/*
 * 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
 *  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/cpu.h>
#include <linux/bitops.h>
#include <linux/device.h>

#include <asm/apic.h>
#include <asm/stacktrace.h>
#include <asm/nmi.h>
#include <asm/smp.h>
#include <asm/alternative.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/timer.h>
#include <asm/desc.h>
#include <asm/ldt.h>

#include "perf_event.h"

struct x86_pmu x86_pmu __read_mostly;

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

struct static_key rdpmc_always_available = STATIC_KEY_INIT_FALSE;

u64 __read_mostly hw_cache_event_ids
                                [PERF_COUNT_HW_CACHE_MAX]
                                [PERF_COUNT_HW_CACHE_OP_MAX]
                                [PERF_COUNT_HW_CACHE_RESULT_MAX];
u64 __read_mostly hw_cache_extra_regs
                                [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.
 */
u64 x86_perf_event_update(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        int shift = 64 - x86_pmu.cntval_bits;
        u64 prev_raw_count, new_raw_count;
        int idx = hwc->idx;
        s64 delta;

        if (idx == INTEL_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 = local64_read(&hwc->prev_count);
        rdpmcl(hwc->event_base_rdpmc, new_raw_count);

        if (local64_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;

        local64_add(delta, &event->count);
        local64_sub(delta, &hwc->period_left);

        return new_raw_count;
}

/*
 * Find and validate any extra registers to set up.
 */
static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
{
        struct hw_perf_event_extra *reg;
        struct extra_reg *er;

        reg = &event->hw.extra_reg;

        if (!x86_pmu.extra_regs)
                return 0;

        for (er = x86_pmu.extra_regs; er->msr; er++) {
                if (er->event != (config & er->config_mask))
                        continue;
                if (event->attr.config1 & ~er->valid_mask)
                        return -EINVAL;
                /* Check if the extra msrs can be safely accessed*/
                if (!er->extra_msr_access)
                        return -ENXIO;

                reg->idx = er->idx;
                reg->config = event->attr.config1;
                reg->reg = er->msr;
                break;
        }
        return 0;
}

static atomic_t active_events;
static atomic_t pmc_refcount;
static DEFINE_MUTEX(pmc_reserve_mutex);

#ifdef CONFIG_X86_LOCAL_APIC

static bool reserve_pmc_hardware(void)
{
        int i;

        for (i = 0; i < x86_pmu.num_counters; i++) {
                if (!reserve_perfctr_nmi(x86_pmu_event_addr(i)))
                        goto perfctr_fail;
        }

        for (i = 0; i < x86_pmu.num_counters; i++) {
                if (!reserve_evntsel_nmi(x86_pmu_config_addr(i)))
                        goto eventsel_fail;
        }

        return true;

eventsel_fail:
        for (i--; i >= 0; i--)
                release_evntsel_nmi(x86_pmu_config_addr(i));

        i = x86_pmu.num_counters;

perfctr_fail:
        for (i--; i >= 0; i--)
                release_perfctr_nmi(x86_pmu_event_addr(i));

        return false;
}

static void release_pmc_hardware(void)
{
        int i;

        for (i = 0; i < x86_pmu.num_counters; i++) {
                release_perfctr_nmi(x86_pmu_event_addr(i));
                release_evntsel_nmi(x86_pmu_config_addr(i));
        }
}

#else

static bool reserve_pmc_hardware(void) { return true; }
static void release_pmc_hardware(void) {}

#endif

static bool check_hw_exists(void)
{
        u64 val, val_fail, val_new= ~0;
        int i, reg, reg_fail, ret = 0;
        int bios_fail = 0;
        int reg_safe = -1;

        /*
         * Check to see if the BIOS enabled any of the counters, if so
         * complain and bail.
         */
        for (i = 0; i < x86_pmu.num_counters; i++) {
                reg = x86_pmu_config_addr(i);
                ret = rdmsrl_safe(reg, &val);
                if (ret)
                        goto msr_fail;
                if (val & ARCH_PERFMON_EVENTSEL_ENABLE) {
                        bios_fail = 1;
                        val_fail = val;
                        reg_fail = reg;
                } else {
                        reg_safe = i;
                }
        }

        if (x86_pmu.num_counters_fixed) {
                reg = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
                ret = rdmsrl_safe(reg, &val);
                if (ret)
                        goto msr_fail;
                for (i = 0; i < x86_pmu.num_counters_fixed; i++) {
                        if (val & (0x03 << i*4)) {
                                bios_fail = 1;
                                val_fail = val;
                                reg_fail = reg;
                        }
                }
        }

        /*
         * If all the counters are enabled, the below test will always
         * fail.  The tools will also become useless in this scenario.
         * Just fail and disable the hardware counters.
         */

        if (reg_safe == -1) {
                reg = reg_safe;
                goto msr_fail;
        }

        /*
         * Read the current value, change it and read it back to see if it
         * matches, this is needed to detect certain hardware emulators
         * (qemu/kvm) that don't trap on the MSR access and always return 0s.
         */
        reg = x86_pmu_event_addr(reg_safe);
        if (rdmsrl_safe(reg, &val))
                goto msr_fail;
        val ^= 0xffffUL;
        ret = wrmsrl_safe(reg, val);
        ret |= rdmsrl_safe(reg, &val_new);
        if (ret || val != val_new)
                goto msr_fail;

        /*
         * We still allow the PMU driver to operate:
         */
        if (bios_fail) {
                pr_cont("Broken BIOS detected, complain to your hardware vendor.\n");
                pr_err(FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n",
                              reg_fail, val_fail);
        }

        return true;

msr_fail:
        pr_cont("Broken PMU hardware detected, using software events only.\n");
        pr_info("%sFailed to access perfctr msr (MSR %x is %Lx)\n",
                boot_cpu_has(X86_FEATURE_HYPERVISOR) ? KERN_INFO : KERN_ERR,
                reg, val_new);

        return false;
}

static void hw_perf_event_destroy(struct perf_event *event)
{
        x86_release_hardware();
        atomic_dec(&active_events);
}

void hw_perf_lbr_event_destroy(struct perf_event *event)
{
        hw_perf_event_destroy(event);

        /* undo the lbr/bts event accounting */
        x86_del_exclusive(x86_lbr_exclusive_lbr);
}

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 *event)
{
        struct perf_event_attr *attr = &event->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;
        attr->config1 = hw_cache_extra_regs[cache_type][cache_op][cache_result];
        return x86_pmu_extra_regs(val, event);
}

int x86_reserve_hardware(void)
{
        int err = 0;

