signal.c

minix3.1.1源代码

/*===========================================================================*
 *				cause_sigalrm				     *
 *===========================================================================*/
PRIVATE void cause_sigalrm(tp)
struct timer *tp;
{
  int proc_nr;
  register struct mproc *rmp;

  proc_nr = tmr_arg(tp)->ta_int;	/* get process from timer */
  rmp = &mproc[proc_nr];

  if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) return;
  if ((rmp->mp_flags & ALARM_ON) == 0) return;
  rmp->mp_flags &= ~ALARM_ON;
  check_sig(rmp->mp_pid, SIGALRM);
}

/*===========================================================================*
 *				do_pause				     *
 *===========================================================================*/
PUBLIC int do_pause()
{
/* Perform the pause() system call. */

  mp->mp_flags |= PAUSED;
  return(SUSPEND);
}

/*===========================================================================*
 *				sig_proc				     *
 *===========================================================================*/
PUBLIC void sig_proc(rmp, signo)
register struct mproc *rmp;	/* pointer to the process to be signaled */
int signo;			/* signal to send to process (1 to _NSIG) */
{
/* Send a signal to a process.  Check to see if the signal is to be caught,
 * ignored, tranformed into a message (for system processes) or blocked.  
 *  - If the signal is to be transformed into a message, request the KERNEL to
 * send the target process a system notification with the pending signal as an 
 * argument. 
 *  - If the signal is to be caught, request the KERNEL to push a sigcontext 
 * structure and a sigframe structure onto the catcher's stack.  Also, KERNEL 
 * will reset the program counter and stack pointer, so that when the process 
 * next runs, it will be executing the signal handler. When the signal handler 
 * returns,  sigreturn(2) will be called.  Then KERNEL will restore the signal 
 * context from the sigcontext structure.
 * If there is insufficient stack space, kill the process.
 */

  vir_bytes new_sp;
  int s;
  int slot;
  int sigflags;
  struct sigmsg sm;

  slot = (int) (rmp - mproc);
  if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) {
	printf("PM: signal %d sent to %s process %d\n",
		signo, (rmp->mp_flags & ZOMBIE) ? "zombie" : "dead", slot);
	panic(__FILE__,"", NO_NUM);
  }
  if ((rmp->mp_flags & TRACED) && signo != SIGKILL) {
	/* A traced process has special handling. */
	unpause(slot);
	stop_proc(rmp, signo);	/* a signal causes it to stop */
	return;
  }
  /* Some signals are ignored by default. */
  if (sigismember(&rmp->mp_ignore, signo)) { 
  	return;
  }
  if (sigismember(&rmp->mp_sigmask, signo)) {
	/* Signal should be blocked. */
	sigaddset(&rmp->mp_sigpending, signo);
	return;
  }
#if ENABLE_SWAP
  if (rmp->mp_flags & ONSWAP) {
	/* Process is swapped out, leave signal pending. */
	sigaddset(&rmp->mp_sigpending, signo);
	swap_inqueue(rmp);
	return;
  }
#endif
  sigflags = rmp->mp_sigact[signo].sa_flags;
  if (sigismember(&rmp->mp_catch, signo)) {
	if (rmp->mp_flags & SIGSUSPENDED)
		sm.sm_mask = rmp->mp_sigmask2;
	else
		sm.sm_mask = rmp->mp_sigmask;
	sm.sm_signo = signo;
	sm.sm_sighandler = (vir_bytes) rmp->mp_sigact[signo].sa_handler;
	sm.sm_sigreturn = rmp->mp_sigreturn;
	if ((s=get_stack_ptr(slot, &new_sp)) != OK)
		panic(__FILE__,"couldn't get new stack pointer",s);
	sm.sm_stkptr = new_sp;

