Way to search for string occurence during the lifetime of the program

[dtomper]

Request

I'm loving this project so much. I'm curious about the possibility of finding a specific string value (or byte sequence in general) that might've occurred and got dropped at some point during the execution of the program. This would be a really helpful feature for debugging, especially in the context of reverse engineering.

Context

I made a dummy Rust code that has a get_user_input() function that prints "Type Something: " and waits for user input, and a main() function that calls get_user_input() inside an infinite loop as shown here:

use std::io::{self, Write};

fn get_user_input() {
    print!("Type something: ");
    std::io::stdout().flush().expect("Failed to flush");

    let mut input = String::new();

    io::stdin()
        .read_line(&mut input)
        .expect("Failed to read line");

    println!("{}", input);
}

fn main() {
    // Print function addresse at runtime
    let addr = get_user_input as *const ();
    println!("Input function location: {:p}", addr);

    loop {
        get_user_input();
    }
}

Rust automatically drops the input variable once the get_user_input() function goes out of scope. The string value itself stays in memory, I was able to verify that using PINCE (a Cheat Engine alternative in Linux). But AFAIU, rr doesn't keep track of unallocated memory because it's unnecessary to reproduce the deterministic outcome of the program. So, in order to find that string in the replay and do a bunch of crazy RE stuff like seeing where it originally came from, I would need to position myself in the right time frame.

[rocallahan]

rr doesn't keep track of unallocated memory because it's unnecessary to reproduce the deterministic outcome of the program

rr reproduces the exact memory and register states of the program, including "unallocated" memory. It's just memory.

gdb has a find command to search memory which works under rr.