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

        return err;
}

void x86_release_hardware(void)
{
        if (atomic_dec_and_mutex_lock(&pmc_refcount, &pmc_reserve_mutex)) {
                release_pmc_hardware();
                release_ds_buffers();
                mutex_unlock(&pmc_reserve_mutex);
        }
}

/*
 * Check if we can create event of a certain type (that no conflicting events
 * are present).
 */
int x86_add_exclusive(unsigned int what)
{
        int i;

        if (!atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what])) {
                mutex_lock(&pmc_reserve_mutex);
                for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) {
                        if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i]))
                                goto fail_unlock;
                }
                atomic_inc(&x86_pmu.lbr_exclusive[what]);
                mutex_unlock(&pmc_reserve_mutex);
        }

        atomic_inc(&active_events);
        return 0;

fail_unlock:
        mutex_unlock(&pmc_reserve_mutex);
        return -EBUSY;
}

void x86_del_exclusive(unsigned int what)
{
        atomic_dec(&x86_pmu.lbr_exclusive[what]);
        atomic_dec(&active_events);
}

int x86_setup_perfctr(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        u64 config;

        if (!is_sampling_event(event)) {
                hwc->sample_period = x86_pmu.max_period;
                hwc->last_period = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }

        if (attr->type == PERF_TYPE_RAW)
                return x86_pmu_extra_regs(event->attr.config, event);

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

        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 &&
            !attr->freq && hwc->sample_period == 1) {
                /* BTS is not supported by this architecture. */
                if (!x86_pmu.bts_active)
                        return -EOPNOTSUPP;

                /* BTS is currently only allowed for user-mode. */
                if (!attr->exclude_kernel)
                        return -EOPNOTSUPP;

                /* disallow bts if conflicting events are present */
                if (x86_add_exclusive(x86_lbr_exclusive_lbr))
                        return -EBUSY;

                event->destroy = hw_perf_lbr_event_destroy;
        }

        hwc->config |= config;

        return 0;
}

/*
 * check that branch_sample_type is compatible with
 * settings needed for precise_ip > 1 which implies
 * using the LBR to capture ALL taken branches at the
 * priv levels of the measurement
 */
static inline int precise_br_compat(struct perf_event *event)
{
        u64 m = event->attr.branch_sample_type;
        u64 b = 0;

        /* must capture all branches */
        if (!(m & PERF_SAMPLE_BRANCH_ANY))
                return 0;

        m &= PERF_SAMPLE_BRANCH_KERNEL | PERF_SAMPLE_BRANCH_USER;

        if (!event->attr.exclude_user)
                b |= PERF_SAMPLE_BRANCH_USER;

        if (!event->attr.exclude_kernel)
                b |= PERF_SAMPLE_BRANCH_KERNEL;

        /*
         * ignore PERF_SAMPLE_BRANCH_HV, not supported on x86
         */

        return m == b;
}

int x86_pmu_hw_config(struct perf_event *event)
{
        if (event->attr.precise_ip) {
                int precise = 0;

                /* Support for constant skid */
                if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
                        precise++;

                        /* Support for IP fixup */
                        if (x86_pmu.lbr_nr || x86_pmu.intel_cap.pebs_format >= 2)
                                precise++;

                        if (x86_pmu.pebs_prec_dist)
                                precise++;
                }

                if (event->attr.precise_ip > precise)
                        return -EOPNOTSUPP;
        }
        /*
         * check that PEBS LBR correction does not conflict with
         * whatever the user is asking with attr->branch_sample_type
         */
        if (event->attr.precise_ip > 1 && x86_pmu.intel_cap.pebs_format < 2) {
                u64 *br_type = &event->attr.branch_sample_type;

                if (has_branch_stack(event)) {
                        if (!precise_br_compat(event))
                                return -EOPNOTSUPP;

                        /* branch_sample_type is compatible */

                } else {
                        /*
                         * user did not specify  branch_sample_type
                         *
                         * For PEBS fixups, we capture all
                         * the branches at the priv level of the
                         * event.
                         */
                        *br_type = PERF_SAMPLE_BRANCH_ANY;

                        if (!event->attr.exclude_user)
                                *br_type |= PERF_SAMPLE_BRANCH_USER;

                        if (!event->attr.exclude_kernel)
                                *br_type |= PERF_SAMPLE_BRANCH_KERNEL;
                }
        }

        if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)
                event->attach_state |= PERF_ATTACH_TASK_DATA;

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

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

        if (event->attr.type == PERF_TYPE_RAW)
                event->hw.config |= event->attr.config & X86_RAW_EVENT_MASK;

        if (event->attr.sample_period && x86_pmu.limit_period) {
                if (x86_pmu.limit_period(event, event->attr.sample_period) >
                                event->attr.sample_period)
                        return -EINVAL;
        }

        return x86_setup_perfctr(event);
}

/*
 * Setup the hardware configuration for a given attr_type
 */
static int __x86_pmu_event_init(struct perf_event *event)
{
        int err;

        if (!x86_pmu_initialized())
                return -ENODEV;

        err = x86_reserve_hardware();
        if (err)
                return err;

        atomic_inc(&active_events);
        event->destroy = hw_perf_event_destroy;

        event->hw.idx = -1;
        event->hw.last_cpu = -1;
        event->hw.last_tag = ~0ULL;

        /* mark unused */
        event->hw.extra_reg.idx = EXTRA_REG_NONE;
        event->hw.branch_reg.idx = EXTRA_REG_NONE;

        return x86_pmu.hw_config(event);
}

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

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

                if (!test_bit(idx, cpuc->active_mask))
                        continue;
                rdmsrl(x86_pmu_config_addr(idx), val);
                if (!(val & ARCH_PERFMON_EVENTSEL_ENABLE))
                        continue;
                val &= ~ARCH_PERFMON_EVENTSEL_ENABLE;
                wrmsrl(x86_pmu_config_addr(idx), val);
        }
}

/*
 * There may be PMI landing after enabled=0. The PMI hitting could be before or
 * after disable_all.
 *
 * If PMI hits before disable_all, the PMU will be disabled in the NMI handler.
 * It will not be re-enabled in the NMI handler again, because enabled=0. After
 * handling the NMI, disable_all will be called, which will not change the
 * state either. If PMI hits after disable_all, the PMU is already disabled
 * before entering NMI handler. The NMI handler will not change the state
 * either.
 *
 * So either situation is harmless.
 */
static void x86_pmu_disable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (!x86_pmu_initialized())
                return;

        if (!cpuc->enabled)
                return;

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

        x86_pmu.disable_all();
}

void x86_pmu_enable_all(int added)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        int idx;

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                struct hw_perf_event *hwc = &cpuc->events[idx]->hw;

