rust-null

A userspace model of Linux /dev/null, on the way to a Rust-for-Linux /dev/rust-null device.

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Quick start

git clone https://github.com/bunnysi/rust-null.git
cd rust-null
cargo test
echo hello | cargo run --example discard

Rust 1.80 or newer. cargo test is the userspace contract; it does not load a kernel module.

Usage

NullDevice is the same three operations as drivers/char/mem.c:

use std::io::{Read, Write};
use rust_null::NullDevice;

let mut n = NullDevice::new();
assert_eq!(n.write(b"secret").unwrap(), 6); // discarded
let mut buf = [0xAAu8; 4];
assert_eq!(n.read(&mut buf).unwrap(), 0);   // EOF, buffer untouched

Call	Result
read	0 (EOF). The buffer is not filled.
write	count. Bytes are thrown away.
seek	0. Offset and whence are ignored.

That last row is the surprising one: lseek on /dev/null always returns 0, even for SEEK_END.

Roadmap

1. Userspace (this tree) — NullDevice + contract tests.
2. Rust for Linux — out-of-tree module against a CONFIG_RUST=y kernel.
3. /dev/rust-null — misc device with the same read/write/llseek contract.

License

GPL-2.0-only