common/libs/utils/subprocess.cpp - device/google/cuttlefish - Git at Google

 /*
  * Copyright (C) 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "common/libs/utils/subprocess.h"

 #include <fcntl.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>

 #include <cerrno>
 #include <cstring>
 #include <map>
 #include <memory>
 #include <ostream>
 #include <set>
 #include <sstream>
 #include <string>
 #include <thread>
 #include <utility>
 #include <vector>

 #include <android-base/logging.h>
 #include <android-base/strings.h>

 #include "common/libs/fs/shared_buf.h"
 #include "common/libs/utils/files.h"

 extern char** environ;

 namespace cuttlefish {
 namespace {

 // If a redirected-to file descriptor was already closed, it's possible that
 // some inherited file descriptor duped to this file descriptor and the redirect
 // would override that. This function makes sure that doesn't happen.
 bool validate_redirects(
     const std::map<Subprocess::StdIOChannel, int>& redirects,
     const std::map<SharedFD, int>& inherited_fds) {
   // Add the redirected IO channels to a set as integers. This allows converting
   // the enum values into integers instead of the other way around.
   std::set<int> int_redirects;
   for (const auto& entry : redirects) {
     int_redirects.insert(static_cast<int>(entry.first));
   }
   for (const auto& entry : inherited_fds) {
     auto dupped_fd = entry.second;
     if (int_redirects.count(dupped_fd)) {
       LOG(ERROR) << "Requested redirect of fd(" << dupped_fd
                  << ") conflicts with inherited FD.";
       return false;
     }
   }
   return true;
 }

 void do_redirects(const std::map<Subprocess::StdIOChannel, int>& redirects) {
   for (const auto& entry : redirects) {
     auto std_channel = static_cast<int>(entry.first);
     auto fd = entry.second;
     TEMP_FAILURE_RETRY(dup2(fd, std_channel));
   }
 }

 std::vector<const char*> ToCharPointers(const std::vector<std::string>& vect) {
   std::vector<const char*> ret = {};
   for (const auto& str : vect) {
     ret.push_back(str.c_str());
   }
   ret.push_back(NULL);
   return ret;
 }
 }  // namespace

 SubprocessOptions& SubprocessOptions::Verbose(bool verbose) & {
   verbose_ = verbose;
   return *this;
 }
 SubprocessOptions SubprocessOptions::Verbose(bool verbose) && {
   verbose_ = verbose;
   return *this;
 }

 SubprocessOptions& SubprocessOptions::ExitWithParent(bool v) & {
   exit_with_parent_ = v;
   return *this;
 }
 SubprocessOptions SubprocessOptions::ExitWithParent(bool v) && {
   exit_with_parent_ = v;
   return *this;
 }

 SubprocessOptions& SubprocessOptions::InGroup(bool in_group) & {
   in_group_ = in_group;
   return *this;
 }
 SubprocessOptions SubprocessOptions::InGroup(bool in_group) && {
   in_group_ = in_group;
   return *this;
 }

 Subprocess::Subprocess(Subprocess&& subprocess)
     : pid_(subprocess.pid_),
       started_(subprocess.started_),
       stopper_(subprocess.stopper_) {
   // Make sure the moved object no longer controls this subprocess
   subprocess.pid_ = -1;
   subprocess.started_ = false;
 }

 Subprocess& Subprocess::operator=(Subprocess&& other) {
   pid_ = other.pid_;
   started_ = other.started_;
   stopper_ = other.stopper_;

