/*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#include "folly/Subprocess.h"
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <folly/Subprocess.h>
+
+#if __linux__
+#include <sys/prctl.h>
+#endif
#include <fcntl.h>
#include <poll.h>
+
#include <unistd.h>
-#include <wait.h>
#include <array>
#include <algorithm>
#include <glog/logging.h>
-#include "folly/Conv.h"
-#include "folly/ScopeGuard.h"
-#include "folly/String.h"
-#include "folly/experimental/io/Cursor.h"
+#include <folly/Conv.h>
+#include <folly/Exception.h>
+#include <folly/ScopeGuard.h>
+#include <folly/String.h>
+#include <folly/io/Cursor.h>
extern char** environ;
+constexpr int kExecFailure = 127;
+constexpr int kChildFailure = 126;
+
namespace folly {
ProcessReturnCode::State ProcessReturnCode::state() const {
"Invalid ProcessReturnCode: ", rawStatus_));
}
-void ProcessReturnCode::enforce(State s) const {
- if (state() != s) {
- throw std::logic_error(to<std::string>("Invalid state ", s));
+void ProcessReturnCode::enforce(State expected) const {
+ State s = state();
+ if (s != expected) {
+ throw std::logic_error(to<std::string>(
+ "Bad use of ProcessReturnCode; state is ", s, " expected ", expected
+ ));
}
}
what_(returnCode_.str()) {
}
+SubprocessSpawnError::SubprocessSpawnError(const char* executable,
+ int errCode,
+ int errnoValue)
+ : errnoValue_(errnoValue),
+ what_(to<std::string>(errCode == kExecFailure ?
+ "failed to execute " :
+ "error preparing to execute ",
+ executable, ": ", errnoStr(errnoValue))) {
+}
+
namespace {
// Copy pointers to the given strings in a format suitable for posix_spawn
return d;
}
-// Helper to throw std::system_error
-void throwSystemError(int err, const char* msg) __attribute__((noreturn));
-void throwSystemError(int err, const char* msg) {
- throw std::system_error(err, std::system_category(), msg);
-}
-
-// Helper to throw std::system_error from errno
-void throwSystemError(const char* msg) __attribute__((noreturn));
-void throwSystemError(const char* msg) {
- throwSystemError(errno, msg);
-}
-
-// Check a Posix return code (0 on success, error number on error), throw
-// on error.
-void checkPosixError(int err, const char* msg) {
- if (err != 0) {
- throwSystemError(err, msg);
- }
-}
-
-// Check a traditional Uinx return code (-1 and sets errno on error), throw
-// on error.
-void checkUnixError(ssize_t ret, const char* msg) {
- if (ret == -1) {
- throwSystemError(msg);
- }
-}
-void checkUnixError(ssize_t ret, int savedErrno, const char* msg) {
- if (ret == -1) {
- throwSystemError(savedErrno, msg);
- }
-}
-
// Check a wait() status, throw on non-successful
void checkStatus(ProcessReturnCode returnCode) {
if (returnCode.state() != ProcessReturnCode::EXITED ||
Subprocess::~Subprocess() {
CHECK_NE(returnCode_.state(), ProcessReturnCode::RUNNING)
<< "Subprocess destroyed without reaping child";
+ closeAll();
}
namespace {
void closeChecked(int fd) {
checkUnixError(::close(fd), "close");
}
+
+struct ChildErrorInfo {
+ int errCode;
+ int errnoValue;
+};
+
+FOLLY_NORETURN void childError(int errFd, int errCode, int errnoValue);
+void childError(int errFd, int errCode, int errnoValue) {
+ ChildErrorInfo info = {errCode, errnoValue};
+ // Write the error information over the pipe to our parent process.
+ // We can't really do anything else if this write call fails.
