library/std/src/sys/unix/process/process_unix.rs

   1 use crate::convert::{TryFrom, TryInto};
   2 use crate::fmt;
   3 use crate::io::{self, Error, ErrorKind};
   4 use crate::mem;
   5 use crate::num::NonZeroI32;
   6 use crate::ptr;
   7 use crate::sys;
   8 use crate::sys::cvt;
   9 use crate::sys::process::process_common::*;
  10 use core::ffi::NonZero_c_int;
  11
  12 #[cfg(target_os = "linux")]
  13 use crate::os::linux::process::PidFd;
  14
  15 #[cfg(target_os = "linux")]
  16 use crate::sys::weak::raw_syscall;
  17
  18 #[cfg(any(
  19     target_os = "macos",
  20     target_os = "freebsd",
  21     all(target_os = "linux", target_env = "gnu"),
  22     all(target_os = "linux", target_env = "musl"),
  23 ))]
  24 use crate::sys::weak::weak;
  25
  26 #[cfg(target_os = "vxworks")]
  27 use libc::RTP_ID as pid_t;
  28
  29 #[cfg(not(target_os = "vxworks"))]
  30 use libc::{c_int, pid_t};
  31
  32 #[cfg(not(any(target_os = "vxworks", target_os = "l4re")))]
  33 use libc::{gid_t, uid_t};
  34
  35 ////////////////////////////////////////////////////////////////////////////////
  36 // Command
  37 ////////////////////////////////////////////////////////////////////////////////
  38
  39 impl Command {
  40     pub fn spawn(
  41         &mut self,
  42         default: Stdio,
  43         needs_stdin: bool,
  44     ) -> io::Result<(Process, StdioPipes)> {
  45         const CLOEXEC_MSG_FOOTER: [u8; 4] = *b"NOEX";
  46
  47         let envp = self.capture_env();
  48
  49         if self.saw_nul() {
  50             return Err(io::const_io_error!(
  51                 ErrorKind::InvalidInput,
  52                 "nul byte found in provided data",
  53             ));
  54         }
  55
  56         let (ours, theirs) = self.setup_io(default, needs_stdin)?;
  57
  58         if let Some(ret) = self.posix_spawn(&theirs, envp.as_ref())? {
  59             return Ok((ret, ours));
  60         }
  61
  62         let (input, output) = sys::pipe::anon_pipe()?;
  63
  64         // Whatever happens after the fork is almost for sure going to touch or
  65         // look at the environment in one way or another (PATH in `execvp` or
  66         // accessing the `environ` pointer ourselves). Make sure no other thread
  67         // is accessing the environment when we do the fork itself.
  68         //
  69         // Note that as soon as we're done with the fork there's no need to hold
  70         // a lock any more because the parent won't do anything and the child is
  71         // in its own process. Thus the parent drops the lock guard while the child
  72         // forgets it to avoid unlocking it on a new thread, which would be invalid.
  73         let env_lock = sys::os::env_read_lock();
  74         let (pid, pidfd) = unsafe { self.do_fork()? };
  75
  76         if pid == 0 {
  77             crate::panic::always_abort();
  78             mem::forget(env_lock);
  79             drop(input);
  80             let Err(err) = unsafe { self.do_exec(theirs, envp.as_ref()) };
  81             let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
  82             let errno = errno.to_be_bytes();
  83             let bytes = [
  84                 errno[0],
  85                 errno[1],
  86                 errno[2],
  87                 errno[3],
  88                 CLOEXEC_MSG_FOOTER[0],
  89                 CLOEXEC_MSG_FOOTER[1],
  90                 CLOEXEC_MSG_FOOTER[2],
  91                 CLOEXEC_MSG_FOOTER[3],
  92             ];
  93             // pipe I/O up to PIPE_BUF bytes should be atomic, and then
  94             // we want to be sure we *don't* run at_exit destructors as
  95             // we're being torn down regardless
  96             rtassert!(output.write(&bytes).is_ok());
  97             unsafe { libc::_exit(1) }
  98         }
  99
 100         drop(env_lock);
 101         drop(output);
 102
 103         // Safety: We obtained the pidfd from calling `clone3` with
 104         // `CLONE_PIDFD` so it's valid an otherwise unowned.
