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 (Call Frame Addresse):
  47     case DW_OP_call_frame_cfa:
  48     {
  49       unw_word_t res;
  50
  51       int register_id =
  52 #if defined(UNW_TARGET_X86_64)
  53           UNW_X86_64_CFA
  54 #elif defined(UNW_TARGET_X86)
  55           UNW_X86_CFA
  56 #else
  57           -1;
  58 #endif
  59         ;
  60       if(register_id<0)
  61         xbt_die("Support for CFA not implemented for this achitecture.");
  62
  63       if(!state->cursor)
  64         return MC_EXPRESSION_E_MISSING_STACK_CONTEXT;
  65
  66       unw_get_reg(state->cursor, register_id, &res);
  67       error = mc_dwarf_push_value(state, res);
  68       break;
  69     }
  70
  71     // Frame base:
  72
  73     case DW_OP_fbreg:
  74       {
  75         if(!state->frame_base)
  76           return MC_EXPRESSION_E_MISSING_FRAME_BASE;
  77         error = mc_dwarf_push_value(state, ((uintptr_t)state->frame_base) + op->number);
  78         break;
  79       }
  80
  81
  82     // Constants:
  83
  84     case DW_OP_lit0: case DW_OP_lit1: case DW_OP_lit2: case DW_OP_lit3:
  85     case DW_OP_lit4: case DW_OP_lit5: case DW_OP_lit6: case DW_OP_lit7:
  86     case DW_OP_lit8: case DW_OP_lit9: case DW_OP_lit10: case DW_OP_lit11:
  87     case DW_OP_lit12: case DW_OP_lit13: case DW_OP_lit14: case DW_OP_lit15:
  88     case DW_OP_lit16: case DW_OP_lit17: case DW_OP_lit18: case DW_OP_lit19:
  89     case DW_OP_lit20: case DW_OP_lit21: case DW_OP_lit22: case DW_OP_lit23:
  90     case DW_OP_lit24: case DW_OP_lit25: case DW_OP_lit26: case DW_OP_lit27:
  91     case DW_OP_lit28: case DW_OP_lit29: case DW_OP_lit30: case DW_OP_lit31:
  92       error = mc_dwarf_push_value(state, atom - DW_OP_lit0);
  93       break;
  94
  95     case DW_OP_addr:
  96     case DW_OP_const1u:
  97     case DW_OP_const2u:
  98     case DW_OP_const4u:
  99     case DW_OP_const8u:
 100     case DW_OP_const1s:
 101     case DW_OP_const2s:
 102     case DW_OP_const4s:
 103     case DW_OP_const8s:
 104     case DW_OP_constu:
 105     case DW_OP_consts:
 106       if(state->stack_size==MC_EXPRESSION_STACK_SIZE)
 107         return MC_EXPRESSION_E_STACK_OVERFLOW;
 108       error = mc_dwarf_push_value(state, op->number);
 109       break;
 110
 111     // Stack manipulation:
 112
 113     // Push the value at the top of the stack:
 114     case DW_OP_dup:
 115       if(state->stack_size==0)
 116         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 117       else
 118         error = mc_dwarf_push_value(state, state->stack[state->stack_size-1]);
 119       break;
 120
 121     case DW_OP_drop:
 122       if(state->stack_size==0)
 123         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 124       else
 125         state->stack_size--;
 126       break;
 127
 128     case DW_OP_swap:
 129       if(state->stack_size<2)
 130         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 131       {
 132         uintptr_t temp = state->stack[state->stack_size-2];
 133         state->stack[state->stack_size-2] = state->stack[state->stack_size-1];
 134         state->stack[state->stack_size-1] = temp;
 135       }
 136       break;
 137
 138     case DW_OP_over:
 139       if(state->stack_size<2)
 140         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 141       error = mc_dwarf_push_value(state, state->stack[state->stack_size-2]);
 142       break;
 143
 144     // Operations:
 145
 146     case DW_OP_plus:
 147       if(state->stack_size<2)
 148         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 149       {
 150         uintptr_t result = state->stack[state->stack_size-2] + state->stack[state->stack_size-1];
 151         state->stack[state->stack_size-2] = result;
 152         state->stack_size--;
 153       }
 154       break;
 155
