maxCodeVector/OS_project_2

OSProject2 User Programe

member: chengmin, huang Yu'an

Before start:

1. change --qumu to --bocus,

2. process_wait() and system call write need to implement first, unless nothing output. (can use semaphore), now its busy waitting. It needs more smart implement later especially for syscall wait().

3. Can change compile optimized model to O0 for more convenient debug.

Start:

Need to write system call hander for each system call.

must use argument -v -k -t 60

• halt: implement HALT

• exit: implement Exit

• sc-bad-sp: check f->esp's value, but I can not recognize this type of bad address.

• sc-bad-arg: check f->esp's value if is valid.

• exec-bound-2: check esp's value, but I can not kown whether this address is bad!!

• exec-bound-3: see exec-bound-2.

Write a syscall

when wiite the callback function for syscall, we need to add its implement (as well as resister) in syscall_init which is in userprog/syscall.c (most of code we need to write in this project is in this file).

void
syscall_init (void) 
{
  intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
  int i;
  for(i=0;i<MAXCALL;i++){
    pfn[i] = NULL;
  }
  pfn[SYS_WRITE] = IWrite;
  pfn[SYS_EXIT] = IExit;
  pfn[SYS_HALT] = IHALT;
  pfn[SYS_EXEC] = IEXEC;
  pfn[SYS_WAIT] = IWAIT;
}

This function call current thread to exit will status as exit code. I add a atrribute rtv: int in struct thread as its return value.

void ExitStatus(int status){
  struct  thread* cur = thread_current();
  cur -> rtv = status;
  thread_exit();
}

The syscall parameter arguments was stored in f->esp. The order and type of them can be seen in lib/user/syscall.c. The return value of syscall was put in f->eax.

void IExit(struct intr_frame * f)
{
  int *esp = (int*)f->esp;
  if(!is_user_vaddr(esp+1))
    ExitStatus(-1);
  else{
    int rtv = *(esp+1);
    ExitStatus(rtv);
  }
}