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Date:: Tue Feb 8 19:08:47 2005 UTC
Message:: play nicer with others w.r.t. signal masks
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  1 9acaad45 2004-10-23 devnull /*
  2 9acaad45 2004-10-23 devnull  * Signal handling for Plan 9 programs. 
  3 9acaad45 2004-10-23 devnull  * We stubbornly use the strings from Plan 9 instead 
  4 9acaad45 2004-10-23 devnull  * of the enumerated Unix constants.  
  5 9acaad45 2004-10-23 devnull  * There are some weird translations.  In particular,
  6 9acaad45 2004-10-23 devnull  * a "kill" note is the same as SIGTERM in Unix.
  7 9acaad45 2004-10-23 devnull  * There is no equivalent note to Unix's SIGKILL, since
  8 9acaad45 2004-10-23 devnull  * it's not a deliverable signal anyway.
  9 9acaad45 2004-10-23 devnull  *
 10 5f8fa947 2004-12-26 devnull  * We do not handle SIGABRT or SIGSEGV, mainly because
 11 5f8fa947 2004-12-26 devnull  * the thread library queues its notes for later, and we want
 12 5f8fa947 2004-12-26 devnull  * to dump core with the state at time of delivery.
 13 9acaad45 2004-10-23 devnull  *
 14 9acaad45 2004-10-23 devnull  * We have to add some extra entry points to provide the
 15 9acaad45 2004-10-23 devnull  * ability to tweak which signals are deliverable and which
 16 9acaad45 2004-10-23 devnull  * are acted upon.  Notifydisable and notifyenable play with
 17 9acaad45 2004-10-23 devnull  * the process signal mask.  Notifyignore enables the signal
 18 9acaad45 2004-10-23 devnull  * but will not call notifyf when it comes in.  This is occasionally
 19 9acaad45 2004-10-23 devnull  * useful.
 20 9acaad45 2004-10-23 devnull  */
 21 9acaad45 2004-10-23 devnull 
 22 fd04aace 2003-11-23 devnull #include <u.h>
 23 8ad51794 2004-03-25 devnull #include <signal.h>
 24 fd04aace 2003-11-23 devnull #define NOPLAN9DEFINES
 25 fd04aace 2003-11-23 devnull #include <libc.h>
 26 fd04aace 2003-11-23 devnull 
 27 fd04aace 2003-11-23 devnull extern char *_p9sigstr(int, char*);
 28 9acaad45 2004-10-23 devnull extern int _p9strsig(char*);
 29 fd04aace 2003-11-23 devnull 
 30 9acaad45 2004-10-23 devnull typedef struct Sig Sig;
 31 9acaad45 2004-10-23 devnull struct Sig
 32 9acaad45 2004-10-23 devnull {
 33 9acaad45 2004-10-23 devnull 	int sig;			/* signal number */
 34 f3ecd8ae 2005-02-08 devnull 	int flags;
 35 9acaad45 2004-10-23 devnull };
 36 9acaad45 2004-10-23 devnull 
 37 f3ecd8ae 2005-02-08 devnull enum
 38 f3ecd8ae 2005-02-08 devnull {
