oprofile_perf.c

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/*
 * Copyright 2010 ARM Ltd.
 * Copyright 2012 Advanced Micro Devices, Inc., Robert Richter
 *
 * Perf-events backend for OProfile.
 */
#include <linux/perf_event.h>
#include <linux/platform_device.h>
#include <linux/oprofile.h>
#include <linux/slab.h>

/*
 * Per performance monitor configuration as set via oprofilefs.
 */
struct op_counter_config {
    unsigned long count;
    unsigned long enabled;
    unsigned long event;
    unsigned long unit_mask;
    unsigned long kernel;
    unsigned long user;
    struct perf_event_attr attr;
};

static int oprofile_perf_enabled;
static DEFINE_MUTEX(oprofile_perf_mutex);

static struct op_counter_config *counter_config;
static DEFINE_PER_CPU(struct perf_event **, perf_events);
static int num_counters;

/*
 * Overflow callback for oprofile.
 */
static void op_overflow_handler(struct perf_event *event,
            struct perf_sample_data *data, struct pt_regs *regs)
{
    int id;
    u32 cpu = smp_processor_id();

    for (id = 0; id < num_counters; ++id)
        if (per_cpu(perf_events, cpu)[id] == event)
            break;

    if (id != num_counters)
        oprofile_add_sample(regs, id);
    else
        pr_warning("oprofile: ignoring spurious overflow "
                "on cpu %u\n", cpu);
}

/*
 * Called by oprofile_perf_setup to create perf attributes to mirror the oprofile
 * settings in counter_config. Attributes are created as `pinned' events and
 * so are permanently scheduled on the PMU.
 */
static void op_perf_setup(void)
{
    int i;
    u32 size = sizeof(struct perf_event_attr);
    struct perf_event_attr *attr;

    for (i = 0; i < num_counters; ++i) {
        attr = &counter_config[i].attr;
        memset(attr, 0, size);
        attr->type      = PERF_TYPE_RAW;
        attr->size      = size;
        attr->config        = counter_config[i].event;
        attr->sample_period = counter_config[i].count;
        attr->pinned        = 1;
    }
}

static int op_create_counter(int cpu, int event)
{
    struct perf_event *pevent;

    if (!counter_config[event].enabled || per_cpu(perf_events, cpu)[event])
        return 0;

    pevent = perf_event_create_kernel_counter(&counter_config[event].attr,
                          cpu, NULL,
                          op_overflow_handler, NULL);

    if (IS_ERR(pevent))
        return PTR_ERR(pevent);

    if (pevent->state != PERF_EVENT_STATE_ACTIVE) {
        perf_event_release_kernel(pevent);
        pr_warning("oprofile: failed to enable event %d "
                "on CPU %d\n", event, cpu);
        return -EBUSY;
    }

    per_cpu(perf_events, cpu)[event] = pevent;

    return 0;
}

static void op_destroy_counter(int cpu, int event)
{
    struct perf_event *pevent = per_cpu(perf_events, cpu)[event];

    if (pevent) {
        perf_event_release_kernel(pevent);
        per_cpu(perf_events, cpu)[event] = NULL;
    }
}

/*
 * Called by oprofile_perf_start to create active perf events based on the
 * perviously configured attributes.
 */
static int op_perf_start(void)
{
    int cpu, event, ret = 0;

    for_each_online_cpu(cpu) {
        for (event = 0; event < num_counters; ++event) {
            ret = op_create_counter(cpu, event);
            if (ret)
                return ret;
        }
    }

    return ret;
}

/*
 * Called by oprofile_perf_stop at the end of a profiling run.
 */
static void op_perf_stop(void)
{
    int cpu, event;

    for_each_online_cpu(cpu)
        for (event = 0; event < num_counters; ++event)
            op_destroy_counter(cpu, event);
}

static int oprofile_perf_create_files(struct super_block *sb, struct dentry *root)
{
    unsigned int i;

    for (i = 0; i < num_counters; i++) {
        struct dentry *dir;
        char buf[4];

        snprintf(buf, sizeof buf, "%d", i);
        dir = oprofilefs_mkdir(sb, root, buf);
        oprofilefs_create_ulong(sb, dir, "enabled", &counter_config[i].enabled);
        oprofilefs_create_ulong(sb, dir, "event", &counter_config[i].event);
        oprofilefs_create_ulong(sb, dir, "count", &counter_config[i].count);
        oprofilefs_create_ulong(sb, dir, "unit_mask", &counter_config[i].unit_mask);
        oprofilefs_create_ulong(sb, dir, "kernel", &counter_config[i].kernel);
        oprofilefs_create_ulong(sb, dir, "user", &counter_config[i].user);
    }

