sys/libkern/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  * $FreeBSD: src/sys/libkern/mcount.c,v 1.16 1999/12/29 04:54:41 peter Exp $
  34  * $DragonFly: src/sys/libkern/mcount.c,v 1.7 2004/04/28 22:05:09 hmp Exp $
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/gmon.h>
  39 #ifdef _KERNEL
  40 #ifndef GUPROF
  41 #include <sys/systm.h>
  42 #endif
  43 #include <vm/vm.h>
  44 #include <vm/vm_param.h>
  45 #include <vm/pmap.h>
  46 void    bintr(void);
  47 void    btrap(void);
  48 void    eintr(void);
  49 void    user(void);
  50 #endif
  51
  52 /*
  53  * mcount is called on entry to each function compiled with the profiling
  54  * switch set.  _mcount(), which is declared in a machine-dependent way
  55  * with _MCOUNT_DECL, does the actual work and is either inlined into a
  56  * C routine or called by an assembly stub.  In any case, this magic is
  57  * taken care of by the MCOUNT definition in <machine/profile.h>.
  58  *
  59  * _mcount updates data structures that represent traversals of the
  60  * program's call graph edges.  frompc and selfpc are the return
  61  * address and function address that represents the given call graph edge.
  62  *
  63  * Note: the original BSD code used the same variable (frompcindex) for
  64  * both frompcindex and frompc.  Any reasonable, modern compiler will
  65  * perform this optimization.
  66  */
  67 /* _mcount; may be static, inline, etc */
  68 _MCOUNT_DECL(uintfptr_t frompc, uintfptr_t selfpc)
  69 {
  70 #ifdef GUPROF
  71         int delta;
  72 #endif
  73         fptrdiff_t frompci;
  74         u_short *frompcindex;
  75         struct tostruct *top, *prevtop;
  76         struct gmonparam *p;
  77         long toindex;
  78 #ifdef _KERNEL
  79         MCOUNT_DECL(s)
  80 #endif
  81
  82         p = &_gmonparam;
  83 #ifndef GUPROF                  /* XXX */
  84         /*
  85          * check that we are profiling
  86          * and that we aren't recursively invoked.
  87          */
  88         if (p->state != GMON_PROF_ON)
  89                 return;
  90 #endif
  91 #ifdef _KERNEL
  92         MCOUNT_ENTER(s);
  93 #else
  94         p->state = GMON_PROF_BUSY;
  95 #endif
  96         frompci = frompc - p->lowpc;
  97
  98 #ifdef _KERNEL
  99         /*
 100          * When we are called from an exception handler, frompci may be
 101          * for a user address.  Convert such frompci's to the index of
 102          * user() to merge all user counts.
 103          */
 104         if (frompci >= p->textsize) {
 105                 if (frompci + p->lowpc
 106                     >= (uintfptr_t)(VM_MAXUSER_ADDRESS + UPAGES * PAGE_SIZE))
 107                         goto done;
 108                 frompci = (uintfptr_t)user - p->lowpc;
 109                 if (frompci >= p->textsize)
 110                     goto done;
 111         }
 112 #endif
 113
 114 #ifdef GUPROF
 115         if (p->state == GMON_PROF_HIRES) {
 116                 /*
 117                  * Count the time since cputime() was previously called
 118                  * against `frompc'.  Compensate for overheads.
 119                  *
 120                  * cputime() sets its prev_count variable to the count when
 121                  * it is called.  This in effect starts a counter for
 122                  * the next period of execution (normally from now until
 123                  * the next call to mcount() or mexitcount()).  We set
 124                  * cputime_bias to compensate for our own overhead.
 125                  *
 126                  * We use the usual sampling counters since they can be
 127                  * located efficiently.  4-byte counters are usually
 128                  * necessary.  gprof will add up the scattered counts
 129                  * just like it does for statistical profiling.  All
 130                  * counts are signed so that underflow in the subtractions
 131                  * doesn't matter much (negative counts are normally
 132                  * compensated for by larger counts elsewhere).  Underflow
 133                  * shouldn't occur, but may be caused by slightly wrong
 134                  * calibrations or from not clearing cputime_bias.
 135                  */
 136                 delta = cputime() - cputime_bias - p->mcount_pre_overhead;
 137                 cputime_bias = p->mcount_post_overhead;
 138                 KCOUNT(p, frompci) += delta;
 139                 *p->cputime_count += p->cputime_overhead;
 140                 *p->mcount_count += p->mcount_overhead;
 141         }
 142 #endif /* GUPROF */
 143
 144 #ifdef _KERNEL
 145         /*
 146          * When we are called from an exception handler, frompc is faked
 147          * to be for where the exception occurred.  We've just solidified
 148          * the count for there.  Now convert frompci to the index of btrap()
 149          * for trap handlers and bintr() for interrupt handlers to make
 150          * exceptions appear in the call graph as calls from btrap() and
 151          * bintr() instead of calls from all over.