 39 f3ecd8ae 2005-02-08 devnull 	Restart = 1<<0,
 40 f3ecd8ae 2005-02-08 devnull 	Ignore = 1<<1,
 41 f3ecd8ae 2005-02-08 devnull };
 42 10f14b04 2005-01-16 devnull 
 43 9acaad45 2004-10-23 devnull static Sig sigs[] = {
 44 f3ecd8ae 2005-02-08 devnull 	SIGHUP,		0,
 45 f3ecd8ae 2005-02-08 devnull 	SIGINT,		0,
 46 f3ecd8ae 2005-02-08 devnull 	SIGQUIT,		0,
 47 f3ecd8ae 2005-02-08 devnull 	SIGILL,		0,
 48 f3ecd8ae 2005-02-08 devnull 	SIGTRAP,		0,
 49 f3ecd8ae 2005-02-08 devnull /*	SIGABRT, 		0, 	*/
 50 d2c4ee9e 2003-11-24 devnull #ifdef SIGEMT
 51 f3ecd8ae 2005-02-08 devnull 	SIGEMT,		0,
 52 d2c4ee9e 2003-11-24 devnull #endif
 53 f3ecd8ae 2005-02-08 devnull 	SIGFPE,		0,
 54 f3ecd8ae 2005-02-08 devnull 	SIGBUS,		0,
 55 f3ecd8ae 2005-02-08 devnull /*	SIGSEGV, 		0, 	*/
 56 f3ecd8ae 2005-02-08 devnull 	SIGCHLD,		Restart|Ignore,
 57 f3ecd8ae 2005-02-08 devnull 	SIGSYS,		0,
 58 f3ecd8ae 2005-02-08 devnull 	SIGPIPE,		Ignore,
 59 f3ecd8ae 2005-02-08 devnull 	SIGALRM,		0,
 60 f3ecd8ae 2005-02-08 devnull 	SIGTERM,		0,
 61 f3ecd8ae 2005-02-08 devnull 	SIGTSTP,		Restart|Ignore,
 62 f3ecd8ae 2005-02-08 devnull 	SIGTTIN,		Restart|Ignore,
 63 f3ecd8ae 2005-02-08 devnull 	SIGTTOU,		Restart|Ignore,
 64 f3ecd8ae 2005-02-08 devnull 	SIGXCPU,		0,
 65 f3ecd8ae 2005-02-08 devnull 	SIGXFSZ,		0,
 66 f3ecd8ae 2005-02-08 devnull 	SIGVTALRM,	0,
 67 f3ecd8ae 2005-02-08 devnull 	SIGUSR1,		0,
 68 f3ecd8ae 2005-02-08 devnull 	SIGUSR2,		0,
 69 f3ecd8ae 2005-02-08 devnull 	SIGWINCH,	Restart|Ignore,
 70 d2c4ee9e 2003-11-24 devnull #ifdef SIGINFO
 71 f3ecd8ae 2005-02-08 devnull 	SIGINFO,		Restart|Ignore,
 72 d2c4ee9e 2003-11-24 devnull #endif
 73 fd04aace 2003-11-23 devnull };
 74 fd04aace 2003-11-23 devnull 
 75 9acaad45 2004-10-23 devnull static Sig*
 76 9acaad45 2004-10-23 devnull findsig(int s)
 77 9acaad45 2004-10-23 devnull {
 78 9acaad45 2004-10-23 devnull 	int i;
 79 9acaad45 2004-10-23 devnull 
 80 9acaad45 2004-10-23 devnull 	for(i=0; i<nelem(sigs); i++)
 81 9acaad45 2004-10-23 devnull 		if(sigs[i].sig == s)
 82 9acaad45 2004-10-23 devnull 			return &sigs[i];
 83 9acaad45 2004-10-23 devnull 	return nil;
 84 9acaad45 2004-10-23 devnull }
 85 9acaad45 2004-10-23 devnull 
 86 9acaad45 2004-10-23 devnull /*
 87 9acaad45 2004-10-23 devnull  * The thread library initializes _notejmpbuf to its own
 88 9acaad45 2004-10-23 devnull  * routine which provides a per-pthread jump buffer.
 89 9acaad45 2004-10-23 devnull  * If we're not using the thread library, we assume we are
 90 9acaad45 2004-10-23 devnull  * single-threaded.
