Auto merge of #3444 - RalfJung:linux-epoll-eventfd-cleanup, r=RalfJung

shims/linux: move epoll and eventfd into their own respective files

Also put the FD types into those files; they can then even be made private there.

Author: bors

src/tools/miri/src/shims/unix/fd.rs

@@ -52,6 +52,8 @@ pub trait FileDescriptor: std::fmt::Debug + Any {
     fn dup(&mut self) -> io::Result<Box<dyn FileDescriptor>>;
 
     fn is_tty(&self, _communicate_allowed: bool) -> bool {
+        // Most FDs are not tty's and the consequence of a wrong `false` are minor,
+        // so we use a default impl here.
         false
     }
 }

src/tools/miri/src/shims/unix/linux/fd.rs renamed to src/tools/miri/src/shims/unix/linux/epoll.rs

@@ -1,12 +1,50 @@
-use std::cell::Cell;
+use std::io;
+
+use rustc_data_structures::fx::FxHashMap;
 
 use crate::shims::unix::*;
 use crate::*;
-use epoll::{Epoll, EpollEvent};
-use event::Event;
 
-pub mod epoll;
-pub mod event;
+/// An `Epoll` file descriptor connects file handles and epoll events
+#[derive(Clone, Debug, Default)]
+struct Epoll {
+    /// The file descriptors we are watching, and what we are watching for.
+    file_descriptors: FxHashMap<i32, EpollEvent>,
+}
+
+/// Epoll Events associate events with data.
+/// These fields are currently unused by miri.
+/// This matches the `epoll_event` struct defined
+/// by the epoll_ctl man page. For more information
+/// see the man page:
+///
+/// <https://man7.org/linux/man-pages/man2/epoll_ctl.2.html>
+#[derive(Clone, Debug)]
+struct EpollEvent {
+    #[allow(dead_code)]
+    events: u32,
+    /// `Scalar<Provenance>` is used to represent the
+    /// `epoll_data` type union.
+    #[allow(dead_code)]
+    data: Scalar<Provenance>,
+}
+
+impl FileDescriptor for Epoll {
+    fn name(&self) -> &'static str {
+        "epoll"
+    }
+
+    fn dup(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
+        Ok(Box::new(self.clone()))
+    }
+
+    fn close<'tcx>(
+        self: Box<Self>,
+        _communicate_allowed: bool,
+    ) -> InterpResult<'tcx, io::Result<i32>> {
+        Ok(Ok(0))
+    }
+}
 
 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
@@ -156,49 +194,4 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             Ok(Scalar::from_i32(this.fd_not_found()?))
         }
     }
-
-    /// This function creates an `Event` that is used as an event wait/notify mechanism by
-    /// user-space applications, and by the kernel to notify user-space applications of events.
-    /// The `Event` contains an `u64` counter maintained by the kernel. The counter is initialized
-    /// with the value specified in the `initval` argument.
-    ///
-    /// A new file descriptor referring to the `Event` is returned. The `read`, `write`, `poll`,
-    /// `select`, and `close` operations can be performed on the file descriptor. For more
-    /// information on these operations, see the man page linked below.
-    ///
-    /// The `flags` are not currently implemented for eventfd.
-    /// The `flags` may be bitwise ORed to change the behavior of `eventfd`:
-    /// `EFD_CLOEXEC` - Set the close-on-exec (`FD_CLOEXEC`) flag on the new file descriptor.
-    /// `EFD_NONBLOCK` - Set the `O_NONBLOCK` file status flag on the new open file description.
-    /// `EFD_SEMAPHORE` - miri does not support semaphore-like semantics.
-    ///
-    /// <https://linux.die.net/man/2/eventfd>
-    #[expect(clippy::needless_if)]
-    fn eventfd(
-        &mut self,
-        val: &OpTy<'tcx, Provenance>,
-        flags: &OpTy<'tcx, Provenance>,
-    ) -> InterpResult<'tcx, Scalar<Provenance>> {
-        let this = self.eval_context_mut();
-
-        let val = this.read_scalar(val)?.to_u32()?;
-        let flags = this.read_scalar(flags)?.to_i32()?;
-
-        let efd_cloexec = this.eval_libc_i32("EFD_CLOEXEC");
-        let efd_nonblock = this.eval_libc_i32("EFD_NONBLOCK");
-        let efd_semaphore = this.eval_libc_i32("EFD_SEMAPHORE");
-
-        if flags & (efd_cloexec | efd_nonblock | efd_semaphore) == 0 {
-            throw_unsup_format!("{flags} is unsupported");
-        }
-        // FIXME handle the cloexec and nonblock flags
-        if flags & efd_cloexec == efd_cloexec {}
-        if flags & efd_nonblock == efd_nonblock {}
-        if flags & efd_semaphore == efd_semaphore {
-            throw_unsup_format!("EFD_SEMAPHORE is unsupported");
-        }
-
-        let fd = this.machine.fds.insert_fd(Box::new(Event { val: Cell::new(val.into()) }));
-        Ok(Scalar::from_i32(fd))
-    }
 }

src/tools/miri/src/shims/unix/linux/fd/event.rs renamed to src/tools/miri/src/shims/unix/linux/eventfd.rs