+ writeNoInt(errFd, &info, sizeof(info));
+ // exit
+ _exit(errCode);
+}
+
} // namespace
void Subprocess::closeAll() {
// Make a copy, we'll mutate options
Options options(optionsIn);
+ // On error, close all of the pipes_
+ auto pipesGuard = makeGuard([&] {
+ for (auto& p : this->pipes_) {
+ CHECK_ERR(::close(p.parentFd));
+ }
+ });
+
+ // Create a pipe to use to receive error information from the child,
+ // in case it fails before calling exec()
+ int errFds[2];
+#if FOLLY_HAVE_PIPE2
+ checkUnixError(::pipe2(errFds, O_CLOEXEC), "pipe2");
+#else
+ checkUnixError(::pipe(errFds), "pipe");
+#endif
+ SCOPE_EXIT {
+ CHECK_ERR(::close(errFds[0]));
+ if (errFds[1] >= 0) {
+ CHECK_ERR(::close(errFds[1]));
+ }
+ };
+
+#if !FOLLY_HAVE_PIPE2
+ // Ask the child to close the read end of the error pipe.
+ checkUnixError(fcntl(errFds[0], F_SETFD, FD_CLOEXEC), "set FD_CLOEXEC");
+ // Set the close-on-exec flag on the write side of the pipe.
+ // This way the pipe will be closed automatically in the child if execve()
+ // succeeds. If the exec fails the child can write error information to the
+ // pipe.
+ checkUnixError(fcntl(errFds[1], F_SETFD, FD_CLOEXEC), "set FD_CLOEXEC");
+#endif
+
+ // Perform the actual work of setting up pipes then forking and
+ // executing the child.
+ spawnInternal(std::move(argv), executable, options, env, errFds[1]);
+
+ // After spawnInternal() returns the child is alive. We have to be very
+ // careful about throwing after this point. We are inside the constructor,
+ // so if we throw the Subprocess object will have never existed, and the
+ // destructor will never be called.
+ //
+ // We should only throw if we got an error via the errFd, and we know the
+ // child has exited and can be immediately waited for. In all other cases,
+ // we have no way of cleaning up the child.
+
+ // Close writable side of the errFd pipe in the parent process
+ CHECK_ERR(::close(errFds[1]));
+ errFds[1] = -1;
+
+ // Read from the errFd pipe, to tell if the child ran into any errors before
+ // calling exec()
+ readChildErrorPipe(errFds[0], executable);
+
+ // We have fully succeeded now, so release the guard on pipes_
+ pipesGuard.dismiss();
+}
+
+void Subprocess::spawnInternal(
+ std::unique_ptr<const char*[]> argv,
+ const char* executable,
+ Options& options,
+ const std::vector<std::string>* env,
+ int errFd) {
// Parent work, pre-fork: create pipes
std::vector<int> childFds;
+ // Close all of the childFds as we leave this scope
+ SCOPE_EXIT {
+ // These are only pipes, closing them shouldn't fail
+ for (int cfd : childFds) {
+ CHECK_ERR(::close(cfd));
+ }
+ };
+
+ int r;
for (auto& p : options.fdActions_) {
if (p.second == PIPE_IN || p.second == PIPE_OUT) {
int fds[2];
- int r = ::pipe(fds);
+ // We're setting both ends of the pipe as close-on-exec. The child
+ // doesn't need to reset the flag on its end, as we always dup2() the fd,
+ // and dup2() fds don't share the close-on-exec flag.
+#if FOLLY_HAVE_PIPE2
+ r = ::pipe2(fds, O_CLOEXEC);
+ checkUnixError(r, "pipe2");
+#else
+ r = ::pipe(fds);
checkUnixError(r, "pipe");
+ r = fcntl(fds[0], F_SETFD, FD_CLOEXEC);
+ checkUnixError(r, "set FD_CLOEXEC");
+ r = fcntl(fds[1], F_SETFD, FD_CLOEXEC);
+ checkUnixError(r, "set FD_CLOEXEC");
+#endif
PipeInfo pinfo;
pinfo.direction = p.second;
int cfd;
//
// The parent also unblocks all signals as soon as vfork() returns.
