RDMA/nes: don't leak skb if carrier down

[deliverable/linux.git] / arch / x86 / events / intel / lbr.c

#include <linux/perf_event.h>
#include <linux/types.h>

#include <asm/perf_event.h>
#include <asm/msr.h>
#include <asm/insn.h>

#include "../perf_event.h"

enum {
        LBR_FORMAT_32           = 0x00,
        LBR_FORMAT_LIP          = 0x01,
        LBR_FORMAT_EIP          = 0x02,
        LBR_FORMAT_EIP_FLAGS    = 0x03,
        LBR_FORMAT_EIP_FLAGS2   = 0x04,
        LBR_FORMAT_INFO         = 0x05,
        LBR_FORMAT_MAX_KNOWN    = LBR_FORMAT_INFO,
};

static enum {
        LBR_EIP_FLAGS           = 1,
        LBR_TSX                 = 2,
} lbr_desc[LBR_FORMAT_MAX_KNOWN + 1] = {
        [LBR_FORMAT_EIP_FLAGS]  = LBR_EIP_FLAGS,
        [LBR_FORMAT_EIP_FLAGS2] = LBR_EIP_FLAGS | LBR_TSX,
};

/*
 * Intel LBR_SELECT bits
 * Intel Vol3a, April 2011, Section 16.7 Table 16-10
 *
 * Hardware branch filter (not available on all CPUs)
 */
#define LBR_KERNEL_BIT          0 /* do not capture at ring0 */
#define LBR_USER_BIT            1 /* do not capture at ring > 0 */
#define LBR_JCC_BIT             2 /* do not capture conditional branches */
#define LBR_REL_CALL_BIT        3 /* do not capture relative calls */
#define LBR_IND_CALL_BIT        4 /* do not capture indirect calls */
#define LBR_RETURN_BIT          5 /* do not capture near returns */
#define LBR_IND_JMP_BIT         6 /* do not capture indirect jumps */
#define LBR_REL_JMP_BIT         7 /* do not capture relative jumps */
#define LBR_FAR_BIT             8 /* do not capture far branches */
#define LBR_CALL_STACK_BIT      9 /* enable call stack */

/*
 * Following bit only exists in Linux; we mask it out before writing it to
 * the actual MSR. But it helps the constraint perf code to understand
 * that this is a separate configuration.
 */
#define LBR_NO_INFO_BIT        63 /* don't read LBR_INFO. */

#define LBR_KERNEL      (1 << LBR_KERNEL_BIT)
#define LBR_USER        (1 << LBR_USER_BIT)
#define LBR_JCC         (1 << LBR_JCC_BIT)
#define LBR_REL_CALL    (1 << LBR_REL_CALL_BIT)
#define LBR_IND_CALL    (1 << LBR_IND_CALL_BIT)
#define LBR_RETURN      (1 << LBR_RETURN_BIT)
#define LBR_REL_JMP     (1 << LBR_REL_JMP_BIT)
#define LBR_IND_JMP     (1 << LBR_IND_JMP_BIT)
#define LBR_FAR         (1 << LBR_FAR_BIT)
#define LBR_CALL_STACK  (1 << LBR_CALL_STACK_BIT)
#define LBR_NO_INFO     (1ULL << LBR_NO_INFO_BIT)

#define LBR_PLM (LBR_KERNEL | LBR_USER)

#define LBR_SEL_MASK    0x1ff   /* valid bits in LBR_SELECT */
#define LBR_NOT_SUPP    -1      /* LBR filter not supported */
#define LBR_IGN         0       /* ignored */

#define LBR_ANY          \
        (LBR_JCC        |\
         LBR_REL_CALL   |\
         LBR_IND_CALL   |\
         LBR_RETURN     |\
         LBR_REL_JMP    |\
         LBR_IND_JMP    |\
         LBR_FAR)

#define LBR_FROM_FLAG_MISPRED  (1ULL << 63)
#define LBR_FROM_FLAG_IN_TX    (1ULL << 62)
#define LBR_FROM_FLAG_ABORT    (1ULL << 61)

/*
 * x86control flow change classification
 * x86control flow changes include branches, interrupts, traps, faults
 */
enum {
        X86_BR_NONE             = 0,      /* unknown */

        X86_BR_USER             = 1 << 0, /* branch target is user */
        X86_BR_KERNEL           = 1 << 1, /* branch target is kernel */

