common/h/dwarfExpr.h

   1 /*
   2  * Copyright (c) 1996-2011 Barton P. Miller
   3  *
   4  * We provide the Paradyn Parallel Performance Tools (below
   5  * described as "Paradyn") on an AS IS basis, and do not warrant its
   6  * validity or performance.  We reserve the right to update, modify,
   7  * or discontinue this software at any time.  We shall have no
   8  * obligation to supply such updates or modifications or any other
   9  * form of support to you.
  10  *
  11  * By your use of Paradyn, you understand and agree that we (or any
  12  * other person or entity with proprietary rights in Paradyn) are
  13  * under no obligation to provide either maintenance services,
  14  * update services, notices of latent defects, or correction of
  15  * defects for Paradyn.
  16  *
  17  * This library is free software; you can redistribute it and/or
  18  * modify it under the terms of the GNU Lesser General Public
  19  * License as published by the Free Software Foundation; either
  20  * version 2.1 of the License, or (at your option) any later version.
  21  *
  22  * This library is distributed in the hope that it will be useful,
  23  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  24  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  25  * Lesser General Public License for more details.
  26  *
  27  * You should have received a copy of the GNU Lesser General Public
  28  * License along with this library; if not, write to the Free Software
  29  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  30  */
  31
  32 #include <stack>
  33 #include "dynutil/h/dyn_regs.h"
  34 #if !defined(DWARF_EXPR_H)
  35 #define DWARF_EXPR_H
  36
  37 using namespace std;
  38 using namespace Dyninst;
  39
  40 #if defined(arch_x86_64)
  41 // We can only safely map the general purpose registers (0-7 on ia-32,
  42 // 0-15 on amd-64)
  43 #define IA32_MAX_MAP 7
  44 #define AMD64_MAX_MAP 15
  45 static int const amd64_register_map[] =
  46   {
  47     0,  // RAX
  48     2,  // RDX
  49     1,  // RCX
  50     3,  // RBX
  51     6,  // RSI
  52     7,  // RDI
  53     5,  // RBP
  54     4,  // RSP
  55     8, 9, 10, 11, 12, 13, 14, 15    // gp 8 - 15
  56     /* This is incomplete. The x86_64 ABI specifies a mapping from
  57        dwarf numbers (0-66) to ("architecture number"). Without a
  58        corresponding mapping for the SVR4 dwarf-machine encoding for
  59        IA-32, however, it is not meaningful to provide this mapping. */
  60   };
  61
  62 static int Register_DWARFtoMachineEnc32(int n)
  63 {
  64   if (n > IA32_MAX_MAP) {
  65     dwarf_printf("%s[%d]: unexpected map lookup for DWARF register %d\n",
  66                  __FILE__,__LINE__,n);
  67   }
  68   return n;
  69 }
  70
  71
  72 static int Register_DWARFtoMachineEnc64(int n)
  73 {
  74   if (n <= AMD64_MAX_MAP)
  75     return amd64_register_map[n];
  76   else {
  77     dwarf_printf("%s[%d]: unexpected map lookup for DWARF register %d\n",
  78                  __FILE__,__LINE__,n);
  79     return n;
  80   }
  81 }
  82
  83 #define DWARF_TO_MACHINE_ENC(n, proc)                                   \
  84   ((proc->getAddressWidth() == 4) ? Register_DWARFtoMachineEnc32((int) n) : Register_DWARFtoMachineEnc64((int) n))
  85 #define DWARF_TO_MACHINE_ENC_W(n, w) \
  86   (w == 4) ? Register_DWARFtoMachineEnc32((int) n) : Register_DWARFtoMachineEnc64((int) n)
  87 #define DWARF_TO_MACHINEREG_ENC_W(n, w) \
  88    (w == 4) ? MachRegister::DwarfEncToReg(n, Dyninst::Arch_x86) : MachRegister::DwarfEncToReg(n, Dyninst::Arch_x86_64);
  89 #else
  90 #define DWARF_TO_MACHINE_ENC(n, proc) (n)
  91 #define DWARF_TO_MACHINE_ENC_W(n, w) (n)
  92 #define DWARF_TO_MACHINEREG_ENC_W(n, w) MachRegister::DwarfEncToReg(n, Dyninst::Arch_x86);
  93 #endif
  94
  95 #define DWARF_FALSE_IF(condition,...)           \
  96   if ( condition ) { return false; }
  97 #define DWARF_RETURN_IF(condition,...)          \
  98   if ( condition ) { return; }
  99 #define DWARF_NULL_IF(condition,...)            \
 100   if ( condition ) { return NULL; }
 101 #define DWARF_NEXT_IF(condition, ...)                                   \
 102   if (condition) { if (depth != 1) { return false; } else {walk_error = true; break; } }
 103
 104
 105 static Dyninst::MachRegister DwarfToDynReg(Dwarf_Signed reg, Dyninst::Architecture arch)
 106 {