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

                __x86_pmu_enable_event(hwc, ARCH_PERFMON_EVENTSEL_ENABLE);
        }
}

static struct pmu pmu;

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

/*
 * Event scheduler state:
 *
 * Assign events iterating over all events and counters, beginning
 * with events with least weights first. Keep the current iterator
 * state in struct sched_state.
 */
struct sched_state {
        int     weight;
        int     event;          /* event index */
        int     counter;        /* counter index */
        int     unassigned;     /* number of events to be assigned left */
        int     nr_gp;          /* number of GP counters used */
        unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
};

/* Total max is X86_PMC_IDX_MAX, but we are O(n!) limited */
#define SCHED_STATES_MAX        2

struct perf_sched {
        int                     max_weight;
        int                     max_events;
        int                     max_gp;
        int                     saved_states;
        struct event_constraint **constraints;
        struct sched_state      state;
        struct sched_state      saved[SCHED_STATES_MAX];
};

/*
 * Initialize interator that runs through all events and counters.
 */
static void perf_sched_init(struct perf_sched *sched, struct event_constraint **constraints,
                            int num, int wmin, int wmax, int gpmax)
{
        int idx;

        memset(sched, 0, sizeof(*sched));
        sched->max_events       = num;
        sched->max_weight       = wmax;
        sched->max_gp           = gpmax;
        sched->constraints      = constraints;

        for (idx = 0; idx < num; idx++) {
                if (constraints[idx]->weight == wmin)
                        break;
        }

        sched->state.event      = idx;          /* start with min weight */
        sched->state.weight     = wmin;
        sched->state.unassigned = num;
}

static void perf_sched_save_state(struct perf_sched *sched)
{
        if (WARN_ON_ONCE(sched->saved_states >= SCHED_STATES_MAX))
                return;

        sched->saved[sched->saved_states] = sched->state;
        sched->saved_states++;
}

static bool perf_sched_restore_state(struct perf_sched *sched)
{
        if (!sched->saved_states)
                return false;

        sched->saved_states--;
        sched->state = sched->saved[sched->saved_states];

        /* continue with next counter: */
        clear_bit(sched->state.counter++, sched->state.used);

        return true;
}

/*
 * Select a counter for the current event to schedule. Return true on
 * success.
 */
static bool __perf_sched_find_counter(struct perf_sched *sched)
{
        struct event_constraint *c;
        int idx;

        if (!sched->state.unassigned)
                return false;

        if (sched->state.event >= sched->max_events)
                return false;

        c = sched->constraints[sched->state.event];
        /* Prefer fixed purpose counters */
        if (c->idxmsk64 & (~0ULL << INTEL_PMC_IDX_FIXED)) {
                idx = INTEL_PMC_IDX_FIXED;
                for_each_set_bit_from(idx, c->idxmsk, X86_PMC_IDX_MAX) {
                        if (!__test_and_set_bit(idx, sched->state.used))
                                goto done;
                }
        }

        /* Grab the first unused counter starting with idx */
        idx = sched->state.counter;
        for_each_set_bit_from(idx, c->idxmsk, INTEL_PMC_IDX_FIXED) {
                if (!__test_and_set_bit(idx, sched->state.used)) {
                        if (sched->state.nr_gp++ >= sched->max_gp)
                                return false;

                        goto done;
                }
        }

        return false;

done:
        sched->state.counter = idx;

        if (c->overlap)
                perf_sched_save_state(sched);

        return true;
}

static bool perf_sched_find_counter(struct perf_sched *sched)
{
        while (!__perf_sched_find_counter(sched)) {
                if (!perf_sched_restore_state(sched))
                        return false;
        }

        return true;
}

/*
 * Go through all unassigned events and find the next one to schedule.
 * Take events with the least weight first. Return true on success.
 */
static bool perf_sched_next_event(struct perf_sched *sched)
{
        struct event_constraint *c;

        if (!sched->state.unassigned || !--sched->state.unassigned)
                return false;

        do {
                /* next event */
                sched->state.event++;
                if (sched->state.event >= sched->max_events) {
                        /* next weight */
                        sched->state.event = 0;
                        sched->state.weight++;
                        if (sched->state.weight > sched->max_weight)
                                return false;
                }
                c = sched->constraints[sched->state.event];
        } while (c->weight != sched->state.weight);

        sched->state.counter = 0;       /* start with first counter */

        return true;
}

/*
 * Assign a counter for each event.
 */
int perf_assign_events(struct event_constraint **constraints, int n,
                        int wmin, int wmax, int gpmax, int *assign)
{
        struct perf_sched sched;

        perf_sched_init(&sched, constraints, n, wmin, wmax, gpmax);

        do {
                if (!perf_sched_find_counter(&sched))
                        break;  /* failed */
                if (assign)
                        assign[sched.state.event] = sched.state.counter;
        } while (perf_sched_next_event(&sched));

        return sched.state.unassigned;
}
EXPORT_SYMBOL_GPL(perf_assign_events);

int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
{
        struct event_constraint *c;
        unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
        struct perf_event *e;
        int i, wmin, wmax, unsched = 0;
        struct hw_perf_event *hwc;

        bitmap_zero(used_mask, X86_PMC_IDX_MAX);

        if (x86_pmu.start_scheduling)
                x86_pmu.start_scheduling(cpuc);

        for (i = 0, wmin = X86_PMC_IDX_MAX, wmax = 0; i < n; i++) {
                cpuc->event_constraint[i] = NULL;
                c = x86_pmu.get_event_constraints(cpuc, i, cpuc->event_list[i]);
                cpuc->event_constraint[i] = c;

                wmin = min(wmin, c->weight);
                wmax = max(wmax, c->weight);
        }

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

        /* slow path */
        if (i != n) {
                int gpmax = x86_pmu.num_counters;

                /*
                 * Do not allow scheduling of more than half the available
                 * generic counters.
                 *
                 * This helps avoid counter starvation of sibling thread by
                 * ensuring at most half the counters cannot be in exclusive
                 * mode. There is no designated counters for the limits. Any
                 * N/2 counters can be used. This helps with events with
                 * specific counter constraints.
                 */
                if (is_ht_workaround_enabled() && !cpuc->is_fake &&
                    READ_ONCE(cpuc->excl_cntrs->exclusive_present))
                        gpmax /= 2;

                unsched = perf_assign_events(cpuc->event_constraint, n, wmin,
                                             wmax, gpmax, assign);
        }

