1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
14 use collections::HashMap;
15 use collections::hash_map::Hasher;
18 use old_io::process::{ProcessExit, ExitStatus, ExitSignal};
19 use old_io::{self, IoResult, IoError, EndOfFile};
20 use libc::{self, pid_t, c_void, c_int};
23 use old_path::BytesContainer;
25 use sync::mpsc::{channel, Sender, Receiver};
26 use sys::fs::FileDesc;
27 use sys::{self, retry, c, wouldblock, set_nonblocking, ms_to_timeval};
28 use sys_common::helper_thread::Helper;
29 use sys_common::{AsInner, mkerr_libc, timeout};
31 pub use sys_common::ProcessConfig;
33 helper_init! { static HELPER: Helper<Req> }
35 /// Unix-specific extensions to the Command builder
36 pub struct CommandExt {
41 /// The unique id of the process (this should never be negative).
47 NewChild(libc::pid_t, Sender<ProcessExit>, u64),
50 const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
53 pub fn id(&self) -> pid_t {
57 pub unsafe fn kill(&self, signal: int) -> IoResult<()> {
58 Process::killpid(self.pid, signal)
61 pub unsafe fn killpid(pid: pid_t, signal: int) -> IoResult<()> {
62 let r = libc::funcs::posix88::signal::kill(pid, signal as c_int);
66 pub fn spawn<K, V, C, P>(cfg: &C, in_fd: Option<P>,
67 out_fd: Option<P>, err_fd: Option<P>)
69 where C: ProcessConfig<K, V>, P: AsInner<FileDesc>,
70 K: BytesContainer + Eq + Hash<Hasher>, V: BytesContainer
72 use libc::funcs::posix88::unistd::{fork, dup2, close, chdir, execvp};
73 use libc::funcs::bsd44::getdtablesize;
77 pub fn rust_unset_sigprocmask();
81 unsafe fn set_cloexec(fd: c_int) {
82 let ret = c::ioctl(fd, c::FIOCLEX);
86 let dirp = cfg.cwd().map(|c| c.as_ptr()).unwrap_or(ptr::null());
88 // temporary until unboxed closures land
90 mem::transmute::<&ProcessConfig<K,V>,&'static ProcessConfig<K,V>>(cfg)
93 with_envp(cfg.env(), move|envp: *const c_void| {
94 with_argv(cfg.program(), cfg.args(), move|argv: *const *const libc::c_char| unsafe {
95 let (input, mut output) = try!(sys::os::pipe());
97 // We may use this in the child, so perform allocations before the
99 let devnull = b"/dev/null\0";
101 set_cloexec(output.fd());
105 return Err(super::last_error())
108 fn combine(arr: &[u8]) -> i32 {
109 let a = arr[0] as u32;
110 let b = arr[1] as u32;
111 let c = arr[2] as u32;
112 let d = arr[3] as u32;
114 ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
117 let p = Process{ pid: pid };
119 let mut bytes = [0; 8];
120 return match input.read(&mut bytes) {
122 assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
123 "Validation on the CLOEXEC pipe failed: {:?}", bytes);
124 let errno = combine(&bytes[0.. 4]);
125 assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
126 Err(super::decode_error(errno))
128 Err(ref e) if e.kind == EndOfFile => Ok(p),
130 assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
131 panic!("the CLOEXEC pipe failed: {:?}", e)
133 Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
134 assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
135 panic!("short read on the CLOEXEC pipe")
140 // And at this point we've reached a special time in the life of the
141 // child. The child must now be considered hamstrung and unable to
142 // do anything other than syscalls really. Consider the following
145 // 1. Thread A of process 1 grabs the malloc() mutex
146 // 2. Thread B of process 1 forks(), creating thread C
147 // 3. Thread C of process 2 then attempts to malloc()
148 // 4. The memory of process 2 is the same as the memory of
149 // process 1, so the mutex is locked.
