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 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 2, 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    You should have received a copy of the GNU General Public License
  17    along with GCC; see the file COPYING.  If not, write to the Free
  18    Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  19    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 /* Read an unsigned leb128 value from P, store the value in VAL, return
 112    P incremented past the value.  We assume that a word is large enough to
 113    hold any value so encoded; if it is smaller than a pointer on some target,
 114    pointers should not be leb128 encoded on that target.  */
 115
 116 static const unsigned char *
 117 read_uleb128 (const unsigned char *p, _Unwind_Word *val)
 118 {
 119   unsigned int shift = 0;
 120   unsigned char byte;
 121   _Unwind_Word result;
 122
 123   result = 0;
 124   do
 125     {
 126       byte = *p++;
 127       result |= (byte & 0x7f) << shift;
 128       shift += 7;
 129     }
 130   while (byte & 0x80);
 131
 132   *val = result;
 133   return p;
 134 }
 135
 136 /* Similar, but read a signed leb128 value.  */
 137
 138 static const unsigned char *
 139 read_sleb128 (const unsigned char *p, _Unwind_Sword *val)
 140 {
 141   unsigned int shift = 0;
 142   unsigned char byte;
 143   _Unwind_Word result;
 144
 145   result = 0;
 146   do
 147     {
 148       byte = *p++;
 149       result |= (byte & 0x7f) << shift;
 150       shift += 7;
 151     }
 152   while (byte & 0x80);
 153
 154   /* Sign-extend a negative value.  */
 155   if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
 156     result |= -(1L << shift);
 157
 158   *val = (_Unwind_Sword) result;
 159   return p;
 160 }
 161
 162 /* Load an encoded value from memory at P.  The value is returned in VAL;
 163    The function returns P incremented past the value.  BASE is as given
 164    by base_of_encoded_value for this encoding in the appropriate context.  */
 165
 166 static const unsigned char *
 167 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
 168                               const unsigned char *p, _Unwind_Ptr *val)
 169 {
 170   union unaligned
 171     {
 172       void *ptr;
 173       unsigned u2 __attribute__ ((mode (HI)));
 174       unsigned u4 __attribute__ ((mode (SI)));
 175       unsigned u8 __attribute__ ((mode (DI)));
 176       signed s2 __attribute__ ((mode (HI)));
 177       signed s4 __attribute__ ((mode (SI)));
 178       signed s8 __attribute__ ((mode (DI)));
 179     } __attribute__((__packed__));
 180
 181   union unaligned *u = (union unaligned *) p;
 182   _Unwind_Ptr result;
 183
 184   if (encoding == DW_EH_PE_aligned)
 185     {
 186       _Unwind_Ptr a = (_Unwind_Ptr)p;
 187       a = (a + sizeof (void *) - 1) & - sizeof(void *);
 188       result = *(_Unwind_Ptr *) a;
 189       p = (const unsigned char *)(a + sizeof (void *));
 190     }
 191   else
 192     {
 193       switch (encoding & 0x0f)
 194         {
 195         case DW_EH_PE_absptr:
 196           result = (_Unwind_Ptr) u->ptr;
 197           p += sizeof (void *);
 198           break;
 199
 200         case DW_EH_PE_uleb128:
 201           {
 202             _Unwind_Word tmp;
 203             p = read_uleb128 (p, &tmp);
 204             result = (_Unwind_Ptr)tmp;
 205           }
 206           break;
 207
 208         case DW_EH_PE_sleb128:
 209           {
 210             _Unwind_Sword tmp;
 211             p = read_sleb128 (p, &tmp);
 212             result = (_Unwind_Ptr)tmp;
 213           }
 214           break;
 215
 216         case DW_EH_PE_udata2:
 217           result = u->u2;
 218           p += 2;
 219           break;
 220         case DW_EH_PE_udata4:
 221           result = u->u4;
 222           p += 4;
 223           break;
 224         case DW_EH_PE_udata8:
 225           result = u->u8;
 226           p += 8;
 227           break;
 228
 229         case DW_EH_PE_sdata2:
 230           result = u->s2;
 231           p += 2;
 232           break;
 233         case DW_EH_PE_sdata4:
 234           result = u->s4;
 235           p += 4;
 236           break;
 237         case DW_EH_PE_sdata8:
 238           result = u->s8;
 239           p += 8;
 240           break;
 241
 242         default:
 243           __gxx_abort ();
 244         }
 245
 246       if (result != 0)
 247         {
 248           result += ((encoding & 0x70) == DW_EH_PE_pcrel
 249                      ? (_Unwind_Ptr)u : base);
 250           if (encoding & DW_EH_PE_indirect)
 251             result = *(_Unwind_Ptr *)result;
 252         }
 253     }
 254
 255   *val = result;
 256   return p;
 257 }
 258
 259 #ifndef NO_BASE_OF_ENCODED_VALUE
 260
 261 /* Like read_encoded_value_with_base, but get the base from the context
 262    rather than providing it directly.  */
 263
 264 static inline const unsigned char *
 265 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
 266                     const unsigned char *p, _Unwind_Ptr *val)
 267 {
 268   return read_encoded_value_with_base (encoding,
 269                 base_of_encoded_value (encoding, context),
 270                 p, val);
 271 }
 272
 273 #endif