libgcc/unwind-pe.h

   1 /* Exception handling and frame unwind runtime interface routines.
   2    Copyright (C) 2001-2020 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 #pragma GCC diagnostic push
 181 #pragma GCC diagnostic ignored "-Waddress-of-packed-member"
 182
 183 static const unsigned char *
 184 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
 185                               const unsigned char *p, _Unwind_Ptr *val)
 186 {
 187   union unaligned
 188     {
 189       void *ptr;
 190       unsigned u2 __attribute__ ((mode (HI)));
 191       unsigned u4 __attribute__ ((mode (SI)));
 192       unsigned u8 __attribute__ ((mode (DI)));
 193       signed s2 __attribute__ ((mode (HI)));
 194       signed s4 __attribute__ ((mode (SI)));
 195       signed s8 __attribute__ ((mode (DI)));
 196     } __attribute__((__packed__));
 197
 198   const union unaligned *u = (const union unaligned *) p;
 199   _Unwind_Internal_Ptr result;
 200
 201   if (encoding == DW_EH_PE_aligned)
 202     {
 203       _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
 204       a = (a + sizeof (void *) - 1) & - sizeof(void *);
 205       result = *(_Unwind_Internal_Ptr *) a;
 206       p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
 207     }
 208   else
 209     {
 210       switch (encoding & 0x0f)
 211         {
 212         case DW_EH_PE_absptr:
 213           result = (_Unwind_Internal_Ptr) u->ptr;
 214           p += sizeof (void *);
 215           break;
 216
 217         case DW_EH_PE_uleb128:
 218           {
 219             _uleb128_t tmp;
 220             p = read_uleb128 (p, &tmp);
 221             result = (_Unwind_Internal_Ptr) tmp;
 222           }
 223           break;
 224
 225         case DW_EH_PE_sleb128:
 226           {
 227             _sleb128_t tmp;
 228             p = read_sleb128 (p, &tmp);
 229             result = (_Unwind_Internal_Ptr) tmp;
 230           }
 231           break;
 232
 233         case DW_EH_PE_udata2:
 234           result = u->u2;
 235           p += 2;
 236           break;
 237         case DW_EH_PE_udata4:
 238           result = u->u4;
 239           p += 4;
 240           break;
 241         case DW_EH_PE_udata8:
 242           result = u->u8;
 243           p += 8;
 244           break;
 245
 246         case DW_EH_PE_sdata2:
 247           result = u->s2;
 248           p += 2;
 249           break;
 250         case DW_EH_PE_sdata4:
 251           result = u->s4;
 252           p += 4;
 253           break;
 254         case DW_EH_PE_sdata8:
 255           result = u->s8;
 256           p += 8;
 257           break;
 258
 259         default:
 260           __gxx_abort ();
 261         }
 262
 263       if (result != 0)
 264         {
 265 #if __FDPIC__
 266           /* FDPIC relative addresses imply taking the GOT address
 267              into account.  */
 268           if ((encoding & DW_EH_PE_pcrel) && (encoding & DW_EH_PE_indirect))
 269             {
 270               result += _Unwind_gnu_Find_got ((_Unwind_Ptr) u);
 271               result = *(_Unwind_Internal_Ptr *) result;
 272             }
 273           else
 274             {
 275               result += ((encoding & 0x70) == DW_EH_PE_pcrel
 276                          ? (_Unwind_Internal_Ptr) u : base);
 277               if (encoding & DW_EH_PE_indirect)
 278                 result = *(_Unwind_Internal_Ptr *) result;
 279             }
 280 #else
 281           result += ((encoding & 0x70) == DW_EH_PE_pcrel
 282                      ? (_Unwind_Internal_Ptr) u : base);
 283           if (encoding & DW_EH_PE_indirect)
 284             result = *(_Unwind_Internal_Ptr *) result;
 285 #endif
 286         }
 287     }
 288
 289   *val = result;
 290   return p;
 291 }
 292
 293 #pragma GCC diagnostic pop
 294
 295 #ifndef NO_BASE_OF_ENCODED_VALUE
 296
 297 /* Like read_encoded_value_with_base, but get the base from the context
 298    rather than providing it directly.  */
 299
 300 static inline const unsigned char *
 301 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
 302                     const unsigned char *p, _Unwind_Ptr *val)
 303 {
 304   return read_encoded_value_with_base (encoding,
 305                 base_of_encoded_value (encoding, context),
 306                 p, val);
 307 }
 308
 309 #endif
 310
 311 #endif /* unwind-pe.h */