xref: /netbsd-src/sys/kern/subr_prof.c (revision 567a3a02e796214c92957e0949056e9002633394)
1 /*	$NetBSD: subr_prof.c,v 1.50 2021/08/14 17:51:20 ryo Exp $	*/
2 
3 /*-
4  * Copyright (c) 1982, 1986, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  *	@(#)subr_prof.c	8.4 (Berkeley) 2/14/95
32  */
33 
34 #include <sys/cdefs.h>
35 __KERNEL_RCSID(0, "$NetBSD: subr_prof.c,v 1.50 2021/08/14 17:51:20 ryo Exp $");
36 
37 #ifdef _KERNEL_OPT
38 #include "opt_gprof.h"
39 #include "opt_multiprocessor.h"
40 #endif
41 
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
45 #include <sys/proc.h>
46 #include <sys/mount.h>
47 #include <sys/syscallargs.h>
48 #include <sys/sysctl.h>
49 
50 #include <sys/cpu.h>
51 
52 #ifdef GPROF
53 #include <sys/malloc.h>
54 #include <sys/gmon.h>
55 #include <sys/xcall.h>
56 
57 MALLOC_DEFINE(M_GPROF, "gprof", "kernel profiling buffer");
58 
59 static int sysctl_kern_profiling(SYSCTLFN_ARGS);
60 #ifdef MULTIPROCESSOR
61 void _gmonparam_merge(struct gmonparam *, struct gmonparam *);
62 #endif
63 
64 /*
65  * Froms is actually a bunch of unsigned shorts indexing tos
66  */
67 struct gmonparam _gmonparam = { .state = GMON_PROF_OFF };
68 
69 /* Actual start of the kernel text segment. */
70 extern char kernel_text[];
71 
72 extern char etext[];
73 
74 
75 void
kmstartup(void)76 kmstartup(void)
77 {
78 	char *cp;
79 	struct gmonparam *p = &_gmonparam;
80 	unsigned long size;
81 	/*
82 	 * Round lowpc and highpc to multiples of the density we're using
83 	 * so the rest of the scaling (here and in gprof) stays in ints.
84 	 */
85 	p->lowpc = rounddown(((u_long)kernel_text),
86 		HISTFRACTION * sizeof(HISTCOUNTER));
87 	p->highpc = roundup((u_long)etext,
88 		HISTFRACTION * sizeof(HISTCOUNTER));
89 	p->textsize = p->highpc - p->lowpc;
90 	printf("Profiling kernel, textsize=%ld [%lx..%lx]\n",
91 	       p->textsize, p->lowpc, p->highpc);
92 	p->kcountsize = p->textsize / HISTFRACTION;
93 	p->hashfraction = HASHFRACTION;
94 	p->fromssize = p->textsize / HASHFRACTION;
95 	p->tolimit = p->textsize * ARCDENSITY / 100;
96 	if (p->tolimit < MINARCS)
97 		p->tolimit = MINARCS;
98 	else if (p->tolimit > MAXARCS)
99 		p->tolimit = MAXARCS;
100 	p->tossize = p->tolimit * sizeof(struct tostruct);
101 
102 	size = p->kcountsize + p->fromssize + p->tossize;
103 #ifdef MULTIPROCESSOR
104 	CPU_INFO_ITERATOR cii;
105 	struct cpu_info *ci;
106 	for (CPU_INFO_FOREACH(cii, ci)) {
107 		p = malloc(sizeof(struct gmonparam) + size, M_GPROF,
108 		    M_NOWAIT | M_ZERO);
109 		if (p == NULL) {
110 			printf("No memory for profiling on %s\n",
111 			    cpu_name(ci));
112 			/* cannot profile on this cpu */
113 			continue;
114 		}
115 		memcpy(p, &_gmonparam, sizeof(_gmonparam));
116 		ci->ci_gmon = p;
117 
118 		/*
119 		 * To allow profiling to be controlled only by the global
120 		 * _gmonparam.state, set the default value for each CPU to
121 		 * GMON_PROF_ON. If _gmonparam.state is not ON, mcount will
122 		 * not be executed.