   other.pid_ = -1;
   other.started_ = false;
   return *this;
 }

 int Subprocess::Wait() {
   if (pid_ < 0) {
     LOG(ERROR)
         << "Attempt to wait on invalid pid(has it been waited on already?): "
         << pid_;
     return -1;
   }
   int wstatus = 0;
   auto pid = pid_;  // Wait will set pid_ to -1 after waiting
   auto wait_ret = waitpid(pid, &wstatus, 0);
   if (wait_ret < 0) {
     auto error = errno;
     LOG(ERROR) << "Error on call to waitpid: " << strerror(error);
     return wait_ret;
   }
   int retval = 0;
   if (WIFEXITED(wstatus)) {
     retval = WEXITSTATUS(wstatus);
     if (retval) {
       LOG(DEBUG) << "Subprocess " << pid
                  << " exited with error code: " << retval;
     }
   } else if (WIFSIGNALED(wstatus)) {
     LOG(ERROR) << "Subprocess " << pid
                << " was interrupted by a signal: " << WTERMSIG(wstatus);
     retval = -1;
   }
   return retval;
 }
 int Subprocess::Wait(siginfo_t* infop, int options) {
   if (pid_ < 0) {
     LOG(ERROR)
         << "Attempt to wait on invalid pid(has it been waited on already?): "
         << pid_;
     return -1;
   }
   *infop = {};
   auto retval = waitid(P_PID, pid_, infop, options);
   // We don't want to wait twice for the same process
   bool exited = infop->si_code == CLD_EXITED || infop->si_code == CLD_DUMPED ||
                 infop->si_code == CLD_DUMPED;
   bool reaped = !(options & WNOWAIT);
   if (exited && reaped) {
     pid_ = -1;
   }
   return retval;
 }

 StopperResult KillSubprocess(Subprocess* subprocess) {
   auto pid = subprocess->pid();
   if (pid > 0) {
     auto pgid = getpgid(pid);
     if (pgid < 0) {
       auto error = errno;
       LOG(WARNING) << "Error obtaining process group id of process with pid="
                    << pid << ": " << strerror(error);
       // Send the kill signal anyways, because pgid will be -1 it will be sent
       // to the process and not a (non-existent) group
     }
     bool is_group_head = pid == pgid;
     auto kill_ret = (is_group_head ? killpg : kill)(pid, SIGKILL);
     if (kill_ret == 0) {
       return StopperResult::kStopSuccess;
     }
     auto kill_cmd = is_group_head ? "killpg(" : "kill(";
     PLOG(ERROR) << kill_cmd << pid << ", SIGKILL) failed: ";
     return StopperResult::kStopFailure;
   }
   return StopperResult::kStopSuccess;
 }

 Command::Command(const std::string& executable, SubprocessStopper stopper)
     : subprocess_stopper_(stopper) {
   for (char** env = environ; *env; env++) {
     env_.emplace_back(*env);
   }
   command_.push_back(executable);
 }

 Command::~Command() {
   // Close all inherited file descriptors
   for (const auto& entry : inherited_fds_) {
     close(entry.second);
   }
   // Close all redirected file descriptors
   for (const auto& entry : redirects_) {
     close(entry.second);
   }
 }

 void Command::BuildParameter(std::stringstream* stream, SharedFD shared_fd) {
   int fd;
   if (inherited_fds_.count(shared_fd)) {
     fd = inherited_fds_[shared_fd];
   } else {
     fd = shared_fd->Fcntl(F_DUPFD_CLOEXEC, 3);
     CHECK(fd >= 0) << "Could not acquire a new file descriptor: "
                    << shared_fd->StrError();
     inherited_fds_[shared_fd] = fd;
   }
   *stream << fd;
 }

 Command& Command::RedirectStdIO(Subprocess::StdIOChannel channel,
                                 SharedFD shared_fd) & {
   CHECK(shared_fd->IsOpen());
   CHECK(redirects_.count(channel) == 0)
       << "Attempted multiple redirections of fd: " << static_cast<int>(channel);
   auto dup_fd = shared_fd->Fcntl(F_DUPFD_CLOEXEC, 3);
   CHECK(dup_fd >= 0) << "Could not acquire a new file descriptor: "
                      << shared_fd->StrError();
   redirects_[channel] = dup_fd;
   return *this;
 }
 Command Command::RedirectStdIO(Subprocess::StdIOChannel channel,
                                SharedFD shared_fd) && {
   RedirectStdIO(channel, shared_fd);
   return std::move(*this);
 }
 Command& Command::RedirectStdIO(Subprocess::StdIOChannel subprocess_channel,
                                 Subprocess::StdIOChannel parent_channel) & {
   return RedirectStdIO(subprocess_channel,
                        SharedFD::Dup(static_cast<int>(parent_channel)));
 }
 Command Command::RedirectStdIO(Subprocess::StdIOChannel subprocess_channel,
                                Subprocess::StdIOChannel parent_channel) && {
   RedirectStdIO(subprocess_channel, parent_channel);
   return std::move(*this);
 }

