110 lines
3.8 KiB
Rust
110 lines
3.8 KiB
Rust
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use swactor::actor::ActorAddress;
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use wasmtime::{Linker, Module, Store, TypedFunc};
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use crate::actor::{HostState, WasmActor};
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use crate::engine::SharedEngine;
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use crate::error::WasmActorError;
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/// Compiles a Wasm module and produces a ready-to-use [`WasmActor`].
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pub struct WasmActorBuilder {
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engine: SharedEngine,
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wasm_bytes: Vec<u8>,
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}
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impl WasmActorBuilder {
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pub fn new(engine: SharedEngine, wasm_bytes: impl Into<Vec<u8>>) -> Self {
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Self {
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engine,
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wasm_bytes: wasm_bytes.into(),
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}
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}
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/// Compile the module, link host functions, and instantiate.
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pub fn build(self) -> Result<WasmActor, WasmActorError> {
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let engine = self.engine.inner();
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let module = Module::new(engine, &self.wasm_bytes)?;
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let mut linker: Linker<HostState> = Linker::new(engine);
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Self::link_send(&mut linker)?;
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let mut store = Store::new(engine, HostState::default());
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let instance = linker.instantiate(&mut store, &module)?;
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// Extract required exports
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let memory = instance
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.get_memory(&mut store, "memory")
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.ok_or(WasmActorError::MissingExport("memory"))?;
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let alloc: TypedFunc<i32, i32> = instance
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.get_typed_func(&mut store, "alloc")
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.map_err(|_| WasmActorError::MissingExport("alloc"))?;
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let handle: TypedFunc<(i32, i32), ()> = instance
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.get_typed_func(&mut store, "handle")
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.map_err(|_| WasmActorError::MissingExport("handle"))?;
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Ok(WasmActor {
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store,
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memory,
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alloc,
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handle,
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})
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}
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/// Link the `swactor.send` host import.
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fn link_send(linker: &mut Linker<HostState>) -> Result<(), WasmActorError> {
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linker.func_wrap(
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"swactor",
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"send",
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|mut caller: wasmtime::Caller<'_, HostState>,
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dest_ptr: i32,
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payload_ptr: i32,
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payload_len: i32|
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-> Result<(), wasmtime::Error> {
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let mem = caller
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.get_export("memory")
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.and_then(|e| e.into_memory())
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.ok_or_else(|| wasmtime::Error::msg("guest must export memory"))?;
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let data = mem.data(&caller);
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let mem_len = data.len();
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// Validate non-negative arguments
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if dest_ptr < 0 || payload_ptr < 0 || payload_len < 0 {
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return Err(wasmtime::Error::msg(
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"negative argument in swactor.send",
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));
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}
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let dest_ptr = dest_ptr as usize;
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let payload_ptr = payload_ptr as usize;
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let payload_len = payload_len as usize;
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// Bounds-check with overflow protection
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let dest_end = dest_ptr
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.checked_add(32)
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.ok_or_else(|| wasmtime::Error::msg("dest_ptr overflow"))?;
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let payload_end = payload_ptr
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.checked_add(payload_len)
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.ok_or_else(|| wasmtime::Error::msg("payload range overflow"))?;
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if dest_end > mem_len || payload_end > mem_len {
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return Err(wasmtime::Error::msg(
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"out-of-bounds memory access in swactor.send",
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));
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}
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// Read 32-byte destination address
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let mut addr_bytes = [0u8; 32];
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addr_bytes.copy_from_slice(&data[dest_ptr..dest_end]);
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let dest = ActorAddress(addr_bytes);
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// Read payload
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let payload = data[payload_ptr..payload_end].to_vec();
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caller.data_mut().outbox.push((dest, payload));
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Ok(())
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},
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)?;
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Ok(())
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}
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}
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