common/subprocess.cc - android_system_update_engine - Gitiles

 //
 // Copyright (C) 2012 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 "update_engine/common/subprocess.h"

 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #include <chrono>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>

 #include <base/bind.h>
 #include <base/logging.h>
 #include <base/posix/eintr_wrapper.h>
 #include <base/stl_util.h>
 #include <base/strings/string_util.h>
 #include <base/strings/stringprintf.h>
 #include <brillo/secure_blob.h>

 #include "update_engine/common/utils.h"

 using brillo::MessageLoop;
 using std::string;
 using std::unique_ptr;
 using std::vector;

 namespace chromeos_update_engine {

 namespace {

 bool SetupChild(const std::map<string, string>& env, uint32_t flags) {
   // Setup the environment variables.
   clearenv();
   if (setpgid(0, 0) != 0) {
     PLOG(ERROR) << "Failed to setpgid on subprocess " << getpid();
     return false;
   }
   for (const auto& key_value : env) {
     setenv(key_value.first.c_str(), key_value.second.c_str(), 0);
   }

   if ((flags & Subprocess::kRedirectStderrToStdout) != 0) {
     if (HANDLE_EINTR(dup2(STDOUT_FILENO, STDERR_FILENO)) != STDERR_FILENO)
       return false;
   }

   int fd = HANDLE_EINTR(open("/dev/null", O_RDONLY));
   if (fd < 0)
     return false;
   if (HANDLE_EINTR(dup2(fd, STDIN_FILENO)) != STDIN_FILENO)
     return false;
   IGNORE_EINTR(close(fd));

   return true;
 }

 // Helper function to launch a process with the given Subprocess::Flags.
 // This function only sets up and starts the process according to the |flags|.
 // The caller is responsible for watching the termination of the subprocess.
 // Return whether the process was successfully launched and fills in the |proc|
 // Process.
 bool LaunchProcess(const vector<string>& cmd,
                    uint32_t flags,
                    const vector<int>& output_pipes,
                    brillo::Process* proc) {
   for (const string& arg : cmd)
     proc->AddArg(arg);
   proc->SetSearchPath((flags & Subprocess::kSearchPath) != 0);

   // Create an environment for the child process with just the required PATHs.
   std::map<string, string> env;
   for (const char* key : {"LD_LIBRARY_PATH", "PATH"}) {
     const char* value = getenv(key);
     if (value)
       env.emplace(key, value);
   }

   for (const int fd : output_pipes) {
     proc->RedirectUsingPipe(fd, false);
   }
   proc->SetCloseUnusedFileDescriptors(true);
   proc->RedirectUsingPipe(STDOUT_FILENO, false);
   proc->SetPreExecCallback(base::Bind(&SetupChild, env, flags));

   LOG(INFO) << "Running \"" << base::JoinString(cmd, " ") << "\"";
   return proc->Start();
 }

 }  // namespace

 void Subprocess::Init(
     brillo::AsynchronousSignalHandlerInterface* async_signal_handler) {
   if (subprocess_singleton_ == this)
     return;
   CHECK(subprocess_singleton_ == nullptr);
   subprocess_singleton_ = this;

   process_reaper_.Register(async_signal_handler);
 }

 Subprocess::~Subprocess() {
   if (subprocess_singleton_ == this)
     subprocess_singleton_ = nullptr;
 }

 void Subprocess::OnStdoutReady(SubprocessRecord* record) {
   char buf[1024];
   size_t bytes_read;
   do {
     bytes_read = 0;
     bool eof;
     bool ok = utils::ReadAll(
         record->stdout_fd, buf, base::size(buf), &bytes_read, &eof);
     record->stdout_str.append(buf, bytes_read);
     if (!ok || eof) {
       // There was either an error or an EOF condition, so we are done watching
       // the file descriptor.
       record->stdout_controller.reset();
       return;
     }
   } while (bytes_read);
 }

 void Subprocess::ChildExitedCallback(const siginfo_t& info) {
   auto pid_record = subprocess_records_.find(info.si_pid);
   if (pid_record == subprocess_records_.end())
     return;
   SubprocessRecord* record = pid_record->second.get();

