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 #if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)
31 static char sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
32 #endif
33
34 #include <unistd.h>
35 #include <sys/param.h>
36 #include <sys/gmon.h>
37
38 /* This file provides the machine-dependent definitions of the _MCOUNT_DECL
39 and MCOUNT macros. */
40 #include <machine-gmon.h>
41
42 #include <atomic.h>
43
44 #include <not-cancel.h>
45 #include <unistd.h>
46 #define ERR(s) __write_nocancel (STDERR_FILENO, s, sizeof (s) - 1)
47
48 /*
49 * mcount is called on entry to each function compiled with the profiling
50 * switch set. _mcount(), which is declared in a machine-dependent way
51 * with _MCOUNT_DECL, does the actual work and is either inlined into a
52 * C routine or called by an assembly stub. In any case, this magic is
53 * taken care of by the MCOUNT definition in <machine/profile.h>.
54 *
55 * _mcount updates data structures that represent traversals of the
56 * program's call graph edges. frompc and selfpc are the return
57 * address and function address that represents the given call graph edge.
58 *
59 * Note: the original BSD code used the same variable (frompcindex) for
60 * both frompcindex and frompc. Any reasonable, modern compiler will
61 * perform this optimization.
62 */
63 _MCOUNT_DECL(frompc, selfpc) /* _mcount; may be static, inline, etc */
64 {
65 ARCINDEX *frompcindex;
66 struct tostruct *top, *prevtop;
67 struct gmonparam *p;
68 ARCINDEX toindex;
69 int i;
70
71 p = &_gmonparam;
72 /*
73 * check that we are profiling
74 * and that we aren't recursively invoked.
75 */
76 if (atomic_compare_and_exchange_bool_acq (&p->state, GMON_PROF_BUSY,
77 GMON_PROF_ON))
78 return;
79
80 /*
81 * check that frompcindex is a reasonable pc value.
82 * for example: signal catchers get called from the stack,
83 * not from text space. too bad.
84 */
85 frompc -= p->lowpc;
86 if (frompc > p->textsize)
87 goto done;
88
89 /* The following test used to be
90 if (p->log_hashfraction >= 0)
91 But we can simplify this if we assume the profiling data
92 is always initialized by the functions in gmon.c. But
93 then it is possible to avoid a runtime check and use the
94 same `if' as in gmon.c. So keep these tests in sync. */
95 if ((HASHFRACTION & (HASHFRACTION - 1)) == 0) {
96 /* avoid integer divide if possible: */
97 i = frompc >> p->log_hashfraction;
98 } else {
99 i = frompc / (p->hashfraction * sizeof(*p->froms));
100 }
101 frompcindex = &p->froms[i];
102 toindex = *frompcindex;
103 if (toindex == 0) {
104 /*
105 * first time traversing this arc
106 */
107 toindex = ++p->tos[0].link;
108 if (toindex >= p->tolimit)
109 /* halt further profiling */
110 goto overflow;
111
112 *frompcindex = toindex;
113 top = &p->tos[toindex];
114 top->selfpc = selfpc;
115 top->count = 1;
116 top->link = 0;
117 goto done;
118 }
119 top = &p->tos[toindex];
120 if (top->selfpc == selfpc) {
121 /*
122 * arc at front of chain; usual case.
123 */
124 top->count++;
125 goto done;
126 }
127 /*
128 * have to go looking down chain for it.
129 * top points to what we are looking at,
130 * prevtop points to previous top.
131 * we know it is not at the head of the chain.
132 */
133 for (; /* goto done */; ) {
134 if (top->link == 0) {
135 /*
136 * top is end of the chain and none of the chain
137 * had top->selfpc == selfpc.
138 * so we allocate a new tostruct
139 * and link it to the head of the chain.
140 */
141 toindex = ++p->tos[0].link;
142 if (toindex >= p->tolimit)
143 goto overflow;
144
145 top = &p->tos[toindex];
146 top->selfpc = selfpc;
147 top->count = 1;
148 top->link = *frompcindex;
149 *frompcindex = toindex;
150 goto done;
151 }
152 /*
153 * otherwise, check the next arc on the chain.
154 */
155 prevtop = top;
156 top = &p->tos[top->link];
157 if (top->selfpc == selfpc) {
158 /*
159 * there it is.
160 * increment its count
161 * move it to the head of the chain.
162 */
163 top->count++;
164 toindex = prevtop->link;
165 prevtop->link = top->link;
166 top->link = *frompcindex;
167 *frompcindex = toindex;
168 goto done;
169 }
170
171 }
172 done:
173 p->state = GMON_PROF_ON;
174 return;
175 overflow:
176 p->state = GMON_PROF_ERROR;
177 ERR("mcount: call graph buffer size limit exceeded, gmon.out will not be generated\n");
178 return;
179 }
180
181 /*
182 * Actual definition of mcount function. Defined in <machine/profile.h>,
183 * which is included by <sys/gmon.h>.
184 */
185 MCOUNT