char/pipe: implement pipes

lib/vfs/Cargo.toml

@@ -13,6 +13,7 @@ kernel-util = { path = "../kernel-util" }
 ygg_driver_block = { path = "../../driver/block/core" }
 
 log = "0.4.20"
+futures-util = { version = "0.3.28", default-features = false, features = ["alloc", "async-await"] }
 
 [dev-dependencies]
 hosted-tests = { path = "../hosted-tests" }

lib/vfs/src/file/mod.rs

@@ -16,11 +16,13 @@ use crate::{
 use self::{
     device::{BlockFile, CharFile},
     directory::DirectoryFile,
+    pipe::PipeEnd,
     regular::RegularFile,
 };
 
 mod device;
 mod directory;
+mod pipe;
 mod regular;
 
 /// Per-file optional instance data created when a regular file is opened
@@ -45,9 +47,19 @@ pub enum File {
     Regular(RegularFile),
     Block(BlockFile),
     Char(CharFile),
+    AnonymousPipe(PipeEnd),
 }
 
 impl File {
+    /// Constructs a pipe pair, returning its `(read, write)` ends
+    pub fn new_pipe_pair(capacity: usize) -> (Arc<Self>, Arc<Self>) {
+        let (read, write) = PipeEnd::new_pair(capacity);
+        (
+            Arc::new(Self::AnonymousPipe(read)),
+            Arc::new(Self::AnonymousPipe(write)),
+        )
+    }
+
     pub(crate) fn directory(node: NodeRef, position: DirectoryOpenPosition) -> Arc<Self> {
         let position = IrqSafeSpinlock::new(position.into());
         Arc::new(Self::Directory(DirectoryFile { node, position }))
@@ -133,6 +145,7 @@ impl File {
             Self::Regular(file) => Some(&file.node),
             Self::Block(file) => Some(&file.node),
             Self::Char(file) => Some(&file.node),
+            Self::AnonymousPipe(_) => None,
         }
     }
 }
@@ -143,6 +156,7 @@ impl Read for File {
             Self::Regular(file) => file.read(buf),
             Self::Block(file) => file.read(buf),
             Self::Char(file) => file.read(buf),
+            Self::AnonymousPipe(pipe) => pipe.read(buf),
             Self::Directory(_) => Err(Error::IsADirectory),
         }
     }
@@ -154,6 +168,7 @@ impl Write for File {
             Self::Regular(file) => file.write(buf),
             Self::Block(file) => file.write(buf),
             Self::Char(file) => file.write(buf),
+            Self::AnonymousPipe(pipe) => pipe.write(buf),
             Self::Directory(_) => Err(Error::IsADirectory),
         }
     }
@@ -164,7 +179,7 @@ impl Seek for File {
         match self {
             Self::Regular(file) => Ok(*file.position.lock()),
             Self::Block(file) => Ok(*file.position.lock()),
-            Self::Char(_) => Err(Error::InvalidOperation),
+            Self::Char(_) | Self::AnonymousPipe(_) => Err(Error::InvalidOperation),
             Self::Directory(_) => Err(Error::IsADirectory),
         }
     }
@@ -173,7 +188,7 @@ impl Seek for File {
         match self {
             Self::Regular(file) => file.seek(from),
             Self::Block(file) => file.seek(from),
-            Self::Char(_) => Err(Error::InvalidOperation),
+            Self::Char(_) | Self::AnonymousPipe(_) => Err(Error::InvalidOperation),
             Self::Directory(_) => Err(Error::IsADirectory),
         }
     }
@@ -200,6 +215,7 @@ impl fmt::Debug for File {
                 .field("write", &file.write)
                 .finish_non_exhaustive(),
             Self::Directory(_) => f.debug_struct("DirectoryFile").finish_non_exhaustive(),
+            Self::AnonymousPipe(_) => f.debug_struct("AnonymousPipe").finish_non_exhaustive(),
         }
     }
 }
@@ -210,6 +226,7 @@ mod tests {
     use std::sync::{Arc, Mutex};
 
     use kernel_util::sync::IrqSafeSpinlock;
+    use ygg_driver_block::BlockDevice;
     use yggdrasil_abi::{
         error::Error,
         io::{DirectoryEntry, FileType, OpenOptions, SeekFrom},
@@ -217,7 +234,7 @@ mod tests {
     };
 
     use crate::{
-        device::{BlockDevice, CharDevice},
+        device::CharDevice,
         file::DirectoryOpenPosition,
         impls::const_value_node,
         node::{AccessToken, CommonImpl, DirectoryImpl, Node, NodeFlags, NodeRef, RegularImpl},

