src/mc/mc_dwarf_expression.c

   1
   2 #include <stdint.h>
   3 #include <stdarg.h>
   4
   5 #include <dwarf.h>
   6 #include <elfutils/libdw.h>
   7
   8 #include "mc_private.h"
   9
  10 static int mc_dwarf_push_value(mc_expression_state_t state, Dwarf_Off value) {
  11   if(state->stack_size>=MC_EXPRESSION_STACK_SIZE)
  12     return MC_EXPRESSION_E_STACK_OVERFLOW;
  13
  14   state->stack[state->stack_size++] = value;
  15   return 0;
  16 }
  17
  18 int mc_dwarf_execute_expression(
  19   size_t n, const Dwarf_Op* ops, mc_expression_state_t state) {
  20   for(int i=0; i!=n; ++i) {
  21     int error = 0;
  22     const Dwarf_Op* op = ops + i;
  23     uint8_t atom = op->atom;
  24
  25     switch (atom) {
  26
  27     // Registers:
  28
  29     case DW_OP_breg0: case DW_OP_breg1: case DW_OP_breg2: case DW_OP_breg3:
  30     case DW_OP_breg4: case DW_OP_breg5: case DW_OP_breg6: case DW_OP_breg7:
  31     case DW_OP_breg8: case DW_OP_breg9: case DW_OP_breg10: case DW_OP_breg11:
  32     case DW_OP_breg12: case DW_OP_breg13: case DW_OP_breg14: case DW_OP_breg15:
  33     case DW_OP_breg16: case DW_OP_breg17: case DW_OP_breg18: case DW_OP_breg19:
  34     case DW_OP_breg20: case DW_OP_breg21: case DW_OP_breg22: case DW_OP_breg23:
  35     case DW_OP_breg24: case DW_OP_breg25: case DW_OP_breg26: case DW_OP_breg27:
  36     case DW_OP_breg28: case DW_OP_breg29: case DW_OP_breg30: case DW_OP_breg31:{
  37         int register_id = op->atom - DW_OP_breg0;
  38         unw_word_t res;
  39         if(!state->cursor)
  40           return MC_EXPRESSION_E_MISSING_STACK_CONTEXT;
  41         unw_get_reg(state->cursor, register_id, &res);
  42         error = mc_dwarf_push_value(state, res + op->number);
  43         break;
  44       }
  45
  46     // Push the CFA (Canonical Frame Addresse):
  47     case DW_OP_call_frame_cfa:
  48     {
  49       // UNW_X86_64_CFA does not return the CFA DWARF expects
  50       // (it is a synonym for UNW_X86_64_RSP) so copy the cursor,
  51       // unwind it once in order to find the parent SP:
  52
  53       if(!state->cursor)
  54         return MC_EXPRESSION_E_MISSING_STACK_CONTEXT;
  55
  56       // Get frame:
  57       unw_cursor_t cursor = *(state->cursor);
  58       unw_step(&cursor);
  59
  60       unw_word_t res;
  61       unw_get_reg(&cursor, UNW_TDEP_SP, &res);
  62       error = mc_dwarf_push_value(state, res);
  63       break;
  64     }
  65
  66     // Frame base:
  67
  68     case DW_OP_fbreg:
  69       {
  70         if(!state->frame_base)
  71           return MC_EXPRESSION_E_MISSING_FRAME_BASE;
  72         error = mc_dwarf_push_value(state, ((uintptr_t)state->frame_base) + op->number);
  73         break;
  74       }
  75
  76
  77     // Constants:
  78
  79     case DW_OP_lit0: case DW_OP_lit1: case DW_OP_lit2: case DW_OP_lit3:
  80     case DW_OP_lit4: case DW_OP_lit5: case DW_OP_lit6: case DW_OP_lit7:
  81     case DW_OP_lit8: case DW_OP_lit9: case DW_OP_lit10: case DW_OP_lit11:
  82     case DW_OP_lit12: case DW_OP_lit13: case DW_OP_lit14: case DW_OP_lit15:
  83     case DW_OP_lit16: case DW_OP_lit17: case DW_OP_lit18: case DW_OP_lit19:
  84     case DW_OP_lit20: case DW_OP_lit21: case DW_OP_lit22: case DW_OP_lit23:
  85     case DW_OP_lit24: case DW_OP_lit25: case DW_OP_lit26: case DW_OP_lit27:
  86     case DW_OP_lit28: case DW_OP_lit29: case DW_OP_lit30: case DW_OP_lit31:
  87       error = mc_dwarf_push_value(state, atom - DW_OP_lit0);
  88       break;
  89
  90     case DW_OP_addr:
  91       if(!state->object_info)
  92         return MC_EXPRESSION_E_NO_BASE_ADDRESS;
  93       if(state->stack_size==MC_EXPRESSION_STACK_SIZE)
  94         return MC_EXPRESSION_E_STACK_OVERFLOW;
  95       error = mc_dwarf_push_value(state,  (Dwarf_Off)MC_object_base_address(state->object_info) + op->number);
  96       break;
  97
  98     case DW_OP_const1u:
  99     case DW_OP_const2u:
 100     case DW_OP_const4u:
 101     case DW_OP_const8u:
 102     case DW_OP_const1s:
 103     case DW_OP_const2s:
 104     case DW_OP_const4s:
 105     case DW_OP_const8s:
 106     case DW_OP_constu:
 107     case DW_OP_consts:
 108       if(state->stack_size==MC_EXPRESSION_STACK_SIZE)
 109         return MC_EXPRESSION_E_STACK_OVERFLOW;
 110       error = mc_dwarf_push_value(state, op->number);
 111       break;
 112
 113     // Stack manipulation:
 114
 115     // Push the value at the top of the stack:
 116     case DW_OP_dup:
 117       if(state->stack_size==0)
 118         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 119       else
