gcc/unwind-pe.h

   1 /* Exception handling and frame unwind runtime interface routines.
   2    Copyright (C) 2001 Free Software Foundation, Inc.
   3
   4    This file is part of GNU CC.
   5
   6    GNU CC is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    GNU CC is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GNU CC; see the file COPYING.  If not, write to
  18    the Free Software Foundation, 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 /* @@@ Really this should be out of line, but this also causes link
  22    compatibility problems with the base ABI.  This is slightly better
  23    than duplicating code, however.  */
  24
  25 /* If using C++, references to abort have to be qualified with std::. */
  26 #if __cplusplus
  27 #define __gxx_abort std::abort
  28 #else
  29 #define __gxx_abort abort
  30 #endif
  31
  32 /* Pointer encodings, from dwarf2.h.  */
  33 #define DW_EH_PE_absptr         0x00
  34 #define DW_EH_PE_omit           0xff
  35
  36 #define DW_EH_PE_uleb128        0x01
  37 #define DW_EH_PE_udata2         0x02
  38 #define DW_EH_PE_udata4         0x03
  39 #define DW_EH_PE_udata8         0x04
  40 #define DW_EH_PE_sleb128        0x09
  41 #define DW_EH_PE_sdata2         0x0A
  42 #define DW_EH_PE_sdata4         0x0B
  43 #define DW_EH_PE_sdata8         0x0C
  44 #define DW_EH_PE_signed         0x08
  45
  46 #define DW_EH_PE_pcrel          0x10
  47 #define DW_EH_PE_textrel        0x20
  48 #define DW_EH_PE_datarel        0x30
  49 #define DW_EH_PE_funcrel        0x40
  50 #define DW_EH_PE_aligned        0x50
  51
  52 #define DW_EH_PE_indirect       0x80
  53 \f
  54
  55 /* Given an encoding, return the number of bytes the format occupies.
  56    This is only defined for fixed-size encodings, and so does not
  57    include leb128.  */
  58
  59 static unsigned int
  60 size_of_encoded_value (unsigned char encoding)
  61 {
  62   if (encoding == DW_EH_PE_omit)
  63     return 0;
  64
  65   switch (encoding & 0x07)
  66     {
  67     case DW_EH_PE_absptr:
  68       return sizeof (void *);
  69     case DW_EH_PE_udata2:
  70       return 2;
  71     case DW_EH_PE_udata4:
  72       return 4;
  73     case DW_EH_PE_udata8:
  74       return 8;
  75     }
  76   __gxx_abort ();
  77 }
  78
  79 #ifndef NO_BASE_OF_ENCODED_VALUE
  80
  81 /* Given an encoding and an _Unwind_Context, return the base to which
  82    the encoding is relative.  This base may then be passed to
  83    read_encoded_value_with_base for use when the _Unwind_Context is
  84    not available.  */
  85
  86 static _Unwind_Ptr
  87 base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
  88 {
  89   if (encoding == DW_EH_PE_omit)
  90     return 0;
  91
  92   switch (encoding & 0x70)
  93     {
  94     case DW_EH_PE_absptr:
  95     case DW_EH_PE_pcrel:
  96     case DW_EH_PE_aligned:
  97       return 0;
  98
  99     case DW_EH_PE_textrel:
 100       return _Unwind_GetTextRelBase (context);
 101     case DW_EH_PE_datarel:
 102       return _Unwind_GetDataRelBase (context);
 103     case DW_EH_PE_funcrel:
 104       return _Unwind_GetRegionStart (context);
 105     }
 106   __gxx_abort ();
 107 }
 108
 109 #endif
 110
 111 /* Load an encoded value from memory at P.  The value is returned in VAL;
 112    The function returns P incremented past the value.  BASE is as given
 113    by base_of_encoded_value for this encoding in the appropriate context.  */
 114
 115 static const unsigned char *
 116 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
 117                               const unsigned char *p, _Unwind_Ptr *val)
 118 {
 119   union unaligned
 120     {
 121       void *ptr;
 122       unsigned u2 __attribute__ ((mode (HI)));
 123       unsigned u4 __attribute__ ((mode (SI)));
 124       unsigned u8 __attribute__ ((mode (DI)));
 125       signed s2 __attribute__ ((mode (HI)));
