1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1983, 1992, 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
32#include <sys/cdefs.h>
33__FBSDID("$FreeBSD$");
34
35#include <sys/param.h>
36#include <sys/gmon.h>
37#ifdef _KERNEL
38#ifndef GUPROF
39#include <sys/systm.h>
40#endif
41#include <vm/vm.h>
42#include <vm/vm_param.h>
43#include <vm/pmap.h>
44#endif
45
46/*
47 * mcount is called on entry to each function compiled with the profiling
48 * switch set.  _mcount(), which is declared in a machine-dependent way
49 * with _MCOUNT_DECL, does the actual work and is either inlined into a
50 * C routine or called by an assembly stub.  In any case, this magic is
51 * taken care of by the MCOUNT definition in <machine/profile.h>.
52 *
53 * _mcount updates data structures that represent traversals of the
54 * program's call graph edges.  frompc and selfpc are the return
55 * address and function address that represents the given call graph edge.
56 *
57 * Note: the original BSD code used the same variable (frompcindex) for
58 * both frompcindex and frompc.  Any reasonable, modern compiler will
59 * perform this optimization.
60 */
61_MCOUNT_DECL(uintfptr_t frompc, uintfptr_t selfpc)	/* _mcount; may be static, inline, etc */
62{
63#ifdef GUPROF
64	int delta;
65#endif
66	fptrdiff_t frompci;
67	u_short *frompcindex;
68	struct tostruct *top, *prevtop;
69	struct gmonparam *p;
70	long toindex;
71#ifdef _KERNEL
72	MCOUNT_DECL(s)
73#endif
74
75	p = &_gmonparam;
76#ifndef GUPROF			/* XXX */
77	/*
78	 * check that we are profiling
79	 * and that we aren't recursively invoked.
80	 */
81	if (p->state != GMON_PROF_ON)
82		return;
83#endif
84#ifdef _KERNEL
85	MCOUNT_ENTER(s);
86#else
87	p->state = GMON_PROF_BUSY;
88#endif
89
90#ifdef _KERNEL
91	/* De-relocate any addresses in a (single) trampoline. */
92#ifdef MCOUNT_DETRAMP
93	MCOUNT_DETRAMP(frompc);
94	MCOUNT_DETRAMP(selfpc);
95#endif
96	/*
97	 * When we are called from an exception handler, frompc may be
98	 * a user address.  Convert such frompc's to some representation
99	 * in kernel address space.
100	 */
101#ifdef MCOUNT_FROMPC_USER
102	frompc = MCOUNT_FROMPC_USER(frompc);
103#elif defined(MCOUNT_USERPC)
104	/*
105	 * For separate address spaces, we can only guess that addresses
106	 * in the range known to us are actually kernel addresses.  Outside
107	 * of this range, conerting to the user address is fail-safe.
108	 */
109	if (frompc < p->lowpc || frompc - p->lowpc >= p->textsize)
110		frompc = MCOUNT_USERPC;
111#endif
112#endif /* _KERNEL */
113
114	frompci = frompc - p->lowpc;
115	if (frompci >= p->textsize)
116		goto done;
117
118#ifdef GUPROF
119	if (p->state == GMON_PROF_HIRES) {
120		/*
121		 * Count the time since cputime() was previously called
122		 * against `frompc'.  Compensate for overheads.
123		 *
124		 * cputime() sets its prev_count variable to the count when
125		 * it is called.  This in effect starts a counter for
126		 * the next period of execution (normally from now until
127		 * the next call to mcount() or mexitcount()).  We set
128		 * cputime_bias to compensate for our own overhead.
129		 *
130		 * We use the usual sampling counters since they can be
131		 * located efficiently.  4-byte counters are usually
132		 * necessary.  gprof will add up the scattered counts
133		 * just like it does for statistical profiling.  All
134		 * counts are signed so that underflow in the subtractions
135		 * doesn't matter much (negative counts are normally
136		 * compensated for by larger counts elsewhere).  Underflow
137		 * shouldn't occur, but may be caused by slightly wrong
138		 * calibrations or from not clearing cputime_bias.
139		 */
140		delta = cputime() - cputime_bias - p->mcount_pre_overhead;
141		cputime_bias = p->mcount_post_overhead;
142		KCOUNT(p, frompci) += delta;
143		*p->cputime_count += p->cputime_overhead;
144		*p->mcount_count += p->mcount_overhead;
145	}
146#endif /* GUPROF */
147
148#ifdef _KERNEL
149	/*
150	 * When we are called from an exception handler, frompc is faked
151	 * to be for where the exception occurred.  We've just solidified
152	 * the count for there.  Now convert frompci to an index that
153	 * represents the kind of exception so that interruptions appear
154	 * in the call graph as calls from those index instead of calls
155	 * from all over.