 107    return MachRegister::DwarfEncToReg(reg, arch);
 108 }
 109
 110 static Dwarf_Signed DynToDwarfReg(Dyninst::MachRegister reg)
 111 {
 112    return reg.getDwarfEnc();
 113 }
 114
 115 static bool decodeDwarfExpression(Dwarf_Locdesc *dwlocs,
 116                                   long int *initialStackValue,
 117                                   VariableLocation *loc, bool &isLocSet,
 118                                   ProcessReader *reader,
 119                                   Dyninst::Architecture arch,
 120                                   long int &end_result)
 121 {
 122    /* Initialize the stack. */
 123    int addr_width = getArchAddressWidth(arch);
 124    std::stack< long int > opStack = std::stack<long int>();
 125    if ( initialStackValue != NULL ) { opStack.push( * initialStackValue ); }
 126
 127    Dwarf_Loc *locations = dwlocs->ld_s;
 128    unsigned count = dwlocs->ld_cents;
 129    for ( unsigned int i = 0; i < count; i++ )
 130    {
 131       /* Handle the literals w/o 32 case statements. */
 132       if ( DW_OP_lit0 <= locations[i].lr_atom && locations[i].lr_atom <= DW_OP_lit31 )
 133       {
 134          dwarf_printf( "pushing named constant: %d\n", locations[i].lr_atom - DW_OP_lit0 );
 135          opStack.push( locations[i].lr_atom - DW_OP_lit0 );
 136          continue;
 137       }
 138
 139       /* Haandle registers w/o 32 case statements. */
 140       if ( DW_OP_reg0 <= locations[i].lr_atom && locations[i].lr_atom <= DW_OP_reg31 )
 141       {
 142          /* storageReg is unimplemented, so do an offset of 0 from the named register instead. */
 143          dwarf_printf( "location is named register %d\n",
 144                        DWARF_TO_MACHINE_ENC_W(locations[i].lr_atom - DW_OP_reg0, addr_width) );
 145          //loc->stClass = storageRegOffset;
 146          if (loc)
 147          {
 148             loc->stClass = storageReg;
 149             loc->refClass = storageNoRef;
 150             loc->frameOffset = 0;
 151             loc->reg = DWARF_TO_MACHINE_ENC_W(locations[i].lr_atom - DW_OP_reg0, addr_width);
 152             loc->mr_reg = DWARF_TO_MACHINEREG_ENC_W(locations[i].lr_atom - DW_OP_reg0, addr_width);
 153             //loc->frameOffset = 0;
 154             isLocSet = true;
 155          }
 156          continue;
 157       }
 158
 159       /* Haandle registers w/o 32 case statements. */
 160       if ( DW_OP_breg0 <= locations[i].lr_atom && locations[i].lr_atom <= DW_OP_breg31 )
 161       {
 162          dwarf_printf( "setting storage class to named register, regNum to %d, offset %d\n", DWARF_TO_MACHINE_ENC_W(locations[i].lr_atom - DW_OP_breg0, addr_width), locations[i].lr_number );
 163          long int to_push;
 164          if (loc) {
 165             loc->stClass = storageRegOffset;
 166             loc->refClass = storageNoRef;
 167             loc->frameOffset = locations[i].lr_number ;
 168             loc->reg = DWARF_TO_MACHINE_ENC_W(locations[i].lr_atom - DW_OP_breg0, addr_width);
 169             loc->mr_reg = DWARF_TO_MACHINEREG_ENC_W(locations[i].lr_atom - DW_OP_breg0, addr_width);
 170             to_push = static_cast<long int>(locations[i].lr_number);
 171          }
 172          else if (reader) {
 173             Dyninst::MachRegister r = DwarfToDynReg(locations[i].lr_atom - DW_OP_breg0,
 174                                                     arch);
 175             Dyninst::MachRegisterVal v;
 176             bool result = reader->GetReg(r, v);
 177             if (!result) {
 178                return false;
 179             }
 180             to_push = (long int) v + locations[i].lr_number;
 181          }
 182
 183          opStack.push(to_push);
 184          continue;
 185       }
 186
 187       switch( locations[i].lr_atom )
 188       {
 189          case DW_OP_addr:
 190          case DW_OP_const1u:
 191          case DW_OP_const2u:
 192          case DW_OP_const4u:
 193          case DW_OP_const8u:
 194          case DW_OP_constu:
 195             dwarf_printf( "pushing unsigned constant %lu\n",
 196                           (unsigned long)locations[i].lr_number );
 197             opStack.push(static_cast<long int>(locations[i].lr_number));
 198             break;
 199
 200          case DW_OP_const1s:
 201          case DW_OP_const2s:
 202          case DW_OP_const4s:
 203          case DW_OP_const8s:
 204          case DW_OP_consts:
 205             dwarf_printf( "pushing signed constant %ld\n",
 206                           (signed long)(locations[i].lr_number) );
 207             opStack.push(static_cast<long int>(locations[i].lr_number));
 208             break;
 209
 210          case DW_OP_regx:
 211             /* storageReg is unimplemented, so do an offset of 0 from the named register instead. */
 212             dwarf_printf( "location is register %d\n",
 213                           DWARF_TO_MACHINE_ENC_W(locations[i].lr_number, addr_width) );
 214             if (loc) {
 215                loc->stClass = storageReg;
 216                loc->refClass = storageNoRef;
 217                loc->reg = (int) DWARF_TO_MACHINE_ENC_W(locations[i].lr_number, addr_width);
 218                loc->mr_reg = DWARF_TO_MACHINEREG_ENC_W(locations[i].lr_number, addr_width);
 219                loc->frameOffset = 0;
 220                isLocSet = true;
 221             }
 222             break;
 223
 224          case DW_OP_fbreg:
 225          {
 226             dwarf_printf( "setting storage class to frame base\n" );
 227             //if ( storageClass != NULL ) { * storageClass = storageFrameOffset; }
 228             long int to_push = 0;
 229             if (loc) {
 230                loc->stClass = storageRegOffset;
 231                loc->refClass = storageNoRef;
 232                loc->frameOffset = 0;
 233                to_push = static_cast<long int>(locations[i].lr_number);
 234             }
 235             else if (reader) {
 236                Dyninst::MachRegister r = Dyninst::FrameBase;
 237                Dyninst::MachRegisterVal v;
 238                bool result = reader->GetReg(r, v);
 239                if (!result) {
 240                   return false;
 241                }
 242                to_push = (long int) v + locations[i].lr_number;
 243             }
 244             opStack.push(to_push);
 245          } break;
 246          case DW_OP_bregx:
 247          {
 248             dwarf_printf( "setting storage class to register, regNum to %d\n",
 249                           locations[i].lr_number );
 250             long int to_push = 0;
 251             if (loc) {
 252                loc->stClass = storageRegOffset;
 253                loc->refClass = storageNoRef;
 254                loc->reg = (int) DWARF_TO_MACHINE_ENC_W( locations[i].lr_number, addr_width );
 255                loc->mr_reg = DWARF_TO_MACHINEREG_ENC_W( locations[i].lr_number, addr_width );
 256                loc->frameOffset = 0;
 257                to_push = static_cast<long int>(locations[i].lr_number2);
 258             }
 259             else if (reader) {
 260                Dyninst::MachRegister r = DwarfToDynReg(locations[i].lr_number, arch);
 261                Dyninst::MachRegisterVal v;
 262                bool result = reader->GetReg(r, v);
 263                if (!result) {
 264                   return false;
 265                }
 266                to_push = (long int) v + locations[i].lr_number2;
 267             }
 268             opStack.push(to_push);
 269          } break;
 270          case DW_OP_dup:
 271             DWARF_FALSE_IF( opStack.size() < 1,
 272                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 273             opStack.push( opStack.top() );
 274             break;
 275
 276          case DW_OP_drop:
 277             DWARF_FALSE_IF( opStack.size() < 1,
 278                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 279             opStack.pop();
 280             break;
 281
 282          case DW_OP_pick:
 283          {
 284             /* Duplicate the entry at index locations[i].lr_number. */
 285             std::stack< long int > temp = std::stack< long int >();
 286
 287             for ( unsigned int j = 0; j < locations[i].lr_number; j++ )
 288             {
 289                temp.push( opStack.top() ); opStack.pop();
 290             }
 291
 292             long int dup = opStack.top();
 293
 294             for ( unsigned int j = 0; j < locations[i].lr_number; j++ )
 295             {
 296                opStack.push( temp.top() ); temp.pop();
 297             }
 298
 299             opStack.push( dup );
 300          } break;
 301
 302          case DW_OP_over:
 303          {
 304             DWARF_FALSE_IF( opStack.size() < 2,