 156     case DW_OP_mul:
 157       if(state->stack_size<2)
 158         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 159       {
 160         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 161         state->stack[state->stack_size-2] = result;
 162         state->stack_size--;
 163       }
 164       break;
 165
 166     case DW_OP_plus_uconst:
 167       if(state->stack_size==0)
 168         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 169       state->stack[state->stack_size-1] += op->number;
 170       break;
 171
 172     case DW_OP_not:
 173       if(state->stack_size==0)
 174         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 175       state->stack[state->stack_size-1] = ~state->stack[state->stack_size-1];
 176       break;
 177
 178     case DW_OP_neg:
 179       if(state->stack_size==0)
 180         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 181       {
 182         intptr_t value = state->stack[state->stack_size-1];
 183         if(value<0) value = -value;
 184         state->stack[state->stack_size-1] = value;
 185       }
 186       break;
 187
 188     case DW_OP_minus:
 189       if(state->stack_size<2)
 190         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 191       {
 192         uintptr_t result = state->stack[state->stack_size-2] - state->stack[state->stack_size-1];
 193         state->stack[state->stack_size-2] = result;
 194         state->stack_size--;
 195       }
 196       break;
 197
 198     case DW_OP_and:
 199       if(state->stack_size<2)
 200         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 201       {
 202         uintptr_t result = state->stack[state->stack_size-2] & state->stack[state->stack_size-1];
 203         state->stack[state->stack_size-2] = result;
 204         state->stack_size--;
 205       }
 206       break;
 207
 208     case DW_OP_or:
 209       if(state->stack_size<2)
 210         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 211       {
 212         uintptr_t result = state->stack[state->stack_size-2] | state->stack[state->stack_size-1];
 213         state->stack[state->stack_size-2] = result;
 214         state->stack_size--;
 215       }
 216       break;
 217
 218     case DW_OP_xor:
 219       if(state->stack_size<2)
 220         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 221       {
 222         uintptr_t result = state->stack[state->stack_size-2] ^ state->stack[state->stack_size-1];
 223         state->stack[state->stack_size-2] = result;
 224         state->stack_size--;
 225       }
 226       break;
 227
 228     case DW_OP_nop:
 229       break;
 230
 231     // Dereference:
 232     case DW_OP_deref_size:
 233       return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 234
 235     case DW_OP_deref:
 236       if(state->stack_size==0)
 237         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 238       {
 239         // Computed address:
 240         uintptr_t address = (uintptr_t) state->stack[state->stack_size-1];
 241         uintptr_t* p = (uintptr_t*)mc_translate_address(address, state->snapshot);
 242         state->stack[state->stack_size-1] = *p;
 243       }
 244       break;
 245
 246     // Not handled:
 247     default:
 248      return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 249     }
 250
 251     if(error) return error;
 252   }
 253   return 0;
 254 }
 255
 256 // ***** Location
 257
 258 /** \brief Resolve a location expression
 259  *  \deprecated Use mc_dwarf_resolve_expression
 260  */
 261 Dwarf_Off mc_dwarf_resolve_location(mc_expression_t expression, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 262   s_mc_expression_state_t state;
 263   memset(&state, 0, sizeof(s_mc_expression_state_t));
 264   state.frame_base = frame_pointer_address;
 265   state.cursor = c;
