feat(userspace): Call/ReplyRecv IPC, malformed-request replies, servers exit on dead endpoint; drop send/receive compat, select!, async_syscall

crates/apps/echo/src/main.rs

@@ -10,8 +10,9 @@ use libkos::syscall;
 extern "C" fn main() {
     let ep = CapSlot::const_new(0);
 
-    let (w0, w1, w2, w3) = syscall::receive(ep);
+    if let Ok(syscall::Received::Call { words: [w0, w1, w2, w3], .. }) = syscall::receive_msg(ep) {
-    syscall::send(ep, w0.wrapping_add(1), w1, w2, w3);
+        let _ = syscall::reply([w0.wrapping_add(1), w1, w2, w3], None);
+    }
 
     syscall::exit();
 }

crates/apps/snake/src/main.rs

@@ -18,9 +18,7 @@ const TICK_DELAY: u64 = 5_000_000;
 const MAX_RENDER_CMDS: usize = 140;
 
 fn display_send(req: &DisplayRequest) {
-    let words = req.encode();
+    let _ = syscall::request(DISPLAY_EP, req.encode());
-    syscall::send(DISPLAY_EP, words[0], words[1], words[2], words[3]);
-    syscall::receive(DISPLAY_EP);
 }
 
 fn draw_rect(x: u16, y: u16, w: u16, h: u16, color: u32) {
@@ -67,8 +65,9 @@ extern "C" fn main() {
 fn handle_input(snake: &mut Snake) {
     // Drain all pending events, apply the latest direction
     loop {
-        let _ = syscall::send(INPUT_EP, 0, 0, 0, 0);
+        let Ok([tag, kind, _, _]) = syscall::request(INPUT_EP, [0; 4]) else {
-        let (tag, kind, _, _) = syscall::receive(INPUT_EP);
+            break;
+        };
         if tag == 0 { break; } // NoEvent — queue drained
         if tag == 1 {
             match kind {

crates/bins/display-qemu/src/main.rs

@@ -14,25 +14,23 @@ extern "C" fn main() {
     } else {
         run_mock(ep);
     }
-
-    loop { libkos::syscall::yield_now(); }
 }
 
 #[inline(never)]
-fn run_virtio(mut fb: driver_framebuffer_virtio::VirtioFramebuffer, ep: CapSlot) {
+fn run_virtio(mut fb: driver_framebuffer_virtio::VirtioFramebuffer, ep: CapSlot) -> ! {
     use port_framebuffer::Framebuffer;
     fb.clear(types::display::Color::rgb(30, 30, 60));
     fb.flush();
     let mut srv = display_server::server::DisplayServer::new(fb);
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
 }
 
 #[inline(never)]
-fn run_mock(ep: CapSlot) {
+fn run_mock(ep: CapSlot) -> ! {
     let fb = driver_framebuffer_mock::MockFramebuffer::new(
         types::display::Dimension::new(640),
         types::display::Dimension::new(480),
     );
     let mut srv = display_server::server::DisplayServer::new(fb);
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
 }

crates/bins/input-qemu/src/main.rs

@@ -14,19 +14,17 @@ extern "C" fn main() {
     } else {
         run_uart(ep);
     }
-
-    loop { libkos::syscall::yield_now(); }
 }
 
 #[inline(never)]
-fn run_input(device: driver_input_virtio::VirtioInputDevice, ep: CapSlot) {
+fn run_input(device: driver_input_virtio::VirtioInputDevice, ep: CapSlot) -> ! {
     let mut srv = input_server::server::InputServer::new(device);
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
 }
 