123 		 * This is For compatibility of the kgmon(8) kmem interface.
124 		 */
125 		p->state = GMON_PROF_ON;
126 
127 		cp = (char *)(p + 1);
128 		p->tos = (struct tostruct *)cp;
129 		p->kcount = (u_short *)(cp + p->tossize);
130 		p->froms = (u_short *)(cp + p->tossize + p->kcountsize);
131 	}
132 
133 	sysctl_createv(NULL, 0, NULL, NULL,
134 	    0, CTLTYPE_NODE, "percpu",
135 	    SYSCTL_DESCR("per cpu profiling information"),
136 	    NULL, 0, NULL, 0,
137 	    CTL_KERN, KERN_PROF, GPROF_PERCPU, CTL_EOL);
138 
139 	for (CPU_INFO_FOREACH(cii, ci)) {
140 		if (ci->ci_gmon == NULL)
141 			continue;
142 
143 		sysctl_createv(NULL, 0, NULL, NULL,
144 		    0, CTLTYPE_NODE, cpu_name(ci),
145 		    NULL,
146 		    NULL, 0, NULL, 0,
147 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci), CTL_EOL);
148 
149 		sysctl_createv(NULL, 0, NULL, NULL,
150 		    CTLFLAG_READWRITE, CTLTYPE_INT, "state",
151 		    SYSCTL_DESCR("Profiling state"),
152 		    sysctl_kern_profiling, 0, (void *)ci, 0,
153 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci),
154 		    GPROF_STATE, CTL_EOL);
155 		sysctl_createv(NULL, 0, NULL, NULL,
156 		    CTLFLAG_READWRITE, CTLTYPE_STRUCT, "count",
157 		    SYSCTL_DESCR("Array of statistical program counters"),
158 		    sysctl_kern_profiling, 0, (void *)ci, 0,
159 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci),
160 		    GPROF_COUNT, CTL_EOL);
161 		sysctl_createv(NULL, 0, NULL, NULL,
162 		    CTLFLAG_READWRITE, CTLTYPE_STRUCT, "froms",
163 		    SYSCTL_DESCR("Array indexed by program counter of "
164 		    "call-from points"),
165 		    sysctl_kern_profiling, 0, (void *)ci, 0,
166 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci),
167 		    GPROF_FROMS, CTL_EOL);
168 		sysctl_createv(NULL, 0, NULL, NULL,
169 		    CTLFLAG_READWRITE, CTLTYPE_STRUCT, "tos",
170 		    SYSCTL_DESCR("Array of structures describing "
171 		    "destination of calls and their counts"),
172 		    sysctl_kern_profiling, 0, (void *)ci, 0,
173 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci),
174 		    GPROF_TOS, CTL_EOL);
175 		sysctl_createv(NULL, 0, NULL, NULL,
176 		    CTLFLAG_READWRITE, CTLTYPE_STRUCT, "gmonparam",
177 		    SYSCTL_DESCR("Structure giving the sizes of the above "
178 		    "arrays"),
179 		    sysctl_kern_profiling, 0, (void *)ci, 0,
180 		    CTL_KERN, KERN_PROF, GPROF_PERCPU, cpu_index(ci),
181 		    GPROF_GMONPARAM, CTL_EOL);
182 	}
183 
184 	/*
185 	 * For minimal compatibility of the kgmon(8) kmem interface,
186 	 * the _gmonparam and cpu0:ci_gmon share buffers.