 Command& Command::SetWorkingDirectory(std::string path) & {
   auto fd = SharedFD::Open(path, O_RDONLY | O_PATH | O_DIRECTORY);
   CHECK(fd->IsOpen()) << "Could not open \"" << path
                       << "\" dir fd: " << fd->StrError();
   return SetWorkingDirectory(fd);
 }
 Command Command::SetWorkingDirectory(std::string path) && {
   auto fd = SharedFD::Open(path, O_RDONLY | O_PATH | O_DIRECTORY);
   CHECK(fd->IsOpen()) << "Could not open \"" << path
                       << "\" dir fd: " << fd->StrError();
   return std::move(SetWorkingDirectory(fd));
 }
 Command& Command::SetWorkingDirectory(SharedFD dirfd) & {
   CHECK(dirfd->IsOpen()) << "Dir fd invalid: " << dirfd->StrError();
   working_directory_ = dirfd;
   return *this;
 }
 Command Command::SetWorkingDirectory(SharedFD dirfd) && {
   CHECK(dirfd->IsOpen()) << "Dir fd invalid: " << dirfd->StrError();
   working_directory_ = dirfd;
   return std::move(*this);
 }

 Subprocess Command::Start(SubprocessOptions options) const {
   auto cmd = ToCharPointers(command_);

   if (!validate_redirects(redirects_, inherited_fds_)) {
     return Subprocess(-1, {});
   }

   pid_t pid = fork();
   if (!pid) {
     if (options.ExitWithParent()) {
       prctl(PR_SET_PDEATHSIG, SIGHUP); // Die when parent dies
     }

     do_redirects(redirects_);
     if (options.InGroup()) {
       // This call should never fail (see SETPGID(2))
       if (setpgid(0, 0) != 0) {
         auto error = errno;
         LOG(ERROR) << "setpgid failed (" << strerror(error) << ")";
       }
     }
     for (const auto& entry : inherited_fds_) {
       if (fcntl(entry.second, F_SETFD, 0)) {
         int error_num = errno;
         LOG(ERROR) << "fcntl failed: " << strerror(error_num);
       }
     }
     if (working_directory_->IsOpen()) {
       if (SharedFD::Fchdir(working_directory_) != 0) {
         LOG(ERROR) << "Fchdir failed: " << working_directory_->StrError();
       }
     }
     int rval;
     auto envp = ToCharPointers(env_);
     rval = execvpe(cmd[0], const_cast<char* const*>(cmd.data()),
                    const_cast<char* const*>(envp.data()));
     // No need for an if: if exec worked it wouldn't have returned
     LOG(ERROR) << "exec of " << cmd[0] << " failed (" << strerror(errno)
                << ")";
     exit(rval);
   }
   if (pid == -1) {
     LOG(ERROR) << "fork failed (" << strerror(errno) << ")";
   }
   if (options.Verbose()) { // "more verbose", and LOG(DEBUG) > LOG(VERBOSE)
     LOG(DEBUG) << "Started (pid: " << pid << "): " << cmd[0];
     for (int i = 1; cmd[i]; i++) {
       LOG(DEBUG) << cmd[i];
     }
   } else {
     LOG(VERBOSE) << "Started (pid: " << pid << "): " << cmd[0];
     for (int i = 1; cmd[i]; i++) {
       LOG(VERBOSE) << cmd[i];
     }
   }
   return Subprocess(pid, subprocess_stopper_);
 }

 std::string Command::AsBashScript(
     const std::string& redirected_stdio_path) const {
   CHECK(inherited_fds_.empty())
       << "Bash wrapper will not have inheritied file descriptors.";
   CHECK(redirects_.empty()) << "Bash wrapper will not have redirected stdio.";

   std::string contents =
       "#!/bin/bash\n\n" + android::base::Join(command_, " \\\n");
   if (!redirected_stdio_path.empty()) {
     contents += " &> " + AbsolutePath(redirected_stdio_path);
   }
   return contents;
 }