 #[inline(never)]
-fn run_uart(ep: CapSlot) {
+fn run_uart(ep: CapSlot) -> ! {
     let device = driver_input_uart::UartInputDevice::new();
     let mut srv = input_server::server::InputServer::new(device);
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
 }

crates/init/src/lib.rs

@@ -24,9 +24,7 @@ fn request_file(shared_buf: *mut u8, filename: &[u8]) -> usize {
             core::ptr::write_volatile(shared_buf.add(i), b);
         }
     }
-    syscall::send(STORAGE_EP, CMD_READ_FILE, filename.len(), 0, 0);
+    syscall::request(STORAGE_EP, [CMD_READ_FILE, filename.len(), 0, 0]).map_or(0, |r| r[0])
-    let (file_size, _, _, _) = syscall::receive(STORAGE_EP);
-    file_size
 }
 
 struct LoadedProcess {
@@ -137,8 +135,11 @@ pub fn run(shared_buf_va: usize) -> ! {
 
     libkos::print!("init: loading snake... ");
     if let Some(snake) = load_binary(shared_buf, b"snake.elf") {
-        syscall::delegate(INPUT_EP, snake.process_cap, ipc_perms);
+        // A client only calls: Execute, never Read, so it cannot pose as
-        syscall::delegate(DISPLAY_EP, snake.process_cap, ipc_perms);
+        // the server and take other clients' requests.
+        let client = PermissionSet::empty().with(Permission::Execute);
+        syscall::delegate(INPUT_EP, snake.process_cap, client);
+        syscall::delegate(DISPLAY_EP, snake.process_cap, client);
         syscall::spawn_thread_in(snake.process_cap, snake.entry_point, USER_STACK_TOP);
         libkos::println!("ok");
     } else {

crates/libkos/src/display.rs

@@ -2,9 +2,10 @@ use crate::syscall;
 use types::bounded::CapSlot;
 use types::display::{Color, Dimension, ScreenCoord};
 
+/// A failed call reads as an error reply (tag `usize::MAX`).
 fn ipc(ep: CapSlot, w0: usize, w1: usize, w2: usize, w3: usize) -> (usize, usize, usize, usize) {
-    syscall::send(ep, w0, w1, w2, w3);
+    let r = syscall::request(ep, [w0, w1, w2, w3]).unwrap_or([usize::MAX, 0, 0, 0]);
-    syscall::receive(ep)
+    (r[0], r[1], r[2], r[3])
 }
 
 pub fn draw_rect(

crates/libkos/src/fs.rs

@@ -23,9 +23,10 @@ fn pack_path(path: &[u8]) -> (usize, usize) {
     (usize::from_le_bytes(w0), usize::from_le_bytes(w1))
 }
 
+/// A failed call reads as an error reply (tag `usize::MAX`).
 fn ipc(ep: CapSlot, w0: usize, w1: usize, w2: usize, w3: usize) -> (usize, usize, usize, usize) {
-    syscall::send(ep, w0, w1, w2, w3);
+    let r = syscall::request(ep, [w0, w1, w2, w3]).unwrap_or([usize::MAX, 0, 0, 0]);
-    syscall::receive(ep)
+    (r[0], r[1], r[2], r[3])
 }
 
 pub fn open(ep: CapSlot, path: &[u8]) -> Option<FileHandle> {

crates/libkos/src/input.rs

@@ -38,8 +38,7 @@ fn decode_key(kind: usize, extra: usize) -> Option<Key> {
 }
 
 pub fn poll_event(ep: CapSlot) -> Option<InputEvent> {
-    syscall::send(ep, 0, 0, 0, 0);
+    let [tag, kind, extra, _] = syscall::request(ep, [0; 4]).ok()?;
-    let (tag, kind, extra, _) = syscall::receive(ep);
     match tag {
         0 => None,
         1 => decode_key(kind, extra).map(InputEvent::KeyDown),

crates/libkos/src/syscall.rs

@@ -243,14 +243,6 @@ pub fn create_endpoint() -> Option<CapSlot> {
     slot_of(call0(SYS_CREATE_ENDPOINT)).ok()
 }
 
-/// Sends four words; returns 0 on success (kept for existing callers).
-pub fn send(endpoint: CapSlot, w0: usize, w1: usize, w2: usize, w3: usize) -> usize {
-    match send_msg(endpoint, [w0, w1, w2, w3], None) {
-        Ok(()) => 0,
-        Err(e) => e as usize,
-    }
-}
-
 pub fn send_msg(endpoint: CapSlot, words: [usize; 4], cap: Option<CapSlot>) -> Result<()> {
     raw(
         SYS_SEND,
@@ -259,12 +251,6 @@ pub fn send_msg(endpoint: CapSlot, words: [usize; 4], cap: Option<CapSlot>) -> R
     .map(|_| ())
 }
 
