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     case DW_OP_const1u:
  92     case DW_OP_const2u:
  93     case DW_OP_const4u:
  94     case DW_OP_const8u:
  95     case DW_OP_const1s:
  96     case DW_OP_const2s:
  97     case DW_OP_const4s:
  98     case DW_OP_const8s:
  99     case DW_OP_constu:
 100     case DW_OP_consts:
 101       if(state->stack_size==MC_EXPRESSION_STACK_SIZE)
 102         return MC_EXPRESSION_E_STACK_OVERFLOW;
 103       error = mc_dwarf_push_value(state, op->number);
 104       break;
 105
 106     // Stack manipulation:
 107
 108     // Push the value at the top of the stack:
 109     case DW_OP_dup:
 110       if(state->stack_size==0)
 111         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 112       else
 113         error = mc_dwarf_push_value(state, state->stack[state->stack_size-1]);
 114       break;
 115
 116     case DW_OP_drop:
 117       if(state->stack_size==0)
 118         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 119       else
 120         state->stack_size--;
 121       break;
 122
 123     case DW_OP_swap:
 124       if(state->stack_size<2)
 125         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 126       {
 127         uintptr_t temp = state->stack[state->stack_size-2];
 128         state->stack[state->stack_size-2] = state->stack[state->stack_size-1];
 129         state->stack[state->stack_size-1] = temp;
 130       }
 131       break;
 132
 133     case DW_OP_over:
 134       if(state->stack_size<2)
 135         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 136       error = mc_dwarf_push_value(state, state->stack[state->stack_size-2]);
 137       break;
 138
 139     // Operations:
 140
 141     case DW_OP_plus:
 142       if(state->stack_size<2)
 143         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 144       {
 145         uintptr_t result = state->stack[state->stack_size-2] + state->stack[state->stack_size-1];
 146         state->stack[state->stack_size-2] = result;
 147         state->stack_size--;
 148       }
 149       break;
 150
 151     case DW_OP_mul:
 152       if(state->stack_size<2)
 153         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 154       {
 155         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 156         state->stack[state->stack_size-2] = result;
 157         state->stack_size--;
 158       }
 159       break;
 160
 161     case DW_OP_plus_uconst:
 162       if(state->stack_size==0)
 163         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 164       state->stack[state->stack_size-1] += op->number;
 165       break;
 166
 167     case DW_OP_not:
 168       if(state->stack_size==0)
 169         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 170       state->stack[state->stack_size-1] = ~state->stack[state->stack_size-1];
 171       break;
 172
 173     case DW_OP_neg:
 174       if(state->stack_size==0)
 175         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 176       {
 177         intptr_t value = state->stack[state->stack_size-1];
 178         if(value<0) value = -value;
 179         state->stack[state->stack_size-1] = value;
 180       }
 181       break;
 182
 183     case DW_OP_minus:
 184       if(state->stack_size<2)
 185         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 186       {
 187         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 188         state->stack[state->stack_size-2] = result;
 189         state->stack_size--;
 190       }
 191       break;
 192
 193     case DW_OP_and:
 194       if(state->stack_size<2)
 195         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 196       {
 197         uintptr_t result = state->stack[state->stack_size-2] & state->stack[state->stack_size-1];
 198         state->stack[state->stack_size-2] = result;
 199         state->stack_size--;
 200       }
 201       break;
 202
 203     case DW_OP_or:
 204       if(state->stack_size<2)
 205         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 206       {
 207         uintptr_t result = state->stack[state->stack_size-2] | state->stack[state->stack_size-1];
 208         state->stack[state->stack_size-2] = result;
 209         state->stack_size--;
 210       }
 211       break;
 212
 213     case DW_OP_xor:
 214       if(state->stack_size<2)
 215         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 216       {
 217         uintptr_t result = state->stack[state->stack_size-2] ^ state->stack[state->stack_size-1];
 218         state->stack[state->stack_size-2] = result;
 219         state->stack_size--;
 220       }
 221       break;
 222
 223     case DW_OP_nop:
 224       break;
 225
 226     // Dereference:
 227     case DW_OP_deref_size:
 228       return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 229
 230     case DW_OP_deref:
