feat(init): spawn service over IPC with per-client allowance refunded on child death; up to 4 death watchers; spawntest on test image

crates/libkos/src/spawn.rs

@@ -0,0 +1,53 @@
+//! Running a program through init (protocol: `types::spawn`). Init loads it
+//! and gives it a log endpoint; the caller hands it any other capabilities
+//! (`delegate` to the process) and starts it.
+
+use crate::syscall;
+use types::address::{EntryPoint, StackPointer};
+use types::bounded::CapSlot;
+use types::budget::Limits;
+use types::spawn::{STACK_TOP, reply, request};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SpawnError {
+    NotFound,
+    /// More than what is left of this process's spawn allowance.
+    OverAllowance,
+    Failed,
+}
+
+/// A loaded program, not yet running.
+pub struct Spawned {
+    pub process: CapSlot,
+    entry: EntryPoint,
+    log: Option<CapSlot>,
+}
+
+pub fn spawn(init: CapSlot, name: &[u8], limits: Limits) -> Result<Spawned, SpawnError> {
+    let words = request(name, limits).ok_or(SpawnError::Failed)?;
+    let reply = syscall::call(init, words, None).map_err(|_| SpawnError::Failed)?;
+    let [tag, entry, log, _] = reply.words();
+    let cap = match reply {
+        syscall::Received::Message { cap, .. } | syscall::Received::Call { cap, .. } => cap,
+        syscall::Received::Signal { .. } => None,
+    };
+    match (tag, cap) {
+        (reply::OK, Some(process)) => Ok(Spawned {
+            process,
+            entry: EntryPoint::from_raw(entry),
+            log: u8::try_from(log).ok().and_then(CapSlot::new),
+        }),
+        (reply::NOT_FOUND, _) => Err(SpawnError::NotFound),
+        (reply::OVER_ALLOWANCE, _) => Err(SpawnError::OverAllowance),
+        _ => Err(SpawnError::Failed),
+    }
+}
+
+impl Spawned {
+    /// Runs the program, telling it where its log endpoint is.
+    pub fn start(&self) -> bool {
+        let arg = types::start_arg::encode(None, self.log);
+        let stack = StackPointer::from_raw(STACK_TOP);
+        syscall::spawn_thread_in(self.process, self.entry, stack, arg) != usize::MAX
+    }
+}