1 use crate::io::{self, Error, ErrorKind};
4 use crate::sys::process::process_common::*;
7 use libc::{c_int, gid_t, pid_t, uid_t};
9 ////////////////////////////////////////////////////////////////////////////////
11 ////////////////////////////////////////////////////////////////////////////////
14 pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
15 -> io::Result<(Process, StdioPipes)> {
16 const CLOEXEC_MSG_FOOTER: &[u8] = b"NOEX";
18 let envp = self.capture_env();
21 return Err(io::Error::new(ErrorKind::InvalidInput,
22 "nul byte found in provided data"));
25 let (ours, theirs) = self.setup_io(default, needs_stdin)?;
27 if let Some(ret) = self.posix_spawn(&theirs, envp.as_ref())? {
28 return Ok((ret, ours))
31 let (input, output) = sys::pipe::anon_pipe()?;
33 // Whatever happens after the fork is almost for sure going to touch or
34 // look at the environment in one way or another (PATH in `execvp` or
35 // accessing the `environ` pointer ourselves). Make sure no other thread
36 // is accessing the environment when we do the fork itself.
38 // Note that as soon as we're done with the fork there's no need to hold
39 // a lock any more because the parent won't do anything and the child is
40 // in its own process.
42 let _env_lock = sys::os::env_lock();
50 let err = self.do_exec(theirs, envp.as_ref());
51 let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
57 CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
58 CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
60 // pipe I/O up to PIPE_BUF bytes should be atomic, and then
61 // we want to be sure we *don't* run at_exit destructors as
62 // we're being torn down regardless
63 assert!(output.write(&bytes).is_ok());
70 let mut p = Process { pid: pid, status: None };
72 let mut bytes = [0; 8];
74 // loop to handle EINTR
76 match input.read(&mut bytes) {
77 Ok(0) => return Ok((p, ours)),
79 assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
80 "Validation on the CLOEXEC pipe failed: {:?}", bytes);
81 let errno = combine(&bytes[0.. 4]);
82 assert!(p.wait().is_ok(),
83 "wait() should either return Ok or panic");
84 return Err(Error::from_raw_os_error(errno))
86 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
88 assert!(p.wait().is_ok(),
89 "wait() should either return Ok or panic");
90 panic!("the CLOEXEC pipe failed: {:?}", e)
92 Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
93 assert!(p.wait().is_ok(),
94 "wait() should either return Ok or panic");
95 panic!("short read on the CLOEXEC pipe")
100 fn combine(arr: &[u8]) -> i32 {
101 let a = arr[0] as u32;
102 let b = arr[1] as u32;
103 let c = arr[2] as u32;
104 let d = arr[3] as u32;
106 ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
110 pub fn exec(&mut self, default: Stdio) -> io::Error {
111 let envp = self.capture_env();
114 return io::Error::new(ErrorKind::InvalidInput,
115 "nul byte found in provided data")
118 match self.setup_io(default, true) {
121 // Similar to when forking, we want to ensure that access to
122 // the environment is synchronized, so make sure to grab the
123 // environment lock before we try to exec.
124 let _lock = sys::os::env_lock();
126 self.do_exec(theirs, envp.as_ref())
133 // And at this point we've reached a special time in the life of the
134 // child. The child must now be considered hamstrung and unable to
135 // do anything other than syscalls really. Consider the following
138 // 1. Thread A of process 1 grabs the malloc() mutex
139 // 2. Thread B of process 1 forks(), creating thread C
140 // 3. Thread C of process 2 then attempts to malloc()
141 // 4. The memory of process 2 is the same as the memory of
142 // process 1, so the mutex is locked.
144 // This situation looks a lot like deadlock, right? It turns out
145 // that this is what pthread_atfork() takes care of, which is
146 // presumably implemented across platforms. The first thing that
147 // threads to *before* forking is to do things like grab the malloc
148 // mutex, and then after the fork they unlock it.
150 // Despite this information, libnative's spawn has been witnessed to
151 // deadlock on both macOS and FreeBSD. I'm not entirely sure why, but
152 // all collected backtraces point at malloc/free traffic in the
153 // child spawned process.
155 // For this reason, the block of code below should contain 0
156 // invocations of either malloc of free (or their related friends).