 91 9acaad45 2004-10-23 devnull  */
 92 05d8c6df 2004-09-23 devnull typedef struct Jmp Jmp;
 93 05d8c6df 2004-09-23 devnull struct Jmp
 94 05d8c6df 2004-09-23 devnull {
 95 05d8c6df 2004-09-23 devnull 	p9jmp_buf b;
 96 05d8c6df 2004-09-23 devnull };
 97 05d8c6df 2004-09-23 devnull 
 98 05d8c6df 2004-09-23 devnull static Jmp onejmp;
 99 05d8c6df 2004-09-23 devnull 
100 05d8c6df 2004-09-23 devnull static Jmp*
101 05d8c6df 2004-09-23 devnull getonejmp(void)
102 05d8c6df 2004-09-23 devnull {
103 05d8c6df 2004-09-23 devnull 	return &onejmp;
104 05d8c6df 2004-09-23 devnull }
105 05d8c6df 2004-09-23 devnull 
106 05d8c6df 2004-09-23 devnull Jmp *(*_notejmpbuf)(void) = getonejmp;
107 9acaad45 2004-10-23 devnull static void noteinit(void);
108 fd04aace 2003-11-23 devnull 
109 9acaad45 2004-10-23 devnull /*
110 9acaad45 2004-10-23 devnull  * Actual signal handler. 
111 9acaad45 2004-10-23 devnull  */
112 aa200fe3 2004-10-22 devnull 
113 9acaad45 2004-10-23 devnull static void (*notifyf)(void*, char*);	/* Plan 9 handler */
114 9acaad45 2004-10-23 devnull 
115 aa200fe3 2004-10-22 devnull static void
116 9acaad45 2004-10-23 devnull signotify(int sig)
117 fd04aace 2003-11-23 devnull {
118 fd04aace 2003-11-23 devnull 	char tmp[64];
119 05d8c6df 2004-09-23 devnull 	Jmp *j;
120 f3ecd8ae 2005-02-08 devnull 	Sig *s;
121 fd04aace 2003-11-23 devnull 
122 05d8c6df 2004-09-23 devnull 	j = (*_notejmpbuf)();
123 9acaad45 2004-10-23 devnull 	switch(p9setjmp(j->b)){
124 9acaad45 2004-10-23 devnull 	case 0:
125 9acaad45 2004-10-23 devnull 		if(notifyf)
126 9acaad45 2004-10-23 devnull 			(*notifyf)(nil, _p9sigstr(sig, tmp));
127 9acaad45 2004-10-23 devnull 		/* fall through */
128 9acaad45 2004-10-23 devnull 	case 1:	/* noted(NDFLT) */
129 9acaad45 2004-10-23 devnull 		if(0)print("DEFAULT %d\n", sig);
130 f3ecd8ae 2005-02-08 devnull 		s = findsig(sig);
131 f3ecd8ae 2005-02-08 devnull 		if(s && (s->flags&Ignore))
132 f3ecd8ae 2005-02-08 devnull 			return;
133 9acaad45 2004-10-23 devnull 		signal(sig, SIG_DFL);
134 9acaad45 2004-10-23 devnull 		raise(sig);
135 9acaad45 2004-10-23 devnull 		_exit(1);
136 9acaad45 2004-10-23 devnull 	case 2:	/* noted(NCONT) */
137 05d8c6df 2004-09-23 devnull 		if(0)print("HANDLED %d\n", sig);
138 fd04aace 2003-11-23 devnull 		return;
139 fd04aace 2003-11-23 devnull 	}
140 fd04aace 2003-11-23 devnull }
141 05d8c6df 2004-09-23 devnull 
142 9acaad45 2004-10-23 devnull static void
143 9acaad45 2004-10-23 devnull signonotify(int sig)
144 9acaad45 2004-10-23 devnull {
145 9acaad45 2004-10-23 devnull 	USED(sig);
146 9acaad45 2004-10-23 devnull }
147 9acaad45 2004-10-23 devnull 
148 fd04aace 2003-11-23 devnull int
149 05d8c6df 2004-09-23 devnull noted(int v)
150 05d8c6df 2004-09-23 devnull {
151 05d8c6df 2004-09-23 devnull 	p9longjmp((*_notejmpbuf)()->b, v==NCONT ? 2 : 1);
152 05d8c6df 2004-09-23 devnull 	abort();
153 05d8c6df 2004-09-23 devnull 	return 0;
154 05d8c6df 2004-09-23 devnull }
155 05d8c6df 2004-09-23 devnull 
156 9acaad45 2004-10-23 devnull int
157 9acaad45 2004-10-23 devnull notify(void (*f)(void*, char*))
158 9acaad45 2004-10-23 devnull {
159 9acaad45 2004-10-23 devnull 	static int init;
160 9acaad45 2004-10-23 devnull 
161 9acaad45 2004-10-23 devnull 	notifyf = f;
162 9acaad45 2004-10-23 devnull 	if(!init){
163 9acaad45 2004-10-23 devnull 		init = 1;
164 9acaad45 2004-10-23 devnull 		noteinit();
165 9acaad45 2004-10-23 devnull 	}
166 9acaad45 2004-10-23 devnull 	return 0;
167 9acaad45 2004-10-23 devnull }
168 9acaad45 2004-10-23 devnull 
169 9acaad45 2004-10-23 devnull /*
170 9acaad45 2004-10-23 devnull  * Nonsense about enabling and disabling signals.
