scsh-0.5/scsh/sighandlers1.c

/* Need to define sig2interrupt vector.
** Interrupt-system mutators should probably hold interrupts while they
**   operate.
*/

#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include "cstuff.h"

/* Make sure our exports match up w/the implementation: */
#include "sighandlers1.h"

extern int errno;

extern scheme_value Spending_interruptsS, Sinterrupt_handlersS;

/* Translate Unix signal numbers to S48 interrupt numbers.
** alarm, keyboard (^C, SIGINT), and memory shortage are 0, 1, and 2.
*/

static int sig2interrupt(int signal)
{
  switch (signal) {
    case SIGALRM: return 0;		/* Already defined by S48. */
    case SIGCHLD: return 3;
    case SIGCONT: return 4;
    case SIGHUP: return 5;	
    case SIGINT: return 1;		/* Already defined by S48. */
    case SIGQUIT: return 6;	
    case SIGTERM: return 7;	
    case SIGTSTP: return 8;
    case SIGUSR1: return 9;
    case SIGUSR2: return 10;

#ifdef SIGINFO
    case SIGINFO: return 11;
#endif
#ifdef SIGIO
    case SIGIO: return 12;
#endif
#ifdef SIGPOLL
    case SIGPOLL: return 13;
#endif
#ifdef SIGPROF
    case SIGPROF: return 14;
#endif
#ifdef SIGPWR
    case SIGPWR: return 15;
#endif
#ifdef SIGURG
    case SIGURG: return 16;
#endif
#ifdef SIGVTALRM
    case SIGVTALRM: return 17;
#endif
#ifdef SIGWINCH
    case SIGWINCH: return 18;
#endif
#ifdef SIGXCPU
    case SIGXCPU: return 19;
#endif
#ifdef SIGXFSZ
    case SIGXFSZ: return 20;
#endif
    default: return -1;
  }
}

/* Hack the blocked-signal mask.
*******************************************************************************
*/


#include "machine/sigset.h"

int set_procmask(int hi, int lo, int *old_lo_p)
{
    sigset_t mask, old_mask;
    int old_hi;

    make_sigset(&mask, hi, lo);
    
    sigprocmask(SIG_SETMASK, &mask, &old_mask);
    split_sigset(old_mask, &old_hi, old_lo_p);
    return old_hi;
    }


int get_procmask(int *old_lo_p)
{
    sigset_t old_mask;
    int old_hi;

    sigprocmask(SIG_SETMASK, NULL, &old_mask);
    split_sigset(old_mask, &old_hi, old_lo_p);
    return old_hi;
    }


/* Set/Get signal handlers
*******************************************************************************
*/

static void scm_handle_sig(int sig)
{
  Spending_interruptsS |= (1<<sig2interrupt(sig));
  }


scheme_value set_sig_handler(int sig, scheme_value handler, int flags,
			     scheme_value *ohandler, int *oflags)
{
    struct sigaction new, old;
    int intnum = sig2interrupt(sig);
    scheme_value old_scsh_handler;

    /* intnum in range? */
    if( intnum >= VECTOR_LENGTH(Sinterrupt_handlersS) ) {
        *ohandler = SCHFALSE;
        return ENTER_FIXNUM(-1);
        }

    /* We may need this for ohandler later, but it may get clobbered
    ** when we set the new handler, so stash it away for now.
    */
    old_scsh_handler = VECTOR_REF(Sinterrupt_handlersS, intnum);

    sigemptyset(&new.sa_mask); /* WTF */
    new.sa_flags = flags;

    if( handler == SCHFALSE ) {
        new.sa_handler = SIG_IGN;
        VECTOR_REF(Sinterrupt_handlersS, intnum) = SCHFALSE;
        }

    /* This *really* sets the Unix signal handler to SIG_DFL.
    ** What usually happens isn't this -- what usually happens is that
    ** we establish a special Scheme handler that does the default, so
    ** that it is subject to S48's blocking machinery.
    */
    else if( handler == SCHTRUE ) {
        new.sa_handler = SIG_DFL;
        VECTOR_REF(Sinterrupt_handlersS, intnum) = SCHFALSE;
        }

    else {
	new.sa_handler = scm_handle_sig;

	VECTOR_REF(Sinterrupt_handlersS, intnum) = handler;
	/* Do other stuff. */
	}

    if( sigaction(sig, &new, &old) ) {
	*ohandler = SCHFALSE;
	return ENTER_FIXNUM(errno);
	}

