Question: how are the WASI API pointer parameters boundary checked and converted to native address

[Kevin0626]

Hi, according to my understanding about the WASM spec, the two steps in the subject must be executed during the runtime serving a WASI call. I traced it down to https://github.com/CraneStation/wasmtime/blob/master/wasmtime-wasi/src/syscalls.rs and got lost. I have no knowledge about Rust programming yet, so I want to ask for any quick answer. Probably I should plan some time for learning Rust.. thanks..

[kubkon]

Hey! Yeah, learning some Rust might be a good idea since we're striving to have wasmtime as well as the syscalls lib written purely in Rust. Anyhow, the crate you've arrived at used to be a wrapper around C implementation of the syscalls (now renamed to wasmtime-wasi-c), and now it's a wrapper around a Rust implementation in the form of a wasi-common library.

In terms of decoding pointers and general memory management, the module you are looking for can be found here memory.rs. It might be useful to actually grab a copy of wasmtime, compile it and run some example Wasm with trace logging on:

RUST_LOG=wasi_common=trace wasmtime -d some_binary.wasm

You should get output similar to that found here. Hope that helps! :-)

[Kevin0626]

Thank you for the guides @kubkon