Merge branch 'master' into export-slabh

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / arch / x86 / kernel / cpu / perf_event.c

/*
 * Performance events x86 architecture code
 *
 *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
 *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2009 Jaswinder Singh Rajput
 *  Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
 *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
 *  Copyright (C) 2009 Intel Corporation, <markus.t.metzger@intel.com>
 *  Copyright (C) 2009 Google, Inc., Stephane Eranian
 *
 *  For licencing details see kernel-base/COPYING
 */

#include <linux/perf_event.h>
#include <linux/capability.h>
#include <linux/notifier.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/kdebug.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/cpu.h>
#include <linux/bitops.h>

#include <asm/apic.h>
#include <asm/stacktrace.h>
#include <asm/nmi.h>
#include <asm/compat.h>

static u64 perf_event_mask __read_mostly;

/* The maximal number of PEBS events: */
#define MAX_PEBS_EVENTS 4

/* The size of a BTS record in bytes: */
#define BTS_RECORD_SIZE         24

/* The size of a per-cpu BTS buffer in bytes: */
#define BTS_BUFFER_SIZE         (BTS_RECORD_SIZE * 2048)

/* The BTS overflow threshold in bytes from the end of the buffer: */
#define BTS_OVFL_TH             (BTS_RECORD_SIZE * 128)


/*
 * Bits in the debugctlmsr controlling branch tracing.
 */
#define X86_DEBUGCTL_TR                 (1 << 6)
#define X86_DEBUGCTL_BTS                (1 << 7)
#define X86_DEBUGCTL_BTINT              (1 << 8)
#define X86_DEBUGCTL_BTS_OFF_OS         (1 << 9)
#define X86_DEBUGCTL_BTS_OFF_USR        (1 << 10)

/*
 * A debug store configuration.
 *
 * We only support architectures that use 64bit fields.
 */
struct debug_store {
        u64     bts_buffer_base;
        u64     bts_index;
        u64     bts_absolute_maximum;
        u64     bts_interrupt_threshold;
        u64     pebs_buffer_base;
        u64     pebs_index;
        u64     pebs_absolute_maximum;
        u64     pebs_interrupt_threshold;
        u64     pebs_event_reset[MAX_PEBS_EVENTS];
};

struct event_constraint {
        union {
                unsigned long   idxmsk[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
                u64             idxmsk64;
        };
        u64     code;
        u64     cmask;
        int     weight;
};

struct amd_nb {
        int nb_id;  /* NorthBridge id */
        int refcnt; /* reference count */
        struct perf_event *owners[X86_PMC_IDX_MAX];
        struct event_constraint event_constraints[X86_PMC_IDX_MAX];
};

struct cpu_hw_events {
        struct perf_event       *events[X86_PMC_IDX_MAX]; /* in counter order */
        unsigned long           active_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        unsigned long           interrupts;
        int                     enabled;
        struct debug_store      *ds;

        int                     n_events;
        int                     n_added;
        int                     assign[X86_PMC_IDX_MAX]; /* event to counter assignment */
        u64                     tags[X86_PMC_IDX_MAX];
        struct perf_event       *event_list[X86_PMC_IDX_MAX]; /* in enabled order */
        struct amd_nb           *amd_nb;
};

#define __EVENT_CONSTRAINT(c, n, m, w) {\
        { .idxmsk64 = (n) },            \
        .code = (c),                    \
        .cmask = (m),                   \
        .weight = (w),                  \
}

#define EVENT_CONSTRAINT(c, n, m)       \
        __EVENT_CONSTRAINT(c, n, m, HWEIGHT(n))

#define INTEL_EVENT_CONSTRAINT(c, n)    \
        EVENT_CONSTRAINT(c, n, INTEL_ARCH_EVTSEL_MASK)

#define FIXED_EVENT_CONSTRAINT(c, n)    \
        EVENT_CONSTRAINT(c, (1ULL << (32+n)), INTEL_ARCH_FIXED_MASK)

#define EVENT_CONSTRAINT_END            \
        EVENT_CONSTRAINT(0, 0, 0)

#define for_each_event_constraint(e, c) \
        for ((e) = (c); (e)->cmask; (e)++)

/*
 * struct x86_pmu - generic x86 pmu
 */
struct x86_pmu {
        const char      *name;
        int             version;
        int             (*handle_irq)(struct pt_regs *);
        void            (*disable_all)(void);
        void            (*enable_all)(void);
        void            (*enable)(struct perf_event *);
        void            (*disable)(struct perf_event *);
        unsigned        eventsel;
        unsigned        perfctr;
        u64             (*event_map)(int);
        u64             (*raw_event)(u64);
        int             max_events;
        int             num_events;
        int             num_events_fixed;
        int             event_bits;
        u64             event_mask;
        int             apic;
        u64             max_period;
        u64             intel_ctrl;
        void            (*enable_bts)(u64 config);
        void            (*disable_bts)(void);

        struct event_constraint *
                        (*get_event_constraints)(struct cpu_hw_events *cpuc,
                                                 struct perf_event *event);

        void            (*put_event_constraints)(struct cpu_hw_events *cpuc,
                                                 struct perf_event *event);
        struct event_constraint *event_constraints;

        int             (*cpu_prepare)(int cpu);
        void            (*cpu_starting)(int cpu);
        void            (*cpu_dying)(int cpu);
        void            (*cpu_dead)(int cpu);
};

static struct x86_pmu x86_pmu __read_mostly;

static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
        .enabled = 1,
};

static int x86_perf_event_set_period(struct perf_event *event);

/*
 * Generalized hw caching related hw_event table, filled
 * in on a per model basis. A value of 0 means
 * 'not supported', -1 means 'hw_event makes no sense on
 * this CPU', any other value means the raw hw_event
 * ID.
 */