 105         let mut p = unsafe { Process::new(pid, pidfd) };
 106         let mut bytes = [0; 8];
 107
 108         // loop to handle EINTR
 109         loop {
 110             match input.read(&mut bytes) {
 111                 Ok(0) => return Ok((p, ours)),
 112                 Ok(8) => {
 113                     let (errno, footer) = bytes.split_at(4);
 114                     assert_eq!(
 115                         CLOEXEC_MSG_FOOTER, footer,
 116                         "Validation on the CLOEXEC pipe failed: {:?}",
 117                         bytes
 118                     );
 119                     let errno = i32::from_be_bytes(errno.try_into().unwrap());
 120                     assert!(p.wait().is_ok(), "wait() should either return Ok or panic");
 121                     return Err(Error::from_raw_os_error(errno));
 122                 }
 123                 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
 124                 Err(e) => {
 125                     assert!(p.wait().is_ok(), "wait() should either return Ok or panic");
 126                     panic!("the CLOEXEC pipe failed: {e:?}")
 127                 }
 128                 Ok(..) => {
 129                     // pipe I/O up to PIPE_BUF bytes should be atomic
 130                     assert!(p.wait().is_ok(), "wait() should either return Ok or panic");
 131                     panic!("short read on the CLOEXEC pipe")
 132                 }
 133             }
 134         }
 135     }
 136
 137     // Attempts to fork the process. If successful, returns Ok((0, -1))
 138     // in the child, and Ok((child_pid, -1)) in the parent.
 139     #[cfg(not(target_os = "linux"))]
 140     unsafe fn do_fork(&mut self) -> Result<(pid_t, pid_t), io::Error> {
 141         cvt(libc::fork()).map(|res| (res, -1))
 142     }
 143
 144     // Attempts to fork the process. If successful, returns Ok((0, -1))
 145     // in the child, and Ok((child_pid, child_pidfd)) in the parent.
 146     #[cfg(target_os = "linux")]
 147     unsafe fn do_fork(&mut self) -> Result<(pid_t, pid_t), io::Error> {
 148         use crate::sync::atomic::{AtomicBool, Ordering};
 149
 150         static HAS_CLONE3: AtomicBool = AtomicBool::new(true);
 151         const CLONE_PIDFD: u64 = 0x00001000;
 152
 153         #[repr(C)]
 154         struct clone_args {
 155             flags: u64,
 156             pidfd: u64,
 157             child_tid: u64,
 158             parent_tid: u64,
 159             exit_signal: u64,
 160             stack: u64,
 161             stack_size: u64,
 162             tls: u64,
 163             set_tid: u64,
 164             set_tid_size: u64,
 165             cgroup: u64,
 166         }
 167
 168         raw_syscall! {
 169             fn clone3(cl_args: *mut clone_args, len: libc::size_t) -> libc::c_long
 170         }
 171
 172         // Bypassing libc for `clone3` can make further libc calls unsafe,
 173         // so we use it sparingly for now. See #89522 for details.
 174         // Some tools (e.g. sandboxing tools) may also expect `fork`
 175         // rather than `clone3`.
 176         let want_clone3_pidfd = self.get_create_pidfd();
 177
 178         // If we fail to create a pidfd for any reason, this will
 179         // stay as -1, which indicates an error.
