1/*-
2 * Copyright (c) 1983, 1992, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/param.h>
34#include <sys/gmon.h>
35#ifdef _KERNEL
36#ifndef GUPROF
37#include <sys/systm.h>
38#endif
39#include <vm/vm.h>
40#include <vm/vm_param.h>
41#include <vm/pmap.h>
42#endif
43
44/*
45 * mcount is called on entry to each function compiled with the profiling
46 * switch set.  _mcount(), which is declared in a machine-dependent way
47 * with _MCOUNT_DECL, does the actual work and is either inlined into a
48 * C routine or called by an assembly stub.  In any case, this magic is
49 * taken care of by the MCOUNT definition in <machine/profile.h>.
50 *
51 * _mcount updates data structures that represent traversals of the
52 * program's call graph edges.  frompc and selfpc are the return
53 * address and function address that represents the given call graph edge.
54 *
55 * Note: the original BSD code used the same variable (frompcindex) for
56 * both frompcindex and frompc.  Any reasonable, modern compiler will
57 * perform this optimization.
58 */
59_MCOUNT_DECL(frompc, selfpc)	/* _mcount; may be static, inline, etc */
60	uintfptr_t frompc, selfpc;
61{
62#ifdef GUPROF
63	int delta;
64#endif
65	fptrdiff_t frompci;
66	u_short *frompcindex;
67	struct tostruct *top, *prevtop;
68	struct gmonparam *p;
69	long toindex;
70#ifdef _KERNEL
71	MCOUNT_DECL(s)
72#endif
73
74	p = &_gmonparam;
75#ifndef GUPROF			/* XXX */
76	/*
77	 * check that we are profiling
78	 * and that we aren't recursively invoked.
79	 */
80	if (p->state != GMON_PROF_ON)
81		return;
82#endif
83#ifdef _KERNEL
84	MCOUNT_ENTER(s);
85#else
86	p->state = GMON_PROF_BUSY;
87#endif
88
89#ifdef _KERNEL
90	/*
91	 * When we are called from an exception handler, frompc may be
92	 * a user address.  Convert such frompc's to some representation
93	 * in kernel address space.
94	 */
95	frompc = MCOUNT_FROMPC_USER(frompc);
96#endif
97
98	frompci = frompc - p->lowpc;
99	if (frompci >= p->textsize)
100		goto done;
101
102#ifdef GUPROF
103	if (p->state == GMON_PROF_HIRES) {
104		/*
105		 * Count the time since cputime() was previously called
106		 * against `frompc'.  Compensate for overheads.
107		 *
108		 * cputime() sets its prev_count variable to the count when
109		 * it is called.  This in effect starts a counter for
110		 * the next period of execution (normally from now until
111		 * the next call to mcount() or mexitcount()).  We set
112		 * cputime_bias to compensate for our own overhead.
113		 *
114		 * We use the usual sampling counters since they can be
115		 * located efficiently.  4-byte counters are usually
116		 * necessary.  gprof will add up the scattered counts
117		 * just like it does for statistical profiling.  All
118		 * counts are signed so that underflow in the subtractions
119		 * doesn't matter much (negative counts are normally
120		 * compensated for by larger counts elsewhere).  Underflow
121		 * shouldn't occur, but may be caused by slightly wrong
122		 * calibrations or from not clearing cputime_bias.
123		 */
124		delta = cputime() - cputime_bias - p->mcount_pre_overhead;
125		cputime_bias = p->mcount_post_overhead;
126		KCOUNT(p, frompci) += delta;
127		*p->cputime_count += p->cputime_overhead;
128		*p->mcount_count += p->mcount_overhead;
129	}
130#endif /* GUPROF */
131
132#ifdef _KERNEL
133	/*
134	 * When we are called from an exception handler, frompc is faked
135	 * to be for where the exception occurred.  We've just solidified
136	 * the count for there.  Now convert frompci to an index that
137	 * represents the kind of exception so that interruptions appear
138	 * in the call graph as calls from those index instead of calls
139	 * from all over.