 305                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 306             long int first = opStack.top(); opStack.pop();
 307             long int second = opStack.top(); opStack.pop();
 308             opStack.push( second ); opStack.push( first ); opStack.push( second );
 309          } break;
 310
 311          case DW_OP_swap:
 312          {
 313             DWARF_FALSE_IF( opStack.size() < 2,
 314                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 315             long int first = opStack.top(); opStack.pop();
 316             long int second = opStack.top(); opStack.pop();
 317             opStack.push( first ); opStack.push( second );
 318          } break;
 319
 320          case DW_OP_deref:
 321          {
 322             if (!reader)
 323                break;
 324             long int addr = opStack.top(); opStack.pop();
 325             unsigned long to_push = 0;
 326             bool bresult = false;
 327             if (addr_width == 4) {
 328                uint32_t v;
 329                bresult = reader->ReadMem(addr, &v, sizeof(v));
 330                to_push = (unsigned long) v;
 331             }
 332             else if (addr_width == 8) {
 333                uint64_t v;
 334                bresult = reader->ReadMem(addr, &v, sizeof(v));
 335                to_push = (unsigned long) v;
 336             }
 337             DWARF_FALSE_IF(!bresult,
 338                            "%s[%d]: Could not read from %lx\n", addr);
 339             opStack.push(to_push);
 340             break;
 341          }
 342          case DW_OP_deref_size:
 343          {
 344             if (!reader)
 345                break;
 346             long int addr = opStack.top(); opStack.pop();
 347             int width = locations[i].lr_number;
 348             unsigned long to_push = 0;
 349             bool bresult = false;
 350             if (width == 1) {
 351                uint8_t v;
 352                bresult = reader->ReadMem(addr, &v, sizeof(v));
 353                to_push = (unsigned long) v;
 354             }
 355             if (width == 2) {
 356                uint16_t v;
 357                bresult = reader->ReadMem(addr, &v, sizeof(v));
 358                to_push = (unsigned long) v;
 359             }
 360             if (width == 4) {
 361                uint32_t v;
 362                bresult = reader->ReadMem(addr, &v, sizeof(v));
 363                to_push = (unsigned long) v;
 364             }
 365             else if (width == 8) {
 366                uint64_t v;
 367                bresult = reader->ReadMem(addr, &v, sizeof(v));
 368                to_push = (long int) v;
 369             }
 370             DWARF_FALSE_IF(!bresult,
 371                            "%s[%d]: Could not read from %lx\n", addr);
 372             opStack.push(to_push);
 373             break;
 374          }
 375          case DW_OP_rot:
 376          {
 377             DWARF_FALSE_IF( opStack.size() < 3,
 378                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 379             long int first = opStack.top(); opStack.pop();
 380             long int second = opStack.top(); opStack.pop();
 381             long int third = opStack.top(); opStack.pop();
 382             opStack.push( first ); opStack.push( third ); opStack.push( second );
 383          } break;
 384
 385          case DW_OP_abs:
 386          {
 387             DWARF_FALSE_IF( opStack.size() < 1,
 388                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 389             long int top = opStack.top(); opStack.pop();
 390             opStack.push( abs( top ) );
 391          } break;
 392
 393          case DW_OP_and:
 394          {
 395             DWARF_FALSE_IF( opStack.size() < 2,
 396                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 397             long int first = opStack.top(); opStack.pop();
 398             long int second = opStack.top(); opStack.pop();
 399             opStack.push( second & first );
 400          } break;
 401
 402          case DW_OP_div:
 403          {
 404             DWARF_FALSE_IF( opStack.size() < 2,
 405                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 406             long int first = opStack.top(); opStack.pop();
 407             long int second = opStack.top(); opStack.pop();
 408             opStack.push( second / first );
 409          } break;
 410