-/// Receives and returns just the words (kept for existing callers).
-pub fn receive(endpoint: CapSlot) -> (usize, usize, usize, usize) {
-    let w = receive_msg(endpoint).map_or([0; 4], |r| r.words());
-    (w[0], w[1], w[2], w[3])
-}
-
 pub fn receive_msg(endpoint: CapSlot) -> Result<Received> {
     raw(SYS_RECEIVE, [endpoint.value() as usize, 0, 0, 0, 0, 0]).and_then(Received::decode)
 }
@@ -278,6 +264,16 @@ pub fn call(endpoint: CapSlot, words: [usize; 4], cap: Option<CapSlot>) -> Resul
     .and_then(Received::decode)
 }
 
+/// Calls a server with four words and returns its reply's words. Needs
+/// only Execute on the endpoint; the reply comes back through the
+/// kernel's reply slot, so it can never reach another client.
+pub fn request(endpoint: CapSlot, words: [usize; 4]) -> Result<[usize; 4]> {
+    match call(endpoint, words, None)? {
+        Received::Signal { .. } => Err(Error::InvalidArgument),
+        reply => Ok(reply.words()),
+    }
+}
+
 /// Answers the last `Call` this thread received.
 pub fn reply(words: [usize; 4], cap: Option<CapSlot>) -> Result<()> {
     raw(SYS_REPLY, message_regs(0, words, cap)).map(|_| ())

crates/server-framework/src/async_syscall/mod.rs

@@ -1,16 +0,0 @@
-use types::bounded::CapSlot;
-
-pub async fn send(endpoint: CapSlot, w0: usize, w1: usize, w2: usize, w3: usize) -> usize {
-    libkos::syscall::send(endpoint, w0, w1, w2, w3)
-}
-
-pub async fn receive(endpoint: CapSlot) -> (usize, usize, usize, usize) {
-    libkos::syscall::receive(endpoint)
-}
-
-pub async fn wait_for_interrupt(_irq: CapSlot) {
-    libkos::syscall::yield_now();
-}
-
-pub async fn acknowledge_interrupt(_irq: CapSlot) {
-}

crates/server-framework/src/lib.rs

@@ -1,9 +1,7 @@
 #![no_std]
 
-pub mod async_syscall;
 pub mod codec;
 pub mod executor;
-pub mod select;
 pub mod server;
 
 pub use codec::{Decode, Encode};

crates/server-framework/src/select/mod.rs

@@ -1,14 +0,0 @@
-#[macro_export]
-macro_rules! select {
-    (
-        $msg:ident = receive($ep:expr) => $ipc_body:block
-        $irq:ident = wait_interrupt($irq_cap:expr) => $irq_body:block
-    ) => {
-        {
-            let sources = types::syscall_abi::SYS_WAIT_ANY;
-            let wake = libkos::syscall::receive($ep as usize);
-            let $msg = wake;
-            $ipc_body
-        }
-    };
-}

crates/server-framework/src/server/mod.rs

@@ -4,24 +4,52 @@ mod tests;
 use crate::codec::{Decode, Encode};
 use types::bounded::CapSlot;
 
+/// The reply to a request that does not decode. No protocol uses this
+/// tag, so every client decodes it as an error.
+pub const MALFORMED: usize = usize::MAX;
+
 pub trait Server {
     type Request: Decode;
     type Response: Encode;
 
     fn handle(&mut self, request: Self::Request) -> Self::Response;
 
