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-rw-r--r--xpcom/base/nsDumpUtils.cpp513
1 files changed, 513 insertions, 0 deletions
diff --git a/xpcom/base/nsDumpUtils.cpp b/xpcom/base/nsDumpUtils.cpp
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+++ b/xpcom/base/nsDumpUtils.cpp
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+/* -*- 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 "nsDumpUtils.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "prenv.h"
+#include <errno.h>
+#include "mozilla/Services.h"
+#include "nsIObserverService.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Unused.h"
+
+#ifdef XP_UNIX // {
+#include "mozilla/Preferences.h"
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+using namespace mozilla;
+
+/*
+ * The following code supports triggering a registered callback upon
+ * receiving a specific signal.
+ *
+ * Take about:memory for example, we register
+ * 1. doGCCCDump for doMemoryReport
+ * 2. doMemoryReport for sDumpAboutMemorySignum(SIGRTMIN)
+ * and sDumpAboutMemoryAfterMMUSignum(SIGRTMIN+1).
+ *
+ * When we receive one of these signals, we write the signal number to a pipe.
+ * The IO thread then notices that the pipe has been written to, and kicks off
+ * the appropriate task on the main thread.
+ *
+ * This scheme is similar to using signalfd(), except it's portable and it
+ * doesn't require the use of sigprocmask, which is problematic because it
+ * masks signals received by child processes.
+ *
+ * In theory, we could use Chromium's MessageLoopForIO::CatchSignal() for this.
+ * But that uses libevent, which does not handle the realtime signals (bug
+ * 794074).
+ */
+
+// This is the write-end of a pipe that we use to notice when a
+// specific signal occurs.
+static Atomic<int> sDumpPipeWriteFd(-1);
+
+const char* const FifoWatcher::kPrefName =
+ "memory_info_dumper.watch_fifo.enabled";
+
+static void
+DumpSignalHandler(int aSignum)
+{
+ // This is a signal handler, so everything in here needs to be
+ // async-signal-safe. Be careful!
+
+ if (sDumpPipeWriteFd != -1) {
+ uint8_t signum = static_cast<int>(aSignum);
+ Unused << write(sDumpPipeWriteFd, &signum, sizeof(signum));
+ }
+}
+
+NS_IMPL_ISUPPORTS(FdWatcher, nsIObserver);
+
+void
+FdWatcher::Init()
+{
+ MOZ_ASSERT(NS_IsMainThread());
+
+ nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+ os->AddObserver(this, "xpcom-shutdown", /* ownsWeak = */ false);
+
+ XRE_GetIOMessageLoop()->PostTask(NewRunnableMethod(this, &FdWatcher::StartWatching));
+}
+
+// Implementations may call this function multiple times if they ensure that
+// it's safe to call OpenFd() multiple times and they call StopWatching()
+// first.
+void
+FdWatcher::StartWatching()
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+ MOZ_ASSERT(mFd == -1);
+
+ mFd = OpenFd();
+ if (mFd == -1) {
+ LOG("FdWatcher: OpenFd failed.");
+ return;
+ }
+
+ MessageLoopForIO::current()->WatchFileDescriptor(
+ mFd, /* persistent = */ true,
+ MessageLoopForIO::WATCH_READ,
+ &mReadWatcher, this);
+}
+
+// Since implementations can call StartWatching() multiple times, they can of
+// course call StopWatching() multiple times.