        /*
         * In case of success (unsched = 0), mark events as committed,
         * so we do not put_constraint() in case new events are added
         * and fail to be scheduled
         *
         * We invoke the lower level commit callback to lock the resource
         *
         * We do not need to do all of this in case we are called to
         * validate an event group (assign == NULL)
         */
        if (!unsched && assign) {
                for (i = 0; i < n; i++) {
                        e = cpuc->event_list[i];
                        e->hw.flags |= PERF_X86_EVENT_COMMITTED;
                        if (x86_pmu.commit_scheduling)
                                x86_pmu.commit_scheduling(cpuc, i, assign[i]);
                }
        } else {
                for (i = 0; i < n; i++) {
                        e = cpuc->event_list[i];
                        /*
                         * do not put_constraint() on comitted events,
                         * because they are good to go
                         */
                        if ((e->hw.flags & PERF_X86_EVENT_COMMITTED))
                                continue;

                        /*
                         * release events that failed scheduling
                         */
                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, e);
                }
        }

        if (x86_pmu.stop_scheduling)
                x86_pmu.stop_scheduling(cpuc);

        return unsched ? -EINVAL : 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_counters + x86_pmu.num_counters_fixed;

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

        if (is_x86_event(leader)) {
                if (n >= max_count)
                        return -EINVAL;
                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 -EINVAL;

                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 == INTEL_PMC_IDX_FIXED_BTS) {
                hwc->config_base = 0;
                hwc->event_base = 0;
        } else if (hwc->idx >= INTEL_PMC_IDX_FIXED) {
                hwc->config_base = MSR_ARCH_PERFMON_FIXED_CTR_CTRL;
                hwc->event_base = MSR_ARCH_PERFMON_FIXED_CTR0 + (hwc->idx - INTEL_PMC_IDX_FIXED);
                hwc->event_base_rdpmc = (hwc->idx - INTEL_PMC_IDX_FIXED) | 1<<30;
        } else {
                hwc->config_base = x86_pmu_config_addr(hwc->idx);
                hwc->event_base  = x86_pmu_event_addr(hwc->idx);
                hwc->event_base_rdpmc = x86_pmu_rdpmc_index(hwc->idx);

        }
}

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 void x86_pmu_start(struct perf_event *event, int flags);

static void x86_pmu_enable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct perf_event *event;
        struct hw_perf_event *hwc;
        int i, added = cpuc->n_added;

        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
                 */
                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;

                        /*
                         * Ensure we don't accidentally enable a stopped
                         * counter simply because we rescheduled.
                         */
                        if (hwc->state & PERF_HES_STOPPED)
                                hwc->state |= PERF_HES_ARCH;

                        x86_pmu_stop(event, PERF_EF_UPDATE);
                }

                /*
                 * step2: reprogram moved events into new counters
                 */
                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;

                        if (hwc->state & PERF_HES_ARCH)
                                continue;

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

        cpuc->enabled = 1;
        barrier();

        x86_pmu.enable_all(added);
}

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:
 */
int x86_perf_event_set_period(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        s64 left = local64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int ret = 0, idx = hwc->idx;

        if (idx == INTEL_PMC_IDX_FIXED_BTS)
                return 0;

        /*
         * If we are way outside a reasonable range then just skip forward:
         */
        if (unlikely(left <= -period)) {
                left = period;
                local64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }

        if (unlikely(left <= 0)) {
                left += period;
                local64_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;

        if (x86_pmu.limit_period)
                left = x86_pmu.limit_period(event, left);

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

        if (!(hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) ||
            local64_read(&hwc->prev_count) != (u64)-left) {
                /*
                 * The hw event starts counting from this event offset,
                 * mark it to be able to extra future deltas:
                 */
                local64_set(&hwc->prev_count, (u64)-left);

                wrmsrl(hwc->event_base, (u64)(-left) & x86_pmu.cntval_mask);
        }

        /*
         * Due to erratum on certan cpu we need
         * a second write to be sure the register
         * is updated properly
         */
        if (x86_pmu.perfctr_second_write) {
                wrmsrl(hwc->event_base,
                        (u64)(-left) & x86_pmu.cntval_mask);
        }

        perf_event_update_userpage(event);

        return ret;
}

void x86_pmu_enable_event(struct perf_event *event)
{
        if (__this_cpu_read(cpu_hw_events.enabled))
                __x86_pmu_enable_event(&event->hw,
                                       ARCH_PERFMON_EVENTSEL_ENABLE);
}

/*
 * Add a single event to the PMU.
 *
 * The event is added to the group of enabled events
 * but only if it can be scehduled with existing events.
 */
static int x86_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&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;
        ret = n = collect_events(cpuc, event, false);
        if (ret < 0)
                goto out;

        hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
        if (!(flags & PERF_EF_START))
                hwc->state |= PERF_HES_ARCH;

        /*
         * If group events scheduling transaction was started,
         * skip the schedulability test here, it will be performed
         * at commit time (->commit_txn) as a whole.
         */
        if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
                goto done_collect;

        ret = x86_pmu.schedule_events(cpuc, n, assign);
        if (ret)
                goto out;
        /*
         * copy new assignment, now we know it is possible
         * will be used by hw_perf_enable()
         */
        memcpy(cpuc->assign, assign, n*sizeof(int));

done_collect:
        /*
         * Commit the collect_events() state. See x86_pmu_del() and
         * x86_pmu_*_txn().
         */
        cpuc->n_events = n;
        cpuc->n_added += n - n0;
        cpuc->n_txn += n - n0;

        ret = 0;
out:
        return ret;
}

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

        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
                return;

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

        if (flags & PERF_EF_RELOAD) {
                WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));
                x86_perf_event_set_period(event);
        }

        event->hw.state = 0;

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

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

        if (!x86_pmu.num_counters)
                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);
                if (x86_pmu.pebs_constraints) {
                        rdmsrl(MSR_IA32_PEBS_ENABLE, pebs);
                        pr_info("CPU#%d: pebs:       %016llx\n", cpu, pebs);
                }
                if (x86_pmu.lbr_nr) {
                        rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
                        pr_info("CPU#%d: debugctl:   %016llx\n", cpu, debugctl);
                }
        }
        pr_info("CPU#%d: active:     %016llx\n", cpu, *(u64 *)cpuc->active_mask);

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                rdmsrl(x86_pmu_config_addr(idx), pmc_ctrl);
                rdmsrl(x86_pmu_event_addr(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_counters_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);
}

void x86_pmu_stop(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;

        if (__test_and_clear_bit(hwc->idx, cpuc->active_mask)) {
                x86_pmu.disable(event);
                cpuc->events[hwc->idx] = NULL;
                WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
                hwc->state |= PERF_HES_STOPPED;
        }

        if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
                /*
                 * Drain the remaining delta count out of a event
                 * that we are disabling:
                 */
                x86_perf_event_update(event);
                hwc->state |= PERF_HES_UPTODATE;
        }
}

static void x86_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        int i;

