src/mc/mc_dwarf_expression.cpp

   1 /* Copyright (c) 2014. The SimGrid Team.
   2  * All rights reserved.                                                     */
   3
   4 /* This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the license (GNU LGPL) which comes with this package. */
   6
   7 #include <stdint.h>
   8 #include <stdarg.h>
   9
  10 #include <dwarf.h>
  11 #include <elfutils/libdw.h>
  12
  13 #include "mc_object_info.h"
  14 #include "mc_private.h"
  15
  16 using simgrid::mc::remote;
  17
  18 extern "C" {
  19
  20 static int mc_dwarf_push_value(mc_expression_state_t state, Dwarf_Off value)
  21 {
  22   if (state->stack_size >= MC_EXPRESSION_STACK_SIZE)
  23     return MC_EXPRESSION_E_STACK_OVERFLOW;
  24
  25   state->stack[state->stack_size++] = value;
  26   return 0;
  27 }
  28
  29 /** Convert a DWARF register into a libunwind register
  30  *
  31  *  DWARF and libunwind does not use the same convention for numbering the
  32  *  registers on some architectures. The function makes the necessary
  33  *  convertion.
  34  */
  35 static int mc_dwarf_register_to_libunwind(int dwarf_register)
  36 {
  37 #if defined(UNW_TARGET_X86_64)
  38   // It seems for this arch, DWARF and libunwind agree in the numbering:
  39   return dwarf_register;
  40 #elif defined(UNW_TARGET_X86)
  41   // Could't find the authoritative source of information for this.
  42   // This is inspired from http://source.winehq.org/source/dlls/dbghelp/cpu_i386.c#L517.
  43   switch (dwarf_register) {
  44   case 0:
  45     return UNW_X86_EAX;
  46   case 1:
  47     return UNW_X86_ECX;
  48   case 2:
  49     return UNW_X86_EDX;
  50   case 3:
  51     return UNW_X86_EBX;
  52   case 4:
  53     return UNW_X86_ESP;
  54   case 5:
  55     return UNW_X86_EBP;
  56   case 6:
  57     return UNW_X86_ESI;
  58   case 7:
  59     return UNW_X86_EDI;
  60   case 8:
  61     return UNW_X86_EIP;
  62   case 9:
  63     return UNW_X86_EFLAGS;
  64   case 10:
  65     return UNW_X86_CS;
  66   case 11:
  67     return UNW_X86_SS;
  68   case 12:
  69     return UNW_X86_DS;
  70   case 13:
  71     return UNW_X86_ES;
  72   case 14:
  73     return UNW_X86_FS;
  74   case 15:
  75     return UNW_X86_GS;
  76   case 16:
  77     return UNW_X86_ST0;
  78   case 17:
  79     return UNW_X86_ST1;
  80   case 18:
  81     return UNW_X86_ST2;
  82   case 19:
  83     return UNW_X86_ST3;
  84   case 20:
  85     return UNW_X86_ST4;
  86   case 21:
  87     return UNW_X86_ST5;
  88   case 22:
  89     return UNW_X86_ST6;
  90   case 23:
  91     return UNW_X86_ST7;
  92   default:
  93     xbt_die("Bad/unknown register number.");
  94   }
  95 #else
  96 #error This architecture is not supported yet for DWARF expression evaluation.