sigset_t allBlocked;
- int r = ::sigfillset(&allBlocked);
+ r = sigfillset(&allBlocked);
checkUnixError(r, "sigfillset");
sigset_t oldSignals;
+
r = pthread_sigmask(SIG_SETMASK, &allBlocked, &oldSignals);
checkPosixError(r, "pthread_sigmask");
+ SCOPE_EXIT {
+ // Restore signal mask
+ r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
+ CHECK_EQ(r, 0) << "pthread_sigmask: " << errnoStr(r); // shouldn't fail
+ };
+ // Call c_str() here, as it's not necessarily safe after fork.
+ const char* childDir =
+ options.childDir_.empty() ? nullptr : options.childDir_.c_str();
pid_t pid = vfork();
if (pid == 0) {
- // While all signals are blocked, we must reset their
- // dispositions to default.
- for (int sig = 1; sig < NSIG; ++sig) {
- ::signal(sig, SIG_DFL);
+ int errnoValue = prepareChild(options, &oldSignals, childDir);
+ if (errnoValue != 0) {
+ childError(errFd, kChildFailure, errnoValue);
}
- // Unblock signals; restore signal mask.
- int r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
- if (r != 0) abort();
- runChild(executable, argVec, envVec, options);
- // This should never return, but there's nothing else we can do here.
- abort();
+ errnoValue = runChild(executable, argVec, envVec, options);
+ // If we get here, exec() failed.
+ childError(errFd, kExecFailure, errnoValue);
}
- // In parent. We want to restore the signal mask even if vfork fails,
- // so we'll save errno here, restore the signal mask, and only then
- // throw.
- int savedErrno = errno;
-
- // Restore signal mask; do this even if vfork fails!
- // We only check for errors from pthread_sigmask after we recorded state
- // that the child is alive, so we know to reap it.
- r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
- checkUnixError(pid, savedErrno, "vfork");
+ // In parent. Make sure vfork() succeeded.
+ checkUnixError(pid, errno, "vfork");
- // Child is alive
+ // Child is alive. We have to be very careful about throwing after this
+ // point. We are inside the constructor, so if we throw the Subprocess
+ // object will have never existed, and the destructor will never be called.
+ //
+ // We should only throw if we got an error via the errFd, and we know the
+ // child has exited and can be immediately waited for. In all other cases,
+ // we have no way of cleaning up the child.
pid_ = pid;
returnCode_ = ProcessReturnCode(RV_RUNNING);
-
- // Parent work, post-fork: close child's ends of pipes
- for (int f : childFds) {
- closeChecked(f);
- }
-
- checkPosixError(r, "pthread_sigmask");
}
-namespace {
-
-// Checked version of close() to use in the child: abort() on error
-void childClose(int fd) {
- int r = ::close(fd);
- if (r == -1) abort();
-}
-
-// Checked version of dup2() to use in the child: abort() on error
-void childDup2(int oldfd, int newfd) {
- int r = ::dup2(oldfd, newfd);
- if (r == -1) abort();
-}
+int Subprocess::prepareChild(const Options& options,
+ const sigset_t* sigmask,
+ const char* childDir) const {
+ // While all signals are blocked, we must reset their
+ // dispositions to default.
+ for (int sig = 1; sig < NSIG; ++sig) {
+ ::signal(sig, SIG_DFL);
+ }
-} // namespace
+ {
+ // Unblock signals; restore signal mask.
+ int r = pthread_sigmask(SIG_SETMASK, sigmask, nullptr);
+ if (r != 0) {
+ return r; // pthread_sigmask() returns an errno value
+ }
+ }
-void Subprocess::runChild(const char* executable,
- char** argv, char** env,
- const Options& options) const {
- // Close parent's ends of all pipes
- for (auto& p : pipes_) {
- childClose(p.parentFd);
+ // Change the working directory, if one is given
+ if (childDir) {
+ if (::chdir(childDir) == -1) {
+ return errno;
+ }
}
+ // We don't have to explicitly close the parent's end of all pipes,
+ // as they all have the FD_CLOEXEC flag set and will be closed at
+ // exec time.
