1 use io::{self, Error, ErrorKind};
2 use libc::{self, c_int, gid_t, pid_t, uid_t};
5 use sys::process::process_common::*;
8 ////////////////////////////////////////////////////////////////////////////////
10 ////////////////////////////////////////////////////////////////////////////////
13 pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
14 -> io::Result<(Process, StdioPipes)> {
15 const CLOEXEC_MSG_FOOTER: &[u8] = b"NOEX";
17 let envp = self.capture_env();
20 return Err(io::Error::new(ErrorKind::InvalidInput,
21 "nul byte found in provided data"));
24 let (ours, theirs) = self.setup_io(default, needs_stdin)?;
26 if let Some(ret) = self.posix_spawn(&theirs, envp.as_ref())? {
27 return Ok((ret, ours))
30 let (input, output) = sys::pipe::anon_pipe()?;
32 // Whatever happens after the fork is almost for sure going to touch or
33 // look at the environment in one way or another (PATH in `execvp` or
34 // accessing the `environ` pointer ourselves). Make sure no other thread
35 // is accessing the environment when we do the fork itself.
37 // Note that as soon as we're done with the fork there's no need to hold
38 // a lock any more because the parent won't do anything and the child is
39 // in its own process.
41 let _env_lock = sys::os::env_lock();
49 let err = self.do_exec(theirs, envp.as_ref());
50 let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
56 CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
57 CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
59 // pipe I/O up to PIPE_BUF bytes should be atomic, and then
60 // we want to be sure we *don't* run at_exit destructors as
61 // we're being torn down regardless
62 assert!(output.write(&bytes).is_ok());
69 let mut p = Process { pid: pid, status: None };
71 let mut bytes = [0; 8];
73 // loop to handle EINTR
75 match input.read(&mut bytes) {
76 Ok(0) => return Ok((p, ours)),
78 assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
79 "Validation on the CLOEXEC pipe failed: {:?}", bytes);
80 let errno = combine(&bytes[0.. 4]);
81 assert!(p.wait().is_ok(),
82 "wait() should either return Ok or panic");
83 return Err(Error::from_raw_os_error(errno))
85 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
87 assert!(p.wait().is_ok(),
88 "wait() should either return Ok or panic");
89 panic!("the CLOEXEC pipe failed: {:?}", e)
91 Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
92 assert!(p.wait().is_ok(),
93 "wait() should either return Ok or panic");
94 panic!("short read on the CLOEXEC pipe")
99 fn combine(arr: &[u8]) -> i32 {
100 let a = arr[0] as u32;
101 let b = arr[1] as u32;
102 let c = arr[2] as u32;
103 let d = arr[3] as u32;
105 ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
109 pub fn exec(&mut self, default: Stdio) -> io::Error {
110 let envp = self.capture_env();
113 return io::Error::new(ErrorKind::InvalidInput,
114 "nul byte found in provided data")
117 match self.setup_io(default, true) {
120 // Similar to when forking, we want to ensure that access to
121 // the environment is synchronized, so make sure to grab the
122 // environment lock before we try to exec.
123 let _lock = sys::os::env_lock();
125 self.do_exec(theirs, envp.as_ref())
132 // And at this point we've reached a special time in the life of the
133 // child. The child must now be considered hamstrung and unable to
134 // do anything other than syscalls really. Consider the following
137 // 1. Thread A of process 1 grabs the malloc() mutex
138 // 2. Thread B of process 1 forks(), creating thread C
139 // 3. Thread C of process 2 then attempts to malloc()
140 // 4. The memory of process 2 is the same as the memory of
141 // process 1, so the mutex is locked.
143 // This situation looks a lot like deadlock, right? It turns out
144 // that this is what pthread_atfork() takes care of, which is
145 // presumably implemented across platforms. The first thing that
146 // threads to *before* forking is to do things like grab the malloc
147 // mutex, and then after the fork they unlock it.
149 // Despite this information, libnative's spawn has been witnessed to
150 // deadlock on both macOS and FreeBSD. I'm not entirely sure why, but
151 // all collected backtraces point at malloc/free traffic in the
152 // child spawned process.
154 // For this reason, the block of code below should contain 0
155 // invocations of either malloc of free (or their related friends).
