The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_prof.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1982, 1986, 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  * 3. 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  *      @(#)subr_prof.c 8.3 (Berkeley) 9/23/93
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD$");
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/sysproto.h>
   40 #include <sys/kernel.h>
   41 #include <sys/lock.h>
   42 #include <sys/mutex.h>
   43 #include <sys/proc.h>
   44 #include <sys/resourcevar.h>
   45 #include <sys/sysctl.h>
   46 
   47 #include <machine/cpu.h>
   48 
   49 /*
   50  * Profiling system call.
   51  *
   52  * The scale factor is a fixed point number with 16 bits of fraction, so that
   53  * 1.0 is represented as 0x10000.  A scale factor of 0 turns off profiling.
   54  */
   55 #ifndef _SYS_SYSPROTO_H_
   56 struct profil_args {
   57         caddr_t samples;
   58         size_t  size;
   59         size_t  offset;
   60         u_int   scale;
   61 };
   62 #endif
   63 /* ARGSUSED */
   64 int
   65 sys_profil(struct thread *td, struct profil_args *uap)
   66 {
   67         struct uprof *upp;
   68         struct proc *p;
   69 
   70         if (uap->scale > (1 << 16))
   71                 return (EINVAL);
   72 
   73         p = td->td_proc;
   74         if (uap->scale == 0) {
   75                 PROC_LOCK(p);
   76                 stopprofclock(p);
   77                 PROC_UNLOCK(p);
   78                 return (0);
   79         }
   80         PROC_LOCK(p);
   81         upp = &td->td_proc->p_stats->p_prof;
   82         PROC_PROFLOCK(p);
   83         upp->pr_off = uap->offset;
   84         upp->pr_scale = uap->scale;
   85         upp->pr_base = uap->samples;
   86         upp->pr_size = uap->size;
   87         PROC_PROFUNLOCK(p);
   88         startprofclock(p);
   89         PROC_UNLOCK(p);
   90 
   91         return (0);
   92 }
   93 
   94 /*
   95  * Scale is a fixed-point number with the binary point 16 bits
   96  * into the value, and is <= 1.0.  pc is at most 32 bits, so the
   97  * intermediate result is at most 48 bits.
   98  */
   99 #define PC_TO_INDEX(pc, prof) \
  100         ((int)(((u_quad_t)((pc) - (prof)->pr_off) * \
  101             (u_quad_t)((prof)->pr_scale)) >> 16) & ~1)
  102 
  103 /*
  104  * Collect user-level profiling statistics; called on a profiling tick,
  105  * when a process is running in user-mode.  This routine may be called
  106  * from an interrupt context.  We perform the update with an AST
  107  * that will vector us to trap() with a context in which copyin and
  108  * copyout will work.  Trap will then call addupc_task().
  109  *
  110  * Note that we may (rarely) not get around to the AST soon enough, and
  111  * lose profile ticks when the next tick overwrites this one, but in this
  112  * case the system is overloaded and the profile is probably already
  113  * inaccurate.
  114  */
  115 void
  116 addupc_intr(struct thread *td, uintfptr_t pc, u_int ticks)
  117 {
  118         struct uprof *prof;
  119 
  120         if (ticks == 0)
  121                 return;
  122         prof = &td->td_proc->p_stats->p_prof;
  123         PROC_PROFLOCK(td->td_proc);
  124         if (pc < prof->pr_off || PC_TO_INDEX(pc, prof) >= prof->pr_size) {
  125                 PROC_PROFUNLOCK(td->td_proc);
  126                 return;                 /* out of range; ignore */
  127         }
  128 
  129         PROC_PROFUNLOCK(td->td_proc);
  130         td->td_profil_addr = pc;
  131         td->td_profil_ticks = ticks;
  132         td->td_pflags |= TDP_OWEUPC;
  133         ast_sched(td, TDA_OWEUPC);
  134 }
  135 
  136 /*
  137  * Actually update the profiling statistics.  If the update fails, we
  138  * simply turn off profiling.
  139  */
  140 void
  141 addupc_task(struct thread *td, uintfptr_t pc, u_int ticks)
  142 {
  143         struct proc *p = td->td_proc; 
  144         struct uprof *prof;
  145         caddr_t addr;
  146         u_int i;
  147         u_short v;
  148         int stop = 0;
  149 
  150         if (ticks == 0)
  151                 return;
  152 
  153         PROC_LOCK(p);
  154         if (!(p->p_flag & P_PROFIL)) {
  155                 PROC_UNLOCK(p);
  156                 return;
  157         }
  158         p->p_profthreads++;
  159         prof = &p->p_stats->p_prof;
  160         PROC_PROFLOCK(p);
  161         if (pc < prof->pr_off ||
  162             (i = PC_TO_INDEX(pc, prof)) >= prof->pr_size) {
  163                 PROC_PROFUNLOCK(p);
  164                 goto out;
  165         }
  166 
  167         addr = prof->pr_base + i;
  168         PROC_PROFUNLOCK(p);
  169         PROC_UNLOCK(p);
  170         if (copyin(addr, &v, sizeof(v)) == 0) {
  171                 v += ticks;
  172                 if (copyout(&v, addr, sizeof(v)) == 0) {
  173                         PROC_LOCK(p);
  174                         goto out;
  175                 }
  176         }
  177         stop = 1;
  178         PROC_LOCK(p);
  179 
  180 out:
  181         if (--p->p_profthreads == 0) {
  182                 if (p->p_flag & P_STOPPROF) {
  183                         wakeup(&p->p_profthreads);
  184                         p->p_flag &= ~P_STOPPROF;
  185                         stop = 0;
  186                 }
  187         }
  188         if (stop)
  189                 stopprofclock(p);
  190         PROC_UNLOCK(p);
  191 }

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