  97 #endif
  98 }
  99
 100 int mc_dwarf_execute_expression(size_t n, const Dwarf_Op * ops,
 101                                 mc_expression_state_t state)
 102 {
 103   for (size_t i = 0; i != n; ++i) {
 104     int error = 0;
 105     const Dwarf_Op *op = ops + i;
 106     uint8_t atom = op->atom;
 107
 108     switch (atom) {
 109
 110       // Registers:
 111
 112     case DW_OP_breg0:
 113     case DW_OP_breg1:
 114     case DW_OP_breg2:
 115     case DW_OP_breg3:
 116     case DW_OP_breg4:
 117     case DW_OP_breg5:
 118     case DW_OP_breg6:
 119     case DW_OP_breg7:
 120     case DW_OP_breg8:
 121     case DW_OP_breg9:
 122     case DW_OP_breg10:
 123     case DW_OP_breg11:
 124     case DW_OP_breg12:
 125     case DW_OP_breg13:
 126     case DW_OP_breg14:
 127     case DW_OP_breg15:
 128     case DW_OP_breg16:
 129     case DW_OP_breg17:
 130     case DW_OP_breg18:
 131     case DW_OP_breg19:
 132     case DW_OP_breg20:
 133     case DW_OP_breg21:
 134     case DW_OP_breg22:
 135     case DW_OP_breg23:
 136     case DW_OP_breg24:
 137     case DW_OP_breg25:
 138     case DW_OP_breg26:
 139     case DW_OP_breg27:
 140     case DW_OP_breg28:
 141     case DW_OP_breg29:
 142     case DW_OP_breg30:
 143     case DW_OP_breg31:{
 144         int register_id =
 145             mc_dwarf_register_to_libunwind(op->atom - DW_OP_breg0);
 146         unw_word_t res;
 147         if (!state->cursor)
 148           return MC_EXPRESSION_E_MISSING_STACK_CONTEXT;
 149         unw_get_reg(state->cursor, register_id, &res);
 150         error = mc_dwarf_push_value(state, res + op->number);
 151         break;
 152       }
 153
 154       // Push the CFA (Canonical Frame Addresse):
 155     case DW_OP_call_frame_cfa:
 156       {
 157         // UNW_X86_64_CFA does not return the CFA DWARF expects
 158         // (it is a synonym for UNW_X86_64_RSP) so copy the cursor,
 159         // unwind it once in order to find the parent SP:
 160
 161         if (!state->cursor)
 162           return MC_EXPRESSION_E_MISSING_STACK_CONTEXT;
 163
 164         // Get frame:
 165         unw_cursor_t cursor = *(state->cursor);
 166         unw_step(&cursor);
 167
 168         unw_word_t res;
 169         unw_get_reg(&cursor, UNW_TDEP_SP, &res);
 170         error = mc_dwarf_push_value(state, res);
 171         break;
 172       }
 173
 174       // Frame base:
 175
 176     case DW_OP_fbreg:
 177       {
 178         if (!state->frame_base)
 179           return MC_EXPRESSION_E_MISSING_FRAME_BASE;
 180         uintptr_t fb = ((uintptr_t) state->frame_base) + op->number;
 181         error = mc_dwarf_push_value(state, fb);
 182         break;
 183       }
 184
 185
 186       // ***** Constants:
 187
 188       // Short constant literals:
 189       // DW_OP_lit15 pushed the 15 on the stack.
 190     case DW_OP_lit0:
 191     case DW_OP_lit1:
 192     case DW_OP_lit2:
 193     case DW_OP_lit3:
 194     case DW_OP_lit4:
 195     case DW_OP_lit5:
 196     case DW_OP_lit6:
 197     case DW_OP_lit7:
 198     case DW_OP_lit8:
 199     case DW_OP_lit9:
 200     case DW_OP_lit10:
 201     case DW_OP_lit11:
 202     case DW_OP_lit12:
 203     case DW_OP_lit13:
 204     case DW_OP_lit14:
 205     case DW_OP_lit15:
 206     case DW_OP_lit16:
 207     case DW_OP_lit17:
 208     case DW_OP_lit18:
 209     case DW_OP_lit19:
 210     case DW_OP_lit20:
 211     case DW_OP_lit21:
 212     case DW_OP_lit22:
 213     case DW_OP_lit23:
 214     case DW_OP_lit24:
 215     case DW_OP_lit25:
 216     case DW_OP_lit26:
 217     case DW_OP_lit27:
 218     case DW_OP_lit28:
 219     case DW_OP_lit29:
 220     case DW_OP_lit30:
 221     case DW_OP_lit31:
 222       error = mc_dwarf_push_value(state, atom - DW_OP_lit0);
 223       break;
 224
 225       // Address from the base address of this ELF object.
 226       // Push the address on the stack (base_address + argument).
 227     case DW_OP_addr: {
 228       if (!state->object_info)
 229         return MC_EXPRESSION_E_NO_BASE_ADDRESS;
 230       if (state->stack_size == MC_EXPRESSION_STACK_SIZE)
 231         return MC_EXPRESSION_E_STACK_OVERFLOW;
 232       Dwarf_Off addr = (Dwarf_Off) (uintptr_t)
 233         MC_object_base_address(state->object_info) + op->number;
 234       error = mc_dwarf_push_value(state, addr);
 235       break;
 236     }
 237
 238       // General constants:
 239       // Push the constant argument on the stack.