 120         error = mc_dwarf_push_value(state, state->stack[state->stack_size-1]);
 121       break;
 122
 123     case DW_OP_drop:
 124       if(state->stack_size==0)
 125         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 126       else
 127         state->stack_size--;
 128       break;
 129
 130     case DW_OP_swap:
 131       if(state->stack_size<2)
 132         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 133       {
 134         uintptr_t temp = state->stack[state->stack_size-2];
 135         state->stack[state->stack_size-2] = state->stack[state->stack_size-1];
 136         state->stack[state->stack_size-1] = temp;
 137       }
 138       break;
 139
 140     case DW_OP_over:
 141       if(state->stack_size<2)
 142         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 143       error = mc_dwarf_push_value(state, state->stack[state->stack_size-2]);
 144       break;
 145
 146     // Operations:
 147
 148     case DW_OP_plus:
 149       if(state->stack_size<2)
 150         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 151       {
 152         uintptr_t result = state->stack[state->stack_size-2] + state->stack[state->stack_size-1];
 153         state->stack[state->stack_size-2] = result;
 154         state->stack_size--;
 155       }
 156       break;
 157
 158     case DW_OP_mul:
 159       if(state->stack_size<2)
 160         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 161       {
 162         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 163         state->stack[state->stack_size-2] = result;
 164         state->stack_size--;
 165       }
 166       break;
 167
 168     case DW_OP_plus_uconst:
 169       if(state->stack_size==0)
 170         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 171       state->stack[state->stack_size-1] += op->number;
 172       break;
 173
 174     case DW_OP_not:
 175       if(state->stack_size==0)
 176         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 177       state->stack[state->stack_size-1] = ~state->stack[state->stack_size-1];
 178       break;
 179
 180     case DW_OP_neg:
 181       if(state->stack_size==0)
 182         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 183       {
 184         intptr_t value = state->stack[state->stack_size-1];
 185         if(value<0) value = -value;
 186         state->stack[state->stack_size-1] = value;
 187       }
 188       break;
 189
 190     case DW_OP_minus:
 191       if(state->stack_size<2)
 192         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 193       {
 194         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 195         state->stack[state->stack_size-2] = result;
 196         state->stack_size--;
 197       }
 198       break;
 199
 200     case DW_OP_and:
 201       if(state->stack_size<2)
 202         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 203       {
 204         uintptr_t result = state->stack[state->stack_size-2] & state->stack[state->stack_size-1];
 205         state->stack[state->stack_size-2] = result;
 206         state->stack_size--;
 207       }
 208       break;
 209
 210     case DW_OP_or:
 211       if(state->stack_size<2)
 212         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 213       {
 214         uintptr_t result = state->stack[state->stack_size-2] | state->stack[state->stack_size-1];
 215         state->stack[state->stack_size-2] = result;
 216         state->stack_size--;
 217       }
 218       break;
 219
 220     case DW_OP_xor:
 221       if(state->stack_size<2)
 222         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 223       {
 224         uintptr_t result = state->stack[state->stack_size-2] ^ state->stack[state->stack_size-1];
 225         state->stack[state->stack_size-2] = result;
 226         state->stack_size--;
 227       }
 228       break;
 229
 230     case DW_OP_nop:
 231       break;
 232
 233     // Dereference:
 234     case DW_OP_deref_size:
 235       return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 236
 237     case DW_OP_deref:
 238       if(state->stack_size==0)
 239         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 240       {
 241         // Computed address:
 242         uintptr_t address = (uintptr_t) state->stack[state->stack_size-1];
 243         uintptr_t* p = (uintptr_t*)mc_translate_address(address, state->snapshot);
 244         state->stack[state->stack_size-1] = *p;
 245       }
 246       break;
 247
 248     // Not handled:
 249     default:
