2 use crate::io::{self, Error, ErrorKind};
5 use crate::sys::process::process_common::*;
8 use libc::{c_int, gid_t, pid_t, uid_t};
10 ////////////////////////////////////////////////////////////////////////////////
12 ////////////////////////////////////////////////////////////////////////////////
15 pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
16 -> io::Result<(Process, StdioPipes)> {
17 const CLOEXEC_MSG_FOOTER: &[u8] = b"NOEX";
19 let envp = self.capture_env();
22 return Err(io::Error::new(ErrorKind::InvalidInput,
23 "nul byte found in provided data"));
26 let (ours, theirs) = self.setup_io(default, needs_stdin)?;
28 if let Some(ret) = self.posix_spawn(&theirs, envp.as_ref())? {
29 return Ok((ret, ours))
32 let (input, output) = sys::pipe::anon_pipe()?;
34 // Whatever happens after the fork is almost for sure going to touch or
35 // look at the environment in one way or another (PATH in `execvp` or
36 // accessing the `environ` pointer ourselves). Make sure no other thread
37 // is accessing the environment when we do the fork itself.
39 // Note that as soon as we're done with the fork there's no need to hold
40 // a lock any more because the parent won't do anything and the child is
41 // in its own process.
43 let _env_lock = sys::os::env_lock();
51 let Err(err) = self.do_exec(theirs, envp.as_ref());
52 let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
58 CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
59 CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
61 // pipe I/O up to PIPE_BUF bytes should be atomic, and then
62 // we want to be sure we *don't* run at_exit destructors as
63 // we're being torn down regardless
64 assert!(output.write(&bytes).is_ok());
71 let mut p = Process { pid: pid, status: None };
73 let mut bytes = [0; 8];
75 // loop to handle EINTR
77 match input.read(&mut bytes) {
78 Ok(0) => return Ok((p, ours)),
80 assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
81 "Validation on the CLOEXEC pipe failed: {:?}", bytes);
82 let errno = combine(&bytes[0.. 4]);
83 assert!(p.wait().is_ok(),
84 "wait() should either return Ok or panic");
85 return Err(Error::from_raw_os_error(errno))
87 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
89 assert!(p.wait().is_ok(),
90 "wait() should either return Ok or panic");
91 panic!("the CLOEXEC pipe failed: {:?}", e)
93 Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
94 assert!(p.wait().is_ok(),
95 "wait() should either return Ok or panic");
96 panic!("short read on the CLOEXEC pipe")
101 fn combine(arr: &[u8]) -> i32 {
102 let a = arr[0] as u32;
103 let b = arr[1] as u32;
104 let c = arr[2] as u32;
105 let d = arr[3] as u32;
107 ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
111 pub fn exec(&mut self, default: Stdio) -> io::Error {
112 let envp = self.capture_env();
115 return io::Error::new(ErrorKind::InvalidInput,
116 "nul byte found in provided data")
119 match self.setup_io(default, true) {
122 // Similar to when forking, we want to ensure that access to
123 // the environment is synchronized, so make sure to grab the
124 // environment lock before we try to exec.
125 let _lock = sys::os::env_lock();
127 let Err(e) = self.do_exec(theirs, envp.as_ref());
135 // And at this point we've reached a special time in the life of the
136 // child. The child must now be considered hamstrung and unable to
137 // do anything other than syscalls really. Consider the following
140 // 1. Thread A of process 1 grabs the malloc() mutex
141 // 2. Thread B of process 1 forks(), creating thread C
142 // 3. Thread C of process 2 then attempts to malloc()
143 // 4. The memory of process 2 is the same as the memory of
144 // process 1, so the mutex is locked.
146 // This situation looks a lot like deadlock, right? It turns out
147 // that this is what pthread_atfork() takes care of, which is
148 // presumably implemented across platforms. The first thing that
149 // threads to *before* forking is to do things like grab the malloc
150 // mutex, and then after the fork they unlock it.
152 // Despite this information, libnative's spawn has been witnessed to
153 // deadlock on both macOS and FreeBSD. I'm not entirely sure why, but
154 // all collected backtraces point at malloc/free traffic in the
155 // child spawned process.
157 // For this reason, the block of code below should contain 0
158 // invocations of either malloc of free (or their related friends).
