Add support for HermitOS

.github/workflows/ci.yml

@@ -62,16 +62,10 @@ jobs:
           RUSTFLAGS: ${{ env.RUSTFLAGS }} --cfg polling_test_epoll_pipe
         if: startsWith(matrix.os, 'ubuntu')
       - run: cargo hack build --feature-powerset --no-dev-deps
-      - name: Add rust-src
-        if: startsWith(matrix.rust, 'nightly')
-        run: rustup component add rust-src
       # TODO: broken due to https://github.com/rust-lang/rust/pull/119026.
       # - name: Check selected Tier 3 targets
       #   if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
       #   run: cargo check -Z build-std --target=riscv32imc-esp-espidf
-      - name: Check haiku
-        if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
-        run: cargo check -Z build-std --target x86_64-unknown-haiku
       - name: Clone async-io
         run: git clone https://github.com/smol-rs/async-io.git
         # The async-io Cargo.toml already has a patch section at the bottom, so we
@@ -93,6 +87,9 @@ jobs:
       run: rustup update stable
     - name: Install cross
       uses: taiki-e/install-action@cross
+    - name: Add rust-src
+      if: startsWith(matrix.rust, 'nightly')
+      run: rustup component add rust-src
     # We don't test BSDs, since we already test them in Cirrus.
     - name: Android
       if: startsWith(matrix.os, 'ubuntu')
@@ -118,9 +115,17 @@ jobs:
         rustup target add x86_64-unknown-illumos
         cargo build --target x86_64-unknown-illumos
     - name: Redox
+      if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
       run: |
         rustup target add x86_64-unknown-redox
         cargo check --target x86_64-unknown-redox
+    - name: HermitOS
+      if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
+      run: |
+        cargo -Zbuild-std check --target x86_64-unknown-hermit
+    - name: Check haiku
+      if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
+      run: cargo check -Z build-std --target x86_64-unknown-haiku
 
   wine:
     runs-on: ubuntu-22.04

Cargo.toml

@@ -21,8 +21,10 @@ rustdoc-args = ["--cfg", "docsrs"]
 cfg-if = "1"
 tracing = { version = "0.1.37", default-features = false }
 
-[target.'cfg(any(unix, target_os = "fuchsia", target_os = "vxworks"))'.dependencies]
-rustix = { version = "0.38.31", features = ["event", "fs", "pipe", "process", "std", "time"], default-features = false }
+[target.'cfg(any(unix, target_os = "fuchsia", target_os = "vxworks"))'.dependencies.rustix]
+version = "0.38.31"
+features = ["event", "fs", "pipe", "process", "std", "time"]
+default-features = false
 
 [target.'cfg(windows)'.dependencies]
 concurrent-queue = "2.2.0"
@@ -43,6 +45,9 @@ features = [
     "Win32_System_WindowsProgramming",
 ]
 
+[target.'cfg(target_os = "hermit")'.dependencies.hermit-abi]
+version = "0.3.9"
+
 [dev-dependencies]
 easy-parallel = "3.1.0"
 fastrand = "2.0.0"

README.md

@@ -12,11 +12,11 @@ https://docs.rs/polling)
 Portable interface to epoll, kqueue, event ports, and IOCP.
 
 Supported platforms:
-- [epoll](https://en.wikipedia.org/wiki/Epoll): Linux, Android
+- [epoll](https://en.wikipedia.org/wiki/Epoll): Linux, Android, RedoxOS
 - [kqueue](https://en.wikipedia.org/wiki/Kqueue): macOS, iOS, tvOS, watchOS, FreeBSD, NetBSD, OpenBSD,
   DragonFly BSD
 - [event ports](https://illumos.org/man/port_create): illumos, Solaris
-- [poll](https://en.wikipedia.org/wiki/Poll_(Unix)): VxWorks, Fuchsia, other Unix systems
+- [poll](https://en.wikipedia.org/wiki/Poll_(Unix)): VxWorks, Fuchsia, HermitOS, other Unix systems
 - [IOCP](https://learn.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports): Windows, Wine (version 7.13+)
 
 Polling is done in oneshot mode, which means interest in I/O events needs to be reset after

src/lib.rs

@@ -5,7 +5,7 @@
 //! - [kqueue](https://en.wikipedia.org/wiki/Kqueue): macOS, iOS, tvOS, watchOS, FreeBSD, NetBSD, OpenBSD,
 //!   DragonFly BSD
 //! - [event ports](https://illumos.org/man/port_create): illumos, Solaris
-//! - [poll](https://en.wikipedia.org/wiki/Poll_(Unix)): VxWorks, Fuchsia, other Unix systems
+//! - [poll](https://en.wikipedia.org/wiki/Poll_(Unix)): VxWorks, Fuchsia, HermitOS, other Unix systems
 //! - [IOCP](https://learn.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports): Windows, Wine (version 7.13+)
 //!
 //! By default, polling is done in oneshot mode, which means interest in I/O events needs to
@@ -107,6 +107,7 @@ cfg_if! {
         use kqueue as sys;
     } else if #[cfg(any(
         target_os = "vxworks",
+        target_os = "hermit",
         target_os = "fuchsia",
         target_os = "horizon",
         unix,
@@ -1017,8 +1018,11 @@ impl fmt::Debug for Poller {
 }
 
 cfg_if! {
-    if #[cfg(unix)] {
+    if #[cfg(any(unix, target_os = "hermit"))] {
+        #[cfg(unix)]
         use std::os::unix::io::{AsRawFd, RawFd, AsFd, BorrowedFd};
+        #[cfg(target_os = "hermit")]
+        use std::os::hermit::io::{AsRawFd, RawFd, AsFd, BorrowedFd};
 
