bp_account.c

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/*
 * Powerpc needs __SANE_USERSPACE_TYPES__ before <linux/types.h> to select
 * 'int-ll64.h' and avoid compile warnings when printing __u64 with %llu.
 */
#define __SANE_USERSPACE_TYPES__

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <time.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/mman.h>
#include <linux/compiler.h>
#include <linux/hw_breakpoint.h>
#include <sys/ioctl.h>

#include "tests.h"
#include "debug.h"
#include "perf.h"
#include "cloexec.h"

volatile long the_var;

static noinline int test_function(void)
{
    return 0;
}

static int __event(bool is_x, void *addr, struct perf_event_attr *attr)
{
    int fd;

    memset(attr, 0, sizeof(struct perf_event_attr));
    attr->type = PERF_TYPE_BREAKPOINT;
    attr->size = sizeof(struct perf_event_attr);

    attr->config = 0;
    attr->bp_type = is_x ? HW_BREAKPOINT_X : HW_BREAKPOINT_W;
    attr->bp_addr = (unsigned long) addr;
    attr->bp_len = sizeof(long);

    attr->sample_period = 1;
    attr->sample_type = PERF_SAMPLE_IP;

    attr->exclude_kernel = 1;
    attr->exclude_hv = 1;

    fd = sys_perf_event_open(attr, -1, 0, -1,
                 perf_event_open_cloexec_flag());
    if (fd < 0) {
        pr_debug("failed opening event %llx\n", attr->config);
        return TEST_FAIL;
    }

    return fd;
}

static int wp_event(void *addr, struct perf_event_attr *attr)
{
    return __event(false, addr, attr);
}

static int bp_event(void *addr, struct perf_event_attr *attr)
{
    return __event(true, addr, attr);
}

static int bp_accounting(int wp_cnt, int share)
{
    struct perf_event_attr attr, attr_mod, attr_new;
    int i, fd[wp_cnt], fd_wp, ret;

    for (i = 0; i < wp_cnt; i++) {
        fd[i] = wp_event((void *)&the_var, &attr);
        TEST_ASSERT_VAL("failed to create wp\n", fd[i] != -1);
        pr_debug("wp %d created\n", i);
    }

    attr_mod = attr;
    attr_mod.bp_type = HW_BREAKPOINT_X;
    attr_mod.bp_addr = (unsigned long) test_function;

    ret = ioctl(fd[0], PERF_EVENT_IOC_MODIFY_ATTRIBUTES, &attr_mod);
    TEST_ASSERT_VAL("failed to modify wp\n", ret == 0);

    pr_debug("wp 0 modified to bp\n");

    if (!share) {
        fd_wp = wp_event((void *)&the_var, &attr_new);
        TEST_ASSERT_VAL("failed to create max wp\n", fd_wp != -1);
        pr_debug("wp max created\n");
    }

    for (i = 0; i < wp_cnt; i++)
        close(fd[i]);

    return 0;
}

static int detect_cnt(bool is_x)
{
    struct perf_event_attr attr;
    void *addr = is_x ? (void *)test_function : (void *)&the_var;
    int fd[100], cnt = 0, i;

    while (1) {
        if (cnt == 100) {
            pr_debug("way too many debug registers, fix the test\n");
            return 0;
        }
        fd[cnt] = __event(is_x, addr, &attr);

        if (fd[cnt] < 0)
            break;
        cnt++;
    }

    for (i = 0; i < cnt; i++)
        close(fd[i]);

    return cnt;
}

static int detect_ioctl(void)
{
    struct perf_event_attr attr;
    int fd, ret = 1;

    fd = wp_event((void *) &the_var, &attr);
    if (fd > 0) {
        ret = ioctl(fd, PERF_EVENT_IOC_MODIFY_ATTRIBUTES, &attr);
        close(fd);
    }

    return ret ? 0 : 1;
}

static int detect_share(int wp_cnt, int bp_cnt)
{
    struct perf_event_attr attr;
    int i, fd[wp_cnt + bp_cnt], ret;

    for (i = 0; i < wp_cnt; i++) {
        fd[i] = wp_event((void *)&the_var, &attr);
        TEST_ASSERT_VAL("failed to create wp\n", fd[i] != -1);
    }

    for (; i < (bp_cnt + wp_cnt); i++) {
        fd[i] = bp_event((void *)test_function, &attr);
        if (fd[i] == -1)
            break;
    }

    ret = i != (bp_cnt + wp_cnt);

    while (i--)
        close(fd[i]);

    return ret;
}

/*
 * This test does following:
 *   - detects the number of watch/break-points,
 *     skip test if any is missing
 *   - detects PERF_EVENT_IOC_MODIFY_ATTRIBUTES ioctl,
 *     skip test if it's missing
 *   - detects if watchpoints and breakpoints share
 *     same slots
 *   - create all possible watchpoints on cpu 0
 *   - change one of it to breakpoint
 *   - in case wp and bp do not share slots,
 *     we create another watchpoint to ensure
 *     the slot accounting is correct
 */
int test__bp_accounting(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    int has_ioctl = detect_ioctl();
    int wp_cnt = detect_cnt(false);
    int bp_cnt = detect_cnt(true);
    int share  = detect_share(wp_cnt, bp_cnt);

    pr_debug("watchpoints count %d, breakpoints count %d, has_ioctl %d, share %d\n",
         wp_cnt, bp_cnt, has_ioctl, share);

    if (!wp_cnt || !bp_cnt || !has_ioctl)
        return TEST_SKIP;

    return bp_accounting(wp_cnt, share);
}