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 /*
  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>.
  47  *
  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.
  51  *
  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.
  55  */
  56 #if 0
  57 _MCOUNT_DECL(frompc, selfpc)    /* _mcount; may be static, inline, etc */
  58         register u_long frompc, selfpc;
  59 #endif
  60
  61 /* GCC version 2 gives us a perfect magical function to get
  62    just the information we need:
  63      void *__builtin_return_address (unsigned int N)
  64    returns the return address of the frame N frames up.  */
  65
  66 #if __GNUC__ < 2
  67  #error "This file uses __builtin_return_address, a GCC 2 extension."
  68 #endif
  69
  70 #include <sysdep.h>
  71 #ifndef NO_UNDERSCORES
  72 /* The asm symbols for C functions are `_function'.
  73    The canonical name for the counter function is `mcount', no _.  */
  74 void _mcount (void) asm ("mcount");
  75 #endif
  76
  77 void
  78 _mcount (void)
  79 {
  80         register u_long selfpc = (u_long) __builtin_return_address (0);
  81         register u_long frompc = (u_long) __builtin_return_address (1);
  82
  83         register u_short *frompcindex;
  84         register struct tostruct *top, *prevtop;
  85         register struct gmonparam *p;
  86         register long toindex;
  87 #ifdef KERNEL
  88         register int s;
  89 #endif
  90
  91         p = &_gmonparam;
  92         /*
  93          * check that we are profiling
  94          * and that we aren't recursively invoked.
  95          */
  96         if (p->state != GMON_PROF_ON)
  97                 return;
  98 #ifdef KERNEL
  99         MCOUNT_ENTER;
 100 #else
 101         p->state = GMON_PROF_BUSY;
 102 #endif
 103         /*
 104          * check that frompcindex is a reasonable pc value.
 105          * for example: signal catchers get called from the stack,
 106          *              not from text space.  too bad.
 107          */
 108         frompc -= p->lowpc;
 109         if (frompc > p->textsize)
 110                 goto done;
 111
 112         frompcindex = &p->froms[frompc / (p->hashfraction * sizeof(*p->froms))];
 113         toindex = *frompcindex;
 114         if (toindex == 0) {
 115                 /*
 116                  *      first time traversing this arc
 117                  */
 118                 toindex = ++p->tos[0].link;
 119                 if (toindex >= p->tolimit)
 120                         /* halt further profiling */
 121                         goto overflow;
 122
 123                 *frompcindex = toindex;
 124                 top = &p->tos[toindex];
 125                 top->selfpc = selfpc;
 126                 top->count = 1;
 127                 top->link = 0;
 128                 goto done;
 129         }
 130         top = &p->tos[toindex];
 131         if (top->selfpc == selfpc) {
 132                 /*
 133                  * arc at front of chain; usual case.
 134                  */
 135                 top->count++;
 136                 goto done;
 137         }
 138         /*
 139          * have to go looking down chain for it.
 140          * top points to what we are looking at,
 141          * prevtop points to previous top.
 142          * we know it is not at the head of the chain.
 143          */
 144         for (; /* goto done */; ) {
 145                 if (top->link == 0) {
 146                         /*
 147                          * top is end of the chain and none of the chain
 148                          * had top->selfpc == selfpc.
 149                          * so we allocate a new tostruct
 150                          * and link it to the head of the chain.
 151                          */
 152                         toindex = ++p->tos[0].link;
 153                         if (toindex >= p->tolimit)
 154                                 goto overflow;
 155
 156                         top = &p->tos[toindex];
 157                         top->selfpc = selfpc;
 158                         top->count = 1;
 159                         top->link = *frompcindex;
 160                         *frompcindex = toindex;
 161                         goto done;
 162                 }
 163                 /*
 164                  * otherwise, check the next arc on the chain.
 165                  */
 166                 prevtop = top;
 167                 top = &p->tos[top->link];
 168                 if (top->selfpc == selfpc) {
 169                         /*
 170                          * there it is.
 171                          * increment its count
 172                          * move it to the head of the chain.
 173                          */
 174                         top->count++;
 175                         toindex = prevtop->link;
 176                         prevtop->link = top->link;
 177                         top->link = *frompcindex;
 178                         *frompcindex = toindex;
 179                         goto done;
 180                 }
 181
 182         }
 183 done:
 184 #ifdef KERNEL
 185         MCOUNT_EXIT;
 186 #else
 187         p->state = GMON_PROF_ON;
 188 #endif
 189         return;
 190 overflow:
 191         p->state = GMON_PROF_ERROR;
 192 #ifdef KERNEL
 193         MCOUNT_EXIT;
 194 #endif
 195         return;
 196 }
 197
 198 #if 0                           /* Obsolete with __builtin_return_address.  */
 199 /*
 200  * Actual definition of mcount function.  Defined in <machine/profile.h>,
 201  * which is included by <sys/gmon.h>.
 202  */
 203 MCOUNT
 204 #endif