#include "folly/Conv.h"
#include "folly/Exception.h"
+#include "folly/FileUtil.h"
#include "folly/ScopeGuard.h"
#include "folly/String.h"
#include "folly/io/Cursor.h"
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
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;
+};
+
+void childError(int errFd, int errCode, int errnoValue) FOLLY_NORETURN;
+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];
+ int r = ::pipe(errFds);
+ checkUnixError(r, "pipe");
+ SCOPE_EXIT {
+ CHECK_ERR(::close(errFds[0]));
+ if (errFds[1] >= 0) {
+ CHECK_ERR(::close(errFds[1]));
+ }
+ };
+ // Ask the child to close the read end of the error pipe.
+ options.fdActions_[errFds[0]] = CLOSE;
+ // 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.
+ r = fcntl(errFds[1], F_SETFD, FD_CLOEXEC);
+ checkUnixError(r, "set FD_CLOEXEC");
+
+ // 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;
-
- // If we throw, don't leak file descriptors
- auto guard = makeGuard([&] {
+ // 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));
}
- for (auto& p : this->pipes_) {
- CHECK_ERR(::close(p.parentFd));
- }
- });
+ };
+ int r;
for (auto& p : options.fdActions_) {
if (p.second == PIPE_IN || p.second == PIPE_OUT) {
int fds[2];
- int r = ::pipe(fds);
+ r = ::pipe(fds);
checkUnixError(r, "pipe");
PipeInfo pinfo;
pinfo.direction = p.second;
//
// 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
+ };
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);
+ if (errnoValue != 0) {
+ childError(errFd, kChildFailure, errnoValue);
}
- // Unblock signals; restore signal mask.
- int r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
- if (r != 0) _exit(kChildFailure);
-
- runChild(executable, argVec, envVec, options);
- // This should never return, but there's nothing else we can do here.
- _exit(kExecFailure);
- }
- // 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!
- r = pthread_sigmask(SIG_SETMASK, &oldSignals, nullptr);
- CHECK_EQ(r, 0) << "pthread_sigmask: " << errnoStr(r); // shouldn't fail
- checkUnixError(pid, savedErrno, "vfork");
-
- // Child is alive. We can't throw any more, as we can't figure out
- // what to do with the child.
- guard.dismiss();
- pid_ = pid;
- returnCode_ = ProcessReturnCode(RV_RUNNING);
- // Parent work, post-fork: close child's ends of pipes; closing them
- // shouldn't fail.
- for (int f : childFds) {
- CHECK_ERR(::close(f));
+ errnoValue = runChild(executable, argVec, envVec, options);
+ // If we get here, exec() failed.
+ childError(errFd, kExecFailure, errnoValue);
}
-}
+ // In parent. Make sure vfork() succeeded.
+ checkUnixError(pid, errno, "vfork");
-namespace {
-
-// Checked version of close() to use in the child: _exit(126) on error
-void childClose(int fd) {
- int r = ::close(fd);
- if (r == -1) _exit(kChildFailure);
-}
-
-// Checked version of dup2() to use in the child: _exit(126) on error
-void childDup2(int oldfd, int newfd) {
- int r = ::dup2(oldfd, newfd);
- if (r == -1) _exit(kChildFailure);
+ // 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);
}
-} // namespace
+int Subprocess::prepareChild(const Options& options,
+ const sigset_t* sigmask) const {
+ // While all signals are blocked, we must reset their
+ // dispositions to default.