151 // This situation looks a lot like deadlock, right? It turns out
152 // that this is what pthread_atfork() takes care of, which is
153 // presumably implemented across platforms. The first thing that
154 // threads to *before* forking is to do things like grab the malloc
155 // mutex, and then after the fork they unlock it.
157 // Despite this information, libnative's spawn has been witnessed to
158 // deadlock on both OSX and FreeBSD. I'm not entirely sure why, but
159 // all collected backtraces point at malloc/free traffic in the
160 // child spawned process.
162 // For this reason, the block of code below should contain 0
163 // invocations of either malloc of free (or their related friends).
165 // As an example of not having malloc/free traffic, we don't close
166 // this file descriptor by dropping the FileDesc (which contains an
167 // allocation). Instead we just close it manually. This will never
168 // have the drop glue anyway because this code never returns (the
169 // child will either exec() or invoke libc::exit)
170 let _ = libc::close(input.fd());
172 fn fail(output: &mut FileDesc) -> ! {
173 let errno = sys::os::errno() as u32;
179 CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
180 CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
182 // pipe I/O up to PIPE_BUF bytes should be atomic
183 assert!(output.write(&bytes).is_ok());
184 unsafe { libc::_exit(1) }
187 rustrt::rust_unset_sigprocmask();
189 // If a stdio file descriptor is set to be ignored (via a -1 file
190 // descriptor), then we don't actually close it, but rather open
191 // up /dev/null into that file descriptor. Otherwise, the first file
192 // descriptor opened up in the child would be numbered as one of the
193 // stdio file descriptors, which is likely to wreak havoc.
194 let setup = |src: Option<P>, dst: c_int| {
195 let src = match src {
197 let flags = if dst == libc::STDIN_FILENO {
202 libc::open(devnull.as_ptr() as *const _, flags, 0)
205 let fd = obj.as_inner().fd();
206 // Leak the memory and the file descriptor. We're in the
207 // child now an all our resources are going to be
208 // cleaned up very soon
213 src != -1 && retry(|| dup2(src, dst)) != -1
216 if !setup(in_fd, libc::STDIN_FILENO) { fail(&mut output) }
217 if !setup(out_fd, libc::STDOUT_FILENO) { fail(&mut output) }
218 if !setup(err_fd, libc::STDERR_FILENO) { fail(&mut output) }
220 // close all other fds
221 for fd in (3..getdtablesize()).rev() {
222 if fd != output.fd() {
223 let _ = close(fd as c_int);
229 if libc::setgid(u as libc::gid_t) != 0 {
237 // When dropping privileges from root, the `setgroups` call
238 // will remove any extraneous groups. If we don't call this,
239 // then even though our uid has dropped, we may still have
240 // groups that enable us to do super-user things. This will
241 // fail if we aren't root, so don't bother checking the
242 // return value, this is just done as an optimistic
243 // privilege dropping function.
245 fn setgroups(ngroups: libc::c_int,
246 ptr: *const libc::c_void) -> libc::c_int;
248 let _ = setgroups(0, ptr::null());
250 if libc::setuid(u as libc::uid_t) != 0 {
257 // Don't check the error of setsid because it fails if we're the
258 // process leader already. We just forked so it shouldn't return
259 // error, but ignore it anyway.
260 let _ = libc::setsid();
262 if !dirp.is_null() && chdir(dirp) == -1 {
266 *sys::os::environ() = envp as *const _;
268 let _ = execvp(*argv, argv as *mut _);
274 pub fn wait(&self, deadline: u64) -> IoResult<ProcessExit> {
276 use sync::mpsc::TryRecvError;
278 static mut WRITE_FD: libc::c_int = 0;
280 let mut status = 0 as c_int;
282 return match retry(|| unsafe { c::waitpid(self.pid, &mut status, 0) }) {
283 -1 => panic!("unknown waitpid error: {:?}", super::last_error()),
284 _ => Ok(translate_status(status)),
288 // On unix, wait() and its friends have no timeout parameters, so there is
289 // no way to time out a thread in wait(). From some googling and some
290 // thinking, it appears that there are a few ways to handle timeouts in
291 // wait(), but the only real reasonable one for a multi-threaded program is
292 // to listen for SIGCHLD.
