DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (7f9f804e9dbe)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* API for getting a stack trace of the C/C++ stack on the current thread */

#include "mozilla/ArrayUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/IntegerPrintfMacros.h"
#include "mozilla/StackWalk.h"

#include <string.h>

#if defined(ANDROID) && defined(MOZ_LINKER)
#  include "Linker.h"
#  include <android/log.h>
#endif

using namespace mozilla;

// for _Unwind_Backtrace from libcxxrt or libunwind
// cxxabi.h from libcxxrt implicitly includes unwind.h first
#if defined(HAVE__UNWIND_BACKTRACE) && !defined(_GNU_SOURCE)
#  define _GNU_SOURCE
#endif

#if defined(HAVE_DLOPEN) || defined(XP_DARWIN)
#  include <dlfcn.h>
#endif

#if (defined(XP_DARWIN) && \
     (defined(__i386) || defined(__ppc__) || defined(HAVE__UNWIND_BACKTRACE)))
#  define MOZ_STACKWALK_SUPPORTS_MACOSX 1
#else
#  define MOZ_STACKWALK_SUPPORTS_MACOSX 0
#endif

#if (defined(linux) &&                                            \
     ((defined(__GNUC__) && (defined(__i386) || defined(PPC))) || \
      defined(HAVE__UNWIND_BACKTRACE)))
#  define MOZ_STACKWALK_SUPPORTS_LINUX 1
#else
#  define MOZ_STACKWALK_SUPPORTS_LINUX 0
#endif

#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1)
#  define HAVE___LIBC_STACK_END 1
#else
#  define HAVE___LIBC_STACK_END 0
#endif

#if HAVE___LIBC_STACK_END
extern MOZ_EXPORT void* __libc_stack_end;  // from ld-linux.so
#endif

#ifdef ANDROID
#  include <algorithm>
#  include <unistd.h>
#  include <pthread.h>
#endif

#if MOZ_STACKWALK_SUPPORTS_WINDOWS

#  include <windows.h>
#  include <process.h>
#  include <stdio.h>
#  include <malloc.h>
#  include "mozilla/ArrayUtils.h"
#  include "mozilla/Atomics.h"
#  include "mozilla/StackWalk_windows.h"
#  include "mozilla/WindowsVersion.h"

#  include <imagehlp.h>
// We need a way to know if we are building for WXP (or later), as if we are, we
// need to use the newer 64-bit APIs. API_VERSION_NUMBER seems to fit the bill.
// A value of 9 indicates we want to use the new APIs.
#  if API_VERSION_NUMBER < 9
#    error Too old imagehlp.h
#  endif

struct WalkStackData {
  // Are we walking the stack of the calling thread? Note that we need to avoid
  // calling fprintf and friends if this is false, in order to avoid deadlocks.
  bool walkCallingThread;
  uint32_t skipFrames;
  HANDLE thread;
  HANDLE process;
  HANDLE eventStart;
  HANDLE eventEnd;
  void** pcs;
  uint32_t pc_size;
  uint32_t pc_count;
  uint32_t pc_max;
  void** sps;
  uint32_t sp_size;
  uint32_t sp_count;
  CONTEXT* context;
};

CRITICAL_SECTION gDbgHelpCS;

#  if defined(_M_AMD64) || defined(_M_ARM64)
// Because various Win64 APIs acquire function-table locks, we need a way of
// preventing stack walking while those APIs are being called. Otherwise, the
// stack walker may suspend a thread holding such a lock, and deadlock when the
// stack unwind code attempts to wait for that lock.
//
// We're using an atomic counter rather than a critical section because we
// don't require mutual exclusion with the stack walker. If the stack walker
// determines that it's safe to start unwinding the suspended thread (i.e.
// there are no suppressions when the unwind begins), then it's safe to
// continue unwinding that thread even if other threads request suppressions
// in the meantime, because we can't deadlock with those other threads.
//
// XXX: This global variable is a larger-than-necessary hammer. A more scoped
// solution would be to maintain a counter per thread, but then it would be
// more difficult for WalkStackMain64 to read the suspended thread's counter.
static Atomic<size_t> sStackWalkSuppressions;

void SuppressStackWalking() { ++sStackWalkSuppressions; }

void DesuppressStackWalking() { --sStackWalkSuppressions; }

MFBT_API
AutoSuppressStackWalking::AutoSuppressStackWalking() { SuppressStackWalking(); }

