1 files changed, 263 insertions, 0 deletions
diff --git a/xpcom/build/LateWriteChecks.cpp b/xpcom/build/LateWriteChecks.cpp
new file mode 100644
index 0000000000..e3bf73d73c
--- /dev/null
+++ b/xpcom/build/LateWriteChecks.cpp
@@ -0,0 +1,263 @@
+/* -*- 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/. */
+
+#include <algorithm>
+
+#include "mozilla/IOInterposer.h"
+#include "mozilla/PoisonIOInterposer.h"
+#include "mozilla/ProcessedStack.h"
+#include "mozilla/SHA1.h"
+#include "mozilla/Scoped.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Unused.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsLocalFile.h"
+#include "nsPrintfCString.h"
+#include "mozilla/StackWalk.h"
+#include "prio.h"
+
+#ifdef XP_WIN
+#  define NS_SLASH "\\"
+#  include <fcntl.h>
+#  include <io.h>
+#  include <stdio.h>
+#  include <stdlib.h>
+#  include <sys/stat.h>
+#  include <windows.h>
+#else
+#  define NS_SLASH "/"
+#endif
+
+#include "LateWriteChecks.h"
+
+/*************************** Auxiliary Declarations ***************************/
+
+static MOZ_THREAD_LOCAL(int) tlsSuspendLateWriteChecks;
+
+bool SuspendingLateWriteChecksForCurrentThread() {
+  if (!tlsSuspendLateWriteChecks.init()) {
+    return true;
+  }
+  return tlsSuspendLateWriteChecks.get() > 0;
+}
+
+// This a wrapper over a file descriptor that provides a Printf method and
+// computes the sha1 of the data that passes through it.
+class SHA1Stream {
+ public:
+  explicit SHA1Stream(FILE* aStream) : mFile(aStream) {
+    MozillaRegisterDebugFILE(mFile);
+  }
+
+  void Printf(const char* aFormat, ...) MOZ_FORMAT_PRINTF(2, 3) {
+    MOZ_ASSERT(mFile);
+    va_list list;
+    va_start(list, aFormat);
+    nsAutoCString str;
+    str.AppendVprintf(aFormat, list);
+    va_end(list);
+    mSHA1.update(str.get(), str.Length());
+    mozilla::Unused << fwrite(str.get(), 1, str.Length(), mFile);
+  }
+  void Finish(mozilla::SHA1Sum::Hash& aHash) {
+    int fd = fileno(mFile);
+    fflush(mFile);
+    MozillaUnRegisterDebugFD(fd);
+    fclose(mFile);
+    mSHA1.finish(aHash);
+    mFile = nullptr;
+  }
+
+ private:
+  FILE* mFile;
+  mozilla::SHA1Sum mSHA1;
+};
+
+static void RecordStackWalker(uint32_t aFrameNumber, void* aPC, void* aSP,
+                              void* aClosure) {
+  std::vector<uintptr_t>* stack =
+      static_cast<std::vector<uintptr_t>*>(aClosure);
+  stack->push_back(reinterpret_cast<uintptr_t>(aPC));
+}
+
+/**************************** Late-Write Observer  ****************************/
+
+/**
+ * An implementation of IOInterposeObserver to be registered with IOInterposer.
+ * This observer logs all writes as late writes.
+ */
+class LateWriteObserver final : public mozilla::IOInterposeObserver {
+  using char_type = mozilla::filesystem::Path::value_type;
+
+ public:
+  explicit LateWriteObserver(const char_type* aProfileDirectory)
+      : mProfileDirectory(NS_xstrdup(aProfileDirectory)) {}
+  ~LateWriteObserver() {
+    free(mProfileDirectory);
+    mProfileDirectory = nullptr;
+  }
+
+  void Observe(
+      mozilla::IOInterposeObserver::Observation& aObservation) override;
+
+ private:
+  char_type* mProfileDirectory;
+};
+
+void LateWriteObserver::Observe(
+    mozilla::IOInterposeObserver::Observation& aOb) {
+  if (SuspendingLateWriteChecksForCurrentThread()) {
+    return;
+  }
+
+#ifdef DEBUG
+  MOZ_CRASH();
+#endif
+
+  // If we can't record then abort
+  if (!mozilla::Telemetry::CanRecordExtended()) {
+    return;
+  }
+
+  // Write the stack and loaded libraries to a file. We can get here
+  // concurrently from many writes, so we use multiple temporary files.
+  std::vector<uintptr_t> rawStack;
+
+  MozStackWalk(RecordStackWalker, nullptr, /* maxFrames */ 0, &rawStack);
+  mozilla::Telemetry::ProcessedStack stack =
+      mozilla::Telemetry::GetStackAndModules(rawStack);
+
+  nsTAutoString<char_type> nameAux(mProfileDirectory);
+  nameAux.AppendLiteral(NS_SLASH "Telemetry.LateWriteTmpXXXXXX");
+  char_type* name = nameAux.BeginWriting();
+
+  // We want the sha1 of the entire file, so please don't write to fd
+  // directly; use sha1Stream.
