Revision control
Copy as Markdown
Other Tools
//! Wait for a process to change status
use crate::errno::Errno;
use crate::sys::signal::Signal;
use crate::unistd::Pid;
use crate::Result;
use cfg_if::cfg_if;
use libc::{self, c_int};
use std::convert::TryFrom;
#[cfg(any(
target_os = "android",
all(target_os = "linux", not(target_env = "uclibc")),
))]
use std::os::unix::io::{AsRawFd, BorrowedFd};
libc_bitflags!(
/// Controls the behavior of [`waitpid`].
pub struct WaitPidFlag: c_int {
/// Do not block when there are no processes wishing to report status.
WNOHANG;
/// Report the status of selected processes which are stopped due to a
/// [`SIGTTIN`](crate::sys::signal::Signal::SIGTTIN),
/// [`SIGTTOU`](crate::sys::signal::Signal::SIGTTOU),
/// [`SIGTSTP`](crate::sys::signal::Signal::SIGTSTP), or
/// [`SIGSTOP`](crate::sys::signal::Signal::SIGSTOP) signal.
WUNTRACED;
/// Report the status of selected processes which have terminated.
#[cfg(any(linux_android,
apple_targets,
target_os = "freebsd",
target_os = "haiku",
target_os = "redox",
target_os = "netbsd"))]
WEXITED;
/// Report the status of selected processes that have continued from a
/// job control stop by receiving a
/// [`SIGCONT`](crate::sys::signal::Signal::SIGCONT) signal.
WCONTINUED;
/// An alias for WUNTRACED.
#[cfg(any(linux_android,
apple_targets,
target_os = "freebsd",
target_os = "haiku",
target_os = "redox",
target_os = "netbsd"))]
WSTOPPED;
/// Don't reap, just poll status.
#[cfg(any(linux_android,
apple_targets,
target_os = "freebsd",
target_os = "haiku",
target_os = "redox",
target_os = "netbsd"))]
WNOWAIT;
/// Don't wait on children of other threads in this group
#[cfg(any(linux_android, target_os = "redox"))]
__WNOTHREAD;
/// Wait on all children, regardless of type
#[cfg(any(linux_android, target_os = "redox"))]
__WALL;
/// Wait for "clone" children only.
#[cfg(any(linux_android, target_os = "redox"))]
__WCLONE;
}
);
/// Possible return values from `wait()` or `waitpid()`.
///
/// Each status (other than `StillAlive`) describes a state transition
/// in a child process `Pid`, such as the process exiting or stopping,
/// plus additional data about the transition if any.
///
/// Note that there are two Linux-specific enum variants, `PtraceEvent`
/// and `PtraceSyscall`. Portable code should avoid exhaustively
/// matching on `WaitStatus`.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum WaitStatus {
/// The process exited normally (as with `exit()` or returning from
/// `main`) with the given exit code. This case matches the C macro
/// `WIFEXITED(status)`; the second field is `WEXITSTATUS(status)`.
Exited(Pid, i32),
/// The process was killed by the given signal. The third field
/// indicates whether the signal generated a core dump. This case
/// matches the C macro `WIFSIGNALED(status)`; the last two fields
/// correspond to `WTERMSIG(status)` and `WCOREDUMP(status)`.
Signaled(Pid, Signal, bool),
/// The process is alive, but was stopped by the given signal. This
/// is only reported if `WaitPidFlag::WUNTRACED` was passed. This
/// case matches the C macro `WIFSTOPPED(status)`; the second field
/// is `WSTOPSIG(status)`.
Stopped(Pid, Signal),
/// The traced process was stopped by a `PTRACE_EVENT_*` event. See
/// [`nix::sys::ptrace`] and [`ptrace`(2)] for more information. All
/// currently-defined events use `SIGTRAP` as the signal; the third
/// field is the `PTRACE_EVENT_*` value of the event.
///
/// [`nix::sys::ptrace`]: ../ptrace/index.html
#[cfg(linux_android)]
PtraceEvent(Pid, Signal, c_int),
/// The traced process was stopped by execution of a system call,
/// and `PTRACE_O_TRACESYSGOOD` is in effect. See [`ptrace`(2)] for
/// more information.
///
#[cfg(linux_android)]
PtraceSyscall(Pid),
/// The process was previously stopped but has resumed execution
/// after receiving a `SIGCONT` signal. This is only reported if
/// `WaitPidFlag::WCONTINUED` was passed. This case matches the C
/// macro `WIFCONTINUED(status)`.