187 	 */
188 	p = curcpu()->ci_gmon;
189 	if (p != NULL) {
190 		_gmonparam.tos = p->tos;
191 		_gmonparam.kcount = p->kcount;
192 		_gmonparam.froms = p->froms;
193 	}
194 #else /* MULTIPROCESSOR */
195 	cp = malloc(size, M_GPROF, M_NOWAIT | M_ZERO);
196 	if (cp == 0) {
197 		printf("No memory for profiling.\n");
198 		return;
199 	}
200 	p->tos = (struct tostruct *)cp;
201 	cp += p->tossize;
202 	p->kcount = (u_short *)cp;
203 	cp += p->kcountsize;
204 	p->froms = (u_short *)cp;
205 #endif /* MULTIPROCESSOR */
206 }
207 
208 #ifdef MULTIPROCESSOR
209 static void
prof_set_state_xc(void * arg1,void * arg2 __unused)210 prof_set_state_xc(void *arg1, void *arg2 __unused)
211 {
212 	int state = PTRTOUINT64(arg1);
213 	struct gmonparam *gp = curcpu()->ci_gmon;
214 
215 	if (gp != NULL)
216 		gp->state = state;
217 }
218 #endif /* MULTIPROCESSOR */
219 
220 /*
221  * Return kernel profiling information.
222  */
223 /*
224  * sysctl helper routine for kern.profiling subtree.  enables/disables
225  * kernel profiling and gives out copies of the profiling data.
226  */
227 static int
sysctl_kern_profiling(SYSCTLFN_ARGS)228 sysctl_kern_profiling(SYSCTLFN_ARGS)
229 {
230 	struct sysctlnode node = *rnode;
231 	struct gmonparam *gp;
232 	int error;
233 #ifdef MULTIPROCESSOR
234 	CPU_INFO_ITERATOR cii;
235 	struct cpu_info *ci, *target_ci;
236 	uint64_t where;
237 	int state;
238 	bool prof_on, do_merge;
239 
240 	target_ci = (struct cpu_info *)rnode->sysctl_data;
241 	do_merge = (oldp != NULL) && (target_ci == NULL) &&
242 	    ((node.sysctl_num == GPROF_COUNT) ||
243 	    (node.sysctl_num == GPROF_FROMS) ||
244 	    (node.sysctl_num == GPROF_TOS));
245 
246 	if (do_merge) {
247 		/* kern.profiling.{count,froms,tos} */
248 		unsigned long size;
249 		char *cp;
250 
251 		/* allocate temporary gmonparam, and merge results of all CPU */
252 		size = _gmonparam.kcountsize + _gmonparam.fromssize +
253 		    _gmonparam.tossize;
254 		gp = malloc(sizeof(struct gmonparam) + size, M_GPROF,
255 		    M_NOWAIT | M_ZERO);
256 		if (gp == NULL)
257 			return ENOMEM;
258 		memcpy(gp, &_gmonparam, sizeof(_gmonparam));
259 		cp = (char *)(gp + 1);
260 		gp->tos = (struct tostruct *)cp;
261 		gp->kcount = (u_short *)(cp + gp->tossize);
262 		gp->froms = (u_short *)(cp + gp->tossize + gp->kcountsize);
263 
264 		for (CPU_INFO_FOREACH(cii, ci)) {
265 			if (ci->ci_gmon == NULL)
266 				continue;
267 			_gmonparam_merge(gp, ci->ci_gmon);
268 		}
269 	} else if (target_ci != NULL) {
270 		/* kern.profiling.percpu.* */
271 		gp = target_ci->ci_gmon;
272 	} else {
273 		/* kern.profiling.{state,gmonparam} */
274 		gp = &_gmonparam;
275 	}
276 #else /* MULTIPROCESSOR */
277 	gp = &_gmonparam;
278 #endif
279 
280 	switch (node.sysctl_num) {
281 	case GPROF_STATE:
282 #ifdef MULTIPROCESSOR
283 		/*
284 		 * if _gmonparam.state is OFF, the state of each CPU is
285 		 * considered to be OFF, even if it is actually ON.