 // A class that waits for threads to exit in its destructor.
 class ThreadJoiner {
 std::vector<std::thread*> threads_;
 public:
   ThreadJoiner(const std::vector<std::thread*> threads) : threads_(threads) {}
   ~ThreadJoiner() {
     for (auto& thread : threads_) {
       if (thread->joinable()) {
         thread->join();
       }
     }
   }
 };

 int RunWithManagedStdio(Command&& cmd_tmp, const std::string* stdin_str,
                         std::string* stdout_str, std::string* stderr_str,
                         SubprocessOptions options) {
   /*
    * The order of these declarations is necessary for safety. If the function
    * returns at any point, the Command will be destroyed first, closing all
    * of its references to SharedFDs. This will cause the thread internals to fail
    * their reads or writes. The ThreadJoiner then waits for the threads to
    * complete, as running the destructor of an active std::thread crashes the
    * program.
    *
    * C++ scoping rules dictate that objects are descoped in reverse order to
    * construction, so this behavior is predictable.
    */
   std::thread stdin_thread, stdout_thread, stderr_thread;
   ThreadJoiner thread_joiner({&stdin_thread, &stdout_thread, &stderr_thread});
   Command cmd = std::move(cmd_tmp);
   bool io_error = false;
   if (stdin_str != nullptr) {
     SharedFD pipe_read, pipe_write;
     if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
       LOG(ERROR) << "Could not create a pipe to write the stdin of \""
                 << cmd.GetShortName() << "\"";
       return -1;
     }
     cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdIn, pipe_read);
     stdin_thread = std::thread([pipe_write, stdin_str, &io_error]() {
       int written = WriteAll(pipe_write, *stdin_str);
       if (written < 0) {
         io_error = true;
         LOG(ERROR) << "Error in writing stdin to process";
       }
     });
   }
   if (stdout_str != nullptr) {
     SharedFD pipe_read, pipe_write;
     if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
       LOG(ERROR) << "Could not create a pipe to read the stdout of \""
                 << cmd.GetShortName() << "\"";
       return -1;
     }
     cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdOut, pipe_write);
     stdout_thread = std::thread([pipe_read, stdout_str, &io_error]() {
       int read = ReadAll(pipe_read, stdout_str);
       if (read < 0) {
         io_error = true;
         LOG(ERROR) << "Error in reading stdout from process";
       }
     });
   }
   if (stderr_str != nullptr) {
     SharedFD pipe_read, pipe_write;
     if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
       LOG(ERROR) << "Could not create a pipe to read the stderr of \""
                 << cmd.GetShortName() << "\"";
       return -1;
     }
     cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdErr, pipe_write);
     stderr_thread = std::thread([pipe_read, stderr_str, &io_error]() {
       int read = ReadAll(pipe_read, stderr_str);
       if (read < 0) {
         io_error = true;
         LOG(ERROR) << "Error in reading stderr from process";
       }
     });
   }

   auto subprocess = cmd.Start(options);
   if (!subprocess.Started()) {
     return -1;
   }
   auto cmd_short_name = cmd.GetShortName();
   {
     // Force the destructor to run by moving it into a smaller scope.
     // This is necessary to close the write end of the pipe.
     Command forceDelete = std::move(cmd);
   }

   int code = subprocess.Wait();
   {
     auto join_threads = std::move(thread_joiner);
   }
   if (io_error) {
     LOG(ERROR) << "IO error communicating with " << cmd_short_name;
     return -1;
   }
   return code;
 }

 int execute(const std::vector<std::string>& command,
             const std::vector<std::string>& env) {
   Command cmd(command[0]);
   for (size_t i = 1; i < command.size(); ++i) {
     cmd.AddParameter(command[i]);
   }
   cmd.SetEnvironment(env);
   auto subprocess = cmd.Start();
   if (!subprocess.Started()) {
     return -1;
   }
   return subprocess.Wait();
 }
 int execute(const std::vector<std::string>& command) {
   Command cmd(command[0]);
   for (size_t i = 1; i < command.size(); ++i) {
     cmd.AddParameter(command[i]);
   }
   auto subprocess = cmd.Start();
   if (!subprocess.Started()) {
     return -1;
   }
   return subprocess.Wait();
 }

 }  // namespace cuttlefish
	/*
	* Copyright (C) 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "common/libs/utils/subprocess.h"