 180         let mut pidfd: pid_t = -1;
 181
 182         // Attempt to use the `clone3` syscall, which supports more arguments
 183         // (in particular, the ability to create a pidfd). If this fails,
 184         // we will fall through this block to a call to `fork()`
 185         if want_clone3_pidfd && HAS_CLONE3.load(Ordering::Relaxed) {
 186             let mut args = clone_args {
 187                 flags: CLONE_PIDFD,
 188                 pidfd: &mut pidfd as *mut pid_t as u64,
 189                 child_tid: 0,
 190                 parent_tid: 0,
 191                 exit_signal: libc::SIGCHLD as u64,
 192                 stack: 0,
 193                 stack_size: 0,
 194                 tls: 0,
 195                 set_tid: 0,
 196                 set_tid_size: 0,
 197                 cgroup: 0,
 198             };
 199
 200             let args_ptr = &mut args as *mut clone_args;
 201             let args_size = crate::mem::size_of::<clone_args>();
 202
 203             let res = cvt(clone3(args_ptr, args_size));
 204             match res {
 205                 Ok(n) => return Ok((n as pid_t, pidfd)),
 206                 Err(e) => match e.raw_os_error() {
 207                     // Multiple threads can race to execute this store,
 208                     // but that's fine - that just means that multiple threads
 209                     // will have tried and failed to execute the same syscall,
 210                     // with no other side effects.
 211                     Some(libc::ENOSYS) => HAS_CLONE3.store(false, Ordering::Relaxed),
 212                     // Fallback to fork if `EPERM` is returned. (e.g. blocked by seccomp)
 213                     Some(libc::EPERM) => {}
 214                     _ => return Err(e),
 215                 },
 216             }
 217         }
 218
 219         // Generally, we just call `fork`. If we get here after wanting `clone3`,
 220         // then the syscall does not exist or we do not have permission to call it.
 221         cvt(libc::fork()).map(|res| (res, pidfd))
 222     }
 223
 224     pub fn exec(&mut self, default: Stdio) -> io::Error {
 225         let envp = self.capture_env();
 226
 227         if self.saw_nul() {
 228             return io::const_io_error!(ErrorKind::InvalidInput, "nul byte found in provided data",);
 229         }
 230
 231         match self.setup_io(default, true) {
 232             Ok((_, theirs)) => {
 233                 unsafe {
 234                     // Similar to when forking, we want to ensure that access to
 235                     // the environment is synchronized, so make sure to grab the
 236                     // environment lock before we try to exec.
 237                     let _lock = sys::os::env_read_lock();
 238
 239                     let Err(e) = self.do_exec(theirs, envp.as_ref());
 240                     e
 241                 }
 242             }
 243             Err(e) => e,
 244         }
 245     }
 246
 247     // And at this point we've reached a special time in the life of the
 248     // child. The child must now be considered hamstrung and unable to
 249     // do anything other than syscalls really. Consider the following
 250     // scenario:
 251     //
 252     //      1. Thread A of process 1 grabs the malloc() mutex
 253     //      2. Thread B of process 1 forks(), creating thread C
 254     //      3. Thread C of process 2 then attempts to malloc()
 255     //      4. The memory of process 2 is the same as the memory of
 256     //         process 1, so the mutex is locked.
 257     //
 258     // This situation looks a lot like deadlock, right? It turns out
 259     // that this is what pthread_atfork() takes care of, which is
 260     // presumably implemented across platforms. The first thing that
 261     // threads to *before* forking is to do things like grab the malloc
 262     // mutex, and then after the fork they unlock it.
 263     //
 264     // Despite this information, libnative's spawn has been witnessed to
 265     // deadlock on both macOS and FreeBSD. I'm not entirely sure why, but
 266     // all collected backtraces point at malloc/free traffic in the
 267     // child spawned process.
 268     //
 269     // For this reason, the block of code below should contain 0
 270     // invocations of either malloc of free (or their related friends).