294 // With this in mind, the waiting mechanism with a timeout barely uses
295 // waitpid() at all. There are a few times that waitpid() is invoked with
296 // WNOHANG, but otherwise all the necessary blocking is done by waiting for
297 // a SIGCHLD to arrive (and that blocking has a timeout). Note, however,
298 // that waitpid() is still used to actually reap the child.
300 // Signal handling is super tricky in general, and this is no exception. Due
301 // to the async nature of SIGCHLD, we use the self-pipe trick to transmit
302 // data out of the signal handler to the rest of the application. The first
303 // idea would be to have each thread waiting with a timeout to read this
304 // output file descriptor, but a write() is akin to a signal(), not a
305 // broadcast(), so it would only wake up one thread, and possibly the wrong
306 // thread. Hence a helper thread is used.
308 // The helper thread here is responsible for farming requests for a
309 // waitpid() with a timeout, and then processing all of the wait requests.
310 // By guaranteeing that only this helper thread is reading half of the
311 // self-pipe, we're sure that we'll never lose a SIGCHLD. This helper thread
312 // is also responsible for select() to wait for incoming messages or
313 // incoming SIGCHLD messages, along with passing an appropriate timeout to
314 // select() to wake things up as necessary.
316 // The ordering of the following statements is also very purposeful. First,
317 // we must be guaranteed that the helper thread is booted and available to
318 // receive SIGCHLD signals, and then we must also ensure that we do a
319 // nonblocking waitpid() at least once before we go ask the sigchld helper.
320 // This prevents the race where the child exits, we boot the helper, and
321 // then we ask for the child's exit status (never seeing a sigchld).
323 // The actual communication between the helper thread and this thread is
324 // quite simple, just a channel moving data around.
326 unsafe { HELPER.boot(register_sigchld, waitpid_helper) }
328 match self.try_wait() {
329 Some(ret) => return Ok(ret),
333 let (tx, rx) = channel();
334 unsafe { HELPER.send(NewChild(self.pid, tx, deadline)); }
335 return match rx.recv() {
337 Err(..) => Err(timeout("wait timed out")),
340 // Register a new SIGCHLD handler, returning the reading half of the
341 // self-pipe plus the old handler registered (return value of sigaction).
343 // Be sure to set up the self-pipe first because as soon as we register a
344 // handler we're going to start receiving signals.
345 fn register_sigchld() -> (libc::c_int, c::sigaction) {
347 let mut pipes = [0; 2];
348 assert_eq!(libc::pipe(pipes.as_mut_ptr()), 0);
349 set_nonblocking(pipes[0], true).ok().unwrap();
350 set_nonblocking(pipes[1], true).ok().unwrap();
353 let mut old: c::sigaction = mem::zeroed();
354 let mut new: c::sigaction = mem::zeroed();
355 new.sa_handler = sigchld_handler;
356 new.sa_flags = c::SA_NOCLDSTOP;
357 assert_eq!(c::sigaction(c::SIGCHLD, &new, &mut old), 0);
362 // Helper thread for processing SIGCHLD messages
363 fn waitpid_helper(input: libc::c_int,
364 messages: Receiver<Req>,
365 (read_fd, old): (libc::c_int, c::sigaction)) {
366 set_nonblocking(input, true).ok().unwrap();
367 let mut set: c::fd_set = unsafe { mem::zeroed() };
368 let mut tv: libc::timeval;
369 let mut active = Vec::<(libc::pid_t, Sender<ProcessExit>, u64)>::new();
370 let max = cmp::max(input, read_fd) + 1;
373 // Figure out the timeout of our syscall-to-happen. If we're waiting
374 // for some processes, then they'll have a timeout, otherwise we
375 // wait indefinitely for a message to arrive.
