lind overlay for the Rust libc crate

[rishabhBudhouliya]

Summary

Rust programs built for lind use the wasm32-wasip1 target. The Rust libc crate picks its wasi module for that target, which describes wasi-libc. However, lind links the binary against lind-glibc. Struct layouts, open flags and errno values don't match causing syscall failures.

Some observed behavior when trying to run in-toto in lind-wasm:

• metadata(): len=34359742464, is_file=false (st_size read from the wrong offset)
• read_dir(): four entries with empty names (d_name read from the wrong offset)
• File::create(): "os error 2" (wasi O_CREAT bit passed to a Linux open)

I was wondering why grates never have this problem and it turns out they do file I/O through raw 3i calls. The imfs grate has a workaround comment for the same bug. Would be interesting to hear more about how the grates designed around this issue.

Related issues

Testing

scripts/rust/make_lind_libc.sh copies libc 0.2.189 from the cargo registry into build/lind-libc and applies scripts/rust/lind-libc-wasi.patch. The patch changes one file, src/wasi/mod.rs: the stat and dirent layouts as measured under lind.

A crate uses it with: cargo --config 'patch.crates-io.libc.path="build/lind-libc"'

Compatibility and security impact

Checklist

• I have read the contribution guidelines.
• I added or updated tests where appropriate.
• I ran the relevant tests locally and they pass.
• I formatted the code and ran the relevant linters.
• I updated documentation for user-visible or architectural changes.
• I disclosed security vulnerabilities privately rather than in this PR.

[Yaxuan-w]

Seems this file is a git diff result? What's the purpose of this file?