   // Make sure we read any remaining process output and then close the pipe.
   OnStdoutReady(record);

   record->stdout_controller.reset();

   // Don't print any log if the subprocess exited with exit code 0.
   if (info.si_code != CLD_EXITED) {
     LOG(INFO) << "Subprocess " << info.si_pid << " terminated with si_code "
               << info.si_code;
   } else if (info.si_status != 0) {
     LOG(INFO) << "Subprocess " << info.si_pid
               << " exited with si_status: " << info.si_status;
   }

   if (!record->stdout_str.empty()) {
     LOG(INFO) << "Subprocess output:\n" << record->stdout_str;
   }
   if (!record->callback.is_null()) {
     record->callback.Run(info.si_status, record->stdout_str);
   }
   // Release and close all the pipes after calling the callback so our
   // redirected pipes are still alive. Releasing the process first makes
   // Reset(0) not attempt to kill the process, which is already a zombie at this
   // point.
   record->proc.Release();
   record->proc.Reset(0);

   subprocess_records_.erase(pid_record);
 }

 pid_t Subprocess::Exec(const vector<string>& cmd,
                        const ExecCallback& callback) {
   return ExecFlags(cmd, kRedirectStderrToStdout, {}, callback);
 }

 pid_t Subprocess::ExecFlags(const vector<string>& cmd,
                             uint32_t flags,
                             const vector<int>& output_pipes,
                             const ExecCallback& callback) {
   unique_ptr<SubprocessRecord> record(new SubprocessRecord(callback));

   if (!LaunchProcess(cmd, flags, output_pipes, &record->proc)) {
     LOG(ERROR) << "Failed to launch subprocess";
     return 0;
   }

   pid_t pid = record->proc.pid();
   CHECK(process_reaper_.WatchForChild(
       FROM_HERE,
       pid,
       base::Bind(&Subprocess::ChildExitedCallback, base::Unretained(this))));

   record->stdout_fd = record->proc.GetPipe(STDOUT_FILENO);
   // Capture the subprocess output. Make our end of the pipe non-blocking.
   int fd_flags = fcntl(record->stdout_fd, F_GETFL, 0) | O_NONBLOCK;
   if (HANDLE_EINTR(fcntl(record->stdout_fd, F_SETFL, fd_flags)) < 0) {
     LOG(ERROR) << "Unable to set non-blocking I/O mode on fd "
                << record->stdout_fd << ".";
   }

   record->stdout_controller = base::FileDescriptorWatcher::WatchReadable(
       record->stdout_fd,
       base::BindRepeating(&Subprocess::OnStdoutReady, record.get()));

   subprocess_records_[pid] = std::move(record);
   return pid;
 }

 bool WaitForProcessGroup(pid_t pid, std::chrono::milliseconds timeout) {
   using std::chrono::system_clock;
   auto start = system_clock::now();
   do {
     pid_t w = waitpid(-pid, nullptr, WNOHANG);
     if (w < 0) {
       // When all of the child process with this process group ID exits, waitpid
       // will return ECHILD. Until that point, keep callilng waitpid() as there
       // might be multiple child processes with the same process group id.
       if (errno == ECHILD) {
         LOG(INFO) << "All processes with process group id " << pid << " exited";
         return true;
       }
       PLOG(ERROR) << "Waitpid returned " << w;
       return false;
     }
     usleep(100);
   } while ((system_clock::now() - start) <= timeout);
   LOG(INFO) << "process group " << pid << " did not exit in " << timeout.count()
             << " milliseconds";
   return false;
 }

