Stuff

static void
handle_syscall_return(pid_t pid, struct traced_child *kid)
{
    int syscall;
    struct user_regs_struct u_in;

    ptrace(PTRACE_GETREGS, pid, 0, &u_in);
    syscall = u_in.orig_eax;
    if (syscall == 0xbadca11) {
        ptrace(PTRACE_POKEUSER, pid, 44, kid->orig_eax); //restore the syscall
        if( kid->ret < 0 )
            ptrace(PTRACE_POKEUSER, pid, 24, -13); //EACCES error
        else
            ptrace(PTRACE_POKEUSER, pid, 24, 0); //even if 0 is changed to -13, I still get same output!
    }

    ptrace(PTRACE_SYSCALL, pid, 0, 0);
}