perfmon.c

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/*
 * This file implements the perfmon-2 subsystem which is used
 * to program the IA-64 Performance Monitoring Unit (PMU).
 *
 * The initial version of perfmon.c was written by
 * Ganesh Venkitachalam, IBM Corp.
 *
 * Then it was modified for perfmon-1.x by Stephane Eranian and
 * David Mosberger, Hewlett Packard Co.
 *
 * Version Perfmon-2.x is a rewrite of perfmon-1.x
 * by Stephane Eranian, Hewlett Packard Co.
 *
 * Copyright (C) 1999-2005  Hewlett Packard Co
 *               Stephane Eranian <[email protected]>
 *               David Mosberger-Tang <[email protected]>
 *
 * More information about perfmon available at:
 *  http://www.hpl.hp.com/research/linux/perfmon
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <linux/list.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/vfs.h>
#include <linux/smp.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/bitops.h>
#include <linux/capability.h>
#include <linux/rcupdate.h>
#include <linux/completion.h>
#include <linux/tracehook.h>
#include <linux/slab.h>

#include <asm/errno.h>
#include <asm/intrinsics.h>
#include <asm/page.h>
#include <asm/perfmon.h>
#include <asm/processor.h>
#include <asm/signal.h>
#include <asm/uaccess.h>
#include <asm/delay.h>

#ifdef CONFIG_PERFMON
/*
 * perfmon context state
 */
#define PFM_CTX_UNLOADED    1   /* context is not loaded onto any task */
#define PFM_CTX_LOADED      2   /* context is loaded onto a task */
#define PFM_CTX_MASKED      3   /* context is loaded but monitoring is masked due to overflow */
#define PFM_CTX_ZOMBIE      4   /* owner of the context is closing it */

#define PFM_INVALID_ACTIVATION  (~0UL)

#define PFM_NUM_PMC_REGS    64  /* PMC save area for ctxsw */
#define PFM_NUM_PMD_REGS    64  /* PMD save area for ctxsw */

/*
 * depth of message queue
 */
#define PFM_MAX_MSGS        32
#define PFM_CTXQ_EMPTY(g)   ((g)->ctx_msgq_head == (g)->ctx_msgq_tail)

/*
 * type of a PMU register (bitmask).
 * bitmask structure:
 *  bit0   : register implemented
 *  bit1   : end marker
 *  bit2-3 : reserved
 *  bit4   : pmc has pmc.pm
 *  bit5   : pmc controls a counter (has pmc.oi), pmd is used as counter
 *  bit6-7 : register type
 *  bit8-31: reserved
 */
#define PFM_REG_NOTIMPL     0x0 /* not implemented at all */
#define PFM_REG_IMPL        0x1 /* register implemented */
#define PFM_REG_END     0x2 /* end marker */
#define PFM_REG_MONITOR     (0x1<<4|PFM_REG_IMPL) /* a PMC with a pmc.pm field only */
#define PFM_REG_COUNTING    (0x2<<4|PFM_REG_MONITOR) /* a monitor + pmc.oi+ PMD used as a counter */
#define PFM_REG_CONTROL     (0x4<<4|PFM_REG_IMPL) /* PMU control register */
#define PFM_REG_CONFIG      (0x8<<4|PFM_REG_IMPL) /* configuration register */
#define PFM_REG_BUFFER      (0xc<<4|PFM_REG_IMPL) /* PMD used as buffer */

#define PMC_IS_LAST(i)  (pmu_conf->pmc_desc[i].type & PFM_REG_END)
#define PMD_IS_LAST(i)  (pmu_conf->pmd_desc[i].type & PFM_REG_END)

#define PMC_OVFL_NOTIFY(ctx, i) ((ctx)->ctx_pmds[i].flags &  PFM_REGFL_OVFL_NOTIFY)

/* i assumed unsigned */
#define PMC_IS_IMPL(i)    (i< PMU_MAX_PMCS && (pmu_conf->pmc_desc[i].type & PFM_REG_IMPL))
#define PMD_IS_IMPL(i)    (i< PMU_MAX_PMDS && (pmu_conf->pmd_desc[i].type & PFM_REG_IMPL))

/* XXX: these assume that register i is implemented */
#define PMD_IS_COUNTING(i) ((pmu_conf->pmd_desc[i].type & PFM_REG_COUNTING) == PFM_REG_COUNTING)
#define PMC_IS_COUNTING(i) ((pmu_conf->pmc_desc[i].type & PFM_REG_COUNTING) == PFM_REG_COUNTING)
#define PMC_IS_MONITOR(i)  ((pmu_conf->pmc_desc[i].type & PFM_REG_MONITOR)  == PFM_REG_MONITOR)
#define PMC_IS_CONTROL(i)  ((pmu_conf->pmc_desc[i].type & PFM_REG_CONTROL)  == PFM_REG_CONTROL)

#define PMC_DFL_VAL(i)     pmu_conf->pmc_desc[i].default_value
#define PMC_RSVD_MASK(i)   pmu_conf->pmc_desc[i].reserved_mask
#define PMD_PMD_DEP(i)     pmu_conf->pmd_desc[i].dep_pmd[0]
#define PMC_PMD_DEP(i)     pmu_conf->pmc_desc[i].dep_pmd[0]

#define PFM_NUM_IBRS      IA64_NUM_DBG_REGS
#define PFM_NUM_DBRS      IA64_NUM_DBG_REGS

#define CTX_OVFL_NOBLOCK(c) ((c)->ctx_fl_block == 0)
#define CTX_HAS_SMPL(c)     ((c)->ctx_fl_is_sampling)
#define PFM_CTX_TASK(h)     (h)->ctx_task

#define PMU_PMC_OI      5 /* position of pmc.oi bit */

/* XXX: does not support more than 64 PMDs */
#define CTX_USED_PMD(ctx, mask) (ctx)->ctx_used_pmds[0] |= (mask)
#define CTX_IS_USED_PMD(ctx, c) (((ctx)->ctx_used_pmds[0] & (1UL << (c))) != 0UL)

#define CTX_USED_MONITOR(ctx, mask) (ctx)->ctx_used_monitors[0] |= (mask)

#define CTX_USED_IBR(ctx,n)     (ctx)->ctx_used_ibrs[(n)>>6] |= 1UL<< ((n) % 64)
#define CTX_USED_DBR(ctx,n)     (ctx)->ctx_used_dbrs[(n)>>6] |= 1UL<< ((n) % 64)
#define CTX_USES_DBREGS(ctx)    (((pfm_context_t *)(ctx))->ctx_fl_using_dbreg==1)
#define PFM_CODE_RR 0   /* requesting code range restriction */
#define PFM_DATA_RR 1   /* requestion data range restriction */

#define PFM_CPUINFO_CLEAR(v)    pfm_get_cpu_var(pfm_syst_info) &= ~(v)
#define PFM_CPUINFO_SET(v)  pfm_get_cpu_var(pfm_syst_info) |= (v)
#define PFM_CPUINFO_GET()   pfm_get_cpu_var(pfm_syst_info)

#define RDEP(x) (1UL<<(x))

/*
 * context protection macros
 * in SMP:
 *  - we need to protect against CPU concurrency (spin_lock)
 *  - we need to protect against PMU overflow interrupts (local_irq_disable)
 * in UP:
 *  - we need to protect against PMU overflow interrupts (local_irq_disable)
 *
 * spin_lock_irqsave()/spin_unlock_irqrestore():
 *  in SMP: local_irq_disable + spin_lock
 *  in UP : local_irq_disable
 *
 * spin_lock()/spin_lock():
 *  in UP : removed automatically
 *  in SMP: protect against context accesses from other CPU. interrupts
 *          are not masked. This is useful for the PMU interrupt handler
 *          because we know we will not get PMU concurrency in that code.
 */
#define PROTECT_CTX(c, f) \
    do {  \
        DPRINT(("spinlock_irq_save ctx %p by [%d]\n", c, task_pid_nr(current))); \
        spin_lock_irqsave(&(c)->ctx_lock, f); \
        DPRINT(("spinlocked ctx %p  by [%d]\n", c, task_pid_nr(current))); \
    } while(0)

#define UNPROTECT_CTX(c, f) \
    do { \
        DPRINT(("spinlock_irq_restore ctx %p by [%d]\n", c, task_pid_nr(current))); \
        spin_unlock_irqrestore(&(c)->ctx_lock, f); \
    } while(0)

#define PROTECT_CTX_NOPRINT(c, f) \
    do {  \
        spin_lock_irqsave(&(c)->ctx_lock, f); \
    } while(0)


#define UNPROTECT_CTX_NOPRINT(c, f) \
    do { \
        spin_unlock_irqrestore(&(c)->ctx_lock, f); \
    } while(0)


#define PROTECT_CTX_NOIRQ(c) \
    do {  \
        spin_lock(&(c)->ctx_lock); \
    } while(0)

#define UNPROTECT_CTX_NOIRQ(c) \
    do { \
        spin_unlock(&(c)->ctx_lock); \
    } while(0)


#ifdef CONFIG_SMP

#define GET_ACTIVATION()    pfm_get_cpu_var(pmu_activation_number)
#define INC_ACTIVATION()    pfm_get_cpu_var(pmu_activation_number)++
#define SET_ACTIVATION(c)   (c)->ctx_last_activation = GET_ACTIVATION()

#else /* !CONFIG_SMP */
#define SET_ACTIVATION(t)   do {} while(0)
#define GET_ACTIVATION(t)   do {} while(0)
#define INC_ACTIVATION(t)   do {} while(0)
#endif /* CONFIG_SMP */

#define SET_PMU_OWNER(t, c) do { pfm_get_cpu_var(pmu_owner) = (t); pfm_get_cpu_var(pmu_ctx) = (c); } while(0)
#define GET_PMU_OWNER()     pfm_get_cpu_var(pmu_owner)
#define GET_PMU_CTX()       pfm_get_cpu_var(pmu_ctx)

#define LOCK_PFS(g)         spin_lock_irqsave(&pfm_sessions.pfs_lock, g)
#define UNLOCK_PFS(g)           spin_unlock_irqrestore(&pfm_sessions.pfs_lock, g)

#define PFM_REG_RETFLAG_SET(flags, val) do { flags &= ~PFM_REG_RETFL_MASK; flags |= (val); } while(0)

/*
 * cmp0 must be the value of pmc0
 */
#define PMC0_HAS_OVFL(cmp0)  (cmp0 & ~0x1UL)

#define PFMFS_MAGIC 0xa0b4d889

/*
 * debugging
 */
#define PFM_DEBUGGING 1
#ifdef PFM_DEBUGGING
#define DPRINT(a) \
    do { \
        if (unlikely(pfm_sysctl.debug >0)) { printk("%s.%d: CPU%d [%d] ", __func__, __LINE__, smp_processor_id(), task_pid_nr(current)); printk a; } \
    } while (0)

#define DPRINT_ovfl(a) \
    do { \
        if (unlikely(pfm_sysctl.debug > 0 && pfm_sysctl.debug_ovfl >0)) { printk("%s.%d: CPU%d [%d] ", __func__, __LINE__, smp_processor_id(), task_pid_nr(current)); printk a; } \
    } while (0)
#endif

/*
 * 64-bit software counter structure
 *
 * the next_reset_type is applied to the next call to pfm_reset_regs()
 */
typedef struct {
    unsigned long   val;        /* virtual 64bit counter value */
    unsigned long   lval;       /* last reset value */
    unsigned long   long_reset; /* reset value on sampling overflow */
    unsigned long   short_reset;    /* reset value on overflow */
    unsigned long   reset_pmds[4];  /* which other pmds to reset when this counter overflows */
    unsigned long   smpl_pmds[4];   /* which pmds are accessed when counter overflow */
    unsigned long   seed;       /* seed for random-number generator */
    unsigned long   mask;       /* mask for random-number generator */
    unsigned int    flags;      /* notify/do not notify */
    unsigned long   eventid;    /* overflow event identifier */
} pfm_counter_t;

/*
 * context flags
 */
typedef struct {
    unsigned int block:1;       /* when 1, task will blocked on user notifications */
    unsigned int system:1;      /* do system wide monitoring */
    unsigned int using_dbreg:1; /* using range restrictions (debug registers) */
    unsigned int is_sampling:1; /* true if using a custom format */
    unsigned int excl_idle:1;   /* exclude idle task in system wide session */
    unsigned int going_zombie:1;    /* context is zombie (MASKED+blocking) */
    unsigned int trap_reason:2; /* reason for going into pfm_handle_work() */
    unsigned int no_msg:1;      /* no message sent on overflow */
    unsigned int can_restart:1; /* allowed to issue a PFM_RESTART */
    unsigned int reserved:22;
} pfm_context_flags_t;

#define PFM_TRAP_REASON_NONE        0x0 /* default value */
#define PFM_TRAP_REASON_BLOCK       0x1 /* we need to block on overflow */
#define PFM_TRAP_REASON_RESET       0x2 /* we need to reset PMDs */


/*
 * perfmon context: encapsulates all the state of a monitoring session
 */

typedef struct pfm_context {
    spinlock_t      ctx_lock;       /* context protection */

    pfm_context_flags_t ctx_flags;      /* bitmask of flags  (block reason incl.) */
    unsigned int        ctx_state;      /* state: active/inactive (no bitfield) */

    struct task_struct  *ctx_task;      /* task to which context is attached */

    unsigned long       ctx_ovfl_regs[4];   /* which registers overflowed (notification) */

    struct completion   ctx_restart_done;   /* use for blocking notification mode */

    unsigned long       ctx_used_pmds[4];   /* bitmask of PMD used            */
    unsigned long       ctx_all_pmds[4];    /* bitmask of all accessible PMDs */
    unsigned long       ctx_reload_pmds[4]; /* bitmask of force reload PMD on ctxsw in */

    unsigned long       ctx_all_pmcs[4];    /* bitmask of all accessible PMCs */
    unsigned long       ctx_reload_pmcs[4]; /* bitmask of force reload PMC on ctxsw in */
    unsigned long       ctx_used_monitors[4];   /* bitmask of monitor PMC being used */

    unsigned long       ctx_pmcs[PFM_NUM_PMC_REGS]; /*  saved copies of PMC values */

    unsigned int        ctx_used_ibrs[1];       /* bitmask of used IBR (speedup ctxsw in) */
    unsigned int        ctx_used_dbrs[1];       /* bitmask of used DBR (speedup ctxsw in) */
    unsigned long       ctx_dbrs[IA64_NUM_DBG_REGS];    /* DBR values (cache) when not loaded */
    unsigned long       ctx_ibrs[IA64_NUM_DBG_REGS];    /* IBR values (cache) when not loaded */

    pfm_counter_t       ctx_pmds[PFM_NUM_PMD_REGS]; /* software state for PMDS */

    unsigned long       th_pmcs[PFM_NUM_PMC_REGS];  /* PMC thread save state */
    unsigned long       th_pmds[PFM_NUM_PMD_REGS];  /* PMD thread save state */

    unsigned long       ctx_saved_psr_up;   /* only contains psr.up value */

    unsigned long       ctx_last_activation;    /* context last activation number for last_cpu */
    unsigned int        ctx_last_cpu;       /* CPU id of current or last CPU used (SMP only) */
    unsigned int        ctx_cpu;        /* cpu to which perfmon is applied (system wide) */

    int         ctx_fd;         /* file descriptor used my this context */
    pfm_ovfl_arg_t      ctx_ovfl_arg;       /* argument to custom buffer format handler */

    pfm_buffer_fmt_t    *ctx_buf_fmt;       /* buffer format callbacks */
    void            *ctx_smpl_hdr;      /* points to sampling buffer header kernel vaddr */
    unsigned long       ctx_smpl_size;      /* size of sampling buffer */
    void            *ctx_smpl_vaddr;    /* user level virtual address of smpl buffer */

    wait_queue_head_t   ctx_msgq_wait;
    pfm_msg_t       ctx_msgq[PFM_MAX_MSGS];
    int         ctx_msgq_head;
    int         ctx_msgq_tail;
    struct fasync_struct    *ctx_async_queue;

    wait_queue_head_t   ctx_zombieq;        /* termination cleanup wait queue */
} pfm_context_t;

/*
 * magic number used to verify that structure is really
 * a perfmon context
 */
#define PFM_IS_FILE(f)      ((f)->f_op == &pfm_file_ops)

#define PFM_GET_CTX(t)      ((pfm_context_t *)(t)->thread.pfm_context)

#ifdef CONFIG_SMP
#define SET_LAST_CPU(ctx, v)    (ctx)->ctx_last_cpu = (v)
#define GET_LAST_CPU(ctx)   (ctx)->ctx_last_cpu
#else
#define SET_LAST_CPU(ctx, v)    do {} while(0)
#define GET_LAST_CPU(ctx)   do {} while(0)
#endif


#define ctx_fl_block        ctx_flags.block
#define ctx_fl_system       ctx_flags.system
#define ctx_fl_using_dbreg  ctx_flags.using_dbreg
#define ctx_fl_is_sampling  ctx_flags.is_sampling
#define ctx_fl_excl_idle    ctx_flags.excl_idle
#define ctx_fl_going_zombie ctx_flags.going_zombie
#define ctx_fl_trap_reason  ctx_flags.trap_reason
#define ctx_fl_no_msg       ctx_flags.no_msg
#define ctx_fl_can_restart  ctx_flags.can_restart

#define PFM_SET_WORK_PENDING(t, v)  do { (t)->thread.pfm_needs_checking = v; } while(0);
#define PFM_GET_WORK_PENDING(t)     (t)->thread.pfm_needs_checking

/*
 * global information about all sessions
 * mostly used to synchronize between system wide and per-process
 */
typedef struct {
    spinlock_t      pfs_lock;          /* lock the structure */

    unsigned int        pfs_task_sessions;     /* number of per task sessions */
    unsigned int        pfs_sys_sessions;      /* number of per system wide sessions */
    unsigned int        pfs_sys_use_dbregs;    /* incremented when a system wide session uses debug regs */
    unsigned int        pfs_ptrace_use_dbregs;     /* incremented when a process uses debug regs */
    struct task_struct  *pfs_sys_session[NR_CPUS]; /* point to task owning a system-wide session */
} pfm_session_t;

/*
 * information about a PMC or PMD.
 * dep_pmd[]: a bitmask of dependent PMD registers
 * dep_pmc[]: a bitmask of dependent PMC registers
 */
typedef int (*pfm_reg_check_t)(struct task_struct *task, pfm_context_t *ctx, unsigned int cnum, unsigned long *val, struct pt_regs *regs);
typedef struct {
    unsigned int        type;
    int         pm_pos;
    unsigned long       default_value;  /* power-on default value */
    unsigned long       reserved_mask;  /* bitmask of reserved bits */
    pfm_reg_check_t     read_check;
    pfm_reg_check_t     write_check;
    unsigned long       dep_pmd[4];
    unsigned long       dep_pmc[4];
} pfm_reg_desc_t;

/* assume cnum is a valid monitor */
#define PMC_PM(cnum, val)   (((val) >> (pmu_conf->pmc_desc[cnum].pm_pos)) & 0x1)

/*
 * This structure is initialized at boot time and contains
 * a description of the PMU main characteristics.
 *
 * If the probe function is defined, detection is based
 * on its return value: 
 *  - 0 means recognized PMU
 *  - anything else means not supported
 * When the probe function is not defined, then the pmu_family field
 * is used and it must match the host CPU family such that:
 *  - cpu->family & config->pmu_family != 0
 */
typedef struct {
    unsigned long  ovfl_val;    /* overflow value for counters */

    pfm_reg_desc_t *pmc_desc;   /* detailed PMC register dependencies descriptions */
    pfm_reg_desc_t *pmd_desc;   /* detailed PMD register dependencies descriptions */

    unsigned int   num_pmcs;    /* number of PMCS: computed at init time */
    unsigned int   num_pmds;    /* number of PMDS: computed at init time */
    unsigned long  impl_pmcs[4];    /* bitmask of implemented PMCS */
    unsigned long  impl_pmds[4];    /* bitmask of implemented PMDS */

    char          *pmu_name;    /* PMU family name */
    unsigned int  pmu_family;   /* cpuid family pattern used to identify pmu */
    unsigned int  flags;        /* pmu specific flags */
    unsigned int  num_ibrs;     /* number of IBRS: computed at init time */
    unsigned int  num_dbrs;     /* number of DBRS: computed at init time */
    unsigned int  num_counters; /* PMC/PMD counting pairs : computed at init time */
    int           (*probe)(void);   /* customized probe routine */
    unsigned int  use_rr_dbregs:1;  /* set if debug registers used for range restriction */
} pmu_config_t;
/*
 * PMU specific flags
 */
#define PFM_PMU_IRQ_RESEND  1   /* PMU needs explicit IRQ resend */

/*
 * debug register related type definitions
 */
typedef struct {
    unsigned long ibr_mask:56;
    unsigned long ibr_plm:4;
    unsigned long ibr_ig:3;
    unsigned long ibr_x:1;
} ibr_mask_reg_t;

typedef struct {
    unsigned long dbr_mask:56;
    unsigned long dbr_plm:4;
    unsigned long dbr_ig:2;
    unsigned long dbr_w:1;
    unsigned long dbr_r:1;
} dbr_mask_reg_t;

typedef union {
    unsigned long  val;
    ibr_mask_reg_t ibr;
    dbr_mask_reg_t dbr;
} dbreg_t;


/*
 * perfmon command descriptions
 */
typedef struct {
    int     (*cmd_func)(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);
    char        *cmd_name;
    int     cmd_flags;
    unsigned int    cmd_narg;
    size_t      cmd_argsize;
    int     (*cmd_getsize)(void *arg, size_t *sz);
} pfm_cmd_desc_t;

#define PFM_CMD_FD      0x01    /* command requires a file descriptor */
#define PFM_CMD_ARG_READ    0x02    /* command must read argument(s) */
#define PFM_CMD_ARG_RW      0x04    /* command must read/write argument(s) */
#define PFM_CMD_STOP        0x08    /* command does not work on zombie context */


#define PFM_CMD_NAME(cmd)   pfm_cmd_tab[(cmd)].cmd_name
#define PFM_CMD_READ_ARG(cmd)   (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_ARG_READ)
#define PFM_CMD_RW_ARG(cmd) (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_ARG_RW)
#define PFM_CMD_USE_FD(cmd) (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_FD)
#define PFM_CMD_STOPPED(cmd)    (pfm_cmd_tab[(cmd)].cmd_flags & PFM_CMD_STOP)

#define PFM_CMD_ARG_MANY    -1 /* cannot be zero */

typedef struct {
    unsigned long pfm_spurious_ovfl_intr_count; /* keep track of spurious ovfl interrupts */
    unsigned long pfm_replay_ovfl_intr_count;   /* keep track of replayed ovfl interrupts */
    unsigned long pfm_ovfl_intr_count;      /* keep track of ovfl interrupts */
    unsigned long pfm_ovfl_intr_cycles;     /* cycles spent processing ovfl interrupts */
    unsigned long pfm_ovfl_intr_cycles_min;     /* min cycles spent processing ovfl interrupts */
    unsigned long pfm_ovfl_intr_cycles_max;     /* max cycles spent processing ovfl interrupts */
    unsigned long pfm_smpl_handler_calls;
    unsigned long pfm_smpl_handler_cycles;
    char pad[SMP_CACHE_BYTES] ____cacheline_aligned;
} pfm_stats_t;

/*
 * perfmon internal variables
 */
static pfm_stats_t      pfm_stats[NR_CPUS];
static pfm_session_t        pfm_sessions;   /* global sessions information */

static DEFINE_SPINLOCK(pfm_alt_install_check);
static pfm_intr_handler_desc_t  *pfm_alt_intr_handler;

static struct proc_dir_entry    *perfmon_dir;
static pfm_uuid_t       pfm_null_uuid = {0,};

static spinlock_t       pfm_buffer_fmt_lock;
static LIST_HEAD(pfm_buffer_fmt_list);

static pmu_config_t     *pmu_conf;

/* sysctl() controls */
pfm_sysctl_t pfm_sysctl;
EXPORT_SYMBOL(pfm_sysctl);

static ctl_table pfm_ctl_table[]={
    {
        .procname   = "debug",
        .data       = &pfm_sysctl.debug,
        .maxlen     = sizeof(int),
        .mode       = 0666,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "debug_ovfl",
        .data       = &pfm_sysctl.debug_ovfl,
        .maxlen     = sizeof(int),
        .mode       = 0666,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "fastctxsw",
        .data       = &pfm_sysctl.fastctxsw,
        .maxlen     = sizeof(int),
        .mode       = 0600,
        .proc_handler   = proc_dointvec,
    },
    {
        .procname   = "expert_mode",
        .data       = &pfm_sysctl.expert_mode,
        .maxlen     = sizeof(int),
        .mode       = 0600,
        .proc_handler   = proc_dointvec,
    },
    {}
};
static ctl_table pfm_sysctl_dir[] = {
    {
        .procname   = "perfmon",
        .mode       = 0555,
        .child      = pfm_ctl_table,
    },
    {}
};
static ctl_table pfm_sysctl_root[] = {
    {
        .procname   = "kernel",
        .mode       = 0555,
        .child      = pfm_sysctl_dir,
    },
    {}
};
static struct ctl_table_header *pfm_sysctl_header;

static int pfm_context_unload(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);

#define pfm_get_cpu_var(v)      __ia64_per_cpu_var(v)
#define pfm_get_cpu_data(a,b)       per_cpu(a, b)

static inline void
pfm_put_task(struct task_struct *task)
{
    if (task != current) put_task_struct(task);
}

static inline void
pfm_reserve_page(unsigned long a)
{
    SetPageReserved(vmalloc_to_page((void *)a));
}
static inline void
pfm_unreserve_page(unsigned long a)
{
    ClearPageReserved(vmalloc_to_page((void*)a));
}

static inline unsigned long
pfm_protect_ctx_ctxsw(pfm_context_t *x)
{
    spin_lock(&(x)->ctx_lock);
    return 0UL;
}

static inline void
pfm_unprotect_ctx_ctxsw(pfm_context_t *x, unsigned long f)
{
    spin_unlock(&(x)->ctx_lock);
}

/* forward declaration */
static const struct dentry_operations pfmfs_dentry_operations;

static struct dentry *
pfmfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data)
{
    return mount_pseudo(fs_type, "pfm:", NULL, &pfmfs_dentry_operations,
            PFMFS_MAGIC);
}

static struct file_system_type pfm_fs_type = {
    .name     = "pfmfs",
    .mount    = pfmfs_mount,
    .kill_sb  = kill_anon_super,
};

DEFINE_PER_CPU(unsigned long, pfm_syst_info);
DEFINE_PER_CPU(struct task_struct *, pmu_owner);
DEFINE_PER_CPU(pfm_context_t  *, pmu_ctx);
DEFINE_PER_CPU(unsigned long, pmu_activation_number);
EXPORT_PER_CPU_SYMBOL_GPL(pfm_syst_info);


