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512 lines
14 KiB
C++
512 lines
14 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsDumpUtils.h"
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#include "nsDirectoryServiceDefs.h"
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#include "nsDirectoryServiceUtils.h"
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#include "prenv.h"
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#include <errno.h>
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#include "mozilla/Services.h"
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#include "nsIObserverService.h"
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#include "mozilla/ClearOnShutdown.h"
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#include "mozilla/unused.h"
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#ifdef XP_UNIX // {
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#include "mozilla/Preferences.h"
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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using namespace mozilla;
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/*
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* The following code supports triggering a registered callback upon
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* receiving a specific signal.
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*
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* Take about:memory for example, we register
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* 1. doGCCCDump for doMemoryReport
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* 2. doMemoryReport for sDumpAboutMemorySignum(SIGRTMIN)
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* and sDumpAboutMemoryAfterMMUSignum(SIGRTMIN+1).
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*
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* When we receive one of these signals, we write the signal number to a pipe.
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* The IO thread then notices that the pipe has been written to, and kicks off
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* the appropriate task on the main thread.
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*
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* This scheme is similar to using signalfd(), except it's portable and it
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* doesn't require the use of sigprocmask, which is problematic because it
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* masks signals received by child processes.
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*
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* In theory, we could use Chromium's MessageLoopForIO::CatchSignal() for this.
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* But that uses libevent, which does not handle the realtime signals (bug
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* 794074).
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*/
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// This is the write-end of a pipe that we use to notice when a
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// specific signal occurs.
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static Atomic<int> sDumpPipeWriteFd(-1);
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const char* const FifoWatcher::kPrefName =
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"memory_info_dumper.watch_fifo.enabled";
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static void
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DumpSignalHandler(int aSignum)
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{
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// This is a signal handler, so everything in here needs to be
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// async-signal-safe. Be careful!
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if (sDumpPipeWriteFd != -1) {
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uint8_t signum = static_cast<int>(aSignum);
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unused << write(sDumpPipeWriteFd, &signum, sizeof(signum));
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}
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}
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NS_IMPL_ISUPPORTS(FdWatcher, nsIObserver);
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void
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FdWatcher::Init()
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{
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MOZ_ASSERT(NS_IsMainThread());
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nsCOMPtr<nsIObserverService> os = services::GetObserverService();
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os->AddObserver(this, "xpcom-shutdown", /* ownsWeak = */ false);
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XRE_GetIOMessageLoop()->PostTask(
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FROM_HERE,
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NewRunnableMethod(this, &FdWatcher::StartWatching));
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}
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// Implementations may call this function multiple times if they ensure that
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// it's safe to call OpenFd() multiple times and they call StopWatching()
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// first.
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void
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FdWatcher::StartWatching()
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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MOZ_ASSERT(mFd == -1);
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mFd = OpenFd();
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if (mFd == -1) {
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LOG("FdWatcher: OpenFd failed.");
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return;
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}
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MessageLoopForIO::current()->WatchFileDescriptor(
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mFd, /* persistent = */ true,
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MessageLoopForIO::WATCH_READ,
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&mReadWatcher, this);
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}
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// Since implementations can call StartWatching() multiple times, they can of
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// course call StopWatching() multiple times.
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void
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FdWatcher::StopWatching()
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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mReadWatcher.StopWatchingFileDescriptor();
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if (mFd != -1) {
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close(mFd);
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mFd = -1;
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}
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}
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StaticRefPtr<SignalPipeWatcher> SignalPipeWatcher::sSingleton;
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/* static */ SignalPipeWatcher*
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SignalPipeWatcher::GetSingleton()
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{
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if (!sSingleton) {
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sSingleton = new SignalPipeWatcher();
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sSingleton->Init();
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ClearOnShutdown(&sSingleton);
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}
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return sSingleton;
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}
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void
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SignalPipeWatcher::RegisterCallback(uint8_t aSignal,
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PipeCallback aCallback)
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{
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MutexAutoLock lock(mSignalInfoLock);
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for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); ++i) {
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if (mSignalInfo[i].mSignal == aSignal) {
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LOG("Register Signal(%d) callback failed! (DUPLICATE)", aSignal);
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return;
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}
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}
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SignalInfo signalInfo = { aSignal, aCallback };
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mSignalInfo.AppendElement(signalInfo);
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RegisterSignalHandler(signalInfo.mSignal);
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}
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void
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SignalPipeWatcher::RegisterSignalHandler(uint8_t aSignal)
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{
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struct sigaction action;
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memset(&action, 0, sizeof(action));
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sigemptyset(&action.sa_mask);
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action.sa_handler = DumpSignalHandler;
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if (aSignal) {
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if (sigaction(aSignal, &action, nullptr)) {
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LOG("SignalPipeWatcher failed to register sig %d.", aSignal);
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}
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} else {
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MutexAutoLock lock(mSignalInfoLock);
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for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); i++) {
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if (sigaction(mSignalInfo[i].mSignal, &action, nullptr)) {
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LOG("SignalPipeWatcher failed to register signal(%d) "
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"dump signal handler.", mSignalInfo[i].mSignal);
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}
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}
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}
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}
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SignalPipeWatcher::~SignalPipeWatcher()
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{
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if (sDumpPipeWriteFd != -1) {
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StopWatching();
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}
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}
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int
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SignalPipeWatcher::OpenFd()
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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// Create a pipe. When we receive a signal in our signal handler, we'll
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// write the signum to the write-end of this pipe.