 240     case DW_OP_const1u:
 241     case DW_OP_const2u:
 242     case DW_OP_const4u:
 243     case DW_OP_const8u:
 244     case DW_OP_const1s:
 245     case DW_OP_const2s:
 246     case DW_OP_const4s:
 247     case DW_OP_const8s:
 248     case DW_OP_constu:
 249     case DW_OP_consts:
 250       if (state->stack_size == MC_EXPRESSION_STACK_SIZE)
 251         return MC_EXPRESSION_E_STACK_OVERFLOW;
 252       error = mc_dwarf_push_value(state, op->number);
 253       break;
 254
 255       // ***** Stack manipulation:
 256
 257       // Push another copy/duplicate the value at the top of the stack:
 258     case DW_OP_dup:
 259       if (state->stack_size == 0)
 260         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 261       else
 262         error = mc_dwarf_push_value(state, state->stack[state->stack_size - 1]);
 263       break;
 264
 265       // Pop/drop the top of the stack:
 266     case DW_OP_drop:
 267       if (state->stack_size == 0)
 268         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 269       else
 270         state->stack_size--;
 271       break;
 272
 273       // Swap the two top-most value of the stack:
 274     case DW_OP_swap:
 275       if (state->stack_size < 2)
 276         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 277       {
 278         uintptr_t temp = state->stack[state->stack_size - 2];
 279         state->stack[state->stack_size - 2] =
 280             state->stack[state->stack_size - 1];
 281         state->stack[state->stack_size - 1] = temp;
 282       }
 283       break;
 284
 285       // Duplicate the value under the top of the stack:
 286     case DW_OP_over:
 287       if (state->stack_size < 2)
 288         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 289       error = mc_dwarf_push_value(state, state->stack[state->stack_size - 2]);
 290       break;
 291
 292       // ***** Operations:
 293       // Those usually take the top of the stack and the next value as argument
 294       // and replace the top of the stack with the computed value
 295       // (stack.top() += stack.before_top()).
 296
 297     case DW_OP_plus:
 298       if (state->stack_size < 2)
 299         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 300       {
 301         uintptr_t result =
 302             state->stack[state->stack_size - 2] +
 303             state->stack[state->stack_size - 1];
 304         state->stack[state->stack_size - 2] = result;
 305         state->stack_size--;
 306       }
 307       break;
 308
 309     case DW_OP_mul:
 310       if (state->stack_size < 2)
 311         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 312       {
 313         uintptr_t result =
 314             state->stack[state->stack_size - 2] -
 315             state->stack[state->stack_size - 1];
 316         state->stack[state->stack_size - 2] = result;
 317         state->stack_size--;
 318       }
 319       break;
 320
 321     case DW_OP_plus_uconst:
 322       if (state->stack_size == 0)
 323         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 324       state->stack[state->stack_size - 1] += op->number;
 325       break;
 326
 327     case DW_OP_not:
 328       if (state->stack_size == 0)
 329         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 330       state->stack[state->stack_size - 1] =
 331           ~state->stack[state->stack_size - 1];
 332       break;
 333
 334     case DW_OP_neg:
 335       if (state->stack_size == 0)
 336         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 337       {
 338         intptr_t value = state->stack[state->stack_size - 1];
 339         if (value < 0)
 340           value = -value;
 341         state->stack[state->stack_size - 1] = value;
 342       }
 343       break;
 344
 345     case DW_OP_minus:
 346       if (state->stack_size < 2)
 347         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 348       {
 349         uintptr_t result =
 350             state->stack[state->stack_size - 2] -
 351             state->stack[state->stack_size - 1];
 352         state->stack[state->stack_size - 2] = result;
 353         state->stack_size--;
 354       }
 355       break;
 356
 357     case DW_OP_and:
 358       if (state->stack_size < 2)
 359         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 360       {
 361         uintptr_t result =
 362             state->stack[state->stack_size -
 363                          2] & state->stack[state->stack_size - 1];
 364         state->stack[state->stack_size - 2] = result;
 365         state->stack_size--;
 366       }
 367       break;
 368
 369     case DW_OP_or:
 370       if (state->stack_size < 2)
 371         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 372       {
 373         uintptr_t result =
 374             state->stack[state->stack_size -
 375                          2] | state->stack[state->stack_size - 1];
 376         state->stack[state->stack_size - 2] = result;
 377         state->stack_size--;
 378       }
 379       break;
 380
 381     case DW_OP_xor:
 382       if (state->stack_size < 2)
