mmtimer.c

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/*
 * See the dyninst/COPYRIGHT file for copyright information.
 * 
 * We provide the Paradyn Tools (below described as "Paradyn")
 * on an AS IS basis, and do not warrant its validity or performance.
 * We reserve the right to update, modify, or discontinue this
 * software at any time.  We shall have no obligation to supply such
 * updates or modifications or any other form of support to you.
 * 
 * By your use of Paradyn, you understand and agree that we (or any
 * other person or entity with proprietary rights in Paradyn) are
 * under no obligation to provide either maintenance services,
 * update services, notices of latent defects, or correction of
 * defects for Paradyn.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
#include <sn/mmtimer.h> /* MMTIMER_* */

/* getpid() */
#include <sys/types.h>
#include <unistd.h>              

#include <stdio.h> /* fprintf() */
#include <sys/ioctl.h> /* for ioctl() */
#include <sys/mman.h> /* for mmap() */

/* The mmtimer, once initialized by a call to isMMTimerAvail(),
   is always (mmdev_clicks_per_tick * (*mmdev_timer_addr)). */
static unsigned long mmdev_clicks_per_tick = 0;
static volatile unsigned long * mmdev_timer_addr = NULL;

/* The defined interface in common/h/timing.h is too clumsy, so duplicate code. */
double getLocalCyclesPerSecond() {
    FILE * cpuinfo = fopen( "/proc/cpuinfo", "r" );
    if( cpuinfo == NULL ) { return 0; }
    
    double MHz = 0.0;
    /* Scan /proc/cpuinfo until we find something; assume all CPUs the same. */
    while( ! feof( cpuinfo ) ) {
        char buffer[ 256 ];
        char * result = fgets( buffer, 255, cpuinfo );
        if( result != NULL ) {
            int status = sscanf( result, "cpu MHz : %lf", & MHz );
            if( status == 1 ) { 
                fclose( cpuinfo );
                return ( MHz * 1000000.0 );
                }
            }
        } /* end scanning loop */
        
    fclose( cpuinfo );
    return 0;
    } /* end getLocalCyclesPerSecond() */

int isMMTimerAvail() {
    int fd = 0;
    unsigned long femtosecondsPerTick = 0;
    int mmTimerOffset = 0;
    
    /* Don't do anything twice. */
    if( mmdev_clicks_per_tick != 0 || mmdev_timer_addr != 0 ) { return 1; }
    
    /* Attempt to setup the mmtimer. */
    if( ( fd = open( MMTIMER_FULLNAME, O_RDONLY ) ) == -1 ) {
        return 0;
        }
    if( ( mmTimerOffset = ioctl( fd, MMTIMER_GETOFFSET, 0 ) ) == -ENOSYS ) {
        close( fd );
        return 0;
        }
     if( ( mmdev_timer_addr = (volatile unsigned long int *)mmap( 0, getpagesize(), PROT_READ, MAP_SHARED, fd, 0 ) ) == NULL ) {
        close( fd );
        return 0;
        }

    mmdev_timer_addr += mmTimerOffset;
    ioctl( fd, MMTIMER_GETRES, & femtosecondsPerTick );
    mmdev_clicks_per_tick = (unsigned long)((getLocalCyclesPerSecond() * 1.0e-15) * femtosecondsPerTick);
     
    assert( mmdev_clicks_per_tick != 0 );
    
    ///* DEBUG */ fprintf( stderr,  "%d: %lf MHz, "
    //                              "microseconds/tick = %lf, "
    //                              "clicks_per_tick = %lu\n",
    //                              getpid(),
    //                              getLocalCyclesPerSecond() / 1.0e6,
    //                              femtosecondsPerTick / 1.0e9,
    //                              mmdev_clicks_per_tick );

    close( fd );
    return 1;
    } /* end isMMtimerAvail() */