 271     //
 272     // As an example of not having malloc/free traffic, we don't close
 273     // this file descriptor by dropping the FileDesc (which contains an
 274     // allocation). Instead we just close it manually. This will never
 275     // have the drop glue anyway because this code never returns (the
 276     // child will either exec() or invoke libc::exit)
 277     unsafe fn do_exec(
 278         &mut self,
 279         stdio: ChildPipes,
 280         maybe_envp: Option<&CStringArray>,
 281     ) -> Result<!, io::Error> {
 282         use crate::sys::{self, cvt_r};
 283
 284         if let Some(fd) = stdio.stdin.fd() {
 285             cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO))?;
 286         }
 287         if let Some(fd) = stdio.stdout.fd() {
 288             cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO))?;
 289         }
 290         if let Some(fd) = stdio.stderr.fd() {
 291             cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO))?;
 292         }
 293
 294         #[cfg(not(target_os = "l4re"))]
 295         {
 296             if let Some(_g) = self.get_groups() {
 297                 //FIXME: Redox kernel does not support setgroups yet
 298                 #[cfg(not(target_os = "redox"))]
 299                 cvt(libc::setgroups(_g.len().try_into().unwrap(), _g.as_ptr()))?;
 300             }
 301             if let Some(u) = self.get_gid() {
 302                 cvt(libc::setgid(u as gid_t))?;
 303             }
 304             if let Some(u) = self.get_uid() {
 305                 // When dropping privileges from root, the `setgroups` call
 306                 // will remove any extraneous groups. We only drop groups
 307                 // if the current uid is 0 and we weren't given an explicit
 308                 // set of groups. If we don't call this, then even though our
 309                 // uid has dropped, we may still have groups that enable us to
 310                 // do super-user things.
 311                 //FIXME: Redox kernel does not support setgroups yet
 312                 #[cfg(not(target_os = "redox"))]
 313                 if libc::getuid() == 0 && self.get_groups().is_none() {
 314                     cvt(libc::setgroups(0, ptr::null()))?;
 315                 }
 316                 cvt(libc::setuid(u as uid_t))?;
 317             }
 318         }
 319         if let Some(ref cwd) = *self.get_cwd() {
 320             cvt(libc::chdir(cwd.as_ptr()))?;
 321         }
 322
 323         if let Some(pgroup) = self.get_pgroup() {
 324             cvt(libc::setpgid(0, pgroup))?;
 325         }
 326
 327         // emscripten has no signal support.
 328         #[cfg(not(target_os = "emscripten"))]
 329         {
 330             use crate::mem::MaybeUninit;
 331             // Reset signal handling so the child process starts in a
 332             // standardized state. libstd ignores SIGPIPE, and signal-handling
 333             // libraries often set a mask. Child processes inherit ignored
 334             // signals and the signal mask from their parent, but most
 335             // UNIX programs do not reset these things on their own, so we
 336             // need to clean things up now to avoid confusing the program
 337             // we're about to run.
 338             let mut set = MaybeUninit::<libc::sigset_t>::uninit();
 339             cvt(sigemptyset(set.as_mut_ptr()))?;
 340             cvt(libc::pthread_sigmask(libc::SIG_SETMASK, set.as_ptr(), ptr::null_mut()))?;
 341
 342             #[cfg(target_os = "android")] // see issue #88585
 343             {
 344                 let mut action: libc::sigaction = mem::zeroed();
 345                 action.sa_sigaction = libc::SIG_DFL;
 346                 cvt(libc::sigaction(libc::SIGPIPE, &action, ptr::null_mut()))?;
 347             }
 348             #[cfg(not(target_os = "android"))]
 349             {
 350                 let ret = sys::signal(libc::SIGPIPE, libc::SIG_DFL);
 351                 if ret == libc::SIG_ERR {
 352                     return Err(io::Error::last_os_error());
 353                 }
 354             }
 355         }
 356
 357         for callback in self.get_closures().iter_mut() {
 358             callback()?;
 359         }
 360
 361         // Although we're performing an exec here we may also return with an
 362         // error from this function (without actually exec'ing) in which case we
 363         // want to be sure to restore the global environment back to what it
 364         // once was, ensuring that our temporary override, when free'd, doesn't
 365         // corrupt our process's environment.