158 // As an example of not having malloc/free traffic, we don't close
159 // this file descriptor by dropping the FileDesc (which contains an
160 // allocation). Instead we just close it manually. This will never
161 // have the drop glue anyway because this code never returns (the
162 // child will either exec() or invoke libc::exit)
166 maybe_envp: Option<&CStringArray>
168 use crate::sys::{self, cvt_r};
171 ($e:expr) => (match $e {
177 if let Some(fd) = stdio.stdin.fd() {
178 t!(cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO)));
180 if let Some(fd) = stdio.stdout.fd() {
181 t!(cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO)));
183 if let Some(fd) = stdio.stderr.fd() {
184 t!(cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO)));
187 if cfg!(not(any(target_os = "l4re"))) {
188 if let Some(u) = self.get_gid() {
189 t!(cvt(libc::setgid(u as gid_t)));
191 if let Some(u) = self.get_uid() {
192 // When dropping privileges from root, the `setgroups` call
193 // will remove any extraneous groups. If we don't call this,
194 // then even though our uid has dropped, we may still have
195 // groups that enable us to do super-user things. This will
196 // fail if we aren't root, so don't bother checking the
197 // return value, this is just done as an optimistic
198 // privilege dropping function.
199 let _ = libc::setgroups(0, ptr::null());
201 t!(cvt(libc::setuid(u as uid_t)));
204 if let Some(ref cwd) = *self.get_cwd() {
205 t!(cvt(libc::chdir(cwd.as_ptr())));
208 // emscripten has no signal support.
209 #[cfg(not(any(target_os = "emscripten")))]
212 // Reset signal handling so the child process starts in a
213 // standardized state. libstd ignores SIGPIPE, and signal-handling
214 // libraries often set a mask. Child processes inherit ignored
215 // signals and the signal mask from their parent, but most
216 // UNIX programs do not reset these things on their own, so we
217 // need to clean things up now to avoid confusing the program
218 // we're about to run.
219 let mut set: libc::sigset_t = mem::uninitialized();
220 if cfg!(target_os = "android") {
221 // Implementing sigemptyset allow us to support older Android
222 // versions. See the comment about Android and sig* functions in
224 libc::memset(&mut set as *mut _ as *mut _,
226 mem::size_of::<libc::sigset_t>());
228 t!(cvt(libc::sigemptyset(&mut set)));
230 t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set,
232 let ret = sys::signal(libc::SIGPIPE, libc::SIG_DFL);
233 if ret == libc::SIG_ERR {
234 return io::Error::last_os_error()
238 for callback in self.get_closures().iter_mut() {
242 // Although we're performing an exec here we may also return with an
243 // error from this function (without actually exec'ing) in which case we
244 // want to be sure to restore the global environment back to what it
245 // once was, ensuring that our temporary override, when free'd, doesn't
246 // corrupt our process's environment.
247 let mut _reset = None;
248 if let Some(envp) = maybe_envp {
249 struct Reset(*const *const libc::c_char);
251 impl Drop for Reset {
254 *sys::os::environ() = self.0;
259 _reset = Some(Reset(*sys::os::environ()));
260 *sys::os::environ() = envp.as_ptr();
263 libc::execvp(self.get_argv()[0], self.get_argv().as_ptr());
264 io::Error::last_os_error()
267 #[cfg(not(any(target_os = "macos", target_os = "freebsd",
268 all(target_os = "linux", target_env = "gnu"))))]
269 fn posix_spawn(&mut self, _: &ChildPipes, _: Option<&CStringArray>)
270 -> io::Result<Option<Process>>
275 // Only support platforms for which posix_spawn() can return ENOENT
277 #[cfg(any(target_os = "macos", target_os = "freebsd",
278 all(target_os = "linux", target_env = "gnu")))]
279 fn posix_spawn(&mut self, stdio: &ChildPipes, envp: Option<&CStringArray>)
280 -> io::Result<Option<Process>>
285 if self.get_gid().is_some() ||
286 self.get_uid().is_some() ||
287 self.env_saw_path() ||
288 self.get_closures().len() != 0 {
292 // Only glibc 2.24+ posix_spawn() supports returning ENOENT directly.