#define C(x) PERF_COUNT_HW_CACHE_##x

static u64 __read_mostly hw_cache_event_ids
                                [PERF_COUNT_HW_CACHE_MAX]
                                [PERF_COUNT_HW_CACHE_OP_MAX]
                                [PERF_COUNT_HW_CACHE_RESULT_MAX];

/*
 * Propagate event elapsed time into the generic event.
 * Can only be executed on the CPU where the event is active.
 * Returns the delta events processed.
 */
static u64
x86_perf_event_update(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        int shift = 64 - x86_pmu.event_bits;
        u64 prev_raw_count, new_raw_count;
        int idx = hwc->idx;
        s64 delta;

        if (idx == X86_PMC_IDX_FIXED_BTS)
                return 0;

        /*
         * Careful: an NMI might modify the previous event value.
         *
         * Our tactic to handle this is to first atomically read and
         * exchange a new raw count - then add that new-prev delta
         * count to the generic event atomically:
         */
again:
        prev_raw_count = atomic64_read(&hwc->prev_count);
        rdmsrl(hwc->event_base + idx, new_raw_count);

        if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
                                        new_raw_count) != prev_raw_count)
                goto again;

        /*
         * Now we have the new raw value and have updated the prev
         * timestamp already. We can now calculate the elapsed delta
         * (event-)time and add that to the generic event.
         *
         * Careful, not all hw sign-extends above the physical width
         * of the count.
         */
        delta = (new_raw_count << shift) - (prev_raw_count << shift);
        delta >>= shift;

        atomic64_add(delta, &event->count);
        atomic64_sub(delta, &hwc->period_left);

        return new_raw_count;
}

static atomic_t active_events;
static DEFINE_MUTEX(pmc_reserve_mutex);

static bool reserve_pmc_hardware(void)
{
#ifdef CONFIG_X86_LOCAL_APIC
        int i;

        if (nmi_watchdog == NMI_LOCAL_APIC)
                disable_lapic_nmi_watchdog();

        for (i = 0; i < x86_pmu.num_events; i++) {
                if (!reserve_perfctr_nmi(x86_pmu.perfctr + i))
                        goto perfctr_fail;
        }

        for (i = 0; i < x86_pmu.num_events; i++) {
                if (!reserve_evntsel_nmi(x86_pmu.eventsel + i))
                        goto eventsel_fail;
        }
#endif

        return true;

#ifdef CONFIG_X86_LOCAL_APIC
eventsel_fail:
        for (i--; i >= 0; i--)
                release_evntsel_nmi(x86_pmu.eventsel + i);

        i = x86_pmu.num_events;

perfctr_fail:
        for (i--; i >= 0; i--)
                release_perfctr_nmi(x86_pmu.perfctr + i);

        if (nmi_watchdog == NMI_LOCAL_APIC)
                enable_lapic_nmi_watchdog();

        return false;
#endif
}

static void release_pmc_hardware(void)
{
#ifdef CONFIG_X86_LOCAL_APIC
        int i;

        for (i = 0; i < x86_pmu.num_events; i++) {
                release_perfctr_nmi(x86_pmu.perfctr + i);
                release_evntsel_nmi(x86_pmu.eventsel + i);
        }

        if (nmi_watchdog == NMI_LOCAL_APIC)
                enable_lapic_nmi_watchdog();
#endif
}

static inline bool bts_available(void)
{
        return x86_pmu.enable_bts != NULL;
}

static void init_debug_store_on_cpu(int cpu)
{
        struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds;

        if (!ds)
                return;

        wrmsr_on_cpu(cpu, MSR_IA32_DS_AREA,
                     (u32)((u64)(unsigned long)ds),
                     (u32)((u64)(unsigned long)ds >> 32));
}

static void fini_debug_store_on_cpu(int cpu)
{
        if (!per_cpu(cpu_hw_events, cpu).ds)
                return;

        wrmsr_on_cpu(cpu, MSR_IA32_DS_AREA, 0, 0);
}

static void release_bts_hardware(void)
{
        int cpu;

        if (!bts_available())
                return;

        get_online_cpus();

        for_each_online_cpu(cpu)
                fini_debug_store_on_cpu(cpu);

        for_each_possible_cpu(cpu) {
                struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds;

                if (!ds)
                        continue;

                per_cpu(cpu_hw_events, cpu).ds = NULL;

                kfree((void *)(unsigned long)ds->bts_buffer_base);
                kfree(ds);
        }

        put_online_cpus();
}

static int reserve_bts_hardware(void)
{
        int cpu, err = 0;

        if (!bts_available())
                return 0;

        get_online_cpus();

        for_each_possible_cpu(cpu) {
                struct debug_store *ds;
                void *buffer;

                err = -ENOMEM;
                buffer = kzalloc(BTS_BUFFER_SIZE, GFP_KERNEL);
                if (unlikely(!buffer))
                        break;

                ds = kzalloc(sizeof(*ds), GFP_KERNEL);
                if (unlikely(!ds)) {
                        kfree(buffer);
                        break;
                }

                ds->bts_buffer_base = (u64)(unsigned long)buffer;
                ds->bts_index = ds->bts_buffer_base;
                ds->bts_absolute_maximum =
                        ds->bts_buffer_base + BTS_BUFFER_SIZE;
                ds->bts_interrupt_threshold =
                        ds->bts_absolute_maximum - BTS_OVFL_TH;

                per_cpu(cpu_hw_events, cpu).ds = ds;
                err = 0;
        }

        if (err)
                release_bts_hardware();
        else {
                for_each_online_cpu(cpu)
                        init_debug_store_on_cpu(cpu);
        }

        put_online_cpus();

        return err;
}

static void hw_perf_event_destroy(struct perf_event *event)
{
        if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
                release_pmc_hardware();
                release_bts_hardware();
                mutex_unlock(&pmc_reserve_mutex);
        }
}