         /// A resource with a raw file descriptor.
         pub trait AsRawSource {

src/poll.rs

@@ -6,8 +6,12 @@ use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Condvar, Mutex};
 use std::time::{Duration, Instant};
 
-use rustix::event::{poll, PollFd, PollFlags};
+#[cfg(not(target_os = "hermit"))]
 use rustix::fd::{AsFd, AsRawFd, BorrowedFd};
+#[cfg(target_os = "hermit")]
+use std::os::hermit::io::{AsFd, AsRawFd, BorrowedFd};
+
+use syscall::{poll, PollFd, PollFlags};
 
 // std::os::unix doesn't exist on Fuchsia
 type RawFd = std::os::raw::c_int;
@@ -443,7 +447,182 @@ fn cvt_mode_as_remove(mode: PollMode) -> io::Result<bool> {
     }
 }
 
-#[cfg(not(target_os = "espidf"))]
+#[cfg(unix)]
+mod syscall {
+    pub(super) use rustix::event::{poll, PollFd, PollFlags};
+
+    #[cfg(target_os = "espidf")]
+    pub(super) use rustix::event::{eventfd, EventfdFlags};
+    #[cfg(target_os = "espidf")]
+    pub(super) use rustix::fd::{AsFd, AsRawFd, BorrowedFd, OwnedFd, RawFd};
+    #[cfg(target_os = "espidf")]
+    pub(super) use rustix::io::{read, write};
+}
+
+#[cfg(target_os = "hermit")]
+mod syscall {
+    // TODO: Remove this shim once HermitOS is supported in Rustix.
+
+    use std::fmt;
+    use std::io;
+    use std::marker::PhantomData;
+    use std::ops::BitOr;
+
+    pub(super) use std::os::hermit::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, OwnedFd, RawFd};
+
+    /// Create an eventfd.
+    pub(super) fn eventfd(count: u64, _flags: EventfdFlags) -> io::Result<OwnedFd> {
+        let fd = unsafe { hermit_abi::eventfd(count, 0) };
+
+        if fd < 0 {
+            Err(io::Error::from_raw_os_error(unsafe {
+                hermit_abi::get_errno()
+            }))
+        } else {
+            Ok(unsafe { OwnedFd::from_raw_fd(fd) })
+        }
+    }
+
+    /// Read some bytes.
+    pub(super) fn read(fd: BorrowedFd<'_>, bytes: &mut [u8]) -> io::Result<usize> {
+        let count = unsafe { hermit_abi::read(fd.as_raw_fd(), bytes.as_mut_ptr(), bytes.len()) };
+
+        cvt(count)
+    }
+
+    /// Write some bytes.
+    pub(super) fn write(fd: BorrowedFd<'_>, bytes: &[u8]) -> io::Result<usize> {
+        let count = unsafe { hermit_abi::write(fd.as_raw_fd(), bytes.as_ptr(), bytes.len()) };
+
+        cvt(count)
+    }
+
+    /// Safe wrapper around the `poll` system call.
+    pub(super) fn poll(fds: &mut [PollFd<'_>], timeout: i32) -> io::Result<usize> {
+        let call = unsafe {
+            hermit_abi::poll(
+                fds.as_mut_ptr() as *mut hermit_abi::pollfd,
+                fds.len(),
+                timeout,
+            )
+        };
+
+        cvt(call as isize)
+    }
+
+    /// Safe wrapper around `pollfd`.
+    #[repr(transparent)]
+    pub(super) struct PollFd<'a> {
+        inner: hermit_abi::pollfd,
+        _lt: PhantomData<BorrowedFd<'a>>,
+    }
+
+    impl<'a> PollFd<'a> {
+        pub(super) fn from_borrowed_fd(fd: BorrowedFd<'a>, inflags: PollFlags) -> Self {
+            Self {
+                inner: hermit_abi::pollfd {
+                    fd: fd.as_raw_fd(),
+                    events: inflags.0,
+                    revents: 0,
+                },
+                _lt: PhantomData,
+            }
+        }
+
+        pub(super) fn revents(&self) -> PollFlags {
+            PollFlags(self.inner.revents)
+        }
+    }
+
+    impl AsFd for PollFd<'_> {
+        fn as_fd(&self) -> BorrowedFd<'_> {
+            unsafe { BorrowedFd::borrow_raw(self.inner.fd) }
+        }
+    }
+
+    impl fmt::Debug for PollFd<'_> {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            f.debug_struct("PollFd")
+                .field("fd", &format_args!("0x{:x}", self.inner.fd))
+                .field("events", &PollFlags(self.inner.events))
+                .field("revents", &PollFlags(self.inner.revents))
+                .finish()
+        }
+    }
+
+    /// Wrapper around polling flags.
+    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
+    pub(super) struct PollFlags(i16);
+
+    impl PollFlags {
+        /// Empty set of flags.
+        pub(super) const fn empty() -> Self {
+            Self(0)
+        }
+
+        pub(super) const IN: PollFlags = PollFlags(hermit_abi::POLLIN);
+        pub(super) const OUT: PollFlags = PollFlags(hermit_abi::POLLOUT);
+        pub(super) const WRBAND: PollFlags = PollFlags(hermit_abi::POLLWRBAND);
+        pub(super) const ERR: PollFlags = PollFlags(hermit_abi::POLLERR);
+        pub(super) const HUP: PollFlags = PollFlags(hermit_abi::POLLHUP);
+        pub(super) const PRI: PollFlags = PollFlags(hermit_abi::POLLPRI);
+
+        /// Tell if this contains some flags.
+        pub(super) fn contains(self, flags: PollFlags) -> bool {
+            self.0 & flags.0 != 0
+        }
+
+        /// Set a flag.
+        pub(super) fn set(&mut self, flags: PollFlags, set: bool) {
+            if set {
+                self.0 |= flags.0;
+            } else {
+                self.0 &= !(flags.0);
+            }
+        }
+
+        /// Tell if this is empty.
+        pub(super) fn is_empty(self) -> bool {
+            self.0 == 0
+        }
+
+        /// Tell if this intersects with some flags.
+        pub(super) fn intersects(self, flags: PollFlags) -> bool {
+            self.contains(flags)
+        }
+    }
+
+    impl BitOr for PollFlags {
+        type Output = PollFlags;
+
+        fn bitor(self, rhs: Self) -> Self::Output {
+            Self(self.0 | rhs.0)
+        }
+    }
+
+    #[derive(Debug, Copy, Clone)]
+    pub(super) struct EventfdFlags;
+
+    impl EventfdFlags {
+        pub(super) fn empty() -> Self {
+            Self
+        }
+    }
+
+    /// Convert a number to an actual result.
+    #[inline]
+    fn cvt(len: isize) -> io::Result<usize> {
+        if len < 0 {
+            Err(io::Error::from_raw_os_error(unsafe {
+                hermit_abi::get_errno()
+            }))
+        } else {
+            Ok(len as usize)
+        }
+    }
+}
+
+#[cfg(not(any(target_os = "espidf", target_os = "hermit")))]
 mod notify {
     use std::io;
 