MFBT_API
AutoSuppressStackWalking::~AutoSuppressStackWalking() {
  DesuppressStackWalking();
}

static uint8_t* sJitCodeRegionStart;
static size_t sJitCodeRegionSize;
uint8_t* sMsMpegJitCodeRegionStart;
size_t sMsMpegJitCodeRegionSize;

MFBT_API void RegisterJitCodeRegion(uint8_t* aStart, size_t aSize) {
  // Currently we can only handle one JIT code region at a time
  MOZ_RELEASE_ASSERT(!sJitCodeRegionStart);

  sJitCodeRegionStart = aStart;
  sJitCodeRegionSize = aSize;
}

MFBT_API void UnregisterJitCodeRegion(uint8_t* aStart, size_t aSize) {
  // Currently we can only handle one JIT code region at a time
  MOZ_RELEASE_ASSERT(sJitCodeRegionStart && sJitCodeRegionStart == aStart &&
                     sJitCodeRegionSize == aSize);

  sJitCodeRegionStart = nullptr;
  sJitCodeRegionSize = 0;
}

#  endif  // _M_AMD64 || _M_ARM64

// Routine to print an error message to standard error.
static void PrintError(const char* aPrefix) {
  LPSTR lpMsgBuf;
  DWORD lastErr = GetLastError();
  FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
                     FORMAT_MESSAGE_IGNORE_INSERTS,
                 nullptr, lastErr,
                 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),  // Default language
                 (LPSTR)&lpMsgBuf, 0, nullptr);
  fprintf(stderr, "### ERROR: %s: %s", aPrefix,
          lpMsgBuf ? lpMsgBuf : "(null)\n");
  fflush(stderr);
  LocalFree(lpMsgBuf);
}

static void InitializeDbgHelpCriticalSection() {
  static bool initialized = false;
  if (initialized) {
    return;
  }
  ::InitializeCriticalSection(&gDbgHelpCS);
  initialized = true;
}

static void WalkStackMain64(struct WalkStackData* aData) {
  // Get a context for the specified thread.
  CONTEXT context_buf;
  CONTEXT* context;
  if (!aData->context) {
    context = &context_buf;
    memset(context, 0, sizeof(CONTEXT));
    context->ContextFlags = CONTEXT_FULL;
    if (aData->walkCallingThread) {
      ::RtlCaptureContext(context);
    } else if (!GetThreadContext(aData->thread, context)) {
      return;
    }
  } else {
    context = aData->context;
  }

#  if defined(_M_IX86) || defined(_M_IA64)
  // Setup initial stack frame to walk from.
  STACKFRAME64 frame64;
  memset(&frame64, 0, sizeof(frame64));
#    ifdef _M_IX86
  frame64.AddrPC.Offset = context->Eip;
  frame64.AddrStack.Offset = context->Esp;
  frame64.AddrFrame.Offset = context->Ebp;
#    elif defined _M_IA64
  frame64.AddrPC.Offset = context->StIIP;
  frame64.AddrStack.Offset = context->SP;
  frame64.AddrFrame.Offset = context->RsBSP;
#    endif
  frame64.AddrPC.Mode = AddrModeFlat;
  frame64.AddrStack.Mode = AddrModeFlat;
  frame64.AddrFrame.Mode = AddrModeFlat;
  frame64.AddrReturn.Mode = AddrModeFlat;
#  endif

#  if defined(_M_AMD64) || defined(_M_ARM64)
  // If there are any active suppressions, then at least one thread (we don't
  // know which) is holding a lock that can deadlock RtlVirtualUnwind. Since
  // that thread may be the one that we're trying to unwind, we can't proceed.
  //
  // But if there are no suppressions, then our target thread can't be holding
  // a lock, and it's safe to proceed. By virtue of being suspended, the target
  // thread can't acquire any new locks during the unwind process, so we only
  // need to do this check once. After that, sStackWalkSuppressions can be
  // changed by other threads while we're unwinding, and that's fine because
  // we can't deadlock with those threads.
  if (sStackWalkSuppressions) {
    return;
  }
#  endif