 152          */
 153         if ((uintfptr_t)selfpc >= (uintfptr_t)btrap
 154             && (uintfptr_t)selfpc < (uintfptr_t)eintr) {
 155                 if ((uintfptr_t)selfpc >= (uintfptr_t)bintr)
 156                         frompci = (uintfptr_t)bintr - p->lowpc;
 157                 else
 158                         frompci = (uintfptr_t)btrap - p->lowpc;
 159         }
 160 #endif
 161
 162         /*
 163          * check that frompc is a reasonable pc value.
 164          * for example: signal catchers get called from the stack,
 165          *              not from text space.  too bad.
 166          */
 167         if (frompci >= p->textsize)
 168                 goto done;
 169
 170         frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
 171         toindex = *frompcindex;
 172         if (toindex == 0) {
 173                 /*
 174                  *      first time traversing this arc
 175                  */
 176                 toindex = ++p->tos[0].link;
 177                 if (toindex >= p->tolimit)
 178                         /* halt further profiling */
 179                         goto overflow;
 180
 181                 *frompcindex = toindex;
 182                 top = &p->tos[toindex];
 183                 top->selfpc = selfpc;
 184                 top->count = 1;
 185                 top->link = 0;
 186                 goto done;
 187         }
 188         top = &p->tos[toindex];
 189         if (top->selfpc == selfpc) {
 190                 /*
 191                  * arc at front of chain; usual case.
 192                  */
 193                 top->count++;
 194                 goto done;
 195         }
 196         /*
 197          * have to go looking down chain for it.
 198          * top points to what we are looking at,
 199          * prevtop points to previous top.
 200          * we know it is not at the head of the chain.
 201          */
 202         for (; /* goto done */; ) {
 203                 if (top->link == 0) {
 204                         /*
 205                          * top is end of the chain and none of the chain
 206                          * had top->selfpc == selfpc.
 207                          * so we allocate a new tostruct
 208                          * and link it to the head of the chain.
 209                          */
 210                         toindex = ++p->tos[0].link;
 211                         if (toindex >= p->tolimit)
 212                                 goto overflow;
 213
 214                         top = &p->tos[toindex];
 215                         top->selfpc = selfpc;
 216                         top->count = 1;
 217                         top->link = *frompcindex;
 218                         *frompcindex = toindex;
 219                         goto done;
 220                 }
 221                 /*
 222                  * otherwise, check the next arc on the chain.
 223                  */
 224                 prevtop = top;
 225                 top = &p->tos[top->link];
 226                 if (top->selfpc == selfpc) {
 227                         /*
 228                          * there it is.
 229                          * increment its count
 230                          * move it to the head of the chain.
 231                          */
 232                         top->count++;
 233                         toindex = prevtop->link;
 234                         prevtop->link = top->link;
 235                         top->link = *frompcindex;
 236                         *frompcindex = toindex;
 237                         goto done;
 238                 }
 239
 240         }
 241 done:
 242 #ifdef _KERNEL
 243         MCOUNT_EXIT(s);
 244 #else
 245         p->state = GMON_PROF_ON;
 246 #endif
 247         return;
 248 overflow:
 249         p->state = GMON_PROF_ERROR;
 250 #ifdef _KERNEL
 251         MCOUNT_EXIT(s);
 252 #endif
 253         return;
 254 }
 255
 256 /*
 257  * Actual definition of mcount function.  Defined in <machine/profile.h>,
 258  * which is included by <sys/gmon.h>.
 259  */
 260 MCOUNT
 261
 262 #ifdef GUPROF
 263 void
 264 mexitcount(uintfptr_t selfpc)
 265 {
 266         struct gmonparam *p;
 267         uintfptr_t selfpcdiff;
 268
 269         p = &_gmonparam;
 270         selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
 271         if (selfpcdiff < p->textsize) {
 272                 int delta;
 273
 274                 /*
 275                  * Count the time since cputime() was previously called
 276                  * against `selfpc'.  Compensate for overheads.
 277                  */
 278                 delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
 279                 cputime_bias = p->mexitcount_post_overhead;
 280                 KCOUNT(p, selfpcdiff) += delta;
 281                 *p->cputime_count += p->cputime_overhead;
 282                 *p->mexitcount_count += p->mexitcount_overhead;
 283         }
 284 }
 285
 286 void
 287 empty_loop(void)
 288 {
 289         int i;
 290
 291         for (i = 0; i < CALIB_SCALE; i++)
 292                 ;
 293 }
 294
 295 void
 296 nullfunc(void)
 297 {
 298 }
 299
 300 void
 301 nullfunc_loop(void)
 302 {
 303         int i;
 304
 305         for (i = 0; i < CALIB_SCALE; i++)
 306                 nullfunc();
 307 }
 308 #endif /* GUPROF */