mcount.c revision 330897
1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1983, 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 4. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32#if !defined(_KERNEL) && defined(LIBC_SCCS) && !defined(lint) 33static char sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93"; 34#endif 35#include <sys/cdefs.h> 36__FBSDID("$FreeBSD: stable/11/lib/libc/gmon/mcount.c 330897 2018-03-14 03:19:51Z eadler $"); 37 38#include <sys/param.h> 39#include <sys/gmon.h> 40#ifdef _KERNEL 41#include <sys/systm.h> 42#include <vm/vm.h> 43#include <vm/vm_param.h> 44#include <vm/pmap.h> 45void bintr(void); 46void btrap(void); 47void eintr(void); 48void user(void); 49#endif 50#include <machine/atomic.h> 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 u_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 if (!atomic_cmpset_acq_int(&p->state, GMON_PROF_ON, GMON_PROF_BUSY)) 95 return; 96#endif 97 frompci = frompc - p->lowpc; 98 99#ifdef _KERNEL 100 /* 101 * When we are called from an exception handler, frompci may be 102 * for a user address. Convert such frompci's to the index of 103 * user() to merge all user counts. 104 */ 105 if (frompci >= p->textsize) { 106 if (frompci + p->lowpc 107 >= (uintfptr_t)(VM_MAXUSER_ADDRESS + UPAGES * PAGE_SIZE)) 108 goto done; 109 frompci = (uintfptr_t)user - p->lowpc; 110 if (frompci >= p->textsize) 111 goto done; 112 } 113#endif 114 115#ifdef GUPROF 116 if (p->state != GMON_PROF_HIRES) 117 goto skip_guprof_stuff; 118 /* 119 * Look at the clock and add the count of clock cycles since the 120 * clock was last looked at to a counter for frompc. This 121 * solidifies the count for the function containing frompc and 122 * effectively starts another clock for the current function. 123 * The count for the new clock will be solidified when another 124 * function call is made or the function returns. 125 * 126 * We use the usual sampling counters since they can be located 127 * efficiently. 4-byte counters are usually necessary. 128 * 129 * There are many complications for subtracting the profiling 130 * overheads from the counts for normal functions and adding 131 * them to the counts for mcount(), mexitcount() and cputime(). 132 * We attempt to handle fractional cycles, but the overheads 133 * are usually underestimated because they are calibrated for 134 * a simpler than usual setup. 135 */ 136 delta = cputime() - p->mcount_overhead; 137 p->cputime_overhead_resid += p->cputime_overhead_frac; 138 p->mcount_overhead_resid += p->mcount_overhead_frac; 139 if ((int)delta < 0) 140 *p->mcount_count += delta + p->mcount_overhead 141 - p->cputime_overhead; 142 else if (delta != 0) { 143 if (p->cputime_overhead_resid >= CALIB_SCALE) { 144 p->cputime_overhead_resid -= CALIB_SCALE; 145 ++*p->cputime_count; 146 --delta; 147 } 148 if (delta != 0) { 149 if (p->mcount_overhead_resid >= CALIB_SCALE) { 150 p->mcount_overhead_resid -= CALIB_SCALE; 151 ++*p->mcount_count; 152 --delta; 153 } 154 KCOUNT(p, frompci) += delta; 155 } 156 *p->mcount_count += p->mcount_overhead_sub; 157 } 158 *p->cputime_count += p->cputime_overhead; 159skip_guprof_stuff: 160#endif /* GUPROF */ 161 162#ifdef _KERNEL 163 /* 164 * When we are called from an exception handler, frompc is faked 165 * to be for where the exception occurred. We've just solidified 166 * the count for there. Now convert frompci to the index of btrap() 167 * for trap handlers and bintr() for interrupt handlers to make 168 * exceptions appear in the call graph as calls from btrap() and 169 * bintr() instead of calls from all over. 170 */ 171 if ((uintfptr_t)selfpc >= (uintfptr_t)btrap 172 && (uintfptr_t)selfpc < (uintfptr_t)eintr) { 173 if ((uintfptr_t)selfpc >= (uintfptr_t)bintr) 174 frompci = (uintfptr_t)bintr - p->lowpc; 175 else 176 frompci = (uintfptr_t)btrap - p->lowpc; 177 } 178#endif 179 180 /* 181 * check that frompc is a reasonable pc value. 