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int pipeFds[2];
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if (pipe(pipeFds)) {
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LOG("SignalPipeWatcher failed to create pipe.");
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return -1;
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}
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// Close this pipe on calls to exec().
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fcntl(pipeFds[0], F_SETFD, FD_CLOEXEC);
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fcntl(pipeFds[1], F_SETFD, FD_CLOEXEC);
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int readFd = pipeFds[0];
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sDumpPipeWriteFd = pipeFds[1];
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RegisterSignalHandler();
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return readFd;
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}
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void
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SignalPipeWatcher::StopWatching()
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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// Close sDumpPipeWriteFd /after/ setting the fd to -1.
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// Otherwise we have the (admittedly far-fetched) race where we
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//
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// 1) close sDumpPipeWriteFd
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// 2) open a new fd with the same number as sDumpPipeWriteFd
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// had.
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// 3) receive a signal, then write to the fd.
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int pipeWriteFd = sDumpPipeWriteFd.exchange(-1);
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close(pipeWriteFd);
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FdWatcher::StopWatching();
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}
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void
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SignalPipeWatcher::OnFileCanReadWithoutBlocking(int aFd)
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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uint8_t signum;
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ssize_t numReceived = read(aFd, &signum, sizeof(signum));
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if (numReceived != sizeof(signum)) {
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LOG("Error reading from buffer in "
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"SignalPipeWatcher::OnFileCanReadWithoutBlocking.");
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return;
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}
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{
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MutexAutoLock lock(mSignalInfoLock);
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for (SignalInfoArray::index_type i = 0; i < mSignalInfo.Length(); i++) {
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if (signum == mSignalInfo[i].mSignal) {
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mSignalInfo[i].mCallback(signum);
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return;
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}
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}
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}
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LOG("SignalPipeWatcher got unexpected signum.");
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}
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StaticRefPtr<FifoWatcher> FifoWatcher::sSingleton;
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/* static */ FifoWatcher*
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FifoWatcher::GetSingleton()
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{
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if (!sSingleton) {
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nsAutoCString dirPath;
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Preferences::GetCString(
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"memory_info_dumper.watch_fifo.directory", &dirPath);
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sSingleton = new FifoWatcher(dirPath);
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sSingleton->Init();
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ClearOnShutdown(&sSingleton);
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}
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return sSingleton;
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}
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/* static */ bool
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FifoWatcher::MaybeCreate()
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{
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MOZ_ASSERT(NS_IsMainThread());
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if (XRE_GetProcessType() != GeckoProcessType_Default) {
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// We want this to be main-process only, since two processes can't listen
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// to the same fifo.
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return false;
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}
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if (!Preferences::GetBool(kPrefName, false)) {
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LOG("Fifo watcher disabled via pref.");
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return false;
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}
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// The FifoWatcher is held alive by the observer service.
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if (!sSingleton) {
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GetSingleton();
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}
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return true;
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}
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void
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FifoWatcher::RegisterCallback(const nsCString& aCommand, FifoCallback aCallback)
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{
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MutexAutoLock lock(mFifoInfoLock);
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for (FifoInfoArray::index_type i = 0; i < mFifoInfo.Length(); ++i) {
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if (mFifoInfo[i].mCommand.Equals(aCommand)) {
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LOG("Register command(%s) callback failed! (DUPLICATE)", aCommand.get());
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return;
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}
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}
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FifoInfo aFifoInfo = { aCommand, aCallback };
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mFifoInfo.AppendElement(aFifoInfo);
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}
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FifoWatcher::~FifoWatcher()
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{
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}
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int
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FifoWatcher::OpenFd()
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{
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// If the memory_info_dumper.directory pref is specified, put the fifo
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// there. Otherwise, put it into the system's tmp directory.
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nsCOMPtr<nsIFile> file;
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nsresult rv;
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if (mDirPath.Length() > 0) {
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rv = XRE_GetFileFromPath(mDirPath.get(), getter_AddRefs(file));
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if (NS_FAILED(rv)) {
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LOG("FifoWatcher failed to open file \"%s\"", mDirPath.get());
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return -1;
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}
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} else {
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rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(file));
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return -1;
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}
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}
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rv = file->AppendNative(NS_LITERAL_CSTRING("debug_info_trigger"));
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return -1;
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}
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nsAutoCString path;
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rv = file->GetNativePath(path);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return -1;
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}
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// unlink might fail because the file doesn't exist, or for other reasons.
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// But we don't care it fails; any problems will be detected later, when we
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// try to mkfifo or open the file.
