1 files changed, 175 insertions, 0 deletions
diff --git a/third_party/rust/nix/src/sys/signalfd.rs b/third_party/rust/nix/src/sys/signalfd.rs
new file mode 100644
index 0000000000..095e590850
--- /dev/null
+++ b/third_party/rust/nix/src/sys/signalfd.rs
@@ -0,0 +1,175 @@
+//! Interface for the `signalfd` syscall.
+//!
+//! # Signal discarding
+//! When a signal can't be delivered to a process (or thread), it will become a pending signal.
+//! Failure to deliver could happen if the signal is blocked by every thread in the process or if
+//! the signal handler is still handling a previous signal.
+//!
+//! If a signal is sent to a process (or thread) that already has a pending signal of the same
+//! type, it will be discarded. This means that if signals of the same type are received faster than
+//! they are processed, some of those signals will be dropped. Because of this limitation,
+//! `signalfd` in itself cannot be used for reliable communication between processes or threads.
+//!
+//! Once the signal is unblocked, or the signal handler is finished, and a signal is still pending
+//! (ie. not consumed from a signalfd) it will be delivered to the signal handler.
+//!
+//! Please note that signal discarding is not specific to `signalfd`, but also happens with regular
+//! signal handlers.
+use crate::errno::Errno;
+pub use crate::sys::signal::{self, SigSet};
+use crate::unistd;
+use crate::Result;
+pub use libc::signalfd_siginfo as siginfo;
+
+use std::mem;
+use std::os::unix::io::{AsRawFd, RawFd};
+
+libc_bitflags! {
+    pub struct SfdFlags: libc::c_int {
+        SFD_NONBLOCK;
+        SFD_CLOEXEC;
+    }
+}
+
+pub const SIGNALFD_NEW: RawFd = -1;
+#[deprecated(since = "0.23.0", note = "use mem::size_of::<siginfo>() instead")]
+pub const SIGNALFD_SIGINFO_SIZE: usize = mem::size_of::<siginfo>();
+
+/// Creates a new file descriptor for reading signals.
+///
+/// **Important:** please read the module level documentation about signal discarding before using
+/// this function!
+///
+/// The `mask` parameter specifies the set of signals that can be accepted via this file descriptor.
+///
+/// A signal must be blocked on every thread in a process, otherwise it won't be visible from
+/// signalfd (the default handler will be invoked instead).
+///
+/// See [the signalfd man page for more information](https://man7.org/linux/man-pages/man2/signalfd.2.html)
+pub fn signalfd(fd: RawFd, mask: &SigSet, flags: SfdFlags) -> Result<RawFd> {
+    unsafe {
+        Errno::result(libc::signalfd(
+            fd as libc::c_int,
+            mask.as_ref(),
+            flags.bits(),
+        ))
+    }
+}
+
+/// A helper struct for creating, reading and closing a `signalfd` instance.
+///
+/// **Important:** please read the module level documentation about signal discarding before using
+/// this struct!
+///
+/// # Examples
+///
+/// ```
+/// # use nix::sys::signalfd::*;
+/// // Set the thread to block the SIGUSR1 signal, otherwise the default handler will be used
+/// let mut mask = SigSet::empty();
+/// mask.add(signal::SIGUSR1);
+/// mask.thread_block().unwrap();
+///
+/// // Signals are queued up on the file descriptor
+/// let mut sfd = SignalFd::with_flags(&mask, SfdFlags::SFD_NONBLOCK).unwrap();
+///
+/// match sfd.read_signal() {
+///     // we caught a signal
+///     Ok(Some(sig)) => (),
+///     // there were no signals waiting (only happens when the SFD_NONBLOCK flag is set,
+///     // otherwise the read_signal call blocks)
+///     Ok(None) => (),
+///     Err(err) => (), // some error happend
+/// }
+/// ```
+#[derive(Debug, Eq, Hash, PartialEq)]
+pub struct SignalFd(RawFd);
+
+impl SignalFd {
+    pub fn new(mask: &SigSet) -> Result<SignalFd> {
+        Self::with_flags(mask, SfdFlags::empty())
+    }
+
+    pub fn with_flags(mask: &SigSet, flags: SfdFlags) -> Result<SignalFd> {
+        let fd = signalfd(SIGNALFD_NEW, mask, flags)?;
+
+        Ok(SignalFd(fd))
+    }
+
+    pub fn set_mask(&mut self, mask: &SigSet) -> Result<()> {
+        signalfd(self.0, mask, SfdFlags::empty()).map(drop)
+    }
+
+    pub fn read_signal(&mut self) -> Result<Option<siginfo>> {
+        let mut buffer = mem::MaybeUninit::<siginfo>::uninit();
+
+        let size = mem::size_of_val(&buffer);
+        let res = Errno::result(unsafe {
+            libc::read(self.0, buffer.as_mut_ptr() as *mut libc::c_void, size)
+        })
+        .map(|r| r as usize);
+        match res {
+            Ok(x) if x == size => Ok(Some(unsafe { buffer.assume_init() })),
+            Ok(_) => unreachable!("partial read on signalfd"),
+            Err(Errno::EAGAIN) => Ok(None),
+            Err(error) => Err(error),
+        }
+    }
+}
+
+impl Drop for SignalFd {
+    fn drop(&mut self) {
+        let e = unistd::close(self.0);
+        if !std::thread::panicking() && e == Err(Errno::EBADF) {
+            panic!("Closing an invalid file descriptor!");
+        };
+    }
+}
+
+impl AsRawFd for SignalFd {
+    fn as_raw_fd(&self) -> RawFd {
+        self.0
+    }
+}
+
+impl Iterator for SignalFd {
+    type Item = siginfo;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.read_signal() {
+            Ok(Some(sig)) => Some(sig),
+            Ok(None) | Err(_) => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn create_signalfd() {
+        let mask = SigSet::empty();
+        SignalFd::new(&mask).unwrap();
+    }
+
+    #[test]
+    fn create_signalfd_with_opts() {
+        let mask = SigSet::empty();
+        SignalFd::with_flags(
+            &mask,
+            SfdFlags::SFD_CLOEXEC | SfdFlags::SFD_NONBLOCK,
+        )
+        .unwrap();
+    }
+
+    #[test]
+    fn read_empty_signalfd() {
+        let mask = SigSet::empty();
+        let mut fd =
+            SignalFd::with_flags(&mask, SfdFlags::SFD_NONBLOCK).unwrap();
+
+        let res = fd.read_signal();
+        assert!(res.unwrap().is_none());
+    }
+}