 void Subprocess::KillExec(pid_t pid) {
   using namespace std::chrono_literals;
   auto pid_record = subprocess_records_.find(pid);
   if (pid_record == subprocess_records_.end())
     return;
   pid_record->second->callback.Reset();
   // We don't care about output/return code, so we use SIGKILL here to ensure it
   // will be killed, SIGTERM might lead to leaked subprocess.
   CHECK_EQ(pid_record->second->proc.pid(), pid);
   if (kill(-pid, SIGKILL) != 0) {
     PLOG(WARNING) << "Failed to kill subprocess group " << pid;
   }
   WaitForProcessGroup(pid, 5000ms);
   // Release the pid now so we don't try to kill it if Subprocess is destroyed
   // before the corresponding ChildExitedCallback() is called.
   pid_record->second->proc.Release();
   if (subprocess_records_.count(pid)) {
     siginfo_t info;
     info.si_code = CLD_KILLED;
     info.si_status = SIGKILL;
     info.si_pid = pid;
     ChildExitedCallback(info);
   }
 }

 int Subprocess::GetPipeFd(pid_t pid, int fd) const {
   auto pid_record = subprocess_records_.find(pid);
   if (pid_record == subprocess_records_.end())
     return -1;
   return pid_record->second->proc.GetPipe(fd);
 }

 bool Subprocess::SynchronousExec(const vector<string>& cmd,
                                  int* return_code,
                                  string* stdout_str,
                                  string* stderr_str) {
   // The default for |SynchronousExec| is to use |kSearchPath| since the code
   // relies on that.
   return SynchronousExecFlags(
       cmd, kSearchPath, return_code, stdout_str, stderr_str);
 }

 bool Subprocess::SynchronousExecFlags(const vector<string>& cmd,
                                       uint32_t flags,
                                       int* return_code,
                                       string* stdout_str,
                                       string* stderr_str) {
   brillo::ProcessImpl proc;
   if (!LaunchProcess(cmd, flags, {STDERR_FILENO}, &proc)) {
     LOG(ERROR) << "Failed to launch subprocess";
     return false;
   }

   if (stdout_str) {
     stdout_str->clear();
   }
   if (stderr_str) {
     stderr_str->clear();
   }

   // Read from both stdout and stderr individually.
   int stdout_fd = proc.GetPipe(STDOUT_FILENO);
   int stderr_fd = proc.GetPipe(STDERR_FILENO);
   vector<char> buffer(32 * 1024);
   bool stdout_closed = false, stderr_closed = false;
   while (!stdout_closed || !stderr_closed) {
     if (!stdout_closed) {
       int rc = HANDLE_EINTR(read(stdout_fd, buffer.data(), buffer.size()));
       if (rc <= 0) {
         stdout_closed = true;
         if (rc < 0)
           PLOG(ERROR) << "Reading from child's stdout";
       } else if (stdout_str != nullptr) {
         stdout_str->append(buffer.data(), rc);
       }
     }

     if (!stderr_closed) {
       int rc = HANDLE_EINTR(read(stderr_fd, buffer.data(), buffer.size()));
       if (rc <= 0) {
         stderr_closed = true;
         if (rc < 0)
           PLOG(ERROR) << "Reading from child's stderr";
       } else if (stderr_str != nullptr) {
         stderr_str->append(buffer.data(), rc);
       }
     }
   }

   // At this point, the subprocess already closed the output, so we only need to
   // wait for it to finish.
   int proc_return_code = proc.Wait();
   if (return_code)
     *return_code = proc_return_code;
   return proc_return_code != brillo::Process::kErrorExitStatus;
 }

 void Subprocess::FlushBufferedLogsAtExit() {
   if (!subprocess_records_.empty()) {
     LOG(INFO) << "We are exiting, but there are still in flight subprocesses!";
     for (auto& pid_record : subprocess_records_) {
       SubprocessRecord* record = pid_record.second.get();
       // Make sure we read any remaining process output.
       OnStdoutReady(record);
       if (!record->stdout_str.empty()) {
         LOG(INFO) << "Subprocess(" << pid_record.first << ") output:\n"
                   << record->stdout_str;
       }
     }
   }
 }

 Subprocess* Subprocess::subprocess_singleton_ = nullptr;