160 // As an example of not having malloc/free traffic, we don't close
161 // this file descriptor by dropping the FileDesc (which contains an
162 // allocation). Instead we just close it manually. This will never
163 // have the drop glue anyway because this code never returns (the
164 // child will either exec() or invoke libc::exit)
168 maybe_envp: Option<&CStringArray>
169 ) -> Result<!, io::Error> {
170 use crate::sys::{self, cvt_r};
172 if let Some(fd) = stdio.stdin.fd() {
173 cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO))?;
175 if let Some(fd) = stdio.stdout.fd() {
176 cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO))?;
178 if let Some(fd) = stdio.stderr.fd() {
179 cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO))?;
182 #[cfg(not(target_os = "l4re"))]
184 if let Some(u) = self.get_gid() {
185 cvt(libc::setgid(u as gid_t))?;
187 if let Some(u) = self.get_uid() {
188 // When dropping privileges from root, the `setgroups` call
189 // will remove any extraneous groups. If we don't call this,
190 // then even though our uid has dropped, we may still have
191 // groups that enable us to do super-user things. This will
192 // fail if we aren't root, so don't bother checking the
193 // return value, this is just done as an optimistic
194 // privilege dropping function.
195 //FIXME: Redox kernel does not support setgroups yet
196 #[cfg(not(target_os = "redox"))]
197 let _ = libc::setgroups(0, ptr::null());
198 cvt(libc::setuid(u as uid_t))?;
201 if let Some(ref cwd) = *self.get_cwd() {
202 cvt(libc::chdir(cwd.as_ptr()))?;
205 // emscripten has no signal support.
206 #[cfg(not(target_os = "emscripten"))]
208 use crate::mem::MaybeUninit;
209 // Reset signal handling so the child process starts in a
210 // standardized state. libstd ignores SIGPIPE, and signal-handling
211 // libraries often set a mask. Child processes inherit ignored
212 // signals and the signal mask from their parent, but most
213 // UNIX programs do not reset these things on their own, so we
214 // need to clean things up now to avoid confusing the program
215 // we're about to run.
216 let mut set = MaybeUninit::<libc::sigset_t>::uninit();
217 cvt(sigemptyset(set.as_mut_ptr()))?;
218 cvt(libc::pthread_sigmask(libc::SIG_SETMASK, set.as_ptr(),
220 let ret = sys::signal(libc::SIGPIPE, libc::SIG_DFL);
221 if ret == libc::SIG_ERR {
222 return Err(io::Error::last_os_error())
226 for callback in self.get_closures().iter_mut() {
230 // Although we're performing an exec here we may also return with an
231 // error from this function (without actually exec'ing) in which case we
232 // want to be sure to restore the global environment back to what it
233 // once was, ensuring that our temporary override, when free'd, doesn't
234 // corrupt our process's environment.
235 let mut _reset = None;
236 if let Some(envp) = maybe_envp {
237 struct Reset(*const *const libc::c_char);
239 impl Drop for Reset {
242 *sys::os::environ() = self.0;
247 _reset = Some(Reset(*sys::os::environ()));
248 *sys::os::environ() = envp.as_ptr();
251 libc::execvp(self.get_argv()[0], self.get_argv().as_ptr());
252 Err(io::Error::last_os_error())
255 #[cfg(not(any(target_os = "macos", target_os = "freebsd",
256 all(target_os = "linux", target_env = "gnu"))))]
257 fn posix_spawn(&mut self, _: &ChildPipes, _: Option<&CStringArray>)
258 -> io::Result<Option<Process>>
263 // Only support platforms for which posix_spawn() can return ENOENT
265 #[cfg(any(target_os = "macos", target_os = "freebsd",
266 all(target_os = "linux", target_env = "gnu")))]
267 fn posix_spawn(&mut self, stdio: &ChildPipes, envp: Option<&CStringArray>)
268 -> io::Result<Option<Process>>
270 use crate::mem::MaybeUninit;
273 if self.get_gid().is_some() ||
274 self.get_uid().is_some() ||
275 self.env_saw_path() ||
276 !self.get_closures().is_empty() {
280 // Only glibc 2.24+ posix_spawn() supports returning ENOENT directly.
281 #[cfg(all(target_os = "linux", target_env = "gnu"))]
283 if let Some(version) = sys::os::glibc_version() {
284 if version < (2, 24) {
292 // Solaris and glibc 2.29+ can set a new working directory, and maybe
293 // others will gain this non-POSIX function too. We'll check for this
294 // weak symbol as soon as it's needed, so we can return early otherwise
295 // to do a manual chdir before exec.