#  if defined(_M_AMD64) || defined(_M_ARM64)
  bool firstFrame = true;
#  endif

  // Skip our own stack walking frames.
  int skip = (aData->walkCallingThread ? 3 : 0) + aData->skipFrames;

  // Now walk the stack.
  while (true) {
    DWORD64 addr;
    DWORD64 spaddr;

#  if defined(_M_IX86) || defined(_M_IA64)
    // 32-bit frame unwinding.
    // Debug routines are not threadsafe, so grab the lock.
    EnterCriticalSection(&gDbgHelpCS);
    BOOL ok = StackWalk64(
#    if defined _M_IA64
        IMAGE_FILE_MACHINE_IA64,
#    elif defined _M_IX86
        IMAGE_FILE_MACHINE_I386,
#    endif
        aData->process, aData->thread, &frame64, context, nullptr,
        SymFunctionTableAccess64,  // function table access routine
        SymGetModuleBase64,        // module base routine
        0);
    LeaveCriticalSection(&gDbgHelpCS);

    if (ok) {
      addr = frame64.AddrPC.Offset;
      spaddr = frame64.AddrStack.Offset;
    } else {
      addr = 0;
      spaddr = 0;
      if (aData->walkCallingThread) {
        PrintError("WalkStack64");
      }
    }

    if (!ok) {
      break;
    }

#  elif defined(_M_AMD64) || defined(_M_ARM64)

#    if defined(_M_AMD64)
    auto currentInstr = context->Rip;
#    elif defined(_M_ARM64)
    auto currentInstr = context->Pc;
#    endif

    // If we reach a frame in JIT code, we don't have enough information to
    // unwind, so we have to give up.
    if (sJitCodeRegionStart && (uint8_t*)currentInstr >= sJitCodeRegionStart &&
        (uint8_t*)currentInstr < sJitCodeRegionStart + sJitCodeRegionSize) {
      break;
    }

    // We must also avoid msmpeg2vdec.dll's JIT region: they don't generate
    // unwind data, so their JIT unwind callback just throws up its hands and
    // terminates the process.
    if (sMsMpegJitCodeRegionStart &&
        (uint8_t*)currentInstr >= sMsMpegJitCodeRegionStart &&
        (uint8_t*)currentInstr <
            sMsMpegJitCodeRegionStart + sMsMpegJitCodeRegionSize) {
      break;
    }

    // 64-bit frame unwinding.
    // Try to look up unwind metadata for the current function.
    ULONG64 imageBase;
    PRUNTIME_FUNCTION runtimeFunction =
        RtlLookupFunctionEntry(currentInstr, &imageBase, NULL);

    if (runtimeFunction) {
      PVOID dummyHandlerData;
      ULONG64 dummyEstablisherFrame;
      RtlVirtualUnwind(UNW_FLAG_NHANDLER, imageBase, currentInstr,
                       runtimeFunction, context, &dummyHandlerData,
                       &dummyEstablisherFrame, nullptr);
    } else if (firstFrame) {
      // Leaf functions can be unwound by hand.
#    if defined(_M_AMD64)
      context->Rip = *reinterpret_cast<DWORD64*>(context->Rsp);
      context->Rsp += sizeof(void*);
#    elif defined(_M_ARM64)
      context->Pc = *reinterpret_cast<DWORD64*>(context->Sp);
      context->Sp += sizeof(void*);
#    endif
    } else {
      // Something went wrong.
      break;
    }

#    if defined(_M_AMD64)
    addr = context->Rip;
    spaddr = context->Rsp;
#    elif defined(_M_ARM64)
    addr = context->Pc;
    spaddr = context->Sp;
#    endif
    firstFrame = false;
#  else
#    error "unknown platform"
#  endif

    if (addr == 0) {
      break;
    }

    if (skip-- > 0) {
      continue;
    }

    if (aData->pc_count < aData->pc_size) {
      aData->pcs[aData->pc_count] = (void*)addr;
    }
    ++aData->pc_count;

    if (aData->sp_count < aData->sp_size) {
      aData->sps[aData->sp_count] = (void*)spaddr;
    }
    ++aData->sp_count;

    if (aData->pc_max != 0 && aData->pc_count == aData->pc_max) {
      break;
    }

#  if defined(_M_IX86) || defined(_M_IA64)
    if (frame64.AddrReturn.Offset == 0) {
      break;
    }
#  endif
  }
}

/**
 * Walk the stack, translating PC's found into strings and recording the
 * chain in aBuffer. For this to work properly, the DLLs must be rebased
 * so that the address in the file agrees with the address in memory.
 * Otherwise StackWalk will return FALSE when it hits a frame in a DLL
 * whose in memory address doesn't match its in-file address.
 */