140	 */
141	frompc = MCOUNT_FROMPC_INTR(selfpc);
142	if ((frompc - p->lowpc) < p->textsize)
143		frompci = frompc - p->lowpc;
144#endif
145
146	/*
147	 * check that frompc is a reasonable pc value.
148	 * for example:	signal catchers get called from the stack,
149	 *		not from text space.  too bad.
150	 */
151	if (frompci >= p->textsize)
152		goto done;
153
154	frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
155	toindex = *frompcindex;
156	if (toindex == 0) {
157		/*
158		 *	first time traversing this arc
159		 */
160		toindex = ++p->tos[0].link;
161		if (toindex >= p->tolimit)
162			/* halt further profiling */
163			goto overflow;
164
165		*frompcindex = toindex;
166		top = &p->tos[toindex];
167		top->selfpc = selfpc;
168		top->count = 1;
169		top->link = 0;
170		goto done;
171	}
172	top = &p->tos[toindex];
173	if (top->selfpc == selfpc) {
174		/*
175		 * arc at front of chain; usual case.
176		 */
177		top->count++;
178		goto done;
179	}
180	/*
181	 * have to go looking down chain for it.
182	 * top points to what we are looking at,
183	 * prevtop points to previous top.
184	 * we know it is not at the head of the chain.
185	 */
186	for (; /* goto done */; ) {
187		if (top->link == 0) {
188			/*
189			 * top is end of the chain and none of the chain
190			 * had top->selfpc == selfpc.
191			 * so we allocate a new tostruct
192			 * and link it to the head of the chain.
193			 */
194			toindex = ++p->tos[0].link;
195			if (toindex >= p->tolimit)
196				goto overflow;
197
198			top = &p->tos[toindex];
199			top->selfpc = selfpc;
200			top->count = 1;
201			top->link = *frompcindex;
202			*frompcindex = toindex;
203			goto done;
204		}
205		/*
206		 * otherwise, check the next arc on the chain.
207		 */
208		prevtop = top;
209		top = &p->tos[top->link];
210		if (top->selfpc == selfpc) {
211			/*
212			 * there it is.
213			 * increment its count
214			 * move it to the head of the chain.
215			 */
216			top->count++;
217			toindex = prevtop->link;
218			prevtop->link = top->link;
219			top->link = *frompcindex;
220			*frompcindex = toindex;
221			goto done;
222		}
223
224	}
225done:
226#ifdef _KERNEL
227	MCOUNT_EXIT(s);
228#else
229	p->state = GMON_PROF_ON;
230#endif
231	return;
232overflow:
233	p->state = GMON_PROF_ERROR;
234#ifdef _KERNEL
235	MCOUNT_EXIT(s);
236#endif
237	return;
238}
239
240/*
241 * Actual definition of mcount function.  Defined in <machine/profile.h>,
242 * which is included by <sys/gmon.h>.
243 */
244MCOUNT
245
246#ifdef GUPROF
247void
248mexitcount(selfpc)
249	uintfptr_t selfpc;
250{
251	struct gmonparam *p;
252	uintfptr_t selfpcdiff;
253
254	p = &_gmonparam;
255	selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
256	if (selfpcdiff < p->textsize) {
257		int delta;
258
259		/*
260		 * Count the time since cputime() was previously called
261		 * against `selfpc'.  Compensate for overheads.
262		 */
263		delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
264		cputime_bias = p->mexitcount_post_overhead;
265		KCOUNT(p, selfpcdiff) += delta;
266		*p->cputime_count += p->cputime_overhead;
267		*p->mexitcount_count += p->mexitcount_overhead;
268	}
269}
270
271#ifndef __GNUCLIKE_ASM
272#error "This file uses null asms to prevent timing loops being optimized away."
273#endif
274
275void
276empty_loop()
277{
278	int i;
279
280	for (i = 0; i < CALIB_SCALE; i++)
281		__asm __volatile("");
282}
283
284void
285nullfunc()
286{
287	__asm __volatile("");
288}
289
290void
291nullfunc_loop()
292{
293	int i;
294
295	for (i = 0; i < CALIB_SCALE; i++)
296		nullfunc();
297}
298#endif /* GUPROF */
299