    *oflags = old.sa_flags;
    if( old.sa_handler == SIG_IGN )             *ohandler = SCHFALSE;
    else if( old.sa_handler == SIG_DFL )        *ohandler = SCHTRUE;
    else if( old.sa_handler == scm_handle_sig ) *ohandler = old_scsh_handler;
    else *ohandler = ENTER_FIXNUM(-1); /* Unknown signal handler. */
    return SCHFALSE;
    }


scheme_value get_sig_handler(int signal, scheme_value *handler, int *flags)
{
    struct sigaction old;

    if( sigaction(signal, NULL, &old) ) {
	*handler = SCHFALSE;
	return ENTER_FIXNUM(errno);
	}
	
    *flags = old.sa_flags;

    if( old.sa_handler == SIG_IGN ) *handler = SCHFALSE;

    else if( old.sa_handler == SIG_DFL ) *handler = SCHTRUE;

    else if( old.sa_handler == scm_handle_sig ) {
        int intnum = sig2interrupt(signal);

	/* intnum in range? */
	if( intnum >= VECTOR_LENGTH(Sinterrupt_handlersS) ) {
	    *handler = SCHFALSE;
	    return ENTER_FIXNUM(-1);
	    }

	*handler = VECTOR_REF(Sinterrupt_handlersS, intnum);
	}

    else *handler = ENTER_FIXNUM(-1); /* Unknown signal handler. */

    return SCHFALSE;
    }


/* Return true if SIGNAL's default action is definitely to be ignored. */
/* This should be inlined by a good compiler. */

static int sig_def_is_ignored(int signal)
{
  return
    /* Posix signals */
    signal == SIGALRM || signal == SIGHUP ||
    signal == SIGINT  ||  signal == SIGQUIT ||
    signal == SIGTERM || signal == SIGUSR1 ||
    signal == SIGUSR2 
      
	/* Non-Posix signals, when present. */
#ifdef SIGINFO			
    || signal == SIGINFO
#endif
#ifdef SIGPOLL
    || signal == SIGPOLL
#endif
#ifdef SIGPROF
    || signal == SIGPROF
#endif
#ifdef SIGVTALRM
    || signal == SIGVTALRM
#endif
#ifdef SIGXCPU
    || signal == SIGXCPU
#endif
#ifdef SIGXFSZ
    || signal == SIGXFSZ
#endif
#ifdef SIGIO
    || signal == SIGIO		/* BSD => ignore; SVR4 => terminate */
#endif
    ;
  }
      

/* This guy is responsible for making the default action for a
** Unix signal happen. Because S48's signal handler system is
** interposed between delivery-to-the-process and
** delivery-to-the-scheme-handler, when the user sets a signal
** handler to default, we install a Scheme proc that calls this
** guy, instead of just slapping a SIGDFL in as the Unix handler.
** We only have to do this for signals whose default isn't "ignore," i.e.:
**   Posix: SIGALRM SIGHUP SIGINT SIGQUIT SIGTERM SIGUSR1 SIGUSR2
**   Non-Posix: SIGINFO SIGPOLL SIGPROF SIGVTALRM SIGXCPU SIGXFSZ SIGIO
** This way, the S48 signal-blocking mechanism can work.
**
** Weird, I know.
*/
void do_default_sigaction(int signal)
{
  sigset_t ss, old_ss;
  struct sigaction default_action, old_action;

  if( !sig_def_is_ignored(signal) ) {

      /* OK -- signal's default *isn't* "ignore," so we have to do it. */
      sigfillset(&ss);				/* Block everyone. */
      sigprocmask(SIG_SETMASK, &ss, &old_ss);

      default_action.sa_handler = SIG_DFL;	/* Set for default. */
      sigemptyset(&default_action.sa_mask);
      default_action.sa_flags = 0;
      sigaction(signal, &default_action, &old_action);

      raise(signal);			      	/* Raise the signal. */
      sigdelset(&ss, signal);
      sigprocmask(SIG_SETMASK, &ss, 0); 	/* Handle it. */

      /* Most likely, we'll never get to here, as the default for
      ** the signals we're handling is "terminate," but we'll play it safe.
      */
      sigaction(signal, &old_action, 0);        /* Restore old handler, */
      sigprocmask(SIG_SETMASK, &old_ss, 0);	/* and mask.            */
      }
  }


/* Install a new signal-handler vector.
** I use this because the default one is only 3 entries long, and I
** don't want to modify the S48 source. So I'll just install my own
** at run-time. 
** It's not a hack, it's a kluge.
*/

void install_new_handler_vector(scheme_value handlers)
{
  extern scheme_value Sinterrupt_handlersS;
  Sinterrupt_handlersS = handlers;
  }