    return 0;
}

static int oprofile_perf_setup(void)
{
    raw_spin_lock(&oprofilefs_lock);
    op_perf_setup();
    raw_spin_unlock(&oprofilefs_lock);
    return 0;
}

static int oprofile_perf_start(void)
{
    int ret = -EBUSY;

    mutex_lock(&oprofile_perf_mutex);
    if (!oprofile_perf_enabled) {
        ret = 0;
        op_perf_start();
        oprofile_perf_enabled = 1;
    }
    mutex_unlock(&oprofile_perf_mutex);
    return ret;
}

static void oprofile_perf_stop(void)
{
    mutex_lock(&oprofile_perf_mutex);
    if (oprofile_perf_enabled)
        op_perf_stop();
    oprofile_perf_enabled = 0;
    mutex_unlock(&oprofile_perf_mutex);
}

#ifdef CONFIG_PM

static int oprofile_perf_suspend(struct platform_device *dev, pm_message_t state)
{
    mutex_lock(&oprofile_perf_mutex);
    if (oprofile_perf_enabled)
        op_perf_stop();
    mutex_unlock(&oprofile_perf_mutex);
    return 0;
}

static int oprofile_perf_resume(struct platform_device *dev)
{
    mutex_lock(&oprofile_perf_mutex);
    if (oprofile_perf_enabled && op_perf_start())
        oprofile_perf_enabled = 0;
    mutex_unlock(&oprofile_perf_mutex);
    return 0;
}

static struct platform_driver oprofile_driver = {
    .driver     = {
        .name       = "oprofile-perf",
    },
    .resume     = oprofile_perf_resume,
    .suspend    = oprofile_perf_suspend,
};

static struct platform_device *oprofile_pdev;

static int __init init_driverfs(void)
{
    int ret;

    ret = platform_driver_register(&oprofile_driver);
    if (ret)
        return ret;

    oprofile_pdev = platform_device_register_simple(
                oprofile_driver.driver.name, 0, NULL, 0);
    if (IS_ERR(oprofile_pdev)) {
        ret = PTR_ERR(oprofile_pdev);
        platform_driver_unregister(&oprofile_driver);
    }

    return ret;
}

static void exit_driverfs(void)
{
    platform_device_unregister(oprofile_pdev);
    platform_driver_unregister(&oprofile_driver);
}

#else

static inline int  init_driverfs(void) { return 0; }
static inline void exit_driverfs(void) { }

#endif /* CONFIG_PM */

void oprofile_perf_exit(void)
{
    int cpu, id;
    struct perf_event *event;

    for_each_possible_cpu(cpu) {
        for (id = 0; id < num_counters; ++id) {
            event = per_cpu(perf_events, cpu)[id];
            if (event)
                perf_event_release_kernel(event);
        }

        kfree(per_cpu(perf_events, cpu));
    }

    kfree(counter_config);
    exit_driverfs();
}

int __init oprofile_perf_init(struct oprofile_operations *ops)
{
    int cpu, ret = 0;

    ret = init_driverfs();
    if (ret)
        return ret;

    num_counters = perf_num_counters();
    if (num_counters <= 0) {
        pr_info("oprofile: no performance counters\n");
        ret = -ENODEV;
        goto out;
    }

    counter_config = kcalloc(num_counters,
            sizeof(struct op_counter_config), GFP_KERNEL);

    if (!counter_config) {
        pr_info("oprofile: failed to allocate %d "
                "counters\n", num_counters);
        ret = -ENOMEM;
        num_counters = 0;
        goto out;
    }

    for_each_possible_cpu(cpu) {
        per_cpu(perf_events, cpu) = kcalloc(num_counters,
                sizeof(struct perf_event *), GFP_KERNEL);
        if (!per_cpu(perf_events, cpu)) {
            pr_info("oprofile: failed to allocate %d perf events "
                    "for cpu %d\n", num_counters, cpu);
            ret = -ENOMEM;
            goto out;
        }
    }

    ops->create_files   = oprofile_perf_create_files;
    ops->setup      = oprofile_perf_setup;
    ops->start      = oprofile_perf_start;
    ops->stop       = oprofile_perf_stop;
    ops->shutdown       = oprofile_perf_stop;
    ops->cpu_type       = op_name_from_perf_id();

    if (!ops->cpu_type)
        ret = -ENODEV;
    else
        pr_info("oprofile: using %s\n", ops->cpu_type);

out:
    if (ret)
        oprofile_perf_exit();

    return ret;
}