/* forward declaration */
static const struct file_operations pfm_file_ops;

/*
 * forward declarations
 */
#ifndef CONFIG_SMP
static void pfm_lazy_save_regs (struct task_struct *ta);
#endif

void dump_pmu_state(const char *);
static int pfm_write_ibr_dbr(int mode, pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);

#include "perfmon_itanium.h"
#include "perfmon_mckinley.h"
#include "perfmon_montecito.h"
#include "perfmon_generic.h"

static pmu_config_t *pmu_confs[]={
    &pmu_conf_mont,
    &pmu_conf_mck,
    &pmu_conf_ita,
    &pmu_conf_gen, /* must be last */
    NULL
};


static int pfm_end_notify_user(pfm_context_t *ctx);

static inline void
pfm_clear_psr_pp(void)
{
    ia64_rsm(IA64_PSR_PP);
    ia64_srlz_i();
}

static inline void
pfm_set_psr_pp(void)
{
    ia64_ssm(IA64_PSR_PP);
    ia64_srlz_i();
}

static inline void
pfm_clear_psr_up(void)
{
    ia64_rsm(IA64_PSR_UP);
    ia64_srlz_i();
}

static inline void
pfm_set_psr_up(void)
{
    ia64_ssm(IA64_PSR_UP);
    ia64_srlz_i();
}

static inline unsigned long
pfm_get_psr(void)
{
    unsigned long tmp;
    tmp = ia64_getreg(_IA64_REG_PSR);
    ia64_srlz_i();
    return tmp;
}

static inline void
pfm_set_psr_l(unsigned long val)
{
    ia64_setreg(_IA64_REG_PSR_L, val);
    ia64_srlz_i();
}

static inline void
pfm_freeze_pmu(void)
{
    ia64_set_pmc(0,1UL);
    ia64_srlz_d();
}

static inline void
pfm_unfreeze_pmu(void)
{
    ia64_set_pmc(0,0UL);
    ia64_srlz_d();
}

static inline void
pfm_restore_ibrs(unsigned long *ibrs, unsigned int nibrs)
{
    int i;

    for (i=0; i < nibrs; i++) {
        ia64_set_ibr(i, ibrs[i]);
        ia64_dv_serialize_instruction();
    }
    ia64_srlz_i();
}

static inline void
pfm_restore_dbrs(unsigned long *dbrs, unsigned int ndbrs)
{
    int i;

    for (i=0; i < ndbrs; i++) {
        ia64_set_dbr(i, dbrs[i]);
        ia64_dv_serialize_data();
    }
    ia64_srlz_d();
}

/*
 * PMD[i] must be a counter. no check is made
 */
static inline unsigned long
pfm_read_soft_counter(pfm_context_t *ctx, int i)
{
    return ctx->ctx_pmds[i].val + (ia64_get_pmd(i) & pmu_conf->ovfl_val);
}

/*
 * PMD[i] must be a counter. no check is made
 */
static inline void
pfm_write_soft_counter(pfm_context_t *ctx, int i, unsigned long val)
{
    unsigned long ovfl_val = pmu_conf->ovfl_val;

    ctx->ctx_pmds[i].val = val  & ~ovfl_val;
    /*
     * writing to unimplemented part is ignore, so we do not need to
     * mask off top part
     */
    ia64_set_pmd(i, val & ovfl_val);
}

static pfm_msg_t *
pfm_get_new_msg(pfm_context_t *ctx)
{
    int idx, next;

    next = (ctx->ctx_msgq_tail+1) % PFM_MAX_MSGS;

    DPRINT(("ctx_fd=%p head=%d tail=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail));
    if (next == ctx->ctx_msgq_head) return NULL;

    idx =   ctx->ctx_msgq_tail;
    ctx->ctx_msgq_tail = next;

    DPRINT(("ctx=%p head=%d tail=%d msg=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail, idx));

    return ctx->ctx_msgq+idx;
}

static pfm_msg_t *
pfm_get_next_msg(pfm_context_t *ctx)
{
    pfm_msg_t *msg;

    DPRINT(("ctx=%p head=%d tail=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail));

    if (PFM_CTXQ_EMPTY(ctx)) return NULL;

    /*
     * get oldest message
     */
    msg = ctx->ctx_msgq+ctx->ctx_msgq_head;

    /*
     * and move forward
     */
    ctx->ctx_msgq_head = (ctx->ctx_msgq_head+1) % PFM_MAX_MSGS;

    DPRINT(("ctx=%p head=%d tail=%d type=%d\n", ctx, ctx->ctx_msgq_head, ctx->ctx_msgq_tail, msg->pfm_gen_msg.msg_type));

    return msg;
}

static void
pfm_reset_msgq(pfm_context_t *ctx)
{
    ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
    DPRINT(("ctx=%p msgq reset\n", ctx));
}

static void *
pfm_rvmalloc(unsigned long size)
{
    void *mem;
    unsigned long addr;

    size = PAGE_ALIGN(size);
    mem  = vzalloc(size);
    if (mem) {
        //printk("perfmon: CPU%d pfm_rvmalloc(%ld)=%p\n", smp_processor_id(), size, mem);
        addr = (unsigned long)mem;
        while (size > 0) {
            pfm_reserve_page(addr);
            addr+=PAGE_SIZE;
            size-=PAGE_SIZE;
        }
    }
    return mem;
}

static void
pfm_rvfree(void *mem, unsigned long size)
{
    unsigned long addr;

    if (mem) {
        DPRINT(("freeing physical buffer @%p size=%lu\n", mem, size));
        addr = (unsigned long) mem;
        while ((long) size > 0) {
            pfm_unreserve_page(addr);
            addr+=PAGE_SIZE;
            size-=PAGE_SIZE;
        }
        vfree(mem);
    }
    return;
}

static pfm_context_t *
pfm_context_alloc(int ctx_flags)
{
    pfm_context_t *ctx;

    /* 
     * allocate context descriptor 
     * must be able to free with interrupts disabled
     */
    ctx = kzalloc(sizeof(pfm_context_t), GFP_KERNEL);
    if (ctx) {
        DPRINT(("alloc ctx @%p\n", ctx));

        /*
         * init context protection lock
         */
        spin_lock_init(&ctx->ctx_lock);

        /*
         * context is unloaded
         */
        ctx->ctx_state = PFM_CTX_UNLOADED;

        /*
         * initialization of context's flags
         */
        ctx->ctx_fl_block       = (ctx_flags & PFM_FL_NOTIFY_BLOCK) ? 1 : 0;
        ctx->ctx_fl_system      = (ctx_flags & PFM_FL_SYSTEM_WIDE) ? 1: 0;
        ctx->ctx_fl_no_msg      = (ctx_flags & PFM_FL_OVFL_NO_MSG) ? 1: 0;
        /*
         * will move to set properties
         * ctx->ctx_fl_excl_idle   = (ctx_flags & PFM_FL_EXCL_IDLE) ? 1: 0;
         */

        /*
         * init restart semaphore to locked
         */
        init_completion(&ctx->ctx_restart_done);

        /*
         * activation is used in SMP only
         */
        ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
        SET_LAST_CPU(ctx, -1);

        /*
         * initialize notification message queue
         */
        ctx->ctx_msgq_head = ctx->ctx_msgq_tail = 0;
        init_waitqueue_head(&ctx->ctx_msgq_wait);
        init_waitqueue_head(&ctx->ctx_zombieq);

    }
    return ctx;
}

static void
pfm_context_free(pfm_context_t *ctx)
{
    if (ctx) {
        DPRINT(("free ctx @%p\n", ctx));
        kfree(ctx);
    }
}

static void
pfm_mask_monitoring(struct task_struct *task)
{
    pfm_context_t *ctx = PFM_GET_CTX(task);
    unsigned long mask, val, ovfl_mask;
    int i;

    DPRINT_ovfl(("masking monitoring for [%d]\n", task_pid_nr(task)));

    ovfl_mask = pmu_conf->ovfl_val;
    /*
     * monitoring can only be masked as a result of a valid
     * counter overflow. In UP, it means that the PMU still
     * has an owner. Note that the owner can be different
     * from the current task. However the PMU state belongs
     * to the owner.
     * In SMP, a valid overflow only happens when task is
     * current. Therefore if we come here, we know that
     * the PMU state belongs to the current task, therefore
     * we can access the live registers.
     *
     * So in both cases, the live register contains the owner's
     * state. We can ONLY touch the PMU registers and NOT the PSR.
     *
     * As a consequence to this call, the ctx->th_pmds[] array
     * contains stale information which must be ignored
     * when context is reloaded AND monitoring is active (see
     * pfm_restart).
     */
    mask = ctx->ctx_used_pmds[0];
    for (i = 0; mask; i++, mask>>=1) {
        /* skip non used pmds */
        if ((mask & 0x1) == 0) continue;
        val = ia64_get_pmd(i);

        if (PMD_IS_COUNTING(i)) {
            /*
             * we rebuild the full 64 bit value of the counter
             */
            ctx->ctx_pmds[i].val += (val & ovfl_mask);
        } else {
            ctx->ctx_pmds[i].val = val;
        }
        DPRINT_ovfl(("pmd[%d]=0x%lx hw_pmd=0x%lx\n",
            i,
            ctx->ctx_pmds[i].val,
            val & ovfl_mask));
    }
    /*
     * mask monitoring by setting the privilege level to 0
     * we cannot use psr.pp/psr.up for this, it is controlled by
     * the user
     *
     * if task is current, modify actual registers, otherwise modify
     * thread save state, i.e., what will be restored in pfm_load_regs()
     */
    mask = ctx->ctx_used_monitors[0] >> PMU_FIRST_COUNTER;
    for(i= PMU_FIRST_COUNTER; mask; i++, mask>>=1) {
        if ((mask & 0x1) == 0UL) continue;
        ia64_set_pmc(i, ctx->th_pmcs[i] & ~0xfUL);
        ctx->th_pmcs[i] &= ~0xfUL;
        DPRINT_ovfl(("pmc[%d]=0x%lx\n", i, ctx->th_pmcs[i]));
    }
    /*
     * make all of this visible
     */
    ia64_srlz_d();
}

/*
 * must always be done with task == current
 *
 * context must be in MASKED state when calling
 */
static void
pfm_restore_monitoring(struct task_struct *task)
{
    pfm_context_t *ctx = PFM_GET_CTX(task);
    unsigned long mask, ovfl_mask;
    unsigned long psr, val;
    int i, is_system;

    is_system = ctx->ctx_fl_system;
    ovfl_mask = pmu_conf->ovfl_val;

    if (task != current) {
        printk(KERN_ERR "perfmon.%d: invalid task[%d] current[%d]\n", __LINE__, task_pid_nr(task), task_pid_nr(current));
        return;
    }
    if (ctx->ctx_state != PFM_CTX_MASKED) {
        printk(KERN_ERR "perfmon.%d: task[%d] current[%d] invalid state=%d\n", __LINE__,
            task_pid_nr(task), task_pid_nr(current), ctx->ctx_state);
        return;
    }
    psr = pfm_get_psr();
    /*
     * monitoring is masked via the PMC.
     * As we restore their value, we do not want each counter to
     * restart right away. We stop monitoring using the PSR,
     * restore the PMC (and PMD) and then re-establish the psr
     * as it was. Note that there can be no pending overflow at
     * this point, because monitoring was MASKED.
     *
     * system-wide session are pinned and self-monitoring
     */
    if (is_system && (PFM_CPUINFO_GET() & PFM_CPUINFO_DCR_PP)) {
        /* disable dcr pp */
        ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) & ~IA64_DCR_PP);
        pfm_clear_psr_pp();
    } else {
        pfm_clear_psr_up();
    }
    /*
     * first, we restore the PMD
     */
    mask = ctx->ctx_used_pmds[0];
    for (i = 0; mask; i++, mask>>=1) {
        /* skip non used pmds */
        if ((mask & 0x1) == 0) continue;

        if (PMD_IS_COUNTING(i)) {
            /*
             * we split the 64bit value according to
             * counter width
             */
            val = ctx->ctx_pmds[i].val & ovfl_mask;
            ctx->ctx_pmds[i].val &= ~ovfl_mask;
        } else {
            val = ctx->ctx_pmds[i].val;
        }
        ia64_set_pmd(i, val);

        DPRINT(("pmd[%d]=0x%lx hw_pmd=0x%lx\n",
            i,
            ctx->ctx_pmds[i].val,
            val));
    }
    /*
     * restore the PMCs
     */
    mask = ctx->ctx_used_monitors[0] >> PMU_FIRST_COUNTER;
    for(i= PMU_FIRST_COUNTER; mask; i++, mask>>=1) {
        if ((mask & 0x1) == 0UL) continue;
        ctx->th_pmcs[i] = ctx->ctx_pmcs[i];
        ia64_set_pmc(i, ctx->th_pmcs[i]);
        DPRINT(("[%d] pmc[%d]=0x%lx\n",
                    task_pid_nr(task), i, ctx->th_pmcs[i]));
    }
    ia64_srlz_d();

    /*
     * must restore DBR/IBR because could be modified while masked
     * XXX: need to optimize 
     */
    if (ctx->ctx_fl_using_dbreg) {
        pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
        pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
    }

    /*
     * now restore PSR
     */
    if (is_system && (PFM_CPUINFO_GET() & PFM_CPUINFO_DCR_PP)) {
        /* enable dcr pp */
        ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) | IA64_DCR_PP);
        ia64_srlz_i();
    }
    pfm_set_psr_l(psr);
}

static inline void
pfm_save_pmds(unsigned long *pmds, unsigned long mask)
{
    int i;

    ia64_srlz_d();

    for (i=0; mask; i++, mask>>=1) {
        if (mask & 0x1) pmds[i] = ia64_get_pmd(i);
    }
}

/*
 * reload from thread state (used for ctxw only)
 */
static inline void
pfm_restore_pmds(unsigned long *pmds, unsigned long mask)
{
    int i;
    unsigned long val, ovfl_val = pmu_conf->ovfl_val;

    for (i=0; mask; i++, mask>>=1) {
        if ((mask & 0x1) == 0) continue;
        val = PMD_IS_COUNTING(i) ? pmds[i] & ovfl_val : pmds[i];
        ia64_set_pmd(i, val);
    }
    ia64_srlz_d();
}

/*
 * propagate PMD from context to thread-state
 */
static inline void
pfm_copy_pmds(struct task_struct *task, pfm_context_t *ctx)
{
    unsigned long ovfl_val = pmu_conf->ovfl_val;
    unsigned long mask = ctx->ctx_all_pmds[0];
    unsigned long val;
    int i;

    DPRINT(("mask=0x%lx\n", mask));

    for (i=0; mask; i++, mask>>=1) {

        val = ctx->ctx_pmds[i].val;

        /*
         * We break up the 64 bit value into 2 pieces
         * the lower bits go to the machine state in the
         * thread (will be reloaded on ctxsw in).
         * The upper part stays in the soft-counter.
         */
        if (PMD_IS_COUNTING(i)) {
            ctx->ctx_pmds[i].val = val & ~ovfl_val;
             val &= ovfl_val;
        }
        ctx->th_pmds[i] = val;

        DPRINT(("pmd[%d]=0x%lx soft_val=0x%lx\n",
            i,
            ctx->th_pmds[i],
            ctx->ctx_pmds[i].val));
    }
}

/*
 * propagate PMC from context to thread-state
 */
static inline void
pfm_copy_pmcs(struct task_struct *task, pfm_context_t *ctx)
{
    unsigned long mask = ctx->ctx_all_pmcs[0];
    int i;

    DPRINT(("mask=0x%lx\n", mask));

    for (i=0; mask; i++, mask>>=1) {
        /* masking 0 with ovfl_val yields 0 */
        ctx->th_pmcs[i] = ctx->ctx_pmcs[i];
        DPRINT(("pmc[%d]=0x%lx\n", i, ctx->th_pmcs[i]));
    }
}



static inline void
pfm_restore_pmcs(unsigned long *pmcs, unsigned long mask)
{
    int i;

    for (i=0; mask; i++, mask>>=1) {
        if ((mask & 0x1) == 0) continue;
        ia64_set_pmc(i, pmcs[i]);
    }
    ia64_srlz_d();
}

static inline int
pfm_uuid_cmp(pfm_uuid_t a, pfm_uuid_t b)
{
    return memcmp(a, b, sizeof(pfm_uuid_t));
}

static inline int
pfm_buf_fmt_exit(pfm_buffer_fmt_t *fmt, struct task_struct *task, void *buf, struct pt_regs *regs)
{
    int ret = 0;
    if (fmt->fmt_exit) ret = (*fmt->fmt_exit)(task, buf, regs);
    return ret;
}

static inline int
pfm_buf_fmt_getsize(pfm_buffer_fmt_t *fmt, struct task_struct *task, unsigned int flags, int cpu, void *arg, unsigned long *size)
{
    int ret = 0;
    if (fmt->fmt_getsize) ret = (*fmt->fmt_getsize)(task, flags, cpu, arg, size);
    return ret;
}


static inline int
pfm_buf_fmt_validate(pfm_buffer_fmt_t *fmt, struct task_struct *task, unsigned int flags,
             int cpu, void *arg)
{
    int ret = 0;
    if (fmt->fmt_validate) ret = (*fmt->fmt_validate)(task, flags, cpu, arg);
    return ret;
}

static inline int
pfm_buf_fmt_init(pfm_buffer_fmt_t *fmt, struct task_struct *task, void *buf, unsigned int flags,
             int cpu, void *arg)
{
    int ret = 0;
    if (fmt->fmt_init) ret = (*fmt->fmt_init)(task, buf, flags, cpu, arg);
    return ret;
}

static inline int
pfm_buf_fmt_restart(pfm_buffer_fmt_t *fmt, struct task_struct *task, pfm_ovfl_ctrl_t *ctrl, void *buf, struct pt_regs *regs)
{
    int ret = 0;
    if (fmt->fmt_restart) ret = (*fmt->fmt_restart)(task, ctrl, buf, regs);
    return ret;
}

static inline int
pfm_buf_fmt_restart_active(pfm_buffer_fmt_t *fmt, struct task_struct *task, pfm_ovfl_ctrl_t *ctrl, void *buf, struct pt_regs *regs)
{
    int ret = 0;
    if (fmt->fmt_restart_active) ret = (*fmt->fmt_restart_active)(task, ctrl, buf, regs);
    return ret;
}

static pfm_buffer_fmt_t *
__pfm_find_buffer_fmt(pfm_uuid_t uuid)
{
    struct list_head * pos;
    pfm_buffer_fmt_t * entry;

    list_for_each(pos, &pfm_buffer_fmt_list) {
        entry = list_entry(pos, pfm_buffer_fmt_t, fmt_list);
        if (pfm_uuid_cmp(uuid, entry->fmt_uuid) == 0)
            return entry;
    }
    return NULL;
}
 
/*
 * find a buffer format based on its uuid
 */
static pfm_buffer_fmt_t *
pfm_find_buffer_fmt(pfm_uuid_t uuid)
{
    pfm_buffer_fmt_t * fmt;
    spin_lock(&pfm_buffer_fmt_lock);
    fmt = __pfm_find_buffer_fmt(uuid);
    spin_unlock(&pfm_buffer_fmt_lock);
    return fmt;
}
 
int
pfm_register_buffer_fmt(pfm_buffer_fmt_t *fmt)
{
    int ret = 0;

    /* some sanity checks */
    if (fmt == NULL || fmt->fmt_name == NULL) return -EINVAL;

    /* we need at least a handler */
    if (fmt->fmt_handler == NULL) return -EINVAL;

    /*
     * XXX: need check validity of fmt_arg_size
     */

    spin_lock(&pfm_buffer_fmt_lock);

    if (__pfm_find_buffer_fmt(fmt->fmt_uuid)) {
        printk(KERN_ERR "perfmon: duplicate sampling format: %s\n", fmt->fmt_name);
        ret = -EBUSY;
        goto out;
    } 
    list_add(&fmt->fmt_list, &pfm_buffer_fmt_list);
    printk(KERN_INFO "perfmon: added sampling format %s\n", fmt->fmt_name);

out:
    spin_unlock(&pfm_buffer_fmt_lock);
    return ret;
}
EXPORT_SYMBOL(pfm_register_buffer_fmt);

int
pfm_unregister_buffer_fmt(pfm_uuid_t uuid)
{
    pfm_buffer_fmt_t *fmt;
    int ret = 0;

    spin_lock(&pfm_buffer_fmt_lock);

    fmt = __pfm_find_buffer_fmt(uuid);
    if (!fmt) {
        printk(KERN_ERR "perfmon: cannot unregister format, not found\n");
        ret = -EINVAL;
        goto out;
    }
    list_del_init(&fmt->fmt_list);
    printk(KERN_INFO "perfmon: removed sampling format: %s\n", fmt->fmt_name);

out:
    spin_unlock(&pfm_buffer_fmt_lock);
    return ret;

}
EXPORT_SYMBOL(pfm_unregister_buffer_fmt);

extern void update_pal_halt_status(int);

static int
pfm_reserve_session(struct task_struct *task, int is_syswide, unsigned int cpu)
{
    unsigned long flags;
    /*
     * validity checks on cpu_mask have been done upstream
     */
    LOCK_PFS(flags);

    DPRINT(("in sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
        pfm_sessions.pfs_sys_sessions,
        pfm_sessions.pfs_task_sessions,
        pfm_sessions.pfs_sys_use_dbregs,
        is_syswide,
        cpu));

    if (is_syswide) {
        /*
         * cannot mix system wide and per-task sessions
         */
        if (pfm_sessions.pfs_task_sessions > 0UL) {
            DPRINT(("system wide not possible, %u conflicting task_sessions\n",
                pfm_sessions.pfs_task_sessions));
            goto abort;
        }

        if (pfm_sessions.pfs_sys_session[cpu]) goto error_conflict;

        DPRINT(("reserving system wide session on CPU%u currently on CPU%u\n", cpu, smp_processor_id()));

        pfm_sessions.pfs_sys_session[cpu] = task;

        pfm_sessions.pfs_sys_sessions++ ;

    } else {
        if (pfm_sessions.pfs_sys_sessions) goto abort;
        pfm_sessions.pfs_task_sessions++;
    }

    DPRINT(("out sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
        pfm_sessions.pfs_sys_sessions,
        pfm_sessions.pfs_task_sessions,
        pfm_sessions.pfs_sys_use_dbregs,
        is_syswide,
        cpu));

    /*
     * disable default_idle() to go to PAL_HALT
     */
    update_pal_halt_status(0);

    UNLOCK_PFS(flags);

    return 0;

error_conflict:
    DPRINT(("system wide not possible, conflicting session [%d] on CPU%d\n",
        task_pid_nr(pfm_sessions.pfs_sys_session[cpu]),
        cpu));
abort:
    UNLOCK_PFS(flags);

    return -EBUSY;

}

static int
pfm_unreserve_session(pfm_context_t *ctx, int is_syswide, unsigned int cpu)
{
    unsigned long flags;
    /*
     * validity checks on cpu_mask have been done upstream
     */
    LOCK_PFS(flags);

    DPRINT(("in sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
        pfm_sessions.pfs_sys_sessions,
        pfm_sessions.pfs_task_sessions,
        pfm_sessions.pfs_sys_use_dbregs,
        is_syswide,
        cpu));


    if (is_syswide) {
        pfm_sessions.pfs_sys_session[cpu] = NULL;
        /*
         * would not work with perfmon+more than one bit in cpu_mask
         */
        if (ctx && ctx->ctx_fl_using_dbreg) {
            if (pfm_sessions.pfs_sys_use_dbregs == 0) {
                printk(KERN_ERR "perfmon: invalid release for ctx %p sys_use_dbregs=0\n", ctx);
            } else {
                pfm_sessions.pfs_sys_use_dbregs--;
            }
        }
        pfm_sessions.pfs_sys_sessions--;
    } else {
        pfm_sessions.pfs_task_sessions--;
    }
    DPRINT(("out sys_sessions=%u task_sessions=%u dbregs=%u syswide=%d cpu=%u\n",
        pfm_sessions.pfs_sys_sessions,
        pfm_sessions.pfs_task_sessions,
        pfm_sessions.pfs_sys_use_dbregs,
        is_syswide,
        cpu));

    /*
     * if possible, enable default_idle() to go into PAL_HALT
     */
    if (pfm_sessions.pfs_task_sessions == 0 && pfm_sessions.pfs_sys_sessions == 0)
        update_pal_halt_status(1);

    UNLOCK_PFS(flags);

    return 0;
}

/*
 * removes virtual mapping of the sampling buffer.
 * IMPORTANT: cannot be called with interrupts disable, e.g. inside
 * a PROTECT_CTX() section.
 */
static int
pfm_remove_smpl_mapping(void *vaddr, unsigned long size)
{
    struct task_struct *task = current;
    int r;

    /* sanity checks */
    if (task->mm == NULL || size == 0UL || vaddr == NULL) {
        printk(KERN_ERR "perfmon: pfm_remove_smpl_mapping [%d] invalid context mm=%p\n", task_pid_nr(task), task->mm);
        return -EINVAL;
    }

    DPRINT(("smpl_vaddr=%p size=%lu\n", vaddr, size));

    /*
     * does the actual unmapping
     */
    r = vm_munmap((unsigned long)vaddr, size);

    if (r !=0) {
        printk(KERN_ERR "perfmon: [%d] unable to unmap sampling buffer @%p size=%lu\n", task_pid_nr(task), vaddr, size);
    }

    DPRINT(("do_unmap(%p, %lu)=%d\n", vaddr, size, r));

    return 0;
}

/*
 * free actual physical storage used by sampling buffer
 */
#if 0
static int
pfm_free_smpl_buffer(pfm_context_t *ctx)
{
    pfm_buffer_fmt_t *fmt;

    if (ctx->ctx_smpl_hdr == NULL) goto invalid_free;

    /*
     * we won't use the buffer format anymore
     */
    fmt = ctx->ctx_buf_fmt;

    DPRINT(("sampling buffer @%p size %lu vaddr=%p\n",
        ctx->ctx_smpl_hdr,
        ctx->ctx_smpl_size,
        ctx->ctx_smpl_vaddr));

    pfm_buf_fmt_exit(fmt, current, NULL, NULL);

    /*
     * free the buffer
     */
    pfm_rvfree(ctx->ctx_smpl_hdr, ctx->ctx_smpl_size);

    ctx->ctx_smpl_hdr  = NULL;
    ctx->ctx_smpl_size = 0UL;

    return 0;

invalid_free:
    printk(KERN_ERR "perfmon: pfm_free_smpl_buffer [%d] no buffer\n", task_pid_nr(current));
    return -EINVAL;
}
#endif

static inline void
pfm_exit_smpl_buffer(pfm_buffer_fmt_t *fmt)
{
    if (fmt == NULL) return;

    pfm_buf_fmt_exit(fmt, current, NULL, NULL);