 231       if(state->stack_size==0)
 232         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 233       {
 234         // Computed address:
 235         uintptr_t address = (uintptr_t) state->stack[state->stack_size-1];
 236         uintptr_t* p = (uintptr_t*)mc_translate_address(address, state->snapshot);
 237         state->stack[state->stack_size-1] = *p;
 238       }
 239       break;
 240
 241     // Not handled:
 242     default:
 243      return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 244     }
 245
 246     if(error) return error;
 247   }
 248   return 0;
 249 }
 250
 251 // ***** Location
 252
 253 /** \brief Resolve a location expression
 254  *  \deprecated Use mc_dwarf_resolve_expression
 255  */
 256 Dwarf_Off mc_dwarf_resolve_location(mc_expression_t expression, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 257   s_mc_expression_state_t state;
 258   memset(&state, 0, sizeof(s_mc_expression_state_t));
 259   state.frame_base = frame_pointer_address;
 260   state.cursor = c;
 261   state.snapshot = snapshot;
 262
 263   if(mc_dwarf_execute_expression(expression->size, expression->ops, &state))
 264     xbt_die("Error evaluating DWARF expression");
 265   if(state.stack_size==0)
 266     xbt_die("No value on the stack");
 267   else
 268     return (Dwarf_Off) state.stack[state.stack_size-1];
 269 }
 270
 271 Dwarf_Off mc_dwarf_resolve_locations(mc_location_list_t locations, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 272
 273   unw_word_t ip;
 274   if(c) {
 275     if(unw_get_reg(c, UNW_REG_IP, &ip))
 276       xbt_die("Could not resolve IP");
 277   }
 278
 279   for(size_t i=0; i!=locations->size; ++i) {
 280     mc_expression_t expression = locations->locations + i;
 281     if( (expression->lowpc==NULL && expression->highpc==NULL)
 282       || (c && ip >= (unw_word_t) expression->lowpc && ip < (unw_word_t) expression->highpc)) {
 283       return mc_dwarf_resolve_location(expression, c, frame_pointer_address, snapshot);
 284     }
 285   }
 286   xbt_die("Could not resolve location");
 287 }
 288
 289 /** \brief Find the frame base of a given frame
 290  *
 291  *  \param frame
 292  *  \param unw_cursor
 293  */
 294 void* mc_find_frame_base(dw_frame_t frame, unw_cursor_t* unw_cursor) {
 295   return (void*) mc_dwarf_resolve_locations(&frame->frame_base, unw_cursor, NULL, NULL);
 296 }
 297
 298 void mc_dwarf_expression_clear(mc_expression_t expression) {
 299   free(expression->ops);
 300   expression->ops = NULL;
 301   expression->size = 0;
 302   expression->lowpc = NULL;
 303   expression->highpc = NULL;
 304 }
 305
 306 void mc_dwarf_location_list_clear(mc_location_list_t list) {
 307   for(size_t i=0; i!=list->size; ++i) {
 308     mc_dwarf_expression_clear(list->locations + i);
 309   }
 310   free(list->locations);
 311   list->locations = NULL;
 312   list->size = 0;
 313 }
 314
 315 void mc_dwarf_expression_init(mc_expression_t expression, size_t len, Dwarf_Op* ops) {
 316   if(expression->ops) {
 317     free(expression->ops);
 318   }
 319   expression->lowpc = NULL;
 320   expression->highpc = NULL;
 321   expression->size = len;
 322   expression->ops = xbt_malloc(len*sizeof(Dwarf_Op));
 323   memcpy(expression->ops, ops, len*sizeof(Dwarf_Op));
 324 }
 325
 326 void mc_dwarf_location_list_init_from_expression(mc_location_list_t target, size_t len, Dwarf_Op* ops) {
 327   if(target->locations) {
 328     mc_dwarf_location_list_clear(target);
 329   }
 330   target->size = 1;
 331   target->locations = (mc_expression_t) xbt_malloc(sizeof(s_mc_expression_t));
 332   mc_dwarf_expression_init(target->locations, len, ops);
 333 }
 334
 335 void mc_dwarf_location_list_init(mc_location_list_t list, mc_object_info_t info, Dwarf_Die* die, Dwarf_Attribute* attr) {
 336   if(list->locations) {
 337     mc_dwarf_location_list_clear(list);
 338   }
 339   list->size = 0;
 340
 341   ptrdiff_t offset = 0;
 342   Dwarf_Addr base, start, end;
 343   Dwarf_Op *ops;
 344   size_t len;
 345
 346   while (1) {
 347
 348     offset = dwarf_getlocations(attr, offset, &base, &start, &end, &ops, &len);
 349     if (offset==0)
 350       return;
 351     else if (offset==-1)
 352       xbt_die("Error while loading location list");
 353
 354     int i = list->size;
 355     list->size++;
 356     list->locations = (mc_expression_t) realloc(list->locations, list->size*sizeof(s_mc_expression_t));
 357     mc_expression_t expression = list->locations + i;
 358
 359     void* base = info->flags & MC_OBJECT_INFO_EXECUTABLE ? 0 : MC_object_base_address(info);
 360     mc_dwarf_expression_init(expression, len, ops);
 361
 362     // If start == 0, this is not a location list:
 363     expression->lowpc = start == 0 ? NULL : (char*) base + start;
 364     expression->highpc = start == 0 ? NULL : (char*) base + end;
 365   }
 366
 367 }