Files

Andrew Brown f85e3f8517 wasi: avoid buffer underflow with shared memory (#5543 )

* wasi: avoid buffer underflow with shared memory

This change fixes an issue identified when using wasi-threads to perform
file reads. In order to maintain Rust safety guarantees in the presence
of WebAssembly shared memory, which can be modified concurrently by any
of the running threads, the WASI implementations of `fd_read` and
`fd_pread` were given special code paths when shared memory is detected:
in these cases, the data is first read into a host-limited buffer and
then subsequently copied into linear memory. The problem was that the
rather-complex logic for doing this "buffer then copy" idea for multiple
IO vectors could fail due to buffer underflow. If, e.g., a read was
limited by the host to 64K (or even if the read returned less than the
total buffer size) the `UnsafeGuestSlice::copy_from_slice` logic would
fail, complaining that the sizes of both buffers were unequal.

This change both simplifies and fixes the logic:
- only the first IO vector is filled; this could represent a performance
  penalty for threaded programs, but the "buffer then copy" idea already
  imposes a non-trivial overhead. This simplifies the logic, allowing us
  to...
- resize the shared memory buffer to the exact number of bytes read

* review: early return when no IO vectors passed to shared memory

* fix: add empty RoFlags on early exit

2023-01-09 19:28:09 +00:00

cap-std-sync

Use workspace inheritance for some more dependencies (#5349 )

2022-11-29 22:32:56 +00:00

src

wasi: avoid buffer underflow with shared memory (#5543 )

2023-01-09 19:28:09 +00:00

tokio

Use workspace inheritance for some more dependencies (#5349 )

2022-11-29 22:32:56 +00:00

WASI @ 0ba0c5e2e3

Implement sock_accept

2022-01-31 16:25:11 -08:00

build.rs

Add "cargo:rerun-if-changed=build.rs" to some build.rs files.

2021-09-16 11:52:21 -07:00

Cargo.toml

Use workspace inheritance for some more dependencies (#5349 )

2022-11-29 22:32:56 +00:00

LICENSE

Initial reorg.

2019-11-08 06:35:40 -08:00

README.md

Implement the remaining socket-related WASI functions. (#4776 )

2022-08-26 11:39:51 -07:00

README.md

`wasi-common`

A Bytecode Alliance project

A library providing a common implementation of WASI hostcalls for re-use in any WASI-enabled runtime.

The wasi-common crate will ultimately serve as a library providing a common implementation of WASI hostcalls for re-use in any WASI (and potentially non-WASI) runtimes such as Wasmtime and Lucet.

The library is an adaption of lucet-wasi crate from the Lucet project, and it is currently based on 40ae1df git revision.

Please note that the library requires Rust compiler version at least 1.37.0.

Supported syscalls

*nix

In our *nix implementation, we currently support the entire WASI API with the exception of the proc_raise hostcall, as it is expected to be dropped entirely from WASI.

Windows

In our Windows implementation, we currently support the minimal subset of WASI API which allows for running the very basic "Hello world!" style WASM apps. More coming shortly, so stay tuned!

Development hints

When testing the crate, you may want to enable and run full wasm32 integration testsuite. This requires wasm32-wasi target installed which can be done as follows using rustup

rustup target add wasm32-wasi

Now, you should be able to run the integration testsuite by running cargo test on the test-programs package with test-programs/test_programs feature enabled:

cargo test --features test-programs/test_programs --package test-programs