MFBT_API void MozStackWalkThread(MozWalkStackCallback aCallback,
                                 uint32_t aSkipFrames, uint32_t aMaxFrames,
                                 void* aClosure, HANDLE aThread,
                                 CONTEXT* aContext) {
  struct WalkStackData data;

  InitializeDbgHelpCriticalSection();

  HANDLE targetThread = aThread;
  if (!aThread) {
    targetThread = ::GetCurrentThread();
    data.walkCallingThread = true;
  } else {
    DWORD threadId = ::GetThreadId(aThread);
    DWORD currentThreadId = ::GetCurrentThreadId();
    data.walkCallingThread = (threadId == currentThreadId);
  }

  data.skipFrames = aSkipFrames;
  data.thread = targetThread;
  data.process = ::GetCurrentProcess();
  void* local_pcs[1024];
  data.pcs = local_pcs;
  data.pc_count = 0;
  data.pc_size = ArrayLength(local_pcs);
  data.pc_max = aMaxFrames;
  void* local_sps[1024];
  data.sps = local_sps;
  data.sp_count = 0;
  data.sp_size = ArrayLength(local_sps);
  data.context = aContext;

  WalkStackMain64(&data);

  if (data.pc_count > data.pc_size) {
    data.pcs = (void**)_alloca(data.pc_count * sizeof(void*));
    data.pc_size = data.pc_count;
    data.pc_count = 0;
    data.sps = (void**)_alloca(data.sp_count * sizeof(void*));
    data.sp_size = data.sp_count;
    data.sp_count = 0;
    WalkStackMain64(&data);
  }

  for (uint32_t i = 0; i < data.pc_count; ++i) {
    (*aCallback)(i + 1, data.pcs[i], data.sps[i], aClosure);
  }
}

MFBT_API void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {
  MozStackWalkThread(aCallback, aSkipFrames, aMaxFrames, aClosure, nullptr,
                     nullptr);
}

static BOOL CALLBACK callbackEspecial64(PCSTR aModuleName, DWORD64 aModuleBase,
                                        ULONG aModuleSize, PVOID aUserContext) {
  BOOL retval = TRUE;
  DWORD64 addr = *(DWORD64*)aUserContext;

  /*
   * You'll want to control this if we are running on an
   *  architecture where the addresses go the other direction.
   * Not sure this is even a realistic consideration.
   */
  const BOOL addressIncreases = TRUE;

  /*
   * If it falls in side the known range, load the symbols.
   */
  if (addressIncreases
          ? (addr >= aModuleBase && addr <= (aModuleBase + aModuleSize))
          : (addr <= aModuleBase && addr >= (aModuleBase - aModuleSize))) {
    retval = !!SymLoadModule64(GetCurrentProcess(), nullptr, (PSTR)aModuleName,
                               nullptr, aModuleBase, aModuleSize);
    if (!retval) {
      PrintError("SymLoadModule64");
    }
  }

  return retval;
}

/*
 * SymGetModuleInfoEspecial
 *
 * Attempt to determine the module information.
 * Bug 112196 says this DLL may not have been loaded at the time
 *  SymInitialize was called, and thus the module information
 *  and symbol information is not available.
 * This code rectifies that problem.
 */

// New members were added to IMAGEHLP_MODULE64 (that show up in the
// Platform SDK that ships with VC8, but not the Platform SDK that ships
// with VC7.1, i.e., between DbgHelp 6.0 and 6.1), but we don't need to
// use them, and it's useful to be able to function correctly with the
// older library.  (Stock Windows XP SP2 seems to ship with dbghelp.dll
// version 5.1.)  Since Platform SDK version need not correspond to
// compiler version, and the version number in debughlp.h was NOT bumped
// when these changes were made, ifdef based on a constant that was
// added between these versions.
#  ifdef SSRVOPT_SETCONTEXT
#    define NS_IMAGEHLP_MODULE64_SIZE                                        \
      (((offsetof(IMAGEHLP_MODULE64, LoadedPdbName) + sizeof(DWORD64) - 1) / \
        sizeof(DWORD64)) *                                                   \
       sizeof(DWORD64))
#  else
#    define NS_IMAGEHLP_MODULE64_SIZE sizeof(IMAGEHLP_MODULE64)
#  endif