	#include <fcntl.h>
	#include <signal.h>
	#include <stdlib.h>
	#include <sys/prctl.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <unistd.h>

	#include <cerrno>
	#include <cstring>
	#include <map>
	#include <memory>
	#include <ostream>
	#include <set>
	#include <sstream>
	#include <string>
	#include <thread>
	#include <utility>
	#include <vector>

	#include <android-base/logging.h>
	#include <android-base/strings.h>

	#include "common/libs/fs/shared_buf.h"
	#include "common/libs/utils/files.h"

	extern char** environ;

	namespace cuttlefish {
	namespace {

	// If a redirected-to file descriptor was already closed, it's possible that
	// some inherited file descriptor duped to this file descriptor and the redirect
	// would override that. This function makes sure that doesn't happen.
	bool validate_redirects(
	const std::map<Subprocess::StdIOChannel, int>& redirects,
	const std::map<SharedFD, int>& inherited_fds) {
	// Add the redirected IO channels to a set as integers. This allows converting
	// the enum values into integers instead of the other way around.
	std::set<int> int_redirects;
	for (const auto& entry : redirects) {
	int_redirects.insert(static_cast<int>(entry.first));
	}
	for (const auto& entry : inherited_fds) {
	auto dupped_fd = entry.second;
	if (int_redirects.count(dupped_fd)) {
	LOG(ERROR) << "Requested redirect of fd(" << dupped_fd
	<< ") conflicts with inherited FD.";
	return false;
	}
	}
	return true;
	}

	void do_redirects(const std::map<Subprocess::StdIOChannel, int>& redirects) {
	for (const auto& entry : redirects) {
	auto std_channel = static_cast<int>(entry.first);
	auto fd = entry.second;
	TEMP_FAILURE_RETRY(dup2(fd, std_channel));
	}
	}

	std::vector<const char*> ToCharPointers(const std::vector<std::string>& vect) {
	std::vector<const char*> ret = {};
	for (const auto& str : vect) {
	ret.push_back(str.c_str());
	}
	ret.push_back(NULL);
	return ret;
	}
	} // namespace

	SubprocessOptions& SubprocessOptions::Verbose(bool verbose) & {
	verbose_ = verbose;
	return *this;
	}
	SubprocessOptions SubprocessOptions::Verbose(bool verbose) && {
	verbose_ = verbose;
	return *this;
	}

	SubprocessOptions& SubprocessOptions::ExitWithParent(bool v) & {
	exit_with_parent_ = v;
	return *this;
	}
	SubprocessOptions SubprocessOptions::ExitWithParent(bool v) && {
	exit_with_parent_ = v;
	return *this;
	}

	SubprocessOptions& SubprocessOptions::InGroup(bool in_group) & {
	in_group_ = in_group;
	return *this;
	}
	SubprocessOptions SubprocessOptions::InGroup(bool in_group) && {
	in_group_ = in_group;
	return *this;
	}

	Subprocess::Subprocess(Subprocess&& subprocess)
	: pid_(subprocess.pid_),
	started_(subprocess.started_),
	stopper_(subprocess.stopper_) {
	// Make sure the moved object no longer controls this subprocess
	subprocess.pid_ = -1;
	subprocess.started_ = false;
	}

	Subprocess& Subprocess::operator=(Subprocess&& other) {
	pid_ = other.pid_;
	started_ = other.started_;
	stopper_ = other.stopper_;