-    fn run(&mut self, endpoint: CapSlot) {
+    /// Serves `endpoint` until receiving on it fails (it was destroyed or
+    /// the capability revoked), then returns why. Every `Call` gets a
+    /// reply, `[MALFORMED, ..]` if it does not decode; a one-way `Send` is
+    /// handled without one; notification signals are ignored.
+    fn run(&mut self, endpoint: CapSlot) -> libkos::syscall::Error {
+        use libkos::syscall::{Received, receive_msg, reply_recv};
+        let mut next = receive_msg(endpoint);
         loop {
-            let words = libkos::syscall::receive(endpoint);
+            let message = match next {
-            if let Some(request) = Self::Request::decode([words.0, words.1, words.2, words.3]) {
+                Ok(m) => m,
-                let response = self.handle(request);
+                Err(e) => return e,
-                let encoded = response.encode();
+            };
-                libkos::syscall::send(endpoint, encoded[0], encoded[1], encoded[2], encoded[3]);
+            next = match message {
+                Received::Call { words, .. } => {
+                    let reply = match Self::Request::decode(words) {
+                        Some(request) => self.handle(request).encode(),
+                        None => [MALFORMED, 0, 0, 0],
+                    };
+                    reply_recv(endpoint, reply, None)
                 }
+                Received::Message { words, .. } => {
+                    if let Some(request) = Self::Request::decode(words) {
+                        let _ = self.handle(request);
+                    }
+                    receive_msg(endpoint)
+                }
+                Received::Signal { .. } => receive_msg(endpoint),
+            };
         }
     }
 }
 
-pub fn serve<S: Server>(server: &mut S, endpoint: CapSlot) {
+/// Runs `server` on `endpoint` for good. A server whose endpoint is gone
-    server.run(endpoint);
+/// has nobody left to serve, so it says why and exits.
+pub fn serve<S: Server>(server: &mut S, endpoint: CapSlot) -> ! {
+    let error = server.run(endpoint);
+    libkos::println!("server: endpoint {} unusable ({:?}), exiting", endpoint.value(), error);
+    libkos::syscall::exit()
 }

crates/servers/input-server/src/lib.rs

@@ -17,6 +17,5 @@ pub fn run() -> ! {
 
     let mut srv = server::InputServer::new(device);
     let ep = types::bounded::CapSlot::new(0).unwrap();
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
-    loop { libkos::syscall::yield_now(); }
 }

crates/servers/log-server/src/lib.rs

@@ -10,6 +10,5 @@ mod tests;
 pub fn run() -> ! {
     let mut srv = server::LogServer::new();
     let ep = types::bounded::CapSlot::new(0).unwrap();
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
-    loop { libkos::syscall::yield_now(); }
 }

crates/servers/permission-manager/src/lib.rs

@@ -10,6 +10,5 @@ mod tests;
 pub fn run() -> ! {
     let mut srv = server::PermissionManager::new();
     let ep = types::bounded::CapSlot::new(0).unwrap();
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
-    loop { libkos::syscall::yield_now(); }
 }

crates/servers/session-server/src/lib.rs

@@ -12,6 +12,5 @@ pub fn run() -> ! {
     let mut srv = server::SessionServer::new(create_cap);
     srv.register_app("snake", "/apps/snake.elf");
     let ep = types::bounded::CapSlot::new(0).unwrap();
-    server_framework::serve(&mut srv, ep);
+    server_framework::serve(&mut srv, ep)
-    loop { libkos::syscall::yield_now(); }
 }

crates/servers/storage-server/src/lib.rs

@@ -36,10 +36,17 @@ pub fn run() -> ! {
 
     let ep = types::bounded::CapSlot::new(0).unwrap();
 
+    let mut next = syscall::receive_msg(ep);
     loop {
-        let (w0, w1, _w2, _w3) = syscall::receive(ep);
+        let message = match next {
-
+            Ok(m) => m,
-        match w0 {
+            Err(e) => {
+                libkos::println!("storage: endpoint unusable ({:?}), exiting", e);
+                syscall::exit();
+            }
+        };
+        let [w0, w1, _, _] = message.words();
+        let reply = match w0 {
             CMD_READ_FILE => {
                 let filename_len = w1;
                 let buf = shared_buf();
@@ -60,12 +67,14 @@ pub fn run() -> ! {
                     libkos::println!("NOT FOUND");
                 }
 
-                syscall::send(ep, file_size, 0, 0, 0);
+                [file_size, 0, 0, 0]
-            }
-            _ => {
-                syscall::send(ep, 0, 0, 0, 0);
-            }
             }
+            _ => [0, 0, 0, 0],
+        };
+        next = match message {
+            syscall::Received::Call { .. } => syscall::reply_recv(ep, reply, None),
+            _ => syscall::receive_msg(ep),
+        };
     }
 }