BOOL SymGetModuleInfoEspecial64(HANDLE aProcess, DWORD64 aAddr,
                                PIMAGEHLP_MODULE64 aModuleInfo,
                                PIMAGEHLP_LINE64 aLineInfo) {
  BOOL retval = FALSE;

  /*
   * Init the vars if we have em.
   */
  aModuleInfo->SizeOfStruct = NS_IMAGEHLP_MODULE64_SIZE;
  if (aLineInfo) {
    aLineInfo->SizeOfStruct = sizeof(IMAGEHLP_LINE64);
  }

  /*
   * Give it a go.
   * It may already be loaded.
   */
  retval = SymGetModuleInfo64(aProcess, aAddr, aModuleInfo);
  if (retval == FALSE) {
    /*
     * Not loaded, here's the magic.
     * Go through all the modules.
     */
    // Need to cast to PENUMLOADED_MODULES_CALLBACK64 because the
    // constness of the first parameter of
    // PENUMLOADED_MODULES_CALLBACK64 varies over SDK versions (from
    // non-const to const over time).  See bug 391848 and bug
    // 415426.
    BOOL enumRes = EnumerateLoadedModules64(
        aProcess, (PENUMLOADED_MODULES_CALLBACK64)callbackEspecial64,
        (PVOID)&aAddr);
    if (enumRes != FALSE) {
      /*
       * One final go.
       * If it fails, then well, we have other problems.
       */
      retval = SymGetModuleInfo64(aProcess, aAddr, aModuleInfo);
    }
  }

  /*
   * If we got module info, we may attempt line info as well.
   * We will not report failure if this does not work.
   */
  if (retval != FALSE && aLineInfo) {
    DWORD displacement = 0;
    BOOL lineRes = FALSE;
    lineRes = SymGetLineFromAddr64(aProcess, aAddr, &displacement, aLineInfo);
    if (!lineRes) {
      // Clear out aLineInfo to indicate that it's not valid
      memset(aLineInfo, 0, sizeof(*aLineInfo));
    }
  }

  return retval;
}

static bool EnsureSymInitialized() {
  static bool gInitialized = false;
  bool retStat;

  if (gInitialized) {
    return gInitialized;
  }

  InitializeDbgHelpCriticalSection();

  SymSetOptions(SYMOPT_LOAD_LINES | SYMOPT_UNDNAME);
  retStat = SymInitialize(GetCurrentProcess(), nullptr, TRUE);
  if (!retStat) {
    PrintError("SymInitialize");
  }

  gInitialized = retStat;
  /* XXX At some point we need to arrange to call SymCleanup */

  return retStat;
}

MFBT_API bool MozDescribeCodeAddress(void* aPC,
                                     MozCodeAddressDetails* aDetails) {
  aDetails->library[0] = '\0';
  aDetails->loffset = 0;
  aDetails->filename[0] = '\0';
  aDetails->lineno = 0;
  aDetails->function[0] = '\0';
  aDetails->foffset = 0;

  if (!EnsureSymInitialized()) {
    return false;
  }

  HANDLE myProcess = ::GetCurrentProcess();
  BOOL ok;

  // debug routines are not threadsafe, so grab the lock.
  EnterCriticalSection(&gDbgHelpCS);

  //
  // Attempt to load module info before we attempt to resolve the symbol.
  // This just makes sure we get good info if available.
  //