static inline int x86_pmu_initialized(void)
{
        return x86_pmu.handle_irq != NULL;
}

static inline int
set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event_attr *attr)
{
        unsigned int cache_type, cache_op, cache_result;
        u64 config, val;

        config = attr->config;

        cache_type = (config >>  0) & 0xff;
        if (cache_type >= PERF_COUNT_HW_CACHE_MAX)
                return -EINVAL;

        cache_op = (config >>  8) & 0xff;
        if (cache_op >= PERF_COUNT_HW_CACHE_OP_MAX)
                return -EINVAL;

        cache_result = (config >> 16) & 0xff;
        if (cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
                return -EINVAL;

        val = hw_cache_event_ids[cache_type][cache_op][cache_result];

        if (val == 0)
                return -ENOENT;

        if (val == -1)
                return -EINVAL;

        hwc->config |= val;

        return 0;
}

/*
 * Setup the hardware configuration for a given attr_type
 */
static int __hw_perf_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        u64 config;
        int err;

        if (!x86_pmu_initialized())
                return -ENODEV;

        err = 0;
        if (!atomic_inc_not_zero(&active_events)) {
                mutex_lock(&pmc_reserve_mutex);
                if (atomic_read(&active_events) == 0) {
                        if (!reserve_pmc_hardware())
                                err = -EBUSY;
                        else
                                err = reserve_bts_hardware();
                }
                if (!err)
                        atomic_inc(&active_events);
                mutex_unlock(&pmc_reserve_mutex);
        }
        if (err)
                return err;

        event->destroy = hw_perf_event_destroy;

        /*
         * Generate PMC IRQs:
         * (keep 'enabled' bit clear for now)
         */
        hwc->config = ARCH_PERFMON_EVENTSEL_INT;

        hwc->idx = -1;
        hwc->last_cpu = -1;
        hwc->last_tag = ~0ULL;

        /*
         * Count user and OS events unless requested not to.
         */
        if (!attr->exclude_user)
                hwc->config |= ARCH_PERFMON_EVENTSEL_USR;
        if (!attr->exclude_kernel)
                hwc->config |= ARCH_PERFMON_EVENTSEL_OS;

        if (!hwc->sample_period) {
                hwc->sample_period = x86_pmu.max_period;
                hwc->last_period = hwc->sample_period;
                atomic64_set(&hwc->period_left, hwc->sample_period);
        } else {
                /*
                 * If we have a PMU initialized but no APIC
                 * interrupts, we cannot sample hardware
                 * events (user-space has to fall back and
                 * sample via a hrtimer based software event):
                 */
                if (!x86_pmu.apic)
                        return -EOPNOTSUPP;
        }

        /*
         * Raw hw_event type provide the config in the hw_event structure
         */
        if (attr->type == PERF_TYPE_RAW) {
                hwc->config |= x86_pmu.raw_event(attr->config);
                if ((hwc->config & ARCH_PERFMON_EVENTSEL_ANY) &&
                    perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
                        return -EACCES;
                return 0;
        }

        if (attr->type == PERF_TYPE_HW_CACHE)
                return set_ext_hw_attr(hwc, attr);

        if (attr->config >= x86_pmu.max_events)
                return -EINVAL;

        /*
         * The generic map:
         */
        config = x86_pmu.event_map(attr->config);

        if (config == 0)
                return -ENOENT;

        if (config == -1LL)
                return -EINVAL;

        /*
         * Branch tracing:
         */
        if ((attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) &&
            (hwc->sample_period == 1)) {
                /* BTS is not supported by this architecture. */
                if (!bts_available())
                        return -EOPNOTSUPP;

                /* BTS is currently only allowed for user-mode. */
                if (hwc->config & ARCH_PERFMON_EVENTSEL_OS)
                        return -EOPNOTSUPP;
        }

        hwc->config |= config;

        return 0;
}

static void x86_pmu_disable_all(void)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx;

        for (idx = 0; idx < x86_pmu.num_events; idx++) {
                u64 val;

                if (!test_bit(idx, cpuc->active_mask))
                        continue;
                rdmsrl(x86_pmu.eventsel + idx, val);
                if (!(val & ARCH_PERFMON_EVENTSEL_ENABLE))
                        continue;
                val &= ~ARCH_PERFMON_EVENTSEL_ENABLE;
                wrmsrl(x86_pmu.eventsel + idx, val);
        }
}

void hw_perf_disable(void)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);

        if (!x86_pmu_initialized())
                return;

        if (!cpuc->enabled)
                return;

        cpuc->n_added = 0;
        cpuc->enabled = 0;
        barrier();

        x86_pmu.disable_all();
}

static void x86_pmu_enable_all(void)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx;

        for (idx = 0; idx < x86_pmu.num_events; idx++) {
                struct perf_event *event = cpuc->events[idx];
                u64 val;

                if (!test_bit(idx, cpuc->active_mask))
                        continue;

                val = event->hw.config;
                val |= ARCH_PERFMON_EVENTSEL_ENABLE;
                wrmsrl(x86_pmu.eventsel + idx, val);
        }
}

static const struct pmu pmu;

static inline int is_x86_event(struct perf_event *event)
{
        return event->pmu == &pmu;
}

static int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
{
        struct event_constraint *c, *constraints[X86_PMC_IDX_MAX];
        unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        int i, j, w, wmax, num = 0;
        struct hw_perf_event *hwc;

        bitmap_zero(used_mask, X86_PMC_IDX_MAX);

        for (i = 0; i < n; i++) {
                c = x86_pmu.get_event_constraints(cpuc, cpuc->event_list[i]);
                constraints[i] = c;
        }

