FreeBSD-5.3/sys/libkern/mcount.c
/*-
* Copyright (c) 1983, 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/libkern/mcount.c,v 1.22 2004/04/07 20:46:10 imp Exp $");
#include <sys/param.h>
#include <sys/gmon.h>
#ifdef _KERNEL
#ifndef GUPROF
#include <sys/systm.h>
#endif
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
void bintr(void);
void btrap(void);
void eintr(void);
void user(void);
#endif
/*
* mcount is called on entry to each function compiled with the profiling
* switch set. _mcount(), which is declared in a machine-dependent way
* with _MCOUNT_DECL, does the actual work and is either inlined into a
* C routine or called by an assembly stub. In any case, this magic is
* taken care of by the MCOUNT definition in <machine/profile.h>.
*
* _mcount updates data structures that represent traversals of the
* program's call graph edges. frompc and selfpc are the return
* address and function address that represents the given call graph edge.
*
* Note: the original BSD code used the same variable (frompcindex) for
* both frompcindex and frompc. Any reasonable, modern compiler will
* perform this optimization.
*/
_MCOUNT_DECL(frompc, selfpc) /* _mcount; may be static, inline, etc */
register uintfptr_t frompc, selfpc;
{
#ifdef GUPROF
int delta;
#endif
register fptrdiff_t frompci;
register u_short *frompcindex;
register struct tostruct *top, *prevtop;
register struct gmonparam *p;
register long toindex;
#ifdef _KERNEL
MCOUNT_DECL(s)
#endif
p = &_gmonparam;
#ifndef GUPROF /* XXX */
/*
* check that we are profiling
* and that we aren't recursively invoked.
*/
if (p->state != GMON_PROF_ON)
return;
#endif
#ifdef _KERNEL
MCOUNT_ENTER(s);
#else
p->state = GMON_PROF_BUSY;
#endif
frompci = frompc - p->lowpc;
#ifdef _KERNEL
/*
* When we are called from an exception handler, frompci may be
* for a user address. Convert such frompci's to the index of
* user() to merge all user counts.
*/
if (frompci >= p->textsize) {
if (frompci + p->lowpc
>= (uintfptr_t)(VM_MAXUSER_ADDRESS))
goto done;
frompci = (uintfptr_t)user - p->lowpc;
if (frompci >= p->textsize)
goto done;
}
#endif
#ifdef GUPROF
if (p->state == GMON_PROF_HIRES) {
/*
* Count the time since cputime() was previously called
* against `frompc'. Compensate for overheads.
*
* cputime() sets its prev_count variable to the count when
* it is called. This in effect starts a counter for
* the next period of execution (normally from now until
* the next call to mcount() or mexitcount()). We set
* cputime_bias to compensate for our own overhead.
*
* We use the usual sampling counters since they can be
* located efficiently. 4-byte counters are usually
* necessary. gprof will add up the scattered counts
* just like it does for statistical profiling. All
* counts are signed so that underflow in the subtractions
* doesn't matter much (negative counts are normally
* compensated for by larger counts elsewhere). Underflow
* shouldn't occur, but may be caused by slightly wrong
* calibrations or from not clearing cputime_bias.
*/
delta = cputime() - cputime_bias - p->mcount_pre_overhead;
cputime_bias = p->mcount_post_overhead;
KCOUNT(p, frompci) += delta;
*p->cputime_count += p->cputime_overhead;
*p->mcount_count += p->mcount_overhead;
}
#endif /* GUPROF */
#ifdef _KERNEL
/*
* When we are called from an exception handler, frompc is faked
* to be for where the exception occurred. We've just solidified
* the count for there. Now convert frompci to the index of btrap()
* for trap handlers and bintr() for interrupt handlers to make
* exceptions appear in the call graph as calls from btrap() and
* bintr() instead of calls from all over.
*/
if ((uintfptr_t)selfpc >= (uintfptr_t)btrap
&& (uintfptr_t)selfpc < (uintfptr_t)eintr) {
if ((uintfptr_t)selfpc >= (uintfptr_t)bintr)
frompci = (uintfptr_t)bintr - p->lowpc;
else
frompci = (uintfptr_t)btrap - p->lowpc;
}
#endif
/*
* check that frompc is a reasonable pc value.
* for example: signal catchers get called from the stack,
* not from text space. too bad.
*/
if (frompci >= p->textsize)
goto done;
frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
toindex = *frompcindex;
if (toindex == 0) {
/*
* first time traversing this arc
*/
toindex = ++p->tos[0].link;
if (toindex >= p->tolimit)
/* halt further profiling */
goto overflow;
*frompcindex = toindex;
top = &p->tos[toindex];
top->selfpc = selfpc;
top->count = 1;
top->link = 0;
goto done;
}
top = &p->tos[toindex];
if (top->selfpc == selfpc) {
/*
* arc at front of chain; usual case.
*/
top->count++;
goto done;
}
/*
* have to go looking down chain for it.
* top points to what we are looking at,
* prevtop points to previous top.
* we know it is not at the head of the chain.
*/
for (; /* goto done */; ) {
if (top->link == 0) {
/*
* top is end of the chain and none of the chain
* had top->selfpc == selfpc.
* so we allocate a new tostruct
* and link it to the head of the chain.
*/
toindex = ++p->tos[0].link;
if (toindex >= p->tolimit)
goto overflow;
top = &p->tos[toindex];
top->selfpc = selfpc;
top->count = 1;
top->link = *frompcindex;
*frompcindex = toindex;
goto done;
}
/*
* otherwise, check the next arc on the chain.
*/
prevtop = top;
top = &p->tos[top->link];
if (top->selfpc == selfpc) {
/*
* there it is.
* increment its count
* move it to the head of the chain.
*/
top->count++;
toindex = prevtop->link;
prevtop->link = top->link;
top->link = *frompcindex;
*frompcindex = toindex;
goto done;
}
}
done:
#ifdef _KERNEL
MCOUNT_EXIT(s);
#else
p->state = GMON_PROF_ON;
#endif
return;
overflow:
p->state = GMON_PROF_ERROR;
#ifdef _KERNEL
MCOUNT_EXIT(s);
#endif
return;
}
/*
* Actual definition of mcount function. Defined in <machine/profile.h>,
* which is included by <sys/gmon.h>.
*/
MCOUNT
#ifdef GUPROF
void
mexitcount(selfpc)
uintfptr_t selfpc;
{
struct gmonparam *p;
uintfptr_t selfpcdiff;
p = &_gmonparam;
selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
if (selfpcdiff < p->textsize) {
int delta;
/*
* Count the time since cputime() was previously called
* against `selfpc'. Compensate for overheads.
*/
delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
cputime_bias = p->mexitcount_post_overhead;
KCOUNT(p, selfpcdiff) += delta;
*p->cputime_count += p->cputime_overhead;
*p->mexitcount_count += p->mexitcount_overhead;
}
}
void
empty_loop()
{
int i;
for (i = 0; i < CALIB_SCALE; i++)
;
}
void
nullfunc()
{
}
void
nullfunc_loop()
{
int i;
for (i = 0; i < CALIB_SCALE; i++)
nullfunc();
}
#endif /* GUPROF */