minimal plan9port to cross-build Jehanne

lib/lib9/notify.c

@@ -0,0 +1,272 @@
+/*
+ * Signal handling for Plan 9 programs.
+ * We stubbornly use the strings from Plan 9 instead
+ * of the enumerated Unix constants.
+ * There are some weird translations.  In particular,
+ * a "kill" note is the same as SIGTERM in Unix.
+ * There is no equivalent note to Unix's SIGKILL, since
+ * it's not a deliverable signal anyway.
+ *
+ * We do not handle SIGABRT or SIGSEGV, mainly because
+ * the thread library queues its notes for later, and we want
+ * to dump core with the state at time of delivery.
+ *
+ * We have to add some extra entry points to provide the
+ * ability to tweak which signals are deliverable and which
+ * are acted upon.  Notifydisable and notifyenable play with
+ * the process signal mask.  Notifyignore enables the signal
+ * but will not call notifyf when it comes in.  This is occasionally
+ * useful.
+ */
+
+#include <u.h>
+#include <signal.h>
+#define NOPLAN9DEFINES
+#include <libc.h>
+
+extern char *_p9sigstr(int, char*);
+extern int _p9strsig(char*);
+
+typedef struct Sig Sig;
+struct Sig
+{
+	int sig;			/* signal number */
+	int flags;
+};
+
+enum
+{
+	Restart = 1<<0,
+	Ignore = 1<<1,
+	NoNotify = 1<<2,
+};
+
+static Sig sigs[] = {
+	SIGHUP,		0,
+	SIGINT,		0,
+	SIGQUIT,		0,
+	SIGILL,		0,
+	SIGTRAP,		0,
+/*	SIGABRT, 		0, 	*/
+#ifdef SIGEMT
+	SIGEMT,		0,
+#endif
+	SIGFPE,		0,
+	SIGBUS,		0,
+/*	SIGSEGV, 		0, 	*/
+	SIGCHLD,		Restart|Ignore,
+	SIGSYS,		0,
+	SIGPIPE,		Ignore,
+	SIGALRM,		0,
+	SIGTERM,		0,
+	SIGTSTP,		Restart|Ignore|NoNotify,
+/*	SIGTTIN,		Restart|Ignore, */
+/*	SIGTTOU,		Restart|Ignore, */
+	SIGXCPU,		0,
+	SIGXFSZ,		0,
+	SIGVTALRM,	0,
+	SIGUSR1,		0,
+	SIGUSR2,		0,
+#ifdef SIGWINCH
+	SIGWINCH,	Restart|Ignore|NoNotify,
+#endif
+#ifdef SIGINFO
+	SIGINFO,		Restart|Ignore|NoNotify,
+#endif
+};
+
+static Sig*
+findsig(int s)
+{
+	int i;
+
+	for(i=0; i<nelem(sigs); i++)
+		if(sigs[i].sig == s)
+			return &sigs[i];
+	return nil;
+}
+
+/*
+ * The thread library initializes _notejmpbuf to its own
+ * routine which provides a per-pthread jump buffer.
+ * If we're not using the thread library, we assume we are
+ * single-threaded.
+ */
+typedef struct Jmp Jmp;
+struct Jmp
+{
+	p9jmp_buf b;
+};
+
+static Jmp onejmp;
+
+static Jmp*
+getonejmp(void)
+{
+	return &onejmp;
+}
+
+Jmp *(*_notejmpbuf)(void) = getonejmp;
+static void noteinit(void);
+
+/*
+ * Actual signal handler.
+ */
+
+static void (*notifyf)(void*, char*);	/* Plan 9 handler */
+
+static void
+signotify(int sig)
+{
+	char tmp[64];
+	Jmp *j;
+	Sig *s;
+
+	j = (*_notejmpbuf)();
+	switch(p9setjmp(j->b)){
+	case 0:
+		if(notifyf)
+			(*notifyf)(nil, _p9sigstr(sig, tmp));
+		/* fall through */
+	case 1:	/* noted(NDFLT) */
+		if(0)print("DEFAULT %d\n", sig);
+		s = findsig(sig);
+		if(s && (s->flags&Ignore))
+			return;
+		signal(sig, SIG_DFL);
+		raise(sig);
+		_exit(1);
+	case 2:	/* noted(NCONT) */
+		if(0)print("HANDLED %d\n", sig);
+		return;
+	}
+}
+
+static void
+signonotify(int sig)
+{
+	USED(sig);
+}
+
+int
+noted(int v)
+{
+	p9longjmp((*_notejmpbuf)()->b, v==NCONT ? 2 : 1);
+	abort();
+	return 0;
+}
+
+int
+notify(void (*f)(void*, char*))
+{
+	static int init;
+
+	notifyf = f;
+	if(!init){
+		init = 1;
+		noteinit();
+	}
+	return 0;
+}
+
+/*
+ * Nonsense about enabling and disabling signals.
+ */
+typedef void Sighandler(int);
+static Sighandler*
+handler(int s)
+{
+	struct sigaction sa;
+
+	sigaction(s, nil, &sa);
+	return sa.sa_handler;
+}
+
+static int
+notesetenable(int sig, int enabled)
+{
+	sigset_t mask, omask;
+
+	if(sig == 0)
+		return -1;
+
+	sigemptyset(&mask);
+	sigaddset(&mask, sig);
+	sigprocmask(enabled ? SIG_UNBLOCK : SIG_BLOCK, &mask, &omask);
+	return !sigismember(&omask, sig);
+}
+
+int
+noteenable(char *msg)
+{
+	return notesetenable(_p9strsig(msg), 1);
+}
+
+int
+notedisable(char *msg)
+{
+	return notesetenable(_p9strsig(msg), 0);
+}
+
+static int
+notifyseton(int s, int on)
+{
+	Sig *sig;
+	struct sigaction sa, osa;
+
+	sig = findsig(s);
+	if(sig == nil)
+		return -1;
+	memset(&sa, 0, sizeof sa);
+	sa.sa_handler = on ? signotify : signonotify;
+	if(sig->flags&Restart)
+		sa.sa_flags |= SA_RESTART;
+
+	/*
+	 * We can't allow signals within signals because there's
+	 * only one jump buffer.
+	 */
+	sigfillset(&sa.sa_mask);
+
+	/*
+	 * Install handler.
+	 */
+	sigaction(sig->sig, &sa, &osa);
+	return osa.sa_handler == signotify;
+}
+
+int
+notifyon(char *msg)
+{
+	return notifyseton(_p9strsig(msg), 1);
+}
+
+int
+notifyoff(char *msg)
+{
+	return notifyseton(_p9strsig(msg), 0);
+}
+
+/*
+ * Initialization follows sigs table.
+ */
+static void
+noteinit(void)
+{
+	int i;
+	Sig *sig;
+
+	for(i=0; i<nelem(sigs); i++){
+		sig = &sigs[i];
+		/*
+		 * If someone has already installed a handler,
+		 * It's probably some ld preload nonsense,
+		 * like pct (a SIGVTALRM-based profiler).
+		 * Or maybe someone has already called notifyon/notifyoff.
+		 * Leave it alone.
+		 */
+		if(handler(sig->sig) != SIG_DFL)
+			continue;
+		notifyseton(sig->sig, !(sig->flags&NoNotify));
+	}
+}