@@ -1,11 +1,13 @@
-use crate::shims::unix::FileDescriptor;
+//! Linux `eventfd` implementation.
+//! Currently just a stub.
+use std::cell::Cell;
+use std::io;
 
-use rustc_const_eval::interpret::InterpResult;
 use rustc_middle::ty::TyCtxt;
 use rustc_target::abi::Endian;
 
-use std::cell::Cell;
-use std::io;
+use crate::shims::unix::*;
+use crate::*;
 
 /// A kind of file descriptor created by `eventfd`.
 /// The `Event` type isn't currently written to by `eventfd`.
@@ -15,10 +17,10 @@ use std::io;
 ///
 /// <https://man.netbsd.org/eventfd.2>
 #[derive(Debug)]
-pub struct Event {
+struct Event {
     /// The object contains an unsigned 64-bit integer (uint64_t) counter that is maintained by the
     /// kernel. This counter is initialized with the value specified in the argument initval.
-    pub val: Cell<u64>,
+    val: Cell<u64>,
 }
 
 impl FileDescriptor for Event {
@@ -70,3 +72,51 @@ impl FileDescriptor for Event {
         Ok(Ok(8))
     }
 }
+
+impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
+pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
+    /// This function creates an `Event` that is used as an event wait/notify mechanism by
+    /// user-space applications, and by the kernel to notify user-space applications of events.
+    /// The `Event` contains an `u64` counter maintained by the kernel. The counter is initialized
+    /// with the value specified in the `initval` argument.
+    ///
+    /// A new file descriptor referring to the `Event` is returned. The `read`, `write`, `poll`,
+    /// `select`, and `close` operations can be performed on the file descriptor. For more
+    /// information on these operations, see the man page linked below.
+    ///
+    /// The `flags` are not currently implemented for eventfd.
+    /// The `flags` may be bitwise ORed to change the behavior of `eventfd`:
+    /// `EFD_CLOEXEC` - Set the close-on-exec (`FD_CLOEXEC`) flag on the new file descriptor.
+    /// `EFD_NONBLOCK` - Set the `O_NONBLOCK` file status flag on the new open file description.
+    /// `EFD_SEMAPHORE` - miri does not support semaphore-like semantics.
+    ///
+    /// <https://linux.die.net/man/2/eventfd>
+    #[expect(clippy::needless_if)]
+    fn eventfd(
+        &mut self,
+        val: &OpTy<'tcx, Provenance>,
+        flags: &OpTy<'tcx, Provenance>,
+    ) -> InterpResult<'tcx, Scalar<Provenance>> {
+        let this = self.eval_context_mut();
+
+        let val = this.read_scalar(val)?.to_u32()?;
+        let flags = this.read_scalar(flags)?.to_i32()?;
+
+        let efd_cloexec = this.eval_libc_i32("EFD_CLOEXEC");
+        let efd_nonblock = this.eval_libc_i32("EFD_NONBLOCK");
+        let efd_semaphore = this.eval_libc_i32("EFD_SEMAPHORE");
+
+        if flags & (efd_cloexec | efd_nonblock | efd_semaphore) == 0 {
+            throw_unsup_format!("{flags} is unsupported");
+        }
+        // FIXME handle the cloexec and nonblock flags
+        if flags & efd_cloexec == efd_cloexec {}
+        if flags & efd_nonblock == efd_nonblock {}
+        if flags & efd_semaphore == efd_semaphore {
+            throw_unsup_format!("EFD_SEMAPHORE is unsupported");
+        }
+
+        let fd = this.machine.fds.insert_fd(Box::new(Event { val: Cell::new(val.into()) }));
+        Ok(Scalar::from_i32(fd))
+    }
+}

src/tools/miri/src/shims/unix/linux/fd/epoll.rs

@@ -6,7 +6,8 @@ use crate::machine::SIGRTMIN;
 use crate::shims::unix::*;
 use crate::*;
 use shims::foreign_items::EmulateForeignItemResult;
-use shims::unix::linux::fd::EvalContextExt as _;
+use shims::unix::linux::epoll::EvalContextExt as _;
+use shims::unix::linux::eventfd::EvalContextExt as _;
 use shims::unix::linux::mem::EvalContextExt as _;
 use shims::unix::linux::sync::futex;
 

src/tools/miri/src/shims/unix/linux/foreign_items.rs

@@ -1,4 +1,5 @@
-pub mod fd;
+pub mod epoll;
+pub mod eventfd;
 pub mod foreign_items;
 pub mod mem;
 pub mod sync;

src/tools/miri/src/shims/unix/linux/mod.rs

@@ -6,7 +6,6 @@ use crate::*;
 /// Pair of connected sockets.
 ///
 /// We currently don't allow sending any data through this pair, so this can be just a dummy.
-/// FIXME: show proper errors when trying to send/receive
 #[derive(Debug)]
 struct SocketPair;