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 <unistd.h>
  35 #include <sys/param.h>
  36 #include <sys/gmon.h>
  37
  38 /* This file provides the machine-dependent definitions of the _MCOUNT_DECL
  39    and MCOUNT macros.  */
  40 #include "machine-gmon.h"
  41
  42 #include <atomic.h>
  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 {
  61         register ARCINDEX *frompcindex;
  62         register struct tostruct *top, *prevtop;
  63         register struct gmonparam *p;
  64         register ARCINDEX toindex;
  65         int i;
  66
  67         p = &_gmonparam;
  68         /*
  69          * check that we are profiling
  70          * and that we aren't recursively invoked.
  71          */
  72         if (atomic_compare_and_exchange_bool_acq (&p->state, GMON_PROF_BUSY,
  73                                                   GMON_PROF_ON))
  74           return;
  75
  76         /*
  77          * check that frompcindex is a reasonable pc value.
  78          * for example: signal catchers get called from the stack,
  79          *              not from text space.  too bad.
  80          */
  81         frompc -= p->lowpc;
  82         if (frompc > p->textsize)
  83                 goto done;
  84
  85         /* The following test used to be
  86                 if (p->log_hashfraction >= 0)
  87            But we can simplify this if we assume the profiling data
  88            is always initialized by the functions in gmon.c.  But
  89            then it is possible to avoid a runtime check and use the
  90            smae `if' as in gmon.c.  So keep these tests in sync.  */
  91         if ((HASHFRACTION & (HASHFRACTION - 1)) == 0) {
  92           /* avoid integer divide if possible: */
  93             i = frompc >> p->log_hashfraction;
  94         } else {
  95             i = frompc / (p->hashfraction * sizeof(*p->froms));
  96         }
  97         frompcindex = &p->froms[i];
  98         toindex = *frompcindex;
  99         if (toindex == 0) {
 100                 /*
 101                  *      first time traversing this arc
 102                  */
 103                 toindex = ++p->tos[0].link;
 104                 if (toindex >= p->tolimit)
 105                         /* halt further profiling */
 106                         goto overflow;
 107
 108                 *frompcindex = toindex;
 109                 top = &p->tos[toindex];
 110                 top->selfpc = selfpc;
 111                 top->count = 1;
 112                 top->link = 0;
 113                 goto done;
 114         }
 115         top = &p->tos[toindex];
 116         if (top->selfpc == selfpc) {
 117                 /*
 118                  * arc at front of chain; usual case.
 119                  */
 120                 top->count++;
 121                 goto done;
 122         }
 123         /*
 124          * have to go looking down chain for it.
 125          * top points to what we are looking at,
 126          * prevtop points to previous top.
 127          * we know it is not at the head of the chain.
 128          */
 129         for (; /* goto done */; ) {
 130                 if (top->link == 0) {
 131                         /*
 132                          * top is end of the chain and none of the chain
 133                          * had top->selfpc == selfpc.
 134                          * so we allocate a new tostruct
 135                          * and link it to the head of the chain.
 136                          */
 137                         toindex = ++p->tos[0].link;
 138                         if (toindex >= p->tolimit)
 139                                 goto overflow;
 140
 141                         top = &p->tos[toindex];
 142                         top->selfpc = selfpc;
 143                         top->count = 1;
 144                         top->link = *frompcindex;
 145                         *frompcindex = toindex;
 146                         goto done;
 147                 }
 148                 /*
 149                  * otherwise, check the next arc on the chain.
 150                  */
 151                 prevtop = top;
 152                 top = &p->tos[top->link];
 153                 if (top->selfpc == selfpc) {
 154                         /*
 155                          * there it is.
 156                          * increment its count
 157                          * move it to the head of the chain.
 158                          */
 159                         top->count++;
 160                         toindex = prevtop->link;
 161                         prevtop->link = top->link;
 162                         top->link = *frompcindex;
 163                         *frompcindex = toindex;
 164                         goto done;
 165                 }
 166
 167         }
 168 done:
 169         p->state = GMON_PROF_ON;
 170         return;
 171 overflow:
 172         p->state = GMON_PROF_ERROR;
 173         return;
 174 }
 175
 176 /*
 177  * Actual definition of mcount function.  Defined in <machine/profile.h>,
 178  * which is included by <sys/gmon.h>.
 179  */
 180 MCOUNT