signal.c

minix3.1.1源代码

/* This file handles signals, which are asynchronous events and are generally
 * a messy and unpleasant business.  Signals can be generated by the KILL
 * system call, or from the keyboard (SIGINT) or from the clock (SIGALRM).
 * In all cases control eventually passes to check_sig() to see which processes
 * can be signaled.  The actual signaling is done by sig_proc().
 *
 * The entry points into this file are:
 *   do_sigaction:   perform the SIGACTION system call
 *   do_sigpending:  perform the SIGPENDING system call
 *   do_sigprocmask: perform the SIGPROCMASK system call
 *   do_sigreturn:   perform the SIGRETURN system call
 *   do_sigsuspend:  perform the SIGSUSPEND system call
 *   do_kill:	perform the KILL system call
 *   do_alarm:	perform the ALARM system call by calling set_alarm()
 *   set_alarm:	tell the clock task to start or stop a timer
 *   do_pause:	perform the PAUSE system call
 *   ksig_pending: the kernel notified about pending signals
 *   sig_proc:	interrupt or terminate a signaled process
 *   check_sig: check which processes to signal with sig_proc()
 *   check_pending:  check if a pending signal can now be delivered
 */

#include "pm.h"
#include <sys/stat.h>
#include <sys/ptrace.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include <signal.h>
#include <sys/sigcontext.h>
#include <string.h>
#include "mproc.h"
#include "param.h"

#define CORE_MODE	0777	/* mode to use on core image files */
#define DUMPED          0200	/* bit set in status when core dumped */

FORWARD _PROTOTYPE( void dump_core, (struct mproc *rmp)			);
FORWARD _PROTOTYPE( void unpause, (int pro)				);
FORWARD _PROTOTYPE( void handle_sig, (int proc_nr, sigset_t sig_map)	);
FORWARD _PROTOTYPE( void cause_sigalrm, (struct timer *tp)		);

/*===========================================================================*
 *				do_sigaction				     *
 *===========================================================================*/
PUBLIC int do_sigaction()
{
  int r;
  struct sigaction svec;
  struct sigaction *svp;

  if (m_in.sig_nr == SIGKILL) return(OK);
  if (m_in.sig_nr < 1 || m_in.sig_nr > _NSIG) return (EINVAL);
  svp = &mp->mp_sigact[m_in.sig_nr];
  if ((struct sigaction *) m_in.sig_osa != (struct sigaction *) NULL) {
	r = sys_datacopy(PM_PROC_NR,(vir_bytes) svp,
		who, (vir_bytes) m_in.sig_osa, (phys_bytes) sizeof(svec));
	if (r != OK) return(r);
  }

  if ((struct sigaction *) m_in.sig_nsa == (struct sigaction *) NULL) 
  	return(OK);

  /* Read in the sigaction structure. */
  r = sys_datacopy(who, (vir_bytes) m_in.sig_nsa,
		PM_PROC_NR, (vir_bytes) &svec, (phys_bytes) sizeof(svec));
  if (r != OK) return(r);

  if (svec.sa_handler == SIG_IGN) {
	sigaddset(&mp->mp_ignore, m_in.sig_nr);
	sigdelset(&mp->mp_sigpending, m_in.sig_nr);
	sigdelset(&mp->mp_catch, m_in.sig_nr);
	sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
  } else if (svec.sa_handler == SIG_DFL) {
	sigdelset(&mp->mp_ignore, m_in.sig_nr);
	sigdelset(&mp->mp_catch, m_in.sig_nr);
	sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
  } else if (svec.sa_handler == SIG_MESS) {
	if (! (mp->mp_flags & PRIV_PROC)) return(EPERM);
	sigdelset(&mp->mp_ignore, m_in.sig_nr);
	sigaddset(&mp->mp_sig2mess, m_in.sig_nr);
	sigdelset(&mp->mp_catch, m_in.sig_nr);
  } else {
	sigdelset(&mp->mp_ignore, m_in.sig_nr);
	sigaddset(&mp->mp_catch, m_in.sig_nr);
	sigdelset(&mp->mp_sig2mess, m_in.sig_nr);
  }
  mp->mp_sigact[m_in.sig_nr].sa_handler = svec.sa_handler;
  sigdelset(&svec.sa_mask, SIGKILL);
  mp->mp_sigact[m_in.sig_nr].sa_mask = svec.sa_mask;
  mp->mp_sigact[m_in.sig_nr].sa_flags = svec.sa_flags;
  mp->mp_sigreturn = (vir_bytes) m_in.sig_ret;
  return(OK);
}