 366         let mut _reset = None;
 367         if let Some(envp) = maybe_envp {
 368             struct Reset(*const *const libc::c_char);
 369
 370             impl Drop for Reset {
 371                 fn drop(&mut self) {
 372                     unsafe {
 373                         *sys::os::environ() = self.0;
 374                     }
 375                 }
 376             }
 377
 378             _reset = Some(Reset(*sys::os::environ()));
 379             *sys::os::environ() = envp.as_ptr();
 380         }
 381
 382         libc::execvp(self.get_program_cstr().as_ptr(), self.get_argv().as_ptr());
 383         Err(io::Error::last_os_error())
 384     }
 385
 386     #[cfg(not(any(
 387         target_os = "macos",
 388         target_os = "freebsd",
 389         all(target_os = "linux", target_env = "gnu"),
 390         all(target_os = "linux", target_env = "musl"),
 391     )))]
 392     fn posix_spawn(
 393         &mut self,
 394         _: &ChildPipes,
 395         _: Option<&CStringArray>,
 396     ) -> io::Result<Option<Process>> {
 397         Ok(None)
 398     }
 399
 400     // Only support platforms for which posix_spawn() can return ENOENT
 401     // directly.
 402     #[cfg(any(
 403         target_os = "macos",
 404         target_os = "freebsd",
 405         all(target_os = "linux", target_env = "gnu"),
 406         all(target_os = "linux", target_env = "musl"),
 407     ))]
 408     fn posix_spawn(
 409         &mut self,
 410         stdio: &ChildPipes,
 411         envp: Option<&CStringArray>,
 412     ) -> io::Result<Option<Process>> {
 413         use crate::mem::MaybeUninit;
 414         use crate::sys::{self, cvt_nz};
 415
 416         if self.get_gid().is_some()
 417             || self.get_uid().is_some()
 418             || (self.env_saw_path() && !self.program_is_path())
 419             || !self.get_closures().is_empty()
 420             || self.get_groups().is_some()
 421             || self.get_create_pidfd()
 422         {
 423             return Ok(None);
 424         }
 425
 426         // Only glibc 2.24+ posix_spawn() supports returning ENOENT directly.
 427         #[cfg(all(target_os = "linux", target_env = "gnu"))]
 428         {
 429             if let Some(version) = sys::os::glibc_version() {
 430                 if version < (2, 24) {
 431                     return Ok(None);
 432                 }
 433             } else {
 434                 return Ok(None);
 435             }
 436         }
 437
 438         // Solaris, glibc 2.29+, and musl 1.24+ can set a new working directory,
 439         // and maybe others will gain this non-POSIX function too. We'll check
 440         // for this weak symbol as soon as it's needed, so we can return early
 441         // otherwise to do a manual chdir before exec.
 442         weak! {
 443             fn posix_spawn_file_actions_addchdir_np(
 444                 *mut libc::posix_spawn_file_actions_t,
 445                 *const libc::c_char
 446             ) -> libc::c_int
 447         }
 448         let addchdir = match self.get_cwd() {
 449             Some(cwd) => {
 450                 if cfg!(target_os = "macos") {
 451                     // There is a bug in macOS where a relative executable
 452                     // path like "../myprogram" will cause `posix_spawn` to
 453                     // successfully launch the program, but erroneously return
 454                     // ENOENT when used with posix_spawn_file_actions_addchdir_np
 455                     // which was introduced in macOS 10.15.
 456                     return Ok(None);
 457                 }
 458                 match posix_spawn_file_actions_addchdir_np.get() {
 459                     Some(f) => Some((f, cwd)),
 460                     None => return Ok(None),
 461                 }
 462             }
 463             None => None,
 464         };
 465
 466         let pgroup = self.get_pgroup();
 467
 468         // Safety: -1 indicates we don't have a pidfd.
