src/userprog/syscall.c


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#include "userprog/syscall.h"
#include <stdio.h>
#include <syscall-nr.h>
#include "threads/init.h"
#include "threads/interrupt.h"
#include "threads/thread.h"

static void syscall_handler (struct intr_frame *);

void
syscall_init (void) 
{
  intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
}

// cast to TYPE and deref argument N from f->esp
#define INTR_ESP(N, TYPE) *(TYPE *)(f->esp+(4*(N)))

static void
syscall_handler (struct intr_frame *f UNUSED) 
{
  int syscall_number = INTR_ESP(0, int);
  switch (syscall_number) {
    case 0:
      // halt
      power_off ();
      break;
    case 9:
      // printf
      printf ("printf: %s", INTR_ESP(2, char *));
      break;
    default:
      printf ("kernel: unknown syscall '%d'\n", syscall_number);
      break;
  }
  thread_exit ();
}