}

/*
 * pfmfs should _never_ be mounted by userland - too much of security hassle,
 * no real gain from having the whole whorehouse mounted. So we don't need
 * any operations on the root directory. However, we need a non-trivial
 * d_name - pfm: will go nicely and kill the special-casing in procfs.
 */
static struct vfsmount *pfmfs_mnt __read_mostly;

static int __init
init_pfm_fs(void)
{
    int err = register_filesystem(&pfm_fs_type);
    if (!err) {
        pfmfs_mnt = kern_mount(&pfm_fs_type);
        err = PTR_ERR(pfmfs_mnt);
        if (IS_ERR(pfmfs_mnt))
            unregister_filesystem(&pfm_fs_type);
        else
            err = 0;
    }
    return err;
}

static ssize_t
pfm_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{
    pfm_context_t *ctx;
    pfm_msg_t *msg;
    ssize_t ret;
    unsigned long flags;
    DECLARE_WAITQUEUE(wait, current);
    if (PFM_IS_FILE(filp) == 0) {
        printk(KERN_ERR "perfmon: pfm_poll: bad magic [%d]\n", task_pid_nr(current));
        return -EINVAL;
    }

    ctx = filp->private_data;
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: pfm_read: NULL ctx [%d]\n", task_pid_nr(current));
        return -EINVAL;
    }

    /*
     * check even when there is no message
     */
    if (size < sizeof(pfm_msg_t)) {
        DPRINT(("message is too small ctx=%p (>=%ld)\n", ctx, sizeof(pfm_msg_t)));
        return -EINVAL;
    }

    PROTECT_CTX(ctx, flags);

    /*
     * put ourselves on the wait queue
     */
    add_wait_queue(&ctx->ctx_msgq_wait, &wait);


    for(;;) {
        /*
         * check wait queue
         */

        set_current_state(TASK_INTERRUPTIBLE);

        DPRINT(("head=%d tail=%d\n", ctx->ctx_msgq_head, ctx->ctx_msgq_tail));

        ret = 0;
        if(PFM_CTXQ_EMPTY(ctx) == 0) break;

        UNPROTECT_CTX(ctx, flags);

        /*
         * check non-blocking read
         */
            ret = -EAGAIN;
        if(filp->f_flags & O_NONBLOCK) break;

        /*
         * check pending signals
         */
        if(signal_pending(current)) {
            ret = -EINTR;
            break;
        }
            /*
         * no message, so wait
         */
            schedule();

        PROTECT_CTX(ctx, flags);
    }
    DPRINT(("[%d] back to running ret=%ld\n", task_pid_nr(current), ret));
    set_current_state(TASK_RUNNING);
    remove_wait_queue(&ctx->ctx_msgq_wait, &wait);

    if (ret < 0) goto abort;

    ret = -EINVAL;
    msg = pfm_get_next_msg(ctx);
    if (msg == NULL) {
        printk(KERN_ERR "perfmon: pfm_read no msg for ctx=%p [%d]\n", ctx, task_pid_nr(current));
        goto abort_locked;
    }

    DPRINT(("fd=%d type=%d\n", msg->pfm_gen_msg.msg_ctx_fd, msg->pfm_gen_msg.msg_type));

    ret = -EFAULT;
    if(copy_to_user(buf, msg, sizeof(pfm_msg_t)) == 0) ret = sizeof(pfm_msg_t);

abort_locked:
    UNPROTECT_CTX(ctx, flags);
abort:
    return ret;
}

static ssize_t
pfm_write(struct file *file, const char __user *ubuf,
              size_t size, loff_t *ppos)
{
    DPRINT(("pfm_write called\n"));
    return -EINVAL;
}

static unsigned int
pfm_poll(struct file *filp, poll_table * wait)
{
    pfm_context_t *ctx;
    unsigned long flags;
    unsigned int mask = 0;

    if (PFM_IS_FILE(filp) == 0) {
        printk(KERN_ERR "perfmon: pfm_poll: bad magic [%d]\n", task_pid_nr(current));
        return 0;
    }

    ctx = filp->private_data;
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: pfm_poll: NULL ctx [%d]\n", task_pid_nr(current));
        return 0;
    }


    DPRINT(("pfm_poll ctx_fd=%d before poll_wait\n", ctx->ctx_fd));

    poll_wait(filp, &ctx->ctx_msgq_wait, wait);

    PROTECT_CTX(ctx, flags);

    if (PFM_CTXQ_EMPTY(ctx) == 0)
        mask =  POLLIN | POLLRDNORM;

    UNPROTECT_CTX(ctx, flags);

    DPRINT(("pfm_poll ctx_fd=%d mask=0x%x\n", ctx->ctx_fd, mask));

    return mask;
}

static long
pfm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    DPRINT(("pfm_ioctl called\n"));
    return -EINVAL;
}

/*
 * interrupt cannot be masked when coming here
 */
static inline int
pfm_do_fasync(int fd, struct file *filp, pfm_context_t *ctx, int on)
{
    int ret;

    ret = fasync_helper (fd, filp, on, &ctx->ctx_async_queue);

    DPRINT(("pfm_fasync called by [%d] on ctx_fd=%d on=%d async_queue=%p ret=%d\n",
        task_pid_nr(current),
        fd,
        on,
        ctx->ctx_async_queue, ret));

    return ret;
}

static int
pfm_fasync(int fd, struct file *filp, int on)
{
    pfm_context_t *ctx;
    int ret;

    if (PFM_IS_FILE(filp) == 0) {
        printk(KERN_ERR "perfmon: pfm_fasync bad magic [%d]\n", task_pid_nr(current));
        return -EBADF;
    }

    ctx = filp->private_data;
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: pfm_fasync NULL ctx [%d]\n", task_pid_nr(current));
        return -EBADF;
    }
    /*
     * we cannot mask interrupts during this call because this may
     * may go to sleep if memory is not readily avalaible.
     *
     * We are protected from the conetxt disappearing by the get_fd()/put_fd()
     * done in caller. Serialization of this function is ensured by caller.
     */
    ret = pfm_do_fasync(fd, filp, ctx, on);


    DPRINT(("pfm_fasync called on ctx_fd=%d on=%d async_queue=%p ret=%d\n",
        fd,
        on,
        ctx->ctx_async_queue, ret));

    return ret;
}

#ifdef CONFIG_SMP
/*
 * this function is exclusively called from pfm_close().
 * The context is not protected at that time, nor are interrupts
 * on the remote CPU. That's necessary to avoid deadlocks.
 */
static void
pfm_syswide_force_stop(void *info)
{
    pfm_context_t   *ctx = (pfm_context_t *)info;
    struct pt_regs *regs = task_pt_regs(current);
    struct task_struct *owner;
    unsigned long flags;
    int ret;

    if (ctx->ctx_cpu != smp_processor_id()) {
        printk(KERN_ERR "perfmon: pfm_syswide_force_stop for CPU%d  but on CPU%d\n",
            ctx->ctx_cpu,
            smp_processor_id());
        return;
    }
    owner = GET_PMU_OWNER();
    if (owner != ctx->ctx_task) {
        printk(KERN_ERR "perfmon: pfm_syswide_force_stop CPU%d unexpected owner [%d] instead of [%d]\n",
            smp_processor_id(),
            task_pid_nr(owner), task_pid_nr(ctx->ctx_task));
        return;
    }
    if (GET_PMU_CTX() != ctx) {
        printk(KERN_ERR "perfmon: pfm_syswide_force_stop CPU%d unexpected ctx %p instead of %p\n",
            smp_processor_id(),
            GET_PMU_CTX(), ctx);
        return;
    }

    DPRINT(("on CPU%d forcing system wide stop for [%d]\n", smp_processor_id(), task_pid_nr(ctx->ctx_task)));
    /*
     * the context is already protected in pfm_close(), we simply
     * need to mask interrupts to avoid a PMU interrupt race on
     * this CPU
     */
    local_irq_save(flags);

    ret = pfm_context_unload(ctx, NULL, 0, regs);
    if (ret) {
        DPRINT(("context_unload returned %d\n", ret));
    }

    /*
     * unmask interrupts, PMU interrupts are now spurious here
     */
    local_irq_restore(flags);
}

static void
pfm_syswide_cleanup_other_cpu(pfm_context_t *ctx)
{
    int ret;

    DPRINT(("calling CPU%d for cleanup\n", ctx->ctx_cpu));
    ret = smp_call_function_single(ctx->ctx_cpu, pfm_syswide_force_stop, ctx, 1);
    DPRINT(("called CPU%d for cleanup ret=%d\n", ctx->ctx_cpu, ret));
}
#endif /* CONFIG_SMP */

/*
 * called for each close(). Partially free resources.
 * When caller is self-monitoring, the context is unloaded.
 */
static int
pfm_flush(struct file *filp, fl_owner_t id)
{
    pfm_context_t *ctx;
    struct task_struct *task;
    struct pt_regs *regs;
    unsigned long flags;
    unsigned long smpl_buf_size = 0UL;
    void *smpl_buf_vaddr = NULL;
    int state, is_system;

    if (PFM_IS_FILE(filp) == 0) {
        DPRINT(("bad magic for\n"));
        return -EBADF;
    }

    ctx = filp->private_data;
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: pfm_flush: NULL ctx [%d]\n", task_pid_nr(current));
        return -EBADF;
    }

    /*
     * remove our file from the async queue, if we use this mode.
     * This can be done without the context being protected. We come
     * here when the context has become unreachable by other tasks.
     *
     * We may still have active monitoring at this point and we may
     * end up in pfm_overflow_handler(). However, fasync_helper()
     * operates with interrupts disabled and it cleans up the
     * queue. If the PMU handler is called prior to entering
     * fasync_helper() then it will send a signal. If it is
     * invoked after, it will find an empty queue and no
     * signal will be sent. In both case, we are safe
     */
    PROTECT_CTX(ctx, flags);

    state     = ctx->ctx_state;
    is_system = ctx->ctx_fl_system;

    task = PFM_CTX_TASK(ctx);
    regs = task_pt_regs(task);

    DPRINT(("ctx_state=%d is_current=%d\n",
        state,
        task == current ? 1 : 0));

    /*
     * if state == UNLOADED, then task is NULL
     */

    /*
     * we must stop and unload because we are losing access to the context.
     */
    if (task == current) {
#ifdef CONFIG_SMP
        /*
         * the task IS the owner but it migrated to another CPU: that's bad
         * but we must handle this cleanly. Unfortunately, the kernel does
         * not provide a mechanism to block migration (while the context is loaded).
         *
         * We need to release the resource on the ORIGINAL cpu.
         */
        if (is_system && ctx->ctx_cpu != smp_processor_id()) {

            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            /*
             * keep context protected but unmask interrupt for IPI
             */
            local_irq_restore(flags);

            pfm_syswide_cleanup_other_cpu(ctx);

            /*
             * restore interrupt masking
             */
            local_irq_save(flags);

            /*
             * context is unloaded at this point
             */
        } else
#endif /* CONFIG_SMP */
        {

            DPRINT(("forcing unload\n"));
            /*
            * stop and unload, returning with state UNLOADED
            * and session unreserved.
            */
            pfm_context_unload(ctx, NULL, 0, regs);

            DPRINT(("ctx_state=%d\n", ctx->ctx_state));
        }
    }

    /*
     * remove virtual mapping, if any, for the calling task.
     * cannot reset ctx field until last user is calling close().
     *
     * ctx_smpl_vaddr must never be cleared because it is needed
     * by every task with access to the context
     *
     * When called from do_exit(), the mm context is gone already, therefore
     * mm is NULL, i.e., the VMA is already gone  and we do not have to
     * do anything here
     */
    if (ctx->ctx_smpl_vaddr && current->mm) {
        smpl_buf_vaddr = ctx->ctx_smpl_vaddr;
        smpl_buf_size  = ctx->ctx_smpl_size;
    }

    UNPROTECT_CTX(ctx, flags);

    /*
     * if there was a mapping, then we systematically remove it
     * at this point. Cannot be done inside critical section
     * because some VM function reenables interrupts.
     *
     */
    if (smpl_buf_vaddr) pfm_remove_smpl_mapping(smpl_buf_vaddr, smpl_buf_size);

    return 0;
}
/*
 * called either on explicit close() or from exit_files(). 
 * Only the LAST user of the file gets to this point, i.e., it is
 * called only ONCE.
 *
 * IMPORTANT: we get called ONLY when the refcnt on the file gets to zero 
 * (fput()),i.e, last task to access the file. Nobody else can access the 
 * file at this point.
 *
 * When called from exit_files(), the VMA has been freed because exit_mm()
 * is executed before exit_files().
 *
 * When called from exit_files(), the current task is not yet ZOMBIE but we
 * flush the PMU state to the context. 
 */
static int
pfm_close(struct inode *inode, struct file *filp)
{
    pfm_context_t *ctx;
    struct task_struct *task;
    struct pt_regs *regs;
    DECLARE_WAITQUEUE(wait, current);
    unsigned long flags;
    unsigned long smpl_buf_size = 0UL;
    void *smpl_buf_addr = NULL;
    int free_possible = 1;
    int state, is_system;

    DPRINT(("pfm_close called private=%p\n", filp->private_data));

    if (PFM_IS_FILE(filp) == 0) {
        DPRINT(("bad magic\n"));
        return -EBADF;
    }
    
    ctx = filp->private_data;
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: pfm_close: NULL ctx [%d]\n", task_pid_nr(current));
        return -EBADF;
    }

    PROTECT_CTX(ctx, flags);

    state     = ctx->ctx_state;
    is_system = ctx->ctx_fl_system;

    task = PFM_CTX_TASK(ctx);
    regs = task_pt_regs(task);

    DPRINT(("ctx_state=%d is_current=%d\n", 
        state,
        task == current ? 1 : 0));

    /*
     * if task == current, then pfm_flush() unloaded the context
     */
    if (state == PFM_CTX_UNLOADED) goto doit;

    /*
     * context is loaded/masked and task != current, we need to
     * either force an unload or go zombie
     */

    /*
     * The task is currently blocked or will block after an overflow.
     * we must force it to wakeup to get out of the
     * MASKED state and transition to the unloaded state by itself.
     *
     * This situation is only possible for per-task mode
     */
    if (state == PFM_CTX_MASKED && CTX_OVFL_NOBLOCK(ctx) == 0) {

        /*
         * set a "partial" zombie state to be checked
         * upon return from down() in pfm_handle_work().
         *
         * We cannot use the ZOMBIE state, because it is checked
         * by pfm_load_regs() which is called upon wakeup from down().
         * In such case, it would free the context and then we would
         * return to pfm_handle_work() which would access the
         * stale context. Instead, we set a flag invisible to pfm_load_regs()
         * but visible to pfm_handle_work().
         *
         * For some window of time, we have a zombie context with
         * ctx_state = MASKED  and not ZOMBIE
         */
        ctx->ctx_fl_going_zombie = 1;

        /*
         * force task to wake up from MASKED state
         */
        complete(&ctx->ctx_restart_done);

        DPRINT(("waking up ctx_state=%d\n", state));

        /*
         * put ourself to sleep waiting for the other
         * task to report completion
         *
         * the context is protected by mutex, therefore there
         * is no risk of being notified of completion before
         * begin actually on the waitq.
         */
        set_current_state(TASK_INTERRUPTIBLE);
        add_wait_queue(&ctx->ctx_zombieq, &wait);

        UNPROTECT_CTX(ctx, flags);

        /*
         * XXX: check for signals :
         *  - ok for explicit close
         *  - not ok when coming from exit_files()
         */
            schedule();


        PROTECT_CTX(ctx, flags);


        remove_wait_queue(&ctx->ctx_zombieq, &wait);
        set_current_state(TASK_RUNNING);

        /*
         * context is unloaded at this point
         */
        DPRINT(("after zombie wakeup ctx_state=%d for\n", state));
    }
    else if (task != current) {
#ifdef CONFIG_SMP
        /*
         * switch context to zombie state
         */
        ctx->ctx_state = PFM_CTX_ZOMBIE;

        DPRINT(("zombie ctx for [%d]\n", task_pid_nr(task)));
        /*
         * cannot free the context on the spot. deferred until
         * the task notices the ZOMBIE state
         */
        free_possible = 0;
#else
        pfm_context_unload(ctx, NULL, 0, regs);
#endif
    }

doit:
    /* reload state, may have changed during  opening of critical section */
    state = ctx->ctx_state;

    /*
     * the context is still attached to a task (possibly current)
     * we cannot destroy it right now
     */

    /*
     * we must free the sampling buffer right here because
     * we cannot rely on it being cleaned up later by the
     * monitored task. It is not possible to free vmalloc'ed
     * memory in pfm_load_regs(). Instead, we remove the buffer
     * now. should there be subsequent PMU overflow originally
     * meant for sampling, the will be converted to spurious
     * and that's fine because the monitoring tools is gone anyway.
     */
    if (ctx->ctx_smpl_hdr) {
        smpl_buf_addr = ctx->ctx_smpl_hdr;
        smpl_buf_size = ctx->ctx_smpl_size;
        /* no more sampling */
        ctx->ctx_smpl_hdr = NULL;
        ctx->ctx_fl_is_sampling = 0;
    }

    DPRINT(("ctx_state=%d free_possible=%d addr=%p size=%lu\n",
        state,
        free_possible,
        smpl_buf_addr,
        smpl_buf_size));

    if (smpl_buf_addr) pfm_exit_smpl_buffer(ctx->ctx_buf_fmt);

    /*
     * UNLOADED that the session has already been unreserved.
     */
    if (state == PFM_CTX_ZOMBIE) {
        pfm_unreserve_session(ctx, ctx->ctx_fl_system , ctx->ctx_cpu);
    }

    /*
     * disconnect file descriptor from context must be done
     * before we unlock.
     */
    filp->private_data = NULL;

    /*
     * if we free on the spot, the context is now completely unreachable
     * from the callers side. The monitored task side is also cut, so we
     * can freely cut.
     *
     * If we have a deferred free, only the caller side is disconnected.
     */
    UNPROTECT_CTX(ctx, flags);

    /*
     * All memory free operations (especially for vmalloc'ed memory)
     * MUST be done with interrupts ENABLED.
     */
    if (smpl_buf_addr)  pfm_rvfree(smpl_buf_addr, smpl_buf_size);

    /*
     * return the memory used by the context
     */
    if (free_possible) pfm_context_free(ctx);

    return 0;
}

static int
pfm_no_open(struct inode *irrelevant, struct file *dontcare)
{
    DPRINT(("pfm_no_open called\n"));
    return -ENXIO;
}



static const struct file_operations pfm_file_ops = {
    .llseek     = no_llseek,
    .read       = pfm_read,
    .write      = pfm_write,
    .poll       = pfm_poll,
    .unlocked_ioctl = pfm_ioctl,
    .open       = pfm_no_open,  /* special open code to disallow open via /proc */
    .fasync     = pfm_fasync,
    .release    = pfm_close,
    .flush      = pfm_flush
};

static int
pfmfs_delete_dentry(const struct dentry *dentry)
{
    return 1;
}

static char *pfmfs_dname(struct dentry *dentry, char *buffer, int buflen)
{
    return dynamic_dname(dentry, buffer, buflen, "pfm:[%lu]",
                 dentry->d_inode->i_ino);
}

static const struct dentry_operations pfmfs_dentry_operations = {
    .d_delete = pfmfs_delete_dentry,
    .d_dname = pfmfs_dname,
};


static struct file *
pfm_alloc_file(pfm_context_t *ctx)
{
    struct file *file;
    struct inode *inode;
    struct path path;
    struct qstr this = { .name = "" };

    /*
     * allocate a new inode
     */
    inode = new_inode(pfmfs_mnt->mnt_sb);
    if (!inode)
        return ERR_PTR(-ENOMEM);

    DPRINT(("new inode ino=%ld @%p\n", inode->i_ino, inode));

    inode->i_mode = S_IFCHR|S_IRUGO;
    inode->i_uid  = current_fsuid();
    inode->i_gid  = current_fsgid();

    /*
     * allocate a new dcache entry
     */
    path.dentry = d_alloc(pfmfs_mnt->mnt_root, &this);
    if (!path.dentry) {
        iput(inode);
        return ERR_PTR(-ENOMEM);
    }
    path.mnt = mntget(pfmfs_mnt);

    d_add(path.dentry, inode);

    file = alloc_file(&path, FMODE_READ, &pfm_file_ops);
    if (!file) {
        path_put(&path);
        return ERR_PTR(-ENFILE);
    }

    file->f_flags = O_RDONLY;
    file->private_data = ctx;

    return file;
}

static int
pfm_remap_buffer(struct vm_area_struct *vma, unsigned long buf, unsigned long addr, unsigned long size)
{
    DPRINT(("CPU%d buf=0x%lx addr=0x%lx size=%ld\n", smp_processor_id(), buf, addr, size));

    while (size > 0) {
        unsigned long pfn = ia64_tpa(buf) >> PAGE_SHIFT;


        if (remap_pfn_range(vma, addr, pfn, PAGE_SIZE, PAGE_READONLY))
            return -ENOMEM;

        addr  += PAGE_SIZE;
        buf   += PAGE_SIZE;
        size  -= PAGE_SIZE;
    }
    return 0;
}

/*
 * allocate a sampling buffer and remaps it into the user address space of the task
 */
static int
pfm_smpl_buffer_alloc(struct task_struct *task, struct file *filp, pfm_context_t *ctx, unsigned long rsize, void **user_vaddr)
{
    struct mm_struct *mm = task->mm;
    struct vm_area_struct *vma = NULL;
    unsigned long size;
    void *smpl_buf;


    /*
     * the fixed header + requested size and align to page boundary
     */
    size = PAGE_ALIGN(rsize);

    DPRINT(("sampling buffer rsize=%lu size=%lu bytes\n", rsize, size));

    /*
     * check requested size to avoid Denial-of-service attacks
     * XXX: may have to refine this test
     * Check against address space limit.
     *
     * if ((mm->total_vm << PAGE_SHIFT) + len> task->rlim[RLIMIT_AS].rlim_cur)
     *  return -ENOMEM;
     */
    if (size > task_rlimit(task, RLIMIT_MEMLOCK))
        return -ENOMEM;

    /*
     * We do the easy to undo allocations first.
     *
     * pfm_rvmalloc(), clears the buffer, so there is no leak
     */
    smpl_buf = pfm_rvmalloc(size);
    if (smpl_buf == NULL) {
        DPRINT(("Can't allocate sampling buffer\n"));
        return -ENOMEM;
    }

    DPRINT(("smpl_buf @%p\n", smpl_buf));

    /* allocate vma */
    vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
    if (!vma) {
        DPRINT(("Cannot allocate vma\n"));
        goto error_kmem;
    }
    INIT_LIST_HEAD(&vma->anon_vma_chain);

    /*
     * partially initialize the vma for the sampling buffer
     */
    vma->vm_mm       = mm;
    vma->vm_file         = get_file(filp);
    vma->vm_flags        = VM_READ|VM_MAYREAD|VM_DONTEXPAND|VM_DONTDUMP;
    vma->vm_page_prot    = PAGE_READONLY; /* XXX may need to change */

    /*
     * Now we have everything we need and we can initialize
     * and connect all the data structures
     */

    ctx->ctx_smpl_hdr   = smpl_buf;
    ctx->ctx_smpl_size  = size; /* aligned size */

    /*
     * Let's do the difficult operations next.
     *
     * now we atomically find some area in the address space and
     * remap the buffer in it.
     */
    down_write(&task->mm->mmap_sem);

    /* find some free area in address space, must have mmap sem held */
    vma->vm_start = get_unmapped_area(NULL, 0, size, 0, MAP_PRIVATE|MAP_ANONYMOUS);
    if (IS_ERR_VALUE(vma->vm_start)) {
        DPRINT(("Cannot find unmapped area for size %ld\n", size));
        up_write(&task->mm->mmap_sem);
        goto error;
    }
    vma->vm_end = vma->vm_start + size;
    vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;

    DPRINT(("aligned size=%ld, hdr=%p mapped @0x%lx\n", size, ctx->ctx_smpl_hdr, vma->vm_start));

    /* can only be applied to current task, need to have the mm semaphore held when called */
    if (pfm_remap_buffer(vma, (unsigned long)smpl_buf, vma->vm_start, size)) {
        DPRINT(("Can't remap buffer\n"));
        up_write(&task->mm->mmap_sem);
        goto error;
    }

    /*
     * now insert the vma in the vm list for the process, must be
     * done with mmap lock held
     */
    insert_vm_struct(mm, vma);

    vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file,
                            vma_pages(vma));
    up_write(&task->mm->mmap_sem);

    /*
     * keep track of user level virtual address
     */
    ctx->ctx_smpl_vaddr = (void *)vma->vm_start;
    *(unsigned long *)user_vaddr = vma->vm_start;

    return 0;

error:
    kmem_cache_free(vm_area_cachep, vma);
error_kmem:
    pfm_rvfree(smpl_buf, size);

    return -ENOMEM;
}

/*
 * XXX: do something better here
 */
static int
pfm_bad_permissions(struct task_struct *task)
{
    const struct cred *tcred;
    kuid_t uid = current_uid();
    kgid_t gid = current_gid();
    int ret;

    rcu_read_lock();
    tcred = __task_cred(task);

    /* inspired by ptrace_attach() */
    DPRINT(("cur: uid=%d gid=%d task: euid=%d suid=%d uid=%d egid=%d sgid=%d\n",
        from_kuid(&init_user_ns, uid),
        from_kgid(&init_user_ns, gid),
        from_kuid(&init_user_ns, tcred->euid),
        from_kuid(&init_user_ns, tcred->suid),
        from_kuid(&init_user_ns, tcred->uid),
        from_kgid(&init_user_ns, tcred->egid),
        from_kgid(&init_user_ns, tcred->sgid)));

    ret = ((!uid_eq(uid, tcred->euid))
           || (!uid_eq(uid, tcred->suid))
           || (!uid_eq(uid, tcred->uid))
           || (!gid_eq(gid, tcred->egid))
           || (!gid_eq(gid, tcred->sgid))
           || (!gid_eq(gid, tcred->gid))) && !capable(CAP_SYS_PTRACE);

    rcu_read_unlock();
    return ret;
}

static int
pfarg_is_sane(struct task_struct *task, pfarg_context_t *pfx)
{
    int ctx_flags;

    /* valid signal */

    ctx_flags = pfx->ctx_flags;

    if (ctx_flags & PFM_FL_SYSTEM_WIDE) {

        /*
         * cannot block in this mode
         */
        if (ctx_flags & PFM_FL_NOTIFY_BLOCK) {
            DPRINT(("cannot use blocking mode when in system wide monitoring\n"));
            return -EINVAL;
        }
    } else {
    }
    /* probably more to add here */

    return 0;
}

static int
pfm_setup_buffer_fmt(struct task_struct *task, struct file *filp, pfm_context_t *ctx, unsigned int ctx_flags,
             unsigned int cpu, pfarg_context_t *arg)
{
    pfm_buffer_fmt_t *fmt = NULL;
    unsigned long size = 0UL;
    void *uaddr = NULL;
    void *fmt_arg = NULL;
    int ret = 0;
#define PFM_CTXARG_BUF_ARG(a)   (pfm_buffer_fmt_t *)(a+1)