  DWORD64 addr = (DWORD64)aPC;
  IMAGEHLP_MODULE64 modInfo;
  IMAGEHLP_LINE64 lineInfo;
  BOOL modInfoRes;
  modInfoRes = SymGetModuleInfoEspecial64(myProcess, addr, &modInfo, &lineInfo);

  if (modInfoRes) {
    strncpy(aDetails->library, modInfo.LoadedImageName,
            sizeof(aDetails->library));
    aDetails->library[mozilla::ArrayLength(aDetails->library) - 1] = '\0';
    aDetails->loffset = (char*)aPC - (char*)modInfo.BaseOfImage;

    if (lineInfo.FileName) {
      strncpy(aDetails->filename, lineInfo.FileName,
              sizeof(aDetails->filename));
      aDetails->filename[mozilla::ArrayLength(aDetails->filename) - 1] = '\0';
      aDetails->lineno = lineInfo.LineNumber;
    }
  }

  ULONG64 buffer[(sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR) +
                  sizeof(ULONG64) - 1) /
                 sizeof(ULONG64)];
  PSYMBOL_INFO pSymbol = (PSYMBOL_INFO)buffer;
  pSymbol->SizeOfStruct = sizeof(SYMBOL_INFO);
  pSymbol->MaxNameLen = MAX_SYM_NAME;

  DWORD64 displacement;
  ok = SymFromAddr(myProcess, addr, &displacement, pSymbol);

  if (ok) {
    strncpy(aDetails->function, pSymbol->Name, sizeof(aDetails->function));
    aDetails->function[mozilla::ArrayLength(aDetails->function) - 1] = '\0';
    aDetails->foffset = static_cast<ptrdiff_t>(displacement);
  }

  LeaveCriticalSection(&gDbgHelpCS);  // release our lock
  return true;
}

// i386 or PPC Linux stackwalking code
#elif HAVE_DLADDR &&                                           \
    (HAVE__UNWIND_BACKTRACE || MOZ_STACKWALK_SUPPORTS_LINUX || \
     MOZ_STACKWALK_SUPPORTS_MACOSX)

#  include <stdlib.h>
#  include <string.h>
#  include <stdio.h>

// On glibc 2.1, the Dl_info api defined in <dlfcn.h> is only exposed
// if __USE_GNU is defined.  I suppose its some kind of standards
// adherence thing.
//
#  if (__GLIBC_MINOR__ >= 1) && !defined(__USE_GNU)
#    define __USE_GNU
#  endif

// This thing is exported by libstdc++
// Yes, this is a gcc only hack
#  if defined(MOZ_DEMANGLE_SYMBOLS)
#    include <cxxabi.h>
#  endif  // MOZ_DEMANGLE_SYMBOLS

namespace mozilla {

void DemangleSymbol(const char* aSymbol, char* aBuffer, int aBufLen) {
  aBuffer[0] = '\0';

#  if defined(MOZ_DEMANGLE_SYMBOLS)
  /* See demangle.h in the gcc source for the voodoo */
  char* demangled = abi::__cxa_demangle(aSymbol, 0, 0, 0);

  if (demangled) {
    strncpy(aBuffer, demangled, aBufLen);
    aBuffer[aBufLen - 1] = '\0';
    free(demangled);
  }
#  endif  // MOZ_DEMANGLE_SYMBOLS
}

}  // namespace mozilla

// {x86, ppc} x {Linux, Mac} stackwalking code.
#  if ((defined(__i386) || defined(PPC) || defined(__ppc__)) && \
       (MOZ_STACKWALK_SUPPORTS_MACOSX || MOZ_STACKWALK_SUPPORTS_LINUX))

MFBT_API void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {
  // Get the frame pointer
  void** bp = (void**)__builtin_frame_address(0);

  void* stackEnd;
#    if HAVE___LIBC_STACK_END
  stackEnd = __libc_stack_end;
#    elif defined(XP_DARWIN)
  stackEnd = pthread_get_stackaddr_np(pthread_self());
#    elif defined(ANDROID)
  pthread_attr_t sattr;
  pthread_attr_init(&sattr);
  pthread_getattr_np(pthread_self(), &sattr);
  void* stackBase = stackEnd = nullptr;
  size_t stackSize = 0;
  if (gettid() != getpid()) {
    // bionic's pthread_attr_getstack doesn't tell the truth for the main
    // thread (see bug 846670). So don't use it for the main thread.
    if (!pthread_attr_getstack(&sattr, &stackBase, &stackSize)) {
      stackEnd = static_cast<char*>(stackBase) + stackSize;
    } else {
      stackEnd = nullptr;
    }
  }
  if (!stackEnd) {
    // So consider the current frame pointer + an arbitrary size of 8MB
    // (modulo overflow ; not really arbitrary as it's the default stack
    // size for the main thread) if pthread_attr_getstack failed for
    // some reason (or was skipped).
    static const uintptr_t kMaxStackSize = 8 * 1024 * 1024;
    uintptr_t maxStackStart = uintptr_t(-1) - kMaxStackSize;
    uintptr_t stackStart = std::max(maxStackStart, uintptr_t(bp));
    stackEnd = reinterpret_cast<void*>(stackStart + kMaxStackSize);
  }
#    else
#      error Unsupported configuration
#    endif
  FramePointerStackWalk(aCallback, aSkipFrames, aMaxFrames, aClosure, bp,
                        stackEnd);
}