156	 */
157	frompc = MCOUNT_FROMPC_INTR(selfpc);
158	if ((frompc - p->lowpc) < p->textsize)
159		frompci = frompc - p->lowpc;
160#endif
161
162	/*
163	 * check that frompc is a reasonable pc value.
164	 * for example:	signal catchers get called from the stack,
165	 *		not from text space.  too bad.
166	 */
167	if (frompci >= p->textsize)
168		goto done;
169
170	frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
171	toindex = *frompcindex;
172	if (toindex == 0) {
173		/*
174		 *	first time traversing this arc
175		 */
176		toindex = ++p->tos[0].link;
177		if (toindex >= p->tolimit)
178			/* halt further profiling */
179			goto overflow;
180
181		*frompcindex = toindex;
182		top = &p->tos[toindex];
183		top->selfpc = selfpc;
184		top->count = 1;
185		top->link = 0;
186		goto done;
187	}
188	top = &p->tos[toindex];
189	if (top->selfpc == selfpc) {
190		/*
191		 * arc at front of chain; usual case.
192		 */
193		top->count++;
194		goto done;
195	}
196	/*
197	 * have to go looking down chain for it.
198	 * top points to what we are looking at,
199	 * prevtop points to previous top.
200	 * we know it is not at the head of the chain.
201	 */
202	for (; /* goto done */; ) {
203		if (top->link == 0) {
204			/*
205			 * top is end of the chain and none of the chain
206			 * had top->selfpc == selfpc.
207			 * so we allocate a new tostruct
208			 * and link it to the head of the chain.
209			 */
210			toindex = ++p->tos[0].link;
211			if (toindex >= p->tolimit)
212				goto overflow;
213
214			top = &p->tos[toindex];
215			top->selfpc = selfpc;
216			top->count = 1;
217			top->link = *frompcindex;
218			*frompcindex = toindex;
219			goto done;
220		}
221		/*
222		 * otherwise, check the next arc on the chain.
223		 */
224		prevtop = top;
225		top = &p->tos[top->link];
226		if (top->selfpc == selfpc) {
227			/*
228			 * there it is.
229			 * increment its count
230			 * move it to the head of the chain.
231			 */
232			top->count++;
233			toindex = prevtop->link;
234			prevtop->link = top->link;
235			top->link = *frompcindex;
236			*frompcindex = toindex;
237			goto done;
238		}
239
240	}
241done:
242#ifdef _KERNEL
243	MCOUNT_EXIT(s);
244#else
245	p->state = GMON_PROF_ON;
246#endif
247	return;
248overflow:
249	p->state = GMON_PROF_ERROR;
250#ifdef _KERNEL
251	MCOUNT_EXIT(s);
252#endif
253	return;
254}
255
256/*
257 * Actual definition of mcount function.  Defined in <machine/profile.h>,
258 * which is included by <sys/gmon.h>.
259 */
260MCOUNT
261
262#ifdef GUPROF
263void
264mexitcount(uintfptr_t selfpc)
265{
266	struct gmonparam *p;
267	uintfptr_t selfpcdiff;
268
269	p = &_gmonparam;
270#ifdef MCOUNT_DETRAMP
271	MCOUNT_DETRAMP(selfpc);
272#endif
273	selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
274	if (selfpcdiff < p->textsize) {
275		int delta;
276
277		/*
278		 * Count the time since cputime() was previously called
279		 * against `selfpc'.  Compensate for overheads.
280		 */
281		delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
282		cputime_bias = p->mexitcount_post_overhead;
283		KCOUNT(p, selfpcdiff) += delta;
284		*p->cputime_count += p->cputime_overhead;
285		*p->mexitcount_count += p->mexitcount_overhead;
286	}
287}
288
289#ifndef __GNUCLIKE_ASM
290#error "This file uses null asms to prevent timing loops being optimized away."
291#endif
292
293void
294empty_loop()
295{
296	int i;
297
298	for (i = 0; i < CALIB_SCALE; i++)
299		__asm __volatile("");
300}
301
302void
303nullfunc()
304{
305	__asm __volatile("");
306}
307
308void
309nullfunc_loop()
310{
311	int i;
312
313	for (i = 0; i < CALIB_SCALE; i++)
314		nullfunc();
315}
316#endif /* GUPROF */
317