+ for (int sig = 1; sig < NSIG; ++sig) {
+ ::signal(sig, SIG_DFL);
+ }
+ // 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);
+ r = ::close(p.parentFd);
+ if (r == -1) {
+ return errno;
+ }
}
// Close all fds that we're supposed to close.
if (p.second == CLOSE) {
::close(p.first);
} else {
- childDup2(p.second, p.first);
+ r = ::dup2(p.second, p.first);
+ if (r == -1) {
+ return errno;
+ }
}
}
// Opt to receive signal on parent death, if requested
if (options.parentDeathSignal_ != 0) {
- int r = prctl(PR_SET_PDEATHSIG, options.parentDeathSignal_, 0, 0, 0);
+ r = prctl(PR_SET_PDEATHSIG, options.parentDeathSignal_, 0, 0, 0);
if (r == -1) {
- _exit(kChildFailure);
+ return errno;
}
}
+ return 0;
+}
+
+int Subprocess::runChild(const char* executable,
+ char** argv, char** env,
+ const Options& options) const {
// Now, finally, exec.
int r;
if (options.usePath_) {
} 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();
+
+ // Throw to signal the error
+ throw SubprocessSpawnError(executable, info.errCode, info.errnoValue);
}
ProcessReturnCode Subprocess::poll() {
int rawStatus_;
};
+/**
+ * Base exception thrown by the Subprocess methods.
+ */
+class SubprocessError : public std::exception {};
+
/**
* Exception thrown by *Checked methods of Subprocess.
*/
-class CalledProcessError : public std::exception {
+class CalledProcessError : public SubprocessError {
public:
explicit CalledProcessError(ProcessReturnCode rc);
~CalledProcessError() throw() { }
std::string what_;
};
+/**
+ * Exception thrown if the subprocess cannot be started.
+ */
+class SubprocessSpawnError : public SubprocessError {
+ public:
+ SubprocessSpawnError(const char* executable, int errCode, int errnoValue);
+ ~SubprocessSpawnError() throw() {}
+ const char* what() const throw() FOLLY_OVERRIDE { return what_.c_str(); }
+ int errnoValue() const { return errnoValue_; }
+
+ private:
+ int errnoValue_;
+ std::string what_;
+};
+
/**
* Subprocess.
*/
static const int RV_RUNNING = ProcessReturnCode::RV_RUNNING;
static const int RV_NOT_STARTED = ProcessReturnCode::RV_NOT_STARTED;
+ // spawn() sets up a pipe to read errors from the child,
+ // then calls spawnInternal() to do the bulk of the work. Once
+ // spawnInternal() returns it reads the error pipe to see if the child
+ // encountered any errors.
void spawn(
std::unique_ptr<const char*[]> argv,
const char* executable,
const Options& options,
const std::vector<std::string>* env);
+ void spawnInternal(
+ std::unique_ptr<const char*[]> argv,
+ const char* executable,
+ Options& options,
+ const std::vector<std::string>* env,
+ int errFd);
- // Action to run in child.
+ // Actions to run in child.
// Note that this runs after vfork(), so tread lightly.
- void runChild(const char* executable, char** argv, char** env,
- const Options& options) const;
+ // Returns 0 on success, or an errno value on failure.
+ int prepareChild(const Options& options, const sigset_t* sigmask) const;
+ int runChild(const char* executable, char** argv, char** env,
+ const Options& options) const;
+
+ /**
+ * Read from the error pipe, and throw SubprocessSpawnError if the child
+ * failed before calling exec().
+ */
+ void readChildErrorPipe(int pfd, const char* executable);
/**
* Close all file descriptors.
