xpcom/build/LateWriteChecks.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include <algorithm>
   8
   9 #include "mozilla/IOInterposer.h"
  10 #include "mozilla/PoisonIOInterposer.h"
  11 #include "mozilla/ProcessedStack.h"
  12 #include "mozilla/SHA1.h"
  13 #include "mozilla/Scoped.h"
  14 #include "mozilla/StaticPtr.h"
  15 #include "mozilla/Telemetry.h"
  16 #include "mozilla/Unused.h"
  17 #include "nsAppDirectoryServiceDefs.h"
  18 #include "nsDirectoryServiceUtils.h"
  19 #include "nsLocalFile.h"
  20 #include "nsPrintfCString.h"
  21 #include "mozilla/StackWalk.h"
  22 #include "prio.h"
  23
  24 #ifdef XP_WIN
  25 #  define NS_SLASH "\\"
  26 #  include <fcntl.h>
  27 #  include <io.h>
  28 #  include <stdio.h>
  29 #  include <stdlib.h>
  30 #  include <sys/stat.h>
  31 #  include <windows.h>
  32 #else
  33 #  define NS_SLASH "/"
  34 #endif
  35
  36 #include "LateWriteChecks.h"
  37
  38 /*************************** Auxiliary Declarations ***************************/
  39
  40 static MOZ_THREAD_LOCAL(int) tlsSuspendLateWriteChecks;
  41
  42 bool SuspendingLateWriteChecksForCurrentThread() {
  43   if (!tlsSuspendLateWriteChecks.init()) {
  44     return true;
  45   }
  46   return tlsSuspendLateWriteChecks.get() > 0;
  47 }
  48
  49 // This a wrapper over a file descriptor that provides a Printf method and
  50 // computes the sha1 of the data that passes through it.
  51 class SHA1Stream {
  52  public:
  53   explicit SHA1Stream(FILE* aStream) : mFile(aStream) {
  54     MozillaRegisterDebugFILE(mFile);
  55   }
  56
  57   void Printf(const char* aFormat, ...) MOZ_FORMAT_PRINTF(2, 3) {
  58     MOZ_ASSERT(mFile);
  59     va_list list;
  60     va_start(list, aFormat);
  61     nsAutoCString str;
  62     str.AppendVprintf(aFormat, list);
  63     va_end(list);
  64     mSHA1.update(str.get(), str.Length());
  65     mozilla::Unused << fwrite(str.get(), 1, str.Length(), mFile);
  66   }
  67   void Finish(mozilla::SHA1Sum::Hash& aHash) {
  68     int fd = fileno(mFile);
  69     fflush(mFile);
  70     MozillaUnRegisterDebugFD(fd);
  71     fclose(mFile);
  72     mSHA1.finish(aHash);
  73     mFile = nullptr;
  74   }
  75
  76  private:
  77   FILE* mFile;
  78   mozilla::SHA1Sum mSHA1;
  79 };
  80
  81 static void RecordStackWalker(uint32_t aFrameNumber, void* aPC, void* aSP,
  82                               void* aClosure) {
  83   std::vector<uintptr_t>* stack =
  84       static_cast<std::vector<uintptr_t>*>(aClosure);
  85   stack->push_back(reinterpret_cast<uintptr_t>(aPC));
  86 }
  87
  88 /**************************** Late-Write Observer  ****************************/
  89
  90 /**
  91  * An implementation of IOInterposeObserver to be registered with IOInterposer.
  92  * This observer logs all writes as late writes.
  93  */
  94 class LateWriteObserver final : public mozilla::IOInterposeObserver {
  95   using char_type = mozilla::filesystem::Path::value_type;
  96
  97  public:
  98   explicit LateWriteObserver(const char_type* aProfileDirectory)
  99       : mProfileDirectory(NS_xstrdup(aProfileDirectory)) {}
 100   ~LateWriteObserver() {
 101     free(mProfileDirectory);
 102     mProfileDirectory = nullptr;
 103   }
 104
 105   void Observe(
 106       mozilla::IOInterposeObserver::Observation& aObservation) override;
 107
 108  private:
 109   char_type* mProfileDirectory;
 110 };
 111
 112 void LateWriteObserver::Observe(
 113     mozilla::IOInterposeObserver::Observation& aOb) {
 114   if (SuspendingLateWriteChecksForCurrentThread()) {
 115     return;
 116   }
 117
 118 #ifdef DEBUG
 119   MOZ_CRASH();
 120 #endif
 121
 122   // If we can't record then abort
 123   if (!mozilla::Telemetry::CanRecordExtended()) {
 124     return;
 125   }
 126
 127   // Write the stack and loaded libraries to a file. We can get here
 128   // concurrently from many writes, so we use multiple temporary files.
 129   std::vector<uintptr_t> rawStack;
 130
 131   MozStackWalk(RecordStackWalker, nullptr, /* maxFrames */ 0, &rawStack);
 132   mozilla::Telemetry::ProcessedStack stack =
 133       mozilla::Telemetry::GetStackAndModules(rawStack);
 134
 135   nsTAutoString<char_type> nameAux(mProfileDirectory);
 136   nameAux.AppendLiteral(NS_SLASH "Telemetry.LateWriteTmpXXXXXX");
 137   char_type* name = nameAux.BeginWriting();
 138
 139   // We want the sha1 of the entire file, so please don't write to fd
 140   // directly; use sha1Stream.
