/*-
 * 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.
 *
 * @(#)mcount.c 8.1 (Berkeley) 6/4/93
 * $FreeBSD: src/lib/libc/gmon/mcount.c,v 1.20 2004/10/16 06:32:43 obrien Exp $
 */

#include <sys/param.h>
#include <sys/gmon.h>

/*
 * 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; may be static, inline, etc */
_MCOUNT_DECL(u_long frompc, u_long selfpc)
{
        u_long frompci;
        u_short *frompcindex;
        struct tostruct *top, *prevtop;
        struct gmonparam *p;
        long toindex;

        p = &_gmonparam;
        /*
         * check that we are profiling
         * and that we aren't recursively invoked.
         */
        if (p->state != GMON_PROF_ON)
                return;
        p->state = GMON_PROF_BUSY;      /* XXX */
        frompci = frompc - p->lowpc;

        /*
         * 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:
        p->state = GMON_PROF_ON;        /* XXX */
        return;
overflow:
        p->state = GMON_PROF_ERROR;     /* XXX */
        return;
}

/*
 * Actual definition of mcount function.  Defined in <machine/profile.h>,
 * which is included by <sys/gmon.h>.
 */
MCOUNT