fix signal-based timers with null sigevent argument

since timer_create is no longer allocating a structure for the timer_t
and simply using the kernel timer id, it was impossible to specify the
timer_t as the argument to the signal handler. the solution is to pass
the null sigevent pointer on to the kernel, rather than filling it in
userspace, so that the kernel does the right thing. however, that
precludes the clever timerid-versus-threadid encoding we were doing.

instead, just assume timerids are below 1M and thread pointers are
above 1M. (in perspective: timerids are sequentially allocated and
seem limited to 32k, and thread pointers are at roughly 3G.)

src/time/timer_create.c

@@ -52,40 +52,35 @@ static void *start(void *arg)
 
 int timer_create(clockid_t clk, struct sigevent *evp, timer_t *res)
 {
-	struct sigevent sev = { 
-		.sigev_notify = SIGEV_SIGNAL,
-		.sigev_signo = SIGALRM
-	};
 	pthread_t td;
 	pthread_attr_t attr;
 	int r;
 	struct start_args args;
-	timer_t t;
-	struct ksigevent ksev;
+	struct ksigevent ksev, *ksevp=0;
 	int timerid;
 
-	if (evp) sev = *evp;
-
-	switch (sev.sigev_notify) {
+	switch (evp ? evp->sigev_notify : SIGEV_SIGNAL) {
 	case SIGEV_NONE:
 	case SIGEV_SIGNAL:
-		ksev.sigev_value = evp ? sev.sigev_value
-			: (union sigval){.sival_ptr=t};
-		ksev.sigev_signo = sev.sigev_signo;
-		ksev.sigev_notify = sev.sigev_notify;
-		ksev.sigev_tid = 0;
-		if (syscall(SYS_timer_create, clk, &ksev, &timerid) < 0)
+		if (evp) {
+			ksev.sigev_value = evp->sigev_value;
+			ksev.sigev_signo = evp->sigev_signo;
+			ksev.sigev_notify = evp->sigev_notify;
+			ksev.sigev_tid = 0;
+			ksevp = &ksev;
+		}
+		if (syscall(SYS_timer_create, clk, ksevp, &timerid) < 0)
 			return -1;
-		*res = (void *)(2*timerid+1);
+		*res = (void *)timerid;
 		break;
 	case SIGEV_THREAD:
-		if (sev.sigev_notify_attributes)
-			attr = *sev.sigev_notify_attributes;
+		if (evp->sigev_notify_attributes)
+			attr = *evp->sigev_notify_attributes;
 		else
 			pthread_attr_init(&attr);
 		pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 		pthread_barrier_init(&args.b, 0, 2);
-		args.sev = &sev;
+		args.sev = evp;
 		r = pthread_create(&td, &attr, start, &args);
 		if (r) {
 			errno = r;

src/time/timer_delete.c

@@ -3,7 +3,6 @@
 
 int timer_delete(timer_t t)
 {
-	if ((uintptr_t)t & 1)
-		return __syscall(SYS_timer_delete, ((unsigned long)t / 2));
-	return pthread_cancel(t);
+	if ((uintptr_t)t >= 0x100000) return pthread_cancel(t);
+	return __syscall(SYS_timer_delete, (long)t);
 }

src/time/timer_getoverrun.c

@@ -3,7 +3,6 @@
 
 int timer_getoverrun(timer_t t)
 {
-	if ((uintptr_t)t & 1) t = (void *)((unsigned long)t / 2);
-	else t = ((pthread_t)t)->result;
+	if ((uintptr_t)t >= 0x100000) t = ((pthread_t)t)->result;
 	return syscall(SYS_timer_getoverrun, (long)t);
 }

src/time/timer_gettime.c

@@ -3,7 +3,6 @@
 
 int timer_gettime(timer_t t, struct itimerspec *val)
 {
-	if ((uintptr_t)t & 1) t = (void *)((unsigned long)t / 2);
-	else t = ((pthread_t)t)->result;
+	if ((uintptr_t)t >= 0x100000) t = ((pthread_t)t)->result;
 	return syscall(SYS_timer_gettime, (long)t, val);
 }

src/time/timer_settime.c

@@ -3,7 +3,6 @@
 
 int timer_settime(timer_t t, int flags, const struct itimerspec *val, struct itimerspec *old)
 {
-	if ((uintptr_t)t & 1) t = (void *)((unsigned long)t / 2);
-	else t = ((pthread_t)t)->result;
+	if ((uintptr_t)t >= 0x100000) t = ((pthread_t)t)->result;
 	return syscall(SYS_timer_settime, (long)t, flags, val, old);
 }