 266   state.snapshot = snapshot;
 267
 268   if(mc_dwarf_execute_expression(expression->size, expression->ops, &state))
 269     xbt_die("Error evaluating DWARF expression");
 270   if(state.stack_size==0)
 271     xbt_die("No value on the stack");
 272   else
 273     return (Dwarf_Off) state.stack[state.stack_size-1];
 274 }
 275
 276 Dwarf_Off mc_dwarf_resolve_locations(mc_location_list_t locations, unw_cursor_t* c, void* frame_pointer_address, mc_snapshot_t snapshot) {
 277
 278   unw_word_t ip;
 279   if(c) {
 280     if(unw_get_reg(c, UNW_REG_IP, &ip))
 281       xbt_die("Could not resolve IP");
 282   }
 283
 284   for(size_t i=0; i!=locations->size; ++i) {
 285     mc_expression_t expression = locations->locations + i;
 286     if( (expression->lowpc==NULL && expression->highpc==NULL)
 287       || (c && ip >= (unw_word_t) expression->lowpc && ip < (unw_word_t) expression->highpc)) {
 288       return mc_dwarf_resolve_location(expression, c, frame_pointer_address, snapshot);
 289     }
 290   }
 291   xbt_die("Could not resolve location");
 292 }
 293
 294 /** \brief Find the frame base of a given frame
 295  *
 296  *  \param frame
 297  *  \param unw_cursor
 298  */
 299 void* mc_find_frame_base(dw_frame_t frame, unw_cursor_t* unw_cursor) {
 300   return (void*) mc_dwarf_resolve_locations(&frame->frame_base, unw_cursor, NULL, NULL);
 301 }
 302
 303 void mc_dwarf_expression_clear(mc_expression_t expression) {
 304   free(expression->ops);
 305   expression->ops = NULL;
 306   expression->size = 0;
 307   expression->lowpc = NULL;
 308   expression->highpc = NULL;
 309 }
 310
 311 void mc_dwarf_location_list_clear(mc_location_list_t list) {
 312   for(size_t i=0; i!=list->size; ++i) {
 313     mc_dwarf_expression_clear(list->locations + i);
 314   }
 315   free(list->locations);
 316   list->locations = NULL;
 317   list->size = 0;
 318 }
 319
 320 void mc_dwarf_expression_init(mc_expression_t expression, size_t len, Dwarf_Op* ops) {
 321   if(expression->ops) {
 322     free(expression->ops);
 323   }
 324   expression->lowpc = NULL;
 325   expression->highpc = NULL;
 326   expression->size = len;
 327   expression->ops = xbt_malloc(len*sizeof(Dwarf_Op));
 328   memcpy(expression->ops, ops, len*sizeof(Dwarf_Op));
 329 }
 330
 331 void mc_dwarf_location_list_init_from_expression(mc_location_list_t target, size_t len, Dwarf_Op* ops) {
 332   if(target->locations) {
 333     mc_dwarf_location_list_clear(target);
 334   }
 335   target->size = 1;
 336   target->locations = (mc_expression_t) xbt_malloc(sizeof(s_mc_expression_t));
 337   mc_dwarf_expression_init(target->locations, len, ops);
 338 }
 339
 340 void mc_dwarf_location_list_init(mc_location_list_t list, mc_object_info_t info, Dwarf_Die* die, Dwarf_Attribute* attr) {
 341   if(list->locations) {
 342     mc_dwarf_location_list_clear(list);
 343   }
 344   list->size = 0;
 345
 346   ptrdiff_t offset = 0;
 347   Dwarf_Addr base, start, end;
 348   Dwarf_Op *ops;
 349   size_t len;
 350
 351   while (1) {
 352
 353     offset = dwarf_getlocations(attr, offset, &base, &start, &end, &ops, &len);
 354     if (offset==0)
 355       return;
 356     else if (offset==-1)
 357       xbt_die("Error while loading location list");
 358
 359     int i = list->size;
 360     list->size++;
 361     list->locations = (mc_expression_t) realloc(list->locations, list->size*sizeof(s_mc_expression_t));
 362     mc_expression_t expression = list->locations + i;
 363
 364     void* base = info->flags & MC_OBJECT_INFO_EXECUTABLE ? 0 : MC_object_base_address(info);
 365     mc_dwarf_expression_init(expression, len, ops);
 366
 367     // If start == 0, this is not a location list:
 368     expression->lowpc = start == 0 ? NULL : (char*) base + start;
 369     expression->highpc = start == 0 ? NULL : (char*) base + end;
 370   }
 371
 372 }