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