        X86_BR_CALL             = 1 << 2, /* call */
        X86_BR_RET              = 1 << 3, /* return */
        X86_BR_SYSCALL          = 1 << 4, /* syscall */
        X86_BR_SYSRET           = 1 << 5, /* syscall return */
        X86_BR_INT              = 1 << 6, /* sw interrupt */
        X86_BR_IRET             = 1 << 7, /* return from interrupt */
        X86_BR_JCC              = 1 << 8, /* conditional */
        X86_BR_JMP              = 1 << 9, /* jump */
        X86_BR_IRQ              = 1 << 10,/* hw interrupt or trap or fault */
        X86_BR_IND_CALL         = 1 << 11,/* indirect calls */
        X86_BR_ABORT            = 1 << 12,/* transaction abort */
        X86_BR_IN_TX            = 1 << 13,/* in transaction */
        X86_BR_NO_TX            = 1 << 14,/* not in transaction */
        X86_BR_ZERO_CALL        = 1 << 15,/* zero length call */
        X86_BR_CALL_STACK       = 1 << 16,/* call stack */
        X86_BR_IND_JMP          = 1 << 17,/* indirect jump */
};

#define X86_BR_PLM (X86_BR_USER | X86_BR_KERNEL)
#define X86_BR_ANYTX (X86_BR_NO_TX | X86_BR_IN_TX)

#define X86_BR_ANY       \
        (X86_BR_CALL    |\
         X86_BR_RET     |\
         X86_BR_SYSCALL |\
         X86_BR_SYSRET  |\
         X86_BR_INT     |\
         X86_BR_IRET    |\
         X86_BR_JCC     |\
         X86_BR_JMP      |\
         X86_BR_IRQ      |\
         X86_BR_ABORT    |\
         X86_BR_IND_CALL |\
         X86_BR_IND_JMP  |\
         X86_BR_ZERO_CALL)

#define X86_BR_ALL (X86_BR_PLM | X86_BR_ANY)

#define X86_BR_ANY_CALL          \
        (X86_BR_CALL            |\
         X86_BR_IND_CALL        |\
         X86_BR_ZERO_CALL       |\
         X86_BR_SYSCALL         |\
         X86_BR_IRQ             |\
         X86_BR_INT)

static void intel_pmu_lbr_filter(struct cpu_hw_events *cpuc);

/*
 * We only support LBR implementations that have FREEZE_LBRS_ON_PMI
 * otherwise it becomes near impossible to get a reliable stack.
 */

static void __intel_pmu_lbr_enable(bool pmi)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        u64 debugctl, lbr_select = 0, orig_debugctl;

        /*
         * No need to unfreeze manually, as v4 can do that as part
         * of the GLOBAL_STATUS ack.
         */
        if (pmi && x86_pmu.version >= 4)
                return;

        /*
         * No need to reprogram LBR_SELECT in a PMI, as it
         * did not change.
         */
        if (cpuc->lbr_sel)
                lbr_select = cpuc->lbr_sel->config & x86_pmu.lbr_sel_mask;
        if (!pmi && cpuc->lbr_sel)
                wrmsrl(MSR_LBR_SELECT, lbr_select);

        rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
        orig_debugctl = debugctl;
        debugctl |= DEBUGCTLMSR_LBR;
        /*
         * LBR callstack does not work well with FREEZE_LBRS_ON_PMI.
         * If FREEZE_LBRS_ON_PMI is set, PMI near call/return instructions
         * may cause superfluous increase/decrease of LBR_TOS.
         */
        if (!(lbr_select & LBR_CALL_STACK))
                debugctl |= DEBUGCTLMSR_FREEZE_LBRS_ON_PMI;
        if (orig_debugctl != debugctl)
                wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}

static void __intel_pmu_lbr_disable(void)
{
        u64 debugctl;

        rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
        debugctl &= ~(DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
        wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}

static void intel_pmu_lbr_reset_32(void)
{
        int i;

        for (i = 0; i < x86_pmu.lbr_nr; i++)
                wrmsrl(x86_pmu.lbr_from + i, 0);
}

static void intel_pmu_lbr_reset_64(void)
{
        int i;

        for (i = 0; i < x86_pmu.lbr_nr; i++) {
                wrmsrl(x86_pmu.lbr_from + i, 0);
                wrmsrl(x86_pmu.lbr_to   + i, 0);
                if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
                        wrmsrl(MSR_LBR_INFO_0 + i, 0);
        }
}

void intel_pmu_lbr_reset(void)
{
        if (!x86_pmu.lbr_nr)
                return;

        if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_32)
                intel_pmu_lbr_reset_32();
        else
                intel_pmu_lbr_reset_64();
}

