1 files changed, 258 insertions, 0 deletions
diff --git a/xpcom/build/LateWriteChecks.cpp b/xpcom/build/LateWriteChecks.cpp
new file mode 100644
index 000000000..69dbedc0f
--- /dev/null
+++ b/xpcom/build/LateWriteChecks.cpp
@@ -0,0 +1,258 @@
+/* -*- 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 "nsAppDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsPrintfCString.h"
+#include "mozilla/StackWalk.h"
+#include "plstr.h"
+#include "prio.h"
+
+#ifdef XP_WIN
+#define NS_T(str) L ## str
+#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"
+
+#define OBSERVE_LATE_WRITES
+
+using namespace mozilla;
+
+/*************************** Auxiliary Declarations ***************************/
+
+// 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_ASSERT(mFile);
+    va_list list;
+    va_start(list, aFormat);
+    nsAutoCString str;
+    str.AppendPrintf(aFormat, list);
+    va_end(list);
+    mSHA1.update(str.get(), str.Length());
+    fwrite(str.get(), 1, str.Length(), mFile);
+  }
+  void Finish(SHA1Sum::Hash& aHash)
+  {
+    int fd = fileno(mFile);
+    fflush(mFile);
+    MozillaUnRegisterDebugFD(fd);
+    fclose(mFile);
+    mSHA1.finish(aHash);
+    mFile = nullptr;
+  }
+private:
+  FILE* mFile;
+  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 IOInterposeObserver
+{
+public:
+  explicit LateWriteObserver(const char* aProfileDirectory)
+    : mProfileDirectory(PL_strdup(aProfileDirectory))
+  {
+  }
+  ~LateWriteObserver()
+  {
+    PL_strfree(mProfileDirectory);
+    mProfileDirectory = nullptr;
+  }
+
+  void Observe(IOInterposeObserver::Observation& aObservation);
+private:
+  char* mProfileDirectory;
+};
+
+void
+LateWriteObserver::Observe(IOInterposeObserver::Observation& aOb)
+{
+#ifdef OBSERVE_LATE_WRITES
+  // Crash if that is the shutdown check mode
+  if (gShutdownChecks == SCM_CRASH) {
+    MOZ_CRASH();
+  }
+
+  // If we have shutdown mode SCM_NOTHING or we can't record then abort
+  if (gShutdownChecks == SCM_NOTHING || !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, /* skipFrames */ 0, /* maxFrames */ 0,
+               reinterpret_cast<void*>(&rawStack), 0, nullptr);
+  Telemetry::ProcessedStack stack = Telemetry::GetStackAndModules(rawStack);
+
+  nsPrintfCString nameAux("%s%s%s", mProfileDirectory,
+                          NS_SLASH, "Telemetry.LateWriteTmpXXXXXX");
+  char* name;
+  nameAux.GetMutableData(&name);
+
+  // 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
+    int result = _mktemp_s(name, strlen(name) + 1);
+    hFile = CreateFileA(name, GENERIC_WRITE, 0, nullptr, CREATE_NEW,
+                        FILE_ATTRIBUTE_NORMAL, nullptr);
+  } while (GetLastError() == ERROR_FILE_EXISTS);
+
+  if (hFile == INVALID_HANDLE_VALUE) {
+    NS_RUNTIMEABORT("Um, how did we get here?");
+  }
+
+  // http://support.microsoft.com/kb/139640
+  int fd = _open_osfhandle((intptr_t)hFile, _O_APPEND);
+  if (fd == -1) {
+    NS_RUNTIMEABORT("Um, how did we get here?");
+  }
+
+  stream = _fdopen(fd, "w");
+#else
+  int fd = mkstemp(name);
+  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) {
+    Telemetry::ProcessedStack::Module module = stack.GetModule(i);
+    sha1Stream.Printf("%s %s\n", module.mBreakpadId.c_str(),
+                      module.mName.c_str());
+  }
+
+  size_t numFrames = stack.GetStackSize();
+  sha1Stream.Printf("%u\n", (unsigned)numFrames);
+  for (size_t i = 0; i < numFrames; ++i) {
+    const 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);
+  }
+
+  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.
+  nsPrintfCString finalName("%s%s", mProfileDirectory,
+                            "/Telemetry.LateWriteFinal-");
+  for (int i = 0; i < 20; ++i) {
+    finalName.AppendPrintf("%02x", sha1[i]);
+  }
+  PR_Delete(finalName.get());
+  PR_Rename(name, finalName.get());
+#endif
+}
+
+/******************************* Setup/Teardown *******************************/
+
+static StaticAutoPtr<LateWriteObserver> sLateWriteObserver;
+
+namespace mozilla {
+
+void
+InitLateWriteChecks()
+{
+  nsCOMPtr<nsIFile> mozFile;
+  NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR, getter_AddRefs(mozFile));
+  if (mozFile) {
+    nsAutoCString nativePath;
+    nsresult rv = mozFile->GetNativePath(nativePath);
+    if (NS_SUCCEEDED(rv) && 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;
+  }
+}
+
+} // namespace mozilla