    /* invoke and lock buffer format, if found */
    fmt = pfm_find_buffer_fmt(arg->ctx_smpl_buf_id);
    if (fmt == NULL) {
        DPRINT(("[%d] cannot find buffer format\n", task_pid_nr(task)));
        return -EINVAL;
    }

    /*
     * buffer argument MUST be contiguous to pfarg_context_t
     */
    if (fmt->fmt_arg_size) fmt_arg = PFM_CTXARG_BUF_ARG(arg);

    ret = pfm_buf_fmt_validate(fmt, task, ctx_flags, cpu, fmt_arg);

    DPRINT(("[%d] after validate(0x%x,%d,%p)=%d\n", task_pid_nr(task), ctx_flags, cpu, fmt_arg, ret));

    if (ret) goto error;

    /* link buffer format and context */
    ctx->ctx_buf_fmt = fmt;
    ctx->ctx_fl_is_sampling = 1; /* assume record() is defined */

    /*
     * check if buffer format wants to use perfmon buffer allocation/mapping service
     */
    ret = pfm_buf_fmt_getsize(fmt, task, ctx_flags, cpu, fmt_arg, &size);
    if (ret) goto error;

    if (size) {
        /*
         * buffer is always remapped into the caller's address space
         */
        ret = pfm_smpl_buffer_alloc(current, filp, ctx, size, &uaddr);
        if (ret) goto error;

        /* keep track of user address of buffer */
        arg->ctx_smpl_vaddr = uaddr;
    }
    ret = pfm_buf_fmt_init(fmt, task, ctx->ctx_smpl_hdr, ctx_flags, cpu, fmt_arg);

error:
    return ret;
}

static void
pfm_reset_pmu_state(pfm_context_t *ctx)
{
    int i;

    /*
     * install reset values for PMC.
     */
    for (i=1; PMC_IS_LAST(i) == 0; i++) {
        if (PMC_IS_IMPL(i) == 0) continue;
        ctx->ctx_pmcs[i] = PMC_DFL_VAL(i);
        DPRINT(("pmc[%d]=0x%lx\n", i, ctx->ctx_pmcs[i]));
    }
    /*
     * PMD registers are set to 0UL when the context in memset()
     */

    /*
     * On context switched restore, we must restore ALL pmc and ALL pmd even
     * when they are not actively used by the task. In UP, the incoming process
     * may otherwise pick up left over PMC, PMD state from the previous process.
     * As opposed to PMD, stale PMC can cause harm to the incoming
     * process because they may change what is being measured.
     * Therefore, we must systematically reinstall the entire
     * PMC state. In SMP, the same thing is possible on the
     * same CPU but also on between 2 CPUs.
     *
     * The problem with PMD is information leaking especially
     * to user level when psr.sp=0
     *
     * There is unfortunately no easy way to avoid this problem
     * on either UP or SMP. This definitively slows down the
     * pfm_load_regs() function.
     */

     /*
      * bitmask of all PMCs accessible to this context
      *
      * PMC0 is treated differently.
      */
    ctx->ctx_all_pmcs[0] = pmu_conf->impl_pmcs[0] & ~0x1;

    /*
     * bitmask of all PMDs that are accessible to this context
     */
    ctx->ctx_all_pmds[0] = pmu_conf->impl_pmds[0];

    DPRINT(("<%d> all_pmcs=0x%lx all_pmds=0x%lx\n", ctx->ctx_fd, ctx->ctx_all_pmcs[0],ctx->ctx_all_pmds[0]));

    /*
     * useful in case of re-enable after disable
     */
    ctx->ctx_used_ibrs[0] = 0UL;
    ctx->ctx_used_dbrs[0] = 0UL;
}

static int
pfm_ctx_getsize(void *arg, size_t *sz)
{
    pfarg_context_t *req = (pfarg_context_t *)arg;
    pfm_buffer_fmt_t *fmt;

    *sz = 0;

    if (!pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) return 0;

    fmt = pfm_find_buffer_fmt(req->ctx_smpl_buf_id);
    if (fmt == NULL) {
        DPRINT(("cannot find buffer format\n"));
        return -EINVAL;
    }
    /* get just enough to copy in user parameters */
    *sz = fmt->fmt_arg_size;
    DPRINT(("arg_size=%lu\n", *sz));

    return 0;
}



/*
 * cannot attach if :
 *  - kernel task
 *  - task not owned by caller
 *  - task incompatible with context mode
 */
static int
pfm_task_incompatible(pfm_context_t *ctx, struct task_struct *task)
{
    /*
     * no kernel task or task not owner by caller
     */
    if (task->mm == NULL) {
        DPRINT(("task [%d] has not memory context (kernel thread)\n", task_pid_nr(task)));
        return -EPERM;
    }
    if (pfm_bad_permissions(task)) {
        DPRINT(("no permission to attach to  [%d]\n", task_pid_nr(task)));
        return -EPERM;
    }
    /*
     * cannot block in self-monitoring mode
     */
    if (CTX_OVFL_NOBLOCK(ctx) == 0 && task == current) {
        DPRINT(("cannot load a blocking context on self for [%d]\n", task_pid_nr(task)));
        return -EINVAL;
    }

    if (task->exit_state == EXIT_ZOMBIE) {
        DPRINT(("cannot attach to  zombie task [%d]\n", task_pid_nr(task)));
        return -EBUSY;
    }

    /*
     * always ok for self
     */
    if (task == current) return 0;

    if (!task_is_stopped_or_traced(task)) {
        DPRINT(("cannot attach to non-stopped task [%d] state=%ld\n", task_pid_nr(task), task->state));
        return -EBUSY;
    }
    /*
     * make sure the task is off any CPU
     */
    wait_task_inactive(task, 0);

    /* more to come... */

    return 0;
}

static int
pfm_get_task(pfm_context_t *ctx, pid_t pid, struct task_struct **task)
{
    struct task_struct *p = current;
    int ret;

    /* XXX: need to add more checks here */
    if (pid < 2) return -EPERM;

    if (pid != task_pid_vnr(current)) {

        read_lock(&tasklist_lock);

        p = find_task_by_vpid(pid);

        /* make sure task cannot go away while we operate on it */
        if (p) get_task_struct(p);

        read_unlock(&tasklist_lock);

        if (p == NULL) return -ESRCH;
    }

    ret = pfm_task_incompatible(ctx, p);
    if (ret == 0) {
        *task = p;
    } else if (p != current) {
        pfm_put_task(p);
    }
    return ret;
}



static int
pfm_context_create(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    pfarg_context_t *req = (pfarg_context_t *)arg;
    struct file *filp;
    struct path path;
    int ctx_flags;
    int fd;
    int ret;

    /* let's check the arguments first */
    ret = pfarg_is_sane(current, req);
    if (ret < 0)
        return ret;

    ctx_flags = req->ctx_flags;

    ret = -ENOMEM;

    fd = get_unused_fd();
    if (fd < 0)
        return fd;

    ctx = pfm_context_alloc(ctx_flags);
    if (!ctx)
        goto error;

    filp = pfm_alloc_file(ctx);
    if (IS_ERR(filp)) {
        ret = PTR_ERR(filp);
        goto error_file;
    }

    req->ctx_fd = ctx->ctx_fd = fd;

    /*
     * does the user want to sample?
     */
    if (pfm_uuid_cmp(req->ctx_smpl_buf_id, pfm_null_uuid)) {
        ret = pfm_setup_buffer_fmt(current, filp, ctx, ctx_flags, 0, req);
        if (ret)
            goto buffer_error;
    }

    DPRINT(("ctx=%p flags=0x%x system=%d notify_block=%d excl_idle=%d no_msg=%d ctx_fd=%d\n",
        ctx,
        ctx_flags,
        ctx->ctx_fl_system,
        ctx->ctx_fl_block,
        ctx->ctx_fl_excl_idle,
        ctx->ctx_fl_no_msg,
        ctx->ctx_fd));

    /*
     * initialize soft PMU state
     */
    pfm_reset_pmu_state(ctx);

    fd_install(fd, filp);

    return 0;

buffer_error:
    path = filp->f_path;
    put_filp(filp);
    path_put(&path);

    if (ctx->ctx_buf_fmt) {
        pfm_buf_fmt_exit(ctx->ctx_buf_fmt, current, NULL, regs);
    }
error_file:
    pfm_context_free(ctx);

error:
    put_unused_fd(fd);
    return ret;
}

static inline unsigned long
pfm_new_counter_value (pfm_counter_t *reg, int is_long_reset)
{
    unsigned long val = is_long_reset ? reg->long_reset : reg->short_reset;
    unsigned long new_seed, old_seed = reg->seed, mask = reg->mask;
    extern unsigned long carta_random32 (unsigned long seed);

    if (reg->flags & PFM_REGFL_RANDOM) {
        new_seed = carta_random32(old_seed);
        val -= (old_seed & mask);   /* counter values are negative numbers! */
        if ((mask >> 32) != 0)
            /* construct a full 64-bit random value: */
            new_seed |= carta_random32(old_seed >> 32) << 32;
        reg->seed = new_seed;
    }
    reg->lval = val;
    return val;
}

static void
pfm_reset_regs_masked(pfm_context_t *ctx, unsigned long *ovfl_regs, int is_long_reset)
{
    unsigned long mask = ovfl_regs[0];
    unsigned long reset_others = 0UL;
    unsigned long val;
    int i;

    /*
     * now restore reset value on sampling overflowed counters
     */
    mask >>= PMU_FIRST_COUNTER;
    for(i = PMU_FIRST_COUNTER; mask; i++, mask >>= 1) {

        if ((mask & 0x1UL) == 0UL) continue;

        ctx->ctx_pmds[i].val = val = pfm_new_counter_value(ctx->ctx_pmds+ i, is_long_reset);
        reset_others        |= ctx->ctx_pmds[i].reset_pmds[0];

        DPRINT_ovfl((" %s reset ctx_pmds[%d]=%lx\n", is_long_reset ? "long" : "short", i, val));
    }

    /*
     * Now take care of resetting the other registers
     */
    for(i = 0; reset_others; i++, reset_others >>= 1) {

        if ((reset_others & 0x1) == 0) continue;

        ctx->ctx_pmds[i].val = val = pfm_new_counter_value(ctx->ctx_pmds + i, is_long_reset);

        DPRINT_ovfl(("%s reset_others pmd[%d]=%lx\n",
              is_long_reset ? "long" : "short", i, val));
    }
}

static void
pfm_reset_regs(pfm_context_t *ctx, unsigned long *ovfl_regs, int is_long_reset)
{
    unsigned long mask = ovfl_regs[0];
    unsigned long reset_others = 0UL;
    unsigned long val;
    int i;

    DPRINT_ovfl(("ovfl_regs=0x%lx is_long_reset=%d\n", ovfl_regs[0], is_long_reset));

    if (ctx->ctx_state == PFM_CTX_MASKED) {
        pfm_reset_regs_masked(ctx, ovfl_regs, is_long_reset);
        return;
    }

    /*
     * now restore reset value on sampling overflowed counters
     */
    mask >>= PMU_FIRST_COUNTER;
    for(i = PMU_FIRST_COUNTER; mask; i++, mask >>= 1) {

        if ((mask & 0x1UL) == 0UL) continue;

        val           = pfm_new_counter_value(ctx->ctx_pmds+ i, is_long_reset);
        reset_others |= ctx->ctx_pmds[i].reset_pmds[0];

        DPRINT_ovfl((" %s reset ctx_pmds[%d]=%lx\n", is_long_reset ? "long" : "short", i, val));

        pfm_write_soft_counter(ctx, i, val);
    }

    /*
     * Now take care of resetting the other registers
     */
    for(i = 0; reset_others; i++, reset_others >>= 1) {

        if ((reset_others & 0x1) == 0) continue;

        val = pfm_new_counter_value(ctx->ctx_pmds + i, is_long_reset);

        if (PMD_IS_COUNTING(i)) {
            pfm_write_soft_counter(ctx, i, val);
        } else {
            ia64_set_pmd(i, val);
        }
        DPRINT_ovfl(("%s reset_others pmd[%d]=%lx\n",
              is_long_reset ? "long" : "short", i, val));
    }
    ia64_srlz_d();
}

static int
pfm_write_pmcs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task;
    pfarg_reg_t *req = (pfarg_reg_t *)arg;
    unsigned long value, pmc_pm;
    unsigned long smpl_pmds, reset_pmds, impl_pmds;
    unsigned int cnum, reg_flags, flags, pmc_type;
    int i, can_access_pmu = 0, is_loaded, is_system, expert_mode;
    int is_monitor, is_counting, state;
    int ret = -EINVAL;
    pfm_reg_check_t wr_func;
#define PFM_CHECK_PMC_PM(x, y, z) ((x)->ctx_fl_system ^ PMC_PM(y, z))

    state     = ctx->ctx_state;
    is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
    is_system = ctx->ctx_fl_system;
    task      = ctx->ctx_task;
    impl_pmds = pmu_conf->impl_pmds[0];

    if (state == PFM_CTX_ZOMBIE) return -EINVAL;

    if (is_loaded) {
        /*
         * In system wide and when the context is loaded, access can only happen
         * when the caller is running on the CPU being monitored by the session.
         * It does not have to be the owner (ctx_task) of the context per se.
         */
        if (is_system && ctx->ctx_cpu != smp_processor_id()) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
        }
        can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
    }
    expert_mode = pfm_sysctl.expert_mode; 

    for (i = 0; i < count; i++, req++) {

        cnum       = req->reg_num;
        reg_flags  = req->reg_flags;
        value      = req->reg_value;
        smpl_pmds  = req->reg_smpl_pmds[0];
        reset_pmds = req->reg_reset_pmds[0];
        flags      = 0;


        if (cnum >= PMU_MAX_PMCS) {
            DPRINT(("pmc%u is invalid\n", cnum));
            goto error;
        }

        pmc_type   = pmu_conf->pmc_desc[cnum].type;
        pmc_pm     = (value >> pmu_conf->pmc_desc[cnum].pm_pos) & 0x1;
        is_counting = (pmc_type & PFM_REG_COUNTING) == PFM_REG_COUNTING ? 1 : 0;
        is_monitor  = (pmc_type & PFM_REG_MONITOR) == PFM_REG_MONITOR ? 1 : 0;

        /*
         * we reject all non implemented PMC as well
         * as attempts to modify PMC[0-3] which are used
         * as status registers by the PMU
         */
        if ((pmc_type & PFM_REG_IMPL) == 0 || (pmc_type & PFM_REG_CONTROL) == PFM_REG_CONTROL) {
            DPRINT(("pmc%u is unimplemented or no-access pmc_type=%x\n", cnum, pmc_type));
            goto error;
        }
        wr_func = pmu_conf->pmc_desc[cnum].write_check;
        /*
         * If the PMC is a monitor, then if the value is not the default:
         *  - system-wide session: PMCx.pm=1 (privileged monitor)
         *  - per-task           : PMCx.pm=0 (user monitor)
         */
        if (is_monitor && value != PMC_DFL_VAL(cnum) && is_system ^ pmc_pm) {
            DPRINT(("pmc%u pmc_pm=%lu is_system=%d\n",
                cnum,
                pmc_pm,
                is_system));
            goto error;
        }

        if (is_counting) {
            /*
             * enforce generation of overflow interrupt. Necessary on all
             * CPUs.
             */
            value |= 1 << PMU_PMC_OI;

            if (reg_flags & PFM_REGFL_OVFL_NOTIFY) {
                flags |= PFM_REGFL_OVFL_NOTIFY;
            }

            if (reg_flags & PFM_REGFL_RANDOM) flags |= PFM_REGFL_RANDOM;

            /* verify validity of smpl_pmds */
            if ((smpl_pmds & impl_pmds) != smpl_pmds) {
                DPRINT(("invalid smpl_pmds 0x%lx for pmc%u\n", smpl_pmds, cnum));
                goto error;
            }

            /* verify validity of reset_pmds */
            if ((reset_pmds & impl_pmds) != reset_pmds) {
                DPRINT(("invalid reset_pmds 0x%lx for pmc%u\n", reset_pmds, cnum));
                goto error;
            }
        } else {
            if (reg_flags & (PFM_REGFL_OVFL_NOTIFY|PFM_REGFL_RANDOM)) {
                DPRINT(("cannot set ovfl_notify or random on pmc%u\n", cnum));
                goto error;
            }
            /* eventid on non-counting monitors are ignored */
        }

        /*
         * execute write checker, if any
         */
        if (likely(expert_mode == 0 && wr_func)) {
            ret = (*wr_func)(task, ctx, cnum, &value, regs);
            if (ret) goto error;
            ret = -EINVAL;
        }

        /*
         * no error on this register
         */
        PFM_REG_RETFLAG_SET(req->reg_flags, 0);

        /*
         * Now we commit the changes to the software state
         */

        /*
         * update overflow information
         */
        if (is_counting) {
            /*
             * full flag update each time a register is programmed
             */
            ctx->ctx_pmds[cnum].flags = flags;

            ctx->ctx_pmds[cnum].reset_pmds[0] = reset_pmds;
            ctx->ctx_pmds[cnum].smpl_pmds[0]  = smpl_pmds;
            ctx->ctx_pmds[cnum].eventid       = req->reg_smpl_eventid;

            /*
             * Mark all PMDS to be accessed as used.
             *
             * We do not keep track of PMC because we have to
             * systematically restore ALL of them.
             *
             * We do not update the used_monitors mask, because
             * if we have not programmed them, then will be in
             * a quiescent state, therefore we will not need to
             * mask/restore then when context is MASKED.
             */
            CTX_USED_PMD(ctx, reset_pmds);
            CTX_USED_PMD(ctx, smpl_pmds);
            /*
             * make sure we do not try to reset on
             * restart because we have established new values
             */
            if (state == PFM_CTX_MASKED) ctx->ctx_ovfl_regs[0] &= ~1UL << cnum;
        }
        /*
         * Needed in case the user does not initialize the equivalent
         * PMD. Clearing is done indirectly via pfm_reset_pmu_state() so there is no
         * possible leak here.
         */
        CTX_USED_PMD(ctx, pmu_conf->pmc_desc[cnum].dep_pmd[0]);

        /*
         * keep track of the monitor PMC that we are using.
         * we save the value of the pmc in ctx_pmcs[] and if
         * the monitoring is not stopped for the context we also
         * place it in the saved state area so that it will be
         * picked up later by the context switch code.
         *
         * The value in ctx_pmcs[] can only be changed in pfm_write_pmcs().
         *
         * The value in th_pmcs[] may be modified on overflow, i.e.,  when
         * monitoring needs to be stopped.
         */
        if (is_monitor) CTX_USED_MONITOR(ctx, 1UL << cnum);

        /*
         * update context state
         */
        ctx->ctx_pmcs[cnum] = value;

        if (is_loaded) {
            /*
             * write thread state
             */
            if (is_system == 0) ctx->th_pmcs[cnum] = value;

            /*
             * write hardware register if we can
             */
            if (can_access_pmu) {
                ia64_set_pmc(cnum, value);
            }
#ifdef CONFIG_SMP
            else {
                /*
                 * per-task SMP only here
                 *
                 * we are guaranteed that the task is not running on the other CPU,
                 * we indicate that this PMD will need to be reloaded if the task
                 * is rescheduled on the CPU it ran last on.
                 */
                ctx->ctx_reload_pmcs[0] |= 1UL << cnum;
            }
#endif
        }

        DPRINT(("pmc[%u]=0x%lx ld=%d apmu=%d flags=0x%x all_pmcs=0x%lx used_pmds=0x%lx eventid=%ld smpl_pmds=0x%lx reset_pmds=0x%lx reloads_pmcs=0x%lx used_monitors=0x%lx ovfl_regs=0x%lx\n",
              cnum,
              value,
              is_loaded,
              can_access_pmu,
              flags,
              ctx->ctx_all_pmcs[0],
              ctx->ctx_used_pmds[0],
              ctx->ctx_pmds[cnum].eventid,
              smpl_pmds,
              reset_pmds,
              ctx->ctx_reload_pmcs[0],
              ctx->ctx_used_monitors[0],
              ctx->ctx_ovfl_regs[0]));
    }

    /*
     * make sure the changes are visible
     */
    if (can_access_pmu) ia64_srlz_d();

    return 0;
error:
    PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
    return ret;
}

static int
pfm_write_pmds(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task;
    pfarg_reg_t *req = (pfarg_reg_t *)arg;
    unsigned long value, hw_value, ovfl_mask;
    unsigned int cnum;
    int i, can_access_pmu = 0, state;
    int is_counting, is_loaded, is_system, expert_mode;
    int ret = -EINVAL;
    pfm_reg_check_t wr_func;


    state     = ctx->ctx_state;
    is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
    is_system = ctx->ctx_fl_system;
    ovfl_mask = pmu_conf->ovfl_val;
    task      = ctx->ctx_task;

    if (unlikely(state == PFM_CTX_ZOMBIE)) return -EINVAL;

    /*
     * on both UP and SMP, we can only write to the PMC when the task is
     * the owner of the local PMU.
     */
    if (likely(is_loaded)) {
        /*
         * In system wide and when the context is loaded, access can only happen
         * when the caller is running on the CPU being monitored by the session.
         * It does not have to be the owner (ctx_task) of the context per se.
         */
        if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
        }
        can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
    }
    expert_mode = pfm_sysctl.expert_mode; 

    for (i = 0; i < count; i++, req++) {

        cnum  = req->reg_num;
        value = req->reg_value;

        if (!PMD_IS_IMPL(cnum)) {
            DPRINT(("pmd[%u] is unimplemented or invalid\n", cnum));
            goto abort_mission;
        }
        is_counting = PMD_IS_COUNTING(cnum);
        wr_func     = pmu_conf->pmd_desc[cnum].write_check;

        /*
         * execute write checker, if any
         */
        if (unlikely(expert_mode == 0 && wr_func)) {
            unsigned long v = value;

            ret = (*wr_func)(task, ctx, cnum, &v, regs);
            if (ret) goto abort_mission;

            value = v;
            ret   = -EINVAL;
        }

        /*
         * no error on this register
         */
        PFM_REG_RETFLAG_SET(req->reg_flags, 0);

        /*
         * now commit changes to software state
         */
        hw_value = value;

        /*
         * update virtualized (64bits) counter
         */
        if (is_counting) {
            /*
             * write context state
             */
            ctx->ctx_pmds[cnum].lval = value;

            /*
             * when context is load we use the split value
             */
            if (is_loaded) {
                hw_value = value &  ovfl_mask;
                value    = value & ~ovfl_mask;
            }
        }
        /*
         * update reset values (not just for counters)
         */
        ctx->ctx_pmds[cnum].long_reset  = req->reg_long_reset;
        ctx->ctx_pmds[cnum].short_reset = req->reg_short_reset;

        /*
         * update randomization parameters (not just for counters)
         */
        ctx->ctx_pmds[cnum].seed = req->reg_random_seed;
        ctx->ctx_pmds[cnum].mask = req->reg_random_mask;

        /*
         * update context value
         */
        ctx->ctx_pmds[cnum].val  = value;

        /*
         * Keep track of what we use
         *
         * We do not keep track of PMC because we have to
         * systematically restore ALL of them.
         */
        CTX_USED_PMD(ctx, PMD_PMD_DEP(cnum));

        /*
         * mark this PMD register used as well
         */
        CTX_USED_PMD(ctx, RDEP(cnum));

        /*
         * make sure we do not try to reset on
         * restart because we have established new values
         */
        if (is_counting && state == PFM_CTX_MASKED) {
            ctx->ctx_ovfl_regs[0] &= ~1UL << cnum;
        }

        if (is_loaded) {
            /*
             * write thread state
             */
            if (is_system == 0) ctx->th_pmds[cnum] = hw_value;

            /*
             * write hardware register if we can
             */
            if (can_access_pmu) {
                ia64_set_pmd(cnum, hw_value);
            } else {
#ifdef CONFIG_SMP
                /*
                 * we are guaranteed that the task is not running on the other CPU,
                 * we indicate that this PMD will need to be reloaded if the task
                 * is rescheduled on the CPU it ran last on.
                 */
                ctx->ctx_reload_pmds[0] |= 1UL << cnum;
#endif
            }
        }

        DPRINT(("pmd[%u]=0x%lx ld=%d apmu=%d, hw_value=0x%lx ctx_pmd=0x%lx  short_reset=0x%lx "
              "long_reset=0x%lx notify=%c seed=0x%lx mask=0x%lx used_pmds=0x%lx reset_pmds=0x%lx reload_pmds=0x%lx all_pmds=0x%lx ovfl_regs=0x%lx\n",
            cnum,
            value,
            is_loaded,
            can_access_pmu,
            hw_value,
            ctx->ctx_pmds[cnum].val,
            ctx->ctx_pmds[cnum].short_reset,
            ctx->ctx_pmds[cnum].long_reset,
            PMC_OVFL_NOTIFY(ctx, cnum) ? 'Y':'N',
            ctx->ctx_pmds[cnum].seed,
            ctx->ctx_pmds[cnum].mask,
            ctx->ctx_used_pmds[0],
            ctx->ctx_pmds[cnum].reset_pmds[0],
            ctx->ctx_reload_pmds[0],
            ctx->ctx_all_pmds[0],
            ctx->ctx_ovfl_regs[0]));
    }

    /*
     * make changes visible
     */
    if (can_access_pmu) ia64_srlz_d();

    return 0;

abort_mission:
    /*
     * for now, we have only one possibility for error
     */
    PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
    return ret;
}

/*
 * By the way of PROTECT_CONTEXT(), interrupts are masked while we are in this function.
 * Therefore we know, we do not have to worry about the PMU overflow interrupt. If an
 * interrupt is delivered during the call, it will be kept pending until we leave, making
 * it appears as if it had been generated at the UNPROTECT_CONTEXT(). At least we are
 * guaranteed to return consistent data to the user, it may simply be old. It is not
 * trivial to treat the overflow while inside the call because you may end up in
 * some module sampling buffer code causing deadlocks.
 */
static int
pfm_read_pmds(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task;
    unsigned long val = 0UL, lval, ovfl_mask, sval;
    pfarg_reg_t *req = (pfarg_reg_t *)arg;
    unsigned int cnum, reg_flags = 0;
    int i, can_access_pmu = 0, state;
    int is_loaded, is_system, is_counting, expert_mode;
    int ret = -EINVAL;
    pfm_reg_check_t rd_func;

    /*
     * access is possible when loaded only for
     * self-monitoring tasks or in UP mode
     */

    state     = ctx->ctx_state;
    is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
    is_system = ctx->ctx_fl_system;
    ovfl_mask = pmu_conf->ovfl_val;
    task      = ctx->ctx_task;

    if (state == PFM_CTX_ZOMBIE) return -EINVAL;

    if (likely(is_loaded)) {
        /*
         * In system wide and when the context is loaded, access can only happen
         * when the caller is running on the CPU being monitored by the session.
         * It does not have to be the owner (ctx_task) of the context per se.
         */
        if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
        }
        /*
         * this can be true when not self-monitoring only in UP
         */
        can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;

        if (can_access_pmu) ia64_srlz_d();
    }
    expert_mode = pfm_sysctl.expert_mode; 