	/* Make room for the sigcontext and sigframe struct. */
	new_sp -= sizeof(struct sigcontext)
				 + 3 * sizeof(char *) + 2 * sizeof(int);

	if (adjust(rmp, rmp->mp_seg[D].mem_len, new_sp) != OK)
		goto doterminate;

	rmp->mp_sigmask |= rmp->mp_sigact[signo].sa_mask;
	if (sigflags & SA_NODEFER)
		sigdelset(&rmp->mp_sigmask, signo);
	else
		sigaddset(&rmp->mp_sigmask, signo);

	if (sigflags & SA_RESETHAND) {
		sigdelset(&rmp->mp_catch, signo);
		rmp->mp_sigact[signo].sa_handler = SIG_DFL;
	}

	if (OK == (s=sys_sigsend(slot, &sm))) {

		sigdelset(&rmp->mp_sigpending, signo);
		/* If process is hanging on PAUSE, WAIT, SIGSUSPEND, tty, 
		 * pipe, etc., release it.
		 */
		unpause(slot);
		return;
	}
  	panic(__FILE__, "warning, sys_sigsend failed", s);
  }
  else if (sigismember(&rmp->mp_sig2mess, signo)) {
  	if (OK != (s=sys_kill(slot,signo)))
  		panic(__FILE__, "warning, sys_kill failed", s);
  	return;
  }

doterminate:
  /* Signal should not or cannot be caught.  Take default action. */
  if (sigismember(&ign_sset, signo)) return;

  rmp->mp_sigstatus = (char) signo;
  if (sigismember(&core_sset, signo)) {
#if ENABLE_SWAP
	if (rmp->mp_flags & ONSWAP) {
		/* Process is swapped out, leave signal pending. */
		sigaddset(&rmp->mp_sigpending, signo);
		swap_inqueue(rmp);
		return;
	}
#endif
	/* Switch to the user's FS environment and dump core. */
	tell_fs(CHDIR, slot, FALSE, 0);
	dump_core(rmp);
  }
  pm_exit(rmp, 0);		/* terminate process */
}

/*===========================================================================*
 *				check_sig				     *
 *===========================================================================*/
PUBLIC int check_sig(proc_id, signo)
pid_t proc_id;			/* pid of proc to sig, or 0 or -1, or -pgrp */
int signo;			/* signal to send to process (0 to _NSIG) */
{
/* Check to see if it is possible to send a signal.  The signal may have to be
 * sent to a group of processes.  This routine is invoked by the KILL system
 * call, and also when the kernel catches a DEL or other signal.
 */

  register struct mproc *rmp;
  int count;			/* count # of signals sent */
  int error_code;

  if (signo < 0 || signo > _NSIG) return(EINVAL);

  /* Return EINVAL for attempts to send SIGKILL to INIT alone. */
  if (proc_id == INIT_PID && signo == SIGKILL) return(EINVAL);

  /* Search the proc table for processes to signal.  (See forkexit.c about
   * pid magic.)
   */
  count = 0;
  error_code = ESRCH;
  for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
	if (!(rmp->mp_flags & IN_USE)) continue;
	if ((rmp->mp_flags & ZOMBIE) && signo != 0) continue;

	/* Check for selection. */
	if (proc_id > 0 && proc_id != rmp->mp_pid) continue;
	if (proc_id == 0 && mp->mp_procgrp != rmp->mp_procgrp) continue;
	if (proc_id == -1 && rmp->mp_pid <= INIT_PID) continue;
	if (proc_id < -1 && rmp->mp_procgrp != -proc_id) continue;

	/* Check for permission. */
	if (mp->mp_effuid != SUPER_USER
	    && mp->mp_realuid != rmp->mp_realuid
	    && mp->mp_effuid != rmp->mp_realuid
	    && mp->mp_realuid != rmp->mp_effuid
	    && mp->mp_effuid != rmp->mp_effuid) {
		error_code = EPERM;
		continue;
	}

	count++;
	if (signo == 0) continue;

	/* 'sig_proc' will handle the disposition of the signal.  The
	 * signal may be caught, blocked, ignored, or cause process
	 * termination, possibly with core dump.
	 */
	sig_proc(rmp, signo);

	if (proc_id > 0) break;	/* only one process being signaled */
  }

  /* If the calling process has killed itself, don't reply. */
  if ((mp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) return(SUSPEND);
  return(count > 0 ? OK : error_code);
}