/*
 * TOS = most recently recorded branch
 */
static inline u64 intel_pmu_lbr_tos(void)
{
        u64 tos;

        rdmsrl(x86_pmu.lbr_tos, tos);
        return tos;
}

enum {
        LBR_NONE,
        LBR_VALID,
};

static void __intel_pmu_lbr_restore(struct x86_perf_task_context *task_ctx)
{
        int i;
        unsigned lbr_idx, mask;
        u64 tos;

        if (task_ctx->lbr_callstack_users == 0 ||
            task_ctx->lbr_stack_state == LBR_NONE) {
                intel_pmu_lbr_reset();
                return;
        }

        mask = x86_pmu.lbr_nr - 1;
        tos = task_ctx->tos;
        for (i = 0; i < tos; i++) {
                lbr_idx = (tos - i) & mask;
                wrmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
                wrmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
                if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
                        wrmsrl(MSR_LBR_INFO_0 + lbr_idx, task_ctx->lbr_info[i]);
        }
        wrmsrl(x86_pmu.lbr_tos, tos);
        task_ctx->lbr_stack_state = LBR_NONE;
}

static void __intel_pmu_lbr_save(struct x86_perf_task_context *task_ctx)
{
        int i;
        unsigned lbr_idx, mask;
        u64 tos;

        if (task_ctx->lbr_callstack_users == 0) {
                task_ctx->lbr_stack_state = LBR_NONE;
                return;
        }

        mask = x86_pmu.lbr_nr - 1;
        tos = intel_pmu_lbr_tos();
        for (i = 0; i < tos; i++) {
                lbr_idx = (tos - i) & mask;
                rdmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
                rdmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
                if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO)
                        rdmsrl(MSR_LBR_INFO_0 + lbr_idx, task_ctx->lbr_info[i]);
        }
        task_ctx->tos = tos;
        task_ctx->lbr_stack_state = LBR_VALID;
}

void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct x86_perf_task_context *task_ctx;

        /*
         * If LBR callstack feature is enabled and the stack was saved when
         * the task was scheduled out, restore the stack. Otherwise flush
         * the LBR stack.
         */
        task_ctx = ctx ? ctx->task_ctx_data : NULL;
        if (task_ctx) {
                if (sched_in) {
                        __intel_pmu_lbr_restore(task_ctx);
                        cpuc->lbr_context = ctx;
                } else {
                        __intel_pmu_lbr_save(task_ctx);
                }
                return;
        }

        /*
         * When sampling the branck stack in system-wide, it may be
         * necessary to flush the stack on context switch. This happens
         * when the branch stack does not tag its entries with the pid
         * of the current task. Otherwise it becomes impossible to
         * associate a branch entry with a task. This ambiguity is more
         * likely to appear when the branch stack supports priv level
         * filtering and the user sets it to monitor only at the user
         * level (which could be a useful measurement in system-wide
         * mode). In that case, the risk is high of having a branch
         * stack with branch from multiple tasks.
         */
        if (sched_in) {
                intel_pmu_lbr_reset();
                cpuc->lbr_context = ctx;
        }
}

static inline bool branch_user_callstack(unsigned br_sel)
{
        return (br_sel & X86_BR_USER) && (br_sel & X86_BR_CALL_STACK);
}

void intel_pmu_lbr_enable(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct x86_perf_task_context *task_ctx;

        if (!x86_pmu.lbr_nr)
                return;

        /*
         * Reset the LBR stack if we changed task context to
         * avoid data leaks.
         */
        if (event->ctx->task && cpuc->lbr_context != event->ctx) {
                intel_pmu_lbr_reset();
                cpuc->lbr_context = event->ctx;
        }
        cpuc->br_sel = event->hw.branch_reg.reg;

        if (branch_user_callstack(cpuc->br_sel) && event->ctx &&
                                        event->ctx->task_ctx_data) {
                task_ctx = event->ctx->task_ctx_data;
                task_ctx->lbr_callstack_users++;
        }

        cpuc->lbr_users++;
        perf_sched_cb_inc(event->ctx->pmu);
}

void intel_pmu_lbr_disable(struct perf_event *event)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct x86_perf_task_context *task_ctx;

        if (!x86_pmu.lbr_nr)
                return;

        if (branch_user_callstack(cpuc->br_sel) && event->ctx &&
                                        event->ctx->task_ctx_data) {
                task_ctx = event->ctx->task_ctx_data;
                task_ctx->lbr_callstack_users--;
        }

        cpuc->lbr_users--;
        WARN_ON_ONCE(cpuc->lbr_users < 0);
        perf_sched_cb_dec(event->ctx->pmu);

        if (cpuc->enabled && !cpuc->lbr_users) {
                __intel_pmu_lbr_disable();
                /* avoid stale pointer */
                cpuc->lbr_context = NULL;
        }
}

void intel_pmu_lbr_enable_all(bool pmi)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (cpuc->lbr_users)
                __intel_pmu_lbr_enable(pmi);
}

void intel_pmu_lbr_disable_all(void)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (cpuc->lbr_users)
                __intel_pmu_lbr_disable();
}

static void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)
{
        unsigned long mask = x86_pmu.lbr_nr - 1;
        u64 tos = intel_pmu_lbr_tos();
        int i;

        for (i = 0; i < x86_pmu.lbr_nr; i++) {
                unsigned long lbr_idx = (tos - i) & mask;
                union {
                        struct {
                                u32 from;
                                u32 to;
                        };
                        u64     lbr;
                } msr_lastbranch;

                rdmsrl(x86_pmu.lbr_from + lbr_idx, msr_lastbranch.lbr);

                cpuc->lbr_entries[i].from       = msr_lastbranch.from;
                cpuc->lbr_entries[i].to         = msr_lastbranch.to;
                cpuc->lbr_entries[i].mispred    = 0;
                cpuc->lbr_entries[i].predicted  = 0;
                cpuc->lbr_entries[i].reserved   = 0;
        }
        cpuc->lbr_stack.nr = i;
}

