mcount.c revision 1574 
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. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)
35static char sccsid[] = "@(#)mcount.c	8.1 (Berkeley) 6/4/93";
36#endif
37
38#include <sys/param.h>
39#include <sys/gmon.h>
40
41/*
42 * mcount is called on entry to each function compiled with the profiling
43 * switch set.  _mcount(), which is declared in a machine-dependent way
44 * with _MCOUNT_DECL, does the actual work and is either inlined into a
45 * C routine or called by an assembly stub.  In any case, this magic is
46 * taken care of by the MCOUNT definition in <machine/profile.h>.
47 *
48 * _mcount updates data structures that represent traversals of the
49 * program's call graph edges.  frompc and selfpc are the return
50 * address and function address that represents the given call graph edge.
51 *
52 * Note: the original BSD code used the same variable (frompcindex) for
53 * both frompcindex and frompc.  Any reasonable, modern compiler will
54 * perform this optimization.
55 */
56_MCOUNT_DECL(frompc, selfpc)	/* _mcount; may be static, inline, etc */
57	register u_long frompc, selfpc;
58{
59	register u_short *frompcindex;
60	register struct tostruct *top, *prevtop;
61	register struct gmonparam *p;
62	register long toindex;
63#ifdef KERNEL
64	register int s;
65#endif
66
67	p = &_gmonparam;
68	/*
69	 * check that we are profiling
70	 * and that we aren't recursively invoked.
71	 */
72	if (p->state != GMON_PROF_ON)
73		return;
74#ifdef KERNEL
75	MCOUNT_ENTER;
76#else
77	p->state = GMON_PROF_BUSY;
78#endif
79	/*
80	 * check that frompcindex is a reasonable pc value.
81	 * for example:	signal catchers get called from the stack,
82	 *		not from text space.  too bad.
83	 */
84	frompc -= p->lowpc;
85	if (frompc > p->textsize)
86		goto done;
87
88	frompcindex = &p->froms[frompc / (p->hashfraction * sizeof(*p->froms))];
89	toindex = *frompcindex;
90	if (toindex == 0) {
91		/*
92		 *	first time traversing this arc
93		 */
94		toindex = ++p->tos[0].link;
95		if (toindex >= p->tolimit)
96			/* halt further profiling */
97			goto overflow;
98
99		*frompcindex = toindex;
100		top = &p->tos[toindex];
101		top->selfpc = selfpc;
102		top->count = 1;
103		top->link = 0;
104		goto done;
105	}
106	top = &p->tos[toindex];
107	if (top->selfpc == selfpc) {
108		/*
109		 * arc at front of chain; usual case.
110		 */
111		top->count++;
112		goto done;
113	}
114	/*
115	 * have to go looking down chain for it.
116	 * top points to what we are looking at,
117	 * prevtop points to previous top.
118	 * we know it is not at the head of the chain.
119	 */
120	for (; /* goto done */; ) {
121		if (top->link == 0) {
122			/*
123			 * top is end of the chain and none of the chain
124			 * had top->selfpc == selfpc.
125			 * so we allocate a new tostruct
126			 * and link it to the head of the chain.
127			 */
128			toindex = ++p->tos[0].link;
129			if (toindex >= p->tolimit)
130				goto overflow;
131
132			top = &p->tos[toindex];
133			top->selfpc = selfpc;
134			top->count = 1;
135			top->link = *frompcindex;
136			*frompcindex = toindex;
137			goto done;
138		}
139		/*
140		 * otherwise, check the next arc on the chain.
141		 */
142		prevtop = top;
143		top = &p->tos[top->link];
144		if (top->selfpc == selfpc) {
145			/*
146			 * there it is.
147			 * increment its count
148			 * move it to the head of the chain.
149			 */
150			top->count++;
151			toindex = prevtop->link;
152			prevtop->link = top->link;
153			top->link = *frompcindex;
154			*frompcindex = toindex;
155			goto done;
156		}
157
158	}
159done:
160#ifdef KERNEL
161	MCOUNT_EXIT;
162#else
163	p->state = GMON_PROF_ON;
164#endif
165	return;
166overflow:
167	p->state = GMON_PROF_ERROR;
168#ifdef KERNEL
169	MCOUNT_EXIT;
170#endif
171	return;
172}
173
174/*
175 * Actual definition of mcount function.  Defined in <machine/profile.h>,
176 * which is included by <sys/gmon.h>.
177 */
178MCOUNT
179