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; may be static, inline, etc */
_MCOUNT_DECL(uintfptr_t frompc,uintfptr_t selfpc)62 _MCOUNT_DECL(uintfptr_t frompc, uintfptr_t selfpc)
63 {
64 #ifdef GUPROF
65 int delta;
66 #endif
67 fptrdiff_t frompci;
68 u_short *frompcindex;
69 struct tostruct *top, *prevtop;
70 struct gmonparam *p;
71 long toindex;
72 #ifdef _KERNEL
73 MCOUNT_DECL(s)
74 #endif
75
76 p = &_gmonparam;
77 #ifndef GUPROF /* XXX */
78 /*
79 * check that we are profiling
80 * and that we aren't recursively invoked.
81 */
82 if (p->state != GMON_PROF_ON)
83 return;
84 #endif
85 #ifdef _KERNEL
86 MCOUNT_ENTER(s);
87 #else
88 p->state = GMON_PROF_BUSY;
89 #endif
90
91 #ifdef _KERNEL
92 /* De-relocate any addresses in a (single) trampoline. */
93 #ifdef MCOUNT_DETRAMP
94 MCOUNT_DETRAMP(frompc);
95 MCOUNT_DETRAMP(selfpc);
96 #endif
97 /*
98 * When we are called from an exception handler, frompc may be
99 * a user address. Convert such frompc's to some representation
100 * in kernel address space.
101 */
102 #ifdef MCOUNT_FROMPC_USER
103 frompc = MCOUNT_FROMPC_USER(frompc);
104 #elif defined(MCOUNT_USERPC)
105 /*
106 * For separate address spaces, we can only guess that addresses
107 * in the range known to us are actually kernel addresses. Outside
108 * of this range, conerting to the user address is fail-safe.
109 */
110 if (frompc < p->lowpc || frompc - p->lowpc >= p->textsize)
111 frompc = MCOUNT_USERPC;
112 #endif
113 #endif /* _KERNEL */
114
115 frompci = frompc - p->lowpc;
116 if (frompci >= p->textsize)
117 goto done;
118
119 #ifdef GUPROF
120 if (p->state == GMON_PROF_HIRES) {
121 /*
122 * Count the time since cputime() was previously called
123 * against `frompc'. Compensate for overheads.
124 *
125 * cputime() sets its prev_count variable to the count when
126 * it is called. This in effect starts a counter for
127 * the next period of execution (normally from now until
128 * the next call to mcount() or mexitcount()). We set
129 * cputime_bias to compensate for our own overhead.
130 *
131 * We use the usual sampling counters since they can be
132 * located efficiently. 4-byte counters are usually
133 * necessary. gprof will add up the scattered counts
134 * just like it does for statistical profiling. All
135 * counts are signed so that underflow in the subtractions
136 * doesn't matter much (negative counts are normally
137 * compensated for by larger counts elsewhere). Underflow
138 * shouldn't occur, but may be caused by slightly wrong
139 * calibrations or from not clearing cputime_bias.
140 */
141 delta = cputime() - cputime_bias - p->mcount_pre_overhead;
142 cputime_bias = p->mcount_post_overhead;
143 KCOUNT(p, frompci) += delta;
144 *p->cputime_count += p->cputime_overhead;
145 *p->mcount_count += p->mcount_overhead;
146 }
147 #endif /* GUPROF */
148
149 #ifdef _KERNEL
150 /*
151 * When we are called from an exception handler, frompc is faked
152 * to be for where the exception occurred. We've just solidified
153 * the count for there. Now convert frompci to an index that
154 * represents the kind of exception so that interruptions appear
155 * in the call graph as calls from those index instead of calls
156 * from all over.
157 */
158 frompc = MCOUNT_FROMPC_INTR(selfpc);
159 if ((frompc - p->lowpc) < p->textsize)
160 frompci = frompc - p->lowpc;
161 #endif
162
163 /*
164 * check that frompc is a reasonable pc value.
165 * for example: signal catchers get called from the stack,
166 * not from text space. too bad.
167 */
168 if (frompci >= p->textsize)
169 goto done;
170
171 frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
172 toindex = *frompcindex;
173 if (toindex == 0) {
174 /*
175 * first time traversing this arc
176 */
177 toindex = ++p->tos[0].link;
178 if (toindex >= p->tolimit)
179 /* halt further profiling */
180 goto overflow;
181
182 *frompcindex = toindex;
183 top = &p->tos[toindex];
184 top->selfpc = selfpc;
185 top->count = 1;
186 top->link = 0;
187 goto done;
188 }
189 top = &p->tos[toindex];
190 if (top->selfpc == selfpc) {
191 /*
192 * arc at front of chain; usual case.
193 */
194 top->count++;
195 goto done;
196 }
197 /*
198 * have to go looking down chain for it.
199 * top points to what we are looking at,
200 * prevtop points to previous top.
201 * we know it is not at the head of the chain.
202 */
203 for (; /* goto done */; ) {
204 if (top->link == 0) {
205 /*
206 * top is end of the chain and none of the chain
207 * had top->selfpc == selfpc.
208 * so we allocate a new tostruct
209 * and link it to the head of the chain.
210 */
211 toindex = ++p->tos[0].link;
212 if (toindex >= p->tolimit)
213 goto overflow;
214
215 top = &p->tos[toindex];
216 top->selfpc = selfpc;
217 top->count = 1;
218 top->link = *frompcindex;
219 *frompcindex = toindex;
220 goto done;
221 }
222 /*
223 * otherwise, check the next arc on the chain.
224 */
225 prevtop = top;
226 top = &p->tos[top->link];
227 if (top->selfpc == selfpc) {
228 /*
229 * there it is.
230 * increment its count
231 * move it to the head of the chain.
232 */
233 top->count++;
234 toindex = prevtop->link;
235 prevtop->link = top->link;
236 top->link = *frompcindex;
237 *frompcindex = toindex;
238 goto done;
239 }
240 }
241 done:
242 #ifdef _KERNEL
243 MCOUNT_EXIT(s);
244 #else
245 p->state = GMON_PROF_ON;
246 #endif
247 return;
248 overflow:
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 */
260 MCOUNT
261
262 #ifdef GUPROF
263 void
mexitcount(uintfptr_t selfpc)264 mexitcount(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
293 void
empty_loop(void)294 empty_loop(void)
295 {
296 int i;
297
298 for (i = 0; i < CALIB_SCALE; i++)
299 __asm __volatile("");
300 }
301
302 void
nullfunc(void)303 nullfunc(void)
304 {
305 __asm __volatile("");
306 }
307
308 void
nullfunc_loop(void)309 nullfunc_loop(void)
310 {
311 int i;
312
313 for (i = 0; i < CALIB_SCALE; i++)
314 nullfunc();
315 }
316 #endif /* GUPROF */
317