freebsd-dev/sys/libkern/mcount.c
Pedro F. Giffuni 51369649b0 sys: further adoption of SPDX licensing ID tags.
Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
2017-11-20 19:43:44 +00:00

299 lines
8.0 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* 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.
* 3. 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("$FreeBSD$");
#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>
#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(uintfptr_t frompc, uintfptr_t selfpc) /* _mcount; may be static, inline, etc */
{
#ifdef GUPROF
int delta;
#endif
fptrdiff_t frompci;
u_short *frompcindex;
struct tostruct *top, *prevtop;
struct gmonparam *p;
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
#ifdef _KERNEL
/*
* When we are called from an exception handler, frompc may be
* a user address. Convert such frompc's to some representation
* in kernel address space.
*/
frompc = MCOUNT_FROMPC_USER(frompc);
#endif
frompci = frompc - p->lowpc;
if (frompci >= p->textsize)
goto done;
#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 an index that
* represents the kind of exception so that interruptions appear
* in the call graph as calls from those index instead of calls
* from all over.
*/
frompc = MCOUNT_FROMPC_INTR(selfpc);
if ((frompc - p->lowpc) < p->textsize)
frompci = frompc - 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(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;
}
}
#ifndef __GNUCLIKE_ASM
#error "This file uses null asms to prevent timing loops being optimized away."
#endif
void
empty_loop()
{
int i;
for (i = 0; i < CALIB_SCALE; i++)
__asm __volatile("");
}
void
nullfunc()
{
__asm __volatile("");
}
void
nullfunc_loop()
{
int i;
for (i = 0; i < CALIB_SCALE; i++)
nullfunc();
}
#endif /* GUPROF */