        /*
         * fastpath, try to reuse previous register
         */
        for (i = 0; i < n; i++) {
                hwc = &cpuc->event_list[i]->hw;
                c = constraints[i];

                /* never assigned */
                if (hwc->idx == -1)
                        break;

                /* constraint still honored */
                if (!test_bit(hwc->idx, c->idxmsk))
                        break;

                /* not already used */
                if (test_bit(hwc->idx, used_mask))
                        break;

                __set_bit(hwc->idx, used_mask);
                if (assign)
                        assign[i] = hwc->idx;
        }
        if (i == n)
                goto done;

        /*
         * begin slow path
         */

        bitmap_zero(used_mask, X86_PMC_IDX_MAX);

        /*
         * weight = number of possible counters
         *
         * 1    = most constrained, only works on one counter
         * wmax = least constrained, works on any counter
         *
         * assign events to counters starting with most
         * constrained events.
         */
        wmax = x86_pmu.num_events;

        /*
         * when fixed event counters are present,
         * wmax is incremented by 1 to account
         * for one more choice
         */
        if (x86_pmu.num_events_fixed)
                wmax++;

        for (w = 1, num = n; num && w <= wmax; w++) {
                /* for each event */
                for (i = 0; num && i < n; i++) {
                        c = constraints[i];
                        hwc = &cpuc->event_list[i]->hw;

                        if (c->weight != w)
                                continue;

                        for_each_set_bit(j, c->idxmsk, X86_PMC_IDX_MAX) {
                                if (!test_bit(j, used_mask))
                                        break;
                        }

                        if (j == X86_PMC_IDX_MAX)
                                break;

                        __set_bit(j, used_mask);

                        if (assign)
                                assign[i] = j;
                        num--;
                }
        }
done:
        /*
         * scheduling failed or is just a simulation,
         * free resources if necessary
         */
        if (!assign || num) {
                for (i = 0; i < n; i++) {
                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, cpuc->event_list[i]);
                }
        }
        return num ? -ENOSPC : 0;
}

/*
 * dogrp: true if must collect siblings events (group)
 * returns total number of events and error code
 */
static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader, bool dogrp)
{
        struct perf_event *event;
        int n, max_count;

        max_count = x86_pmu.num_events + x86_pmu.num_events_fixed;

        /* current number of events already accepted */
        n = cpuc->n_events;

        if (is_x86_event(leader)) {
                if (n >= max_count)
                        return -ENOSPC;
                cpuc->event_list[n] = leader;
                n++;
        }
        if (!dogrp)
                return n;

        list_for_each_entry(event, &leader->sibling_list, group_entry) {
                if (!is_x86_event(event) ||
                    event->state <= PERF_EVENT_STATE_OFF)
                        continue;

                if (n >= max_count)
                        return -ENOSPC;

                cpuc->event_list[n] = event;
                n++;
        }
        return n;
}

static inline void x86_assign_hw_event(struct perf_event *event,
                                struct cpu_hw_events *cpuc, int i)
{
        struct hw_perf_event *hwc = &event->hw;

        hwc->idx = cpuc->assign[i];
        hwc->last_cpu = smp_processor_id();
        hwc->last_tag = ++cpuc->tags[i];

        if (hwc->idx == X86_PMC_IDX_FIXED_BTS) {
                hwc->config_base = 0;
                hwc->event_base = 0;
        } else if (hwc->idx >= X86_PMC_IDX_FIXED) {
                hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
                /*
                 * We set it so that event_base + idx in wrmsr/rdmsr maps to
                 * MSR_ARCH_PERFMON_FIXED_CTR0 ... CTR2:
                 */
                hwc->event_base =
                        MSR_ARCH_PERFMON_FIXED_CTR0 - X86_PMC_IDX_FIXED;
        } else {
                hwc->config_base = x86_pmu.eventsel;
                hwc->event_base  = x86_pmu.perfctr;
        }
}

static inline int match_prev_assignment(struct hw_perf_event *hwc,
                                        struct cpu_hw_events *cpuc,
                                        int i)
{
        return hwc->idx == cpuc->assign[i] &&
                hwc->last_cpu == smp_processor_id() &&
                hwc->last_tag == cpuc->tags[i];
}

static int x86_pmu_start(struct perf_event *event);
static void x86_pmu_stop(struct perf_event *event);

void hw_perf_enable(void)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct perf_event *event;
        struct hw_perf_event *hwc;
        int i;

        if (!x86_pmu_initialized())
                return;

        if (cpuc->enabled)
                return;

        if (cpuc->n_added) {
                int n_running = cpuc->n_events - cpuc->n_added;
                /*
                 * apply assignment obtained either from
                 * hw_perf_group_sched_in() or x86_pmu_enable()
                 *
                 * step1: save events moving to new counters
                 * step2: reprogram moved events into new counters
                 */
                for (i = 0; i < n_running; i++) {
                        event = cpuc->event_list[i];
                        hwc = &event->hw;

                        /*
                         * we can avoid reprogramming counter if:
                         * - assigned same counter as last time
                         * - running on same CPU as last time
                         * - no other event has used the counter since
                         */
                        if (hwc->idx == -1 ||
                            match_prev_assignment(hwc, cpuc, i))
                                continue;

                        x86_pmu_stop(event);
                }

                for (i = 0; i < cpuc->n_events; i++) {
                        event = cpuc->event_list[i];
                        hwc = &event->hw;

                        if (!match_prev_assignment(hwc, cpuc, i))
                                x86_assign_hw_event(event, cpuc, i);
                        else if (i < n_running)
                                continue;