182 * for example: signal catchers get called from the stack, 183 * not from text space. too bad. 184 */ 185 if (frompci >= p->textsize) 186 goto done; 187 188 frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))]; 189 toindex = *frompcindex; 190 if (toindex == 0) { 191 /* 192 * first time traversing this arc 193 */ 194 toindex = ++p->tos[0].link; 195 if (toindex >= p->tolimit) 196 /* halt further profiling */ 197 goto overflow; 198 199 *frompcindex = toindex; 200 top = &p->tos[toindex]; 201 top->selfpc = selfpc; 202 top->count = 1; 203 top->link = 0; 204 goto done; 205 } 206 top = &p->tos[toindex]; 207 if (top->selfpc == selfpc) { 208 /* 209 * arc at front of chain; usual case. 210 */ 211 top->count++; 212 goto done; 213 } 214 /* 215 * have to go looking down chain for it. 216 * top points to what we are looking at, 217 * prevtop points to previous top. 218 * we know it is not at the head of the chain. 219 */ 220 for (; /* goto done */; ) { 221 if (top->link == 0) { 222 /* 223 * top is end of the chain and none of the chain 224 * had top->selfpc == selfpc. 225 * so we allocate a new tostruct 226 * and link it to the head of the chain. 227 */ 228 toindex = ++p->tos[0].link; 229 if (toindex >= p->tolimit) 230 goto overflow; 231 232 top = &p->tos[toindex]; 233 top->selfpc = selfpc; 234 top->count = 1; 235 top->link = *frompcindex; 236 *frompcindex = toindex; 237 goto done; 238 } 239 /* 240 * otherwise, check the next arc on the chain. 241 */ 242 prevtop = top; 243 top = &p->tos[top->link]; 244 if (top->selfpc == selfpc) { 245 /* 246 * there it is. 247 * increment its count 248 * move it to the head of the chain. 249 */ 250 top->count++; 251 toindex = prevtop->link; 252 prevtop->link = top->link; 253 top->link = *frompcindex; 254 *frompcindex = toindex; 255 goto done; 256 } 257 258 } 259done: 260#ifdef _KERNEL 261 MCOUNT_EXIT(s); 262#else 263 atomic_store_rel_int(&p->state, GMON_PROF_ON); 264#endif 265 return; 266overflow: 267 atomic_store_rel_int(&p->state, GMON_PROF_ERROR); 268#ifdef _KERNEL 269 MCOUNT_EXIT(s); 270#endif 271 return; 272} 273 274/* 275 * Actual definition of mcount function. Defined in <machine/profile.h>, 276 * which is included by <sys/gmon.h>. 277 */ 278MCOUNT 279 280#ifdef GUPROF 281void 282mexitcount(selfpc) 283 uintfptr_t selfpc; 284{ 285 struct gmonparam *p; 286 uintfptr_t selfpcdiff; 287 288 p = &_gmonparam; 289 selfpcdiff = selfpc - (uintfptr_t)p->lowpc; 290 if (selfpcdiff < p->textsize) { 291 u_int delta; 292 293 /* 294 * Solidify the count for the current function. 295 */ 296 delta = cputime() - p->mexitcount_overhead; 297 p->cputime_overhead_resid += p->cputime_overhead_frac; 298 p->mexitcount_overhead_resid += p->mexitcount_overhead_frac; 299 if ((int)delta < 0) 300 *p->mexitcount_count += delta + p->mexitcount_overhead 301 - p->cputime_overhead; 302 else if (delta != 0) { 303 if (p->cputime_overhead_resid >= CALIB_SCALE) { 304 p->cputime_overhead_resid -= CALIB_SCALE; 305 ++*p->cputime_count; 306 --delta; 307 } 308 if (delta != 0) { 309 if (p->mexitcount_overhead_resid 310 >= CALIB_SCALE) { 311 p->mexitcount_overhead_resid 312 -= CALIB_SCALE; 313 ++*p->mexitcount_count; 314 --delta; 315 } 316 KCOUNT(p, selfpcdiff) += delta; 317 } 318 *p->mexitcount_count += p->mexitcount_overhead_sub; 319 } 320 *p->cputime_count += p->cputime_overhead; 321 } 322} 323#endif /* GUPROF */ 324