/*===========================================================================*
 *				do_sigpending                                *
 *===========================================================================*/
PUBLIC int do_sigpending()
{
  mp->mp_reply.reply_mask = (long) mp->mp_sigpending;
  return OK;
}

/*===========================================================================*
 *				do_sigprocmask                               *
 *===========================================================================*/
PUBLIC int do_sigprocmask()
{
/* Note that the library interface passes the actual mask in sigmask_set,
 * not a pointer to the mask, in order to save a copy.  Similarly,
 * the old mask is placed in the return message which the library
 * interface copies (if requested) to the user specified address.
 *
 * The library interface must set SIG_INQUIRE if the 'act' argument
 * is NULL.
 */

  int i;

  mp->mp_reply.reply_mask = (long) mp->mp_sigmask;

  switch (m_in.sig_how) {
      case SIG_BLOCK:
	sigdelset((sigset_t *)&m_in.sig_set, SIGKILL);
	for (i = 1; i <= _NSIG; i++) {
		if (sigismember((sigset_t *)&m_in.sig_set, i))
			sigaddset(&mp->mp_sigmask, i);
	}
	break;

      case SIG_UNBLOCK:
	for (i = 1; i <= _NSIG; i++) {
		if (sigismember((sigset_t *)&m_in.sig_set, i))
			sigdelset(&mp->mp_sigmask, i);
	}
	check_pending(mp);
	break;

      case SIG_SETMASK:
	sigdelset((sigset_t *) &m_in.sig_set, SIGKILL);
	mp->mp_sigmask = (sigset_t) m_in.sig_set;
	check_pending(mp);
	break;

      case SIG_INQUIRE:
	break;

      default:
	return(EINVAL);
	break;
  }
  return OK;
}

/*===========================================================================*
 *				do_sigsuspend                                *
 *===========================================================================*/
PUBLIC int do_sigsuspend()
{
  mp->mp_sigmask2 = mp->mp_sigmask;	/* save the old mask */
  mp->mp_sigmask = (sigset_t) m_in.sig_set;
  sigdelset(&mp->mp_sigmask, SIGKILL);
  mp->mp_flags |= SIGSUSPENDED;
  check_pending(mp);
  return(SUSPEND);
}

/*===========================================================================*
 *				do_sigreturn				     *
 *===========================================================================*/
PUBLIC int do_sigreturn()
{
/* A user signal handler is done.  Restore context and check for
 * pending unblocked signals.
 */

  int r;

  mp->mp_sigmask = (sigset_t) m_in.sig_set;
  sigdelset(&mp->mp_sigmask, SIGKILL);

  r = sys_sigreturn(who, (struct sigmsg *) m_in.sig_context);
  check_pending(mp);
  return(r);
}

/*===========================================================================*
 *				do_kill					     *
 *===========================================================================*/
PUBLIC int do_kill()
{
/* Perform the kill(pid, signo) system call. */

  return check_sig(m_in.pid, m_in.sig_nr);
}

/*===========================================================================*
 *				ksig_pending				     *
 *===========================================================================*/
PUBLIC int ksig_pending()
{
/* Certain signals, such as segmentation violations originate in the kernel.
 * When the kernel detects such signals, it notifies the PM to take further 
 * action. The PM requests the kernel to send messages with the process
 * slot and bit map for all signaled processes. The File System, for example,
 * uses this mechanism to signal writing on broken pipes (SIGPIPE). 
 *
 * The kernel has notified the PM about pending signals. Request pending
 * signals until all signals are handled. If there are no more signals,
 * NONE is returned in the process number field.
 */ 
 int proc_nr;
 sigset_t sig_map;

 while (TRUE) {
   sys_getksig(&proc_nr, &sig_map); 	/* get an arbitrary pending signal */
   if (NONE == proc_nr) {		/* stop if no more pending signals */
 	break;
   } else {
   	handle_sig(proc_nr, sig_map);	/* handle the received signal */
	sys_endksig(proc_nr);		/* tell kernel it's done */
   }
 } 
 return(SUSPEND);			/* prevents sending reply */
}