#include "folly/Subprocess.h"
#include <unistd.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <boost/container/flat_set.hpp>
#include <glog/logging.h>
#include <gtest/gtest.h>
+#include "folly/Exception.h"
#include "folly/Format.h"
#include "folly/experimental/Gen.h"
#include "folly/experimental/FileGen.h"
EXPECT_THROW(proc.waitChecked(), CalledProcessError);
}
+#define EXPECT_SPAWN_ERROR(err, errMsg, cmd, ...) \
+ do { \
+ try { \
+ Subprocess proc(std::vector<std::string>{ (cmd), ## __VA_ARGS__ }); \
+ ADD_FAILURE() << "expected an error when running " << (cmd); \
+ } catch (const SubprocessSpawnError& ex) { \
+ EXPECT_EQ((err), ex.errnoValue()); \
+ if (StringPiece(ex.what()).find(errMsg) == StringPiece::npos) { \
+ ADD_FAILURE() << "failed to find \"" << (errMsg) << \
+ "\" in exception: \"" << ex.what() << "\""; \
+ } \
+ } \
+ } while (0)
+
TEST(SimpleSubprocessTest, ExecFails) {
- Subprocess proc(std::vector<std::string>{ "/no/such/file" });
- EXPECT_EQ(127, proc.wait().exitStatus());
+ EXPECT_SPAWN_ERROR(ENOENT, "failed to execute /no/such/file:",
+ "/no/such/file");
+ EXPECT_SPAWN_ERROR(EACCES, "failed to execute /etc/passwd:",
+ "/etc/passwd");
+ EXPECT_SPAWN_ERROR(ENOTDIR, "failed to execute /etc/passwd/not/a/file:",
+ "/etc/passwd/not/a/file");
}
TEST(SimpleSubprocessTest, ShellExitsSuccesssfully) {
EXPECT_EQ(1, proc.wait().exitStatus());
}
+namespace {
+boost::container::flat_set<int> getOpenFds() {
+ auto pid = getpid();
+ auto dirname = to<std::string>("/proc/", pid, "/fd");
+
+ boost::container::flat_set<int> fds;
+ for (fs::directory_iterator it(dirname);
+ it != fs::directory_iterator();
+ ++it) {
+ int fd = to<int>(it->path().filename().native());
+ fds.insert(fd);
+ }
+ return fds;
+}
+
+template<class Runnable>
+void checkFdLeak(const Runnable& r) {
+ // Get the currently open fds. Check that they are the same both before and
+ // after calling the specified function. We read the open fds from /proc.
+ // (If we wanted to work even on systems that don't have /proc, we could
+ // perhaps create and immediately close a socket both before and after
+ // running the function, and make sure we got the same fd number both times.)
+ auto fdsBefore = getOpenFds();
+ r();
+ auto fdsAfter = getOpenFds();
+ EXPECT_EQ(fdsAfter.size(), fdsBefore.size());
+}
+}
+
+// Make sure Subprocess doesn't leak any file descriptors
+TEST(SimpleSubprocessTest, FdLeakTest) {
+ // Normal execution
+ checkFdLeak([] {
+ Subprocess proc("true");
+ EXPECT_EQ(0, proc.wait().exitStatus());
+ });
+ // Normal execution with pipes
+ checkFdLeak([] {
+ Subprocess proc("echo foo; echo bar >&2",
+ Subprocess::pipeStdout() | Subprocess::pipeStderr());
+ auto p = proc.communicate(Subprocess::readStdout() |
+ Subprocess::readStderr());
+ EXPECT_EQ("foo\n", p.first);
+ EXPECT_EQ("bar\n", p.second);
+ proc.waitChecked();
+ });
+
+ // Test where the exec call fails()
+ checkFdLeak([] {
+ EXPECT_SPAWN_ERROR(ENOENT, "failed to execute", "/no/such/file");
+ });
+ // Test where the exec call fails() with pipes
+ checkFdLeak([] {
+ try {
+ Subprocess proc(std::vector<std::string>({"/no/such/file"}),
+ Subprocess::pipeStdout().stderr(Subprocess::PIPE));
+ ADD_FAILURE() << "expected an error when running /no/such/file";
+ } catch (const SubprocessSpawnError& ex) {
+ EXPECT_EQ(ENOENT, ex.errnoValue());
+ }
+ });
+}
+
TEST(ParentDeathSubprocessTest, ParentDeathSignal) {
// Find out where we are.
static constexpr size_t pathLength = 2048;
EXPECT_EQ(std::string::npos, p.first.find_first_not_of('X'));
proc.waitChecked();
}
-
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