377 // FIXME: sure would be nice to not have to scan the entire array
378 let min = active.iter().map(|a| a.2).enumerate().min_by(|p| {
381 let (p, idx) = match min {
382 Some((idx, deadline)) => {
383 let now = sys::timer::now();
384 let ms = if now < deadline {deadline - now} else {0};
385 tv = ms_to_timeval(ms);
386 (&mut tv as *mut _, idx)
388 None => (ptr::null_mut(), -1),
391 // Wait for something to happen
392 c::fd_set(&mut set, input);
393 c::fd_set(&mut set, read_fd);
394 match unsafe { c::select(max, &mut set, ptr::null_mut(),
395 ptr::null_mut(), p) } {
396 // interrupted, retry
397 -1 if os::errno() == libc::EINTR as i32 => continue,
399 // We read something, break out and process
402 // Timeout, the pending request is removed
404 drop(active.remove(idx));
408 n => panic!("error in select {:?} ({:?})", os::errno(), n),
411 // Process any pending messages
414 match messages.try_recv() {
415 Ok(NewChild(pid, tx, deadline)) => {
416 active.push((pid, tx, deadline));
418 Err(TryRecvError::Disconnected) => {
419 assert!(active.len() == 0);
422 Err(TryRecvError::Empty) => break,
427 // If a child exited (somehow received SIGCHLD), then poll all
428 // children to see if any of them exited.
430 // We also attempt to be responsible netizens when dealing with
431 // SIGCHLD by invoking any previous SIGCHLD handler instead of just
432 // ignoring any previous SIGCHLD handler. Note that we don't provide
433 // a 1:1 mapping of our handler invocations to the previous handler
434 // invocations because we drain the `read_fd` entirely. This is
435 // probably OK because the kernel is already allowed to coalesce
436 // simultaneous signals, we're just doing some extra coalescing.
438 // Another point of note is that this likely runs the signal handler
439 // on a different thread than the one that received the signal. I
440 // *think* this is ok at this time.
442 // The main reason for doing this is to allow stdtest to run native
443 // tests as well. Both libgreen and libnative are running around
444 // with process timeouts, but libgreen should get there first
445 // (currently libuv doesn't handle old signal handlers).
447 let i: uint = unsafe { mem::transmute(old.sa_handler) };
449 assert!(old.sa_flags & c::SA_SIGINFO == 0);
450 (old.sa_handler)(c::SIGCHLD);
453 // FIXME: sure would be nice to not have to scan the entire
455 active.retain(|&(pid, ref tx, _)| {
456 let pr = Process { pid: pid };
457 match pr.try_wait() {
458 Some(msg) => { tx.send(msg).unwrap(); false }
465 // Once this helper thread is done, we re-register the old sigchld
466 // handler and close our intermediate file descriptors.
468 assert_eq!(c::sigaction(c::SIGCHLD, &old, ptr::null_mut()), 0);
469 let _ = libc::close(read_fd);
470 let _ = libc::close(WRITE_FD);
475 // Drain all pending data from the file descriptor, returning if any data
476 // could be drained. This requires that the file descriptor is in
478 fn drain(fd: libc::c_int) -> bool {
481 let mut buf = [0u8; 1];
483 libc::read(fd, buf.as_mut_ptr() as *mut libc::c_void,
484 buf.len() as libc::size_t)
486 n if n > 0 => { ret = true; }
488 -1 if wouldblock() => return ret,
489 n => panic!("bad read {:?} ({:?})", os::last_os_error(), n),
494 // Signal handler for SIGCHLD signals, must be async-signal-safe!