+
// Close all fds that we're supposed to close.
- // Note that we're ignoring errors here, in case some of these
- // fds were set to close on exec.
for (auto& p : options.fdActions_) {
if (p.second == CLOSE) {
- ::close(p.first);
- } else {
- childDup2(p.second, p.first);
+ if (::close(p.first) == -1) {
+ return errno;
+ }
+ } else if (p.second != p.first) {
+ if (::dup2(p.second, p.first) == -1) {
+ return errno;
+ }
}
}
}
}
+#if __linux__
+ // Opt to receive signal on parent death, if requested
+ if (options.parentDeathSignal_ != 0) {
+ if (prctl(PR_SET_PDEATHSIG, options.parentDeathSignal_, 0, 0, 0) == -1) {
+ return errno;
+ }
+ }
+#endif
+
+ return 0;
+}
+
+int Subprocess::runChild(const char* executable,
+ char** argv, char** env,
+ const Options& options) const {
// Now, finally, exec.
- int r;
if (options.usePath_) {
::execvp(executable, argv);
} else {
::execve(executable, argv, env);
}
+ return errno;
+}
+
+void Subprocess::readChildErrorPipe(int pfd, const char* executable) {
+ ChildErrorInfo info;
+ auto rc = readNoInt(pfd, &info, sizeof(info));
+ if (rc == 0) {
+ // No data means the child executed successfully, and the pipe
+ // was closed due to the close-on-exec flag being set.
+ return;
+ } else if (rc != sizeof(ChildErrorInfo)) {
+ // An error occurred trying to read from the pipe, or we got a partial read.
+ // Neither of these cases should really occur in practice.
+ //
+ // We can't get any error data from the child in this case, and we don't
+ // know if it is successfully running or not. All we can do is to return
+ // normally, as if the child executed successfully. If something bad
+ // happened the caller should at least get a non-normal exit status from
+ // the child.
+ LOG(ERROR) << "unexpected error trying to read from child error pipe " <<
+ "rc=" << rc << ", errno=" << errno;
+ return;
+ }
+
+ // We got error data from the child. The child should exit immediately in
+ // this case, so wait on it to clean up.
+ wait();
- // If we're here, something's wrong.
- abort();
+ // Throw to signal the error
+ throw SubprocessSpawnError(executable, info.errCode, info.errnoValue);
}
ProcessReturnCode Subprocess::poll() {
checkUnixError(found, "waitpid");
DCHECK_EQ(found, pid_);
returnCode_ = ProcessReturnCode(status);
+ pid_ = -1;
return returnCode_;
}
checkUnixError(r, "kill");
}
-namespace {
-void setNonBlocking(int fd) {
- int flags = ::fcntl(fd, F_GETFL);
- checkUnixError(flags, "fcntl");
- int r = ::fcntl(fd, F_SETFL, flags | O_NONBLOCK);
- checkUnixError(r, "fcntl");
+pid_t Subprocess::pid() const {
+ return pid_;
}
+namespace {
+
std::pair<const uint8_t*, size_t> queueFront(const IOBufQueue& queue) {
auto* p = queue.front();
if (!p) return std::make_pair(nullptr, 0);
return true; // EOF
}
- ssize_t n;
- do {
- n = ::write(fd, p.first, p.second);
- } while (n == -1 && errno == EINTR);
+ ssize_t n = writeNoInt(fd, p.first, p.second);
if (n == -1 && errno == EAGAIN) {
return false;
}
bool handleRead(int fd, IOBufQueue& queue) {
for (;;) {
auto p = queue.preallocate(100, 65000);
- ssize_t n;
- do {
- n = ::read(fd, p.first, p.second);
- } while (n == -1 && errno == EINTR);
+ ssize_t n = readNoInt(fd, p.first, p.second);