    DPRINT(("ld=%d apmu=%d ctx_state=%d\n",
        is_loaded,
        can_access_pmu,
        state));

    /*
     * on both UP and SMP, we can only read the PMD from the hardware register when
     * the task is the owner of the local PMU.
     */

    for (i = 0; i < count; i++, req++) {

        cnum        = req->reg_num;
        reg_flags   = req->reg_flags;

        if (unlikely(!PMD_IS_IMPL(cnum))) goto error;
        /*
         * we can only read the register that we use. That includes
         * the one we explicitly initialize AND the one we want included
         * in the sampling buffer (smpl_regs).
         *
         * Having this restriction allows optimization in the ctxsw routine
         * without compromising security (leaks)
         */
        if (unlikely(!CTX_IS_USED_PMD(ctx, cnum))) goto error;

        sval        = ctx->ctx_pmds[cnum].val;
        lval        = ctx->ctx_pmds[cnum].lval;
        is_counting = PMD_IS_COUNTING(cnum);

        /*
         * If the task is not the current one, then we check if the
         * PMU state is still in the local live register due to lazy ctxsw.
         * If true, then we read directly from the registers.
         */
        if (can_access_pmu){
            val = ia64_get_pmd(cnum);
        } else {
            /*
             * context has been saved
             * if context is zombie, then task does not exist anymore.
             * In this case, we use the full value saved in the context (pfm_flush_regs()).
             */
            val = is_loaded ? ctx->th_pmds[cnum] : 0UL;
        }
        rd_func = pmu_conf->pmd_desc[cnum].read_check;

        if (is_counting) {
            /*
             * XXX: need to check for overflow when loaded
             */
            val &= ovfl_mask;
            val += sval;
        }

        /*
         * execute read checker, if any
         */
        if (unlikely(expert_mode == 0 && rd_func)) {
            unsigned long v = val;
            ret = (*rd_func)(ctx->ctx_task, ctx, cnum, &v, regs);
            if (ret) goto error;
            val = v;
            ret = -EINVAL;
        }

        PFM_REG_RETFLAG_SET(reg_flags, 0);

        DPRINT(("pmd[%u]=0x%lx\n", cnum, val));

        /*
         * update register return value, abort all if problem during copy.
         * we only modify the reg_flags field. no check mode is fine because
         * access has been verified upfront in sys_perfmonctl().
         */
        req->reg_value            = val;
        req->reg_flags            = reg_flags;
        req->reg_last_reset_val   = lval;
    }

    return 0;

error:
    PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
    return ret;
}

int
pfm_mod_write_pmcs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
    pfm_context_t *ctx;

    if (req == NULL) return -EINVAL;

    ctx = GET_PMU_CTX();

    if (ctx == NULL) return -EINVAL;

    /*
     * for now limit to current task, which is enough when calling
     * from overflow handler
     */
    if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

    return pfm_write_pmcs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_pmcs);

int
pfm_mod_read_pmds(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
    pfm_context_t *ctx;

    if (req == NULL) return -EINVAL;

    ctx = GET_PMU_CTX();

    if (ctx == NULL) return -EINVAL;

    /*
     * for now limit to current task, which is enough when calling
     * from overflow handler
     */
    if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

    return pfm_read_pmds(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_read_pmds);

/*
 * Only call this function when a process it trying to
 * write the debug registers (reading is always allowed)
 */
int
pfm_use_debug_registers(struct task_struct *task)
{
    pfm_context_t *ctx = task->thread.pfm_context;
    unsigned long flags;
    int ret = 0;

    if (pmu_conf->use_rr_dbregs == 0) return 0;

    DPRINT(("called for [%d]\n", task_pid_nr(task)));

    /*
     * do it only once
     */
    if (task->thread.flags & IA64_THREAD_DBG_VALID) return 0;

    /*
     * Even on SMP, we do not need to use an atomic here because
     * the only way in is via ptrace() and this is possible only when the
     * process is stopped. Even in the case where the ctxsw out is not totally
     * completed by the time we come here, there is no way the 'stopped' process
     * could be in the middle of fiddling with the pfm_write_ibr_dbr() routine.
     * So this is always safe.
     */
    if (ctx && ctx->ctx_fl_using_dbreg == 1) return -1;

    LOCK_PFS(flags);

    /*
     * We cannot allow setting breakpoints when system wide monitoring
     * sessions are using the debug registers.
     */
    if (pfm_sessions.pfs_sys_use_dbregs> 0)
        ret = -1;
    else
        pfm_sessions.pfs_ptrace_use_dbregs++;

    DPRINT(("ptrace_use_dbregs=%u  sys_use_dbregs=%u by [%d] ret = %d\n",
          pfm_sessions.pfs_ptrace_use_dbregs,
          pfm_sessions.pfs_sys_use_dbregs,
          task_pid_nr(task), ret));

    UNLOCK_PFS(flags);

    return ret;
}

/*
 * This function is called for every task that exits with the
 * IA64_THREAD_DBG_VALID set. This indicates a task which was
 * able to use the debug registers for debugging purposes via
 * ptrace(). Therefore we know it was not using them for
 * performance monitoring, so we only decrement the number
 * of "ptraced" debug register users to keep the count up to date
 */
int
pfm_release_debug_registers(struct task_struct *task)
{
    unsigned long flags;
    int ret;

    if (pmu_conf->use_rr_dbregs == 0) return 0;

    LOCK_PFS(flags);
    if (pfm_sessions.pfs_ptrace_use_dbregs == 0) {
        printk(KERN_ERR "perfmon: invalid release for [%d] ptrace_use_dbregs=0\n", task_pid_nr(task));
        ret = -1;
    }  else {
        pfm_sessions.pfs_ptrace_use_dbregs--;
        ret = 0;
    }
    UNLOCK_PFS(flags);

    return ret;
}

static int
pfm_restart(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task;
    pfm_buffer_fmt_t *fmt;
    pfm_ovfl_ctrl_t rst_ctrl;
    int state, is_system;
    int ret = 0;

    state     = ctx->ctx_state;
    fmt       = ctx->ctx_buf_fmt;
    is_system = ctx->ctx_fl_system;
    task      = PFM_CTX_TASK(ctx);

    switch(state) {
        case PFM_CTX_MASKED:
            break;
        case PFM_CTX_LOADED: 
            if (CTX_HAS_SMPL(ctx) && fmt->fmt_restart_active) break;
            /* fall through */
        case PFM_CTX_UNLOADED:
        case PFM_CTX_ZOMBIE:
            DPRINT(("invalid state=%d\n", state));
            return -EBUSY;
        default:
            DPRINT(("state=%d, cannot operate (no active_restart handler)\n", state));
            return -EINVAL;
    }

    /*
     * In system wide and when the context is loaded, access can only happen
     * when the caller is running on the CPU being monitored by the session.
     * It does not have to be the owner (ctx_task) of the context per se.
     */
    if (is_system && ctx->ctx_cpu != smp_processor_id()) {
        DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
        return -EBUSY;
    }

    /* sanity check */
    if (unlikely(task == NULL)) {
        printk(KERN_ERR "perfmon: [%d] pfm_restart no task\n", task_pid_nr(current));
        return -EINVAL;
    }

    if (task == current || is_system) {

        fmt = ctx->ctx_buf_fmt;

        DPRINT(("restarting self %d ovfl=0x%lx\n",
            task_pid_nr(task),
            ctx->ctx_ovfl_regs[0]));

        if (CTX_HAS_SMPL(ctx)) {

            prefetch(ctx->ctx_smpl_hdr);

            rst_ctrl.bits.mask_monitoring = 0;
            rst_ctrl.bits.reset_ovfl_pmds = 0;

            if (state == PFM_CTX_LOADED)
                ret = pfm_buf_fmt_restart_active(fmt, task, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
            else
                ret = pfm_buf_fmt_restart(fmt, task, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
        } else {
            rst_ctrl.bits.mask_monitoring = 0;
            rst_ctrl.bits.reset_ovfl_pmds = 1;
        }

        if (ret == 0) {
            if (rst_ctrl.bits.reset_ovfl_pmds)
                pfm_reset_regs(ctx, ctx->ctx_ovfl_regs, PFM_PMD_LONG_RESET);

            if (rst_ctrl.bits.mask_monitoring == 0) {
                DPRINT(("resuming monitoring for [%d]\n", task_pid_nr(task)));

                if (state == PFM_CTX_MASKED) pfm_restore_monitoring(task);
            } else {
                DPRINT(("keeping monitoring stopped for [%d]\n", task_pid_nr(task)));

                // cannot use pfm_stop_monitoring(task, regs);
            }
        }
        /*
         * clear overflowed PMD mask to remove any stale information
         */
        ctx->ctx_ovfl_regs[0] = 0UL;

        /*
         * back to LOADED state
         */
        ctx->ctx_state = PFM_CTX_LOADED;

        /*
         * XXX: not really useful for self monitoring
         */
        ctx->ctx_fl_can_restart = 0;

        return 0;
    }

    /* 
     * restart another task
     */

    /*
     * When PFM_CTX_MASKED, we cannot issue a restart before the previous 
     * one is seen by the task.
     */
    if (state == PFM_CTX_MASKED) {
        if (ctx->ctx_fl_can_restart == 0) return -EINVAL;
        /*
         * will prevent subsequent restart before this one is
         * seen by other task
         */
        ctx->ctx_fl_can_restart = 0;
    }

    /*
     * if blocking, then post the semaphore is PFM_CTX_MASKED, i.e.
     * the task is blocked or on its way to block. That's the normal
     * restart path. If the monitoring is not masked, then the task
     * can be actively monitoring and we cannot directly intervene.
     * Therefore we use the trap mechanism to catch the task and
     * force it to reset the buffer/reset PMDs.
     *
     * if non-blocking, then we ensure that the task will go into
     * pfm_handle_work() before returning to user mode.
     *
     * We cannot explicitly reset another task, it MUST always
     * be done by the task itself. This works for system wide because
     * the tool that is controlling the session is logically doing 
     * "self-monitoring".
     */
    if (CTX_OVFL_NOBLOCK(ctx) == 0 && state == PFM_CTX_MASKED) {
        DPRINT(("unblocking [%d]\n", task_pid_nr(task)));
        complete(&ctx->ctx_restart_done);
    } else {
        DPRINT(("[%d] armed exit trap\n", task_pid_nr(task)));

        ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_RESET;

        PFM_SET_WORK_PENDING(task, 1);

        set_notify_resume(task);

        /*
         * XXX: send reschedule if task runs on another CPU
         */
    }
    return 0;
}

static int
pfm_debug(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    unsigned int m = *(unsigned int *)arg;

    pfm_sysctl.debug = m == 0 ? 0 : 1;

    printk(KERN_INFO "perfmon debugging %s (timing reset)\n", pfm_sysctl.debug ? "on" : "off");

    if (m == 0) {
        memset(pfm_stats, 0, sizeof(pfm_stats));
        for(m=0; m < NR_CPUS; m++) pfm_stats[m].pfm_ovfl_intr_cycles_min = ~0UL;
    }
    return 0;
}

/*
 * arg can be NULL and count can be zero for this function
 */
static int
pfm_write_ibr_dbr(int mode, pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct thread_struct *thread = NULL;
    struct task_struct *task;
    pfarg_dbreg_t *req = (pfarg_dbreg_t *)arg;
    unsigned long flags;
    dbreg_t dbreg;
    unsigned int rnum;
    int first_time;
    int ret = 0, state;
    int i, can_access_pmu = 0;
    int is_system, is_loaded;

    if (pmu_conf->use_rr_dbregs == 0) return -EINVAL;

    state     = ctx->ctx_state;
    is_loaded = state == PFM_CTX_LOADED ? 1 : 0;
    is_system = ctx->ctx_fl_system;
    task      = ctx->ctx_task;

    if (state == PFM_CTX_ZOMBIE) return -EINVAL;

    /*
     * on both UP and SMP, we can only write to the PMC when the task is
     * the owner of the local PMU.
     */
    if (is_loaded) {
        thread = &task->thread;
        /*
         * In system wide and when the context is loaded, access can only happen
         * when the caller is running on the CPU being monitored by the session.
         * It does not have to be the owner (ctx_task) of the context per se.
         */
        if (unlikely(is_system && ctx->ctx_cpu != smp_processor_id())) {
            DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
            return -EBUSY;
        }
        can_access_pmu = GET_PMU_OWNER() == task || is_system ? 1 : 0;
    }

    /*
     * we do not need to check for ipsr.db because we do clear ibr.x, dbr.r, and dbr.w
     * ensuring that no real breakpoint can be installed via this call.
     *
     * IMPORTANT: regs can be NULL in this function
     */

    first_time = ctx->ctx_fl_using_dbreg == 0;

    /*
     * don't bother if we are loaded and task is being debugged
     */
    if (is_loaded && (thread->flags & IA64_THREAD_DBG_VALID) != 0) {
        DPRINT(("debug registers already in use for [%d]\n", task_pid_nr(task)));
        return -EBUSY;
    }

    /*
     * check for debug registers in system wide mode
     *
     * If though a check is done in pfm_context_load(),
     * we must repeat it here, in case the registers are
     * written after the context is loaded
     */
    if (is_loaded) {
        LOCK_PFS(flags);

        if (first_time && is_system) {
            if (pfm_sessions.pfs_ptrace_use_dbregs)
                ret = -EBUSY;
            else
                pfm_sessions.pfs_sys_use_dbregs++;
        }
        UNLOCK_PFS(flags);
    }

    if (ret != 0) return ret;

    /*
     * mark ourself as user of the debug registers for
     * perfmon purposes.
     */
    ctx->ctx_fl_using_dbreg = 1;

    /*
     * clear hardware registers to make sure we don't
     * pick up stale state.
     *
     * for a system wide session, we do not use
     * thread.dbr, thread.ibr because this process
     * never leaves the current CPU and the state
     * is shared by all processes running on it
     */
    if (first_time && can_access_pmu) {
        DPRINT(("[%d] clearing ibrs, dbrs\n", task_pid_nr(task)));
        for (i=0; i < pmu_conf->num_ibrs; i++) {
            ia64_set_ibr(i, 0UL);
            ia64_dv_serialize_instruction();
        }
        ia64_srlz_i();
        for (i=0; i < pmu_conf->num_dbrs; i++) {
            ia64_set_dbr(i, 0UL);
            ia64_dv_serialize_data();
        }
        ia64_srlz_d();
    }

    /*
     * Now install the values into the registers
     */
    for (i = 0; i < count; i++, req++) {

        rnum      = req->dbreg_num;
        dbreg.val = req->dbreg_value;

        ret = -EINVAL;

        if ((mode == PFM_CODE_RR && rnum >= PFM_NUM_IBRS) || ((mode == PFM_DATA_RR) && rnum >= PFM_NUM_DBRS)) {
            DPRINT(("invalid register %u val=0x%lx mode=%d i=%d count=%d\n",
                  rnum, dbreg.val, mode, i, count));

            goto abort_mission;
        }

        /*
         * make sure we do not install enabled breakpoint
         */
        if (rnum & 0x1) {
            if (mode == PFM_CODE_RR)
                dbreg.ibr.ibr_x = 0;
            else
                dbreg.dbr.dbr_r = dbreg.dbr.dbr_w = 0;
        }

        PFM_REG_RETFLAG_SET(req->dbreg_flags, 0);

        /*
         * Debug registers, just like PMC, can only be modified
         * by a kernel call. Moreover, perfmon() access to those
         * registers are centralized in this routine. The hardware
         * does not modify the value of these registers, therefore,
         * if we save them as they are written, we can avoid having
         * to save them on context switch out. This is made possible
         * by the fact that when perfmon uses debug registers, ptrace()
         * won't be able to modify them concurrently.
         */
        if (mode == PFM_CODE_RR) {
            CTX_USED_IBR(ctx, rnum);

            if (can_access_pmu) {
                ia64_set_ibr(rnum, dbreg.val);
                ia64_dv_serialize_instruction();
            }

            ctx->ctx_ibrs[rnum] = dbreg.val;

            DPRINT(("write ibr%u=0x%lx used_ibrs=0x%x ld=%d apmu=%d\n",
                rnum, dbreg.val, ctx->ctx_used_ibrs[0], is_loaded, can_access_pmu));
        } else {
            CTX_USED_DBR(ctx, rnum);

            if (can_access_pmu) {
                ia64_set_dbr(rnum, dbreg.val);
                ia64_dv_serialize_data();
            }
            ctx->ctx_dbrs[rnum] = dbreg.val;

            DPRINT(("write dbr%u=0x%lx used_dbrs=0x%x ld=%d apmu=%d\n",
                rnum, dbreg.val, ctx->ctx_used_dbrs[0], is_loaded, can_access_pmu));
        }
    }

    return 0;

abort_mission:
    /*
     * in case it was our first attempt, we undo the global modifications
     */
    if (first_time) {
        LOCK_PFS(flags);
        if (ctx->ctx_fl_system) {
            pfm_sessions.pfs_sys_use_dbregs--;
        }
        UNLOCK_PFS(flags);
        ctx->ctx_fl_using_dbreg = 0;
    }
    /*
     * install error return flag
     */
    PFM_REG_RETFLAG_SET(req->dbreg_flags, PFM_REG_RETFL_EINVAL);

    return ret;
}

static int
pfm_write_ibrs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    return pfm_write_ibr_dbr(PFM_CODE_RR, ctx, arg, count, regs);
}

static int
pfm_write_dbrs(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    return pfm_write_ibr_dbr(PFM_DATA_RR, ctx, arg, count, regs);
}

int
pfm_mod_write_ibrs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
    pfm_context_t *ctx;

    if (req == NULL) return -EINVAL;

    ctx = GET_PMU_CTX();

    if (ctx == NULL) return -EINVAL;

    /*
     * for now limit to current task, which is enough when calling
     * from overflow handler
     */
    if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

    return pfm_write_ibrs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_ibrs);

int
pfm_mod_write_dbrs(struct task_struct *task, void *req, unsigned int nreq, struct pt_regs *regs)
{
    pfm_context_t *ctx;

    if (req == NULL) return -EINVAL;

    ctx = GET_PMU_CTX();

    if (ctx == NULL) return -EINVAL;

    /*
     * for now limit to current task, which is enough when calling
     * from overflow handler
     */
    if (task != current && ctx->ctx_fl_system == 0) return -EBUSY;

    return pfm_write_dbrs(ctx, req, nreq, regs);
}
EXPORT_SYMBOL(pfm_mod_write_dbrs);


static int
pfm_get_features(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    pfarg_features_t *req = (pfarg_features_t *)arg;

    req->ft_version = PFM_VERSION;
    return 0;
}

static int
pfm_stop(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct pt_regs *tregs;
    struct task_struct *task = PFM_CTX_TASK(ctx);
    int state, is_system;

    state     = ctx->ctx_state;
    is_system = ctx->ctx_fl_system;

    /*
     * context must be attached to issue the stop command (includes LOADED,MASKED,ZOMBIE)
     */
    if (state == PFM_CTX_UNLOADED) return -EINVAL;

    /*
     * In system wide and when the context is loaded, access can only happen
     * when the caller is running on the CPU being monitored by the session.
     * It does not have to be the owner (ctx_task) of the context per se.
     */
    if (is_system && ctx->ctx_cpu != smp_processor_id()) {
        DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
        return -EBUSY;
    }
    DPRINT(("task [%d] ctx_state=%d is_system=%d\n",
        task_pid_nr(PFM_CTX_TASK(ctx)),
        state,
        is_system));
    /*
     * in system mode, we need to update the PMU directly
     * and the user level state of the caller, which may not
     * necessarily be the creator of the context.
     */
    if (is_system) {
        /*
         * Update local PMU first
         *
         * disable dcr pp
         */
        ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) & ~IA64_DCR_PP);
        ia64_srlz_i();

        /*
         * update local cpuinfo
         */
        PFM_CPUINFO_CLEAR(PFM_CPUINFO_DCR_PP);

        /*
         * stop monitoring, does srlz.i
         */
        pfm_clear_psr_pp();

        /*
         * stop monitoring in the caller
         */
        ia64_psr(regs)->pp = 0;

        return 0;
    }
    /*
     * per-task mode
     */

    if (task == current) {
        /* stop monitoring  at kernel level */
        pfm_clear_psr_up();

        /*
         * stop monitoring at the user level
         */
        ia64_psr(regs)->up = 0;
    } else {
        tregs = task_pt_regs(task);

        /*
         * stop monitoring at the user level
         */
        ia64_psr(tregs)->up = 0;

        /*
         * monitoring disabled in kernel at next reschedule
         */
        ctx->ctx_saved_psr_up = 0;
        DPRINT(("task=[%d]\n", task_pid_nr(task)));
    }
    return 0;
}


static int
pfm_start(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct pt_regs *tregs;
    int state, is_system;

    state     = ctx->ctx_state;
    is_system = ctx->ctx_fl_system;

    if (state != PFM_CTX_LOADED) return -EINVAL;

    /*
     * In system wide and when the context is loaded, access can only happen
     * when the caller is running on the CPU being monitored by the session.
     * It does not have to be the owner (ctx_task) of the context per se.
     */
    if (is_system && ctx->ctx_cpu != smp_processor_id()) {
        DPRINT(("should be running on CPU%d\n", ctx->ctx_cpu));
        return -EBUSY;
    }

    /*
     * in system mode, we need to update the PMU directly
     * and the user level state of the caller, which may not
     * necessarily be the creator of the context.
     */
    if (is_system) {

        /*
         * set user level psr.pp for the caller
         */
        ia64_psr(regs)->pp = 1;

        /*
         * now update the local PMU and cpuinfo
         */
        PFM_CPUINFO_SET(PFM_CPUINFO_DCR_PP);

        /*
         * start monitoring at kernel level
         */
        pfm_set_psr_pp();

        /* enable dcr pp */
        ia64_setreg(_IA64_REG_CR_DCR, ia64_getreg(_IA64_REG_CR_DCR) | IA64_DCR_PP);
        ia64_srlz_i();

        return 0;
    }

    /*
     * per-process mode
     */

    if (ctx->ctx_task == current) {

        /* start monitoring at kernel level */
        pfm_set_psr_up();

        /*
         * activate monitoring at user level
         */
        ia64_psr(regs)->up = 1;

    } else {
        tregs = task_pt_regs(ctx->ctx_task);

        /*
         * start monitoring at the kernel level the next
         * time the task is scheduled
         */
        ctx->ctx_saved_psr_up = IA64_PSR_UP;

        /*
         * activate monitoring at user level
         */
        ia64_psr(tregs)->up = 1;
    }
    return 0;
}

static int
pfm_get_pmc_reset(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    pfarg_reg_t *req = (pfarg_reg_t *)arg;
    unsigned int cnum;
    int i;
    int ret = -EINVAL;

    for (i = 0; i < count; i++, req++) {

        cnum = req->reg_num;

        if (!PMC_IS_IMPL(cnum)) goto abort_mission;

        req->reg_value = PMC_DFL_VAL(cnum);

        PFM_REG_RETFLAG_SET(req->reg_flags, 0);

        DPRINT(("pmc_reset_val pmc[%u]=0x%lx\n", cnum, req->reg_value));
    }
    return 0;

abort_mission:
    PFM_REG_RETFLAG_SET(req->reg_flags, PFM_REG_RETFL_EINVAL);
    return ret;
}

static int
pfm_check_task_exist(pfm_context_t *ctx)
{
    struct task_struct *g, *t;
    int ret = -ESRCH;

    read_lock(&tasklist_lock);

    do_each_thread (g, t) {
        if (t->thread.pfm_context == ctx) {
            ret = 0;
            goto out;
        }
    } while_each_thread (g, t);
out:
    read_unlock(&tasklist_lock);

    DPRINT(("pfm_check_task_exist: ret=%d ctx=%p\n", ret, ctx));

    return ret;
}

static int
pfm_context_load(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task;
    struct thread_struct *thread;
    struct pfm_context_t *old;
    unsigned long flags;
#ifndef CONFIG_SMP
    struct task_struct *owner_task = NULL;
#endif
    pfarg_load_t *req = (pfarg_load_t *)arg;
    unsigned long *pmcs_source, *pmds_source;
    int the_cpu;
    int ret = 0;
    int state, is_system, set_dbregs = 0;

    state     = ctx->ctx_state;
    is_system = ctx->ctx_fl_system;
    /*
     * can only load from unloaded or terminated state
     */
    if (state != PFM_CTX_UNLOADED) {
        DPRINT(("cannot load to [%d], invalid ctx_state=%d\n",
            req->load_pid,
            ctx->ctx_state));
        return -EBUSY;
    }

    DPRINT(("load_pid [%d] using_dbreg=%d\n", req->load_pid, ctx->ctx_fl_using_dbreg));

    if (CTX_OVFL_NOBLOCK(ctx) == 0 && req->load_pid == current->pid) {
        DPRINT(("cannot use blocking mode on self\n"));
        return -EINVAL;
    }

    ret = pfm_get_task(ctx, req->load_pid, &task);
    if (ret) {
        DPRINT(("load_pid [%d] get_task=%d\n", req->load_pid, ret));
        return ret;
    }

    ret = -EINVAL;

    /*
     * system wide is self monitoring only
     */
    if (is_system && task != current) {
        DPRINT(("system wide is self monitoring only load_pid=%d\n",
            req->load_pid));
        goto error;
    }

    thread = &task->thread;

    ret = 0;
    /*
     * cannot load a context which is using range restrictions,
     * into a task that is being debugged.
     */
    if (ctx->ctx_fl_using_dbreg) {
        if (thread->flags & IA64_THREAD_DBG_VALID) {
            ret = -EBUSY;
            DPRINT(("load_pid [%d] task is debugged, cannot load range restrictions\n", req->load_pid));
            goto error;
        }
        LOCK_PFS(flags);

        if (is_system) {
            if (pfm_sessions.pfs_ptrace_use_dbregs) {
                DPRINT(("cannot load [%d] dbregs in use\n",
                            task_pid_nr(task)));
                ret = -EBUSY;
            } else {
                pfm_sessions.pfs_sys_use_dbregs++;
                DPRINT(("load [%d] increased sys_use_dbreg=%u\n", task_pid_nr(task), pfm_sessions.pfs_sys_use_dbregs));
                set_dbregs = 1;
            }
        }