496 // This function will write to the writing half of the "self pipe" to wake
497 // up the helper thread if it's waiting. Note that this write must be
498 // nonblocking because if it blocks and the reader is the thread we
499 // interrupted, then we'll deadlock.
501 // When writing, if the write returns EWOULDBLOCK then we choose to ignore
502 // it. At that point we're guaranteed that there's something in the pipe
503 // which will wake up the other end at some point, so we just allow this
504 // signal to be coalesced with the pending signals on the pipe.
505 extern fn sigchld_handler(_signum: libc::c_int) {
508 libc::write(WRITE_FD, &msg as *const _ as *const libc::c_void, 1)
511 -1 if wouldblock() => {} // see above comments
512 n => panic!("bad error on write fd: {:?} {:?}", n, os::errno()),
517 pub fn try_wait(&self) -> Option<ProcessExit> {
518 let mut status = 0 as c_int;
519 match retry(|| unsafe {
520 c::waitpid(self.pid, &mut status, c::WNOHANG)
522 n if n == self.pid => Some(translate_status(status)),
524 n => panic!("unknown waitpid error `{:?}`: {:?}", n,
525 super::last_error()),
530 fn with_argv<T,F>(prog: &CString, args: &[CString],
533 where F : FnOnce(*const *const libc::c_char) -> T
535 let mut ptrs: Vec<*const libc::c_char> = Vec::with_capacity(args.len()+1);
537 // Convert the CStrings into an array of pointers. Note: the
538 // lifetime of the various CStrings involved is guaranteed to be
539 // larger than the lifetime of our invocation of cb, but this is
540 // technically unsafe as the callback could leak these pointers
542 ptrs.push(prog.as_ptr());
543 ptrs.extend(args.iter().map(|tmp| tmp.as_ptr()));
545 // Add a terminating null pointer (required by libc).
546 ptrs.push(ptr::null());
551 fn with_envp<K,V,T,F>(env: Option<&HashMap<K, V>>,
554 where F : FnOnce(*const c_void) -> T,
555 K : BytesContainer + Eq + Hash<Hasher>,
558 // On posixy systems we can pass a char** for envp, which is a
559 // null-terminated array of "k=v\0" strings. Since we must create
560 // these strings locally, yet expose a raw pointer to them, we
561 // create a temporary vector to own the CStrings that outlives the
565 let mut tmps = Vec::with_capacity(env.len());
568 let mut kv = Vec::new();
569 kv.push_all(pair.0.container_as_bytes());
571 kv.push_all(pair.1.container_as_bytes());
572 kv.push(0); // terminating null
576 // As with `with_argv`, this is unsafe, since cb could leak the pointers.
577 let mut ptrs: Vec<*const libc::c_char> =
579 .map(|tmp| tmp.as_ptr() as *const libc::c_char)
581 ptrs.push(ptr::null());
583 cb(ptrs.as_ptr() as *const c_void)
589 fn translate_status(status: c_int) -> ProcessExit {
590 #![allow(non_snake_case)]
591 #[cfg(any(target_os = "linux", target_os = "android"))]
593 pub fn WIFEXITED(status: i32) -> bool { (status & 0xff) == 0 }
594 pub fn WEXITSTATUS(status: i32) -> i32 { (status >> 8) & 0xff }
595 pub fn WTERMSIG(status: i32) -> i32 { status & 0x7f }
598 #[cfg(any(target_os = "macos",
600 target_os = "freebsd",
601 target_os = "dragonfly",
602 target_os = "openbsd"))]
604 pub fn WIFEXITED(status: i32) -> bool { (status & 0x7f) == 0 }
605 pub fn WEXITSTATUS(status: i32) -> i32 { status >> 8 }
606 pub fn WTERMSIG(status: i32) -> i32 { status & 0o177 }
609 if imp::WIFEXITED(status) {
610 ExitStatus(imp::WEXITSTATUS(status) as int)
612 ExitSignal(imp::WTERMSIG(status) as int)