Continued(Pid),
/// There are currently no state changes to report in any awaited
/// child process. This is only returned if `WaitPidFlag::WNOHANG`
/// was used (otherwise `wait()` or `waitpid()` would block until
/// there was something to report).
StillAlive,
}
impl WaitStatus {
/// Extracts the PID from the WaitStatus unless it equals StillAlive.
pub fn pid(&self) -> Option<Pid> {
use self::WaitStatus::*;
match *self {
Exited(p, _) | Signaled(p, _, _) | Stopped(p, _) | Continued(p) => {
Some(p)
}
StillAlive => None,
#[cfg(linux_android)]
PtraceEvent(p, _, _) | PtraceSyscall(p) => Some(p),
}
}
}
fn exited(status: i32) -> bool {
libc::WIFEXITED(status)
}
fn exit_status(status: i32) -> i32 {
libc::WEXITSTATUS(status)
}
fn signaled(status: i32) -> bool {
libc::WIFSIGNALED(status)
}
fn term_signal(status: i32) -> Result<Signal> {
Signal::try_from(libc::WTERMSIG(status))
}
fn dumped_core(status: i32) -> bool {
libc::WCOREDUMP(status)
}
fn stopped(status: i32) -> bool {
libc::WIFSTOPPED(status)
}
fn stop_signal(status: i32) -> Result<Signal> {
Signal::try_from(libc::WSTOPSIG(status))
}
#[cfg(linux_android)]
fn syscall_stop(status: i32) -> bool {
// From ptrace(2), setting PTRACE_O_TRACESYSGOOD has the effect
// of delivering SIGTRAP | 0x80 as the signal number for syscall
// stops. This allows easily distinguishing syscall stops from
// genuine SIGTRAP signals.
libc::WSTOPSIG(status) == libc::SIGTRAP | 0x80
}
#[cfg(linux_android)]
fn stop_additional(status: i32) -> c_int {
(status >> 16) as c_int
}
fn continued(status: i32) -> bool {
libc::WIFCONTINUED(status)
}
impl WaitStatus {
/// Convert a raw `wstatus` as returned by `waitpid`/`wait` into a `WaitStatus`
///
/// # Errors
///
/// Returns an `Error` corresponding to `EINVAL` for invalid status values.
///
/// # Examples
///
/// Convert a `wstatus` obtained from `libc::waitpid` into a `WaitStatus`:
///
/// ```
/// use nix::sys::wait::WaitStatus;
/// use nix::sys::signal::Signal;
/// let pid = nix::unistd::Pid::from_raw(1);
/// let status = WaitStatus::from_raw(pid, 0x0002);
/// assert_eq!(status, Ok(WaitStatus::Signaled(pid, Signal::SIGINT, false)));
/// ```
pub fn from_raw(pid: Pid, status: i32) -> Result<WaitStatus> {
Ok(if exited(status) {
WaitStatus::Exited(pid, exit_status(status))
} else if signaled(status) {
WaitStatus::Signaled(pid, term_signal(status)?, dumped_core(status))
} else if stopped(status) {
cfg_if! {
if #[cfg(linux_android)] {
fn decode_stopped(pid: Pid, status: i32) -> Result<WaitStatus> {
let status_additional = stop_additional(status);
Ok(if syscall_stop(status) {
WaitStatus::PtraceSyscall(pid)
} else if status_additional == 0 {
WaitStatus::Stopped(pid, stop_signal(status)?)
} else {
WaitStatus::PtraceEvent(pid, stop_signal(status)?,
stop_additional(status))
})
}
} else {
fn decode_stopped(pid: Pid, status: i32) -> Result<WaitStatus> {
Ok(WaitStatus::Stopped(pid, stop_signal(status)?))
}
}
}
return decode_stopped(pid, status);
} else {
assert!(continued(status));
WaitStatus::Continued(pid)
})
}
/// Convert a `siginfo_t` as returned by `waitid` to a `WaitStatus`
///
/// # Errors
///
/// Returns an `Error` corresponding to `EINVAL` for invalid values.
///
/// # Safety
///
/// siginfo_t is actually a union, not all fields may be initialized.
/// The functions si_pid() and si_status() must be valid to call on
/// the passed siginfo_t.
