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