 383         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 384       {
 385         uintptr_t result =
 386             state->stack[state->stack_size -
 387                          2] ^ state->stack[state->stack_size - 1];
 388         state->stack[state->stack_size - 2] = result;
 389         state->stack_size--;
 390       }
 391       break;
 392
 393     case DW_OP_nop:
 394       break;
 395
 396       // ***** Deference (memory fetch)
 397
 398     case DW_OP_deref_size:
 399       return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 400
 401     case DW_OP_deref:
 402       if (state->stack_size == 0)
 403         return MC_EXPRESSION_E_STACK_UNDERFLOW;
 404       {
 405         // Computed address:
 406         uintptr_t address = (uintptr_t) state->stack[state->stack_size - 1];
 407         if (!state->address_space)
 408           xbt_die("Missing address space");
 409         state->address_space->read_bytes(
 410           &state->stack[state->stack_size - 1], sizeof(uintptr_t),
 411           remote(address), state->process_index);
 412       }
 413       break;
 414
 415       // Not handled:
 416     default:
 417       return MC_EXPRESSION_E_UNSUPPORTED_OPERATION;
 418     }
 419
 420     if (error)
 421       return error;
 422   }
 423   return 0;
 424 }
 425
 426 // ***** Location
 427
 428 /** \brief Resolve a location expression
 429  *  \deprecated Use mc_dwarf_resolve_expression
 430  */
 431 void mc_dwarf_resolve_location(mc_location_t location,
 432                                mc_expression_t expression,
 433                                mc_object_info_t object_info,
 434                                unw_cursor_t * c,
 435                                void *frame_pointer_address,
 436                                mc_address_space_t address_space, int process_index)
 437 {
 438   s_mc_expression_state_t state;
 439   memset(&state, 0, sizeof(s_mc_expression_state_t));
 440   state.frame_base = frame_pointer_address;
 441   state.cursor = c;
 442   state.address_space = address_space;
 443   state.object_info = object_info;
 444   state.process_index = process_index;
 445
 446   if (expression->size >= 1
 447     && expression->ops[0].atom >=DW_OP_reg0 && expression->ops[0].atom <= DW_OP_reg31) {
 448     int dwarf_register = expression->ops[0].atom - DW_OP_reg0;
 449     xbt_assert(c, "Missing frame context for register operation DW_OP_reg%i",
 450       dwarf_register);
 451     location->memory_location = NULL;
 452     location->cursor = c;
 453     location->register_id = mc_dwarf_register_to_libunwind(dwarf_register);
 454     return;
 455   }
 456
 457   if (mc_dwarf_execute_expression(expression->size, expression->ops, &state))
 458     xbt_die("Error evaluating DWARF expression");
 459   if (state.stack_size == 0)
 460     xbt_die("No value on the stack");
 461   else {
 462     location->memory_location = (void*) state.stack[state.stack_size - 1];
 463     location->cursor = NULL;
 464     location->register_id = 0;
 465   }
 466 }
 467
 468 static mc_expression_t mc_find_expression(mc_location_list_t locations, unw_word_t ip) {
 469   for (size_t i = 0; i != locations->size; ++i) {
 470     mc_expression_t expression = locations->locations + i;
 471     if ((expression->lowpc == NULL && expression->highpc == NULL)
 472         || (ip && ip >= (unw_word_t) expression->lowpc
 473             && ip < (unw_word_t) expression->highpc)) {
 474       return expression;
 475     }
 476   }
 477   return NULL;
 478 }
 479
 480 void mc_dwarf_resolve_locations(mc_location_t location,
 481                                      mc_location_list_t locations,
 482                                      mc_object_info_t object_info,
 483                                      unw_cursor_t * c,
 484                                      void *frame_pointer_address,
 485                                      mc_address_space_t address_space, int process_index)
 486 {
 487
 488   unw_word_t ip = 0;
 489   if (c) {
 490     if (unw_get_reg(c, UNW_REG_IP, &ip))
 491       xbt_die("Could not resolve IP");
 492   }
 493
 494   mc_expression_t expression = mc_find_expression(locations, ip);
 495   if (expression) {
 496     mc_dwarf_resolve_location(location,
 497                               expression, object_info, c,
 498                               frame_pointer_address, address_space, process_index);
 499   } else {
 500     xbt_die("Could not resolve location");
 501   }
 502 }
 503
 504 /** \brief Find the frame base of a given frame
 505  *
 506  *  \param frame
 507  *  \param unw_cursor
 508  */
 509 void *mc_find_frame_base(dw_frame_t frame, mc_object_info_t object_info,
 510                          unw_cursor_t * unw_cursor)
 511 {
 512   s_mc_location_t location;
 513   mc_dwarf_resolve_locations(&location,
 514                              &frame->frame_base, object_info,
 515                              unw_cursor, NULL, NULL, -1);
 516   switch(mc_get_location_type(&location)) {
 517   case MC_LOCATION_TYPE_ADDRESS:
 518     return location.memory_location;
 519
 520   case MC_LOCATION_TYPE_REGISTER: {
 521       // This is a special case.