#[cfg(any(
target_os = "android",
target_os = "freebsd",
target_os = "haiku",
all(target_os = "linux", not(target_env = "uclibc")),
))]
unsafe fn from_siginfo(siginfo: &libc::siginfo_t) -> Result<WaitStatus> {
let si_pid = unsafe { siginfo.si_pid() };
if si_pid == 0 {
return Ok(WaitStatus::StillAlive);
}
assert_eq!(siginfo.si_signo, libc::SIGCHLD);
let pid = Pid::from_raw(si_pid);
let si_status = unsafe { siginfo.si_status() };
let status = match siginfo.si_code {
libc::CLD_EXITED => WaitStatus::Exited(pid, si_status),
libc::CLD_KILLED | libc::CLD_DUMPED => WaitStatus::Signaled(
pid,
Signal::try_from(si_status)?,
siginfo.si_code == libc::CLD_DUMPED,
),
libc::CLD_STOPPED => {
WaitStatus::Stopped(pid, Signal::try_from(si_status)?)
}
libc::CLD_CONTINUED => WaitStatus::Continued(pid),
#[cfg(linux_android)]
libc::CLD_TRAPPED => {
if si_status == libc::SIGTRAP | 0x80 {
WaitStatus::PtraceSyscall(pid)
} else {
WaitStatus::PtraceEvent(
pid,
Signal::try_from(si_status & 0xff)?,
(si_status >> 8) as c_int,
)
}
}
_ => return Err(Errno::EINVAL),
};
Ok(status)
}
}
/// Wait for a process to change status
///
pub fn waitpid<P: Into<Option<Pid>>>(
pid: P,
options: Option<WaitPidFlag>,
) -> Result<WaitStatus> {
use self::WaitStatus::*;
let mut status: i32 = 0;
let option_bits = match options {
Some(bits) => bits.bits(),
None => 0,
};
let res = unsafe {
libc::waitpid(
pid.into().unwrap_or_else(|| Pid::from_raw(-1)).into(),
&mut status as *mut c_int,
option_bits,
)
};
match Errno::result(res)? {
0 => Ok(StillAlive),
res => WaitStatus::from_raw(Pid::from_raw(res), status),
}
}
/// Wait for any child process to change status or a signal is received.
///
pub fn wait() -> Result<WaitStatus> {
waitpid(None, None)
}
/// The ID argument for `waitid`
#[cfg(any(
target_os = "android",
target_os = "freebsd",
target_os = "haiku",
all(target_os = "linux", not(target_env = "uclibc")),
))]
#[derive(Debug)]
pub enum Id<'fd> {
/// Wait for any child
All,
/// Wait for the child whose process ID matches the given PID
Pid(Pid),
/// Wait for the child whose process group ID matches the given PID
///
/// If the PID is zero, the caller's process group is used since Linux 5.4.
PGid(Pid),
/// Wait for the child referred to by the given PID file descriptor
#[cfg(linux_android)]
PIDFd(BorrowedFd<'fd>),
/// A helper variant to resolve the unused parameter (`'fd`) problem on platforms
/// other than Linux and Android.
#[doc(hidden)]
_Unreachable(std::marker::PhantomData<&'fd std::convert::Infallible>),
}
/// Wait for a process to change status
///
#[cfg(any(
target_os = "android",
target_os = "freebsd",
target_os = "haiku",
all(target_os = "linux", not(target_env = "uclibc")),
))]
pub fn waitid(id: Id, flags: WaitPidFlag) -> Result<WaitStatus> {
let (idtype, idval) = match id {
Id::All => (libc::P_ALL, 0),
Id::Pid(pid) => (libc::P_PID, pid.as_raw() as libc::id_t),
Id::PGid(pid) => (libc::P_PGID, pid.as_raw() as libc::id_t),
#[cfg(linux_android)]
Id::PIDFd(fd) => (libc::P_PIDFD, fd.as_raw_fd() as libc::id_t),
Id::_Unreachable(_) => {
unreachable!("This variant could never be constructed")
}
};
let siginfo = unsafe {
// Memory is zeroed rather than uninitialized, as not all platforms
// initialize the memory in the StillAlive case
let mut siginfo: libc::siginfo_t = std::mem::zeroed();
Errno::result(libc::waitid(idtype, idval, &mut siginfo, flags.bits()))?;
siginfo
};
unsafe { WaitStatus::from_siginfo(&siginfo) }
}