signed leb128 value.  */

static const unsigned char *
read_sleb128 (const unsigned char *p, _Unwind_Sword *val)
{
  unsigned int shift = 0;
  unsigned char byte;
  _Unwind_Word result;

  result = 0;
  do
    {
      byte = *p++;
      result |= ((_Unwind_Word)byte & 0x7f) << shift;
      shift += 7;
    }
  while (byte & 0x80);

  /* Sign-extend a negative value.  */
  if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
    result |= -(((_Unwind_Word)1L) << shift);

  *val = (_Unwind_Sword) result;
  return p;
}

/* Load an encoded value from memory at P.  The value is returned in VAL;
   The function returns P incremented past the value.  BASE is as given
   by base_of_encoded_value for this encoding in the appropriate context.  */

static const unsigned char *
read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
			      const unsigned char *p, _Unwind_Ptr *val)
{
  union unaligned
    {
      void *ptr;
      unsigned u2 __attribute__ ((mode (HI)));
      unsigned u4 __attribute__ ((mode (SI)));
      unsigned u8 __attribute__ ((mode (DI)));
      signed s2 __attribute__ ((mode (HI)));
      signed s4 __attribute__ ((mode (SI)));
      signed s8 __attribute__ ((mode (DI)));
    } __attribute__((__packed__));

  const union unaligned *u = (const union unaligned *) p;
  _Unwind_Internal_Ptr result;

  if (encoding == DW_EH_PE_aligned)
    {
      _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
      a = (a + sizeof (void *) - 1) & - sizeof(void *);
      result = *(_Unwind_Internal_Ptr *) a;
      p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
    }
  else
    {
      switch (encoding & 0x0f)
	{
	case DW_EH_PE_absptr:
	  result = (_Unwind_Internal_Ptr) u->ptr;
	  p += sizeof (void *);
	  break;

	case DW_EH_PE_uleb128:
	  {
	    _Unwind_Word tmp;
	    p = read_uleb128 (p, &tmp);
	    result = (_Unwind_Internal_Ptr) tmp;
	  }
	  break;

	case DW_EH_PE_sleb128:
	  {
	    _Unwind_Sword tmp;
	    p = read_sleb128 (p, &tmp);
	    result = (_Unwind_Internal_Ptr) tmp;
	  }
	  break;

	case DW_EH_PE_udata2:
	  result = u->u2;
	  p += 2;
	  break;
	case DW_EH_PE_udata4:
	  result = u->u4;
	  p += 4;
	  break;
	case DW_EH_PE_udata8:
	  result = u->u8;
	  p += 8;
	  break;

	case DW_EH_PE_sdata2:
	  result = u->s2;
	  p += 2;
	  break;
	case DW_EH_PE_sdata4:
	  result = u->s4;
	  p += 4;
	  break;
	case DW_EH_PE_sdata8:
	  result = u->s8;
	  p += 8;
	  break;

	default:
	  __gxx_abort ();
	}

      if (result != 0)
	{
	  result += ((encoding & 0x70) == DW_EH_PE_pcrel
		     ? (_Unwind_Internal_Ptr) u : base);
	  if (encoding & DW_EH_PE_indirect)
	    result = *(_Unwind_Internal_Ptr *) result;
	}
    }

  *val = result;
  return p;
}

#ifndef NO_BASE_OF_ENCODED_VALUE

/* Like read_encoded_value_with_base, but get the base from the context
   rather than providing it directly.  */

static inline const unsigned char *
read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
		    const unsigned char *p, _Unwind_Ptr *val)
{
  return read_encoded_value_with_base (encoding,
		base_of_encoded_value (encoding, context),
		p, val);
}

#endif

#endif /* unwind-pe.h */