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