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use crate::runner::prelude::*;
const PID0: nix::unistd::Pid = nix::unistd::Pid::from_raw(0);
pub fn pipe() -> Result<(std::fs::File, std::fs::File)> {
let (r, w) = nix::unistd::pipe2(nix::fcntl::OFlag::O_CLOEXEC)?;
// Safety: these file descriptors were just returned by pipe2 above, and
// are only available in this function, so nothing else can be accessing
// them
Ok((unsafe { std::fs::File::from_raw_fd(r) }, unsafe {
std::fs::File::from_raw_fd(w)
}))
}
pub fn set_foreground_pg(pg: nix::unistd::Pid) -> Result<()> {
let pty = nix::fcntl::open(
"/dev/tty",
nix::fcntl::OFlag::empty(),
nix::sys::stat::Mode::empty(),
)?;
// if a background process calls tcsetpgrp, the kernel will send it
// SIGTTOU which suspends it. if that background process is the session
// leader and doesn't have SIGTTOU blocked, the kernel will instead just
// return ENOTTY from the tcsetpgrp call rather than sending a signal to
// avoid deadlocking the process. therefore, we need to ensure that
// SIGTTOU is blocked here.
// Safety: setting a signal handler to SigIgn is always safe
unsafe {
nix::sys::signal::signal(
nix::sys::signal::Signal::SIGTTOU,
nix::sys::signal::SigHandler::SigIgn,
)?;
}
let res = nix::unistd::tcsetpgrp(pty, pg);
// Safety: setting a signal handler to SigDfl is always safe
unsafe {
nix::sys::signal::signal(
nix::sys::signal::Signal::SIGTTOU,
nix::sys::signal::SigHandler::SigDfl,
)?;
}
res?;
nix::unistd::close(pty)?;
nix::sys::signal::kill(neg_pid(pg), nix::sys::signal::Signal::SIGCONT)
// the process group has already exited
.allow(nix::errno::Errno::ESRCH)?;
Ok(())
}
pub fn setpgid_child(pg: Option<nix::unistd::Pid>) -> std::io::Result<()> {
nix::unistd::setpgid(PID0, pg.unwrap_or(PID0))?;
Ok(())
}
pub fn setpgid_parent(
pid: nix::unistd::Pid,
pg: Option<nix::unistd::Pid>,
) -> Result<()> {
nix::unistd::setpgid(pid, pg.unwrap_or(PID0))
// the child already called exec, so it must have already called
// setpgid itself
.allow(nix::errno::Errno::EACCES)
// the child already exited, so we don't care
.allow(nix::errno::Errno::ESRCH)?;
Ok(())
}
pub fn id_to_pid(id: u32) -> nix::unistd::Pid {
nix::unistd::Pid::from_raw(id.try_into().unwrap())
}
pub fn neg_pid(pid: nix::unistd::Pid) -> nix::unistd::Pid {
nix::unistd::Pid::from_raw(-pid.as_raw())
}
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