                        x86_pmu_start(event);
                }
                cpuc->n_added = 0;
                perf_events_lapic_init();
        }

        cpuc->enabled = 1;
        barrier();

        x86_pmu.enable_all();
}

static inline void __x86_pmu_enable_event(struct hw_perf_event *hwc)
{
        (void)checking_wrmsrl(hwc->config_base + hwc->idx,
                              hwc->config | ARCH_PERFMON_EVENTSEL_ENABLE);
}

static inline void x86_pmu_disable_event(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        (void)checking_wrmsrl(hwc->config_base + hwc->idx, hwc->config);
}

static DEFINE_PER_CPU(u64 [X86_PMC_IDX_MAX], pmc_prev_left);

/*
 * Set the next IRQ period, based on the hwc->period_left value.
 * To be called with the event disabled in hw:
 */
static int
x86_perf_event_set_period(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        s64 left = atomic64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int err, ret = 0, idx = hwc->idx;

        if (idx == X86_PMC_IDX_FIXED_BTS)
                return 0;

        /*
         * If we are way outside a reasonable range then just skip forward:
         */
        if (unlikely(left <= -period)) {
                left = period;
                atomic64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }

        if (unlikely(left <= 0)) {
                left += period;
                atomic64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }
        /*
         * Quirk: certain CPUs dont like it if just 1 hw_event is left:
         */
        if (unlikely(left < 2))
                left = 2;

        if (left > x86_pmu.max_period)
                left = x86_pmu.max_period;

        per_cpu(pmc_prev_left[idx], smp_processor_id()) = left;

        /*
         * The hw event starts counting from this event offset,
         * mark it to be able to extra future deltas:
         */
        atomic64_set(&hwc->prev_count, (u64)-left);

        err = checking_wrmsrl(hwc->event_base + idx,
                             (u64)(-left) & x86_pmu.event_mask);

        perf_event_update_userpage(event);

        return ret;
}

static void x86_pmu_enable_event(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        if (cpuc->enabled)
                __x86_pmu_enable_event(&event->hw);
}

/*
 * activate a single event
 *
 * The event is added to the group of enabled events
 * but only if it can be scehduled with existing events.
 *
 * Called with PMU disabled. If successful and return value 1,
 * then guaranteed to call perf_enable() and hw_perf_enable()
 */
static int x86_pmu_enable(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc;
        int assign[X86_PMC_IDX_MAX];
        int n, n0, ret;

        hwc = &event->hw;

        n0 = cpuc->n_events;
        n = collect_events(cpuc, event, false);
        if (n < 0)
                return n;

        ret = x86_schedule_events(cpuc, n, assign);
        if (ret)
                return ret;
        /*
         * copy new assignment, now we know it is possible
         * will be used by hw_perf_enable()
         */
        memcpy(cpuc->assign, assign, n*sizeof(int));

        cpuc->n_events = n;
        cpuc->n_added += n - n0;

        return 0;
}

static int x86_pmu_start(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int idx = event->hw.idx;

        if (idx == -1)
                return -EAGAIN;

        x86_perf_event_set_period(event);
        cpuc->events[idx] = event;
        __set_bit(idx, cpuc->active_mask);
        x86_pmu.enable(event);
        perf_event_update_userpage(event);

        return 0;
}

static void x86_pmu_unthrottle(struct perf_event *event)
{
        int ret = x86_pmu_start(event);
        WARN_ON_ONCE(ret);
}

void perf_event_print_debug(void)
{
        u64 ctrl, status, overflow, pmc_ctrl, pmc_count, prev_left, fixed;
        struct cpu_hw_events *cpuc;
        unsigned long flags;
        int cpu, idx;

        if (!x86_pmu.num_events)
                return;

        local_irq_save(flags);

        cpu = smp_processor_id();
        cpuc = &per_cpu(cpu_hw_events, cpu);

        if (x86_pmu.version >= 2) {
                rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, ctrl);
                rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status);
                rdmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, overflow);
                rdmsrl(MSR_ARCH_PERFMON_FIXED_CTR_CTRL, fixed);

                pr_info("\n");
                pr_info("CPU#%d: ctrl:       %016llx\n", cpu, ctrl);
                pr_info("CPU#%d: status:     %016llx\n", cpu, status);
                pr_info("CPU#%d: overflow:   %016llx\n", cpu, overflow);
                pr_info("CPU#%d: fixed:      %016llx\n", cpu, fixed);
        }
        pr_info("CPU#%d: active:       %016llx\n", cpu, *(u64 *)cpuc->active_mask);

        for (idx = 0; idx < x86_pmu.num_events; idx++) {
                rdmsrl(x86_pmu.eventsel + idx, pmc_ctrl);
                rdmsrl(x86_pmu.perfctr  + idx, pmc_count);

                prev_left = per_cpu(pmc_prev_left[idx], cpu);

                pr_info("CPU#%d:   gen-PMC%d ctrl:  %016llx\n",
                        cpu, idx, pmc_ctrl);
                pr_info("CPU#%d:   gen-PMC%d count: %016llx\n",
                        cpu, idx, pmc_count);
                pr_info("CPU#%d:   gen-PMC%d left:  %016llx\n",
                        cpu, idx, prev_left);
        }
        for (idx = 0; idx < x86_pmu.num_events_fixed; idx++) {
                rdmsrl(MSR_ARCH_PERFMON_FIXED_CTR0 + idx, pmc_count);

                pr_info("CPU#%d: fixed-PMC%d count: %016llx\n",
                        cpu, idx, pmc_count);
        }
        local_irq_restore(flags);
}

static void x86_pmu_stop(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;

        if (!__test_and_clear_bit(idx, cpuc->active_mask))
                return;

        x86_pmu.disable(event);

        /*
         * Drain the remaining delta count out of a event
         * that we are disabling:
         */
        x86_perf_event_update(event);

        cpuc->events[idx] = NULL;
}

static void x86_pmu_disable(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        int i;

        x86_pmu_stop(event);

        for (i = 0; i < cpuc->n_events; i++) {
                if (event == cpuc->event_list[i]) {