if (n == -1 && errno == EAGAIN) {
return false;
}
static std::unique_ptr<char[]> buf(new char[bufSize]);
for (;;) {
- ssize_t n;
- do {
- n = ::read(fd, buf.get(), bufSize);
- } while (n == -1 && errno == EINTR);
+ ssize_t n = readNoInt(fd, buf.get(), bufSize);
if (n == -1 && errno == EAGAIN) {
return false;
}
} // namespace
std::pair<std::string, std::string> Subprocess::communicate(
- const CommunicateFlags& flags,
- StringPiece data) {
- IOBufQueue dataQueue;
- dataQueue.wrapBuffer(data.data(), data.size());
+ StringPiece input) {
+ IOBufQueue inputQueue;
+ inputQueue.wrapBuffer(input.data(), input.size());
- auto outQueues = communicateIOBuf(flags, std::move(dataQueue));
+ auto outQueues = communicateIOBuf(std::move(inputQueue));
auto outBufs = std::make_pair(outQueues.first.move(),
outQueues.second.move());
std::pair<std::string, std::string> out;
}
std::pair<IOBufQueue, IOBufQueue> Subprocess::communicateIOBuf(
- const CommunicateFlags& flags,
- IOBufQueue data) {
+ IOBufQueue input) {
+ // If the user supplied a non-empty input buffer, make sure
+ // that stdin is a pipe so we can write the data.
+ if (!input.empty()) {
+ // findByChildFd() will throw std::invalid_argument if no pipe for
+ // STDIN_FILENO exists
+ findByChildFd(STDIN_FILENO);
+ }
+
std::pair<IOBufQueue, IOBufQueue> out;
- auto readCallback = [&] (int pfd, int cfd) {
- if (cfd == 1 && flags.readStdout_) {
+ auto readCallback = [&] (int pfd, int cfd) -> bool {
+ if (cfd == STDOUT_FILENO) {
return handleRead(pfd, out.first);
- } else if (cfd == 2 && flags.readStderr_) {
+ } else if (cfd == STDERR_FILENO) {
return handleRead(pfd, out.second);
} else {
// Don't close the file descriptor, the child might not like SIGPIPE,
}
};
- auto writeCallback = [&] (int pfd, int cfd) {
- if (cfd == 0 && flags.writeStdin_) {
- return handleWrite(pfd, data);
+ auto writeCallback = [&] (int pfd, int cfd) -> bool {
+ if (cfd == STDIN_FILENO) {
+ return handleWrite(pfd, input);
} else {
// If we don't want to write to this fd, just close it.
- return false;
+ return true;
}
};
pfd.fd = p.parentFd;
// Yes, backwards, PIPE_IN / PIPE_OUT are defined from the
// child's point of view.
- pfd.events = (p.direction == PIPE_IN ? POLLOUT : POLLIN);
+ if (!p.enabled) {
+ // Still keeping fd in watched set so we get notified of POLLHUP /
+ // POLLERR
+ pfd.events = 0;
+ } else if (p.direction == PIPE_IN) {
+ pfd.events = POLLOUT;
+ } else {
+ pfd.events = POLLIN;
+ }
fds.push_back(pfd);
}
}
}
- if (events & POLLIN) {
+ // Call read callback on POLLHUP, to give it a chance to read (and act
+ // on) end of file
+ if (events & (POLLIN | POLLHUP)) {
DCHECK(!(events & POLLOUT));
if (readCallback(p.parentFd, p.childFd)) {
toClose.push_back(i);
}
}
+void Subprocess::enableNotifications(int childFd, bool enabled) {
+ pipes_[findByChildFd(childFd)].enabled = enabled;
+}
+
+bool Subprocess::notificationsEnabled(int childFd) const {
+ return pipes_[findByChildFd(childFd)].enabled;
+}
+
int Subprocess::findByChildFd(int childFd) const {
auto pos = std::lower_bound(
pipes_.begin(), pipes_.end(), childFd,
} // namespace
} // namespace folly
-
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