 141   FILE* stream;
 142 #ifdef XP_WIN
 143   HANDLE hFile;
 144   do {
 145     // mkstemp isn't supported so keep trying until we get a file
 146     _wmktemp_s(char16ptr_t(name), NS_strlen(name) + 1);
 147     hFile = CreateFileW(char16ptr_t(name), GENERIC_WRITE, 0, nullptr,
 148                         CREATE_NEW, FILE_ATTRIBUTE_NORMAL, nullptr);
 149   } while (GetLastError() == ERROR_FILE_EXISTS);
 150
 151   if (hFile == INVALID_HANDLE_VALUE) {
 152     MOZ_CRASH("Um, how did we get here?");
 153   }
 154
 155   // http://support.microsoft.com/kb/139640
 156   int fd = _open_osfhandle((intptr_t)hFile, _O_APPEND);
 157   if (fd == -1) {
 158     MOZ_CRASH("Um, how did we get here?");
 159   }
 160
 161   stream = _fdopen(fd, "w");
 162 #else
 163   int fd = mkstemp(name);
 164   if (fd == -1) {
 165     MOZ_CRASH("mkstemp failed");
 166   }
 167   stream = fdopen(fd, "w");
 168 #endif
 169
 170   SHA1Stream sha1Stream(stream);
 171
 172   size_t numModules = stack.GetNumModules();
 173   sha1Stream.Printf("%u\n", (unsigned)numModules);
 174   for (size_t i = 0; i < numModules; ++i) {
 175     mozilla::Telemetry::ProcessedStack::Module module = stack.GetModule(i);
 176     sha1Stream.Printf("%s %s\n", module.mBreakpadId.get(),
 177                       NS_ConvertUTF16toUTF8(module.mName).get());
 178   }
 179
 180   size_t numFrames = stack.GetStackSize();
 181   sha1Stream.Printf("%u\n", (unsigned)numFrames);
 182   for (size_t i = 0; i < numFrames; ++i) {
 183     const mozilla::Telemetry::ProcessedStack::Frame& frame = stack.GetFrame(i);
 184     // NOTE: We write the offsets, while the atos tool expects a value with
 185     // the virtual address added. For example, running otool -l on the the
 186     // firefox binary shows
 187     //      cmd LC_SEGMENT_64
 188     //      cmdsize 632
 189     //      segname __TEXT
 190     //      vmaddr 0x0000000100000000
 191     // so to print the line matching the offset 123 one has to run
 192     // atos -o firefox 0x100000123.
 193     sha1Stream.Printf("%d %x\n", frame.mModIndex, (unsigned)frame.mOffset);
 194   }
 195
 196   mozilla::SHA1Sum::Hash sha1;
 197   sha1Stream.Finish(sha1);
 198
 199   // Note: These files should be deleted by telemetry once it reads them. If
 200   // there were no telemetry runs by the time we shut down, we just add files
 201   // to the existing ones instead of replacing them. Given that each of these
 202   // files is a bug to be fixed, that is probably the right thing to do.
 203
 204   // We append the sha1 of the contents to the file name. This provides a simple
 205   // client side deduplication.
 206   nsAutoString finalName(u"Telemetry.LateWriteFinal-"_ns);
 207   for (int i = 0; i < 20; ++i) {
 208     finalName.AppendPrintf("%02x", sha1[i]);
 209   }
 210   RefPtr<nsLocalFile> file = new nsLocalFile(nameAux);
 211   file->RenameTo(nullptr, finalName);
 212 }
 213
 214 /******************************* Setup/Teardown *******************************/
 215
 216 static mozilla::StaticAutoPtr<LateWriteObserver> sLateWriteObserver;
 217
 218 namespace mozilla {
 219
 220 void InitLateWriteChecks() {
 221   nsCOMPtr<nsIFile> mozFile;
 222   NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR, getter_AddRefs(mozFile));
 223   if (mozFile) {
 224     PathString nativePath = mozFile->NativePath();
 225     if (nativePath.get()) {
 226       sLateWriteObserver = new LateWriteObserver(nativePath.get());
 227     }
 228   }
 229 }
 230
 231 void BeginLateWriteChecks() {
 232   if (sLateWriteObserver) {
 233     IOInterposer::Register(IOInterposeObserver::OpWriteFSync,
 234                            sLateWriteObserver);
 235   }
 236 }
 237
 238 void StopLateWriteChecks() {
 239   if (sLateWriteObserver) {
 240     IOInterposer::Unregister(IOInterposeObserver::OpAll, sLateWriteObserver);
 241     // Deallocation would not be thread-safe, and StopLateWriteChecks() is
 242     // called at shutdown and only in special cases.
 243     // sLateWriteObserver = nullptr;
 244   }
 245 }
 246
 247 void PushSuspendLateWriteChecks() {
 248   if (!tlsSuspendLateWriteChecks.init()) {
 249     return;
 250   }
 251   tlsSuspendLateWriteChecks.set(tlsSuspendLateWriteChecks.get() + 1);
 252 }
 253
 254 void PopSuspendLateWriteChecks() {
 255   if (!tlsSuspendLateWriteChecks.init()) {
 256     return;
 257   }
 258   int current = tlsSuspendLateWriteChecks.get();
 259   MOZ_ASSERT(current > 0);
 260   tlsSuspendLateWriteChecks.set(current - 1);
 261 }
 262
 263 }  // namespace mozilla