157 // As an example of not having malloc/free traffic, we don't close
158 // this file descriptor by dropping the FileDesc (which contains an
159 // allocation). Instead we just close it manually. This will never
160 // have the drop glue anyway because this code never returns (the
161 // child will either exec() or invoke libc::exit)
165 maybe_envp: Option<&CStringArray>
167 use sys::{self, cvt_r};
170 ($e:expr) => (match $e {
176 if let Some(fd) = stdio.stdin.fd() {
177 t!(cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO)));
179 if let Some(fd) = stdio.stdout.fd() {
180 t!(cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO)));
182 if let Some(fd) = stdio.stderr.fd() {
183 t!(cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO)));
186 if cfg!(not(any(target_os = "l4re"))) {
187 if let Some(u) = self.get_gid() {
188 t!(cvt(libc::setgid(u as gid_t)));
190 if let Some(u) = self.get_uid() {
191 // When dropping privileges from root, the `setgroups` call
192 // will remove any extraneous groups. If we don't call this,
193 // then even though our uid has dropped, we may still have
194 // groups that enable us to do super-user things. This will
195 // fail if we aren't root, so don't bother checking the
196 // return value, this is just done as an optimistic
197 // privilege dropping function.
198 let _ = libc::setgroups(0, ptr::null());
200 t!(cvt(libc::setuid(u as uid_t)));
203 if let Some(ref cwd) = *self.get_cwd() {
204 t!(cvt(libc::chdir(cwd.as_ptr())));
207 // emscripten has no signal support.
208 #[cfg(not(any(target_os = "emscripten")))]
211 // Reset signal handling so the child process starts in a
212 // standardized state. libstd ignores SIGPIPE, and signal-handling
213 // libraries often set a mask. Child processes inherit ignored
214 // signals and the signal mask from their parent, but most
215 // UNIX programs do not reset these things on their own, so we
216 // need to clean things up now to avoid confusing the program
217 // we're about to run.
218 let mut set: libc::sigset_t = mem::uninitialized();
219 if cfg!(target_os = "android") {
220 // Implementing sigemptyset allow us to support older Android
221 // versions. See the comment about Android and sig* functions in
223 libc::memset(&mut set as *mut _ as *mut _,
225 mem::size_of::<libc::sigset_t>());
227 t!(cvt(libc::sigemptyset(&mut set)));
229 t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set,
231 let ret = sys::signal(libc::SIGPIPE, libc::SIG_DFL);
232 if ret == libc::SIG_ERR {
233 return io::Error::last_os_error()
237 for callback in self.get_closures().iter_mut() {
241 // Although we're performing an exec here we may also return with an
242 // error from this function (without actually exec'ing) in which case we
243 // want to be sure to restore the global environment back to what it
244 // once was, ensuring that our temporary override, when free'd, doesn't
245 // corrupt our process's environment.
246 let mut _reset = None;
247 if let Some(envp) = maybe_envp {
248 struct Reset(*const *const libc::c_char);
250 impl Drop for Reset {
253 *sys::os::environ() = self.0;
258 _reset = Some(Reset(*sys::os::environ()));
259 *sys::os::environ() = envp.as_ptr();
262 libc::execvp(self.get_argv()[0], self.get_argv().as_ptr());
263 io::Error::last_os_error()
266 #[cfg(not(any(target_os = "macos", target_os = "freebsd",
267 all(target_os = "linux", target_env = "gnu"))))]
268 fn posix_spawn(&mut self, _: &ChildPipes, _: Option<&CStringArray>)
269 -> io::Result<Option<Process>>
274 // Only support platforms for which posix_spawn() can return ENOENT
276 #[cfg(any(target_os = "macos", target_os = "freebsd",
277 all(target_os = "linux", target_env = "gnu")))]
278 fn posix_spawn(&mut self, stdio: &ChildPipes, envp: Option<&CStringArray>)
279 -> io::Result<Option<Process>>
284 if self.get_gid().is_some() ||
285 self.get_uid().is_some() ||
286 self.env_saw_path() ||
287 self.get_closures().len() != 0 {
291 // Only glibc 2.24+ posix_spawn() supports returning ENOENT directly.
