Load unless there's a segfault

example.c

// gcc example.c try_load.c
#include "try_load.h"
  
#include <stdio.h>

void try_to_load(const uint8_t *address) {
    uint8_t value;
    if (try_load_u8(address, &value)) {
        printf("Successfully load from address %p: %d\n", address, value);
    } else {
        printf("Failed to load from address %p\n", address);
    }
}

int main() {
    uint8_t data[] = {0, 1, 2, 3};
    try_to_load((uint8_t*)0x123123);
    try_to_load(data);
}

try_load.c

/// Erika @rrika9 https://twitter.com/rrika9/status/1247491367686807552
/// it'd be nice if userspace had something like "load_or_branch_on_segfault"

#include "try_load.h"

#include <stdlib.h>
#include <unistd.h>

enum Pipes {READ, WRITE};

bool try_load_u8(const uint8_t *address, uint8_t *value) {
    int pipes[2];
    pipe(pipes);
    if (fork()) {
        close(pipes[WRITE]);
        ssize_t read_amount = read(pipes[READ], value, 1);
        if (read_amount <= 0) { return false; }
        close(pipes[READ]);
        return true;
    } else {
        close(pipes[READ]);
        write(pipes[WRITE], address, 1);
        close(pipes[WRITE]);
        exit(0);
    }
}

try_load.h

#pragma once
  
#include <stdint.h>
#include <stdbool.h>

/// Returns true on success, false on failure.
bool try_load_u8(const uint8_t *address, uint8_t *value);