 }  // namespace chromeos_update_engine
	//
	// Copyright (C) 2012 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 "update_engine/common/subprocess.h"

	#include <fcntl.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#include <chrono>
	#include <memory>
	#include <string>
	#include <utility>
	#include <vector>

	#include <base/bind.h>
	#include <base/logging.h>
	#include <base/posix/eintr_wrapper.h>
	#include <base/stl_util.h>
	#include <base/strings/string_util.h>
	#include <base/strings/stringprintf.h>
	#include <brillo/secure_blob.h>

	#include "update_engine/common/utils.h"

	using brillo::MessageLoop;
	using std::string;
	using std::unique_ptr;
	using std::vector;

	namespace chromeos_update_engine {

	namespace {

	bool SetupChild(const std::map<string, string>& env, uint32_t flags) {
	// Setup the environment variables.
	clearenv();
	if (setpgid(0, 0) != 0) {
	PLOG(ERROR) << "Failed to setpgid on subprocess " << getpid();
	return false;
	}
	for (const auto& key_value : env) {
	setenv(key_value.first.c_str(), key_value.second.c_str(), 0);
	}

	if ((flags & Subprocess::kRedirectStderrToStdout) != 0) {
	if (HANDLE_EINTR(dup2(STDOUT_FILENO, STDERR_FILENO)) != STDERR_FILENO)
	return false;
	}

	int fd = HANDLE_EINTR(open("/dev/null", O_RDONLY));
	if (fd < 0)
	return false;
	if (HANDLE_EINTR(dup2(fd, STDIN_FILENO)) != STDIN_FILENO)
	return false;
	IGNORE_EINTR(close(fd));

	return true;
	}

	// Helper function to launch a process with the given Subprocess::Flags.
	// This function only sets up and starts the process according to the \|flags\|.
	// The caller is responsible for watching the termination of the subprocess.
	// Return whether the process was successfully launched and fills in the \|proc\|
	// Process.
	bool LaunchProcess(const vector<string>& cmd,
	uint32_t flags,
	const vector<int>& output_pipes,
	brillo::Process* proc) {
	for (const string& arg : cmd)
	proc->AddArg(arg);
	proc->SetSearchPath((flags & Subprocess::kSearchPath) != 0);

	// Create an environment for the child process with just the required PATHs.
	std::map<string, string> env;
	for (const char* key : {"LD_LIBRARY_PATH", "PATH"}) {
	const char* value = getenv(key);
	if (value)
	env.emplace(key, value);
	}

	for (const int fd : output_pipes) {
	proc->RedirectUsingPipe(fd, false);
	}
	proc->SetCloseUnusedFileDescriptors(true);
	proc->RedirectUsingPipe(STDOUT_FILENO, false);
	proc->SetPreExecCallback(base::Bind(&SetupChild, env, flags));

	LOG(INFO) << "Running \"" << base::JoinString(cmd, " ") << "\"";
	return proc->Start();
	}

	} // namespace

	void Subprocess::Init(
	brillo::AsynchronousSignalHandlerInterface* async_signal_handler) {
	if (subprocess_singleton_ == this)
	return;
	CHECK(subprocess_singleton_ == nullptr);
	subprocess_singleton_ = this;

	process_reaper_.Register(async_signal_handler);
	}

	Subprocess::~Subprocess() {
	if (subprocess_singleton_ == this)
	subprocess_singleton_ = nullptr;
	}

	void Subprocess::OnStdoutReady(SubprocessRecord* record) {
	char buf[1024];
	size_t bytes_read;
	do {
	bytes_read = 0;
	bool eof;
	bool ok = utils::ReadAll(
	record->stdout_fd, buf, base::size(buf), &bytes_read, &eof);
	record->stdout_str.append(buf, bytes_read);
	if (!ok \|\| eof) {
	// There was either an error or an EOF condition, so we are done watching
	// the file descriptor.
	record->stdout_controller.reset();
	return;
	}
	} while (bytes_read);
	}

	void Subprocess::ChildExitedCallback(const siginfo_t& info) {
	auto pid_record = subprocess_records_.find(info.si_pid);
	if (pid_record == subprocess_records_.end())
	return;
	SubprocessRecord* record = pid_record->second.get();