	other.pid_ = -1;
	other.started_ = false;
	return *this;
	}

	int Subprocess::Wait() {
	if (pid_ < 0) {
	LOG(ERROR)
	<< "Attempt to wait on invalid pid(has it been waited on already?): "
	<< pid_;
	return -1;
	}
	int wstatus = 0;
	auto pid = pid_; // Wait will set pid_ to -1 after waiting
	auto wait_ret = waitpid(pid, &wstatus, 0);
	if (wait_ret < 0) {
	auto error = errno;
	LOG(ERROR) << "Error on call to waitpid: " << strerror(error);
	return wait_ret;
	}
	int retval = 0;
	if (WIFEXITED(wstatus)) {
	retval = WEXITSTATUS(wstatus);
	if (retval) {
	LOG(DEBUG) << "Subprocess " << pid
	<< " exited with error code: " << retval;
	}
	} else if (WIFSIGNALED(wstatus)) {
	LOG(ERROR) << "Subprocess " << pid
	<< " was interrupted by a signal: " << WTERMSIG(wstatus);
	retval = -1;
	}
	return retval;
	}
	int Subprocess::Wait(siginfo_t* infop, int options) {
	if (pid_ < 0) {
	LOG(ERROR)
	<< "Attempt to wait on invalid pid(has it been waited on already?): "
	<< pid_;
	return -1;
	}
	*infop = {};
	auto retval = waitid(P_PID, pid_, infop, options);
	// We don't want to wait twice for the same process
	bool exited = infop->si_code == CLD_EXITED \|\| infop->si_code == CLD_DUMPED \|\|
	infop->si_code == CLD_DUMPED;
	bool reaped = !(options & WNOWAIT);
	if (exited && reaped) {
	pid_ = -1;
	}
	return retval;
	}

	StopperResult KillSubprocess(Subprocess* subprocess) {
	auto pid = subprocess->pid();
	if (pid > 0) {
	auto pgid = getpgid(pid);
	if (pgid < 0) {
	auto error = errno;
	LOG(WARNING) << "Error obtaining process group id of process with pid="
	<< pid << ": " << strerror(error);
	// Send the kill signal anyways, because pgid will be -1 it will be sent
	// to the process and not a (non-existent) group
	}
	bool is_group_head = pid == pgid;
	auto kill_ret = (is_group_head ? killpg : kill)(pid, SIGKILL);
	if (kill_ret == 0) {
	return StopperResult::kStopSuccess;
	}
	auto kill_cmd = is_group_head ? "killpg(" : "kill(";
	PLOG(ERROR) << kill_cmd << pid << ", SIGKILL) failed: ";
	return StopperResult::kStopFailure;
	}
	return StopperResult::kStopSuccess;
	}

	Command::Command(const std::string& executable, SubprocessStopper stopper)
	: subprocess_stopper_(stopper) {
	for (char** env = environ; *env; env++) {
	env_.emplace_back(*env);
	}
	command_.push_back(executable);
	}

	Command::~Command() {
	// Close all inherited file descriptors
	for (const auto& entry : inherited_fds_) {
	close(entry.second);
	}
	// Close all redirected file descriptors
	for (const auto& entry : redirects_) {
	close(entry.second);
	}
	}

	void Command::BuildParameter(std::stringstream* stream, SharedFD shared_fd) {
	int fd;
	if (inherited_fds_.count(shared_fd)) {
	fd = inherited_fds_[shared_fd];
	} else {
	fd = shared_fd->Fcntl(F_DUPFD_CLOEXEC, 3);
	CHECK(fd >= 0) << "Could not acquire a new file descriptor: "
	<< shared_fd->StrError();
	inherited_fds_[shared_fd] = fd;
	}
	*stream << fd;
	}

	Command& Command::RedirectStdIO(Subprocess::StdIOChannel channel,
	SharedFD shared_fd) & {
	CHECK(shared_fd->IsOpen());
	CHECK(redirects_.count(channel) == 0)
	<< "Attempted multiple redirections of fd: " << static_cast<int>(channel);
	auto dup_fd = shared_fd->Fcntl(F_DUPFD_CLOEXEC, 3);
	CHECK(dup_fd >= 0) << "Could not acquire a new file descriptor: "
	<< shared_fd->StrError();
	redirects_[channel] = dup_fd;
	return *this;
	}
	Command Command::RedirectStdIO(Subprocess::StdIOChannel channel,
	SharedFD shared_fd) && {
	RedirectStdIO(channel, shared_fd);
	return std::move(*this);
	}
	Command& Command::RedirectStdIO(Subprocess::StdIOChannel subprocess_channel,
	Subprocess::StdIOChannel parent_channel) & {
	return RedirectStdIO(subprocess_channel,
	SharedFD::Dup(static_cast<int>(parent_channel)));
	}
	Command Command::RedirectStdIO(Subprocess::StdIOChannel subprocess_channel,
	Subprocess::StdIOChannel parent_channel) && {
	RedirectStdIO(subprocess_channel, parent_channel);
	return std::move(*this);
	}

