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wiggle: allow wiggle to use shared memory (#5054)

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`wiggle` looks for an exported `Memory` named `"memory"` to use for its
guest slices. This change allows it to use a `SharedMemory` if this is
the kind of memory used for the export.

It is `unsafe` to use shared memory in Wiggle because of broken Rust
guarantees: previously, Wiggle could hand out slices to WebAssembly
linear memory that could be concurrently modified by some other thread.
With the introduction of Wiggle's new `UnsafeGuestSlice` (#5225, #5229,
 #5264), Wiggle should now correctly communicate its guarantees through
its API.
This commit is contained in:
Andrew Brown
2022-11-15 11:04:42 -08:00
committed by GitHub
parent 9967782726
commit df1d679d2f
1 changed files with 11 additions and 5 deletions
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16
crates/wiggle/generate/src/wasmtime.rs
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@@ -112,13 +112,19 @@ fn generate_func(
};
let body = quote! {
let mem = match caller.get_export("memory") {
Some(#rt::wasmtime_crate::Extern::Memory(m)) => m,
let export = caller.get_export("memory");
let (mem, ctx) = match &export {
Some(#rt::wasmtime_crate::Extern::Memory(m)) => {
let (mem, ctx) = m.data_and_store_mut(&mut caller);
let ctx = get_cx(ctx);
(#rt::wasmtime::WasmtimeGuestMemory::new(mem), ctx)
}
Some(#rt::wasmtime_crate::Extern::SharedMemory(m)) => {
let ctx = get_cx(caller.data_mut());
(#rt::wasmtime::WasmtimeGuestMemory::shared(m.data()), ctx)
}
_ => #rt::anyhow::bail!("missing required memory export"),
};
let (mem , ctx) = mem.data_and_store_mut(&mut caller);
let ctx = get_cx(ctx);
let mem = #rt::wasmtime::WasmtimeGuestMemory::new(mem);
Ok(<#ret_ty>::from(#abi_func(ctx, &mem #(, #arg_names)*) #await_ ?))
};