#  elif defined(HAVE__UNWIND_BACKTRACE)

// libgcc_s.so symbols _Unwind_Backtrace@@GCC_3.3 and _Unwind_GetIP@@GCC_3.0
#    include <unwind.h>

struct unwind_info {
  MozWalkStackCallback callback;
  int skip;
  int maxFrames;
  int numFrames;
  void* closure;
};

static _Unwind_Reason_Code unwind_callback(struct _Unwind_Context* context,
                                           void* closure) {
  unwind_info* info = static_cast<unwind_info*>(closure);
  void* pc = reinterpret_cast<void*>(_Unwind_GetIP(context));
  // TODO Use something like '_Unwind_GetGR()' to get the stack pointer.
  if (--info->skip < 0) {
    info->numFrames++;
    (*info->callback)(info->numFrames, pc, nullptr, info->closure);
    if (info->maxFrames != 0 && info->numFrames == info->maxFrames) {
      // Again, any error code that stops the walk will do.
      return _URC_FOREIGN_EXCEPTION_CAUGHT;
    }
  }
  return _URC_NO_REASON;
}

MFBT_API void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {
  unwind_info info;
  info.callback = aCallback;
  info.skip = aSkipFrames + 1;
  info.maxFrames = aMaxFrames;
  info.numFrames = 0;
  info.closure = aClosure;

  // We ignore the return value from _Unwind_Backtrace. There are three main
  // reasons for this.
  // - On ARM/Android bionic's _Unwind_Backtrace usually (always?) returns
  //   _URC_FAILURE.  See
  //   https://bugzilla.mozilla.org/show_bug.cgi?id=717853#c110.
  // - If aMaxFrames != 0, we want to stop early, and the only way to do that
  //   is to make unwind_callback return something other than _URC_NO_REASON,
  //   which causes _Unwind_Backtrace to return a non-success code.
  // - MozStackWalk doesn't have a return value anyway.
  (void)_Unwind_Backtrace(unwind_callback, &info);
}

#  endif

bool MFBT_API MozDescribeCodeAddress(void* aPC,
                                     MozCodeAddressDetails* aDetails) {
  aDetails->library[0] = '\0';
  aDetails->loffset = 0;
  aDetails->filename[0] = '\0';
  aDetails->lineno = 0;
  aDetails->function[0] = '\0';
  aDetails->foffset = 0;

  Dl_info info;

#  if defined(ANDROID) && defined(MOZ_LINKER)
  int ok = __wrap_dladdr(aPC, &info);
#  else
  int ok = dladdr(aPC, &info);
#  endif

  if (!ok) {
    return true;
  }

  strncpy(aDetails->library, info.dli_fname, sizeof(aDetails->library));
  aDetails->library[mozilla::ArrayLength(aDetails->library) - 1] = '\0';
  aDetails->loffset = (char*)aPC - (char*)info.dli_fbase;

  const char* symbol = info.dli_sname;
  if (!symbol || symbol[0] == '\0') {
    return true;
  }

  DemangleSymbol(symbol, aDetails->function, sizeof(aDetails->function));

  if (aDetails->function[0] == '\0') {
    // Just use the mangled symbol if demangling failed.
    strncpy(aDetails->function, symbol, sizeof(aDetails->function));
    aDetails->function[mozilla::ArrayLength(aDetails->function) - 1] = '\0';
  }

  aDetails->foffset = (char*)aPC - (char*)info.dli_saddr;
  return true;
}

#else  // unsupported platform.

