static void
command_regs(struct mi_process proc)
{
    struct mi_registers regs = get_process_registers(proc);
    printf("rax = %#018lx rcx = %#018lx\n"
           "rbp = %#018lx rbx = %#018lx\n"
           "rdx = %#018lx rsi = %#018lx\n"
           "rdi = %#018lx rip = %#018lx\n"
           "rsp = %#018lx\n", 
           regs.rax, regs.rcx, regs.rbp, regs.rbx, 
           regs.rdx, regs.rsi, regs.rdi, regs.rip, 
           regs.rsp);
}

static void
command_step(struct mi_process proc)
{
    ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
    waitpid(proc.pid, 0, 0);
    
#if 1
    print_current_instruction(proc);
    struct mi_registers regs = get_process_registers(proc);
    struct mi_sourcepoint *sp = pc_to_sourcepoint(proc, regs.rip - proc.base_address);
    print_current_line(proc, sp->line);
#endif
}

static void
command_start(struct mi_process proc)
{
    u64 main_address = proc.base_address + proc.main_address;
    
    long saved_instruction = ptrace(PTRACE_PEEKDATA, proc.pid, main_address, NULL);
    long int3_byte = 0x000000cc;
    long int3_word = (saved_instruction & 0xFFFFFF00) | int3_byte;
    
    /* write 0xcc */
    ptrace(PTRACE_POKEDATA, proc.pid, main_address, int3_word);
    
    /* wait till child hits the interrupt */
    ptrace(PTRACE_CONT, proc.pid, 0, 0);
    waitpid(proc.pid, 0, 0);
    
    /* restore original instrucion */
    ptrace(PTRACE_POKEDATA, proc.pid, main_address, saved_instruction);
    
    /* step back to original instruction */
    struct mi_registers regs = get_process_registers(proc);
    regs.rip -= 1;
    set_process_registers(proc, regs);
}

static void
command_next(struct mi_process proc)
{
    struct mi_registers regs = get_process_registers(proc);
    
    struct mi_sourcepoint *sp = pc_to_sourcepoint(proc, regs.rip - proc.base_address);
    struct mi_sourcepoint *next_sp;
    
    do {
        ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
        waitpid(proc.pid, 0, 0);
        regs = get_process_registers(proc);
        //printf("%#lx\n", regs.rip - proc.base_address);
        next_sp = pc_to_sourcepoint(proc, regs.rip - proc.base_address);
        // TODO: skip call, repXXX, etc
    } while (next_sp->line == sp->line);
    
    print_current_line(proc, next_sp->line);
}

static void
command_list(struct mi_process proc)
{
    struct mi_registers regs = get_process_registers(proc);
    struct mi_sourcepoint *sp = pc_to_sourcepoint(proc, regs.rip - proc.base_address);
    print_current_line(proc, sp->line);
}

static void
command_cont(struct mi_process proc)
{
    ptrace(PTRACE_CONT, proc.pid, 0, 0);
    // TODO
}

static void
command_stop(struct mi_process proc)
{
    kill(proc.pid, SIGINT);
    // TODO
}