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30 #if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)
31 static char sccsid
[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
35 #include <sys/param.h>
38 /* This file provides the machine-dependent definitions of the _MCOUNT_DECL
40 #include "machine-gmon.h"
42 #include <atomicity.h>
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>.
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.
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.
59 _MCOUNT_DECL(frompc
, selfpc
) /* _mcount; may be static, inline, etc */
61 register ARCINDEX
*frompcindex
;
62 register struct tostruct
*top
, *prevtop
;
63 register struct gmonparam
*p
;
64 register ARCINDEX toindex
;
69 * check that we are profiling
70 * and that we aren't recursively invoked.
72 if (! compare_and_swap (&p
->state
, GMON_PROF_ON
, GMON_PROF_BUSY
))
76 * check that frompcindex is a reasonable pc value.
77 * for example: signal catchers get called from the stack,
78 * not from text space. too bad.
81 if (frompc
> p
->textsize
)
84 /* The following test used to be
85 if (p->log_hashfraction >= 0)
86 But we can simplify this if we assume the profiling data
87 is always initialized by the functions in gmon.c. But
88 then it is possible to avoid a runtime check and use the
89 smae `if' as in gmon.c. So keep these tests in sync. */
90 if ((HASHFRACTION
& (HASHFRACTION
- 1)) == 0) {
91 /* avoid integer divide if possible: */
92 i
= frompc
>> p
->log_hashfraction
;
94 i
= frompc
/ (p
->hashfraction
* sizeof(*p
->froms
));
96 frompcindex
= &p
->froms
[i
];
97 toindex
= *frompcindex
;
100 * first time traversing this arc
102 toindex
= ++p
->tos
[0].link
;
103 if (toindex
>= p
->tolimit
)
104 /* halt further profiling */
107 *frompcindex
= toindex
;
108 top
= &p
->tos
[toindex
];
109 top
->selfpc
= selfpc
;
114 top
= &p
->tos
[toindex
];
115 if (top
->selfpc
== selfpc
) {
117 * arc at front of chain; usual case.
123 * have to go looking down chain for it.
124 * top points to what we are looking at,
125 * prevtop points to previous top.
126 * we know it is not at the head of the chain.
128 for (; /* goto done */; ) {
129 if (top
->link
== 0) {
131 * top is end of the chain and none of the chain
132 * had top->selfpc == selfpc.
133 * so we allocate a new tostruct
134 * and link it to the head of the chain.
136 toindex
= ++p
->tos
[0].link
;
137 if (toindex
>= p
->tolimit
)
140 top
= &p
->tos
[toindex
];
141 top
->selfpc
= selfpc
;
143 top
->link
= *frompcindex
;
144 *frompcindex
= toindex
;
148 * otherwise, check the next arc on the chain.
151 top
= &p
->tos
[top
->link
];
152 if (top
->selfpc
== selfpc
) {
155 * increment its count
156 * move it to the head of the chain.
159 toindex
= prevtop
->link
;
160 prevtop
->link
= top
->link
;
161 top
->link
= *frompcindex
;
162 *frompcindex
= toindex
;
168 p
->state
= GMON_PROF_ON
;
171 p
->state
= GMON_PROF_ERROR
;
176 * Actual definition of mcount function. Defined in <machine/profile.h>,
177 * which is included by <sys/gmon.h>.