@@ -534,16 +713,14 @@ mod notify {
     }
 }
 
-#[cfg(target_os = "espidf")]
+#[cfg(any(target_os = "espidf", target_os = "hermit"))]
 mod notify {
     use std::io;
     use std::mem;
 
-    use rustix::event::PollFlags;
-    use rustix::event::{eventfd, EventfdFlags};
-
-    use rustix::fd::{AsFd, AsRawFd, BorrowedFd, OwnedFd, RawFd};
-    use rustix::io::{read, write};
+    use super::syscall::{
+        eventfd, read, write, AsFd, AsRawFd, BorrowedFd, EventfdFlags, OwnedFd, PollFlags, RawFd,
+    };
 
     /// A notification pipe.
     ///
@@ -573,16 +750,16 @@ mod notify {
 
             let flags = EventfdFlags::empty();
             let event_fd = eventfd(0, flags).map_err(|err| {
-                match err {
-                    rustix::io::Errno::PERM => {
+                match io::Error::from(err) {
+                    err if err.kind() == io::ErrorKind::PermissionDenied => {
                         // EPERM can happen if the eventfd isn't initialized yet.
                         // Tell the user to call esp_vfs_eventfd_register.
                         io::Error::new(
                             io::ErrorKind::PermissionDenied,
                             "failed to initialize eventfd for polling, try calling `esp_vfs_eventfd_register`"
                         )
                     },
-                    err => io::Error::from(err),
+                    err => err,
                 }
             })?;
 
@@ -601,14 +778,14 @@ mod notify {
 
         /// Notifies the `Poller` instance via the eventfd file descriptor.
         pub(super) fn notify(&self) -> Result<(), io::Error> {
-            write(&self.event_fd, &1u64.to_ne_bytes())?;
+            write(self.event_fd.as_fd(), &1u64.to_ne_bytes())?;
 
             Ok(())
         }
 
         /// Pops a notification (if any) from the eventfd file descriptor.
         pub(super) fn pop_notification(&self) -> Result<(), io::Error> {
-            read(&self.event_fd, &mut [0; mem::size_of::<u64>()])?;
+            read(self.event_fd.as_fd(), &mut [0; mem::size_of::<u64>()])?;
 
             Ok(())
         }