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if (unlink(path.get())) {
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LOG("FifoWatcher::OpenFifo unlink failed; errno=%d. "
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"Continuing despite error.", errno);
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}
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if (mkfifo(path.get(), 0766)) {
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LOG("FifoWatcher::OpenFifo mkfifo failed; errno=%d", errno);
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return -1;
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}
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#ifdef ANDROID
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// Android runs with a umask, so we need to chmod our fifo to make it
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// world-writable.
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chmod(path.get(), 0666);
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#endif
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int fd;
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do {
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// The fifo will block until someone else has written to it. In
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// particular, open() will block until someone else has opened it for
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// writing! We want open() to succeed and read() to block, so we open
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// with NONBLOCK and then fcntl that away.
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fd = open(path.get(), O_RDONLY | O_NONBLOCK);
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} while (fd == -1 && errno == EINTR);
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if (fd == -1) {
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LOG("FifoWatcher::OpenFifo open failed; errno=%d", errno);
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return -1;
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}
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// Make fd blocking now that we've opened it.
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if (fcntl(fd, F_SETFL, 0)) {
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close(fd);
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return -1;
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}
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return fd;
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}
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void
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FifoWatcher::OnFileCanReadWithoutBlocking(int aFd)
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{
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MOZ_ASSERT(XRE_GetIOMessageLoop() == MessageLoopForIO::current());
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char buf[1024];
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int nread;
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do {
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// sizeof(buf) - 1 to leave space for the null-terminator.
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nread = read(aFd, buf, sizeof(buf));
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} while (nread == -1 && errno == EINTR);
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if (nread == -1) {
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// We want to avoid getting into a situation where
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// OnFileCanReadWithoutBlocking is called in an infinite loop, so when
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// something goes wrong, stop watching the fifo altogether.
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LOG("FifoWatcher hit an error (%d) and is quitting.", errno);
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StopWatching();
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return;
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}
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if (nread == 0) {
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// If we get EOF, that means that the other side closed the fifo. We need
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// to close and re-open the fifo; if we don't,
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// OnFileCanWriteWithoutBlocking will be called in an infinite loop.
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LOG("FifoWatcher closing and re-opening fifo.");
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StopWatching();
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StartWatching();
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return;
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}
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nsAutoCString inputStr;
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inputStr.Append(buf, nread);
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// Trimming whitespace is important because if you do
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// |echo "foo" >> debug_info_trigger|,
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// it'll actually write "foo\n" to the fifo.
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inputStr.Trim("\b\t\r\n");
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{
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MutexAutoLock lock(mFifoInfoLock);
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for (FifoInfoArray::index_type i = 0; i < mFifoInfo.Length(); i++) {
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const nsCString commandStr = mFifoInfo[i].mCommand;
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if (inputStr == commandStr.get()) {
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mFifoInfo[i].mCallback(inputStr);
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return;
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}
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}
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}
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LOG("Got unexpected value from fifo; ignoring it.");
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}
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#endif // XP_UNIX }
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// In Android case, this function will open a file named aFilename under
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// /data/local/tmp/"aFoldername".
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// Otherwise, it will open a file named aFilename under "NS_OS_TEMP_DIR".
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/* static */ nsresult
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nsDumpUtils::OpenTempFile(const nsACString& aFilename, nsIFile** aFile,
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const nsACString& aFoldername)
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{
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#ifdef ANDROID
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// For Android, first try the downloads directory which is world-readable
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// rather than the temp directory which is not.
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if (!*aFile) {
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char* env = PR_GetEnv("DOWNLOADS_DIRECTORY");
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if (env) {
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NS_NewNativeLocalFile(nsCString(env), /* followLinks = */ true, aFile);
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}
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}
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#endif
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nsresult rv;
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if (!*aFile) {
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rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, aFile);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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}
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#ifdef ANDROID
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// /data/local/tmp is a true tmp directory; anyone can create a file there,
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// but only the user which created the file can remove it. We want non-root
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// users to be able to remove these files, so we write them into a
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// subdirectory of the temp directory and chmod 777 that directory.
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if (aFoldername != EmptyCString()) {
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rv = (*aFile)->AppendNative(aFoldername);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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// It's OK if this fails; that probably just means that the directory already
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// exists.
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(*aFile)->Create(nsIFile::DIRECTORY_TYPE, 0777);
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nsAutoCString dirPath;
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rv = (*aFile)->GetNativePath(dirPath);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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while (chmod(dirPath.get(), 0777) == -1 && errno == EINTR) {
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}
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}
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#endif
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nsCOMPtr<nsIFile> file(*aFile);
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rv = file->AppendNative(aFilename);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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rv = file->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0666);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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#ifdef ANDROID
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// Make this file world-read/writable; the permissions passed to the
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// CreateUnique call above are not sufficient on Android, which runs with a
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// umask.
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nsAutoCString path;
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rv = file->GetNativePath(path);
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if (NS_WARN_IF(NS_FAILED(rv))) {
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return rv;
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}
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while (chmod(path.get(), 0666) == -1 && errno == EINTR) {
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}
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#endif
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return NS_OK;
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}
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