293 #[cfg(all(target_os = "linux", target_env = "gnu"))]
295 if let Some(version) = sys::os::glibc_version() {
296 if version < (2, 24) {
304 // Solaris and glibc 2.29+ can set a new working directory, and maybe
305 // others will gain this non-POSIX function too. We'll check for this
306 // weak symbol as soon as it's needed, so we can return early otherwise
307 // to do a manual chdir before exec.
309 fn posix_spawn_file_actions_addchdir_np(
310 *mut libc::posix_spawn_file_actions_t,
314 let addchdir = match self.get_cwd() {
315 Some(cwd) => match posix_spawn_file_actions_addchdir_np.get() {
316 Some(f) => Some((f, cwd)),
317 None => return Ok(None),
322 let mut p = Process { pid: 0, status: None };
324 struct PosixSpawnFileActions(libc::posix_spawn_file_actions_t);
326 impl Drop for PosixSpawnFileActions {
329 libc::posix_spawn_file_actions_destroy(&mut self.0);
334 struct PosixSpawnattr(libc::posix_spawnattr_t);
336 impl Drop for PosixSpawnattr {
339 libc::posix_spawnattr_destroy(&mut self.0);
345 let mut file_actions = PosixSpawnFileActions(mem::uninitialized());
346 let mut attrs = PosixSpawnattr(mem::uninitialized());
348 libc::posix_spawnattr_init(&mut attrs.0);
349 libc::posix_spawn_file_actions_init(&mut file_actions.0);
351 if let Some(fd) = stdio.stdin.fd() {
352 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
354 libc::STDIN_FILENO))?;
356 if let Some(fd) = stdio.stdout.fd() {
357 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
359 libc::STDOUT_FILENO))?;
361 if let Some(fd) = stdio.stderr.fd() {
362 cvt(libc::posix_spawn_file_actions_adddup2(&mut file_actions.0,
364 libc::STDERR_FILENO))?;
366 if let Some((f, cwd)) = addchdir {
367 cvt(f(&mut file_actions.0, cwd.as_ptr()))?;
370 let mut set: libc::sigset_t = mem::uninitialized();
371 cvt(libc::sigemptyset(&mut set))?;
372 cvt(libc::posix_spawnattr_setsigmask(&mut attrs.0,
374 cvt(libc::sigaddset(&mut set, libc::SIGPIPE))?;
375 cvt(libc::posix_spawnattr_setsigdefault(&mut attrs.0,
378 let flags = libc::POSIX_SPAWN_SETSIGDEF |
379 libc::POSIX_SPAWN_SETSIGMASK;
380 cvt(libc::posix_spawnattr_setflags(&mut attrs.0, flags as _))?;
382 // Make sure we synchronize access to the global `environ` resource
383 let _env_lock = sys::os::env_lock();
384 let envp = envp.map(|c| c.as_ptr())
385 .unwrap_or_else(|| *sys::os::environ() as *const _);
386 let ret = libc::posix_spawnp(
391 self.get_argv().as_ptr() as *const _,
397 Err(io::Error::from_raw_os_error(ret))
403 ////////////////////////////////////////////////////////////////////////////////
405 ////////////////////////////////////////////////////////////////////////////////
407 /// The unique ID of the process (this should never be negative).
410 status: Option<ExitStatus>,
414 pub fn id(&self) -> u32 {
418 pub fn kill(&mut self) -> io::Result<()> {
419 // If we've already waited on this process then the pid can be recycled
420 // and used for another process, and we probably shouldn't be killing
421 // random processes, so just return an error.
422 if self.status.is_some() {
423 Err(Error::new(ErrorKind::InvalidInput,
424 "invalid argument: can't kill an exited process"))
426 cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(|_| ())
430 pub fn wait(&mut self) -> io::Result<ExitStatus> {
431 use crate::sys::cvt_r;
432 if let Some(status) = self.status {
435 let mut status = 0 as c_int;
436 cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?;
437 self.status = Some(ExitStatus::new(status));
438 Ok(ExitStatus::new(status))
441 pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
442 if let Some(status) = self.status {
443 return Ok(Some(status))
445 let mut status = 0 as c_int;
446 let pid = cvt(unsafe {
447 libc::waitpid(self.pid, &mut status, libc::WNOHANG)
452 self.status = Some(ExitStatus::new(status));
453 Ok(Some(ExitStatus::new(status)))