libgcc/unwind-pe.h

   1 /* Exception handling and frame unwind runtime interface routines.
   2    Copyright (C) 2001-2017 Free Software Foundation, Inc.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GCC is distributed in the hope that it will be useful, but WITHOUT
  12    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  14    License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* @@@ Really this should be out of line, but this also causes link
  26    compatibility problems with the base ABI.  This is slightly better
  27    than duplicating code, however.  */
  28
  29 #ifndef GCC_UNWIND_PE_H
  30 #define GCC_UNWIND_PE_H
  31
  32 /* If using C++, references to abort have to be qualified with std::.  */
  33 #if __cplusplus
  34 #define __gxx_abort std::abort
  35 #else
  36 #define __gxx_abort abort
  37 #endif
  38
  39 /* Pointer encodings, from dwarf2.h.  */
  40 #define DW_EH_PE_absptr         0x00
  41 #define DW_EH_PE_omit           0xff
  42
  43 #define DW_EH_PE_uleb128        0x01
  44 #define DW_EH_PE_udata2         0x02
  45 #define DW_EH_PE_udata4         0x03
  46 #define DW_EH_PE_udata8         0x04
  47 #define DW_EH_PE_sleb128        0x09
  48 #define DW_EH_PE_sdata2         0x0A
  49 #define DW_EH_PE_sdata4         0x0B
  50 #define DW_EH_PE_sdata8         0x0C
  51 #define DW_EH_PE_signed         0x08
  52
  53 #define DW_EH_PE_pcrel          0x10
  54 #define DW_EH_PE_textrel        0x20
  55 #define DW_EH_PE_datarel        0x30
  56 #define DW_EH_PE_funcrel        0x40
  57 #define DW_EH_PE_aligned        0x50
  58
  59 #define DW_EH_PE_indirect       0x80
  60 \f
  61
  62 #ifndef NO_SIZE_OF_ENCODED_VALUE
  63
  64 /* Given an encoding, return the number of bytes the format occupies.
  65    This is only defined for fixed-size encodings, and so does not
  66    include leb128.  */
  67
  68 static unsigned int
  69 size_of_encoded_value (unsigned char encoding) __attribute__ ((unused));
  70
  71 static unsigned int
  72 size_of_encoded_value (unsigned char encoding)
  73 {
  74   if (encoding == DW_EH_PE_omit)
  75     return 0;
  76
  77   switch (encoding & 0x07)
  78     {
  79     case DW_EH_PE_absptr:
  80       return sizeof (void *);
  81     case DW_EH_PE_udata2:
  82       return 2;
  83     case DW_EH_PE_udata4:
  84       return 4;
  85     case DW_EH_PE_udata8:
  86       return 8;
  87     }
  88   __gxx_abort ();
  89 }
  90
  91 #endif
  92
  93 #ifndef NO_BASE_OF_ENCODED_VALUE
  94
  95 /* Given an encoding and an _Unwind_Context, return the base to which
  96    the encoding is relative.  This base may then be passed to
  97    read_encoded_value_with_base for use when the _Unwind_Context is
  98    not available.  */
  99
 100 static _Unwind_Ptr
 101 base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
 102 {
 103   if (encoding == DW_EH_PE_omit)
 104     return 0;
 105
 106   switch (encoding & 0x70)
 107     {
 108     case DW_EH_PE_absptr:
 109     case DW_EH_PE_pcrel:
 110     case DW_EH_PE_aligned:
 111       return 0;
 112
 113     case DW_EH_PE_textrel:
 114       return _Unwind_GetTextRelBase (context);
 115     case DW_EH_PE_datarel:
 116       return _Unwind_GetDataRelBase (context);
 117     case DW_EH_PE_funcrel:
 118       return _Unwind_GetRegionStart (context);
 119     }
 120   __gxx_abort ();
 121 }
 122
 123 #endif
 124
 125 /* Read an unsigned leb128 value from P, store the value in VAL, return
 126    P incremented past the value.  We assume that a word is large enough to
 127    hold any value so encoded; if it is smaller than a pointer on some target,
 128    pointers should not be leb128 encoded on that target.  */
 129
 130 static const unsigned char *
 131 read_uleb128 (const unsigned char *p, _uleb128_t *val)
 132 {
 133   unsigned int shift = 0;
 134   unsigned char byte;
 135   _uleb128_t result;
 136
 137   result = 0;
 138   do
 139     {
 140       byte = *p++;
 141       result |= ((_uleb128_t)byte & 0x7f) << shift;
 142       shift += 7;
 143     }
 144   while (byte & 0x80);
 145
 146   *val = result;
 147   return p;
 148 }
 149
 150 /* Similar, but read a signed leb128 value.  */
 151