 469         let mut p = unsafe { Process::new(0, -1) };
 470
 471         struct PosixSpawnFileActions<'a>(&'a mut MaybeUninit<libc::posix_spawn_file_actions_t>);
 472
 473         impl Drop for PosixSpawnFileActions<'_> {
 474             fn drop(&mut self) {
 475                 unsafe {
 476                     libc::posix_spawn_file_actions_destroy(self.0.as_mut_ptr());
 477                 }
 478             }
 479         }
 480
 481         struct PosixSpawnattr<'a>(&'a mut MaybeUninit<libc::posix_spawnattr_t>);
 482
 483         impl Drop for PosixSpawnattr<'_> {
 484             fn drop(&mut self) {
 485                 unsafe {
 486                     libc::posix_spawnattr_destroy(self.0.as_mut_ptr());
 487                 }
 488             }
 489         }
 490
 491         unsafe {
 492             let mut attrs = MaybeUninit::uninit();
 493             cvt_nz(libc::posix_spawnattr_init(attrs.as_mut_ptr()))?;
 494             let attrs = PosixSpawnattr(&mut attrs);
 495
 496             let mut flags = 0;
 497
 498             let mut file_actions = MaybeUninit::uninit();
 499             cvt_nz(libc::posix_spawn_file_actions_init(file_actions.as_mut_ptr()))?;
 500             let file_actions = PosixSpawnFileActions(&mut file_actions);
 501
 502             if let Some(fd) = stdio.stdin.fd() {
 503                 cvt_nz(libc::posix_spawn_file_actions_adddup2(
 504                     file_actions.0.as_mut_ptr(),
 505                     fd,
 506                     libc::STDIN_FILENO,
 507                 ))?;
 508             }
 509             if let Some(fd) = stdio.stdout.fd() {
 510                 cvt_nz(libc::posix_spawn_file_actions_adddup2(
 511                     file_actions.0.as_mut_ptr(),
 512                     fd,
 513                     libc::STDOUT_FILENO,
 514                 ))?;
 515             }
 516             if let Some(fd) = stdio.stderr.fd() {
 517                 cvt_nz(libc::posix_spawn_file_actions_adddup2(
 518                     file_actions.0.as_mut_ptr(),
 519                     fd,
 520                     libc::STDERR_FILENO,
 521                 ))?;
 522             }
 523             if let Some((f, cwd)) = addchdir {
 524                 cvt_nz(f(file_actions.0.as_mut_ptr(), cwd.as_ptr()))?;
 525             }
 526
 527             if let Some(pgroup) = pgroup {
 528                 flags |= libc::POSIX_SPAWN_SETPGROUP;
 529                 cvt_nz(libc::posix_spawnattr_setpgroup(attrs.0.as_mut_ptr(), pgroup))?;
 530             }
 531
 532             let mut set = MaybeUninit::<libc::sigset_t>::uninit();
 533             cvt(sigemptyset(set.as_mut_ptr()))?;
 534             cvt_nz(libc::posix_spawnattr_setsigmask(attrs.0.as_mut_ptr(), set.as_ptr()))?;
 535             cvt(sigaddset(set.as_mut_ptr(), libc::SIGPIPE))?;
 536             cvt_nz(libc::posix_spawnattr_setsigdefault(attrs.0.as_mut_ptr(), set.as_ptr()))?;
 537
 538             flags |= libc::POSIX_SPAWN_SETSIGDEF | libc::POSIX_SPAWN_SETSIGMASK;
 539             cvt_nz(libc::posix_spawnattr_setflags(attrs.0.as_mut_ptr(), flags as _))?;
 540
 541             // Make sure we synchronize access to the global `environ` resource
 542             let _env_lock = sys::os::env_read_lock();
 543             let envp = envp.map(|c| c.as_ptr()).unwrap_or_else(|| *sys::os::environ() as *const _);
 544             cvt_nz(libc::posix_spawnp(
 545                 &mut p.pid,
 546                 self.get_program_cstr().as_ptr(),
 547                 file_actions.0.as_ptr(),
 548                 attrs.0.as_ptr(),
 549                 self.get_argv().as_ptr() as *const _,
 550                 envp as *const _,
 551             ))?;
 552             Ok(Some(p))
 553         }
 554     }
 555 }
 556
 557 ////////////////////////////////////////////////////////////////////////////////
 558 // Processes
 559 ////////////////////////////////////////////////////////////////////////////////
 560
 561 /// The unique ID of the process (this should never be negative).
