alarm.txt

1.按之前的系统调用的操作步骤：int sigreturn(void);
int sigalarm(int,void*);。。。。等等
2.proc.h
struct proc {
  ......
  int interval;                // interval of alarm
  int since_interval;          // last call until now
  void (*handler)();           // function pointer
  int running_hand;            // flag of running
  struct trapframe trapframe_cp;  //copy of trapframe_cp
};
3.
sysproc.c
uint64
sys_sigreturn(void)
{
  struct proc *p = myproc();
  p->since_interval = 0;
  *(p->trapframe) = p->trapframe_cp;
  p->running_hand = 0;
  return 0;
}

uint64
sys_sigalarm(void)
{
  int interval;
  uint64 pointer;
  if(argint(0, &interval) < 0)
    return -1;
  if(interval == 0)
    return 0;
  if(argaddr(1, &pointer) < 0)
    return -1;
  myproc()->handler = (void *)pointer;
  myproc()->since_interval = 0;
  myproc()->running_hand = 0;
  myproc()->interval = interval;
  return 0;
}

proc.c
static struct proc*
allocproc(void)
{
  ....
found:
  p->pid = allocpid();
  p->interval = 0;
  p->since_interval = 0;
  p->handler = 0;
  ....
}


trap.c
void
usertrap(void)
{
  .......
  // give up the CPU if this is a timer interrupt.
  if(which_dev == 2)
  {
    if(p->interval != 0)
    {
      if(!p->running_hand)
        p->since_interval = p->since_interval + 1;
      if(!p->running_hand && p->since_interval == p->interval)
      {
        printf("alarm!\n");
        p->running_hand = 1;
        p->trapframe_cp = *(p->trapframe);
        p->trapframe->epc = (uint64)p->handler;
      }
    }
    yield();
  }
  ......
}