 411          case DW_OP_minus:
 412          {
 413             DWARF_FALSE_IF( opStack.size() < 2,
 414                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 415             long int first = opStack.top(); opStack.pop();
 416             long int second = opStack.top(); opStack.pop();
 417             opStack.push( second - first );
 418          } break;
 419
 420          case DW_OP_mod:
 421          {
 422             DWARF_FALSE_IF( opStack.size() < 2,
 423                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 424             long int first = opStack.top(); opStack.pop();
 425             long int second = opStack.top(); opStack.pop();
 426             opStack.push( second % first );
 427          } break;
 428
 429          case DW_OP_mul:
 430          {
 431             DWARF_FALSE_IF( opStack.size() < 2,
 432                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 433             long int first = opStack.top(); opStack.pop();
 434             long int second = opStack.top(); opStack.pop();
 435             opStack.push( second * first );
 436          } break;
 437
 438          case DW_OP_neg:
 439          {
 440             DWARF_FALSE_IF( opStack.size() < 1,
 441                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 442             long int first = opStack.top(); opStack.pop();
 443             opStack.push( first * (-1) );
 444          } break;
 445
 446          case DW_OP_not:
 447          {
 448             DWARF_FALSE_IF( opStack.size() < 1,
 449                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 450             long int first = opStack.top(); opStack.pop();
 451             opStack.push( ~ first );
 452          } break;
 453
 454          case DW_OP_or:
 455          {
 456             DWARF_FALSE_IF( opStack.size() < 2,
 457                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 458             long int first = opStack.top(); opStack.pop();
 459             long int second = opStack.top(); opStack.pop();
 460             opStack.push( second | first );
 461          } break;
 462
 463          case DW_OP_plus:
 464          {
 465             DWARF_FALSE_IF( opStack.size() < 2,
 466                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 467             long int first = opStack.top(); opStack.pop();
 468             long int second = opStack.top(); opStack.pop();
 469             opStack.push( second + first );
 470          } break;
 471
 472          case DW_OP_plus_uconst:
 473          {
 474             DWARF_FALSE_IF( opStack.size() < 1,
 475                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 476             long int first = opStack.top(); opStack.pop();
 477             opStack.push(static_cast<long int>(first + locations[i].lr_number));
 478          } break;
 479
 480          case DW_OP_shl:
 481          {
 482             DWARF_FALSE_IF( opStack.size() < 2,
 483                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 484             long int first = opStack.top(); opStack.pop();
 485             long int second = opStack.top(); opStack.pop();
 486             opStack.push( second << first );
 487          } break;
 488
 489          case DW_OP_shr:
 490          {
 491             DWARF_FALSE_IF( opStack.size() < 2,
 492                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 493             long int first = opStack.top(); opStack.pop();
 494             long int second = opStack.top(); opStack.pop();
 495
 496             opStack.push( (long int)((unsigned long)second >> (unsigned long)first) );
 497          } break;
 498
 499          case DW_OP_shra:
 500          {
 501             DWARF_FALSE_IF( opStack.size() < 2,
 502                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 503             long int first = opStack.top(); opStack.pop();
 504             long int second = opStack.top(); opStack.pop();
 505             opStack.push( second >> first );
 506          } break;
 507
 508          case DW_OP_xor:
 509          {
 510             DWARF_FALSE_IF( opStack.size() < 2,
 511                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 512             long int first = opStack.top(); opStack.pop();
 513             long int second = opStack.top(); opStack.pop();
 514             opStack.push( second ^ first );