171 9acaad45 2004-10-23 devnull  */
172 5f8fa947 2004-12-26 devnull typedef void Sighandler(int);
173 5f8fa947 2004-12-26 devnull static Sighandler*
174 9acaad45 2004-10-23 devnull handler(int s)
175 9acaad45 2004-10-23 devnull {
176 9acaad45 2004-10-23 devnull 	struct sigaction sa;
177 9acaad45 2004-10-23 devnull 
178 9acaad45 2004-10-23 devnull 	sigaction(s, nil, &sa);
179 9acaad45 2004-10-23 devnull 	return sa.sa_handler;
180 9acaad45 2004-10-23 devnull }
181 9acaad45 2004-10-23 devnull 
182 10f14b04 2005-01-16 devnull static int
183 5f8fa947 2004-12-26 devnull notesetenable(int sig, int enabled)
184 fd04aace 2003-11-23 devnull {
185 10f14b04 2005-01-16 devnull 	sigset_t mask, omask;
186 fd04aace 2003-11-23 devnull 
187 9acaad45 2004-10-23 devnull 	if(sig == 0)
188 10f14b04 2005-01-16 devnull 		return -1;
189 aa200fe3 2004-10-22 devnull 
190 9acaad45 2004-10-23 devnull 	sigemptyset(&mask);
191 9acaad45 2004-10-23 devnull 	sigaddset(&mask, sig);
192 10f14b04 2005-01-16 devnull 	sigprocmask(enabled ? SIG_UNBLOCK : SIG_BLOCK, &mask, &omask);
193 10f14b04 2005-01-16 devnull 	return !sigismember(&omask, sig);	
194 9acaad45 2004-10-23 devnull }
195 9acaad45 2004-10-23 devnull 
196 10f14b04 2005-01-16 devnull int
197 5f8fa947 2004-12-26 devnull noteenable(char *msg)
198 9acaad45 2004-10-23 devnull {
199 10f14b04 2005-01-16 devnull 	return notesetenable(_p9strsig(msg), 1);
200 9acaad45 2004-10-23 devnull }
201 9acaad45 2004-10-23 devnull 
202 10f14b04 2005-01-16 devnull int
203 5f8fa947 2004-12-26 devnull notedisable(char *msg)
204 9acaad45 2004-10-23 devnull {
205 10f14b04 2005-01-16 devnull 	return notesetenable(_p9strsig(msg), 0);
206 9acaad45 2004-10-23 devnull }
207 9acaad45 2004-10-23 devnull 
208 10f14b04 2005-01-16 devnull static int
209 9acaad45 2004-10-23 devnull notifyseton(int s, int on)
210 9acaad45 2004-10-23 devnull {
211 9acaad45 2004-10-23 devnull 	Sig *sig;
212 10f14b04 2005-01-16 devnull 	struct sigaction sa, osa;
213 9acaad45 2004-10-23 devnull 
214 9acaad45 2004-10-23 devnull 	sig = findsig(s);
215 9acaad45 2004-10-23 devnull 	if(sig == nil)
216 10f14b04 2005-01-16 devnull 		return -1;
217 669250d1 2003-12-03 devnull 	memset(&sa, 0, sizeof sa);
218 9acaad45 2004-10-23 devnull 	sa.sa_handler = on ? signotify : signonotify;
219 f3ecd8ae 2005-02-08 devnull 	if(sig->flags&Restart)
220 9acaad45 2004-10-23 devnull 		sa.sa_flags |= SA_RESTART;
221 aa200fe3 2004-10-22 devnull 
222 aa200fe3 2004-10-22 devnull 	/*
223 9acaad45 2004-10-23 devnull 	 * We can't allow signals within signals because there's
224 9acaad45 2004-10-23 devnull 	 * only one jump buffer.