                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, event);

                        while (++i < cpuc->n_events)
                                cpuc->event_list[i-1] = cpuc->event_list[i];

                        --cpuc->n_events;
                        break;
                }
        }
        perf_event_update_userpage(event);
}

static int x86_pmu_handle_irq(struct pt_regs *regs)
{
        struct perf_sample_data data;
        struct cpu_hw_events *cpuc;
        struct perf_event *event;
        struct hw_perf_event *hwc;
        int idx, handled = 0;
        u64 val;

        perf_sample_data_init(&data, 0);

        cpuc = &__get_cpu_var(cpu_hw_events);

        for (idx = 0; idx < x86_pmu.num_events; idx++) {
                if (!test_bit(idx, cpuc->active_mask))
                        continue;

                event = cpuc->events[idx];
                hwc = &event->hw;

                val = x86_perf_event_update(event);
                if (val & (1ULL << (x86_pmu.event_bits - 1)))
                        continue;

                /*
                 * event overflow
                 */
                handled         = 1;
                data.period     = event->hw.last_period;

                if (!x86_perf_event_set_period(event))
                        continue;

                if (perf_event_overflow(event, 1, &data, regs))
                        x86_pmu_stop(event);
        }

        if (handled)
                inc_irq_stat(apic_perf_irqs);

        return handled;
}

void smp_perf_pending_interrupt(struct pt_regs *regs)
{
        irq_enter();
        ack_APIC_irq();
        inc_irq_stat(apic_pending_irqs);
        perf_event_do_pending();
        irq_exit();
}

void set_perf_event_pending(void)
{
#ifdef CONFIG_X86_LOCAL_APIC
        if (!x86_pmu.apic || !x86_pmu_initialized())
                return;

        apic->send_IPI_self(LOCAL_PENDING_VECTOR);
#endif
}

void perf_events_lapic_init(void)
{
#ifdef CONFIG_X86_LOCAL_APIC
        if (!x86_pmu.apic || !x86_pmu_initialized())
                return;

        /*
         * Always use NMI for PMU
         */
        apic_write(APIC_LVTPC, APIC_DM_NMI);
#endif
}

static int __kprobes
perf_event_nmi_handler(struct notifier_block *self,
                         unsigned long cmd, void *__args)
{
        struct die_args *args = __args;
        struct pt_regs *regs;

        if (!atomic_read(&active_events))
                return NOTIFY_DONE;

        switch (cmd) {
        case DIE_NMI:
        case DIE_NMI_IPI:
                break;

        default:
                return NOTIFY_DONE;
        }

        regs = args->regs;

#ifdef CONFIG_X86_LOCAL_APIC
        apic_write(APIC_LVTPC, APIC_DM_NMI);
#endif
        /*
         * Can't rely on the handled return value to say it was our NMI, two
         * events could trigger 'simultaneously' raising two back-to-back NMIs.
         *
         * If the first NMI handles both, the latter will be empty and daze
         * the CPU.
         */
        x86_pmu.handle_irq(regs);

        return NOTIFY_STOP;
}

static __read_mostly struct notifier_block perf_event_nmi_notifier = {
        .notifier_call          = perf_event_nmi_handler,
        .next                   = NULL,
        .priority               = 1
};

static struct event_constraint unconstrained;
static struct event_constraint emptyconstraint;

static struct event_constraint *
x86_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
{
        struct event_constraint *c;

        if (x86_pmu.event_constraints) {
                for_each_event_constraint(c, x86_pmu.event_constraints) {
                        if ((event->hw.config & c->cmask) == c->code)
                                return c;
                }
        }

        return &unconstrained;
}

static int x86_event_sched_in(struct perf_event *event,
                          struct perf_cpu_context *cpuctx)
{
        int ret = 0;

        event->state = PERF_EVENT_STATE_ACTIVE;
        event->oncpu = smp_processor_id();
        event->tstamp_running += event->ctx->time - event->tstamp_stopped;

        if (!is_x86_event(event))
                ret = event->pmu->enable(event);

        if (!ret && !is_software_event(event))
                cpuctx->active_oncpu++;

        if (!ret && event->attr.exclusive)
                cpuctx->exclusive = 1;

        return ret;
}

static void x86_event_sched_out(struct perf_event *event,
                            struct perf_cpu_context *cpuctx)
{
        event->state = PERF_EVENT_STATE_INACTIVE;
        event->oncpu = -1;

        if (!is_x86_event(event))
                event->pmu->disable(event);

        event->tstamp_running -= event->ctx->time - event->tstamp_stopped;

        if (!is_software_event(event))
                cpuctx->active_oncpu--;

        if (event->attr.exclusive || !cpuctx->active_oncpu)
                cpuctx->exclusive = 0;
}

/*
 * Called to enable a whole group of events.
 * Returns 1 if the group was enabled, or -EAGAIN if it could not be.
 * Assumes the caller has disabled interrupts and has
 * frozen the PMU with hw_perf_save_disable.
 *
 * called with PMU disabled. If successful and return value 1,
 * then guaranteed to call perf_enable() and hw_perf_enable()
 */
int hw_perf_group_sched_in(struct perf_event *leader,
               struct perf_cpu_context *cpuctx,
               struct perf_event_context *ctx)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct perf_event *sub;
        int assign[X86_PMC_IDX_MAX];
        int n0, n1, ret;