/*
 * Due to lack of segmentation in Linux the effective address (offset)
 * is the same as the linear address, allowing us to merge the LIP and EIP
 * LBR formats.
 */
static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
{
        bool need_info = false;
        unsigned long mask = x86_pmu.lbr_nr - 1;
        int lbr_format = x86_pmu.intel_cap.lbr_format;
        u64 tos = intel_pmu_lbr_tos();
        int i;
        int out = 0;
        int num = x86_pmu.lbr_nr;

        if (cpuc->lbr_sel) {
                need_info = !(cpuc->lbr_sel->config & LBR_NO_INFO);
                if (cpuc->lbr_sel->config & LBR_CALL_STACK)
                        num = tos;
        }

        for (i = 0; i < num; i++) {
                unsigned long lbr_idx = (tos - i) & mask;
                u64 from, to, mis = 0, pred = 0, in_tx = 0, abort = 0;
                int skip = 0;
                u16 cycles = 0;
                int lbr_flags = lbr_desc[lbr_format];

                rdmsrl(x86_pmu.lbr_from + lbr_idx, from);
                rdmsrl(x86_pmu.lbr_to   + lbr_idx, to);

                if (lbr_format == LBR_FORMAT_INFO && need_info) {
                        u64 info;

                        rdmsrl(MSR_LBR_INFO_0 + lbr_idx, info);
                        mis = !!(info & LBR_INFO_MISPRED);
                        pred = !mis;
                        in_tx = !!(info & LBR_INFO_IN_TX);
                        abort = !!(info & LBR_INFO_ABORT);
                        cycles = (info & LBR_INFO_CYCLES);
                }
                if (lbr_flags & LBR_EIP_FLAGS) {
                        mis = !!(from & LBR_FROM_FLAG_MISPRED);
                        pred = !mis;
                        skip = 1;
                }
                if (lbr_flags & LBR_TSX) {
                        in_tx = !!(from & LBR_FROM_FLAG_IN_TX);
                        abort = !!(from & LBR_FROM_FLAG_ABORT);
                        skip = 3;
                }
                from = (u64)((((s64)from) << skip) >> skip);

                /*
                 * Some CPUs report duplicated abort records,
                 * with the second entry not having an abort bit set.
                 * Skip them here. This loop runs backwards,
                 * so we need to undo the previous record.
                 * If the abort just happened outside the window
                 * the extra entry cannot be removed.
                 */
                if (abort && x86_pmu.lbr_double_abort && out > 0)
                        out--;

                cpuc->lbr_entries[out].from      = from;
                cpuc->lbr_entries[out].to        = to;
                cpuc->lbr_entries[out].mispred   = mis;
                cpuc->lbr_entries[out].predicted = pred;
                cpuc->lbr_entries[out].in_tx     = in_tx;
                cpuc->lbr_entries[out].abort     = abort;
                cpuc->lbr_entries[out].cycles    = cycles;
                cpuc->lbr_entries[out].reserved  = 0;
                out++;
        }
        cpuc->lbr_stack.nr = out;
}

void intel_pmu_lbr_read(void)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (!cpuc->lbr_users)
                return;

        if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_32)
                intel_pmu_lbr_read_32(cpuc);
        else
                intel_pmu_lbr_read_64(cpuc);

        intel_pmu_lbr_filter(cpuc);
}

/*
 * SW filter is used:
 * - in case there is no HW filter
 * - in case the HW filter has errata or limitations
 */
static int intel_pmu_setup_sw_lbr_filter(struct perf_event *event)
{
        u64 br_type = event->attr.branch_sample_type;
        int mask = 0;

        if (br_type & PERF_SAMPLE_BRANCH_USER)
                mask |= X86_BR_USER;

        if (br_type & PERF_SAMPLE_BRANCH_KERNEL)
                mask |= X86_BR_KERNEL;