	Command& Command::SetWorkingDirectory(std::string path) & {
	auto fd = SharedFD::Open(path, O_RDONLY \| O_PATH \| O_DIRECTORY);
	CHECK(fd->IsOpen()) << "Could not open \"" << path
	<< "\" dir fd: " << fd->StrError();
	return SetWorkingDirectory(fd);
	}
	Command Command::SetWorkingDirectory(std::string path) && {
	auto fd = SharedFD::Open(path, O_RDONLY \| O_PATH \| O_DIRECTORY);
	CHECK(fd->IsOpen()) << "Could not open \"" << path
	<< "\" dir fd: " << fd->StrError();
	return std::move(SetWorkingDirectory(fd));
	}
	Command& Command::SetWorkingDirectory(SharedFD dirfd) & {
	CHECK(dirfd->IsOpen()) << "Dir fd invalid: " << dirfd->StrError();
	working_directory_ = dirfd;
	return *this;
	}
	Command Command::SetWorkingDirectory(SharedFD dirfd) && {
	CHECK(dirfd->IsOpen()) << "Dir fd invalid: " << dirfd->StrError();
	working_directory_ = dirfd;
	return std::move(*this);
	}

	Subprocess Command::Start(SubprocessOptions options) const {
	auto cmd = ToCharPointers(command_);

	if (!validate_redirects(redirects_, inherited_fds_)) {
	return Subprocess(-1, {});
	}

	pid_t pid = fork();
	if (!pid) {
	if (options.ExitWithParent()) {
	prctl(PR_SET_PDEATHSIG, SIGHUP); // Die when parent dies
	}

	do_redirects(redirects_);
	if (options.InGroup()) {
	// This call should never fail (see SETPGID(2))
	if (setpgid(0, 0) != 0) {
	auto error = errno;
	LOG(ERROR) << "setpgid failed (" << strerror(error) << ")";
	}
	}
	for (const auto& entry : inherited_fds_) {
	if (fcntl(entry.second, F_SETFD, 0)) {
	int error_num = errno;
	LOG(ERROR) << "fcntl failed: " << strerror(error_num);
	}
	}
	if (working_directory_->IsOpen()) {
	if (SharedFD::Fchdir(working_directory_) != 0) {
	LOG(ERROR) << "Fchdir failed: " << working_directory_->StrError();
	}
	}
	int rval;
	auto envp = ToCharPointers(env_);
	rval = execvpe(cmd[0], const_cast<char* const*>(cmd.data()),
	const_cast<char* const*>(envp.data()));
	// No need for an if: if exec worked it wouldn't have returned
	LOG(ERROR) << "exec of " << cmd[0] << " failed (" << strerror(errno)
	<< ")";
	exit(rval);
	}
	if (pid == -1) {
	LOG(ERROR) << "fork failed (" << strerror(errno) << ")";
	}
	if (options.Verbose()) { // "more verbose", and LOG(DEBUG) > LOG(VERBOSE)
	LOG(DEBUG) << "Started (pid: " << pid << "): " << cmd[0];
	for (int i = 1; cmd[i]; i++) {
	LOG(DEBUG) << cmd[i];
	}
	} else {
	LOG(VERBOSE) << "Started (pid: " << pid << "): " << cmd[0];
	for (int i = 1; cmd[i]; i++) {
	LOG(VERBOSE) << cmd[i];
	}
	}
	return Subprocess(pid, subprocess_stopper_);
	}

	std::string Command::AsBashScript(
	const std::string& redirected_stdio_path) const {
	CHECK(inherited_fds_.empty())
	<< "Bash wrapper will not have inheritied file descriptors.";
	CHECK(redirects_.empty()) << "Bash wrapper will not have redirected stdio.";

	std::string contents =
	"#!/bin/bash\n\n" + android::base::Join(command_, " \\\n");
	if (!redirected_stdio_path.empty()) {
	contents += " &> " + AbsolutePath(redirected_stdio_path);
	}
	return contents;
	}