/*===========================================================================*
 *				check_pending				     *
 *===========================================================================*/
PUBLIC void check_pending(rmp)
register struct mproc *rmp;
{
  /* Check to see if any pending signals have been unblocked.  The
   * first such signal found is delivered.
   *
   * If multiple pending unmasked signals are found, they will be
   * delivered sequentially.
   *
   * There are several places in this file where the signal mask is
   * changed.  At each such place, check_pending() should be called to
   * check for newly unblocked signals.
   */

  int i;

  for (i = 1; i <= _NSIG; i++) {
	if (sigismember(&rmp->mp_sigpending, i) &&
		!sigismember(&rmp->mp_sigmask, i)) {
		sigdelset(&rmp->mp_sigpending, i);
		sig_proc(rmp, i);
		break;
	}
  }
}

/*===========================================================================*
 *				unpause					     *
 *===========================================================================*/
PRIVATE void unpause(pro)
int pro;			/* which process number */
{
/* A signal is to be sent to a process.  If that process is hanging on a
 * system call, the system call must be terminated with EINTR.  Possible
 * calls are PAUSE, WAIT, READ and WRITE, the latter two for pipes and ttys.
 * First check if the process is hanging on an PM call.  If not, tell FS,
 * so it can check for READs and WRITEs from pipes, ttys and the like.
 */

  register struct mproc *rmp;

  rmp = &mproc[pro];

  /* Check to see if process is hanging on a PAUSE, WAIT or SIGSUSPEND call. */
  if (rmp->mp_flags & (PAUSED | WAITING | SIGSUSPENDED)) {
	rmp->mp_flags &= ~(PAUSED | WAITING | SIGSUSPENDED);
	setreply(pro, EINTR);
	return;
  }

  /* Process is not hanging on an PM call.  Ask FS to take a look. */
  tell_fs(UNPAUSE, pro, 0, 0);
}

/*===========================================================================*
 *				dump_core				     *
 *===========================================================================*/
PRIVATE void dump_core(rmp)
register struct mproc *rmp;	/* whose core is to be dumped */
{
/* Make a core dump on the file "core", if possible. */

  int s, fd, seg, slot;
  vir_bytes current_sp;
  long trace_data, trace_off;

  slot = (int) (rmp - mproc);

  /* Can core file be written?  We are operating in the user's FS environment,
   * so no special permission checks are needed.
   */
  if (rmp->mp_realuid != rmp->mp_effuid) return;
  if ( (fd = open(core_name, O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK,
						CORE_MODE)) < 0) return;
  rmp->mp_sigstatus |= DUMPED;

  /* Make sure the stack segment is up to date.
   * We don't want adjust() to fail unless current_sp is preposterous,
   * but it might fail due to safety checking.  Also, we don't really want 
   * the adjust() for sending a signal to fail due to safety checking.  
   * Maybe make SAFETY_BYTES a parameter.
   */
  if ((s=get_stack_ptr(slot, &current_sp)) != OK)
	panic(__FILE__,"couldn't get new stack pointer",s);
  adjust(rmp, rmp->mp_seg[D].mem_len, current_sp);

  /* Write the memory map of all segments to begin the core file. */
  if (write(fd, (char *) rmp->mp_seg, (unsigned) sizeof rmp->mp_seg)
      != (unsigned) sizeof rmp->mp_seg) {
	close(fd);
	return;
  }

  /* Write out the whole kernel process table entry to get the regs. */
  trace_off = 0;
  while (sys_trace(T_GETUSER, slot, trace_off, &trace_data) == OK) {
	if (write(fd, (char *) &trace_data, (unsigned) sizeof (long))
	    != (unsigned) sizeof (long)) {
		close(fd);
		return;
	}
	trace_off += sizeof (long);
  }

  /* Loop through segments and write the segments themselves out. */
  for (seg = 0; seg < NR_LOCAL_SEGS; seg++) {
	rw_seg(1, fd, slot, seg,
		(phys_bytes) rmp->mp_seg[seg].mem_len << CLICK_SHIFT);
  }
  close(fd);
}