+void
+FdWatcher::StopWatching()
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+
+ mReadWatcher.StopWatchingFileDescriptor();
+ if (mFd != -1) {
+ close(mFd);
+ mFd = -1;
+ }
+}
+
+StaticRefPtr<SignalPipeWatcher> SignalPipeWatcher::sSingleton;
+
+/* static */ SignalPipeWatcher*
+SignalPipeWatcher::GetSingleton()
+{
+ if (!sSingleton) {
+ sSingleton = new SignalPipeWatcher();
+ sSingleton->Init();
+ ClearOnShutdown(&sSingleton);
+ }
+ return sSingleton;
+}
+
+void
+SignalPipeWatcher::RegisterCallback(uint8_t aSignal,
+ PipeCallback aCallback)
+{
+ MutexAutoLock lock(mSignalInfoLock);
+
+ for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); ++i) {
+ if (mSignalInfo[i].mSignal == aSignal) {
+ LOG("Register Signal(%d) callback failed! (DUPLICATE)", aSignal);
+ return;
+ }
+ }
+ SignalInfo signalInfo = { aSignal, aCallback };
+ mSignalInfo.AppendElement(signalInfo);
+ RegisterSignalHandler(signalInfo.mSignal);
+}
+
+void
+SignalPipeWatcher::RegisterSignalHandler(uint8_t aSignal)
+{
+ struct sigaction action;
+ memset(&action, 0, sizeof(action));
+ sigemptyset(&action.sa_mask);
+ action.sa_handler = DumpSignalHandler;
+
+ if (aSignal) {
+ if (sigaction(aSignal, &action, nullptr)) {
+ LOG("SignalPipeWatcher failed to register sig %d.", aSignal);
+ }
+ } else {
+ MutexAutoLock lock(mSignalInfoLock);
+ for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); i++) {
+ if (sigaction(mSignalInfo[i].mSignal, &action, nullptr)) {
+ LOG("SignalPipeWatcher failed to register signal(%d) "
+ "dump signal handler.", mSignalInfo[i].mSignal);
+ }
+ }
+ }
+}
+
+SignalPipeWatcher::~SignalPipeWatcher()
+{
+ if (sDumpPipeWriteFd != -1) {
+ StopWatching();
+ }
+}
+
+int
+SignalPipeWatcher::OpenFd()
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+
+ // Create a pipe. When we receive a signal in our signal handler, we'll
+ // write the signum to the write-end of this pipe.
+ int pipeFds[2];
+ if (pipe(pipeFds)) {
+ LOG("SignalPipeWatcher failed to create pipe.");
+ return -1;
+ }
+
+ // Close this pipe on calls to exec().
+ fcntl(pipeFds[0], F_SETFD, FD_CLOEXEC);
+ fcntl(pipeFds[1], F_SETFD, FD_CLOEXEC);
+
+ int readFd = pipeFds[0];
+ sDumpPipeWriteFd = pipeFds[1];
+
+ RegisterSignalHandler();
+ return readFd;
+}
+
+void
+SignalPipeWatcher::StopWatching()
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+
+ // Close sDumpPipeWriteFd /after/ setting the fd to -1.
+ // Otherwise we have the (admittedly far-fetched) race where we
+ //
+ // 1) close sDumpPipeWriteFd
+ // 2) open a new fd with the same number as sDumpPipeWriteFd
+ // had.
+ // 3) receive a signal, then write to the fd.
+ int pipeWriteFd = sDumpPipeWriteFd.exchange(-1);
+ close(pipeWriteFd);
+
+ FdWatcher::StopWatching();
+}
+
+void
+SignalPipeWatcher::OnFileCanReadWithoutBlocking(int aFd)
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+
+ uint8_t signum;
+ ssize_t numReceived = read(aFd, &signum, sizeof(signum));
+ if (numReceived != sizeof(signum)) {
+ LOG("Error reading from buffer in "
+ "SignalPipeWatcher::OnFileCanReadWithoutBlocking.");
+ return;
+ }
+
+ {
+ MutexAutoLock lock(mSignalInfoLock);
+ for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); i++) {
+ if (signum == mSignalInfo[i].mSignal) {
+ mSignalInfo[i].mCallback(signum);
+ return;
+ }
+ }
+ }
+ LOG("SignalPipeWatcher got unexpected signum.");
+}
+
+StaticRefPtr<FifoWatcher> FifoWatcher::sSingleton;
+
+/* static */ FifoWatcher*
+FifoWatcher::GetSingleton()
+{
+ if (!sSingleton) {
+ nsAutoCString dirPath;
+ Preferences::GetCString(
+ "memory_info_dumper.watch_fifo.directory", &dirPath);
+ sSingleton = new FifoWatcher(dirPath);
+ sSingleton->Init();
+ ClearOnShutdown(&sSingleton);
+ }
+ return sSingleton;
+}
+
+/* static */ bool
+FifoWatcher::MaybeCreate()
+{
+ MOZ_ASSERT(NS_IsMainThread());
+
+ if (!XRE_IsParentProcess()) {
+ // We want this to be main-process only, since two processes can't listen
+ // to the same fifo.