        /* n0 = total number of events */
        n0 = collect_events(cpuc, leader, true);
        if (n0 < 0)
                return n0;

        ret = x86_schedule_events(cpuc, n0, assign);
        if (ret)
                return ret;

        ret = x86_event_sched_in(leader, cpuctx);
        if (ret)
                return ret;

        n1 = 1;
        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                if (sub->state > PERF_EVENT_STATE_OFF) {
                        ret = x86_event_sched_in(sub, cpuctx);
                        if (ret)
                                goto undo;
                        ++n1;
                }
        }
        /*
         * copy new assignment, now we know it is possible
         * will be used by hw_perf_enable()
         */
        memcpy(cpuc->assign, assign, n0*sizeof(int));

        cpuc->n_events  = n0;
        cpuc->n_added  += n1;
        ctx->nr_active += n1;

        /*
         * 1 means successful and events are active
         * This is not quite true because we defer
         * actual activation until hw_perf_enable() but
         * this way we* ensure caller won't try to enable
         * individual events
         */
        return 1;
undo:
        x86_event_sched_out(leader, cpuctx);
        n0  = 1;
        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                if (sub->state == PERF_EVENT_STATE_ACTIVE) {
                        x86_event_sched_out(sub, cpuctx);
                        if (++n0 == n1)
                                break;
                }
        }
        return ret;
}

#include "perf_event_amd.c"
#include "perf_event_p6.c"
#include "perf_event_intel.c"

static int __cpuinit
x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
{
        unsigned int cpu = (long)hcpu;
        int ret = NOTIFY_OK;

        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_UP_PREPARE:
                if (x86_pmu.cpu_prepare)
                        ret = x86_pmu.cpu_prepare(cpu);
                break;

        case CPU_STARTING:
                if (x86_pmu.cpu_starting)
                        x86_pmu.cpu_starting(cpu);
                break;

        case CPU_DYING:
                if (x86_pmu.cpu_dying)
                        x86_pmu.cpu_dying(cpu);
                break;

        case CPU_UP_CANCELED:
        case CPU_DEAD:
                if (x86_pmu.cpu_dead)
                        x86_pmu.cpu_dead(cpu);
                break;

        default:
                break;
        }

        return ret;
}

static void __init pmu_check_apic(void)
{
        if (cpu_has_apic)
                return;

        x86_pmu.apic = 0;
        pr_info("no APIC, boot with the \"lapic\" boot parameter to force-enable it.\n");
        pr_info("no hardware sampling interrupt available.\n");
}

void __init init_hw_perf_events(void)
{
        struct event_constraint *c;
        int err;

        pr_info("Performance Events: ");

        switch (boot_cpu_data.x86_vendor) {
        case X86_VENDOR_INTEL:
                err = intel_pmu_init();
                break;
        case X86_VENDOR_AMD:
                err = amd_pmu_init();
                break;
        default:
                return;
        }
        if (err != 0) {
                pr_cont("no PMU driver, software events only.\n");
                return;
        }

        pmu_check_apic();

        pr_cont("%s PMU driver.\n", x86_pmu.name);

        if (x86_pmu.num_events > X86_PMC_MAX_GENERIC) {
                WARN(1, KERN_ERR "hw perf events %d > max(%d), clipping!",
                     x86_pmu.num_events, X86_PMC_MAX_GENERIC);
                x86_pmu.num_events = X86_PMC_MAX_GENERIC;
        }
        perf_event_mask = (1 << x86_pmu.num_events) - 1;
        perf_max_events = x86_pmu.num_events;

        if (x86_pmu.num_events_fixed > X86_PMC_MAX_FIXED) {
                WARN(1, KERN_ERR "hw perf events fixed %d > max(%d), clipping!",
                     x86_pmu.num_events_fixed, X86_PMC_MAX_FIXED);
                x86_pmu.num_events_fixed = X86_PMC_MAX_FIXED;
        }

        perf_event_mask |=
                ((1LL << x86_pmu.num_events_fixed)-1) << X86_PMC_IDX_FIXED;
        x86_pmu.intel_ctrl = perf_event_mask;

        perf_events_lapic_init();
        register_die_notifier(&perf_event_nmi_notifier);

        unconstrained = (struct event_constraint)
                __EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_events) - 1,
                                   0, x86_pmu.num_events);

        if (x86_pmu.event_constraints) {
                for_each_event_constraint(c, x86_pmu.event_constraints) {
                        if (c->cmask != INTEL_ARCH_FIXED_MASK)
                                continue;

                        c->idxmsk64 |= (1ULL << x86_pmu.num_events) - 1;
                        c->weight += x86_pmu.num_events;
                }
        }

        pr_info("... version:                %d\n",     x86_pmu.version);
        pr_info("... bit width:              %d\n",     x86_pmu.event_bits);
        pr_info("... generic registers:      %d\n",     x86_pmu.num_events);
        pr_info("... value mask:             %016Lx\n", x86_pmu.event_mask);
        pr_info("... max period:             %016Lx\n", x86_pmu.max_period);
        pr_info("... fixed-purpose events:   %d\n",     x86_pmu.num_events_fixed);
        pr_info("... event mask:             %016Lx\n", perf_event_mask);

        perf_cpu_notifier(x86_pmu_notifier);
}

static inline void x86_pmu_read(struct perf_event *event)
{
        x86_perf_event_update(event);
}

static const struct pmu pmu = {
        .enable         = x86_pmu_enable,
        .disable        = x86_pmu_disable,
        .start          = x86_pmu_start,
        .stop           = x86_pmu_stop,
        .read           = x86_pmu_read,
        .unthrottle     = x86_pmu_unthrottle,
};

/*
 * validate a single event group
 *
 * validation include:
 *      - check events are compatible which each other
 *      - events do not compete for the same counter
 *      - number of events <= number of counters
 *
 * validation ensures the group can be loaded onto the
 * PMU if it was the only group available.
 */
static int validate_group(struct perf_event *event)
{
        struct perf_event *leader = event->group_leader;
        struct cpu_hw_events *fake_cpuc;
        int ret, n;

        ret = -ENOMEM;
        fake_cpuc = kmalloc(sizeof(*fake_cpuc), GFP_KERNEL | __GFP_ZERO);
        if (!fake_cpuc)
                goto out;