        UNLOCK_PFS(flags);

        if (ret) goto error;
    }

    /*
     * SMP system-wide monitoring implies self-monitoring.
     *
     * The programming model expects the task to
     * be pinned on a CPU throughout the session.
     * Here we take note of the current CPU at the
     * time the context is loaded. No call from
     * another CPU will be allowed.
     *
     * The pinning via shed_setaffinity()
     * must be done by the calling task prior
     * to this call.
     *
     * systemwide: keep track of CPU this session is supposed to run on
     */
    the_cpu = ctx->ctx_cpu = smp_processor_id();

    ret = -EBUSY;
    /*
     * now reserve the session
     */
    ret = pfm_reserve_session(current, is_system, the_cpu);
    if (ret) goto error;

    /*
     * task is necessarily stopped at this point.
     *
     * If the previous context was zombie, then it got removed in
     * pfm_save_regs(). Therefore we should not see it here.
     * If we see a context, then this is an active context
     *
     * XXX: needs to be atomic
     */
    DPRINT(("before cmpxchg() old_ctx=%p new_ctx=%p\n",
        thread->pfm_context, ctx));

    ret = -EBUSY;
    old = ia64_cmpxchg(acq, &thread->pfm_context, NULL, ctx, sizeof(pfm_context_t *));
    if (old != NULL) {
        DPRINT(("load_pid [%d] already has a context\n", req->load_pid));
        goto error_unres;
    }

    pfm_reset_msgq(ctx);

    ctx->ctx_state = PFM_CTX_LOADED;

    /*
     * link context to task
     */
    ctx->ctx_task = task;

    if (is_system) {
        /*
         * we load as stopped
         */
        PFM_CPUINFO_SET(PFM_CPUINFO_SYST_WIDE);
        PFM_CPUINFO_CLEAR(PFM_CPUINFO_DCR_PP);

        if (ctx->ctx_fl_excl_idle) PFM_CPUINFO_SET(PFM_CPUINFO_EXCL_IDLE);
    } else {
        thread->flags |= IA64_THREAD_PM_VALID;
    }

    /*
     * propagate into thread-state
     */
    pfm_copy_pmds(task, ctx);
    pfm_copy_pmcs(task, ctx);

    pmcs_source = ctx->th_pmcs;
    pmds_source = ctx->th_pmds;

    /*
     * always the case for system-wide
     */
    if (task == current) {

        if (is_system == 0) {

            /* allow user level control */
            ia64_psr(regs)->sp = 0;
            DPRINT(("clearing psr.sp for [%d]\n", task_pid_nr(task)));

            SET_LAST_CPU(ctx, smp_processor_id());
            INC_ACTIVATION();
            SET_ACTIVATION(ctx);
#ifndef CONFIG_SMP
            /*
             * push the other task out, if any
             */
            owner_task = GET_PMU_OWNER();
            if (owner_task) pfm_lazy_save_regs(owner_task);
#endif
        }
        /*
         * load all PMD from ctx to PMU (as opposed to thread state)
         * restore all PMC from ctx to PMU
         */
        pfm_restore_pmds(pmds_source, ctx->ctx_all_pmds[0]);
        pfm_restore_pmcs(pmcs_source, ctx->ctx_all_pmcs[0]);

        ctx->ctx_reload_pmcs[0] = 0UL;
        ctx->ctx_reload_pmds[0] = 0UL;

        /*
         * guaranteed safe by earlier check against DBG_VALID
         */
        if (ctx->ctx_fl_using_dbreg) {
            pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
            pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
        }
        /*
         * set new ownership
         */
        SET_PMU_OWNER(task, ctx);

        DPRINT(("context loaded on PMU for [%d]\n", task_pid_nr(task)));
    } else {
        /*
         * when not current, task MUST be stopped, so this is safe
         */
        regs = task_pt_regs(task);

        /* force a full reload */
        ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
        SET_LAST_CPU(ctx, -1);

        /* initial saved psr (stopped) */
        ctx->ctx_saved_psr_up = 0UL;
        ia64_psr(regs)->up = ia64_psr(regs)->pp = 0;
    }

    ret = 0;

error_unres:
    if (ret) pfm_unreserve_session(ctx, ctx->ctx_fl_system, the_cpu);
error:
    /*
     * we must undo the dbregs setting (for system-wide)
     */
    if (ret && set_dbregs) {
        LOCK_PFS(flags);
        pfm_sessions.pfs_sys_use_dbregs--;
        UNLOCK_PFS(flags);
    }
    /*
     * release task, there is now a link with the context
     */
    if (is_system == 0 && task != current) {
        pfm_put_task(task);

        if (ret == 0) {
            ret = pfm_check_task_exist(ctx);
            if (ret) {
                ctx->ctx_state = PFM_CTX_UNLOADED;
                ctx->ctx_task  = NULL;
            }
        }
    }
    return ret;
}

/*
 * in this function, we do not need to increase the use count
 * for the task via get_task_struct(), because we hold the
 * context lock. If the task were to disappear while having
 * a context attached, it would go through pfm_exit_thread()
 * which also grabs the context lock  and would therefore be blocked
 * until we are here.
 */
static void pfm_flush_pmds(struct task_struct *, pfm_context_t *ctx);

static int
pfm_context_unload(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs)
{
    struct task_struct *task = PFM_CTX_TASK(ctx);
    struct pt_regs *tregs;
    int prev_state, is_system;
    int ret;

    DPRINT(("ctx_state=%d task [%d]\n", ctx->ctx_state, task ? task_pid_nr(task) : -1));

    prev_state = ctx->ctx_state;
    is_system  = ctx->ctx_fl_system;

    /*
     * unload only when necessary
     */
    if (prev_state == PFM_CTX_UNLOADED) {
        DPRINT(("ctx_state=%d, nothing to do\n", prev_state));
        return 0;
    }

    /*
     * clear psr and dcr bits
     */
    ret = pfm_stop(ctx, NULL, 0, regs);
    if (ret) return ret;

    ctx->ctx_state = PFM_CTX_UNLOADED;

    /*
     * in system mode, we need to update the PMU directly
     * and the user level state of the caller, which may not
     * necessarily be the creator of the context.
     */
    if (is_system) {

        /*
         * Update cpuinfo
         *
         * local PMU is taken care of in pfm_stop()
         */
        PFM_CPUINFO_CLEAR(PFM_CPUINFO_SYST_WIDE);
        PFM_CPUINFO_CLEAR(PFM_CPUINFO_EXCL_IDLE);

        /*
         * save PMDs in context
         * release ownership
         */
        pfm_flush_pmds(current, ctx);

        /*
         * at this point we are done with the PMU
         * so we can unreserve the resource.
         */
        if (prev_state != PFM_CTX_ZOMBIE) 
            pfm_unreserve_session(ctx, 1 , ctx->ctx_cpu);

        /*
         * disconnect context from task
         */
        task->thread.pfm_context = NULL;
        /*
         * disconnect task from context
         */
        ctx->ctx_task = NULL;

        /*
         * There is nothing more to cleanup here.
         */
        return 0;
    }

    /*
     * per-task mode
     */
    tregs = task == current ? regs : task_pt_regs(task);

    if (task == current) {
        /*
         * cancel user level control
         */
        ia64_psr(regs)->sp = 1;

        DPRINT(("setting psr.sp for [%d]\n", task_pid_nr(task)));
    }
    /*
     * save PMDs to context
     * release ownership
     */
    pfm_flush_pmds(task, ctx);

    /*
     * at this point we are done with the PMU
     * so we can unreserve the resource.
     *
     * when state was ZOMBIE, we have already unreserved.
     */
    if (prev_state != PFM_CTX_ZOMBIE) 
        pfm_unreserve_session(ctx, 0 , ctx->ctx_cpu);

    /*
     * reset activation counter and psr
     */
    ctx->ctx_last_activation = PFM_INVALID_ACTIVATION;
    SET_LAST_CPU(ctx, -1);

    /*
     * PMU state will not be restored
     */
    task->thread.flags &= ~IA64_THREAD_PM_VALID;

    /*
     * break links between context and task
     */
    task->thread.pfm_context  = NULL;
    ctx->ctx_task             = NULL;

    PFM_SET_WORK_PENDING(task, 0);

    ctx->ctx_fl_trap_reason  = PFM_TRAP_REASON_NONE;
    ctx->ctx_fl_can_restart  = 0;
    ctx->ctx_fl_going_zombie = 0;

    DPRINT(("disconnected [%d] from context\n", task_pid_nr(task)));

    return 0;
}


/*
 * called only from exit_thread(): task == current
 * we come here only if current has a context attached (loaded or masked)
 */
void
pfm_exit_thread(struct task_struct *task)
{
    pfm_context_t *ctx;
    unsigned long flags;
    struct pt_regs *regs = task_pt_regs(task);
    int ret, state;
    int free_ok = 0;

    ctx = PFM_GET_CTX(task);

    PROTECT_CTX(ctx, flags);

    DPRINT(("state=%d task [%d]\n", ctx->ctx_state, task_pid_nr(task)));

    state = ctx->ctx_state;
    switch(state) {
        case PFM_CTX_UNLOADED:
            /*
             * only comes to this function if pfm_context is not NULL, i.e., cannot
             * be in unloaded state
             */
            printk(KERN_ERR "perfmon: pfm_exit_thread [%d] ctx unloaded\n", task_pid_nr(task));
            break;
        case PFM_CTX_LOADED:
        case PFM_CTX_MASKED:
            ret = pfm_context_unload(ctx, NULL, 0, regs);
            if (ret) {
                printk(KERN_ERR "perfmon: pfm_exit_thread [%d] state=%d unload failed %d\n", task_pid_nr(task), state, ret);
            }
            DPRINT(("ctx unloaded for current state was %d\n", state));

            pfm_end_notify_user(ctx);
            break;
        case PFM_CTX_ZOMBIE:
            ret = pfm_context_unload(ctx, NULL, 0, regs);
            if (ret) {
                printk(KERN_ERR "perfmon: pfm_exit_thread [%d] state=%d unload failed %d\n", task_pid_nr(task), state, ret);
            }
            free_ok = 1;
            break;
        default:
            printk(KERN_ERR "perfmon: pfm_exit_thread [%d] unexpected state=%d\n", task_pid_nr(task), state);
            break;
    }
    UNPROTECT_CTX(ctx, flags);

    { u64 psr = pfm_get_psr();
      BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
      BUG_ON(GET_PMU_OWNER());
      BUG_ON(ia64_psr(regs)->up);
      BUG_ON(ia64_psr(regs)->pp);
    }

    /*
     * All memory free operations (especially for vmalloc'ed memory)
     * MUST be done with interrupts ENABLED.
     */
    if (free_ok) pfm_context_free(ctx);
}

/*
 * functions MUST be listed in the increasing order of their index (see permfon.h)
 */
#define PFM_CMD(name, flags, arg_count, arg_type, getsz) { name, #name, flags, arg_count, sizeof(arg_type), getsz }
#define PFM_CMD_S(name, flags) { name, #name, flags, 0, 0, NULL }
#define PFM_CMD_PCLRWS  (PFM_CMD_FD|PFM_CMD_ARG_RW|PFM_CMD_STOP)
#define PFM_CMD_PCLRW   (PFM_CMD_FD|PFM_CMD_ARG_RW)
#define PFM_CMD_NONE    { NULL, "no-cmd", 0, 0, 0, NULL}

static pfm_cmd_desc_t pfm_cmd_tab[]={
/* 0  */PFM_CMD_NONE,
/* 1  */PFM_CMD(pfm_write_pmcs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 2  */PFM_CMD(pfm_write_pmds, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 3  */PFM_CMD(pfm_read_pmds, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 4  */PFM_CMD_S(pfm_stop, PFM_CMD_PCLRWS),
/* 5  */PFM_CMD_S(pfm_start, PFM_CMD_PCLRWS),
/* 6  */PFM_CMD_NONE,
/* 7  */PFM_CMD_NONE,
/* 8  */PFM_CMD(pfm_context_create, PFM_CMD_ARG_RW, 1, pfarg_context_t, pfm_ctx_getsize),
/* 9  */PFM_CMD_NONE,
/* 10 */PFM_CMD_S(pfm_restart, PFM_CMD_PCLRW),
/* 11 */PFM_CMD_NONE,
/* 12 */PFM_CMD(pfm_get_features, PFM_CMD_ARG_RW, 1, pfarg_features_t, NULL),
/* 13 */PFM_CMD(pfm_debug, 0, 1, unsigned int, NULL),
/* 14 */PFM_CMD_NONE,
/* 15 */PFM_CMD(pfm_get_pmc_reset, PFM_CMD_ARG_RW, PFM_CMD_ARG_MANY, pfarg_reg_t, NULL),
/* 16 */PFM_CMD(pfm_context_load, PFM_CMD_PCLRWS, 1, pfarg_load_t, NULL),
/* 17 */PFM_CMD_S(pfm_context_unload, PFM_CMD_PCLRWS),
/* 18 */PFM_CMD_NONE,
/* 19 */PFM_CMD_NONE,
/* 20 */PFM_CMD_NONE,
/* 21 */PFM_CMD_NONE,
/* 22 */PFM_CMD_NONE,
/* 23 */PFM_CMD_NONE,
/* 24 */PFM_CMD_NONE,
/* 25 */PFM_CMD_NONE,
/* 26 */PFM_CMD_NONE,
/* 27 */PFM_CMD_NONE,
/* 28 */PFM_CMD_NONE,
/* 29 */PFM_CMD_NONE,
/* 30 */PFM_CMD_NONE,
/* 31 */PFM_CMD_NONE,
/* 32 */PFM_CMD(pfm_write_ibrs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_dbreg_t, NULL),
/* 33 */PFM_CMD(pfm_write_dbrs, PFM_CMD_PCLRWS, PFM_CMD_ARG_MANY, pfarg_dbreg_t, NULL)
};
#define PFM_CMD_COUNT   (sizeof(pfm_cmd_tab)/sizeof(pfm_cmd_desc_t))

static int
pfm_check_task_state(pfm_context_t *ctx, int cmd, unsigned long flags)
{
    struct task_struct *task;
    int state, old_state;

recheck:
    state = ctx->ctx_state;
    task  = ctx->ctx_task;

    if (task == NULL) {
        DPRINT(("context %d no task, state=%d\n", ctx->ctx_fd, state));
        return 0;
    }

    DPRINT(("context %d state=%d [%d] task_state=%ld must_stop=%d\n",
        ctx->ctx_fd,
        state,
        task_pid_nr(task),
        task->state, PFM_CMD_STOPPED(cmd)));

    /*
     * self-monitoring always ok.
     *
     * for system-wide the caller can either be the creator of the
     * context (to one to which the context is attached to) OR
     * a task running on the same CPU as the session.
     */
    if (task == current || ctx->ctx_fl_system) return 0;

    /*
     * we are monitoring another thread
     */
    switch(state) {
        case PFM_CTX_UNLOADED:
            /*
             * if context is UNLOADED we are safe to go
             */
            return 0;
        case PFM_CTX_ZOMBIE:
            /*
             * no command can operate on a zombie context
             */
            DPRINT(("cmd %d state zombie cannot operate on context\n", cmd));
            return -EINVAL;
        case PFM_CTX_MASKED:
            /*
             * PMU state has been saved to software even though
             * the thread may still be running.
             */
            if (cmd != PFM_UNLOAD_CONTEXT) return 0;
    }

    /*
     * context is LOADED or MASKED. Some commands may need to have 
     * the task stopped.
     *
     * We could lift this restriction for UP but it would mean that
     * the user has no guarantee the task would not run between
     * two successive calls to perfmonctl(). That's probably OK.
     * If this user wants to ensure the task does not run, then
     * the task must be stopped.
     */
    if (PFM_CMD_STOPPED(cmd)) {
        if (!task_is_stopped_or_traced(task)) {
            DPRINT(("[%d] task not in stopped state\n", task_pid_nr(task)));
            return -EBUSY;
        }
        /*
         * task is now stopped, wait for ctxsw out
         *
         * This is an interesting point in the code.
         * We need to unprotect the context because
         * the pfm_save_regs() routines needs to grab
         * the same lock. There are danger in doing
         * this because it leaves a window open for
         * another task to get access to the context
         * and possibly change its state. The one thing
         * that is not possible is for the context to disappear
         * because we are protected by the VFS layer, i.e.,
         * get_fd()/put_fd().
         */
        old_state = state;

        UNPROTECT_CTX(ctx, flags);

        wait_task_inactive(task, 0);

        PROTECT_CTX(ctx, flags);

        /*
         * we must recheck to verify if state has changed
         */
        if (ctx->ctx_state != old_state) {
            DPRINT(("old_state=%d new_state=%d\n", old_state, ctx->ctx_state));
            goto recheck;
        }
    }
    return 0;
}

/*
 * system-call entry point (must return long)
 */
asmlinkage long
sys_perfmonctl (int fd, int cmd, void __user *arg, int count)
{
    struct fd f = {NULL, 0};
    pfm_context_t *ctx = NULL;
    unsigned long flags = 0UL;
    void *args_k = NULL;
    long ret; /* will expand int return types */
    size_t base_sz, sz, xtra_sz = 0;
    int narg, completed_args = 0, call_made = 0, cmd_flags;
    int (*func)(pfm_context_t *ctx, void *arg, int count, struct pt_regs *regs);
    int (*getsize)(void *arg, size_t *sz);
#define PFM_MAX_ARGSIZE 4096

    /*
     * reject any call if perfmon was disabled at initialization
     */
    if (unlikely(pmu_conf == NULL)) return -ENOSYS;

    if (unlikely(cmd < 0 || cmd >= PFM_CMD_COUNT)) {
        DPRINT(("invalid cmd=%d\n", cmd));
        return -EINVAL;
    }

    func      = pfm_cmd_tab[cmd].cmd_func;
    narg      = pfm_cmd_tab[cmd].cmd_narg;
    base_sz   = pfm_cmd_tab[cmd].cmd_argsize;
    getsize   = pfm_cmd_tab[cmd].cmd_getsize;
    cmd_flags = pfm_cmd_tab[cmd].cmd_flags;

    if (unlikely(func == NULL)) {
        DPRINT(("invalid cmd=%d\n", cmd));
        return -EINVAL;
    }

    DPRINT(("cmd=%s idx=%d narg=0x%x argsz=%lu count=%d\n",
        PFM_CMD_NAME(cmd),
        cmd,
        narg,
        base_sz,
        count));

    /*
     * check if number of arguments matches what the command expects
     */
    if (unlikely((narg == PFM_CMD_ARG_MANY && count <= 0) || (narg > 0 && narg != count)))
        return -EINVAL;

restart_args:
    sz = xtra_sz + base_sz*count;
    /*
     * limit abuse to min page size
     */
    if (unlikely(sz > PFM_MAX_ARGSIZE)) {
        printk(KERN_ERR "perfmon: [%d] argument too big %lu\n", task_pid_nr(current), sz);
        return -E2BIG;
    }

    /*
     * allocate default-sized argument buffer
     */
    if (likely(count && args_k == NULL)) {
        args_k = kmalloc(PFM_MAX_ARGSIZE, GFP_KERNEL);
        if (args_k == NULL) return -ENOMEM;
    }

    ret = -EFAULT;

    /*
     * copy arguments
     *
     * assume sz = 0 for command without parameters
     */
    if (sz && copy_from_user(args_k, arg, sz)) {
        DPRINT(("cannot copy_from_user %lu bytes @%p\n", sz, arg));
        goto error_args;
    }

    /*
     * check if command supports extra parameters
     */
    if (completed_args == 0 && getsize) {
        /*
         * get extra parameters size (based on main argument)
         */
        ret = (*getsize)(args_k, &xtra_sz);
        if (ret) goto error_args;

        completed_args = 1;

        DPRINT(("restart_args sz=%lu xtra_sz=%lu\n", sz, xtra_sz));

        /* retry if necessary */
        if (likely(xtra_sz)) goto restart_args;
    }

    if (unlikely((cmd_flags & PFM_CMD_FD) == 0)) goto skip_fd;

    ret = -EBADF;

    f = fdget(fd);
    if (unlikely(f.file == NULL)) {
        DPRINT(("invalid fd %d\n", fd));
        goto error_args;
    }
    if (unlikely(PFM_IS_FILE(f.file) == 0)) {
        DPRINT(("fd %d not related to perfmon\n", fd));
        goto error_args;
    }

    ctx = f.file->private_data;
    if (unlikely(ctx == NULL)) {
        DPRINT(("no context for fd %d\n", fd));
        goto error_args;
    }
    prefetch(&ctx->ctx_state);

    PROTECT_CTX(ctx, flags);

    /*
     * check task is stopped
     */
    ret = pfm_check_task_state(ctx, cmd, flags);
    if (unlikely(ret)) goto abort_locked;

skip_fd:
    ret = (*func)(ctx, args_k, count, task_pt_regs(current));

    call_made = 1;

abort_locked:
    if (likely(ctx)) {
        DPRINT(("context unlocked\n"));
        UNPROTECT_CTX(ctx, flags);
    }

    /* copy argument back to user, if needed */
    if (call_made && PFM_CMD_RW_ARG(cmd) && copy_to_user(arg, args_k, base_sz*count)) ret = -EFAULT;

error_args:
    if (f.file)
        fdput(f);

    kfree(args_k);

    DPRINT(("cmd=%s ret=%ld\n", PFM_CMD_NAME(cmd), ret));

    return ret;
}

static void
pfm_resume_after_ovfl(pfm_context_t *ctx, unsigned long ovfl_regs, struct pt_regs *regs)
{
    pfm_buffer_fmt_t *fmt = ctx->ctx_buf_fmt;
    pfm_ovfl_ctrl_t rst_ctrl;
    int state;
    int ret = 0;

    state = ctx->ctx_state;
    /*
     * Unlock sampling buffer and reset index atomically
     * XXX: not really needed when blocking
     */
    if (CTX_HAS_SMPL(ctx)) {

        rst_ctrl.bits.mask_monitoring = 0;
        rst_ctrl.bits.reset_ovfl_pmds = 0;

        if (state == PFM_CTX_LOADED)
            ret = pfm_buf_fmt_restart_active(fmt, current, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
        else
            ret = pfm_buf_fmt_restart(fmt, current, &rst_ctrl, ctx->ctx_smpl_hdr, regs);
    } else {
        rst_ctrl.bits.mask_monitoring = 0;
        rst_ctrl.bits.reset_ovfl_pmds = 1;
    }

    if (ret == 0) {
        if (rst_ctrl.bits.reset_ovfl_pmds) {
            pfm_reset_regs(ctx, &ovfl_regs, PFM_PMD_LONG_RESET);
        }
        if (rst_ctrl.bits.mask_monitoring == 0) {
            DPRINT(("resuming monitoring\n"));
            if (ctx->ctx_state == PFM_CTX_MASKED) pfm_restore_monitoring(current);
        } else {
            DPRINT(("stopping monitoring\n"));
            //pfm_stop_monitoring(current, regs);
        }
        ctx->ctx_state = PFM_CTX_LOADED;
    }
}

/*
 * context MUST BE LOCKED when calling
 * can only be called for current
 */
static void
pfm_context_force_terminate(pfm_context_t *ctx, struct pt_regs *regs)
{
    int ret;

    DPRINT(("entering for [%d]\n", task_pid_nr(current)));

    ret = pfm_context_unload(ctx, NULL, 0, regs);
    if (ret) {
        printk(KERN_ERR "pfm_context_force_terminate: [%d] unloaded failed with %d\n", task_pid_nr(current), ret);
    }

    /*
     * and wakeup controlling task, indicating we are now disconnected
     */
    wake_up_interruptible(&ctx->ctx_zombieq);

    /*
     * given that context is still locked, the controlling
     * task will only get access when we return from
     * pfm_handle_work().
     */
}

static int pfm_ovfl_notify_user(pfm_context_t *ctx, unsigned long ovfl_pmds);

 /*
  * pfm_handle_work() can be called with interrupts enabled
  * (TIF_NEED_RESCHED) or disabled. The down_interruptible
  * call may sleep, therefore we must re-enable interrupts
  * to avoid deadlocks. It is safe to do so because this function
  * is called ONLY when returning to user level (pUStk=1), in which case
  * there is no risk of kernel stack overflow due to deep
  * interrupt nesting.
  */
void
pfm_handle_work(void)
{
    pfm_context_t *ctx;
    struct pt_regs *regs;
    unsigned long flags, dummy_flags;
    unsigned long ovfl_regs;
    unsigned int reason;
    int ret;

    ctx = PFM_GET_CTX(current);
    if (ctx == NULL) {
        printk(KERN_ERR "perfmon: [%d] has no PFM context\n",
            task_pid_nr(current));
        return;
    }

    PROTECT_CTX(ctx, flags);

    PFM_SET_WORK_PENDING(current, 0);

    regs = task_pt_regs(current);

    /*
     * extract reason for being here and clear
     */
    reason = ctx->ctx_fl_trap_reason;
    ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_NONE;
    ovfl_regs = ctx->ctx_ovfl_regs[0];

    DPRINT(("reason=%d state=%d\n", reason, ctx->ctx_state));

    /*
     * must be done before we check for simple-reset mode
     */
    if (ctx->ctx_fl_going_zombie || ctx->ctx_state == PFM_CTX_ZOMBIE)
        goto do_zombie;

    //if (CTX_OVFL_NOBLOCK(ctx)) goto skip_blocking;
    if (reason == PFM_TRAP_REASON_RESET)
        goto skip_blocking;

    /*
     * restore interrupt mask to what it was on entry.
     * Could be enabled/diasbled.
     */
    UNPROTECT_CTX(ctx, flags);

    /*
     * force interrupt enable because of down_interruptible()
     */
    local_irq_enable();

    DPRINT(("before block sleeping\n"));

    /*
     * may go through without blocking on SMP systems
     * if restart has been received already by the time we call down()
     */
    ret = wait_for_completion_interruptible(&ctx->ctx_restart_done);

    DPRINT(("after block sleeping ret=%d\n", ret));

    /*
     * lock context and mask interrupts again
     * We save flags into a dummy because we may have
     * altered interrupts mask compared to entry in this
     * function.
     */
    PROTECT_CTX(ctx, dummy_flags);

    /*
     * we need to read the ovfl_regs only after wake-up
     * because we may have had pfm_write_pmds() in between
     * and that can changed PMD values and therefore 
     * ovfl_regs is reset for these new PMD values.
     */
    ovfl_regs = ctx->ctx_ovfl_regs[0];

    if (ctx->ctx_fl_going_zombie) {
do_zombie:
        DPRINT(("context is zombie, bailing out\n"));
        pfm_context_force_terminate(ctx, regs);
        goto nothing_to_do;
    }
    /*
     * in case of interruption of down() we don't restart anything
     */
    if (ret < 0)
        goto nothing_to_do;

skip_blocking:
    pfm_resume_after_ovfl(ctx, ovfl_regs, regs);
    ctx->ctx_ovfl_regs[0] = 0UL;

nothing_to_do:
    /*
     * restore flags as they were upon entry
     */
    UNPROTECT_CTX(ctx, flags);
}

static int
pfm_notify_user(pfm_context_t *ctx, pfm_msg_t *msg)
{
    if (ctx->ctx_state == PFM_CTX_ZOMBIE) {
        DPRINT(("ignoring overflow notification, owner is zombie\n"));
        return 0;
    }