286 		 */
287 		if (_gmonparam.state == GMON_PROF_OFF ||
288 		    gp->state == GMON_PROF_OFF)
289 			state = GMON_PROF_OFF;
290 		else
291 			state = GMON_PROF_ON;
292 		node.sysctl_data = &state;
293 #else
294 		node.sysctl_data = &gp->state;
295 #endif
296 		break;
297 	case GPROF_COUNT:
298 		node.sysctl_data = gp->kcount;
299 		node.sysctl_size = gp->kcountsize;
300 		break;
301 	case GPROF_FROMS:
302 		node.sysctl_data = gp->froms;
303 		node.sysctl_size = gp->fromssize;
304 		break;
305 	case GPROF_TOS:
306 		node.sysctl_data = gp->tos;
307 		node.sysctl_size = gp->tossize;
308 		break;
309 	case GPROF_GMONPARAM:
310 		node.sysctl_data = gp;
311 		node.sysctl_size = sizeof(*gp);
312 		break;
313 	default:
314 		return (EOPNOTSUPP);
315 	}
316 
317 	error = sysctl_lookup(SYSCTLFN_CALL(&node));
318 	if (error || newp == NULL)
319 		goto done;
320 
321 #ifdef MULTIPROCESSOR
322 	switch (node.sysctl_num) {
323 	case GPROF_STATE:
324 		if (target_ci != NULL) {
325 			where = xc_unicast(0, prof_set_state_xc,
326 			    UINT64TOPTR(state), NULL, target_ci);
327 			xc_wait(where);
328 
329 			/* if even one CPU being profiled, enable perfclock. */
330 			prof_on = false;
331 			for (CPU_INFO_FOREACH(cii, ci)) {
332 				if (ci->ci_gmon == NULL)
333 					continue;
334 				if (ci->ci_gmon->state != GMON_PROF_OFF) {
335 					prof_on = true;
336 					break;
337 				}
338 			}
339 			mutex_spin_enter(&proc0.p_stmutex);
340 			if (prof_on)
341 				startprofclock(&proc0);
342 			else
343 				stopprofclock(&proc0);
344 			mutex_spin_exit(&proc0.p_stmutex);
345 
346 			if (prof_on) {
347 				_gmonparam.state = GMON_PROF_ON;
348 			} else {
349 				_gmonparam.state = GMON_PROF_OFF;
350 				/*
351 				 * when _gmonparam.state and all CPU gmon state
352 				 * are OFF, all CPU states should be ON so that
353 				 * the entire CPUs profiling can be controlled
354 				 * by _gmonparam.state only.
355 				 */
356 				for (CPU_INFO_FOREACH(cii, ci)) {
357 					if (ci->ci_gmon == NULL)
358 						continue;
359 					ci->ci_gmon->state = GMON_PROF_ON;
360 				}
361 			}
362 		} else {
363 			_gmonparam.state = state;
364 			where = xc_broadcast(0, prof_set_state_xc,
365 			    UINT64TOPTR(state), NULL);
366 			xc_wait(where);
367 
368 			mutex_spin_enter(&proc0.p_stmutex);
369 			if (state == GMON_PROF_OFF)
370 				stopprofclock(&proc0);
371 			else
372 				startprofclock(&proc0);
373 			mutex_spin_exit(&proc0.p_stmutex);
374 		}
375 		break;
376 	case GPROF_COUNT:
377 		/*
378 		 * if 'kern.profiling.{count,froms,tos}' is written, the same
379 		 * data will be written to 'kern.profiling.percpu.cpuN.xxx'
380 		 */
381 		if (target_ci == NULL) {
382 			for (CPU_INFO_FOREACH(cii, ci)) {
383 				if (ci->ci_gmon == NULL)
384 					continue;
385 				memmove(ci->ci_gmon->kcount, gp->kcount,
386 				    newlen);
387 			}
388 		}
389 		break;
390 	case GPROF_FROMS:
391 		if (target_ci == NULL) {
392 			for (CPU_INFO_FOREACH(cii, ci)) {
393 				if (ci->ci_gmon == NULL)
394 					continue;
395 				memmove(ci->ci_gmon->froms, gp->froms, newlen);
396 			}
397 		}
398 		break;
399 	case GPROF_TOS:
400 		if (target_ci == NULL) {
401 			for (CPU_INFO_FOREACH(cii, ci)) {
402 				if (ci->ci_gmon == NULL)
403 					continue;
404 				memmove(ci->ci_gmon->tos, gp->tos, newlen);
405 			}
406 		}
407 		break;
408 	}
409 #else
410 	if (node.sysctl_num == GPROF_STATE) {
411 		mutex_spin_enter(&proc0.p_stmutex);
412 		if (gp->state == GMON_PROF_OFF)
413 			stopprofclock(&proc0);
414 		else
415 			startprofclock(&proc0);
416 		mutex_spin_exit(&proc0.p_stmutex);