lib/vfs/src/file/pipe.rs

@@ -0,0 +1,226 @@
+use core::{
+    pin::Pin,
+    sync::atomic::{AtomicBool, Ordering},
+    task::{Context, Poll},
+};
+
+use alloc::{sync::Arc, vec, vec::Vec};
+use futures_util::{task::AtomicWaker, Future};
+use kernel_util::{block, sync::IrqSafeSpinlock};
+use yggdrasil_abi::error::Error;
+
+struct PipeInner {
+    data: Vec<u8>,
+    capacity: usize,
+    rd: usize,
+    wr: usize,
+}
+
+pub struct Pipe {
+    inner: IrqSafeSpinlock<PipeInner>,
+    shutdown: AtomicBool,
+    read_notify: AtomicWaker,
+    write_notify: AtomicWaker,
+}
+
+pub enum PipeEnd {
+    Read(Arc<Pipe>),
+    Write(Arc<Pipe>),
+}
+
+impl PipeInner {
+    pub fn new(capacity: usize) -> Self {
+        Self {
+            data: vec![0; capacity],
+            capacity,
+            rd: 0,
+            wr: 0,
+        }
+    }
+
+    pub fn can_write(&self) -> bool {
+        (self.wr + 1) % self.capacity != self.rd
+    }
+
+    pub fn can_read(&self) -> bool {
+        self.rd != self.wr
+    }
+
+    pub unsafe fn write(&mut self, val: u8) {
+        self.data[self.wr] = val;
+        self.wr = (self.wr + 1) % self.capacity;
+    }
+
+    pub unsafe fn read(&mut self) -> u8 {
+        let val = self.data[self.rd];
+        self.rd = (self.rd + 1) % self.capacity;
+        val
+    }
+
+    fn try_write(&mut self, val: u8) -> bool {
+        if self.can_write() {
+            unsafe {
+                self.write(val);
+            }
+            true
+        } else {
+            false
+        }
+    }
+
+    fn try_read(&mut self) -> Option<u8> {
+        if self.can_read() {
+            Some(unsafe { self.read() })
+        } else {
+            None
+        }
+    }
+}
+
+impl Pipe {
+    pub fn new(capacity: usize) -> Self {
+        Self {
+            inner: IrqSafeSpinlock::new(PipeInner::new(capacity)),
+            shutdown: AtomicBool::new(false),
+            read_notify: AtomicWaker::new(),
+            write_notify: AtomicWaker::new(),
+        }
+    }
+
+    pub fn shutdown(&self) {
+        self.shutdown.store(true, Ordering::Release);
+        self.read_notify.wake();
+        self.write_notify.wake();
+    }
+
+    pub fn blocking_write(&self, val: u8) -> impl Future<Output = Result<(), Error>> + '_ {
+        struct F<'a> {
+            pipe: &'a Pipe,
+            val: u8,
+        }
+
+        impl<'a> Future for F<'a> {
+            type Output = Result<(), Error>;
+
+            fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+                let mut lock = self.pipe.inner.lock();
+
+                // Try fast path before acquiring write notify to avoid unnecessary contention
+                if self.pipe.shutdown.load(Ordering::Acquire) {
+                    // TODO BrokenPipe
+                    return Poll::Ready(Err(Error::ReadOnly));
+                } else if lock.try_write(self.val) {
+                    self.pipe.read_notify.wake();
+                    return Poll::Ready(Ok(()));
+                }
+
+                self.pipe.write_notify.register(cx.waker());
+
+                if self.pipe.shutdown.load(Ordering::Acquire) {
+                    Poll::Ready(Err(Error::ReadOnly))
+                } else if lock.try_write(self.val) {
+                    self.pipe.read_notify.wake();
+                    Poll::Ready(Ok(()))
+                } else {
+                    Poll::Pending
+                }
+            }
+        }
+
+        F { pipe: self, val }
+    }
+
+    pub fn blocking_read(&self) -> impl Future<Output = Option<u8>> + '_ {
+        struct F<'a> {
+            pipe: &'a Pipe,
+        }
+
+        impl<'a> Future for F<'a> {
+            type Output = Option<u8>;
+
+            fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+                let mut lock = self.pipe.inner.lock();
+
+                if let Some(val) = lock.try_read() {
+                    self.pipe.write_notify.wake();
+                    return Poll::Ready(Some(val));
+                } else if self.pipe.shutdown.load(Ordering::Acquire) {
+                    return Poll::Ready(None);
+                }
+
+                self.pipe.read_notify.register(cx.waker());
+
+                if let Some(val) = lock.try_read() {
+                    Poll::Ready(Some(val))
+                } else if self.pipe.shutdown.load(Ordering::Acquire) {
+                    Poll::Ready(None)
+                } else {
+                    Poll::Pending
+                }
+            }
+        }
+
+        F { pipe: self }
+    }
+}
+
+impl PipeEnd {
+    pub fn new_pair(capacity: usize) -> (PipeEnd, PipeEnd) {
+        let pipe = Arc::new(Pipe::new(capacity));
+        let read = PipeEnd::Read(pipe.clone());
+        let write = PipeEnd::Write(pipe);
+
+        (read, write)
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> Result<usize, Error> {
+        let PipeEnd::Read(read) = self else {
+            return Err(Error::InvalidOperation);
+        };
+
+        block! {
+            let mut pos = 0;
+            let mut rem = buf.len();
+
+            while rem != 0 {
+                if let Some(val) = read.blocking_read().await {
+                    buf[pos] = val;
+                    pos += 1;
+                    rem -= 1;
+                } else {
+                    break;
+                }
+            }
+
+            Ok(pos)
+        }?
+    }
+
+    pub fn write(&self, buf: &[u8]) -> Result<usize, Error> {
+        let PipeEnd::Write(write) = self else {
+            return Err(Error::InvalidOperation);
+        };
+
+        block! {
+            let mut pos = 0;
+            let mut rem = buf.len();
+
+            while rem != 0 {
+                write.blocking_write(buf[pos]).await?;
+                pos += 1;
+                rem -= 1;
+            }
+
+            Ok(pos)
+        }?
+    }
+}
+
+impl Drop for PipeEnd {
+    fn drop(&mut self) {
+        match self {
+            Self::Read(read) => read.shutdown(),
+            Self::Write(write) => write.shutdown(),
+        }
+    }
+}