/*===========================================================================*
 *				handle_sig				     *
 *===========================================================================*/
PRIVATE void handle_sig(proc_nr, sig_map)
int proc_nr;
sigset_t sig_map;
{
  register struct mproc *rmp;
  int i;
  pid_t proc_id, id;

  rmp = &mproc[proc_nr];
  if ((rmp->mp_flags & (IN_USE | ZOMBIE)) != IN_USE) return;
  proc_id = rmp->mp_pid;
  mp = &mproc[0];			/* pretend signals are from PM */
  mp->mp_procgrp = rmp->mp_procgrp;	/* get process group right */

  /* Check each bit in turn to see if a signal is to be sent.  Unlike
   * kill(), the kernel may collect several unrelated signals for a
   * process and pass them to PM in one blow.  Thus loop on the bit
   * map. For SIGINT, SIGWINCH and SIGQUIT, use proc_id 0 to indicate
   * a broadcast to the recipient's process group.  For SIGKILL, use
   * proc_id -1 to indicate a systemwide broadcast.
   */
  for (i = 1; i <= _NSIG; i++) {
	if (!sigismember(&sig_map, i)) continue;
	switch (i) {
	    case SIGINT:
	    case SIGQUIT:
	    case SIGWINCH:
		id = 0; break;	/* broadcast to process group */
	    case SIGKILL:
		id = -1; break;	/* broadcast to all except INIT */
	    default:
		id = proc_id;
		break;
	}
	check_sig(id, i);
  }
}

/*===========================================================================*
 *				do_alarm				     *
 *===========================================================================*/
PUBLIC int do_alarm()
{
/* Perform the alarm(seconds) system call. */
  return(set_alarm(who, m_in.seconds));
}

/*===========================================================================*
 *				set_alarm				     *
 *===========================================================================*/
PUBLIC int set_alarm(proc_nr, sec)
int proc_nr;			/* process that wants the alarm */
int sec;			/* how many seconds delay before the signal */
{
/* This routine is used by do_alarm() to set the alarm timer.  It is also used
 * to turn the timer off when a process exits with the timer still on.
 */
  clock_t ticks;	/* number of ticks for alarm */
  clock_t exptime;	/* needed for remaining time on previous alarm */
  clock_t uptime;	/* current system time */
  int remaining;	/* previous time left in seconds */
  int s;

  /* First determine remaining time of previous alarm, if set. */
  if (mproc[proc_nr].mp_flags & ALARM_ON) {
  	if ( (s=getuptime(&uptime)) != OK) 
  		panic(__FILE__,"set_alarm couldn't get uptime", s);
  	exptime = *tmr_exp_time(&mproc[proc_nr].mp_timer);
  	remaining = (int) ((exptime - uptime + (HZ-1))/HZ);
  	if (remaining < 0) remaining = 0;	
  } else {
  	remaining = 0; 
  }

  /* Tell the clock task to provide a signal message when the time comes.
   *
   * Large delays cause a lot of problems.  First, the alarm system call
   * takes an unsigned seconds count and the library has cast it to an int.
   * That probably works, but on return the library will convert "negative"
   * unsigneds to errors.  Presumably no one checks for these errors, so
   * force this call through.  Second, If unsigned and long have the same
   * size, converting from seconds to ticks can easily overflow.  Finally,
   * the kernel has similar overflow bugs adding ticks.
   *
   * Fixing this requires a lot of ugly casts to fit the wrong interface
   * types and to avoid overflow traps.  ALRM_EXP_TIME has the right type
   * (clock_t) although it is declared as long.  How can variables like
   * this be declared properly without combinatorial explosion of message
   * types?
   */
  ticks = (clock_t) (HZ * (unsigned long) (unsigned) sec);
  if ( (unsigned long) ticks / HZ != (unsigned) sec)
	ticks = LONG_MAX;	/* eternity (really TMR_NEVER) */

  if (ticks != 0) {
  	pm_set_timer(&mproc[proc_nr].mp_timer, ticks, cause_sigalrm, proc_nr);
  	mproc[proc_nr].mp_flags |=  ALARM_ON;
  } else if (mproc[proc_nr].mp_flags & ALARM_ON) {
  	pm_cancel_timer(&mproc[proc_nr].mp_timer);
  	mproc[proc_nr].mp_flags &= ~ALARM_ON;
  }
  return(remaining);
}