    DPRINT(("waking up somebody\n"));

    if (msg) wake_up_interruptible(&ctx->ctx_msgq_wait);

    /*
     * safe, we are not in intr handler, nor in ctxsw when
     * we come here
     */
    kill_fasync (&ctx->ctx_async_queue, SIGIO, POLL_IN);

    return 0;
}

static int
pfm_ovfl_notify_user(pfm_context_t *ctx, unsigned long ovfl_pmds)
{
    pfm_msg_t *msg = NULL;

    if (ctx->ctx_fl_no_msg == 0) {
        msg = pfm_get_new_msg(ctx);
        if (msg == NULL) {
            printk(KERN_ERR "perfmon: pfm_ovfl_notify_user no more notification msgs\n");
            return -1;
        }

        msg->pfm_ovfl_msg.msg_type         = PFM_MSG_OVFL;
        msg->pfm_ovfl_msg.msg_ctx_fd       = ctx->ctx_fd;
        msg->pfm_ovfl_msg.msg_active_set   = 0;
        msg->pfm_ovfl_msg.msg_ovfl_pmds[0] = ovfl_pmds;
        msg->pfm_ovfl_msg.msg_ovfl_pmds[1] = 0UL;
        msg->pfm_ovfl_msg.msg_ovfl_pmds[2] = 0UL;
        msg->pfm_ovfl_msg.msg_ovfl_pmds[3] = 0UL;
        msg->pfm_ovfl_msg.msg_tstamp       = 0UL;
    }

    DPRINT(("ovfl msg: msg=%p no_msg=%d fd=%d ovfl_pmds=0x%lx\n",
        msg,
        ctx->ctx_fl_no_msg,
        ctx->ctx_fd,
        ovfl_pmds));

    return pfm_notify_user(ctx, msg);
}

static int
pfm_end_notify_user(pfm_context_t *ctx)
{
    pfm_msg_t *msg;

    msg = pfm_get_new_msg(ctx);
    if (msg == NULL) {
        printk(KERN_ERR "perfmon: pfm_end_notify_user no more notification msgs\n");
        return -1;
    }
    /* no leak */
    memset(msg, 0, sizeof(*msg));

    msg->pfm_end_msg.msg_type    = PFM_MSG_END;
    msg->pfm_end_msg.msg_ctx_fd  = ctx->ctx_fd;
    msg->pfm_ovfl_msg.msg_tstamp = 0UL;

    DPRINT(("end msg: msg=%p no_msg=%d ctx_fd=%d\n",
        msg,
        ctx->ctx_fl_no_msg,
        ctx->ctx_fd));

    return pfm_notify_user(ctx, msg);
}

/*
 * main overflow processing routine.
 * it can be called from the interrupt path or explicitly during the context switch code
 */
static void pfm_overflow_handler(struct task_struct *task, pfm_context_t *ctx,
                unsigned long pmc0, struct pt_regs *regs)
{
    pfm_ovfl_arg_t *ovfl_arg;
    unsigned long mask;
    unsigned long old_val, ovfl_val, new_val;
    unsigned long ovfl_notify = 0UL, ovfl_pmds = 0UL, smpl_pmds = 0UL, reset_pmds;
    unsigned long tstamp;
    pfm_ovfl_ctrl_t ovfl_ctrl;
    unsigned int i, has_smpl;
    int must_notify = 0;

    if (unlikely(ctx->ctx_state == PFM_CTX_ZOMBIE)) goto stop_monitoring;

    /*
     * sanity test. Should never happen
     */
    if (unlikely((pmc0 & 0x1) == 0)) goto sanity_check;

    tstamp   = ia64_get_itc();
    mask     = pmc0 >> PMU_FIRST_COUNTER;
    ovfl_val = pmu_conf->ovfl_val;
    has_smpl = CTX_HAS_SMPL(ctx);

    DPRINT_ovfl(("pmc0=0x%lx pid=%d iip=0x%lx, %s "
             "used_pmds=0x%lx\n",
            pmc0,
            task ? task_pid_nr(task): -1,
            (regs ? regs->cr_iip : 0),
            CTX_OVFL_NOBLOCK(ctx) ? "nonblocking" : "blocking",
            ctx->ctx_used_pmds[0]));


    /*
     * first we update the virtual counters
     * assume there was a prior ia64_srlz_d() issued
     */
    for (i = PMU_FIRST_COUNTER; mask ; i++, mask >>= 1) {

        /* skip pmd which did not overflow */
        if ((mask & 0x1) == 0) continue;

        /*
         * Note that the pmd is not necessarily 0 at this point as qualified events
         * may have happened before the PMU was frozen. The residual count is not
         * taken into consideration here but will be with any read of the pmd via
         * pfm_read_pmds().
         */
        old_val              = new_val = ctx->ctx_pmds[i].val;
        new_val             += 1 + ovfl_val;
        ctx->ctx_pmds[i].val = new_val;

        /*
         * check for overflow condition
         */
        if (likely(old_val > new_val)) {
            ovfl_pmds |= 1UL << i;
            if (PMC_OVFL_NOTIFY(ctx, i)) ovfl_notify |= 1UL << i;
        }

        DPRINT_ovfl(("ctx_pmd[%d].val=0x%lx old_val=0x%lx pmd=0x%lx ovfl_pmds=0x%lx ovfl_notify=0x%lx\n",
            i,
            new_val,
            old_val,
            ia64_get_pmd(i) & ovfl_val,
            ovfl_pmds,
            ovfl_notify));
    }

    /*
     * there was no 64-bit overflow, nothing else to do
     */
    if (ovfl_pmds == 0UL) return;

    /* 
     * reset all control bits
     */
    ovfl_ctrl.val = 0;
    reset_pmds    = 0UL;

    /*
     * if a sampling format module exists, then we "cache" the overflow by 
     * calling the module's handler() routine.
     */
    if (has_smpl) {
        unsigned long start_cycles, end_cycles;
        unsigned long pmd_mask;
        int j, k, ret = 0;
        int this_cpu = smp_processor_id();

        pmd_mask = ovfl_pmds >> PMU_FIRST_COUNTER;
        ovfl_arg = &ctx->ctx_ovfl_arg;

        prefetch(ctx->ctx_smpl_hdr);

        for(i=PMU_FIRST_COUNTER; pmd_mask && ret == 0; i++, pmd_mask >>=1) {

            mask = 1UL << i;

            if ((pmd_mask & 0x1) == 0) continue;

            ovfl_arg->ovfl_pmd      = (unsigned char )i;
            ovfl_arg->ovfl_notify   = ovfl_notify & mask ? 1 : 0;
            ovfl_arg->active_set    = 0;
            ovfl_arg->ovfl_ctrl.val = 0; /* module must fill in all fields */
            ovfl_arg->smpl_pmds[0]  = smpl_pmds = ctx->ctx_pmds[i].smpl_pmds[0];

            ovfl_arg->pmd_value      = ctx->ctx_pmds[i].val;
            ovfl_arg->pmd_last_reset = ctx->ctx_pmds[i].lval;
            ovfl_arg->pmd_eventid    = ctx->ctx_pmds[i].eventid;

            /*
             * copy values of pmds of interest. Sampling format may copy them
             * into sampling buffer.
             */
            if (smpl_pmds) {
                for(j=0, k=0; smpl_pmds; j++, smpl_pmds >>=1) {
                    if ((smpl_pmds & 0x1) == 0) continue;
                    ovfl_arg->smpl_pmds_values[k++] = PMD_IS_COUNTING(j) ?  pfm_read_soft_counter(ctx, j) : ia64_get_pmd(j);
                    DPRINT_ovfl(("smpl_pmd[%d]=pmd%u=0x%lx\n", k-1, j, ovfl_arg->smpl_pmds_values[k-1]));
                }
            }

            pfm_stats[this_cpu].pfm_smpl_handler_calls++;

            start_cycles = ia64_get_itc();

            /*
             * call custom buffer format record (handler) routine
             */
            ret = (*ctx->ctx_buf_fmt->fmt_handler)(task, ctx->ctx_smpl_hdr, ovfl_arg, regs, tstamp);

            end_cycles = ia64_get_itc();

            /*
             * For those controls, we take the union because they have
             * an all or nothing behavior.
             */
            ovfl_ctrl.bits.notify_user     |= ovfl_arg->ovfl_ctrl.bits.notify_user;
            ovfl_ctrl.bits.block_task      |= ovfl_arg->ovfl_ctrl.bits.block_task;
            ovfl_ctrl.bits.mask_monitoring |= ovfl_arg->ovfl_ctrl.bits.mask_monitoring;
            /*
             * build the bitmask of pmds to reset now
             */
            if (ovfl_arg->ovfl_ctrl.bits.reset_ovfl_pmds) reset_pmds |= mask;

            pfm_stats[this_cpu].pfm_smpl_handler_cycles += end_cycles - start_cycles;
        }
        /*
         * when the module cannot handle the rest of the overflows, we abort right here
         */
        if (ret && pmd_mask) {
            DPRINT(("handler aborts leftover ovfl_pmds=0x%lx\n",
                pmd_mask<<PMU_FIRST_COUNTER));
        }
        /*
         * remove the pmds we reset now from the set of pmds to reset in pfm_restart()
         */
        ovfl_pmds &= ~reset_pmds;
    } else {
        /*
         * when no sampling module is used, then the default
         * is to notify on overflow if requested by user
         */
        ovfl_ctrl.bits.notify_user     = ovfl_notify ? 1 : 0;
        ovfl_ctrl.bits.block_task      = ovfl_notify ? 1 : 0;
        ovfl_ctrl.bits.mask_monitoring = ovfl_notify ? 1 : 0; /* XXX: change for saturation */
        ovfl_ctrl.bits.reset_ovfl_pmds = ovfl_notify ? 0 : 1;
        /*
         * if needed, we reset all overflowed pmds
         */
        if (ovfl_notify == 0) reset_pmds = ovfl_pmds;
    }

    DPRINT_ovfl(("ovfl_pmds=0x%lx reset_pmds=0x%lx\n", ovfl_pmds, reset_pmds));

    /*
     * reset the requested PMD registers using the short reset values
     */
    if (reset_pmds) {
        unsigned long bm = reset_pmds;
        pfm_reset_regs(ctx, &bm, PFM_PMD_SHORT_RESET);
    }

    if (ovfl_notify && ovfl_ctrl.bits.notify_user) {
        /*
         * keep track of what to reset when unblocking
         */
        ctx->ctx_ovfl_regs[0] = ovfl_pmds;

        /*
         * check for blocking context 
         */
        if (CTX_OVFL_NOBLOCK(ctx) == 0 && ovfl_ctrl.bits.block_task) {

            ctx->ctx_fl_trap_reason = PFM_TRAP_REASON_BLOCK;

            /*
             * set the perfmon specific checking pending work for the task
             */
            PFM_SET_WORK_PENDING(task, 1);

            /*
             * when coming from ctxsw, current still points to the
             * previous task, therefore we must work with task and not current.
             */
            set_notify_resume(task);
        }
        /*
         * defer until state is changed (shorten spin window). the context is locked
         * anyway, so the signal receiver would come spin for nothing.
         */
        must_notify = 1;
    }

    DPRINT_ovfl(("owner [%d] pending=%ld reason=%u ovfl_pmds=0x%lx ovfl_notify=0x%lx masked=%d\n",
            GET_PMU_OWNER() ? task_pid_nr(GET_PMU_OWNER()) : -1,
            PFM_GET_WORK_PENDING(task),
            ctx->ctx_fl_trap_reason,
            ovfl_pmds,
            ovfl_notify,
            ovfl_ctrl.bits.mask_monitoring ? 1 : 0));
    /*
     * in case monitoring must be stopped, we toggle the psr bits
     */
    if (ovfl_ctrl.bits.mask_monitoring) {
        pfm_mask_monitoring(task);
        ctx->ctx_state = PFM_CTX_MASKED;
        ctx->ctx_fl_can_restart = 1;
    }

    /*
     * send notification now
     */
    if (must_notify) pfm_ovfl_notify_user(ctx, ovfl_notify);

    return;

sanity_check:
    printk(KERN_ERR "perfmon: CPU%d overflow handler [%d] pmc0=0x%lx\n",
            smp_processor_id(),
            task ? task_pid_nr(task) : -1,
            pmc0);
    return;

stop_monitoring:
    /*
     * in SMP, zombie context is never restored but reclaimed in pfm_load_regs().
     * Moreover, zombies are also reclaimed in pfm_save_regs(). Therefore we can
     * come here as zombie only if the task is the current task. In which case, we
     * can access the PMU  hardware directly.
     *
     * Note that zombies do have PM_VALID set. So here we do the minimal.
     *
     * In case the context was zombified it could not be reclaimed at the time
     * the monitoring program exited. At this point, the PMU reservation has been
     * returned, the sampiing buffer has been freed. We must convert this call
     * into a spurious interrupt. However, we must also avoid infinite overflows
     * by stopping monitoring for this task. We can only come here for a per-task
     * context. All we need to do is to stop monitoring using the psr bits which
     * are always task private. By re-enabling secure montioring, we ensure that
     * the monitored task will not be able to re-activate monitoring.
     * The task will eventually be context switched out, at which point the context
     * will be reclaimed (that includes releasing ownership of the PMU).
     *
     * So there might be a window of time where the number of per-task session is zero
     * yet one PMU might have a owner and get at most one overflow interrupt for a zombie
     * context. This is safe because if a per-task session comes in, it will push this one
     * out and by the virtue on pfm_save_regs(), this one will disappear. If a system wide
     * session is force on that CPU, given that we use task pinning, pfm_save_regs() will
     * also push our zombie context out.
     *
     * Overall pretty hairy stuff....
     */
    DPRINT(("ctx is zombie for [%d], converted to spurious\n", task ? task_pid_nr(task): -1));
    pfm_clear_psr_up();
    ia64_psr(regs)->up = 0;
    ia64_psr(regs)->sp = 1;
    return;
}

static int
pfm_do_interrupt_handler(void *arg, struct pt_regs *regs)
{
    struct task_struct *task;
    pfm_context_t *ctx;
    unsigned long flags;
    u64 pmc0;
    int this_cpu = smp_processor_id();
    int retval = 0;

    pfm_stats[this_cpu].pfm_ovfl_intr_count++;

    /*
     * srlz.d done before arriving here
     */
    pmc0 = ia64_get_pmc(0);

    task = GET_PMU_OWNER();
    ctx  = GET_PMU_CTX();

    /*
     * if we have some pending bits set
     * assumes : if any PMC0.bit[63-1] is set, then PMC0.fr = 1
     */
    if (PMC0_HAS_OVFL(pmc0) && task) {
        /*
         * we assume that pmc0.fr is always set here
         */

        /* sanity check */
        if (!ctx) goto report_spurious1;

        if (ctx->ctx_fl_system == 0 && (task->thread.flags & IA64_THREAD_PM_VALID) == 0) 
            goto report_spurious2;

        PROTECT_CTX_NOPRINT(ctx, flags);

        pfm_overflow_handler(task, ctx, pmc0, regs);

        UNPROTECT_CTX_NOPRINT(ctx, flags);

    } else {
        pfm_stats[this_cpu].pfm_spurious_ovfl_intr_count++;
        retval = -1;
    }
    /*
     * keep it unfrozen at all times
     */
    pfm_unfreeze_pmu();

    return retval;

report_spurious1:
    printk(KERN_INFO "perfmon: spurious overflow interrupt on CPU%d: process %d has no PFM context\n",
        this_cpu, task_pid_nr(task));
    pfm_unfreeze_pmu();
    return -1;
report_spurious2:
    printk(KERN_INFO "perfmon: spurious overflow interrupt on CPU%d: process %d, invalid flag\n", 
        this_cpu, 
        task_pid_nr(task));
    pfm_unfreeze_pmu();
    return -1;
}

static irqreturn_t
pfm_interrupt_handler(int irq, void *arg)
{
    unsigned long start_cycles, total_cycles;
    unsigned long min, max;
    int this_cpu;
    int ret;
    struct pt_regs *regs = get_irq_regs();

    this_cpu = get_cpu();
    if (likely(!pfm_alt_intr_handler)) {
        min = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min;
        max = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max;

        start_cycles = ia64_get_itc();

        ret = pfm_do_interrupt_handler(arg, regs);

        total_cycles = ia64_get_itc();

        /*
         * don't measure spurious interrupts
         */
        if (likely(ret == 0)) {
            total_cycles -= start_cycles;

            if (total_cycles < min) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min = total_cycles;
            if (total_cycles > max) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max = total_cycles;

            pfm_stats[this_cpu].pfm_ovfl_intr_cycles += total_cycles;
        }
    }
    else {
        (*pfm_alt_intr_handler->handler)(irq, arg, regs);
    }

    put_cpu();
    return IRQ_HANDLED;
}

/*
 * /proc/perfmon interface, for debug only
 */

#define PFM_PROC_SHOW_HEADER    ((void *)(long)nr_cpu_ids+1)

static void *
pfm_proc_start(struct seq_file *m, loff_t *pos)
{
    if (*pos == 0) {
        return PFM_PROC_SHOW_HEADER;
    }

    while (*pos <= nr_cpu_ids) {
        if (cpu_online(*pos - 1)) {
            return (void *)*pos;
        }
        ++*pos;
    }
    return NULL;
}

static void *
pfm_proc_next(struct seq_file *m, void *v, loff_t *pos)
{
    ++*pos;
    return pfm_proc_start(m, pos);
}

static void
pfm_proc_stop(struct seq_file *m, void *v)
{
}

static void
pfm_proc_show_header(struct seq_file *m)
{
    struct list_head * pos;
    pfm_buffer_fmt_t * entry;
    unsigned long flags;

    seq_printf(m,
        "perfmon version           : %u.%u\n"
        "model                     : %s\n"
        "fastctxsw                 : %s\n"
        "expert mode               : %s\n"
        "ovfl_mask                 : 0x%lx\n"
        "PMU flags                 : 0x%x\n",
        PFM_VERSION_MAJ, PFM_VERSION_MIN,
        pmu_conf->pmu_name,
        pfm_sysctl.fastctxsw > 0 ? "Yes": "No",
        pfm_sysctl.expert_mode > 0 ? "Yes": "No",
        pmu_conf->ovfl_val,
        pmu_conf->flags);

    LOCK_PFS(flags);

    seq_printf(m,
        "proc_sessions             : %u\n"
        "sys_sessions              : %u\n"
        "sys_use_dbregs            : %u\n"
        "ptrace_use_dbregs         : %u\n",
        pfm_sessions.pfs_task_sessions,
        pfm_sessions.pfs_sys_sessions,
        pfm_sessions.pfs_sys_use_dbregs,
        pfm_sessions.pfs_ptrace_use_dbregs);

    UNLOCK_PFS(flags);

    spin_lock(&pfm_buffer_fmt_lock);

    list_for_each(pos, &pfm_buffer_fmt_list) {
        entry = list_entry(pos, pfm_buffer_fmt_t, fmt_list);
        seq_printf(m, "format                    : %02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x %s\n",
            entry->fmt_uuid[0],
            entry->fmt_uuid[1],
            entry->fmt_uuid[2],
            entry->fmt_uuid[3],
            entry->fmt_uuid[4],
            entry->fmt_uuid[5],
            entry->fmt_uuid[6],
            entry->fmt_uuid[7],
            entry->fmt_uuid[8],
            entry->fmt_uuid[9],
            entry->fmt_uuid[10],
            entry->fmt_uuid[11],
            entry->fmt_uuid[12],
            entry->fmt_uuid[13],
            entry->fmt_uuid[14],
            entry->fmt_uuid[15],
            entry->fmt_name);
    }
    spin_unlock(&pfm_buffer_fmt_lock);

}

static int
pfm_proc_show(struct seq_file *m, void *v)
{
    unsigned long psr;
    unsigned int i;
    int cpu;

    if (v == PFM_PROC_SHOW_HEADER) {
        pfm_proc_show_header(m);
        return 0;
    }

    /* show info for CPU (v - 1) */

    cpu = (long)v - 1;
    seq_printf(m,
        "CPU%-2d overflow intrs      : %lu\n"
        "CPU%-2d overflow cycles     : %lu\n"
        "CPU%-2d overflow min        : %lu\n"
        "CPU%-2d overflow max        : %lu\n"
        "CPU%-2d smpl handler calls  : %lu\n"
        "CPU%-2d smpl handler cycles : %lu\n"
        "CPU%-2d spurious intrs      : %lu\n"
        "CPU%-2d replay   intrs      : %lu\n"
        "CPU%-2d syst_wide           : %d\n"
        "CPU%-2d dcr_pp              : %d\n"
        "CPU%-2d exclude idle        : %d\n"
        "CPU%-2d owner               : %d\n"
        "CPU%-2d context             : %p\n"
        "CPU%-2d activations         : %lu\n",
        cpu, pfm_stats[cpu].pfm_ovfl_intr_count,
        cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles,
        cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles_min,
        cpu, pfm_stats[cpu].pfm_ovfl_intr_cycles_max,
        cpu, pfm_stats[cpu].pfm_smpl_handler_calls,
        cpu, pfm_stats[cpu].pfm_smpl_handler_cycles,
        cpu, pfm_stats[cpu].pfm_spurious_ovfl_intr_count,
        cpu, pfm_stats[cpu].pfm_replay_ovfl_intr_count,
        cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_SYST_WIDE ? 1 : 0,
        cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_DCR_PP ? 1 : 0,
        cpu, pfm_get_cpu_data(pfm_syst_info, cpu) & PFM_CPUINFO_EXCL_IDLE ? 1 : 0,
        cpu, pfm_get_cpu_data(pmu_owner, cpu) ? pfm_get_cpu_data(pmu_owner, cpu)->pid: -1,
        cpu, pfm_get_cpu_data(pmu_ctx, cpu),
        cpu, pfm_get_cpu_data(pmu_activation_number, cpu));

    if (num_online_cpus() == 1 && pfm_sysctl.debug > 0) {

        psr = pfm_get_psr();

        ia64_srlz_d();

        seq_printf(m, 
            "CPU%-2d psr                 : 0x%lx\n"
            "CPU%-2d pmc0                : 0x%lx\n", 
            cpu, psr,
            cpu, ia64_get_pmc(0));

        for (i=0; PMC_IS_LAST(i) == 0;  i++) {
            if (PMC_IS_COUNTING(i) == 0) continue;
            seq_printf(m, 
                "CPU%-2d pmc%u                : 0x%lx\n"
                "CPU%-2d pmd%u                : 0x%lx\n", 
                cpu, i, ia64_get_pmc(i),
                cpu, i, ia64_get_pmd(i));
        }
    }
    return 0;
}

const struct seq_operations pfm_seq_ops = {
    .start =    pfm_proc_start,
    .next =     pfm_proc_next,
    .stop =     pfm_proc_stop,
    .show =     pfm_proc_show
};

static int
pfm_proc_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &pfm_seq_ops);
}


/*
 * we come here as soon as local_cpu_data->pfm_syst_wide is set. this happens
 * during pfm_enable() hence before pfm_start(). We cannot assume monitoring
 * is active or inactive based on mode. We must rely on the value in
 * local_cpu_data->pfm_syst_info
 */
void
pfm_syst_wide_update_task(struct task_struct *task, unsigned long info, int is_ctxswin)
{
    struct pt_regs *regs;
    unsigned long dcr;
    unsigned long dcr_pp;

    dcr_pp = info & PFM_CPUINFO_DCR_PP ? 1 : 0;

    /*
     * pid 0 is guaranteed to be the idle task. There is one such task with pid 0
     * on every CPU, so we can rely on the pid to identify the idle task.
     */
    if ((info & PFM_CPUINFO_EXCL_IDLE) == 0 || task->pid) {
        regs = task_pt_regs(task);
        ia64_psr(regs)->pp = is_ctxswin ? dcr_pp : 0;
        return;
    }
    /*
     * if monitoring has started
     */
    if (dcr_pp) {
        dcr = ia64_getreg(_IA64_REG_CR_DCR);
        /*
         * context switching in?
         */
        if (is_ctxswin) {
            /* mask monitoring for the idle task */
            ia64_setreg(_IA64_REG_CR_DCR, dcr & ~IA64_DCR_PP);
            pfm_clear_psr_pp();
            ia64_srlz_i();
            return;
        }
        /*
         * context switching out
         * restore monitoring for next task
         *
         * Due to inlining this odd if-then-else construction generates
         * better code.
         */
        ia64_setreg(_IA64_REG_CR_DCR, dcr |IA64_DCR_PP);
        pfm_set_psr_pp();
        ia64_srlz_i();
    }
}

#ifdef CONFIG_SMP

static void
pfm_force_cleanup(pfm_context_t *ctx, struct pt_regs *regs)
{
    struct task_struct *task = ctx->ctx_task;

    ia64_psr(regs)->up = 0;
    ia64_psr(regs)->sp = 1;

    if (GET_PMU_OWNER() == task) {
        DPRINT(("cleared ownership for [%d]\n",
                    task_pid_nr(ctx->ctx_task)));
        SET_PMU_OWNER(NULL, NULL);
    }

    /*
     * disconnect the task from the context and vice-versa
     */
    PFM_SET_WORK_PENDING(task, 0);

    task->thread.pfm_context  = NULL;
    task->thread.flags       &= ~IA64_THREAD_PM_VALID;

    DPRINT(("force cleanup for [%d]\n",  task_pid_nr(task)));
}


/*
 * in 2.6, interrupts are masked when we come here and the runqueue lock is held
 */
void
pfm_save_regs(struct task_struct *task)
{
    pfm_context_t *ctx;
    unsigned long flags;
    u64 psr;


    ctx = PFM_GET_CTX(task);
    if (ctx == NULL) return;

    /*
     * we always come here with interrupts ALREADY disabled by
     * the scheduler. So we simply need to protect against concurrent
     * access, not CPU concurrency.
     */
    flags = pfm_protect_ctx_ctxsw(ctx);

    if (ctx->ctx_state == PFM_CTX_ZOMBIE) {
        struct pt_regs *regs = task_pt_regs(task);

        pfm_clear_psr_up();

        pfm_force_cleanup(ctx, regs);

        BUG_ON(ctx->ctx_smpl_hdr);

        pfm_unprotect_ctx_ctxsw(ctx, flags);

        pfm_context_free(ctx);
        return;
    }

    /*
     * save current PSR: needed because we modify it
     */
    ia64_srlz_d();
    psr = pfm_get_psr();

    BUG_ON(psr & (IA64_PSR_I));

    /*
     * stop monitoring:
     * This is the last instruction which may generate an overflow
     *
     * We do not need to set psr.sp because, it is irrelevant in kernel.
     * It will be restored from ipsr when going back to user level
     */
    pfm_clear_psr_up();

    /*
     * keep a copy of psr.up (for reload)
     */
    ctx->ctx_saved_psr_up = psr & IA64_PSR_UP;