225 aa200fe3 2004-10-22 devnull 	 */
226 aa200fe3 2004-10-22 devnull 	sigfillset(&sa.sa_mask);
227 9acaad45 2004-10-23 devnull 
228 9acaad45 2004-10-23 devnull 	/*
229 9acaad45 2004-10-23 devnull 	 * Install handler.
230 9acaad45 2004-10-23 devnull 	 */
231 10f14b04 2005-01-16 devnull 	sigaction(sig->sig, &sa, &osa);
232 10f14b04 2005-01-16 devnull 	return osa.sa_handler == signotify;
233 aa200fe3 2004-10-22 devnull }
234 aa200fe3 2004-10-22 devnull 
235 10f14b04 2005-01-16 devnull int
236 9acaad45 2004-10-23 devnull notifyon(char *msg)
237 aa200fe3 2004-10-22 devnull {
238 10f14b04 2005-01-16 devnull 	return notifyseton(_p9strsig(msg), 1);
239 fd04aace 2003-11-23 devnull }
240 aa200fe3 2004-10-22 devnull 
241 10f14b04 2005-01-16 devnull int
242 9acaad45 2004-10-23 devnull notifyoff(char *msg)
243 aa200fe3 2004-10-22 devnull {
244 10f14b04 2005-01-16 devnull 	return notifyseton(_p9strsig(msg), 0);
245 aa200fe3 2004-10-22 devnull }
246 aa200fe3 2004-10-22 devnull 
247 9acaad45 2004-10-23 devnull /*
248 9acaad45 2004-10-23 devnull  * Initialization follows sigs table.
249 9acaad45 2004-10-23 devnull  */
250 9acaad45 2004-10-23 devnull static void
251 9acaad45 2004-10-23 devnull noteinit(void)
252 aa200fe3 2004-10-22 devnull {
253 aa200fe3 2004-10-22 devnull 	int i;
254 9acaad45 2004-10-23 devnull 	Sig *sig;
255 aa200fe3 2004-10-22 devnull 
256 9acaad45 2004-10-23 devnull 	for(i=0; i<nelem(sigs); i++){
257 9acaad45 2004-10-23 devnull 		sig = &sigs[i];
258 9acaad45 2004-10-23 devnull 		/*
259 9acaad45 2004-10-23 devnull 		 * If someone has already installed a handler,
260 9acaad45 2004-10-23 devnull 		 * It's probably some ld preload nonsense,
261 9acaad45 2004-10-23 devnull 		 * like pct (a SIGVTALRM-based profiler).
262 5f8fa947 2004-12-26 devnull 		 * Or maybe someone has already called notifyon/notifyoff.
263 9acaad45 2004-10-23 devnull 		 * Leave it alone.
264 9acaad45 2004-10-23 devnull 		 */
265 9acaad45 2004-10-23 devnull 		if(handler(sig->sig) != SIG_DFL)
266 9acaad45 2004-10-23 devnull 			continue;
267 f3ecd8ae 2005-02-08 devnull 		notifyseton(sig->sig, 1);
268 9acaad45 2004-10-23 devnull 	}
269 aa200fe3 2004-10-22 devnull }
270 aa200fe3 2004-10-22 devnull