+ return false;
+ }
+
+ if (!Preferences::GetBool(kPrefName, false)) {
+ LOG("Fifo watcher disabled via pref.");
+ return false;
+ }
+
+ // The FifoWatcher is held alive by the observer service.
+ if (!sSingleton) {
+ GetSingleton();
+ }
+ return true;
+}
+
+void
+FifoWatcher::RegisterCallback(const nsCString& aCommand, FifoCallback aCallback)
+{
+ MutexAutoLock lock(mFifoInfoLock);
+
+ for (FifoInfoArray::index_type i = 0; i < mFifoInfo.Length(); ++i) {
+ if (mFifoInfo[i].mCommand.Equals(aCommand)) {
+ LOG("Register command(%s) callback failed! (DUPLICATE)", aCommand.get());
+ return;
+ }
+ }
+ FifoInfo aFifoInfo = { aCommand, aCallback };
+ mFifoInfo.AppendElement(aFifoInfo);
+}
+
+FifoWatcher::~FifoWatcher()
+{
+}
+
+int
+FifoWatcher::OpenFd()
+{
+ // If the memory_info_dumper.directory pref is specified, put the fifo
+ // there. Otherwise, put it into the system's tmp directory.
+
+ nsCOMPtr<nsIFile> file;
+
+ nsresult rv;
+ if (mDirPath.Length() > 0) {
+ rv = XRE_GetFileFromPath(mDirPath.get(), getter_AddRefs(file));
+ if (NS_FAILED(rv)) {
+ LOG("FifoWatcher failed to open file \"%s\"", mDirPath.get());
+ return -1;
+ }
+ } else {
+ rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(file));
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return -1;
+ }
+ }
+
+ rv = file->AppendNative(NS_LITERAL_CSTRING("debug_info_trigger"));
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return -1;
+ }
+
+ nsAutoCString path;
+ rv = file->GetNativePath(path);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return -1;
+ }
+
+ // unlink might fail because the file doesn't exist, or for other reasons.
+ // But we don't care it fails; any problems will be detected later, when we
+ // try to mkfifo or open the file.
+ if (unlink(path.get())) {
+ LOG("FifoWatcher::OpenFifo unlink failed; errno=%d. "
+ "Continuing despite error.", errno);
+ }
+
+ if (mkfifo(path.get(), 0766)) {
+ LOG("FifoWatcher::OpenFifo mkfifo failed; errno=%d", errno);
+ return -1;
+ }
+
+#ifdef ANDROID
+ // Android runs with a umask, so we need to chmod our fifo to make it
+ // world-writable.
+ chmod(path.get(), 0666);
+#endif
+
+ int fd;
+ do {
+ // The fifo will block until someone else has written to it. In
+ // particular, open() will block until someone else has opened it for
+ // writing! We want open() to succeed and read() to block, so we open
+ // with NONBLOCK and then fcntl that away.
+ fd = open(path.get(), O_RDONLY | O_NONBLOCK);
+ } while (fd == -1 && errno == EINTR);
+
+ if (fd == -1) {
+ LOG("FifoWatcher::OpenFifo open failed; errno=%d", errno);
+ return -1;
+ }
+
+ // Make fd blocking now that we've opened it.
+ if (fcntl(fd, F_SETFL, 0)) {
+ close(fd);
+ return -1;
+ }
+
+ return fd;
+}
+
+void
+FifoWatcher::OnFileCanReadWithoutBlocking(int aFd)
+{
+ MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
+
+ char buf[1024];
+ int nread;
+ do {
+ // sizeof(buf) - 1 to leave space for the null-terminator.
