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 1.9 2007/01/12 22:12:50 dillon 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          * XXX doesn't work properly with vkernel
 105          */
 106         if (frompci >= p->textsize) {
 107                 if (frompci + p->lowpc
 108                     >= (uintfptr_t)(VM_MAX_USER_ADDRESS + UPAGES * PAGE_SIZE))
 109                         goto done;
 110                 frompci = (uintfptr_t)user - p->lowpc;
 111                 if (frompci >= p->textsize)
 112                     goto done;
 113         }
 114 #endif
 115
 116 #ifdef GUPROF
 117         if (p->state == GMON_PROF_HIRES) {
 118                 /*
 119                  * Count the time since cputime() was previously called
 120                  * against `frompc'.  Compensate for overheads.
 121                  *
 122                  * cputime() sets its prev_count variable to the count when
 123                  * it is called.  This in effect starts a counter for
 124                  * the next period of execution (normally from now until
 125                  * the next call to mcount() or mexitcount()).  We set
 126                  * cputime_bias to compensate for our own overhead.
 127                  *
 128                  * We use the usual sampling counters since they can be
 129                  * located efficiently.  4-byte counters are usually
 130                  * necessary.  gprof will add up the scattered counts
 131                  * just like it does for statistical profiling.  All
 132                  * counts are signed so that underflow in the subtractions
 133                  * doesn't matter much (negative counts are normally
 134                  * compensated for by larger counts elsewhere).  Underflow
 135                  * shouldn't occur, but may be caused by slightly wrong
 136                  * calibrations or from not clearing cputime_bias.
 137                  */
 138                 delta = cputime() - cputime_bias - p->mcount_pre_overhead;
 139                 cputime_bias = p->mcount_post_overhead;
 140                 KCOUNT(p, frompci) += delta;
 141                 *p->cputime_count += p->cputime_overhead;
 142                 *p->mcount_count += p->mcount_overhead;
 143         }
 144 #endif /* GUPROF */
 145
 146 #ifdef _KERNEL
 147         /*
 148          * When we are called from an exception handler, frompc is faked
 149          * to be for where the exception occurred.  We've just solidified
 150          * the count for there.  Now convert frompci to the index of btrap()
 151          * for trap handlers and bintr() for interrupt handlers to make
 152          * exceptions appear in the call graph as calls from btrap() and
 153          * bintr() instead of calls from all over.
 154          */
 155         if ((uintfptr_t)selfpc >= (uintfptr_t)btrap
 156             && (uintfptr_t)selfpc < (uintfptr_t)eintr) {
 157                 if ((uintfptr_t)selfpc >= (uintfptr_t)bintr)
 158                         frompci = (uintfptr_t)bintr - p->lowpc;
 159                 else
 160                         frompci = (uintfptr_t)btrap - p->lowpc;
 161         }
 162 #endif
 163
 164         /*
 165          * check that frompc is a reasonable pc value.
 166          * for example: signal catchers get called from the stack,
 167          *              not from text space.  too bad.
 168          */
 169         if (frompci >= p->textsize)
 170                 goto done;
 171
 172         frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
 173         toindex = *frompcindex;
 174         if (toindex == 0) {
 175                 /*
 176                  *      first time traversing this arc
 177                  */
 178                 toindex = ++p->tos[0].link;
 179                 if (toindex >= p->tolimit)
 180                         /* halt further profiling */
 181                         goto overflow;
 182
 183                 *frompcindex = toindex;
 184                 top = &p->tos[toindex];
 185                 top->selfpc = selfpc;
 186                 top->count = 1;
 187                 top->link = 0;
 188                 goto done;
 189         }
 190         top = &p->tos[toindex];
 191         if (top->selfpc == selfpc) {
 192                 /*
 193                  * arc at front of chain; usual case.
 194                  */
 195                 top->count++;
 196                 goto done;
 197         }
 198         /*
 199          * have to go looking down chain for it.
 200          * top points to what we are looking at,
 201          * prevtop points to previous top.
 202          * we know it is not at the head of the chain.
 203          */
 204         for (; /* goto done */; ) {
 205                 if (top->link == 0) {
 206                         /*
 207                          * top is end of the chain and none of the chain
 208                          * had top->selfpc == selfpc.
 209                          * so we allocate a new tostruct
 210                          * and link it to the head of the chain.
 211                          */
 212                         toindex = ++p->tos[0].link;
 213                         if (toindex >= p->tolimit)
 214                                 goto overflow;
 215
 216                         top = &p->tos[toindex];
 217                         top->selfpc = selfpc;
 218                         top->count = 1;
 219                         top->link = *frompcindex;
 220                         *frompcindex = toindex;
 221                         goto done;
 222                 }
 223                 /*
 224                  * otherwise, check the next arc on the chain.
 225                  */
 226                 prevtop = top;
 227                 top = &p->tos[top->link];
 228                 if (top->selfpc == selfpc) {
 229                         /*
 230                          * there it is.
 231                          * increment its count
 232                          * move it to the head of the chain.
 233                          */
 234                         top->count++;
 235                         toindex = prevtop->link;
 236                         prevtop->link = top->link;
 237                         top->link = *frompcindex;
 238                         *frompcindex = toindex;
 239                         goto done;
 240                 }
 241
 242         }
 243 done:
 244 #ifdef _KERNEL
 245         MCOUNT_EXIT(s);
 246 #else
 247         p->state = GMON_PROF_ON;
 248 #endif
 249         return;
 250 overflow:
 251         p->state = GMON_PROF_ERROR;
 252 #ifdef _KERNEL
 253         MCOUNT_EXIT(s);
 254 #endif
 255         return;
 256 }
 257
 258 /*
 259  * Actual definition of mcount function.  Defined in <machine/profile.h>,
 260  * which is included by <sys/gmon.h>.
 261  */
 262 MCOUNT
 263
 264 #ifdef GUPROF
 265 void
 266 mexitcount(uintfptr_t selfpc)
 267 {
 268         struct gmonparam *p;
 269         uintfptr_t selfpcdiff;
 270
 271         p = &_gmonparam;
 272         selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
 273         if (selfpcdiff < p->textsize) {
 274                 int delta;
 275
 276                 /*
 277                  * Count the time since cputime() was previously called
 278                  * against `selfpc'.  Compensate for overheads.
 279                  */
 280                 delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
 281                 cputime_bias = p->mexitcount_post_overhead;
 282                 KCOUNT(p, selfpcdiff) += delta;
 283                 *p->cputime_count += p->cputime_overhead;
 284                 *p->mexitcount_count += p->mexitcount_overhead;
 285         }
 286 }
 287
 288 void
 289 empty_loop(void)
 290 {
 291         int i;
 292
 293         for (i = 0; i < CALIB_SCALE; i++)
 294                 ;
 295 }
 296
 297 void
 298 nullfunc(void)
 299 {
 300 }
 301
 302 void
 303 nullfunc_loop(void)
 304 {
 305         int i;
 306
 307         for (i = 0; i < CALIB_SCALE; i++)
 308                 nullfunc();
 309 }
 310 #endif /* GUPROF */