        /* we ignore BRANCH_HV here */

        if (br_type & PERF_SAMPLE_BRANCH_ANY)
                mask |= X86_BR_ANY;

        if (br_type & PERF_SAMPLE_BRANCH_ANY_CALL)
                mask |= X86_BR_ANY_CALL;

        if (br_type & PERF_SAMPLE_BRANCH_ANY_RETURN)
                mask |= X86_BR_RET | X86_BR_IRET | X86_BR_SYSRET;

        if (br_type & PERF_SAMPLE_BRANCH_IND_CALL)
                mask |= X86_BR_IND_CALL;

        if (br_type & PERF_SAMPLE_BRANCH_ABORT_TX)
                mask |= X86_BR_ABORT;

        if (br_type & PERF_SAMPLE_BRANCH_IN_TX)
                mask |= X86_BR_IN_TX;

        if (br_type & PERF_SAMPLE_BRANCH_NO_TX)
                mask |= X86_BR_NO_TX;

        if (br_type & PERF_SAMPLE_BRANCH_COND)
                mask |= X86_BR_JCC;

        if (br_type & PERF_SAMPLE_BRANCH_CALL_STACK) {
                if (!x86_pmu_has_lbr_callstack())
                        return -EOPNOTSUPP;
                if (mask & ~(X86_BR_USER | X86_BR_KERNEL))
                        return -EINVAL;
                mask |= X86_BR_CALL | X86_BR_IND_CALL | X86_BR_RET |
                        X86_BR_CALL_STACK;
        }

        if (br_type & PERF_SAMPLE_BRANCH_IND_JUMP)
                mask |= X86_BR_IND_JMP;

        if (br_type & PERF_SAMPLE_BRANCH_CALL)
                mask |= X86_BR_CALL | X86_BR_ZERO_CALL;
        /*
         * stash actual user request into reg, it may
         * be used by fixup code for some CPU
         */
        event->hw.branch_reg.reg = mask;
        return 0;
}

/*
 * setup the HW LBR filter
 * Used only when available, may not be enough to disambiguate
 * all branches, may need the help of the SW filter
 */
static int intel_pmu_setup_hw_lbr_filter(struct perf_event *event)
{
        struct hw_perf_event_extra *reg;
        u64 br_type = event->attr.branch_sample_type;
        u64 mask = 0, v;
        int i;

        for (i = 0; i < PERF_SAMPLE_BRANCH_MAX_SHIFT; i++) {
                if (!(br_type & (1ULL << i)))
                        continue;

                v = x86_pmu.lbr_sel_map[i];
                if (v == LBR_NOT_SUPP)
                        return -EOPNOTSUPP;

                if (v != LBR_IGN)
                        mask |= v;
        }

        reg = &event->hw.branch_reg;
        reg->idx = EXTRA_REG_LBR;

        /*
         * The first 9 bits (LBR_SEL_MASK) in LBR_SELECT operate
         * in suppress mode. So LBR_SELECT should be set to
         * (~mask & LBR_SEL_MASK) | (mask & ~LBR_SEL_MASK)
         */
        reg->config = mask ^ x86_pmu.lbr_sel_mask;

        if ((br_type & PERF_SAMPLE_BRANCH_NO_CYCLES) &&
            (br_type & PERF_SAMPLE_BRANCH_NO_FLAGS) &&
            (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_INFO))
                reg->config |= LBR_NO_INFO;

        return 0;
}

int intel_pmu_setup_lbr_filter(struct perf_event *event)
{
        int ret = 0;

        /*
         * no LBR on this PMU
         */
        if (!x86_pmu.lbr_nr)
                return -EOPNOTSUPP;

        /*
         * setup SW LBR filter
         */
        ret = intel_pmu_setup_sw_lbr_filter(event);
        if (ret)
                return ret;

        /*
         * setup HW LBR filter, if any
         */
        if (x86_pmu.lbr_sel_map)
                ret = intel_pmu_setup_hw_lbr_filter(event);

        return ret;
}

/*
 * return the type of control flow change at address "from"
 * instruction is not necessarily a branch (in case of interrupt).
 *
 * The branch type returned also includes the priv level of the
 * target of the control flow change (X86_BR_USER, X86_BR_KERNEL).
 *
 * If a branch type is unknown OR the instruction cannot be
 * decoded (e.g., text page not present), then X86_BR_NONE is
 * returned.
 */
static int branch_type(unsigned long from, unsigned long to, int abort)
{
        struct insn insn;
        void *addr;
        int bytes_read, bytes_left;
        int ret = X86_BR_NONE;
        int ext, to_plm, from_plm;
        u8 buf[MAX_INSN_SIZE];
        int is64 = 0;

        to_plm = kernel_ip(to) ? X86_BR_KERNEL : X86_BR_USER;
        from_plm = kernel_ip(from) ? X86_BR_KERNEL : X86_BR_USER;

        /*
         * maybe zero if lbr did not fill up after a reset by the time
         * we get a PMU interrupt
         */
        if (from == 0 || to == 0)
                return X86_BR_NONE;

        if (abort)
                return X86_BR_ABORT | to_plm;

        if (from_plm == X86_BR_USER) {
                /*
                 * can happen if measuring at the user level only
                 * and we interrupt in a kernel thread, e.g., idle.
                 */
                if (!current->mm)
                        return X86_BR_NONE;