src/proc/io.rs

@@ -62,12 +62,20 @@ impl ProcessIo {
     /// Removes and closes a [FileRef] from the struct
     pub fn close_file(&mut self, fd: RawFd) -> Result<(), Error> {
         // Do nothing, file will be dropped and closed
-        self.files.remove(&fd).ok_or(Error::InvalidFile)?;
-        Ok(())
+        if self.files.remove(&fd).is_some() {
+            Ok(())
+        } else {
+            Err(Error::InvalidFile)
+        }
     }
 
     /// Removes all [FileRef]s from the struct which do not pass the `predicate` check
     pub fn retain<F: Fn(&RawFd, &mut FileRef) -> bool>(&mut self, predicate: F) {
         self.files.retain(predicate);
     }
+
+    /// Handles process exit by closing all of its files
+    pub fn handle_exit(&mut self) {
+        self.files.clear();
+    }
 }

src/syscall/mod.rs

@@ -9,7 +9,7 @@ use abi::{
 };
 use alloc::sync::Arc;
 use kernel_util::{block, runtime, sync::IrqSafeSpinlockGuard};
-use vfs::{IoContext, NodeRef, Read, Seek, Write};
+use vfs::{File, IoContext, NodeRef, Read, Seek, Write};
 use yggdrasil_abi::{error::SyscallResult, io::MountOptions};
 
 use crate::{
@@ -188,7 +188,17 @@ fn syscall_handler(func: SyscallFunction, args: &[u64]) -> Result<usize, Error>
             let fd = RawFd(args[0] as u32);
 
             run_with_io(process, |mut io| {
-                io.close_file(fd)?;
+                let res = io.close_file(fd);
+
+                match res {
+                    Err(Error::InvalidFile) => {
+                        warnln!("Double close of fd {:?} in process {}", fd, process.id());
+                    }
+                    _ => (),
+                }
+
+                res?;
+
                 Ok(0)
             })
         }
@@ -262,6 +272,24 @@ fn syscall_handler(func: SyscallFunction, args: &[u64]) -> Result<usize, Error>
         SyscallFunction::RemoveDirectory => {
             todo!()
         }
+        SyscallFunction::CreatePipe => {
+            let ends: &mut [MaybeUninit<RawFd>; 2] = arg_user_mut(args[0] as usize)?;
+
+            run_with_io(process, |mut io| {
+                let (read, write) = File::new_pipe_pair(256);
+
+                let read_fd = io.place_file(read)?;
+                let write_fd = io.place_file(write)?;
+
+                infoln!("Read end: {:?}", read_fd);
+                infoln!("Write end: {:?}", write_fd);
+
+                ends[0].write(read_fd);
+                ends[1].write(write_fd);
+
+                Ok(0)
+            })
+        }
         // Process management
         SyscallFunction::SpawnProcess => {
             let options = arg_user_ref::<SpawnOptions>(args[0] as usize)?;

src/task/process.rs

@@ -346,7 +346,7 @@ impl Process {
             inner.state = ProcessState::Terminated(code);
 
             // XXX
-            // self.io.lock().handle_exit();
+            self.io.lock().handle_exit();
 
             drop(inner);