    /*
     * release ownership of this PMU.
     * PM interrupts are masked, so nothing
     * can happen.
     */
    SET_PMU_OWNER(NULL, NULL);

    /*
     * we systematically save the PMD as we have no
     * guarantee we will be schedule at that same
     * CPU again.
     */
    pfm_save_pmds(ctx->th_pmds, ctx->ctx_used_pmds[0]);

    /*
     * save pmc0 ia64_srlz_d() done in pfm_save_pmds()
     * we will need it on the restore path to check
     * for pending overflow.
     */
    ctx->th_pmcs[0] = ia64_get_pmc(0);

    /*
     * unfreeze PMU if had pending overflows
     */
    if (ctx->th_pmcs[0] & ~0x1UL) pfm_unfreeze_pmu();

    /*
     * finally, allow context access.
     * interrupts will still be masked after this call.
     */
    pfm_unprotect_ctx_ctxsw(ctx, flags);
}

#else /* !CONFIG_SMP */
void
pfm_save_regs(struct task_struct *task)
{
    pfm_context_t *ctx;
    u64 psr;

    ctx = PFM_GET_CTX(task);
    if (ctx == NULL) return;

    /*
     * save current PSR: needed because we modify it
     */
    psr = pfm_get_psr();

    BUG_ON(psr & (IA64_PSR_I));

    /*
     * stop monitoring:
     * This is the last instruction which may generate an overflow
     *
     * We do not need to set psr.sp because, it is irrelevant in kernel.
     * It will be restored from ipsr when going back to user level
     */
    pfm_clear_psr_up();

    /*
     * keep a copy of psr.up (for reload)
     */
    ctx->ctx_saved_psr_up = psr & IA64_PSR_UP;
}

static void
pfm_lazy_save_regs (struct task_struct *task)
{
    pfm_context_t *ctx;
    unsigned long flags;

    { u64 psr  = pfm_get_psr();
      BUG_ON(psr & IA64_PSR_UP);
    }

    ctx = PFM_GET_CTX(task);

    /*
     * we need to mask PMU overflow here to
     * make sure that we maintain pmc0 until
     * we save it. overflow interrupts are
     * treated as spurious if there is no
     * owner.
     *
     * XXX: I don't think this is necessary
     */
    PROTECT_CTX(ctx,flags);

    /*
     * release ownership of this PMU.
     * must be done before we save the registers.
     *
     * after this call any PMU interrupt is treated
     * as spurious.
     */
    SET_PMU_OWNER(NULL, NULL);

    /*
     * save all the pmds we use
     */
    pfm_save_pmds(ctx->th_pmds, ctx->ctx_used_pmds[0]);

    /*
     * save pmc0 ia64_srlz_d() done in pfm_save_pmds()
     * it is needed to check for pended overflow
     * on the restore path
     */
    ctx->th_pmcs[0] = ia64_get_pmc(0);

    /*
     * unfreeze PMU if had pending overflows
     */
    if (ctx->th_pmcs[0] & ~0x1UL) pfm_unfreeze_pmu();

    /*
     * now get can unmask PMU interrupts, they will
     * be treated as purely spurious and we will not
     * lose any information
     */
    UNPROTECT_CTX(ctx,flags);
}
#endif /* CONFIG_SMP */

#ifdef CONFIG_SMP
/*
 * in 2.6, interrupts are masked when we come here and the runqueue lock is held
 */
void
pfm_load_regs (struct task_struct *task)
{
    pfm_context_t *ctx;
    unsigned long pmc_mask = 0UL, pmd_mask = 0UL;
    unsigned long flags;
    u64 psr, psr_up;
    int need_irq_resend;

    ctx = PFM_GET_CTX(task);
    if (unlikely(ctx == NULL)) return;

    BUG_ON(GET_PMU_OWNER());

    /*
     * possible on unload
     */
    if (unlikely((task->thread.flags & IA64_THREAD_PM_VALID) == 0)) return;

    /*
     * we always come here with interrupts ALREADY disabled by
     * the scheduler. So we simply need to protect against concurrent
     * access, not CPU concurrency.
     */
    flags = pfm_protect_ctx_ctxsw(ctx);
    psr   = pfm_get_psr();

    need_irq_resend = pmu_conf->flags & PFM_PMU_IRQ_RESEND;

    BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
    BUG_ON(psr & IA64_PSR_I);

    if (unlikely(ctx->ctx_state == PFM_CTX_ZOMBIE)) {
        struct pt_regs *regs = task_pt_regs(task);

        BUG_ON(ctx->ctx_smpl_hdr);

        pfm_force_cleanup(ctx, regs);

        pfm_unprotect_ctx_ctxsw(ctx, flags);

        /*
         * this one (kmalloc'ed) is fine with interrupts disabled
         */
        pfm_context_free(ctx);

        return;
    }

    /*
     * we restore ALL the debug registers to avoid picking up
     * stale state.
     */
    if (ctx->ctx_fl_using_dbreg) {
        pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
        pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
    }
    /*
     * retrieve saved psr.up
     */
    psr_up = ctx->ctx_saved_psr_up;

    /*
     * if we were the last user of the PMU on that CPU,
     * then nothing to do except restore psr
     */
    if (GET_LAST_CPU(ctx) == smp_processor_id() && ctx->ctx_last_activation == GET_ACTIVATION()) {

        /*
         * retrieve partial reload masks (due to user modifications)
         */
        pmc_mask = ctx->ctx_reload_pmcs[0];
        pmd_mask = ctx->ctx_reload_pmds[0];

    } else {
        /*
         * To avoid leaking information to the user level when psr.sp=0,
         * we must reload ALL implemented pmds (even the ones we don't use).
         * In the kernel we only allow PFM_READ_PMDS on registers which
         * we initialized or requested (sampling) so there is no risk there.
         */
        pmd_mask = pfm_sysctl.fastctxsw ?  ctx->ctx_used_pmds[0] : ctx->ctx_all_pmds[0];

        /*
         * ALL accessible PMCs are systematically reloaded, unused registers
         * get their default (from pfm_reset_pmu_state()) values to avoid picking
         * up stale configuration.
         *
         * PMC0 is never in the mask. It is always restored separately.
         */
        pmc_mask = ctx->ctx_all_pmcs[0];
    }
    /*
     * when context is MASKED, we will restore PMC with plm=0
     * and PMD with stale information, but that's ok, nothing
     * will be captured.
     *
     * XXX: optimize here
     */
    if (pmd_mask) pfm_restore_pmds(ctx->th_pmds, pmd_mask);
    if (pmc_mask) pfm_restore_pmcs(ctx->th_pmcs, pmc_mask);

    /*
     * check for pending overflow at the time the state
     * was saved.
     */
    if (unlikely(PMC0_HAS_OVFL(ctx->th_pmcs[0]))) {
        /*
         * reload pmc0 with the overflow information
         * On McKinley PMU, this will trigger a PMU interrupt
         */
        ia64_set_pmc(0, ctx->th_pmcs[0]);
        ia64_srlz_d();
        ctx->th_pmcs[0] = 0UL;

        /*
         * will replay the PMU interrupt
         */
        if (need_irq_resend) ia64_resend_irq(IA64_PERFMON_VECTOR);

        pfm_stats[smp_processor_id()].pfm_replay_ovfl_intr_count++;
    }

    /*
     * we just did a reload, so we reset the partial reload fields
     */
    ctx->ctx_reload_pmcs[0] = 0UL;
    ctx->ctx_reload_pmds[0] = 0UL;

    SET_LAST_CPU(ctx, smp_processor_id());

    /*
     * dump activation value for this PMU
     */
    INC_ACTIVATION();
    /*
     * record current activation for this context
     */
    SET_ACTIVATION(ctx);

    /*
     * establish new ownership. 
     */
    SET_PMU_OWNER(task, ctx);

    /*
     * restore the psr.up bit. measurement
     * is active again.
     * no PMU interrupt can happen at this point
     * because we still have interrupts disabled.
     */
    if (likely(psr_up)) pfm_set_psr_up();

    /*
     * allow concurrent access to context
     */
    pfm_unprotect_ctx_ctxsw(ctx, flags);
}
#else /*  !CONFIG_SMP */
/*
 * reload PMU state for UP kernels
 * in 2.5 we come here with interrupts disabled
 */
void
pfm_load_regs (struct task_struct *task)
{
    pfm_context_t *ctx;
    struct task_struct *owner;
    unsigned long pmd_mask, pmc_mask;
    u64 psr, psr_up;
    int need_irq_resend;

    owner = GET_PMU_OWNER();
    ctx   = PFM_GET_CTX(task);
    psr   = pfm_get_psr();

    BUG_ON(psr & (IA64_PSR_UP|IA64_PSR_PP));
    BUG_ON(psr & IA64_PSR_I);

    /*
     * we restore ALL the debug registers to avoid picking up
     * stale state.
     *
     * This must be done even when the task is still the owner
     * as the registers may have been modified via ptrace()
     * (not perfmon) by the previous task.
     */
    if (ctx->ctx_fl_using_dbreg) {
        pfm_restore_ibrs(ctx->ctx_ibrs, pmu_conf->num_ibrs);
        pfm_restore_dbrs(ctx->ctx_dbrs, pmu_conf->num_dbrs);
    }

    /*
     * retrieved saved psr.up
     */
    psr_up = ctx->ctx_saved_psr_up;
    need_irq_resend = pmu_conf->flags & PFM_PMU_IRQ_RESEND;

    /*
     * short path, our state is still there, just
     * need to restore psr and we go
     *
     * we do not touch either PMC nor PMD. the psr is not touched
     * by the overflow_handler. So we are safe w.r.t. to interrupt
     * concurrency even without interrupt masking.
     */
    if (likely(owner == task)) {
        if (likely(psr_up)) pfm_set_psr_up();
        return;
    }

    /*
     * someone else is still using the PMU, first push it out and
     * then we'll be able to install our stuff !
     *
     * Upon return, there will be no owner for the current PMU
     */
    if (owner) pfm_lazy_save_regs(owner);

    /*
     * To avoid leaking information to the user level when psr.sp=0,
     * we must reload ALL implemented pmds (even the ones we don't use).
     * In the kernel we only allow PFM_READ_PMDS on registers which
     * we initialized or requested (sampling) so there is no risk there.
     */
    pmd_mask = pfm_sysctl.fastctxsw ?  ctx->ctx_used_pmds[0] : ctx->ctx_all_pmds[0];

    /*
     * ALL accessible PMCs are systematically reloaded, unused registers
     * get their default (from pfm_reset_pmu_state()) values to avoid picking
     * up stale configuration.
     *
     * PMC0 is never in the mask. It is always restored separately
     */
    pmc_mask = ctx->ctx_all_pmcs[0];

    pfm_restore_pmds(ctx->th_pmds, pmd_mask);
    pfm_restore_pmcs(ctx->th_pmcs, pmc_mask);

    /*
     * check for pending overflow at the time the state
     * was saved.
     */
    if (unlikely(PMC0_HAS_OVFL(ctx->th_pmcs[0]))) {
        /*
         * reload pmc0 with the overflow information
         * On McKinley PMU, this will trigger a PMU interrupt
         */
        ia64_set_pmc(0, ctx->th_pmcs[0]);
        ia64_srlz_d();

        ctx->th_pmcs[0] = 0UL;

        /*
         * will replay the PMU interrupt
         */
        if (need_irq_resend) ia64_resend_irq(IA64_PERFMON_VECTOR);

        pfm_stats[smp_processor_id()].pfm_replay_ovfl_intr_count++;
    }

    /*
     * establish new ownership. 
     */
    SET_PMU_OWNER(task, ctx);

    /*
     * restore the psr.up bit. measurement
     * is active again.
     * no PMU interrupt can happen at this point
     * because we still have interrupts disabled.
     */
    if (likely(psr_up)) pfm_set_psr_up();
}
#endif /* CONFIG_SMP */

/*
 * this function assumes monitoring is stopped
 */
static void
pfm_flush_pmds(struct task_struct *task, pfm_context_t *ctx)
{
    u64 pmc0;
    unsigned long mask2, val, pmd_val, ovfl_val;
    int i, can_access_pmu = 0;
    int is_self;

    /*
     * is the caller the task being monitored (or which initiated the
     * session for system wide measurements)
     */
    is_self = ctx->ctx_task == task ? 1 : 0;

    /*
     * can access PMU is task is the owner of the PMU state on the current CPU
     * or if we are running on the CPU bound to the context in system-wide mode
     * (that is not necessarily the task the context is attached to in this mode).
     * In system-wide we always have can_access_pmu true because a task running on an
     * invalid processor is flagged earlier in the call stack (see pfm_stop).
     */
    can_access_pmu = (GET_PMU_OWNER() == task) || (ctx->ctx_fl_system && ctx->ctx_cpu == smp_processor_id());
    if (can_access_pmu) {
        /*
         * Mark the PMU as not owned
         * This will cause the interrupt handler to do nothing in case an overflow
         * interrupt was in-flight
         * This also guarantees that pmc0 will contain the final state
         * It virtually gives us full control on overflow processing from that point
         * on.
         */
        SET_PMU_OWNER(NULL, NULL);
        DPRINT(("releasing ownership\n"));

        /*
         * read current overflow status:
         *
         * we are guaranteed to read the final stable state
         */
        ia64_srlz_d();
        pmc0 = ia64_get_pmc(0); /* slow */

        /*
         * reset freeze bit, overflow status information destroyed
         */
        pfm_unfreeze_pmu();
    } else {
        pmc0 = ctx->th_pmcs[0];
        /*
         * clear whatever overflow status bits there were
         */
        ctx->th_pmcs[0] = 0;
    }
    ovfl_val = pmu_conf->ovfl_val;
    /*
     * we save all the used pmds
     * we take care of overflows for counting PMDs
     *
     * XXX: sampling situation is not taken into account here
     */
    mask2 = ctx->ctx_used_pmds[0];

    DPRINT(("is_self=%d ovfl_val=0x%lx mask2=0x%lx\n", is_self, ovfl_val, mask2));

    for (i = 0; mask2; i++, mask2>>=1) {

        /* skip non used pmds */
        if ((mask2 & 0x1) == 0) continue;

        /*
         * can access PMU always true in system wide mode
         */
        val = pmd_val = can_access_pmu ? ia64_get_pmd(i) : ctx->th_pmds[i];

        if (PMD_IS_COUNTING(i)) {
            DPRINT(("[%d] pmd[%d] ctx_pmd=0x%lx hw_pmd=0x%lx\n",
                task_pid_nr(task),
                i,
                ctx->ctx_pmds[i].val,
                val & ovfl_val));

            /*
             * we rebuild the full 64 bit value of the counter
             */
            val = ctx->ctx_pmds[i].val + (val & ovfl_val);

            /*
             * now everything is in ctx_pmds[] and we need
             * to clear the saved context from save_regs() such that
             * pfm_read_pmds() gets the correct value
             */
            pmd_val = 0UL;

            /*
             * take care of overflow inline
             */
            if (pmc0 & (1UL << i)) {
                val += 1 + ovfl_val;
                DPRINT(("[%d] pmd[%d] overflowed\n", task_pid_nr(task), i));
            }
        }

        DPRINT(("[%d] ctx_pmd[%d]=0x%lx  pmd_val=0x%lx\n", task_pid_nr(task), i, val, pmd_val));

        if (is_self) ctx->th_pmds[i] = pmd_val;

        ctx->ctx_pmds[i].val = val;
    }
}

static struct irqaction perfmon_irqaction = {
    .handler = pfm_interrupt_handler,
    .flags   = IRQF_DISABLED,
    .name    = "perfmon"
};

static void
pfm_alt_save_pmu_state(void *data)
{
    struct pt_regs *regs;

    regs = task_pt_regs(current);

    DPRINT(("called\n"));

    /*
     * should not be necessary but
     * let's take not risk
     */
    pfm_clear_psr_up();
    pfm_clear_psr_pp();
    ia64_psr(regs)->pp = 0;

    /*
     * This call is required
     * May cause a spurious interrupt on some processors
     */
    pfm_freeze_pmu();

    ia64_srlz_d();
}

void
pfm_alt_restore_pmu_state(void *data)
{
    struct pt_regs *regs;

    regs = task_pt_regs(current);

    DPRINT(("called\n"));

    /*
     * put PMU back in state expected
     * by perfmon
     */
    pfm_clear_psr_up();
    pfm_clear_psr_pp();
    ia64_psr(regs)->pp = 0;

    /*
     * perfmon runs with PMU unfrozen at all times
     */
    pfm_unfreeze_pmu();

    ia64_srlz_d();
}

int
pfm_install_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
    int ret, i;
    int reserve_cpu;

    /* some sanity checks */
    if (hdl == NULL || hdl->handler == NULL) return -EINVAL;

    /* do the easy test first */
    if (pfm_alt_intr_handler) return -EBUSY;

    /* one at a time in the install or remove, just fail the others */
    if (!spin_trylock(&pfm_alt_install_check)) {
        return -EBUSY;
    }

    /* reserve our session */
    for_each_online_cpu(reserve_cpu) {
        ret = pfm_reserve_session(NULL, 1, reserve_cpu);
        if (ret) goto cleanup_reserve;
    }

    /* save the current system wide pmu states */
    ret = on_each_cpu(pfm_alt_save_pmu_state, NULL, 1);
    if (ret) {
        DPRINT(("on_each_cpu() failed: %d\n", ret));
        goto cleanup_reserve;
    }

    /* officially change to the alternate interrupt handler */
    pfm_alt_intr_handler = hdl;

    spin_unlock(&pfm_alt_install_check);

    return 0;

cleanup_reserve:
    for_each_online_cpu(i) {
        /* don't unreserve more than we reserved */
        if (i >= reserve_cpu) break;

        pfm_unreserve_session(NULL, 1, i);
    }

    spin_unlock(&pfm_alt_install_check);

    return ret;
}
EXPORT_SYMBOL_GPL(pfm_install_alt_pmu_interrupt);

int
pfm_remove_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
    int i;
    int ret;

    if (hdl == NULL) return -EINVAL;

    /* cannot remove someone else's handler! */
    if (pfm_alt_intr_handler != hdl) return -EINVAL;

    /* one at a time in the install or remove, just fail the others */
    if (!spin_trylock(&pfm_alt_install_check)) {
        return -EBUSY;
    }

    pfm_alt_intr_handler = NULL;

    ret = on_each_cpu(pfm_alt_restore_pmu_state, NULL, 1);
    if (ret) {
        DPRINT(("on_each_cpu() failed: %d\n", ret));
    }

    for_each_online_cpu(i) {
        pfm_unreserve_session(NULL, 1, i);
    }

    spin_unlock(&pfm_alt_install_check);

    return 0;
}
EXPORT_SYMBOL_GPL(pfm_remove_alt_pmu_interrupt);

/*
 * perfmon initialization routine, called from the initcall() table
 */
static int init_pfm_fs(void);

static int __init
pfm_probe_pmu(void)
{
    pmu_config_t **p;
    int family;

    family = local_cpu_data->family;
    p      = pmu_confs;

    while(*p) {
        if ((*p)->probe) {
            if ((*p)->probe() == 0) goto found;
        } else if ((*p)->pmu_family == family || (*p)->pmu_family == 0xff) {
            goto found;
        }
        p++;
    }
    return -1;
found:
    pmu_conf = *p;
    return 0;
}

static const struct file_operations pfm_proc_fops = {
    .open       = pfm_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

int __init
pfm_init(void)
{
    unsigned int n, n_counters, i;

    printk("perfmon: version %u.%u IRQ %u\n",
        PFM_VERSION_MAJ,
        PFM_VERSION_MIN,
        IA64_PERFMON_VECTOR);

    if (pfm_probe_pmu()) {
        printk(KERN_INFO "perfmon: disabled, there is no support for processor family %d\n", 
                local_cpu_data->family);
        return -ENODEV;
    }

    /*
     * compute the number of implemented PMD/PMC from the
     * description tables
     */
    n = 0;
    for (i=0; PMC_IS_LAST(i) == 0;  i++) {
        if (PMC_IS_IMPL(i) == 0) continue;
        pmu_conf->impl_pmcs[i>>6] |= 1UL << (i&63);
        n++;
    }
    pmu_conf->num_pmcs = n;

    n = 0; n_counters = 0;
    for (i=0; PMD_IS_LAST(i) == 0;  i++) {
        if (PMD_IS_IMPL(i) == 0) continue;
        pmu_conf->impl_pmds[i>>6] |= 1UL << (i&63);
        n++;
        if (PMD_IS_COUNTING(i)) n_counters++;
    }
    pmu_conf->num_pmds      = n;
    pmu_conf->num_counters  = n_counters;

    /*
     * sanity checks on the number of debug registers
     */
    if (pmu_conf->use_rr_dbregs) {
        if (pmu_conf->num_ibrs > IA64_NUM_DBG_REGS) {
            printk(KERN_INFO "perfmon: unsupported number of code debug registers (%u)\n", pmu_conf->num_ibrs);
            pmu_conf = NULL;
            return -1;
        }
        if (pmu_conf->num_dbrs > IA64_NUM_DBG_REGS) {
            printk(KERN_INFO "perfmon: unsupported number of data debug registers (%u)\n", pmu_conf->num_ibrs);
            pmu_conf = NULL;
            return -1;
        }
    }

    printk("perfmon: %s PMU detected, %u PMCs, %u PMDs, %u counters (%lu bits)\n",
           pmu_conf->pmu_name,
           pmu_conf->num_pmcs,
           pmu_conf->num_pmds,
           pmu_conf->num_counters,
           ffz(pmu_conf->ovfl_val));

    /* sanity check */
    if (pmu_conf->num_pmds >= PFM_NUM_PMD_REGS || pmu_conf->num_pmcs >= PFM_NUM_PMC_REGS) {
        printk(KERN_ERR "perfmon: not enough pmc/pmd, perfmon disabled\n");
        pmu_conf = NULL;
        return -1;
    }

    /*
     * create /proc/perfmon (mostly for debugging purposes)
     */
    perfmon_dir = proc_create("perfmon", S_IRUGO, NULL, &pfm_proc_fops);
    if (perfmon_dir == NULL) {
        printk(KERN_ERR "perfmon: cannot create /proc entry, perfmon disabled\n");
        pmu_conf = NULL;
        return -1;
    }

    /*
     * create /proc/sys/kernel/perfmon (for debugging purposes)
     */
    pfm_sysctl_header = register_sysctl_table(pfm_sysctl_root);

    /*
     * initialize all our spinlocks
     */
    spin_lock_init(&pfm_sessions.pfs_lock);
    spin_lock_init(&pfm_buffer_fmt_lock);

    init_pfm_fs();

    for(i=0; i < NR_CPUS; i++) pfm_stats[i].pfm_ovfl_intr_cycles_min = ~0UL;

    return 0;
}

__initcall(pfm_init);

/*
 * this function is called before pfm_init()
 */
void
pfm_init_percpu (void)
{
    static int first_time=1;
    /*
     * make sure no measurement is active
     * (may inherit programmed PMCs from EFI).
     */
    pfm_clear_psr_pp();
    pfm_clear_psr_up();

    /*
     * we run with the PMU not frozen at all times
     */
    pfm_unfreeze_pmu();

    if (first_time) {
        register_percpu_irq(IA64_PERFMON_VECTOR, &perfmon_irqaction);
        first_time=0;
    }

    ia64_setreg(_IA64_REG_CR_PMV, IA64_PERFMON_VECTOR);
    ia64_srlz_d();
}

/*
 * used for debug purposes only
 */
void
dump_pmu_state(const char *from)
{
    struct task_struct *task;
    struct pt_regs *regs;
    pfm_context_t *ctx;
    unsigned long psr, dcr, info, flags;
    int i, this_cpu;

    local_irq_save(flags);

    this_cpu = smp_processor_id();
    regs     = task_pt_regs(current);
    info     = PFM_CPUINFO_GET();
    dcr      = ia64_getreg(_IA64_REG_CR_DCR);

    if (info == 0 && ia64_psr(regs)->pp == 0 && (dcr & IA64_DCR_PP) == 0) {
        local_irq_restore(flags);
        return;
    }

    printk("CPU%d from %s() current [%d] iip=0x%lx %s\n", 
        this_cpu, 
        from, 
        task_pid_nr(current),
        regs->cr_iip,
        current->comm);

    task = GET_PMU_OWNER();
    ctx  = GET_PMU_CTX();

    printk("->CPU%d owner [%d] ctx=%p\n", this_cpu, task ? task_pid_nr(task) : -1, ctx);

    psr = pfm_get_psr();

    printk("->CPU%d pmc0=0x%lx psr.pp=%d psr.up=%d dcr.pp=%d syst_info=0x%lx user_psr.up=%d user_psr.pp=%d\n", 
        this_cpu,
        ia64_get_pmc(0),
        psr & IA64_PSR_PP ? 1 : 0,
        psr & IA64_PSR_UP ? 1 : 0,
        dcr & IA64_DCR_PP ? 1 : 0,
        info,
        ia64_psr(regs)->up,
        ia64_psr(regs)->pp);

    ia64_psr(regs)->up = 0;
    ia64_psr(regs)->pp = 0;

    for (i=1; PMC_IS_LAST(i) == 0; i++) {
        if (PMC_IS_IMPL(i) == 0) continue;
        printk("->CPU%d pmc[%d]=0x%lx thread_pmc[%d]=0x%lx\n", this_cpu, i, ia64_get_pmc(i), i, ctx->th_pmcs[i]);
    }

    for (i=1; PMD_IS_LAST(i) == 0; i++) {
        if (PMD_IS_IMPL(i) == 0) continue;
        printk("->CPU%d pmd[%d]=0x%lx thread_pmd[%d]=0x%lx\n", this_cpu, i, ia64_get_pmd(i), i, ctx->th_pmds[i]);
    }

    if (ctx) {
        printk("->CPU%d ctx_state=%d vaddr=%p addr=%p fd=%d ctx_task=[%d] saved_psr_up=0x%lx\n",
                this_cpu,
                ctx->ctx_state,
                ctx->ctx_smpl_vaddr,
                ctx->ctx_smpl_hdr,
                ctx->ctx_msgq_head,
                ctx->ctx_msgq_tail,
                ctx->ctx_saved_psr_up);
    }
    local_irq_restore(flags);
}

/*
 * called from process.c:copy_thread(). task is new child.
 */
void
pfm_inherit(struct task_struct *task, struct pt_regs *regs)
{
    struct thread_struct *thread;

    DPRINT(("perfmon: pfm_inherit clearing state for [%d]\n", task_pid_nr(task)));

    thread = &task->thread;

    /*
     * cut links inherited from parent (current)
     */
    thread->pfm_context = NULL;

    PFM_SET_WORK_PENDING(task, 0);

    /*
     * the psr bits are already set properly in copy_threads()
     */
}
#else  /* !CONFIG_PERFMON */
asmlinkage long
sys_perfmonctl (int fd, int cmd, void *arg, int count)
{
    return -ENOSYS;
}
#endif /* CONFIG_PERFMON */