                /* may fail if text not present */
                bytes_left = copy_from_user_nmi(buf, (void __user *)from,
                                                MAX_INSN_SIZE);
                bytes_read = MAX_INSN_SIZE - bytes_left;
                if (!bytes_read)
                        return X86_BR_NONE;

                addr = buf;
        } else {
                /*
                 * The LBR logs any address in the IP, even if the IP just
                 * faulted. This means userspace can control the from address.
                 * Ensure we don't blindy read any address by validating it is
                 * a known text address.
                 */
                if (kernel_text_address(from)) {
                        addr = (void *)from;
                        /*
                         * Assume we can get the maximum possible size
                         * when grabbing kernel data.  This is not
                         * _strictly_ true since we could possibly be
                         * executing up next to a memory hole, but
                         * it is very unlikely to be a problem.
                         */
                        bytes_read = MAX_INSN_SIZE;
                } else {
                        return X86_BR_NONE;
                }
        }

        /*
         * decoder needs to know the ABI especially
         * on 64-bit systems running 32-bit apps
         */
#ifdef CONFIG_X86_64
        is64 = kernel_ip((unsigned long)addr) || !test_thread_flag(TIF_IA32);
#endif
        insn_init(&insn, addr, bytes_read, is64);
        insn_get_opcode(&insn);
        if (!insn.opcode.got)
                return X86_BR_ABORT;

        switch (insn.opcode.bytes[0]) {
        case 0xf:
                switch (insn.opcode.bytes[1]) {
                case 0x05: /* syscall */
                case 0x34: /* sysenter */
                        ret = X86_BR_SYSCALL;
                        break;
                case 0x07: /* sysret */
                case 0x35: /* sysexit */
                        ret = X86_BR_SYSRET;
                        break;
                case 0x80 ... 0x8f: /* conditional */
                        ret = X86_BR_JCC;
                        break;
                default:
                        ret = X86_BR_NONE;
                }
                break;
        case 0x70 ... 0x7f: /* conditional */
                ret = X86_BR_JCC;
                break;
        case 0xc2: /* near ret */
        case 0xc3: /* near ret */
        case 0xca: /* far ret */
        case 0xcb: /* far ret */
                ret = X86_BR_RET;
                break;
        case 0xcf: /* iret */
                ret = X86_BR_IRET;
                break;
        case 0xcc ... 0xce: /* int */
                ret = X86_BR_INT;
                break;
        case 0xe8: /* call near rel */
                insn_get_immediate(&insn);
                if (insn.immediate1.value == 0) {
                        /* zero length call */
                        ret = X86_BR_ZERO_CALL;
                        break;
                }
        case 0x9a: /* call far absolute */
                ret = X86_BR_CALL;
                break;
        case 0xe0 ... 0xe3: /* loop jmp */
                ret = X86_BR_JCC;
                break;
        case 0xe9 ... 0xeb: /* jmp */
                ret = X86_BR_JMP;
                break;
        case 0xff: /* call near absolute, call far absolute ind */
                insn_get_modrm(&insn);
                ext = (insn.modrm.bytes[0] >> 3) & 0x7;
                switch (ext) {
                case 2: /* near ind call */
                case 3: /* far ind call */
                        ret = X86_BR_IND_CALL;
                        break;
                case 4:
                case 5:
                        ret = X86_BR_IND_JMP;
                        break;
                }
                break;
        default:
                ret = X86_BR_NONE;
        }
        /*
         * interrupts, traps, faults (and thus ring transition) may
         * occur on any instructions. Thus, to classify them correctly,
         * we need to first look at the from and to priv levels. If they
         * are different and to is in the kernel, then it indicates
         * a ring transition. If the from instruction is not a ring
         * transition instr (syscall, systenter, int), then it means
         * it was a irq, trap or fault.
         *
         * we have no way of detecting kernel to kernel faults.
         */
        if (from_plm == X86_BR_USER && to_plm == X86_BR_KERNEL
            && ret != X86_BR_SYSCALL && ret != X86_BR_INT)
                ret = X86_BR_IRQ;

        /*
         * branch priv level determined by target as
         * is done by HW when LBR_SELECT is implemented
         */
        if (ret != X86_BR_NONE)
                ret |= to_plm;

        return ret;
}

/*
 * implement actual branch filter based on user demand.
 * Hardware may not exactly satisfy that request, thus
 * we need to inspect opcodes. Mismatched branches are
 * discarded. Therefore, the number of branches returned
 * in PERF_SAMPLE_BRANCH_STACK sample may vary.
 */
static void
intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
{
        u64 from, to;
        int br_sel = cpuc->br_sel;
        int i, j, type;
        bool compress = false;

