feat(wasm): run a "hello world" wasm under an interpreter #58
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holy cow |
src/lib.rs
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| @@ -8,6 +8,10 @@ use hal_core::{boot::BootInfo, mem, Architecture}; | |||
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| use alloc::vec::Vec; | |||
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| mod wasm; | |||
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| const HELLOWORLD_WASM: &[u8] = include_bytes!("helloworld.wasm"); | |||
| mod wasm; | ||
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| const HELLOWORLD_WASM: &[u8] = include_bytes!("helloworld.wasm"); | ||
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| pub fn kernel_main<A>(bootinfo: &impl BootInfo<Arch = A>) -> ! |
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this clippy lint fires a lot of false positives on tracing macros, we should just turn it off
| // FIXME: These should both be `u16`, and probably generated from the wasi | ||
| // snapshot_0 `witx` definitions. |
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Oops, yeah. I fixed that. Should probably remove this comment.
| "unresolved global import" | ||
| ); | ||
| Err(wasmi::Error::Instantiation( | ||
| "unresolved global import".to_owned(), |
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there's no way for these error strings to be static strings, is there? I'm assuming the wasmi error type is not ours...
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Yup :-/. Every wasmi error has a string allocation.
if we decide to hard-fork wasmi and break the API, we could change the error type (and the lib in general) to be much less allocation-happy.
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| host_funcs! { | ||
| fn "wasi_unstable"::"fd_write"(fd: u32, iovs: u32, iovs_len: u32, nwritten: u32) -> u16 |
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TIOLI: seems like these could be idents rather than quoted?
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shrug probably.
I made them strings because I think theoretically wasm supports spaces in symbols. I'm not sure we'll ever declare a symbol which has spaces in it, though, so it's probably not reasonable.
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| } | ||
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| macro_rules! host_funcs { |
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am i correct that this macro is generating all the wasi host calls (eventually)? it would be nice to have a little more documentation of all the stuff this generates & how it should be invoked (eventually)
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Yeah. I threw together this macro because I needed to write a boatload of boilerplate to declare even a single host method, and didn't want to have to do it again.
We might actually want to use witx files and auto-generate the binding logic (similar to how wasmtime does since bytecodealliance/wasmtime#707), but this was much easier to get started with.
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| macro_rules! host_funcs { | ||
| ($( | ||
| fn $module:literal :: $name:literal ($($p:ident : $t:ident),*) $( -> $rt:ident)? |
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whoa, TIL that literal is an acceptable thing to match against in a macro!
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Yeah, it's super handy, especially because it has an open FOLLOW set, so you don't need to be as careful with what you put after it!
Been around since ~2016 sometime, but was stabilized in rust-lang/rust#56072.
| index: usize, | ||
| args: wasmi::RuntimeArgs, | ||
| ) -> Result<Option<wasmi::RuntimeValue>, wasmi::Trap> { | ||
| let span = tracing::trace_span!("invoke_index", index, ?args); |
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TIOLI: seems like we could just slap a #[tracing::instrument] on the generated function?
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This is the method which I was poking you on Discord about yesterday which breaks when annotated with #[tracing::instrument] due to rust messing up spans.
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ah gotcha. it would be nice to have a tracing issue for that (even though it's a compiler error), just so we can reference the related issue against the compiler?
| ;; | ||
| ;; wat2wasm helloworld.wast | ||
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| (module |
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could we wat2wasm when building the kernel? it seems super easy to accidentally end up with a binary wasm dep in the kernel that doesn't match some associated source
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That'd be pretty solid. We could also use a pure-rust wat2wasm converter (there are a few iirc) and just run it in our build script.
I just did it this way because it was the easiest, but not checking in binaries is probably a good plan.
This uses a fork of the
wasmicrate as the interpreter: https://github.com/mystor/wasmi/tree/mycelium.This fork has been modified to run under our custom target, removing implicit
stddependencies, and working around some missing soft-float intrinsics.