 562 pub struct Process {
 563     pid: pid_t,
 564     status: Option<ExitStatus>,
 565     // On Linux, stores the pidfd created for this child.
 566     // This is None if the user did not request pidfd creation,
 567     // or if the pidfd could not be created for some reason
 568     // (e.g. the `clone3` syscall was not available).
 569     #[cfg(target_os = "linux")]
 570     pidfd: Option<PidFd>,
 571 }
 572
 573 impl Process {
 574     #[cfg(target_os = "linux")]
 575     unsafe fn new(pid: pid_t, pidfd: pid_t) -> Self {
 576         use crate::os::unix::io::FromRawFd;
 577         use crate::sys_common::FromInner;
 578         // Safety: If `pidfd` is nonnegative, we assume it's valid and otherwise unowned.
 579         let pidfd = (pidfd >= 0).then(|| PidFd::from_inner(sys::fd::FileDesc::from_raw_fd(pidfd)));
 580         Process { pid, status: None, pidfd }
 581     }
 582
 583     #[cfg(not(target_os = "linux"))]
 584     unsafe fn new(pid: pid_t, _pidfd: pid_t) -> Self {
 585         Process { pid, status: None }
 586     }
 587
 588     pub fn id(&self) -> u32 {
 589         self.pid as u32
 590     }
 591
 592     pub fn kill(&mut self) -> io::Result<()> {
 593         // If we've already waited on this process then the pid can be recycled
 594         // and used for another process, and we probably shouldn't be killing
 595         // random processes, so just return an error.
 596         if self.status.is_some() {
 597             Err(io::const_io_error!(
 598                 ErrorKind::InvalidInput,
 599                 "invalid argument: can't kill an exited process",
 600             ))
 601         } else {
 602             cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(drop)
 603         }
 604     }
 605
 606     pub fn wait(&mut self) -> io::Result<ExitStatus> {
 607         use crate::sys::cvt_r;
 608         if let Some(status) = self.status {
 609             return Ok(status);
 610         }
 611         let mut status = 0 as c_int;
 612         cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?;
 613         self.status = Some(ExitStatus::new(status));
 614         Ok(ExitStatus::new(status))
 615     }
 616
 617     pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
 618         if let Some(status) = self.status {
 619             return Ok(Some(status));
 620         }
 621         let mut status = 0 as c_int;
 622         let pid = cvt(unsafe { libc::waitpid(self.pid, &mut status, libc::WNOHANG) })?;
 623         if pid == 0 {
 624             Ok(None)
 625         } else {
 626             self.status = Some(ExitStatus::new(status));
 627             Ok(Some(ExitStatus::new(status)))
 628         }
 629     }
 630 }
 631
 632 /// Unix exit statuses
 633 //
 634 // This is not actually an "exit status" in Unix terminology.  Rather, it is a "wait status".
 635 // See the discussion in comments and doc comments for `std::process::ExitStatus`.
 636 #[derive(PartialEq, Eq, Clone, Copy)]
 637 pub struct ExitStatus(c_int);
 638
 639 impl fmt::Debug for ExitStatus {
 640     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 641         f.debug_tuple("unix_wait_status").field(&self.0).finish()
 642     }
 643 }
 644
 645 impl ExitStatus {
 646     pub fn new(status: c_int) -> ExitStatus {
 647         ExitStatus(status)
 648     }
 649
 650     fn exited(&self) -> bool {
 651         libc::WIFEXITED(self.0)
 652     }
 653
 654     pub fn exit_ok(&self) -> Result<(), ExitStatusError> {
 655         // This assumes that WIFEXITED(status) && WEXITSTATUS==0 corresponds to status==0.  This is
 656         // true on all actual versions of Unix, is widely assumed, and is specified in SuS
 657         // https://pubs.opengroup.org/onlinepubs/9699919799/functions/wait.html .  If it is not
 658         // true for a platform pretending to be Unix, the tests (our doctests, and also
 659         // procsss_unix/tests.rs) will spot it.  `ExitStatusError::code` assumes this too.