        /* if sampling all branches, then nothing to filter */
        if ((br_sel & X86_BR_ALL) == X86_BR_ALL)
                return;

        for (i = 0; i < cpuc->lbr_stack.nr; i++) {

                from = cpuc->lbr_entries[i].from;
                to = cpuc->lbr_entries[i].to;

                type = branch_type(from, to, cpuc->lbr_entries[i].abort);
                if (type != X86_BR_NONE && (br_sel & X86_BR_ANYTX)) {
                        if (cpuc->lbr_entries[i].in_tx)
                                type |= X86_BR_IN_TX;
                        else
                                type |= X86_BR_NO_TX;
                }

                /* if type does not correspond, then discard */
                if (type == X86_BR_NONE || (br_sel & type) != type) {
                        cpuc->lbr_entries[i].from = 0;
                        compress = true;
                }
        }

        if (!compress)
                return;

        /* remove all entries with from=0 */
        for (i = 0; i < cpuc->lbr_stack.nr; ) {
                if (!cpuc->lbr_entries[i].from) {
                        j = i;
                        while (++j < cpuc->lbr_stack.nr)
                                cpuc->lbr_entries[j-1] = cpuc->lbr_entries[j];
                        cpuc->lbr_stack.nr--;
                        if (!cpuc->lbr_entries[i].from)
                                continue;
                }
                i++;
        }
}

/*
 * Map interface branch filters onto LBR filters
 */
static const int nhm_lbr_sel_map[PERF_SAMPLE_BRANCH_MAX_SHIFT] = {
        [PERF_SAMPLE_BRANCH_ANY_SHIFT]          = LBR_ANY,
        [PERF_SAMPLE_BRANCH_USER_SHIFT]         = LBR_USER,
        [PERF_SAMPLE_BRANCH_KERNEL_SHIFT]       = LBR_KERNEL,
        [PERF_SAMPLE_BRANCH_HV_SHIFT]           = LBR_IGN,
        [PERF_SAMPLE_BRANCH_ANY_RETURN_SHIFT]   = LBR_RETURN | LBR_REL_JMP
                                                | LBR_IND_JMP | LBR_FAR,
        /*
         * NHM/WSM erratum: must include REL_JMP+IND_JMP to get CALL branches
         */
        [PERF_SAMPLE_BRANCH_ANY_CALL_SHIFT] =
         LBR_REL_CALL | LBR_IND_CALL | LBR_REL_JMP | LBR_IND_JMP | LBR_FAR,
        /*
         * NHM/WSM erratum: must include IND_JMP to capture IND_CALL
         */
        [PERF_SAMPLE_BRANCH_IND_CALL_SHIFT] = LBR_IND_CALL | LBR_IND_JMP,
        [PERF_SAMPLE_BRANCH_COND_SHIFT]     = LBR_JCC,
        [PERF_SAMPLE_BRANCH_IND_JUMP_SHIFT] = LBR_IND_JMP,
};

static const int snb_lbr_sel_map[PERF_SAMPLE_BRANCH_MAX_SHIFT] = {
        [PERF_SAMPLE_BRANCH_ANY_SHIFT]          = LBR_ANY,
        [PERF_SAMPLE_BRANCH_USER_SHIFT]         = LBR_USER,
        [PERF_SAMPLE_BRANCH_KERNEL_SHIFT]       = LBR_KERNEL,
        [PERF_SAMPLE_BRANCH_HV_SHIFT]           = LBR_IGN,
        [PERF_SAMPLE_BRANCH_ANY_RETURN_SHIFT]   = LBR_RETURN | LBR_FAR,
        [PERF_SAMPLE_BRANCH_ANY_CALL_SHIFT]     = LBR_REL_CALL | LBR_IND_CALL
                                                | LBR_FAR,
        [PERF_SAMPLE_BRANCH_IND_CALL_SHIFT]     = LBR_IND_CALL,
        [PERF_SAMPLE_BRANCH_COND_SHIFT]         = LBR_JCC,
        [PERF_SAMPLE_BRANCH_IND_JUMP_SHIFT]     = LBR_IND_JMP,
        [PERF_SAMPLE_BRANCH_CALL_SHIFT]         = LBR_REL_CALL,
};

static const int hsw_lbr_sel_map[PERF_SAMPLE_BRANCH_MAX_SHIFT] = {
        [PERF_SAMPLE_BRANCH_ANY_SHIFT]          = LBR_ANY,
        [PERF_SAMPLE_BRANCH_USER_SHIFT]         = LBR_USER,
        [PERF_SAMPLE_BRANCH_KERNEL_SHIFT]       = LBR_KERNEL,
        [PERF_SAMPLE_BRANCH_HV_SHIFT]           = LBR_IGN,
        [PERF_SAMPLE_BRANCH_ANY_RETURN_SHIFT]   = LBR_RETURN | LBR_FAR,
        [PERF_SAMPLE_BRANCH_ANY_CALL_SHIFT]     = LBR_REL_CALL | LBR_IND_CALL
                                                | LBR_FAR,
        [PERF_SAMPLE_BRANCH_IND_CALL_SHIFT]     = LBR_IND_CALL,
        [PERF_SAMPLE_BRANCH_COND_SHIFT]         = LBR_JCC,
        [PERF_SAMPLE_BRANCH_CALL_STACK_SHIFT]   = LBR_REL_CALL | LBR_IND_CALL
                                                | LBR_RETURN | LBR_CALL_STACK,
        [PERF_SAMPLE_BRANCH_IND_JUMP_SHIFT]     = LBR_IND_JMP,
        [PERF_SAMPLE_BRANCH_CALL_SHIFT]         = LBR_REL_CALL,
};