	// Make sure we read any remaining process output and then close the pipe.
	OnStdoutReady(record);

	record->stdout_controller.reset();

	// Don't print any log if the subprocess exited with exit code 0.
	if (info.si_code != CLD_EXITED) {
	LOG(INFO) << "Subprocess " << info.si_pid << " terminated with si_code "
	<< info.si_code;
	} else if (info.si_status != 0) {
	LOG(INFO) << "Subprocess " << info.si_pid
	<< " exited with si_status: " << info.si_status;
	}

	if (!record->stdout_str.empty()) {
	LOG(INFO) << "Subprocess output:\n" << record->stdout_str;
	}
	if (!record->callback.is_null()) {
	record->callback.Run(info.si_status, record->stdout_str);
	}
	// Release and close all the pipes after calling the callback so our
	// redirected pipes are still alive. Releasing the process first makes
	// Reset(0) not attempt to kill the process, which is already a zombie at this
	// point.
	record->proc.Release();
	record->proc.Reset(0);

	subprocess_records_.erase(pid_record);
	}

	pid_t Subprocess::Exec(const vector<string>& cmd,
	const ExecCallback& callback) {
	return ExecFlags(cmd, kRedirectStderrToStdout, {}, callback);
	}

	pid_t Subprocess::ExecFlags(const vector<string>& cmd,
	uint32_t flags,
	const vector<int>& output_pipes,
	const ExecCallback& callback) {
	unique_ptr<SubprocessRecord> record(new SubprocessRecord(callback));

	if (!LaunchProcess(cmd, flags, output_pipes, &record->proc)) {
	LOG(ERROR) << "Failed to launch subprocess";
	return 0;
	}

	pid_t pid = record->proc.pid();
	CHECK(process_reaper_.WatchForChild(
	FROM_HERE,
	pid,
	base::Bind(&Subprocess::ChildExitedCallback, base::Unretained(this))));

	record->stdout_fd = record->proc.GetPipe(STDOUT_FILENO);
	// Capture the subprocess output. Make our end of the pipe non-blocking.
	int fd_flags = fcntl(record->stdout_fd, F_GETFL, 0) \| O_NONBLOCK;
	if (HANDLE_EINTR(fcntl(record->stdout_fd, F_SETFL, fd_flags)) < 0) {
	LOG(ERROR) << "Unable to set non-blocking I/O mode on fd "
	<< record->stdout_fd << ".";
	}

	record->stdout_controller = base::FileDescriptorWatcher::WatchReadable(
	record->stdout_fd,
	base::BindRepeating(&Subprocess::OnStdoutReady, record.get()));

	subprocess_records_[pid] = std::move(record);
	return pid;
	}

	bool WaitForProcessGroup(pid_t pid, std::chrono::milliseconds timeout) {
	using std::chrono::system_clock;
	auto start = system_clock::now();
	do {
	pid_t w = waitpid(-pid, nullptr, WNOHANG);
	if (w < 0) {
	// When all of the child process with this process group ID exits, waitpid
	// will return ECHILD. Until that point, keep callilng waitpid() as there
	// might be multiple child processes with the same process group id.
	if (errno == ECHILD) {
	LOG(INFO) << "All processes with process group id " << pid << " exited";
	return true;
	}
	PLOG(ERROR) << "Waitpid returned " << w;
	return false;
	}
	usleep(100);
	} while ((system_clock::now() - start) <= timeout);
	LOG(INFO) << "process group " << pid << " did not exit in " << timeout.count()
	<< " milliseconds";
	return false;
	}

