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34 #if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)
35 static char sccsid
[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
38 #include <sys/param.h>
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>.
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.
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.
56 _MCOUNT_DECL(frompc
, selfpc
) /* _mcount; may be static, inline, etc */
57 register u_long frompc
, selfpc
;
59 register u_short
*frompcindex
;
60 register struct tostruct
*top
, *prevtop
;
61 register struct gmonparam
*p
;
62 register long toindex
;
69 * check that we are profiling
70 * and that we aren't recursively invoked.
72 if (p
->state
!= GMON_PROF_ON
)
77 p
->state
= GMON_PROF_BUSY
;
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.
85 if (frompc
> p
->textsize
)
88 frompcindex
= &p
->froms
[frompc
/ (p
->hashfraction
* sizeof(*p
->froms
))];
89 toindex
= *frompcindex
;
92 * first time traversing this arc
94 toindex
= ++p
->tos
[0].link
;
95 if (toindex
>= p
->tolimit
)
96 /* halt further profiling */
99 *frompcindex
= toindex
;
100 top
= &p
->tos
[toindex
];
101 top
->selfpc
= selfpc
;
106 top
= &p
->tos
[toindex
];
107 if (top
->selfpc
== selfpc
) {
109 * arc at front of chain; usual case.
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.
120 for (; /* goto done */; ) {
121 if (top
->link
== 0) {
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.
128 toindex
= ++p
->tos
[0].link
;
129 if (toindex
>= p
->tolimit
)
132 top
= &p
->tos
[toindex
];
133 top
->selfpc
= selfpc
;
135 top
->link
= *frompcindex
;
136 *frompcindex
= toindex
;
140 * otherwise, check the next arc on the chain.
143 top
= &p
->tos
[top
->link
];
144 if (top
->selfpc
== selfpc
) {
147 * increment its count
148 * move it to the head of the chain.
151 toindex
= prevtop
->link
;
152 prevtop
->link
= top
->link
;
153 top
->link
= *frompcindex
;
154 *frompcindex
= toindex
;
163 p
->state
= GMON_PROF_ON
;
167 p
->state
= GMON_PROF_ERROR
;
175 * Actual definition of mcount function. Defined in <machine/profile.h>,
176 * which is included by <sys/gmon.h>.