        /*
         * the event is not yet connected with its
         * siblings therefore we must first collect
         * existing siblings, then add the new event
         * before we can simulate the scheduling
         */
        ret = -ENOSPC;
        n = collect_events(fake_cpuc, leader, true);
        if (n < 0)
                goto out_free;

        fake_cpuc->n_events = n;
        n = collect_events(fake_cpuc, event, false);
        if (n < 0)
                goto out_free;

        fake_cpuc->n_events = n;

        ret = x86_schedule_events(fake_cpuc, n, NULL);

out_free:
        kfree(fake_cpuc);
out:
        return ret;
}

const struct pmu *hw_perf_event_init(struct perf_event *event)
{
        const struct pmu *tmp;
        int err;

        err = __hw_perf_event_init(event);
        if (!err) {
                /*
                 * we temporarily connect event to its pmu
                 * such that validate_group() can classify
                 * it as an x86 event using is_x86_event()
                 */
                tmp = event->pmu;
                event->pmu = &pmu;

                if (event->group_leader != event)
                        err = validate_group(event);

                event->pmu = tmp;
        }
        if (err) {
                if (event->destroy)
                        event->destroy(event);
                return ERR_PTR(err);
        }

        return &pmu;
}

/*
 * callchain support
 */

static inline
void callchain_store(struct perf_callchain_entry *entry, u64 ip)
{
        if (entry->nr < PERF_MAX_STACK_DEPTH)
                entry->ip[entry->nr++] = ip;
}

static DEFINE_PER_CPU(struct perf_callchain_entry, pmc_irq_entry);
static DEFINE_PER_CPU(struct perf_callchain_entry, pmc_nmi_entry);


static void
backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
{
        /* Ignore warnings */
}

static void backtrace_warning(void *data, char *msg)
{
        /* Ignore warnings */
}

static int backtrace_stack(void *data, char *name)
{
        return 0;
}

static void backtrace_address(void *data, unsigned long addr, int reliable)
{
        struct perf_callchain_entry *entry = data;

        if (reliable)
                callchain_store(entry, addr);
}

static const struct stacktrace_ops backtrace_ops = {
        .warning                = backtrace_warning,
        .warning_symbol         = backtrace_warning_symbol,
        .stack                  = backtrace_stack,
        .address                = backtrace_address,
        .walk_stack             = print_context_stack_bp,
};

#include "../dumpstack.h"

static void
perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
        callchain_store(entry, PERF_CONTEXT_KERNEL);
        callchain_store(entry, regs->ip);

        dump_trace(NULL, regs, NULL, regs->bp, &backtrace_ops, entry);
}

/*
 * best effort, GUP based copy_from_user() that assumes IRQ or NMI context
 */
static unsigned long
copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
{
        unsigned long offset, addr = (unsigned long)from;
        int type = in_nmi() ? KM_NMI : KM_IRQ0;
        unsigned long size, len = 0;
        struct page *page;
        void *map;
        int ret;

        do {
                ret = __get_user_pages_fast(addr, 1, 0, &page);
                if (!ret)
                        break;

                offset = addr & (PAGE_SIZE - 1);
                size = min(PAGE_SIZE - offset, n - len);

                map = kmap_atomic(page, type);
                memcpy(to, map+offset, size);
                kunmap_atomic(map, type);
                put_page(page);

                len  += size;
                to   += size;
                addr += size;

        } while (len < n);

        return len;
}

#ifdef CONFIG_COMPAT
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
        /* 32-bit process in 64-bit kernel. */
        struct stack_frame_ia32 frame;
        const void __user *fp;

        if (!test_thread_flag(TIF_IA32))
                return 0;

        fp = compat_ptr(regs->bp);
        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                unsigned long bytes;
                frame.next_frame     = 0;
                frame.return_address = 0;

                bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
                if (bytes != sizeof(frame))
                        break;

                if (fp < compat_ptr(regs->sp))
                        break;

                callchain_store(entry, frame.return_address);
                fp = compat_ptr(frame.next_frame);
        }
        return 1;
}
#else
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
    return 0;
}
#endif

static void
perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
        struct stack_frame frame;
        const void __user *fp;

        if (!user_mode(regs))
                regs = task_pt_regs(current);

        fp = (void __user *)regs->bp;

        callchain_store(entry, PERF_CONTEXT_USER);
        callchain_store(entry, regs->ip);

        if (perf_callchain_user32(regs, entry))
                return;

        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                unsigned long bytes;
                frame.next_frame             = NULL;
                frame.return_address = 0;

                bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
                if (bytes != sizeof(frame))
                        break;

                if ((unsigned long)fp < regs->sp)
                        break;

                callchain_store(entry, frame.return_address);
                fp = frame.next_frame;
        }
}

static void
perf_do_callchain(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
        int is_user;

        if (!regs)
                return;

        is_user = user_mode(regs);

        if (is_user && current->state != TASK_RUNNING)
                return;

        if (!is_user)
                perf_callchain_kernel(regs, entry);

        if (current->mm)
                perf_callchain_user(regs, entry);
}

struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
{
        struct perf_callchain_entry *entry;

        if (in_nmi())
                entry = &__get_cpu_var(pmc_nmi_entry);
        else
                entry = &__get_cpu_var(pmc_irq_entry);

        entry->nr = 0;

        perf_do_callchain(regs, entry);

        return entry;
}

void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip)
{
        regs->ip = ip;
        /*
         * perf_arch_fetch_caller_regs adds another call, we need to increment
         * the skip level
         */
        regs->bp = rewind_frame_pointer(skip + 1);
        regs->cs = __KERNEL_CS;
        local_save_flags(regs->flags);
}