417 	}
418 #endif
419 
420  done:
421 #ifdef MULTIPROCESSOR
422 	if (do_merge)
423 		free(gp, M_GPROF);
424 #endif
425 	return error;
426 }
427 
428 SYSCTL_SETUP(sysctl_kern_gprof_setup, "sysctl kern.profiling subtree setup")
429 {
430 
431 	sysctl_createv(clog, 0, NULL, NULL,
432 		       CTLFLAG_PERMANENT,
433 		       CTLTYPE_NODE, "profiling",
434 		       SYSCTL_DESCR("Profiling information (available)"),
435 		       NULL, 0, NULL, 0,
436 		       CTL_KERN, KERN_PROF, CTL_EOL);
437 
438 	sysctl_createv(clog, 0, NULL, NULL,
439 		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
440 		       CTLTYPE_INT, "state",
441 		       SYSCTL_DESCR("Profiling state"),
442 		       sysctl_kern_profiling, 0, NULL, 0,
443 		       CTL_KERN, KERN_PROF, GPROF_STATE, CTL_EOL);
444 	sysctl_createv(clog, 0, NULL, NULL,
445 		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
446 		       CTLTYPE_STRUCT, "count",
447 		       SYSCTL_DESCR("Array of statistical program counters"),
448 		       sysctl_kern_profiling, 0, NULL, 0,
449 		       CTL_KERN, KERN_PROF, GPROF_COUNT, CTL_EOL);
450 	sysctl_createv(clog, 0, NULL, NULL,
451 		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
452 		       CTLTYPE_STRUCT, "froms",
453 		       SYSCTL_DESCR("Array indexed by program counter of "
454 				    "call-from points"),
455 		       sysctl_kern_profiling, 0, NULL, 0,
456 		       CTL_KERN, KERN_PROF, GPROF_FROMS, CTL_EOL);
457 	sysctl_createv(clog, 0, NULL, NULL,
458 		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
459 		       CTLTYPE_STRUCT, "tos",
460 		       SYSCTL_DESCR("Array of structures describing "
461 				    "destination of calls and their counts"),
462 		       sysctl_kern_profiling, 0, NULL, 0,
463 		       CTL_KERN, KERN_PROF, GPROF_TOS, CTL_EOL);
464 	sysctl_createv(clog, 0, NULL, NULL,
465 		       CTLFLAG_PERMANENT,
466 		       CTLTYPE_STRUCT, "gmonparam",
467 		       SYSCTL_DESCR("Structure giving the sizes of the above "
468 				    "arrays"),
469 		       sysctl_kern_profiling, 0, NULL, 0,
470 		       CTL_KERN, KERN_PROF, GPROF_GMONPARAM, CTL_EOL);
471 }
472 #endif /* GPROF */
473 
474 /*
475  * Profiling system call.
476  *
477  * The scale factor is a fixed point number with 16 bits of fraction, so that
478  * 1.0 is represented as 0x10000.  A scale factor of 0 turns off profiling.
479  */
480 /* ARGSUSED */
481 int
sys_profil(struct lwp * l,const struct sys_profil_args * uap,register_t * retval)482 sys_profil(struct lwp *l, const struct sys_profil_args *uap, register_t *retval)
483 {
484 	/* {
485 		syscallarg(char *) samples;
486 		syscallarg(size_t) size;
487 		syscallarg(u_long) offset;
488 		syscallarg(u_int) scale;
489 	} */
490 	struct proc *p = l->l_proc;
491 	struct uprof *upp;
492 
493 	if (SCARG(uap, scale) > (1 << 16))
494 		return (EINVAL);
495 	if (SCARG(uap, scale) == 0) {
496 		mutex_spin_enter(&p->p_stmutex);
497 		stopprofclock(p);
498 		mutex_spin_exit(&p->p_stmutex);
499 		return (0);
500 	}
501 	upp = &p->p_stats->p_prof;
502 
503 	/* Block profile interrupts while changing state. */
504 	mutex_spin_enter(&p->p_stmutex);
505 	upp->pr_off = SCARG(uap, offset);
506 	upp->pr_scale = SCARG(uap, scale);
507 	upp->pr_base = SCARG(uap, samples);
508 	upp->pr_size = SCARG(uap, size);
509 	startprofclock(p);
510 	mutex_spin_exit(&p->p_stmutex);
511 
512 	return (0);
513 }
514 
515 /*
516  * Scale is a fixed-point number with the binary point 16 bits
517  * into the value, and is <= 1.0.  pc is at most 32 bits, so the
518  * intermediate result is at most 48 bits.