+  FILE* stream;
+#ifdef XP_WIN
+  HANDLE hFile;
+  do {
+    // mkstemp isn't supported so keep trying until we get a file
+    _wmktemp_s(char16ptr_t(name), NS_strlen(name) + 1);
+    hFile = CreateFileW(char16ptr_t(name), GENERIC_WRITE, 0, nullptr,
+                        CREATE_NEW, FILE_ATTRIBUTE_NORMAL, nullptr);
+  } while (GetLastError() == ERROR_FILE_EXISTS);
+
+  if (hFile == INVALID_HANDLE_VALUE) {
+    MOZ_CRASH("Um, how did we get here?");
+  }
+
+  // http://support.microsoft.com/kb/139640
+  int fd = _open_osfhandle((intptr_t)hFile, _O_APPEND);
+  if (fd == -1) {
+    MOZ_CRASH("Um, how did we get here?");
+  }
+
+  stream = _fdopen(fd, "w");
+#else
+  int fd = mkstemp(name);
+  if (fd == -1) {
+    MOZ_CRASH("mkstemp failed");
+  }
+  stream = fdopen(fd, "w");
+#endif
+
+  SHA1Stream sha1Stream(stream);
+
+  size_t numModules = stack.GetNumModules();
+  sha1Stream.Printf("%u\n", (unsigned)numModules);
+  for (size_t i = 0; i < numModules; ++i) {
+    mozilla::Telemetry::ProcessedStack::Module module = stack.GetModule(i);
+    sha1Stream.Printf("%s %s\n", module.mBreakpadId.get(),
+                      NS_ConvertUTF16toUTF8(module.mName).get());
+  }
+
+  size_t numFrames = stack.GetStackSize();
+  sha1Stream.Printf("%u\n", (unsigned)numFrames);
+  for (size_t i = 0; i < numFrames; ++i) {
+    const mozilla::Telemetry::ProcessedStack::Frame& frame = stack.GetFrame(i);
+    // NOTE: We write the offsets, while the atos tool expects a value with
+    // the virtual address added. For example, running otool -l on the the
+    // firefox binary shows
+    //      cmd LC_SEGMENT_64
+    //      cmdsize 632
+    //      segname __TEXT
+    //      vmaddr 0x0000000100000000
+    // so to print the line matching the offset 123 one has to run
+    // atos -o firefox 0x100000123.
+    sha1Stream.Printf("%d %x\n", frame.mModIndex, (unsigned)frame.mOffset);
+  }
+
+  mozilla::SHA1Sum::Hash sha1;
+  sha1Stream.Finish(sha1);
+
+  // Note: These files should be deleted by telemetry once it reads them. If
+  // there were no telemetry runs by the time we shut down, we just add files
+  // to the existing ones instead of replacing them. Given that each of these
+  // files is a bug to be fixed, that is probably the right thing to do.
+
+  // We append the sha1 of the contents to the file name. This provides a simple
+  // client side deduplication.
+  nsAutoString finalName(u"Telemetry.LateWriteFinal-"_ns);
+  for (int i = 0; i < 20; ++i) {
+    finalName.AppendPrintf("%02x", sha1[i]);
+  }
+  RefPtr<nsLocalFile> file = new nsLocalFile(nameAux);
+  file->RenameTo(nullptr, finalName);
+}
+
+/******************************* Setup/Teardown *******************************/
+
+static mozilla::StaticAutoPtr<LateWriteObserver> sLateWriteObserver;
+
+namespace mozilla {
+
+void InitLateWriteChecks() {
+  nsCOMPtr<nsIFile> mozFile;
+  NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR, getter_AddRefs(mozFile));
+  if (mozFile) {
+    PathString nativePath = mozFile->NativePath();
+    if (nativePath.get()) {
+      sLateWriteObserver = new LateWriteObserver(nativePath.get());
+    }
+  }
+}
+
+void BeginLateWriteChecks() {
+  if (sLateWriteObserver) {
+    IOInterposer::Register(IOInterposeObserver::OpWriteFSync,
+                           sLateWriteObserver);
+  }
+}
+
+void StopLateWriteChecks() {
+  if (sLateWriteObserver) {
+    IOInterposer::Unregister(IOInterposeObserver::OpAll, sLateWriteObserver);
+    // Deallocation would not be thread-safe, and StopLateWriteChecks() is
+    // called at shutdown and only in special cases.
+    // sLateWriteObserver = nullptr;
+  }
+}
+
+void PushSuspendLateWriteChecks() {
+  if (!tlsSuspendLateWriteChecks.init()) {
+    return;
+  }
+  tlsSuspendLateWriteChecks.set(tlsSuspendLateWriteChecks.get() + 1);
+}
+
+void PopSuspendLateWriteChecks() {
+  if (!tlsSuspendLateWriteChecks.init()) {
+    return;
+  }
+  int current = tlsSuspendLateWriteChecks.get();
+  MOZ_ASSERT(current > 0);
+  tlsSuspendLateWriteChecks.set(current - 1);
+}
+
+}  // namespace mozilla