 660         match NonZero_c_int::try_from(self.0) {
 661             /* was nonzero */ Ok(failure) => Err(ExitStatusError(failure)),
 662             /* was zero, couldn't convert */ Err(_) => Ok(()),
 663         }
 664     }
 665
 666     pub fn code(&self) -> Option<i32> {
 667         self.exited().then(|| libc::WEXITSTATUS(self.0))
 668     }
 669
 670     pub fn signal(&self) -> Option<i32> {
 671         libc::WIFSIGNALED(self.0).then(|| libc::WTERMSIG(self.0))
 672     }
 673
 674     pub fn core_dumped(&self) -> bool {
 675         libc::WIFSIGNALED(self.0) && libc::WCOREDUMP(self.0)
 676     }
 677
 678     pub fn stopped_signal(&self) -> Option<i32> {
 679         libc::WIFSTOPPED(self.0).then(|| libc::WSTOPSIG(self.0))
 680     }
 681
 682     pub fn continued(&self) -> bool {
 683         libc::WIFCONTINUED(self.0)
 684     }
 685
 686     pub fn into_raw(&self) -> c_int {
 687         self.0
 688     }
 689 }
 690
 691 /// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying.
 692 impl From<c_int> for ExitStatus {
 693     fn from(a: c_int) -> ExitStatus {
 694         ExitStatus(a)
 695     }
 696 }
 697
 698 impl fmt::Display for ExitStatus {
 699     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 700         if let Some(code) = self.code() {
 701             write!(f, "exit status: {code}")
 702         } else if let Some(signal) = self.signal() {
 703             if self.core_dumped() {
 704                 write!(f, "signal: {signal} (core dumped)")
 705             } else {
 706                 write!(f, "signal: {signal}")
 707             }
 708         } else if let Some(signal) = self.stopped_signal() {
 709             write!(f, "stopped (not terminated) by signal: {signal}")
 710         } else if self.continued() {
 711             write!(f, "continued (WIFCONTINUED)")
 712         } else {
 713             write!(f, "unrecognised wait status: {} {:#x}", self.0, self.0)
 714         }
 715     }
 716 }
 717
 718 #[derive(PartialEq, Eq, Clone, Copy)]
 719 pub struct ExitStatusError(NonZero_c_int);
 720
 721 impl Into<ExitStatus> for ExitStatusError {
 722     fn into(self) -> ExitStatus {
 723         ExitStatus(self.0.into())
 724     }
 725 }
 726
 727 impl fmt::Debug for ExitStatusError {
 728     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 729         f.debug_tuple("unix_wait_status").field(&self.0).finish()
 730     }
 731 }
 732
 733 impl ExitStatusError {
 734     pub fn code(self) -> Option<NonZeroI32> {
 735         ExitStatus(self.0.into()).code().map(|st| st.try_into().unwrap())
 736     }
 737 }
 738
 739 #[cfg(target_os = "linux")]
 740 #[unstable(feature = "linux_pidfd", issue = "82971")]
 741 impl crate::os::linux::process::ChildExt for crate::process::Child {
 742     fn pidfd(&self) -> io::Result<&PidFd> {
 743         self.handle
 744             .pidfd
 745             .as_ref()
 746             .ok_or_else(|| Error::new(ErrorKind::Other, "No pidfd was created."))
 747     }
 748
 749     fn take_pidfd(&mut self) -> io::Result<PidFd> {
 750         self.handle
 751             .pidfd
 752             .take()
 753             .ok_or_else(|| Error::new(ErrorKind::Other, "No pidfd was created."))
 754     }
 755 }
 756
 757 #[cfg(test)]
 758 #[path = "process_unix/tests.rs"]
 759 mod tests;