 515          } break;
 516
 517          case DW_OP_le:
 518          {
 519             DWARF_FALSE_IF( opStack.size() < 2,
 520                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 521             long int first = opStack.top(); opStack.pop();
 522             long int second = opStack.top(); opStack.pop();
 523             opStack.push( first <= second ? 1 : 0 );
 524          } break;
 525
 526          case DW_OP_ge:
 527          {
 528             DWARF_FALSE_IF( opStack.size() < 2,
 529                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 530             long int first = opStack.top(); opStack.pop();
 531             long int second = opStack.top(); opStack.pop();
 532             opStack.push( first >= second ? 1 : 0 );
 533          } break;
 534
 535          case DW_OP_eq:
 536          {
 537             DWARF_FALSE_IF( opStack.size() < 2,
 538                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 539             long int first = opStack.top(); opStack.pop();
 540             long int second = opStack.top(); opStack.pop();
 541             opStack.push( first == second ? 1 : 0 );
 542          } break;
 543
 544          case DW_OP_lt:
 545          {
 546             DWARF_FALSE_IF( opStack.size() < 2,
 547                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 548             long int first = opStack.top(); opStack.pop();
 549             long int second = opStack.top(); opStack.pop();
 550             opStack.push( first < second ? 1 : 0 );
 551          } break;
 552
 553          case DW_OP_gt:
 554          {
 555             DWARF_FALSE_IF( opStack.size() < 2,
 556                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 557             long int first = opStack.top(); opStack.pop();
 558             long int second = opStack.top(); opStack.pop();
 559             opStack.push( first > second ? 1 : 0 );
 560          } break;
 561
 562          case DW_OP_ne:
 563          {
 564             DWARF_FALSE_IF( opStack.size() < 2,
 565                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 566             long int first = opStack.top(); opStack.pop();
 567             long int second = opStack.top(); opStack.pop();
 568             opStack.push( first != second ? 1 : 0 );
 569          } break;
 570
 571          case DW_OP_bra:
 572          {
 573             DWARF_FALSE_IF( opStack.size() < 1,
 574                             "%s[%d]: invalid stack, returning false.\n", __FILE__, __LINE__ );
 575             if ( opStack.top() == 0 ) { break; }
 576             opStack.pop();
 577          }
 578          case DW_OP_skip:
 579          {
 580             int bytes = (int)(Dwarf_Signed)locations[i].lr_number;
 581             unsigned int target = (unsigned int) locations[i].lr_offset + bytes;
 582
 583             int j = i;
 584             if ( bytes < 0 ) {
 585                for ( j = i - 1; j >= 0; j-- ) {
 586                   if ( locations[j].lr_offset == target ) { break; }
 587                } /* end search backward */
 588             } else {
 589                for ( j = i + 1; j < dwlocs->ld_cents; j ++ ) {
 590                   if ( locations[j].lr_offset == target ) { break; }
 591                } /* end search forward */
 592             } /* end if positive offset */
 593
 594             /* Because i will be incremented the next time around the loop. */
 595             i = j - 1;
 596          } break;
 597
 598          case DW_OP_piece:
 599             /* For multi-part variables, which we don't handle. */
 600             //bperr ( "Warning: dyninst does not handle multi-part variables.\n" );
 601             break;
 602
 603          case DW_OP_nop:
 604             break;
 605
 606          default:
 607             dwarf_printf( "Unrecognized or non-static location opcode 0x%x, aborting.\n", locations[i].lr_atom );
 608             return false;
 609             break;
 610       } /* end operand switch */
 611    } /* end iteration over Dwarf_Loc entries. */
 612
 613    if (opStack.empty()) {
 614       dwarf_printf( "ignoring malformed location list (stack empty at end of list).\n" );
 615       return isLocSet;
 616    }
 617    dwarf_printf( "Dwarf expression returning %d\n", opStack.top() );
 618    end_result = opStack.top();
 619    return true;
 620 }
 621
 622 #endif