 522       // The register if not the location of the frame base
 523       // (a frame base cannot be located in a register)
 524       // Instead, DWARF defines this to mean that the register
 525       // contains the address of the frame base.
 526       unw_word_t word;
 527       unw_get_reg(location.cursor, location.register_id, &word);
 528       return (void*) word;
 529     }
 530
 531   default:
 532     xbt_die("Cannot handle non-address frame base");
 533     return NULL; // Unreachable
 534   }
 535 }
 536
 537 void mc_dwarf_expression_clear(mc_expression_t expression)
 538 {
 539   free(expression->ops);
 540   expression->ops = NULL;
 541   expression->size = 0;
 542   expression->lowpc = NULL;
 543   expression->highpc = NULL;
 544 }
 545
 546 void mc_dwarf_location_list_clear(mc_location_list_t list)
 547 {
 548   for (size_t i = 0; i != list->size; ++i) {
 549     mc_dwarf_expression_clear(list->locations + i);
 550   }
 551   free(list->locations);
 552   list->locations = NULL;
 553   list->size = 0;
 554 }
 555
 556 void mc_dwarf_expression_init(mc_expression_t expression, size_t len,
 557                               Dwarf_Op * ops)
 558 {
 559   expression->lowpc = NULL;
 560   expression->highpc = NULL;
 561   expression->size = len;
 562   expression->ops = (Dwarf_Op*) xbt_malloc(len * sizeof(Dwarf_Op));
 563   memcpy(expression->ops, ops, len * sizeof(Dwarf_Op));
 564 }
 565
 566 void mc_dwarf_location_list_init_from_expression(mc_location_list_t target,
 567                                                  size_t len, Dwarf_Op * ops)
 568 {
 569   target->size = 1;
 570   target->locations = (mc_expression_t) xbt_malloc(sizeof(s_mc_expression_t));
 571   mc_dwarf_expression_init(target->locations, len, ops);
 572 }
 573
 574 void mc_dwarf_location_list_init(mc_location_list_t list, mc_object_info_t info,
 575                                  Dwarf_Die * die, Dwarf_Attribute * attr)
 576 {
 577   if (list->locations) {
 578     mc_dwarf_location_list_clear(list);
 579   }
 580   list->size = 0;
 581
 582   ptrdiff_t offset = 0;
 583   Dwarf_Addr base, start, end;
 584   Dwarf_Op *ops;
 585   size_t len;
 586
 587   while (1) {
 588
 589     offset = dwarf_getlocations(attr, offset, &base, &start, &end, &ops, &len);
 590     if (offset == 0)
 591       return;
 592     else if (offset == -1)
 593       xbt_die("Error while loading location list");
 594
 595     int i = list->size;
 596     list->size++;
 597     list->locations =
 598         (mc_expression_t) realloc(list->locations,
 599                                   list->size * sizeof(s_mc_expression_t));
 600     mc_expression_t expression = list->locations + i;
 601     expression->ops = NULL;
 602     mc_dwarf_expression_init(expression, len, ops);
 603
 604     void *base =
 605         info->
 606         flags & MC_OBJECT_INFO_EXECUTABLE ? 0 : MC_object_base_address(info);
 607     // If start == 0, this is not a location list:
 608     expression->lowpc = start == 0 ? NULL : (char *) base + start;
 609     expression->highpc = start == 0 ? NULL : (char *) base + end;
 610   }
 611
 612 }
 613
 614 }