        /*
         * event is descheduled
         */
        event->hw.flags &= ~PERF_X86_EVENT_COMMITTED;

        /*
         * If we're called during a txn, we don't need to do anything.
         * The events never got scheduled and ->cancel_txn will truncate
         * the event_list.
         *
         * XXX assumes any ->del() called during a TXN will only be on
         * an event added during that same TXN.
         */
        if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
                return;

        /*
         * Not a TXN, therefore cleanup properly.
         */
        x86_pmu_stop(event, PERF_EF_UPDATE);

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

        if (WARN_ON_ONCE(i == cpuc->n_events)) /* called ->del() without ->add() ? */
                return;

        /* If we have a newly added event; make sure to decrease n_added. */
        if (i >= cpuc->n_events - cpuc->n_added)
                --cpuc->n_added;

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

        /* Delete the array entry. */
        while (++i < cpuc->n_events) {
                cpuc->event_list[i-1] = cpuc->event_list[i];
                cpuc->event_constraint[i-1] = cpuc->event_constraint[i];
        }
        --cpuc->n_events;

        perf_event_update_userpage(event);
}

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

        cpuc = this_cpu_ptr(&cpu_hw_events);

        /*
         * Some chipsets need to unmask the LVTPC in a particular spot
         * inside the nmi handler.  As a result, the unmasking was pushed
         * into all the nmi handlers.
         *
         * This generic handler doesn't seem to have any issues where the
         * unmasking occurs so it was left at the top.
         */
        apic_write(APIC_LVTPC, APIC_DM_NMI);

        for (idx = 0; idx < x86_pmu.num_counters; idx++) {
                if (!test_bit(idx, cpuc->active_mask)) {
                        /*
                         * Though we deactivated the counter some cpus
                         * might still deliver spurious interrupts still
                         * in flight. Catch them:
                         */
                        if (__test_and_clear_bit(idx, cpuc->running))
                                handled++;
                        continue;
                }

                event = cpuc->events[idx];

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

                /*
                 * event overflow
                 */
                handled++;
                perf_sample_data_init(&data, 0, event->hw.last_period);

                if (!x86_perf_event_set_period(event))
                        continue;

                if (perf_event_overflow(event, &data, regs))
                        x86_pmu_stop(event, 0);
        }

        if (handled)
                inc_irq_stat(apic_perf_irqs);

        return handled;
}

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

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

static int
perf_event_nmi_handler(unsigned int cmd, struct pt_regs *regs)
{
        u64 start_clock;
        u64 finish_clock;
        int ret;

        /*
         * All PMUs/events that share this PMI handler should make sure to
         * increment active_events for their events.
         */
        if (!atomic_read(&active_events))
                return NMI_DONE;

        start_clock = sched_clock();
        ret = x86_pmu.handle_irq(regs);
        finish_clock = sched_clock();

        perf_sample_event_took(finish_clock - start_clock);

        return ret;
}
NOKPROBE_SYMBOL(perf_event_nmi_handler);

struct event_constraint emptyconstraint;
struct event_constraint unconstrained;

static int
x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
{
        unsigned int cpu = (long)hcpu;
        struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
        int i, ret = NOTIFY_OK;

        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_UP_PREPARE:
                for (i = 0 ; i < X86_PERF_KFREE_MAX; i++)
                        cpuc->kfree_on_online[i] = NULL;
                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_ONLINE:
                for (i = 0 ; i < X86_PERF_KFREE_MAX; i++) {
                        kfree(cpuc->kfree_on_online[i]);
                        cpuc->kfree_on_online[i] = NULL;
                }
                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");

        /*
         * 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):
         */
        pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;

}

static struct attribute_group x86_pmu_format_group = {
        .name = "format",
        .attrs = NULL,
};

/*
 * Remove all undefined events (x86_pmu.event_map(id) == 0)
 * out of events_attr attributes.
 */
static void __init filter_events(struct attribute **attrs)
{
        struct device_attribute *d;
        struct perf_pmu_events_attr *pmu_attr;
        int offset = 0;
        int i, j;

        for (i = 0; attrs[i]; i++) {
                d = (struct device_attribute *)attrs[i];
                pmu_attr = container_of(d, struct perf_pmu_events_attr, attr);
                /* str trumps id */
                if (pmu_attr->event_str)
                        continue;
                if (x86_pmu.event_map(i + offset))
                        continue;

                for (j = i; attrs[j]; j++)
                        attrs[j] = attrs[j + 1];

                /* Check the shifted attr. */
                i--;

                /*
                 * event_map() is index based, the attrs array is organized
                 * by increasing event index. If we shift the events, then
                 * we need to compensate for the event_map(), otherwise
                 * we are looking up the wrong event in the map
                 */
                offset++;
        }
}

/* Merge two pointer arrays */
__init struct attribute **merge_attr(struct attribute **a, struct attribute **b)
{
        struct attribute **new;
        int j, i;

        for (j = 0; a[j]; j++)
                ;
        for (i = 0; b[i]; i++)
                j++;
        j++;

        new = kmalloc(sizeof(struct attribute *) * j, GFP_KERNEL);
        if (!new)
                return NULL;

        j = 0;
        for (i = 0; a[i]; i++)
                new[j++] = a[i];
        for (i = 0; b[i]; i++)
                new[j++] = b[i];
        new[j] = NULL;

        return new;
}

ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr, char *page)
{
        struct perf_pmu_events_attr *pmu_attr = \
                container_of(attr, struct perf_pmu_events_attr, attr);
        u64 config = x86_pmu.event_map(pmu_attr->id);

        /* string trumps id */
        if (pmu_attr->event_str)
                return sprintf(page, "%s", pmu_attr->event_str);

        return x86_pmu.events_sysfs_show(page, config);
}
EXPORT_SYMBOL_GPL(events_sysfs_show);

