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Diffstat (limited to 'xpcom/base/nsDumpUtils.cpp')
| -rw-r--r-- | xpcom/base/nsDumpUtils.cpp | 488 |
1 files changed, 488 insertions, 0 deletions
diff --git a/xpcom/base/nsDumpUtils.cpp b/xpcom/base/nsDumpUtils.cpp new file mode 100644 index 0000000000..c7bbbf4eb3 --- /dev/null +++ b/xpcom/base/nsDumpUtils.cpp @@ -0,0 +1,488 @@ +/* -*- 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 <errno.h> +#include "prenv.h" +#include "mozilla/Services.h" +#include "nsIObserverService.h" +#include "mozilla/ClearOnShutdown.h" +#include "mozilla/Unused.h" +#include "SpecialSystemDirectory.h" + +#ifdef XP_UNIX // { +# include "mozilla/Preferences.h" +# include <fcntl.h> +# include <unistd.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 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( + "FdWatcher::StartWatching", 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() = default; + +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("debug_info_trigger"_ns); + 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) { + if (NS_IsMainThread()) { + // This allows tests to override, but isn't safe off-mainthread. + rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, aFile); + } else { + rv = GetSpecialSystemDirectory(OS_TemporaryDirectory, 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.IsEmpty()) { + 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; +} |