MFBT_API void MozStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure) {}

MFBT_API bool MozDescribeCodeAddress(void* aPC,
                                     MozCodeAddressDetails* aDetails) {
  aDetails->library[0] = '\0';
  aDetails->loffset = 0;
  aDetails->filename[0] = '\0';
  aDetails->lineno = 0;
  aDetails->function[0] = '\0';
  aDetails->foffset = 0;
  return false;
}

#endif

#if defined(XP_WIN) || defined(XP_MACOSX) || defined(XP_LINUX)
namespace mozilla {
MOZ_ASAN_BLACKLIST
void FramePointerStackWalk(MozWalkStackCallback aCallback, uint32_t aSkipFrames,
                           uint32_t aMaxFrames, void* aClosure, void** aBp,
                           void* aStackEnd) {
  // Stack walking code courtesy Kipp's "leaky".

  int32_t skip = aSkipFrames;
  uint32_t numFrames = 0;
  while (aBp) {
    void** next = (void**)*aBp;
    // aBp may not be a frame pointer on i386 if code was compiled with
    // -fomit-frame-pointer, so do some sanity checks.
    // (aBp should be a frame pointer on ppc(64) but checking anyway may help
    // a little if the stack has been corrupted.)
    // We don't need to check against the begining of the stack because
    // we can assume that aBp > sp
    if (next <= aBp || next >= aStackEnd || (uintptr_t(next) & 3)) {
      break;
    }
#  if (defined(__ppc__) && defined(XP_MACOSX)) || defined(__powerpc64__)
    // ppc mac or powerpc64 linux
    void* pc = *(aBp + 2);
    aBp += 3;
#  else  // i386 or powerpc32 linux
    void* pc = *(aBp + 1);
    aBp += 2;
#  endif
    if (--skip < 0) {
      // Assume that the SP points to the BP of the function
      // it called. We can't know the exact location of the SP
      // but this should be sufficient for our use the SP
      // to order elements on the stack.
      numFrames++;
      (*aCallback)(numFrames, pc, aBp, aClosure);
      if (aMaxFrames != 0 && numFrames == aMaxFrames) {
        break;
      }
    }
    aBp = next;
  }
}
}  // namespace mozilla

#else

namespace mozilla {
MFBT_API void FramePointerStackWalk(MozWalkStackCallback aCallback,
                                    uint32_t aSkipFrames, uint32_t aMaxFrames,
                                    void* aClosure, void** aBp,
                                    void* aStackEnd) {}
}  // namespace mozilla

#endif

MFBT_API void MozFormatCodeAddressDetails(
    char* aBuffer, uint32_t aBufferSize, uint32_t aFrameNumber, void* aPC,
    const MozCodeAddressDetails* aDetails) {
  MozFormatCodeAddress(aBuffer, aBufferSize, aFrameNumber, aPC,
                       aDetails->function, aDetails->library, aDetails->loffset,
                       aDetails->filename, aDetails->lineno);
}

MFBT_API void MozFormatCodeAddress(char* aBuffer, uint32_t aBufferSize,
                                   uint32_t aFrameNumber, const void* aPC,
                                   const char* aFunction, const char* aLibrary,
                                   ptrdiff_t aLOffset, const char* aFileName,
                                   uint32_t aLineNo) {
  const char* function = aFunction && aFunction[0] ? aFunction : "???";
  if (aFileName && aFileName[0]) {
    // We have a filename and (presumably) a line number. Use them.
    snprintf(aBuffer, aBufferSize, "#%02u: %s (%s:%u)", aFrameNumber, function,
             aFileName, aLineNo);
  } else if (aLibrary && aLibrary[0]) {
    // We have no filename, but we do have a library name. Use it and the
    // library offset, and print them in a way that scripts like
    // fix_{linux,macosx}_stacks.py can easily post-process.
    snprintf(aBuffer, aBufferSize, "#%02u: %s[%s +0x%" PRIxPTR "]",
             aFrameNumber, function, aLibrary,
             static_cast<uintptr_t>(aLOffset));
  } else {
    // We have nothing useful to go on. (The format string is split because
    // '??)' is a trigraph and causes a warning, sigh.)
    snprintf(aBuffer, aBufferSize,
             "#%02u: ??? (???:???"
             ")",
             aFrameNumber);
  }
}