	// A class that waits for threads to exit in its destructor.
	class ThreadJoiner {
	std::vector<std::thread*> threads_;
	public:
	ThreadJoiner(const std::vector<std::thread*> threads) : threads_(threads) {}
	~ThreadJoiner() {
	for (auto& thread : threads_) {
	if (thread->joinable()) {
	thread->join();
	}
	}
	}
	};

	int RunWithManagedStdio(Command&& cmd_tmp, const std::string* stdin_str,
	std::string* stdout_str, std::string* stderr_str,
	SubprocessOptions options) {
	/*
	* The order of these declarations is necessary for safety. If the function
	* returns at any point, the Command will be destroyed first, closing all
	* of its references to SharedFDs. This will cause the thread internals to fail
	* their reads or writes. The ThreadJoiner then waits for the threads to
	* complete, as running the destructor of an active std::thread crashes the
	* program.
	*
	* C++ scoping rules dictate that objects are descoped in reverse order to
	* construction, so this behavior is predictable.
	*/
	std::thread stdin_thread, stdout_thread, stderr_thread;
	ThreadJoiner thread_joiner({&stdin_thread, &stdout_thread, &stderr_thread});
	Command cmd = std::move(cmd_tmp);
	bool io_error = false;
	if (stdin_str != nullptr) {
	SharedFD pipe_read, pipe_write;
	if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
	LOG(ERROR) << "Could not create a pipe to write the stdin of \""
	<< cmd.GetShortName() << "\"";
	return -1;
	}
	cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdIn, pipe_read);
	stdin_thread = std::thread([pipe_write, stdin_str, &io_error]() {
	int written = WriteAll(pipe_write, *stdin_str);
	if (written < 0) {
	io_error = true;
	LOG(ERROR) << "Error in writing stdin to process";
	}
	});
	}
	if (stdout_str != nullptr) {
	SharedFD pipe_read, pipe_write;
	if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
	LOG(ERROR) << "Could not create a pipe to read the stdout of \""
	<< cmd.GetShortName() << "\"";
	return -1;
	}
	cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdOut, pipe_write);
	stdout_thread = std::thread([pipe_read, stdout_str, &io_error]() {
	int read = ReadAll(pipe_read, stdout_str);
	if (read < 0) {
	io_error = true;
	LOG(ERROR) << "Error in reading stdout from process";
	}
	});
	}
	if (stderr_str != nullptr) {
	SharedFD pipe_read, pipe_write;
	if (!SharedFD::Pipe(&pipe_read, &pipe_write)) {
	LOG(ERROR) << "Could not create a pipe to read the stderr of \""
	<< cmd.GetShortName() << "\"";
	return -1;
	}
	cmd.RedirectStdIO(Subprocess::StdIOChannel::kStdErr, pipe_write);
	stderr_thread = std::thread([pipe_read, stderr_str, &io_error]() {
	int read = ReadAll(pipe_read, stderr_str);
	if (read < 0) {
	io_error = true;
	LOG(ERROR) << "Error in reading stderr from process";
	}
	});
	}

	auto subprocess = cmd.Start(options);
	if (!subprocess.Started()) {
	return -1;
	}
	auto cmd_short_name = cmd.GetShortName();
	{
	// Force the destructor to run by moving it into a smaller scope.
	// This is necessary to close the write end of the pipe.
	Command forceDelete = std::move(cmd);
	}

	int code = subprocess.Wait();
	{
	auto join_threads = std::move(thread_joiner);
	}
	if (io_error) {
	LOG(ERROR) << "IO error communicating with " << cmd_short_name;
	return -1;
	}
	return code;
	}

	int execute(const std::vector<std::string>& command,
	const std::vector<std::string>& env) {
	Command cmd(command[0]);
	for (size_t i = 1; i < command.size(); ++i) {
	cmd.AddParameter(command[i]);
	}
	cmd.SetEnvironment(env);
	auto subprocess = cmd.Start();
	if (!subprocess.Started()) {
	return -1;
	}
	return subprocess.Wait();
	}
	int execute(const std::vector<std::string>& command) {
	Command cmd(command[0]);
	for (size_t i = 1; i < command.size(); ++i) {
	cmd.AddParameter(command[i]);
	}
	auto subprocess = cmd.Start();
	if (!subprocess.Started()) {
	return -1;
	}
	return subprocess.Wait();
	}

	} // namespace cuttlefish