EVENT_ATTR(cpu-cycles,                  CPU_CYCLES              );
EVENT_ATTR(instructions,                INSTRUCTIONS            );
EVENT_ATTR(cache-references,            CACHE_REFERENCES        );
EVENT_ATTR(cache-misses,                CACHE_MISSES            );
EVENT_ATTR(branch-instructions,         BRANCH_INSTRUCTIONS     );
EVENT_ATTR(branch-misses,               BRANCH_MISSES           );
EVENT_ATTR(bus-cycles,                  BUS_CYCLES              );
EVENT_ATTR(stalled-cycles-frontend,     STALLED_CYCLES_FRONTEND );
EVENT_ATTR(stalled-cycles-backend,      STALLED_CYCLES_BACKEND  );
EVENT_ATTR(ref-cycles,                  REF_CPU_CYCLES          );

static struct attribute *empty_attrs;

static struct attribute *events_attr[] = {
        EVENT_PTR(CPU_CYCLES),
        EVENT_PTR(INSTRUCTIONS),
        EVENT_PTR(CACHE_REFERENCES),
        EVENT_PTR(CACHE_MISSES),
        EVENT_PTR(BRANCH_INSTRUCTIONS),
        EVENT_PTR(BRANCH_MISSES),
        EVENT_PTR(BUS_CYCLES),
        EVENT_PTR(STALLED_CYCLES_FRONTEND),
        EVENT_PTR(STALLED_CYCLES_BACKEND),
        EVENT_PTR(REF_CPU_CYCLES),
        NULL,
};

static struct attribute_group x86_pmu_events_group = {
        .name = "events",
        .attrs = events_attr,
};

ssize_t x86_event_sysfs_show(char *page, u64 config, u64 event)
{
        u64 umask  = (config & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
        u64 cmask  = (config & ARCH_PERFMON_EVENTSEL_CMASK) >> 24;
        bool edge  = (config & ARCH_PERFMON_EVENTSEL_EDGE);
        bool pc    = (config & ARCH_PERFMON_EVENTSEL_PIN_CONTROL);
        bool any   = (config & ARCH_PERFMON_EVENTSEL_ANY);
        bool inv   = (config & ARCH_PERFMON_EVENTSEL_INV);
        ssize_t ret;

        /*
        * We have whole page size to spend and just little data
        * to write, so we can safely use sprintf.
        */
        ret = sprintf(page, "event=0x%02llx", event);

        if (umask)
                ret += sprintf(page + ret, ",umask=0x%02llx", umask);

        if (edge)
                ret += sprintf(page + ret, ",edge");

        if (pc)
                ret += sprintf(page + ret, ",pc");

        if (any)
                ret += sprintf(page + ret, ",any");

        if (inv)
                ret += sprintf(page + ret, ",inv");

        if (cmask)
                ret += sprintf(page + ret, ",cmask=0x%02llx", cmask);

        ret += sprintf(page + ret, "\n");

        return ret;
}

static int __init init_hw_perf_events(void)
{
        struct x86_pmu_quirk *quirk;
        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:
                err = -ENOTSUPP;
        }
        if (err != 0) {
                pr_cont("no PMU driver, software events only.\n");
                return 0;
        }

        pmu_check_apic();

        /* sanity check that the hardware exists or is emulated */
        if (!check_hw_exists())
                return 0;

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

        x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */

        for (quirk = x86_pmu.quirks; quirk; quirk = quirk->next)
                quirk->func();

        if (!x86_pmu.intel_ctrl)
                x86_pmu.intel_ctrl = (1 << x86_pmu.num_counters) - 1;

        perf_events_lapic_init();
        register_nmi_handler(NMI_LOCAL, perf_event_nmi_handler, 0, "PMI");

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

        x86_pmu_format_group.attrs = x86_pmu.format_attrs;

        if (x86_pmu.event_attrs)
                x86_pmu_events_group.attrs = x86_pmu.event_attrs;

        if (!x86_pmu.events_sysfs_show)
                x86_pmu_events_group.attrs = &empty_attrs;
        else
                filter_events(x86_pmu_events_group.attrs);

        if (x86_pmu.cpu_events) {
                struct attribute **tmp;

                tmp = merge_attr(x86_pmu_events_group.attrs, x86_pmu.cpu_events);
                if (!WARN_ON(!tmp))
                        x86_pmu_events_group.attrs = tmp;
        }

        pr_info("... version:                %d\n",     x86_pmu.version);
        pr_info("... bit width:              %d\n",     x86_pmu.cntval_bits);
        pr_info("... generic registers:      %d\n",     x86_pmu.num_counters);
        pr_info("... value mask:             %016Lx\n", x86_pmu.cntval_mask);
        pr_info("... max period:             %016Lx\n", x86_pmu.max_period);
        pr_info("... fixed-purpose events:   %d\n",     x86_pmu.num_counters_fixed);
        pr_info("... event mask:             %016Lx\n", x86_pmu.intel_ctrl);

        perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);
        perf_cpu_notifier(x86_pmu_notifier);

        return 0;
}
early_initcall(init_hw_perf_events);

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

/*
 * Start group events scheduling transaction
 * Set the flag to make pmu::enable() not perform the
 * schedulability test, it will be performed at commit time
 *
 * We only support PERF_PMU_TXN_ADD transactions. Save the
 * transaction flags but otherwise ignore non-PERF_PMU_TXN_ADD
 * transactions.
 */
static void x86_pmu_start_txn(struct pmu *pmu, unsigned int txn_flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        WARN_ON_ONCE(cpuc->txn_flags);          /* txn already in flight */

        cpuc->txn_flags = txn_flags;
        if (txn_flags & ~PERF_PMU_TXN_ADD)
                return;

        perf_pmu_disable(pmu);
        __this_cpu_write(cpu_hw_events.n_txn, 0);
}

/*
 * Stop group events scheduling transaction
 * Clear the flag and pmu::enable() will perform the
 * schedulability test.
 */
static void x86_pmu_cancel_txn(struct pmu *pmu)
{
        unsigned int txn_flags;
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        WARN_ON_ONCE(!cpuc->txn_flags); /* no txn in flight */

        txn_flags = cpuc->txn_flags;
        cpuc->txn_flags = 0;
        if (txn_flags & ~PERF_PMU_TXN_ADD)
                return;

        /*
         * Truncate collected array by the number of events added in this
         * transaction. See x86_pmu_add() and x86_pmu_*_txn().
         */
        __this_cpu_sub(cpu_hw_events.n_added, __this_cpu_read(cpu_hw_events.n_txn));
        __this_cpu_sub(cpu_hw_events.n_events, __this_cpu_read(cpu_hw_events.n_txn));
        perf_pmu_enable(pmu);
}

/*
 * Commit group events scheduling transaction
 * Perform the group schedulability test as a whole
 * Return 0 if success
 *
 * Does not cancel the transaction on failure; expects the caller to do this.
 */
static int x86_pmu_commit_txn(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        int assign[X86_PMC_IDX_MAX];
        int n, ret;