519  */
520 #define	PC_TO_INDEX(pc, prof) \
521 	((int)(((u_quad_t)((pc) - (prof)->pr_off) * \
522 	    (u_quad_t)((prof)->pr_scale)) >> 16) & ~1)
523 
524 /*
525  * Collect user-level profiling statistics; called on a profiling tick,
526  * when a process is running in user-mode.  This routine may be called
527  * from an interrupt context.  We schedule an AST that will vector us
528  * to trap() with a context in which copyin and copyout will work.
529  * Trap will then call addupc_task().
530  *
531  * XXX We could use ufetch/ustore here if the profile buffers were
532  * wired.
533  *
534  * Note that we may (rarely) not get around to the AST soon enough, and
535  * lose profile ticks when the next tick overwrites this one, but in this
536  * case the system is overloaded and the profile is probably already
537  * inaccurate.
538  */
539 void
addupc_intr(struct lwp * l,u_long pc)540 addupc_intr(struct lwp *l, u_long pc)
541 {
542 	struct uprof *prof;
543 	struct proc *p;
544 	u_int i;
545 
546 	p = l->l_proc;
547 
548 	KASSERT(mutex_owned(&p->p_stmutex));
549 
550 	prof = &p->p_stats->p_prof;
551 	if (pc < prof->pr_off ||
552 	    (i = PC_TO_INDEX(pc, prof)) >= prof->pr_size)
553 		return;			/* out of range; ignore */
554 
555 	mutex_spin_exit(&p->p_stmutex);
556 
557 	/* XXXSMP */
558 	prof->pr_addr = pc;
559 	prof->pr_ticks++;
560 	cpu_need_proftick(l);
561 
562 	mutex_spin_enter(&p->p_stmutex);
563 }
564 
565 /*
566  * Much like before, but we can afford to take faults here.  If the
567  * update fails, we simply turn off profiling.
568  */
569 void
addupc_task(struct lwp * l,u_long pc,u_int ticks)570 addupc_task(struct lwp *l, u_long pc, u_int ticks)
571 {
572 	struct uprof *prof;
573 	struct proc *p;
574 	void *addr;
575 	int error;
576 	u_int i;
577 	u_short v;
578 
579 	p = l->l_proc;
580 
581 	if (ticks == 0)
582 		return;
583 
584 	mutex_spin_enter(&p->p_stmutex);
585 	prof = &p->p_stats->p_prof;
586 
587 	/* Testing P_PROFIL may be unnecessary, but is certainly safe. */
588 	if ((p->p_stflag & PST_PROFIL) == 0 || pc < prof->pr_off ||
589 	    (i = PC_TO_INDEX(pc, prof)) >= prof->pr_size) {
590 		mutex_spin_exit(&p->p_stmutex);
591 		return;
592 	}
593 
594 	addr = prof->pr_base + i;
595 	mutex_spin_exit(&p->p_stmutex);
596 	if ((error = copyin(addr, (void *)&v, sizeof(v))) == 0) {
597 		v += ticks;
598 		error = copyout((void *)&v, addr, sizeof(v));
599 	}
600 	if (error != 0) {
601 		mutex_spin_enter(&p->p_stmutex);
602 		stopprofclock(p);
603 		mutex_spin_exit(&p->p_stmutex);
604 	}
605 }
606