Can Redhook (or other project) hook into Rust code?

[vi]

If something is compiled with -C prefer-dynamic, can, for example, <std::fs::File as std::io::Write>::write be instrumented by LD_PRELOAD to inject failures?

[geofft]

Looks like the answer is yes, if you're willing to dig out the mangled name, and of course if the Rust compiler version is the same (since there's no stable ABI). If I cargo new --bin hello and cargo new p, edit p/Cargo.toml to make it a dylib and depend on libc, and then put the following in p/src/lib.rs:

#![allow(bad_style)]

extern crate libc;

use std::fmt::Arguments;
use std::mem::transmute;
use libc::{c_char, c_void};

#[link(name="dl")]
extern {
    fn dlsym(handle: *const c_void, symbol: *const c_char) -> *const c_void;
}

const RTLD_NEXT: *const c_void = -1isize as *const c_void;

#[no_mangle]
pub unsafe fn _ZN2io5stdio6_print20h47445faa595ef503E6gE(args: Arguments) {
    let ptr: unsafe extern fn(args: Arguments) =
        transmute(dlsym(RTLD_NEXT, b"_ZN2io5stdio6_print20h47445faa595ef503E6gE\0".as_ptr() as *const _));
    ptr(args);
    ptr(args);
}

then I can build both with -C prefer-dynamic as follows:

titan:~/src/rust/t/p geofft$ cargo rustc -- -C prefer-dynamic
   Compiling libc v0.2.9
   Compiling p v0.1.0 (file:///home/geofft/src/rust/t/p)
titan:~/src/rust/t/p geofft$ cd ../hello
titan:~/src/rust/t/hello geofft$ cargo rustc -- -C prefer-dynamic
   Compiling hello v0.1.0 (file:///home/geofft/src/rust/t/hello)
titan:~/src/rust/t/hello geofft$ LD_PRELOAD=../p/target/debug/libp.so target/debug/hello 
Hello, world!
Hello, world!

The difference with what redhook does already is that this is a pub unsafe fn, not a pub unsafe extern fn. I don't think there's a good way to programmatically derive the mangled name from the actual one, especially because the crate's name is not part of it and the crate's random ID is. If it's still useful for you with this restriction, I'm happy to add something to the syntax to let you drop the extern from redhook's generated code.

[vi]

I was just curious.

When Rust's stable ABI land and there be libstd in distros like today's libc, will Redhook extend its scope to also cover hooking into Rust?