+ nread = read(aFd, buf, sizeof(buf));
+ } while (nread == -1 && errno == EINTR);
+
+ if (nread == -1) {
+ // We want to avoid getting into a situation where
+ // OnFileCanReadWithoutBlocking is called in an infinite loop, so when
+ // something goes wrong, stop watching the fifo altogether.
+ LOG("FifoWatcher hit an error (%d) and is quitting.", errno);
+ StopWatching();
+ return;
+ }
+
+ if (nread == 0) {
+ // If we get EOF, that means that the other side closed the fifo. We need
+ // to close and re-open the fifo; if we don't,
+ // OnFileCanWriteWithoutBlocking will be called in an infinite loop.
+
+ LOG("FifoWatcher closing and re-opening fifo.");
+ StopWatching();
+ StartWatching();
+ return;
+ }
+
+ nsAutoCString inputStr;
+ inputStr.Append(buf, nread);
+
+ // Trimming whitespace is important because if you do
+ // |echo "foo" >> debug_info_trigger|,
+ // it'll actually write "foo\n" to the fifo.
+ inputStr.Trim("\b\t\r\n");
+
+ {
+ MutexAutoLock lock(mFifoInfoLock);
+
+ for (FifoInfoArray::index_type i = 0; i < mFifoInfo.Length(); i++) {
+ const nsCString commandStr = mFifoInfo[i].mCommand;
+ if (inputStr == commandStr.get()) {
+ mFifoInfo[i].mCallback(inputStr);
+ return;
+ }
+ }
+ }
+ LOG("Got unexpected value from fifo; ignoring it.");
+}
+
+#endif // XP_UNIX }
+
+// In Android case, this function will open a file named aFilename under
+// /data/local/tmp/"aFoldername".
+// Otherwise, it will open a file named aFilename under "NS_OS_TEMP_DIR".
+/* static */ nsresult
+nsDumpUtils::OpenTempFile(const nsACString& aFilename, nsIFile** aFile,
+ const nsACString& aFoldername, Mode aMode)
+{
+#ifdef ANDROID
+ // For Android, first try the downloads directory which is world-readable
+ // rather than the temp directory which is not.
+ if (!*aFile) {
+ char* env = PR_GetEnv("DOWNLOADS_DIRECTORY");
+ if (env) {
+ NS_NewNativeLocalFile(nsCString(env), /* followLinks = */ true, aFile);
+ }
+ }
+#endif
+ nsresult rv;
+ if (!*aFile) {
+ rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, aFile);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+ }
+
+#ifdef ANDROID
+ // /data/local/tmp is a true tmp directory; anyone can create a file there,
+ // but only the user which created the file can remove it. We want non-root
+ // users to be able to remove these files, so we write them into a
+ // subdirectory of the temp directory and chmod 777 that directory.
+ if (aFoldername != EmptyCString()) {
+ rv = (*aFile)->AppendNative(aFoldername);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+ // It's OK if this fails; that probably just means that the directory
+ // already exists.
+ Unused << (*aFile)->Create(nsIFile::DIRECTORY_TYPE, 0777);
+
+ nsAutoCString dirPath;
+ rv = (*aFile)->GetNativePath(dirPath);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+ while (chmod(dirPath.get(), 0777) == -1 && errno == EINTR) {
+ }
+ }
+#endif
+
+ nsCOMPtr<nsIFile> file(*aFile);
+
+ rv = file->AppendNative(aFilename);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+ if (aMode == CREATE_UNIQUE) {
+ rv = file->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0666);
+ } else {
+ rv = file->Create(nsIFile::NORMAL_FILE_TYPE, 0666);
+ }
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+#ifdef ANDROID
+ // Make this file world-read/writable; the permissions passed to the
+ // CreateUnique call above are not sufficient on Android, which runs with a
+ // umask.
+ nsAutoCString path;
+ rv = file->GetNativePath(path);
+ if (NS_WARN_IF(NS_FAILED(rv))) {
+ return rv;
+ }
+
+ while (chmod(path.get(), 0666) == -1 && errno == EINTR) {
+ }
+#endif
+
+ return NS_OK;
+}
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