gmon/mcount.c

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