/* core */
void __init intel_pmu_lbr_init_core(void)
{
        x86_pmu.lbr_nr     = 4;
        x86_pmu.lbr_tos    = MSR_LBR_TOS;
        x86_pmu.lbr_from   = MSR_LBR_CORE_FROM;
        x86_pmu.lbr_to     = MSR_LBR_CORE_TO;

        /*
         * SW branch filter usage:
         * - compensate for lack of HW filter
         */
        pr_cont("4-deep LBR, ");
}

/* nehalem/westmere */
void __init intel_pmu_lbr_init_nhm(void)
{
        x86_pmu.lbr_nr     = 16;
        x86_pmu.lbr_tos    = MSR_LBR_TOS;
        x86_pmu.lbr_from   = MSR_LBR_NHM_FROM;
        x86_pmu.lbr_to     = MSR_LBR_NHM_TO;

        x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
        x86_pmu.lbr_sel_map  = nhm_lbr_sel_map;

        /*
         * SW branch filter usage:
         * - workaround LBR_SEL errata (see above)
         * - support syscall, sysret capture.
         *   That requires LBR_FAR but that means far
         *   jmp need to be filtered out
         */
        pr_cont("16-deep LBR, ");
}

/* sandy bridge */
void __init intel_pmu_lbr_init_snb(void)
{
        x86_pmu.lbr_nr   = 16;
        x86_pmu.lbr_tos  = MSR_LBR_TOS;
        x86_pmu.lbr_from = MSR_LBR_NHM_FROM;
        x86_pmu.lbr_to   = MSR_LBR_NHM_TO;

        x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
        x86_pmu.lbr_sel_map  = snb_lbr_sel_map;

        /*
         * SW branch filter usage:
         * - support syscall, sysret capture.
         *   That requires LBR_FAR but that means far
         *   jmp need to be filtered out
         */
        pr_cont("16-deep LBR, ");
}

/* haswell */
void intel_pmu_lbr_init_hsw(void)
{
        x86_pmu.lbr_nr   = 16;
        x86_pmu.lbr_tos  = MSR_LBR_TOS;
        x86_pmu.lbr_from = MSR_LBR_NHM_FROM;
        x86_pmu.lbr_to   = MSR_LBR_NHM_TO;

        x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
        x86_pmu.lbr_sel_map  = hsw_lbr_sel_map;

        pr_cont("16-deep LBR, ");
}

/* skylake */
__init void intel_pmu_lbr_init_skl(void)
{
        x86_pmu.lbr_nr   = 32;
        x86_pmu.lbr_tos  = MSR_LBR_TOS;
        x86_pmu.lbr_from = MSR_LBR_NHM_FROM;
        x86_pmu.lbr_to   = MSR_LBR_NHM_TO;

        x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
        x86_pmu.lbr_sel_map  = hsw_lbr_sel_map;

        /*
         * SW branch filter usage:
         * - support syscall, sysret capture.
         *   That requires LBR_FAR but that means far
         *   jmp need to be filtered out
         */
        pr_cont("32-deep LBR, ");
}

/* atom */
void __init intel_pmu_lbr_init_atom(void)
{
        /*
         * only models starting at stepping 10 seems
         * to have an operational LBR which can freeze
         * on PMU interrupt
         */
        if (boot_cpu_data.x86_model == 28
            && boot_cpu_data.x86_mask < 10) {
                pr_cont("LBR disabled due to erratum");
                return;
        }

        x86_pmu.lbr_nr     = 8;
        x86_pmu.lbr_tos    = MSR_LBR_TOS;
        x86_pmu.lbr_from   = MSR_LBR_CORE_FROM;
        x86_pmu.lbr_to     = MSR_LBR_CORE_TO;

        /*
         * SW branch filter usage:
         * - compensate for lack of HW filter
         */
        pr_cont("8-deep LBR, ");
}

/* Knights Landing */
void intel_pmu_lbr_init_knl(void)
{
        x86_pmu.lbr_nr     = 8;
        x86_pmu.lbr_tos    = MSR_LBR_TOS;
        x86_pmu.lbr_from   = MSR_LBR_NHM_FROM;
        x86_pmu.lbr_to     = MSR_LBR_NHM_TO;

        x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
        x86_pmu.lbr_sel_map  = snb_lbr_sel_map;

        pr_cont("8-deep LBR, ");
}