        WARN_ON_ONCE(!cpuc->txn_flags); /* no txn in flight */

        if (cpuc->txn_flags & ~PERF_PMU_TXN_ADD) {
                cpuc->txn_flags = 0;
                return 0;
        }

        n = cpuc->n_events;

        if (!x86_pmu_initialized())
                return -EAGAIN;

        ret = x86_pmu.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->txn_flags = 0;
        perf_pmu_enable(pmu);
        return 0;
}
/*
 * a fake_cpuc is used to validate event groups. Due to
 * the extra reg logic, we need to also allocate a fake
 * per_core and per_cpu structure. Otherwise, group events
 * using extra reg may conflict without the kernel being
 * able to catch this when the last event gets added to
 * the group.
 */
static void free_fake_cpuc(struct cpu_hw_events *cpuc)
{
        kfree(cpuc->shared_regs);
        kfree(cpuc);
}

static struct cpu_hw_events *allocate_fake_cpuc(void)
{
        struct cpu_hw_events *cpuc;
        int cpu = raw_smp_processor_id();

        cpuc = kzalloc(sizeof(*cpuc), GFP_KERNEL);
        if (!cpuc)
                return ERR_PTR(-ENOMEM);

        /* only needed, if we have extra_regs */
        if (x86_pmu.extra_regs) {
                cpuc->shared_regs = allocate_shared_regs(cpu);
                if (!cpuc->shared_regs)
                        goto error;
        }
        cpuc->is_fake = 1;
        return cpuc;
error:
        free_fake_cpuc(cpuc);
        return ERR_PTR(-ENOMEM);
}

/*
 * validate that we can schedule this event
 */
static int validate_event(struct perf_event *event)
{
        struct cpu_hw_events *fake_cpuc;
        struct event_constraint *c;
        int ret = 0;

        fake_cpuc = allocate_fake_cpuc();
        if (IS_ERR(fake_cpuc))
                return PTR_ERR(fake_cpuc);

        c = x86_pmu.get_event_constraints(fake_cpuc, -1, event);

        if (!c || !c->weight)
                ret = -EINVAL;

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

        free_fake_cpuc(fake_cpuc);

        return ret;
}

/*
 * 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 = -EINVAL, n;

        fake_cpuc = allocate_fake_cpuc();
        if (IS_ERR(fake_cpuc))
                return PTR_ERR(fake_cpuc);
        /*
         * 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
         */
        n = collect_events(fake_cpuc, leader, true);
        if (n < 0)
                goto out;

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

        fake_cpuc->n_events = n;

        ret = x86_pmu.schedule_events(fake_cpuc, n, NULL);

out:
        free_fake_cpuc(fake_cpuc);
        return ret;
}

static int x86_pmu_event_init(struct perf_event *event)
{
        struct pmu *tmp;
        int err;

        switch (event->attr.type) {
        case PERF_TYPE_RAW:
        case PERF_TYPE_HARDWARE:
        case PERF_TYPE_HW_CACHE:
                break;

        default:
                return -ENOENT;
        }

        err = __x86_pmu_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);
                else
                        err = validate_event(event);

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

                        event->destroy(event);
        }

        if (ACCESS_ONCE(x86_pmu.attr_rdpmc))
                event->hw.flags |= PERF_X86_EVENT_RDPMC_ALLOWED;

        return err;
}

static void refresh_pce(void *ignored)
{
        if (current->mm)
                load_mm_cr4(current->mm);
}

static void x86_pmu_event_mapped(struct perf_event *event)
{
        if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
                return;

        if (atomic_inc_return(&current->mm->context.perf_rdpmc_allowed) == 1)
                on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
}

static void x86_pmu_event_unmapped(struct perf_event *event)
{
        if (!current->mm)
                return;

        if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
                return;

        if (atomic_dec_and_test(&current->mm->context.perf_rdpmc_allowed))
                on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
}

static int x86_pmu_event_idx(struct perf_event *event)
{
        int idx = event->hw.idx;

        if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
                return 0;

        if (x86_pmu.num_counters_fixed && idx >= INTEL_PMC_IDX_FIXED) {
                idx -= INTEL_PMC_IDX_FIXED;
                idx |= 1 << 30;
        }

        return idx + 1;
}

static ssize_t get_attr_rdpmc(struct device *cdev,
                              struct device_attribute *attr,
                              char *buf)
{
        return snprintf(buf, 40, "%d\n", x86_pmu.attr_rdpmc);
}

static ssize_t set_attr_rdpmc(struct device *cdev,
                              struct device_attribute *attr,
                              const char *buf, size_t count)
{
        unsigned long val;
        ssize_t ret;

        ret = kstrtoul(buf, 0, &val);
        if (ret)
                return ret;

        if (val > 2)
                return -EINVAL;

        if (x86_pmu.attr_rdpmc_broken)
                return -ENOTSUPP;

        if ((val == 2) != (x86_pmu.attr_rdpmc == 2)) {
                /*
                 * Changing into or out of always available, aka
                 * perf-event-bypassing mode.  This path is extremely slow,
                 * but only root can trigger it, so it's okay.
                 */
                if (val == 2)
                        static_key_slow_inc(&rdpmc_always_available);
                else
                        static_key_slow_dec(&rdpmc_always_available);
                on_each_cpu(refresh_pce, NULL, 1);
        }

        x86_pmu.attr_rdpmc = val;

        return count;
}

static DEVICE_ATTR(rdpmc, S_IRUSR | S_IWUSR, get_attr_rdpmc, set_attr_rdpmc);

static struct attribute *x86_pmu_attrs[] = {
        &dev_attr_rdpmc.attr,
        NULL,
};

static struct attribute_group x86_pmu_attr_group = {
        .attrs = x86_pmu_attrs,
};

static const struct attribute_group *x86_pmu_attr_groups[] = {
        &x86_pmu_attr_group,
        &x86_pmu_format_group,
        &x86_pmu_events_group,
        NULL,
};

static void x86_pmu_sched_task(struct perf_event_context *ctx, bool sched_in)
{
        if (x86_pmu.sched_task)
                x86_pmu.sched_task(ctx, sched_in);
}

void perf_check_microcode(void)
{
        if (x86_pmu.check_microcode)
                x86_pmu.check_microcode();
}
EXPORT_SYMBOL_GPL(perf_check_microcode);

static struct pmu pmu = {
        .pmu_enable             = x86_pmu_enable,
        .pmu_disable            = x86_pmu_disable,

        .attr_groups            = x86_pmu_attr_groups,

        .event_init             = x86_pmu_event_init,

        .event_mapped           = x86_pmu_event_mapped,
        .event_unmapped         = x86_pmu_event_unmapped,

        .add                    = x86_pmu_add,
        .del                    = x86_pmu_del,
        .start                  = x86_pmu_start,
        .stop                   = x86_pmu_stop,
        .read                   = x86_pmu_read,

        .start_txn              = x86_pmu_start_txn,
        .cancel_txn             = x86_pmu_cancel_txn,
        .commit_txn             = x86_pmu_commit_txn,

