???????user_mode(regs)????1?????????????(?м??????o??????????????)get_signal_to_deliver()????????????????????????(????Private Signal Queue??Shared Signal Queue)??????????????(????dequeue_signal()????)????????????λ???????signal_struct?????????????????sa_handler?SIG_IGN??????????????????????????????????????sa_handler?SIG_DFL????ζ??????????????????????????(??????????do_coredump()??)??

???????get_signal_to_deliver()?????????????0?????????????????????????????(???signal()??sigaction()??????????????????????????)????????handle_signal()???????д????handle_signal()????????????￡?

/*
 * OK?? we're invoking a handler
 */
static void
handle_signal(unsigned long sig?? struct k_sigaction *ka??
       siginfo_t *info?? sigset_t *oldset??
       struct pt_regs * regs?? int syscall)
{
 struct thread_info *thread = current_thread_info();
 struct task_struct *tsk = current;
 int usig = sig;
 int ret;

 /*
  * If we were from a system call?? check for system call restarting...
  */
 if (syscall) {
  switch (regs->ARM_r0) {
  case -ERESTART_RESTARTBLOCK:
  case -ERESTARTNOHAND:
   regs->ARM_r0 = -EINTR;
   break;
  case -ERESTARTSYS:
   if (!(ka->sa.sa_flags & SA_RESTART)) {
    regs->ARM_r0 = -EINTR;
    break;
   }
   /* fallthrough */
  case -ERESTARTNOINTR:
   restart_syscall(regs);
  }
 }

 /*
  * translate the signal
  */
 if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
  usig = thread->exec_domain->signal_invmap[usig];

 /*
  * Set up the stack frame//??????
  */
 if (ka->sa.sa_flags & SA_SIGINFO)
  ret = setup_rt_frame(usig?? ka?? info?? oldset?? regs);
 else
  ret = setup_frame(usig?? ka?? oldset?? regs);

 /*
  * Check that the resulting registers are actually sane.
  */
 ret |= !valid_user_regs(regs);

 /*
  * Block the signal if we were unsuccessful.
  */
 if (ret != 0) {
  spin_lock_irq(&tsk->sighand->siglock);
  sigorsets(&tsk->blocked?? &tsk->blocked??
     &ka->sa.sa_mask);
  if (!(ka->sa.sa_flags & SA_NODEFER))
   sigaddset(&tsk->blocked?? sig);
  recalc_sigpending();
  spin_unlock_irq(&tsk->sighand->siglock);
 }

 if (ret == 0)
  return;

 force_sigsegv(sig?? tsk);
}

??????????????￡????????????????????????????????????????????????????????????????????????????????????????????????к????????????t??????????????????????????????????????????????????????????????С???????????У??????????????????????

????1????????????????????????????y????????????????y??????е?????????????????????????y??????????????????????????????

????2??????????????????????????????????????????????????????е??????????????????????????????????????????б?????????ж????????????pt_regs?????ж????????????pt_regts?е?pc?У???????????????????????pt_regs??pc?????sa_handler?????????????????sa_handler???????????

unsigned long handler = (unsigned long)ka->sa.sa_handler;
regs->ARM_pc = handler;