// Copyright (c) 2016 GitHub, Inc.

// Use of this source code is governed by the MIT license that can be

// found in the LICENSE file.

#include "shell/browser/relauncher.h"

#include <fcntl.h>

#include <signal.h>

#include <sys/prctl.h>

#include <sys/signalfd.h>

#include "base/files/file_util.h"

#include "base/files/scoped_file.h"

#include "base/logging.h"

#include "base/process/launch.h"

#include "base/synchronization/waitable_event.h"

namespace relauncher {

namespace internal {

// this is global to be visible to the sa_handler

base::WaitableEvent parentWaiter;

void RelauncherSynchronizeWithParent() {

base::ScopedFD relauncher_sync_fd(kRelauncherSyncFD);

static const auto signum = SIGUSR2;

// send signum to current process when parent process ends.

if (HANDLE_EINTR(prctl(PR_SET_PDEATHSIG, signum)) != 0) {

PLOG(ERROR) << "prctl";

return;

}

// set up a signum handler

struct sigaction action;

memset(&action, 0, sizeof(action));

action.sa_handler = [](int /*signum*/) { parentWaiter.Signal(); };

if (sigaction(signum, &action, nullptr) != 0) {

PLOG(ERROR) << "sigaction";

return;

}

// write a '\0' character to the pipe to the parent process.

// this is how the parent knows that we're ready for it to exit.

if (HANDLE_EINTR(write(relauncher_sync_fd.get(), "", 1)) != 1) {

PLOG(ERROR) << "write";

return;

}

// Wait for the parent to exit

parentWaiter.Wait();

}

int LaunchProgram(const StringVector& relauncher_args,

const StringVector& argv) {

// Redirect the stdout of child process to /dev/null, otherwise after

// relaunch the child process will raise exception when writing to stdout.

base::ScopedFD devnull(HANDLE_EINTR(open("/dev/null", O_WRONLY)));

base::LaunchOptions options;

options.allow_new_privs = true;

options.new_process_group = true; // detach

options.fds_to_remap.push_back(std::make_pair(devnull.get(), STDERR_FILENO));

options.fds_to_remap.push_back(std::make_pair(devnull.get(), STDOUT_FILENO));

base::Process process = base::LaunchProcess(argv, options);

return process.IsValid() ? 0 : 1;

}

} // namespace internal

} // namespace relauncher