 152 static const unsigned char *
 153 read_sleb128 (const unsigned char *p, _sleb128_t *val)
 154 {
 155   unsigned int shift = 0;
 156   unsigned char byte;
 157   _uleb128_t result;
 158
 159   result = 0;
 160   do
 161     {
 162       byte = *p++;
 163       result |= ((_uleb128_t)byte & 0x7f) << shift;
 164       shift += 7;
 165     }
 166   while (byte & 0x80);
 167
 168   /* Sign-extend a negative value.  */
 169   if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
 170     result |= -(((_uleb128_t)1L) << shift);
 171
 172   *val = (_sleb128_t) result;
 173   return p;
 174 }
 175
 176 /* Load an encoded value from memory at P.  The value is returned in VAL;
 177    The function returns P incremented past the value.  BASE is as given
 178    by base_of_encoded_value for this encoding in the appropriate context.  */
 179
 180 static const unsigned char *
 181 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
 182                               const unsigned char *p, _Unwind_Ptr *val)
 183 {
 184   union unaligned
 185     {
 186       void *ptr;
 187       unsigned u2 __attribute__ ((mode (HI)));
 188       unsigned u4 __attribute__ ((mode (SI)));
 189       unsigned u8 __attribute__ ((mode (DI)));
 190       signed s2 __attribute__ ((mode (HI)));
 191       signed s4 __attribute__ ((mode (SI)));
 192       signed s8 __attribute__ ((mode (DI)));
 193     } __attribute__((__packed__));
 194
 195   const union unaligned *u = (const union unaligned *) p;
 196   _Unwind_Internal_Ptr result;
 197
 198   if (encoding == DW_EH_PE_aligned)
 199     {
 200       _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
 201       a = (a + sizeof (void *) - 1) & - sizeof(void *);
 202       result = *(_Unwind_Internal_Ptr *) a;
 203       p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
 204     }
 205   else
 206     {
 207       switch (encoding & 0x0f)
 208         {
 209         case DW_EH_PE_absptr:
 210           result = (_Unwind_Internal_Ptr) u->ptr;
 211           p += sizeof (void *);
 212           break;
 213
 214         case DW_EH_PE_uleb128:
 215           {
 216             _uleb128_t tmp;
 217             p = read_uleb128 (p, &tmp);
 218             result = (_Unwind_Internal_Ptr) tmp;
 219           }
 220           break;
 221
 222         case DW_EH_PE_sleb128:
 223           {
 224             _sleb128_t tmp;
 225             p = read_sleb128 (p, &tmp);
 226             result = (_Unwind_Internal_Ptr) tmp;
 227           }
 228           break;
 229
 230         case DW_EH_PE_udata2:
 231           result = u->u2;
 232           p += 2;
 233           break;
 234         case DW_EH_PE_udata4:
 235           result = u->u4;
 236           p += 4;
 237           break;
 238         case DW_EH_PE_udata8:
 239           result = u->u8;
 240           p += 8;
 241           break;
 242
 243         case DW_EH_PE_sdata2:
 244           result = u->s2;
 245           p += 2;
 246           break;
 247         case DW_EH_PE_sdata4:
 248           result = u->s4;
 249           p += 4;
 250           break;
 251         case DW_EH_PE_sdata8:
 252           result = u->s8;
 253           p += 8;
 254           break;
 255
 256         default:
 257           __gxx_abort ();
 258         }
 259
 260       if (result != 0)
 261         {
 262           result += ((encoding & 0x70) == DW_EH_PE_pcrel
 263                      ? (_Unwind_Internal_Ptr) u : base);
 264           if (encoding & DW_EH_PE_indirect)
 265             result = *(_Unwind_Internal_Ptr *) result;
 266         }
 267     }
 268
 269   *val = result;
 270   return p;
 271 }
 272
 273 #ifndef NO_BASE_OF_ENCODED_VALUE
 274
 275 /* Like read_encoded_value_with_base, but get the base from the context
 276    rather than providing it directly.  */
 277
 278 static inline const unsigned char *
 279 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
 280                     const unsigned char *p, _Unwind_Ptr *val)
 281 {
 282   return read_encoded_value_with_base (encoding,
 283                 base_of_encoded_value (encoding, context),
 284                 p, val);
 285 }
 286
 287 #endif
 288
 289 #endif /* unwind-pe.h */