 250      return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 251     }
 252
 253     if(error) return error;
 254   }
 255   return 0;
 256 }
 257
 258 // ***** Location
 259
 260 /** \brief Resolve a location expression
 261  *  \deprecated Use mc_dwarf_resolve_expression
 262  */
 263 uintptr_t mc_dwarf_resolve_location(mc_expression_t expression, mc_object_info_t object_info, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 264   s_mc_expression_state_t state;
 265   memset(&state, 0, sizeof(s_mc_expression_state_t));
 266   state.frame_base = frame_pointer_address;
 267   state.cursor = c;
 268   state.snapshot = snapshot;
 269   state.object_info = object_info;
 270
 271   if(mc_dwarf_execute_expression(expression->size, expression->ops, &state))
 272     xbt_die("Error evaluating DWARF expression");
 273   if(state.stack_size==0)
 274     xbt_die("No value on the stack");
 275   else
 276     return state.stack[state.stack_size-1];
 277 }
 278
 279 uintptr_t mc_dwarf_resolve_locations(mc_location_list_t locations, mc_object_info_t object_info, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 280
 281   unw_word_t ip;
 282   if(c) {
 283     if(unw_get_reg(c, UNW_REG_IP, &ip))
 284       xbt_die("Could not resolve IP");
 285   }
 286
 287   for(size_t i=0; i!=locations->size; ++i) {
 288     mc_expression_t expression = locations->locations + i;
 289     if( (expression->lowpc==NULL && expression->highpc==NULL)
 290       || (c && ip >= (unw_word_t) expression->lowpc && ip < (unw_word_t) expression->highpc)) {
 291       return mc_dwarf_resolve_location(expression, object_info, c, frame_pointer_address, snapshot);
 292     }
 293   }
 294   xbt_die("Could not resolve location");
 295 }
 296
 297 /** \brief Find the frame base of a given frame
 298  *
 299  *  \param frame
 300  *  \param unw_cursor
 301  */
 302 void* mc_find_frame_base(dw_frame_t frame, mc_object_info_t object_info, unw_cursor_t* unw_cursor) {
 303   return (void*) mc_dwarf_resolve_locations(&frame->frame_base, object_info, unw_cursor, NULL, NULL);
 304 }
 305
 306 void mc_dwarf_expression_clear(mc_expression_t expression) {
 307   free(expression->ops);
 308   expression->ops = NULL;
 309   expression->size = 0;
 310   expression->lowpc = NULL;
 311   expression->highpc = NULL;
 312 }
 313
 314 void mc_dwarf_location_list_clear(mc_location_list_t list) {
 315   for(size_t i=0; i!=list->size; ++i) {
 316     mc_dwarf_expression_clear(list->locations + i);
 317   }
 318   free(list->locations);
 319   list->locations = NULL;
 320   list->size = 0;
 321 }
 322
 323 void mc_dwarf_expression_init(mc_expression_t expression, size_t len, Dwarf_Op* ops) {
 324   if(expression->ops) {
 325     free(expression->ops);
 326   }
 327   expression->lowpc = NULL;
 328   expression->highpc = NULL;
 329   expression->size = len;
 330   expression->ops = xbt_malloc(len*sizeof(Dwarf_Op));
 331   memcpy(expression->ops, ops, len*sizeof(Dwarf_Op));
 332 }
 333
 334 void mc_dwarf_location_list_init_from_expression(mc_location_list_t target, size_t len, Dwarf_Op* ops) {
 335   if(target->locations) {
 336     mc_dwarf_location_list_clear(target);
 337   }
 338   target->size = 1;
 339   target->locations = (mc_expression_t) xbt_malloc(sizeof(s_mc_expression_t));
 340   mc_dwarf_expression_init(target->locations, len, ops);
 341 }
 342
 343 void mc_dwarf_location_list_init(mc_location_list_t list, mc_object_info_t info, Dwarf_Die* die, Dwarf_Attribute* attr) {
 344   if(list->locations) {
 345     mc_dwarf_location_list_clear(list);
 346   }
 347   list->size = 0;
 348
 349   ptrdiff_t offset = 0;
 350   Dwarf_Addr base, start, end;
 351   Dwarf_Op *ops;
 352   size_t len;
 353
 354   while (1) {
 355
 356     offset = dwarf_getlocations(attr, offset, &base, &start, &end, &ops, &len);
 357     if (offset==0)
 358       return;
 359     else if (offset==-1)
 360       xbt_die("Error while loading location list");
 361
 362     int i = list->size;
 363     list->size++;
 364     list->locations = (mc_expression_t) realloc(list->locations, list->size*sizeof(s_mc_expression_t));
 365     mc_expression_t expression = list->locations + i;
 366
 367     void* base = info->flags & MC_OBJECT_INFO_EXECUTABLE ? 0 : MC_object_base_address(info);
 368     mc_dwarf_expression_init(expression, len, ops);
 369
 370     // If start == 0, this is not a location list:
 371     expression->lowpc = start == 0 ? NULL : (char*) base + start;
 372     expression->highpc = start == 0 ? NULL : (char*) base + end;
 373   }
 374
 375 }