/* $Id: signal.c,v 1.20 2005/04/08 14:37:55 mikpe Exp $

 *

 * This test program illustrates how performance counter overflow

 * can be caught and sent to the process as a user-specified signal.

 *

 * Limitations:

 * - Requires a 2.4 or newer kernel with local APIC support.

 * - Requires a CPU with a local APIC (P4, P6, K8, K7).

 *

 * Copyright (C) 2001-2004  Mikael Pettersson

 */

#define __USE_GNU /* enable symbolic names for gregset_t[] indices */

#include <sys/ucontext.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "libperfctr.h"

#include "arch.h"

static struct vperfctr *vperfctr;

static struct perfctr_info info;

static void do_open(void)

{

    vperfctr = vperfctr_open();

    if( !vperfctr ) {

	perror("vperfctr_open");

	exit(1);

    }

    if( vperfctr_info(vperfctr, &info) < 0 ) {

	perror("vperfctr_info");

	exit(1);

    }

    if( !(info.cpu_features & PERFCTR_FEATURE_PCINT) )

	printf("PCINT not supported -- expect failure\n");

}

static void on_sigio(int sig, siginfo_t *si, void *puc)

{

    struct ucontext *uc;

    unsigned long pc;

    unsigned int pmc_mask;

    if( sig != SIGIO ) {

	printf("%s: unexpected signal %d\n", __FUNCTION__, sig);

	return;

    }

    if( si->si_code != SI_PMC_OVF ) {

	printf("%s: unexpected si_code #%x\n", __FUNCTION__, si->si_code);

	return;

    }

    if( (pmc_mask = si->si_pmc_ovf_mask) == 0 ) {

	printf("%s: overflow PMCs not identified\n", __FUNCTION__);

	return;

    }

    uc = puc;

    pc = ucontext_pc(uc);

    if( !vperfctr_is_running(vperfctr) ) {

	/*

	 * My theory is that this happens if a perfctr overflowed

	 * at the very instruction for the VPERFCTR_STOP call.

	 * Signal delivery is delayed until the kernel returns to

	 * user-space, at which time VPERFCTR_STOP will already

	 * have marked the vperfctr as stopped. In this case, we

	 * cannot and must not attempt to IRESUME it.

	 * This can be triggered by counting e.g. BRANCHES and setting

	 * the overflow limit ridiculously low.

	 */

	printf("%s: unexpected overflow from PMC set %#x at pc %#lx\n",

	       __FUNCTION__, pmc_mask, pc);

	return;

    }

    printf("%s: PMC overflow set %#x at pc %#lx\n", __FUNCTION__, pmc_mask, pc);

    if( vperfctr_iresume(vperfctr) < 0 ) {

	perror("vperfctr_iresume");

	abort();

    }

}

static void do_sigaction(void)

{

    struct sigaction sa;

    memset(&sa, 0, sizeof sa);

    sa.sa_sigaction = on_sigio;

    sa.sa_flags = SA_SIGINFO;

    if( sigaction(SIGIO, &sa, NULL) < 0 ) {

	perror("sigaction");

	exit(1);

    }

}

static void do_control(void)

{

    struct vperfctr_control control;

    memset(&control, 0, sizeof control);

    do_setup(&info, &control.cpu_control);

    control.si_signo = SIGIO;

    printf("Control used:\n");

    perfctr_cpu_control_print(&control.cpu_control);

    printf("\n");

    if( vperfctr_control(vperfctr, &control) < 0 ) {

	perror("vperfctr_control");

	exit(1);

    }

}

static void do_stop(void)

{

    struct sigaction sa;

    if( vperfctr_stop(vperfctr) )

	perror("vperfctr_stop");

    memset(&sa, 0, sizeof sa);

    sa.sa_handler = SIG_DFL;

    if( sigaction(SIGIO, &sa, NULL) < 0 ) {

	perror("sigaction");

	exit(1);

    }

}

#define N 150

static double v[N], w[N];

static double it;

static void do_dotprod(void)

{

    int i;

    double sum;

    sum = 0.0;

    for(i = 0; i < N; ++i)

	sum += v[i] * w[i];

    it = sum;

}

int main(void)

{

    do_sigaction();

    do_open();

    do_control();

    do_dotprod();

    do_stop();

    return 0;

}