 126       signed s4 __attribute__ ((mode (SI)));
 127       signed s8 __attribute__ ((mode (DI)));
 128     } __attribute__((__packed__));
 129
 130   union unaligned *u = (union unaligned *) p;
 131   _Unwind_Ptr result;
 132
 133   if (encoding == DW_EH_PE_aligned)
 134     {
 135       _Unwind_Ptr a = (_Unwind_Ptr)p;
 136       a = (a + sizeof (void *) - 1) & - sizeof(void *);
 137       result = *(_Unwind_Ptr *) a;
 138       p = (const unsigned char *)(a + sizeof (void *));
 139     }
 140   else
 141     {
 142       switch (encoding & 0x0f)
 143         {
 144         case DW_EH_PE_absptr:
 145           result = (_Unwind_Ptr) u->ptr;
 146           p += sizeof (void *);
 147           break;
 148
 149         case DW_EH_PE_uleb128:
 150           {
 151             unsigned int shift = 0;
 152             unsigned char byte;
 153
 154             result = 0;
 155             do
 156               {
 157                 byte = *p++;
 158                 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
 159                 shift += 7;
 160               }
 161             while (byte & 0x80);
 162           }
 163           break;
 164
 165         case DW_EH_PE_sleb128:
 166           {
 167             unsigned int shift = 0;
 168             unsigned char byte;
 169
 170             result = 0;
 171             do
 172               {
 173                 byte = *p++;
 174                 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
 175                 shift += 7;
 176               }
 177             while (byte & 0x80);
 178
 179             if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
 180               result |= -(1L << shift);
 181           }
 182           break;
 183
 184         case DW_EH_PE_udata2:
 185           result = u->u2;
 186           p += 2;
 187           break;
 188         case DW_EH_PE_udata4:
 189           result = u->u4;
 190           p += 4;
 191           break;
 192         case DW_EH_PE_udata8:
 193           result = u->u8;
 194           p += 8;
 195           break;
 196
 197         case DW_EH_PE_sdata2:
 198           result = u->s2;
 199           p += 2;
 200           break;
 201         case DW_EH_PE_sdata4:
 202           result = u->s4;
 203           p += 4;
 204           break;
 205         case DW_EH_PE_sdata8:
 206           result = u->s8;
 207           p += 8;
 208           break;
 209
 210         default:
 211           __gxx_abort ();
 212         }
 213
 214       if (result != 0)
 215         {
 216           result += ((encoding & 0x70) == DW_EH_PE_pcrel
 217                      ? (_Unwind_Ptr)u : base);
 218           if (encoding & DW_EH_PE_indirect)
 219             result = *(_Unwind_Ptr *)result;
 220         }
 221     }
 222
 223   *val = result;
 224   return p;
 225 }
 226
 227 #ifndef NO_BASE_OF_ENCODED_VALUE
 228
 229 /* Like read_encoded_value_with_base, but get the base from the context
 230    rather than providing it directly.  */
 231
 232 static inline const unsigned char *
 233 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
 234                     const unsigned char *p, _Unwind_Ptr *val)
 235 {
 236   return read_encoded_value_with_base (encoding,
 237                 base_of_encoded_value (encoding, context),
 238                 p, val);
 239 }
 240
 241 #endif
 242
 243 /* Read an unsigned leb128 value from P, store the value in VAL, return
 244    P incremented past the value.  */
 245
 246 static inline const unsigned char *
 247 read_uleb128 (const unsigned char *p, _Unwind_Ptr *val)
 248 {
 249   return read_encoded_value_with_base (DW_EH_PE_uleb128, 0, p, val);
 250 }
 251
 252 /* Similar, but read a signed leb128 value.  */
 253
 254 static inline const unsigned char *
 255 read_sleb128 (const unsigned char *p, _Unwind_Ptr *val)
 256 {
 257   return read_encoded_value_with_base (DW_EH_PE_sleb128, 0, p, val);
 258 }