        .event_idx              = x86_pmu_event_idx,
        .sched_task             = x86_pmu_sched_task,
        .task_ctx_size          = sizeof(struct x86_perf_task_context),
};

void arch_perf_update_userpage(struct perf_event *event,
                               struct perf_event_mmap_page *userpg, u64 now)
{
        struct cyc2ns_data *data;

        userpg->cap_user_time = 0;
        userpg->cap_user_time_zero = 0;
        userpg->cap_user_rdpmc =
                !!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED);
        userpg->pmc_width = x86_pmu.cntval_bits;

        if (!sched_clock_stable())
                return;

        data = cyc2ns_read_begin();

        /*
         * Internal timekeeping for enabled/running/stopped times
         * is always in the local_clock domain.
         */
        userpg->cap_user_time = 1;
        userpg->time_mult = data->cyc2ns_mul;
        userpg->time_shift = data->cyc2ns_shift;
        userpg->time_offset = data->cyc2ns_offset - now;

        /*
         * cap_user_time_zero doesn't make sense when we're using a different
         * time base for the records.
         */
        if (event->clock == &local_clock) {
                userpg->cap_user_time_zero = 1;
                userpg->time_zero = data->cyc2ns_offset;
        }

        cyc2ns_read_end(data);
}

/*
 * callchain support
 */

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

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

        return perf_callchain_store(entry, addr);
}

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

void
perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
{
        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                /* TODO: We don't support guest os callchain now */
                return;
        }

        perf_callchain_store(entry, regs->ip);

        dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
}

static inline int
valid_user_frame(const void __user *fp, unsigned long size)
{
        return (__range_not_ok(fp, size, TASK_SIZE) == 0);
}

static unsigned long get_segment_base(unsigned int segment)
{
        struct desc_struct *desc;
        int idx = segment >> 3;

        if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) {
#ifdef CONFIG_MODIFY_LDT_SYSCALL
                struct ldt_struct *ldt;

                if (idx > LDT_ENTRIES)
                        return 0;

                /* IRQs are off, so this synchronizes with smp_store_release */
                ldt = lockless_dereference(current->active_mm->context.ldt);
                if (!ldt || idx > ldt->size)
                        return 0;

                desc = &ldt->entries[idx];
#else
                return 0;
#endif
        } else {
                if (idx > GDT_ENTRIES)
                        return 0;

                desc = raw_cpu_ptr(gdt_page.gdt) + idx;
        }

        return get_desc_base(desc);
}

#ifdef CONFIG_IA32_EMULATION

#include <asm/compat.h>

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

        if (!test_thread_flag(TIF_IA32))
                return 0;

        cs_base = get_segment_base(regs->cs);
        ss_base = get_segment_base(regs->ss);

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

                if (!access_ok(VERIFY_READ, fp, 8))
                        break;

                bytes = __copy_from_user_nmi(&frame.next_frame, fp, 4);
                if (bytes != 0)
                        break;
                bytes = __copy_from_user_nmi(&frame.return_address, fp+4, 4);
                if (bytes != 0)
                        break;

                if (!valid_user_frame(fp, sizeof(frame)))
                        break;

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

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

        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                /* TODO: We don't support guest os callchain now */
                return;
        }

        /*
         * We don't know what to do with VM86 stacks.. ignore them for now.
         */
        if (regs->flags & (X86_VM_MASK | PERF_EFLAGS_VM))
                return;

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

        perf_callchain_store(entry, regs->ip);

        if (!current->mm)
                return;

        if (perf_callchain_user32(regs, entry))
                return;

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

                if (!access_ok(VERIFY_READ, fp, 16))
                        break;

                bytes = __copy_from_user_nmi(&frame.next_frame, fp, 8);
                if (bytes != 0)
                        break;
                bytes = __copy_from_user_nmi(&frame.return_address, fp+8, 8);
                if (bytes != 0)
                        break;

                if (!valid_user_frame(fp, sizeof(frame)))
                        break;

                perf_callchain_store(entry, frame.return_address);
                fp = (void __user *)frame.next_frame;
        }
        pagefault_enable();
}

/*
 * Deal with code segment offsets for the various execution modes:
 *
 *   VM86 - the good olde 16 bit days, where the linear address is
 *          20 bits and we use regs->ip + 0x10 * regs->cs.
 *
 *   IA32 - Where we need to look at GDT/LDT segment descriptor tables
 *          to figure out what the 32bit base address is.
 *
 *    X32 - has TIF_X32 set, but is running in x86_64
 *
 * X86_64 - CS,DS,SS,ES are all zero based.
 */
static unsigned long code_segment_base(struct pt_regs *regs)
{
        /*
         * For IA32 we look at the GDT/LDT segment base to convert the
         * effective IP to a linear address.
         */

#ifdef CONFIG_X86_32
        /*
         * If we are in VM86 mode, add the segment offset to convert to a
         * linear address.
         */
        if (regs->flags & X86_VM_MASK)
                return 0x10 * regs->cs;

        if (user_mode(regs) && regs->cs != __USER_CS)
                return get_segment_base(regs->cs);
#else
        if (user_mode(regs) && !user_64bit_mode(regs) &&
            regs->cs != __USER32_CS)
                return get_segment_base(regs->cs);
#endif
        return 0;
}

unsigned long perf_instruction_pointer(struct pt_regs *regs)
{
        if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
                return perf_guest_cbs->get_guest_ip();

        return regs->ip + code_segment_base(regs);
}

unsigned long perf_misc_flags(struct pt_regs *regs)
{
        int misc = 0;

        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
                if (perf_guest_cbs->is_user_mode())
                        misc |= PERF_RECORD_MISC_GUEST_USER;
                else
                        misc |= PERF_RECORD_MISC_GUEST_KERNEL;
        } else {
                if (user_mode(regs))
                        misc |= PERF_RECORD_MISC_USER;
                else
                        misc |= PERF_RECORD_MISC_KERNEL;
        }

        if (regs->flags & PERF_EFLAGS_EXACT)
                misc |= PERF_RECORD_MISC_EXACT_IP;

        return misc;
}

void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
{
        cap->version            = x86_pmu.version;
        cap->num_counters_gp    = x86_pmu.num_counters;
        cap->num_counters_fixed = x86_pmu.num_counters_fixed;
        cap->bit_width_gp       = x86_pmu.cntval_bits;
        cap->bit_width_fixed    = x86_pmu.cntval_bits;
        cap->events_mask        = (unsigned int)x86_pmu.events_maskl;
        cap->events_mask_len    = x86_pmu.events_mask_len;
}
EXPORT_SYMBOL_GPL(perf_get_x86_pmu_capability);