292 #[cfg(all(target_os = "linux", target_env = "gnu"))]
294 if let Some(version) = sys::os::glibc_version() {
295 if version < (2, 24) {
303 // Solaris and glibc 2.29+ can set a new working directory, and maybe
304 // others will gain this non-POSIX function too. We'll check for this
305 // weak symbol as soon as it's needed, so we can return early otherwise
306 // to do a manual chdir before exec.
308 fn posix_spawn_file_actions_addchdir_np(
309 *mut libc::posix_spawn_file_actions_t,
313 let addchdir = match self.get_cwd() {
314 Some(cwd) => match posix_spawn_file_actions_addchdir_np.get() {
315 Some(f) => Some((f, cwd)),
316 None => return Ok(None),
321 let mut p = Process { pid: 0, status: None };
323 struct PosixSpawnFileActions(libc::posix_spawn_file_actions_t);
325 impl Drop for PosixSpawnFileActions {
328 libc::posix_spawn_file_actions_destroy(&mut self.0);
333 struct PosixSpawnattr(libc::posix_spawnattr_t);
335 impl Drop for PosixSpawnattr {
338 libc::posix_spawnattr_destroy(&mut self.0);
344 let mut file_actions = PosixSpawnFileActions(mem::uninitialized());
345 let mut attrs = PosixSpawnattr(mem::uninitialized());
347 libc::posix_spawnattr_init(&mut attrs.0);
348 libc::posix_spawn_file_actions_init(&mut file_actions.0);
350 if let Some(fd) = stdio.stdin.fd() {
351 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
353 libc::STDIN_FILENO))?;
355 if let Some(fd) = stdio.stdout.fd() {
356 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
358 libc::STDOUT_FILENO))?;
360 if let Some(fd) = stdio.stderr.fd() {
361 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
363 libc::STDERR_FILENO))?;
365 if let Some((f, cwd)) = addchdir {
366 cvt(f(&mut file_actions.0, cwd.as_ptr()))?;
369 let mut set: libc::sigset_t = mem::uninitialized();
370 cvt(libc::sigemptyset(&mut set))?;
371 cvt(libc::posix_spawnattr_setsigmask(&mut attrs.0,
373 cvt(libc::sigaddset(&mut set, libc::SIGPIPE))?;
374 cvt(libc::posix_spawnattr_setsigdefault(&mut attrs.0,
377 let flags = libc::POSIX_SPAWN_SETSIGDEF |
378 libc::POSIX_SPAWN_SETSIGMASK;
379 cvt(libc::posix_spawnattr_setflags(&mut attrs.0, flags as _))?;
381 // Make sure we synchronize access to the global `environ` resource
382 let _env_lock = sys::os::env_lock();
383 let envp = envp.map(|c| c.as_ptr())
384 .unwrap_or_else(|| *sys::os::environ() as *const _);
385 let ret = libc::posix_spawnp(
390 self.get_argv().as_ptr() as *const _,
396 Err(io::Error::from_raw_os_error(ret))
402 ////////////////////////////////////////////////////////////////////////////////
404 ////////////////////////////////////////////////////////////////////////////////
406 /// The unique ID of the process (this should never be negative).
409 status: Option<ExitStatus>,
413 pub fn id(&self) -> u32 {
417 pub fn kill(&mut self) -> io::Result<()> {
418 // If we've already waited on this process then the pid can be recycled
419 // and used for another process, and we probably shouldn't be killing
420 // random processes, so just return an error.
421 if self.status.is_some() {
422 Err(Error::new(ErrorKind::InvalidInput,
423 "invalid argument: can't kill an exited process"))
425 cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(|_| ())
429 pub fn wait(&mut self) -> io::Result<ExitStatus> {
431 if let Some(status) = self.status {
434 let mut status = 0 as c_int;
435 cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?;
436 self.status = Some(ExitStatus::new(status));
437 Ok(ExitStatus::new(status))
440 pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
441 if let Some(status) = self.status {
442 return Ok(Some(status))
444 let mut status = 0 as c_int;
445 let pid = cvt(unsafe {
446 libc::waitpid(self.pid, &mut status, libc::WNOHANG)
451 self.status = Some(ExitStatus::new(status));
452 Ok(Some(ExitStatus::new(status)))