	void Subprocess::KillExec(pid_t pid) {
	using namespace std::chrono_literals;
	auto pid_record = subprocess_records_.find(pid);
	if (pid_record == subprocess_records_.end())
	return;
	pid_record->second->callback.Reset();
	// We don't care about output/return code, so we use SIGKILL here to ensure it
	// will be killed, SIGTERM might lead to leaked subprocess.
	CHECK_EQ(pid_record->second->proc.pid(), pid);
	if (kill(-pid, SIGKILL) != 0) {
	PLOG(WARNING) << "Failed to kill subprocess group " << pid;
	}
	WaitForProcessGroup(pid, 5000ms);
	// Release the pid now so we don't try to kill it if Subprocess is destroyed
	// before the corresponding ChildExitedCallback() is called.
	pid_record->second->proc.Release();
	if (subprocess_records_.count(pid)) {
	siginfo_t info;
	info.si_code = CLD_KILLED;
	info.si_status = SIGKILL;
	info.si_pid = pid;
	ChildExitedCallback(info);
	}
	}

	int Subprocess::GetPipeFd(pid_t pid, int fd) const {
	auto pid_record = subprocess_records_.find(pid);
	if (pid_record == subprocess_records_.end())
	return -1;
	return pid_record->second->proc.GetPipe(fd);
	}

	bool Subprocess::SynchronousExec(const vector<string>& cmd,
	int* return_code,
	string* stdout_str,
	string* stderr_str) {
	// The default for \|SynchronousExec\| is to use \|kSearchPath\| since the code
	// relies on that.
	return SynchronousExecFlags(
	cmd, kSearchPath, return_code, stdout_str, stderr_str);
	}

	bool Subprocess::SynchronousExecFlags(const vector<string>& cmd,
	uint32_t flags,
	int* return_code,
	string* stdout_str,
	string* stderr_str) {
	brillo::ProcessImpl proc;
	if (!LaunchProcess(cmd, flags, {STDERR_FILENO}, &proc)) {
	LOG(ERROR) << "Failed to launch subprocess";
	return false;
	}

	if (stdout_str) {
	stdout_str->clear();
	}
	if (stderr_str) {
	stderr_str->clear();
	}

	// Read from both stdout and stderr individually.
	int stdout_fd = proc.GetPipe(STDOUT_FILENO);
	int stderr_fd = proc.GetPipe(STDERR_FILENO);
	vector<char> buffer(32 * 1024);
	bool stdout_closed = false, stderr_closed = false;
	while (!stdout_closed \|\| !stderr_closed) {
	if (!stdout_closed) {
	int rc = HANDLE_EINTR(read(stdout_fd, buffer.data(), buffer.size()));
	if (rc <= 0) {
	stdout_closed = true;
	if (rc < 0)
	PLOG(ERROR) << "Reading from child's stdout";
	} else if (stdout_str != nullptr) {
	stdout_str->append(buffer.data(), rc);
	}
	}

	if (!stderr_closed) {
	int rc = HANDLE_EINTR(read(stderr_fd, buffer.data(), buffer.size()));
	if (rc <= 0) {
	stderr_closed = true;
	if (rc < 0)
	PLOG(ERROR) << "Reading from child's stderr";
	} else if (stderr_str != nullptr) {
	stderr_str->append(buffer.data(), rc);
	}
	}
	}

	// At this point, the subprocess already closed the output, so we only need to
	// wait for it to finish.
	int proc_return_code = proc.Wait();
	if (return_code)
	*return_code = proc_return_code;
	return proc_return_code != brillo::Process::kErrorExitStatus;
	}

	void Subprocess::FlushBufferedLogsAtExit() {
	if (!subprocess_records_.empty()) {
	LOG(INFO) << "We are exiting, but there are still in flight subprocesses!";
	for (auto& pid_record : subprocess_records_) {
	SubprocessRecord* record = pid_record.second.get();
	// Make sure we read any remaining process output.
	OnStdoutReady(record);
	if (!record->stdout_str.empty()) {
	LOG(INFO) << "Subprocess(" << pid_record.first << ") output:\n"
	<< record->stdout_str;
	}
	}
	}
	}

	Subprocess* Subprocess::subprocess_singleton_ = nullptr;

	} // namespace chromeos_update_engine