Call me Later !

call_me_later.c

#include <err.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

#define OFFSET_PARAM    0x2
#define OFFSET_ADDR     (OFFSET_PARAM + 8 + 2)

void *jit_this_call(void (*f)(), void *arg)
{
        char buf[] =
        {   
                0x48, 0xbf, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde,     // mov    $0xdeadbeefdeadbeef,%rdi
                0x49, 0xbb, 0xfe, 0xca, 0xfe, 0xca, 0xfe, 0xca, 0xfe, 0xca,     // mov    $0xcafecafecafecafe,%r11
                0x41, 0xff, 0xe3                                                // jmpq   *%r11
        };  

        char *addr = mmap(NULL, sizeof(buf), PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

        if (addr == MAP_FAILED) {
                err(EXIT_FAILURE, "lulz, ca a merde");
        }   

        memcpy(addr, buf, sizeof(buf));

        *(void**)(addr + OFFSET_PARAM) = arg;
        *(void**)(addr + OFFSET_ADDR) = (void*)f;

        mprotect(addr, sizeof(buf), PROT_EXEC);

        return addr;
}

static void byebye(int *lol)
{
        printf("bye : %p \n", lol);
}

static void on_int(int i)
{
        exit(EXIT_SUCCESS);
}

int main()
{
        printf("%d\n", getpid());

        void *wut_func = jit_this_call(byebye, (void *)0x42);

        atexit(wut_func);

        signal(SIGINT, on_int);

        for (;;)
                pause();

        return 0;
}