297 fn posix_spawn_file_actions_addchdir_np(
298 *mut libc::posix_spawn_file_actions_t,
302 let addchdir = match self.get_cwd() {
303 Some(cwd) => match posix_spawn_file_actions_addchdir_np.get() {
304 Some(f) => Some((f, cwd)),
305 None => return Ok(None),
310 let mut p = Process { pid: 0, status: None };
312 struct PosixSpawnFileActions(MaybeUninit<libc::posix_spawn_file_actions_t>);
314 impl Drop for PosixSpawnFileActions {
317 libc::posix_spawn_file_actions_destroy(self.0.as_mut_ptr());
322 struct PosixSpawnattr(MaybeUninit<libc::posix_spawnattr_t>);
324 impl Drop for PosixSpawnattr {
327 libc::posix_spawnattr_destroy(self.0.as_mut_ptr());
333 let mut file_actions = PosixSpawnFileActions(MaybeUninit::uninit());
334 let mut attrs = PosixSpawnattr(MaybeUninit::uninit());
336 libc::posix_spawnattr_init(attrs.0.as_mut_ptr());
337 libc::posix_spawn_file_actions_init(file_actions.0.as_mut_ptr());
339 if let Some(fd) = stdio.stdin.fd() {
340 cvt(libc::posix_spawn_file_actions_adddup2(file_actions.0.as_mut_ptr(),
342 libc::STDIN_FILENO))?;
344 if let Some(fd) = stdio.stdout.fd() {
345 cvt(libc::posix_spawn_file_actions_adddup2(file_actions.0.as_mut_ptr(),
347 libc::STDOUT_FILENO))?;
349 if let Some(fd) = stdio.stderr.fd() {
350 cvt(libc::posix_spawn_file_actions_adddup2(file_actions.0.as_mut_ptr(),
352 libc::STDERR_FILENO))?;
354 if let Some((f, cwd)) = addchdir {
355 cvt(f(file_actions.0.as_mut_ptr(), cwd.as_ptr()))?;
358 let mut set = MaybeUninit::<libc::sigset_t>::uninit();
359 cvt(sigemptyset(set.as_mut_ptr()))?;
360 cvt(libc::posix_spawnattr_setsigmask(attrs.0.as_mut_ptr(),
362 cvt(sigaddset(set.as_mut_ptr(), libc::SIGPIPE))?;
363 cvt(libc::posix_spawnattr_setsigdefault(attrs.0.as_mut_ptr(),
366 let flags = libc::POSIX_SPAWN_SETSIGDEF |
367 libc::POSIX_SPAWN_SETSIGMASK;
368 cvt(libc::posix_spawnattr_setflags(attrs.0.as_mut_ptr(), flags as _))?;
370 // Make sure we synchronize access to the global `environ` resource
371 let _env_lock = sys::os::env_lock();
372 let envp = envp.map(|c| c.as_ptr())
373 .unwrap_or_else(|| *sys::os::environ() as *const _);
374 let ret = libc::posix_spawnp(
377 file_actions.0.as_ptr(),
379 self.get_argv().as_ptr() as *const _,
385 Err(io::Error::from_raw_os_error(ret))
391 ////////////////////////////////////////////////////////////////////////////////
393 ////////////////////////////////////////////////////////////////////////////////
395 /// The unique ID of the process (this should never be negative).
398 status: Option<ExitStatus>,
402 pub fn id(&self) -> u32 {
406 pub fn kill(&mut self) -> io::Result<()> {
407 // If we've already waited on this process then the pid can be recycled
408 // and used for another process, and we probably shouldn't be killing
409 // random processes, so just return an error.
410 if self.status.is_some() {
411 Err(Error::new(ErrorKind::InvalidInput,
412 "invalid argument: can't kill an exited process"))
414 cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(|_| ())
418 pub fn wait(&mut self) -> io::Result<ExitStatus> {
419 use crate::sys::cvt_r;
420 if let Some(status) = self.status {
423 let mut status = 0 as c_int;
424 cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?;
425 self.status = Some(ExitStatus::new(status));
426 Ok(ExitStatus::new(status))
429 pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
430 if let Some(status) = self.status {
431 return Ok(Some(status))
433 let mut status = 0 as c_int;
434 let pid = cvt(unsafe {
435 libc::waitpid(self.pid, &mut status, libc::WNOHANG)
440 self.status = Some(ExitStatus::new(status));
441 Ok(Some(ExitStatus::new(status)))
446 /// Unix exit statuses
447 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
448 pub struct ExitStatus(c_int);
451 pub fn new(status: c_int) -> ExitStatus {
455 fn exited(&self) -> bool {
456 unsafe { libc::WIFEXITED(self.0) }
459 pub fn success(&self) -> bool {
460 self.code() == Some(0)
463 pub fn code(&self) -> Option<i32> {
465 Some(unsafe { libc::WEXITSTATUS(self.0) })
471 pub fn signal(&self) -> Option<i32> {
473 Some(unsafe { libc::WTERMSIG(self.0) })
480 impl From<c_int> for ExitStatus {
481 fn from(a: c_int) -> ExitStatus {
486 impl fmt::Display for ExitStatus {
487 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
488 if let Some(code) = self.code() {
489 write!(f, "exit code: {}", code)
491 let signal = self.signal().unwrap();
492 write!(f, "signal: {}", signal)