Source code
Revision control
Copy as Markdown
Other Tools
/* -*- 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
#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_GetAsyncIOEventTarget()->Dispatch(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_GetAsyncIOEventTarget()->IsOnCurrentThread());
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_GetAsyncIOEventTarget()->IsOnCurrentThread());
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_GetAsyncIOEventTarget()->IsOnCurrentThread());
// 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_GetAsyncIOEventTarget()->IsOnCurrentThread());
// 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_GetAsyncIOEventTarget()->IsOnCurrentThread());
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_GetAsyncIOEventTarget()->IsOnCurrentThread());
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) {
if (char* env = PR_GetEnv("DOWNLOADS_DIRECTORY")) {
Unused << NS_WARN_IF(
NS_FAILED(NS_NewNativeLocalFile(nsCString(env), 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;
}