mcount.c revision 8870 
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#ifdef KERNEL
41#include <i386/include/cpufunc.h>
42#endif
43
44/*
45 * mcount is called on entry to each function compiled with the profiling
46 * switch set.  _mcount(), which is declared in a machine-dependent way
47 * with _MCOUNT_DECL, does the actual work and is either inlined into a
48 * C routine or called by an assembly stub.  In any case, this magic is
49 * taken care of by the MCOUNT definition in <machine/profile.h>.
50 *
51 * _mcount updates data structures that represent traversals of the
52 * program's call graph edges.  frompc and selfpc are the return
53 * address and function address that represents the given call graph edge.
54 *
55 * Note: the original BSD code used the same variable (frompcindex) for
56 * both frompcindex and frompc.  Any reasonable, modern compiler will
57 * perform this optimization.
58 */
59_MCOUNT_DECL(frompc, selfpc)	/* _mcount; may be static, inline, etc */
60	register u_long frompc, selfpc;
61{
62	register u_short *frompcindex;
63	register struct tostruct *top, *prevtop;
64	register struct gmonparam *p;
65	register long toindex;
66#ifdef KERNEL
67	register int s;
68	u_long save_eflags;
69#endif
70
71	p = &_gmonparam;
72	/*
73	 * check that we are profiling
74	 * and that we aren't recursively invoked.
75	 */
76	if (p->state != GMON_PROF_ON)
77		return;
78#ifdef KERNEL
79	MCOUNT_ENTER;
80#else
81	p->state = GMON_PROF_BUSY;
82#endif
83	/*
84	 * check that frompcindex is a reasonable pc value.
85	 * for example:	signal catchers get called from the stack,
86	 *		not from text space.  too bad.
87	 */
88	frompc -= p->lowpc;
89	if (frompc > p->textsize)
90		goto done;
91
92	frompcindex = &p->froms[frompc / (p->hashfraction * sizeof(*p->froms))];
93	toindex = *frompcindex;
94	if (toindex == 0) {
95		/*
96		 *	first time traversing this arc
97		 */
98		toindex = ++p->tos[0].link;
99		if (toindex >= p->tolimit)
100			/* halt further profiling */
101			goto overflow;
102
103		*frompcindex = toindex;
104		top = &p->tos[toindex];
105		top->selfpc = selfpc;
106		top->count = 1;
107		top->link = 0;
108		goto done;
109	}
110	top = &p->tos[toindex];
111	if (top->selfpc == selfpc) {
112		/*
113		 * arc at front of chain; usual case.
114		 */
115		top->count++;
116		goto done;
117	}
118	/*
119	 * have to go looking down chain for it.
120	 * top points to what we are looking at,
121	 * prevtop points to previous top.
122	 * we know it is not at the head of the chain.
123	 */
124	for (; /* goto done */; ) {
125		if (top->link == 0) {
126			/*
127			 * top is end of the chain and none of the chain
128			 * had top->selfpc == selfpc.
129			 * so we allocate a new tostruct
130			 * and link it to the head of the chain.
131			 */
132			toindex = ++p->tos[0].link;
133			if (toindex >= p->tolimit)
134				goto overflow;
135
136			top = &p->tos[toindex];
137			top->selfpc = selfpc;
138			top->count = 1;
139			top->link = *frompcindex;
140			*frompcindex = toindex;
141			goto done;
142		}
143		/*
144		 * otherwise, check the next arc on the chain.
145		 */
146		prevtop = top;
147		top = &p->tos[top->link];
148		if (top->selfpc == selfpc) {
149			/*
150			 * there it is.
151			 * increment its count
152			 * move it to the head of the chain.
153			 */
154			top->count++;
155			toindex = prevtop->link;
156			prevtop->link = top->link;
157			top->link = *frompcindex;
158			*frompcindex = toindex;
159			goto done;
160		}
161
162	}
163done:
164#ifdef KERNEL
165	MCOUNT_EXIT;
166#else
167	p->state = GMON_PROF_ON;
168#endif
169	return;
170overflow:
171	p->state = GMON_PROF_ERROR;
172#ifdef KERNEL
173	MCOUNT_EXIT;
174#endif
175	return;
176}
177
178/*
179 * Actual definition of mcount function.  Defined in <machine/profile.h>,
180 * which is included by <sys/gmon.h>.
181 */
182MCOUNT
183