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 * 3. 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 * @(#)mcount.c 8.1 (Berkeley) 6/4/93
30 * $FreeBSD: src/lib/libc/gmon/mcount.c,v 1.20 2004/10/16 06:32:43 obrien Exp $
31 */
32
33 #include <sys/param.h>
34 #include <sys/gmon.h>
35
36 /*
37 * mcount is called on entry to each function compiled with the profiling
38 * switch set. _mcount(), which is declared in a machine-dependent way
39 * with _MCOUNT_DECL, does the actual work and is either inlined into a
40 * C routine or called by an assembly stub. In any case, this magic is
41 * taken care of by the MCOUNT definition in <machine/profile.h>.
42 *
43 * _mcount updates data structures that represent traversals of the
44 * program's call graph edges. frompc and selfpc are the return
45 * address and function address that represents the given call graph edge.
46 *
47 * Note: the original BSD code used the same variable (frompcindex) for
48 * both frompcindex and frompc. Any reasonable, modern compiler will
49 * perform this optimization.
50 */
51 /* _mcount; may be static, inline, etc */
_MCOUNT_DECL(u_long frompc,u_long selfpc)52 _MCOUNT_DECL(u_long frompc, u_long selfpc)
53 {
54 u_long frompci;
55 u_short *frompcindex;
56 struct tostruct *top, *prevtop;
57 struct gmonparam *p;
58 long toindex;
59
60 p = &_gmonparam;
61 /*
62 * check that we are profiling
63 * and that we aren't recursively invoked.
64 */
65 if (p->state != GMON_PROF_ON)
66 return;
67 p->state = GMON_PROF_BUSY; /* XXX */
68 frompci = frompc - p->lowpc;
69
70 /*
71 * check that frompc is a reasonable pc value.
72 * for example: signal catchers get called from the stack,
73 * not from text space. too bad.
74 */
75 if (frompci >= p->textsize)
76 goto done;
77
78 frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
79 toindex = *frompcindex;
80 if (toindex == 0) {
81 /*
82 * first time traversing this arc
83 */
84 toindex = ++p->tos[0].link;
85 if (toindex >= p->tolimit)
86 /* halt further profiling */
87 goto overflow;
88
89 *frompcindex = toindex;
90 top = &p->tos[toindex];
91 top->selfpc = selfpc;
92 top->count = 1;
93 top->link = 0;
94 goto done;
95 }
96 top = &p->tos[toindex];
97 if (top->selfpc == selfpc) {
98 /*
99 * arc at front of chain; usual case.
100 */
101 top->count++;
102 goto done;
103 }
104 /*
105 * have to go looking down chain for it.
106 * top points to what we are looking at,
107 * prevtop points to previous top.
108 * we know it is not at the head of the chain.
109 */
110 for (; /* goto done */; ) {
111 if (top->link == 0) {
112 /*
113 * top is end of the chain and none of the chain
114 * had top->selfpc == selfpc.
115 * so we allocate a new tostruct
116 * and link it to the head of the chain.
117 */
118 toindex = ++p->tos[0].link;
119 if (toindex >= p->tolimit)
120 goto overflow;
121
122 top = &p->tos[toindex];
123 top->selfpc = selfpc;
124 top->count = 1;
125 top->link = *frompcindex;
126 *frompcindex = toindex;
127 goto done;
128 }
129 /*
130 * otherwise, check the next arc on the chain.
131 */
132 prevtop = top;
133 top = &p->tos[top->link];
134 if (top->selfpc == selfpc) {
135 /*
136 * there it is.
137 * increment its count
138 * move it to the head of the chain.
139 */
140 top->count++;
141 toindex = prevtop->link;
142 prevtop->link = top->link;
143 top->link = *frompcindex;
144 *frompcindex = toindex;
145 goto done;
146 }
147
148 }
149 done:
150 p->state = GMON_PROF_ON; /* XXX */
151 return;
152 overflow:
153 p->state = GMON_PROF_ERROR; /* XXX */
154 return;
155 }
156
157 /*
158 * Actual definition of mcount function. Defined in <machine/profile.h>,
159 * which is included by <sys/gmon.h>.
160 */
161 MCOUNT
162