linux-stable/kernel/trace/trace_events_hist.c

// SPDX-License-Identifier: GPL-2.0
/*
 * trace_events_hist - trace event hist triggers
 *
 * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/security.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/rculist.h>
#include <linux/tracefs.h>

/* for gfp flag names */
#include <linux/trace_events.h>
#include <trace/events/mmflags.h>

#include "tracing_map.h"
#include "trace_synth.h"

#define ERRORS								\
	C(NONE,			"No error"),				\
	C(DUPLICATE_VAR,	"Variable already defined"),		\
	C(VAR_NOT_UNIQUE,	"Variable name not unique, need to use fully qualified name (subsys.event.var) for variable"), \
	C(TOO_MANY_VARS,	"Too many variables defined"),		\
	C(MALFORMED_ASSIGNMENT,	"Malformed assignment"),		\
	C(NAMED_MISMATCH,	"Named hist trigger doesn't match existing named trigger (includes variables)"), \
	C(TRIGGER_EEXIST,	"Hist trigger already exists"),		\
	C(TRIGGER_ENOENT_CLEAR,	"Can't clear or continue a nonexistent hist trigger"), \
	C(SET_CLOCK_FAIL,	"Couldn't set trace_clock"),		\
	C(BAD_FIELD_MODIFIER,	"Invalid field modifier"),		\
	C(TOO_MANY_SUBEXPR,	"Too many subexpressions (3 max)"),	\
	C(TIMESTAMP_MISMATCH,	"Timestamp units in expression don't match"), \
	C(TOO_MANY_FIELD_VARS,	"Too many field variables defined"),	\
	C(EVENT_FILE_NOT_FOUND,	"Event file not found"),		\
	C(HIST_NOT_FOUND,	"Matching event histogram not found"),	\
	C(HIST_CREATE_FAIL,	"Couldn't create histogram for field"),	\
	C(SYNTH_VAR_NOT_FOUND,	"Couldn't find synthetic variable"),	\
	C(SYNTH_EVENT_NOT_FOUND,"Couldn't find synthetic event"),	\
	C(SYNTH_TYPE_MISMATCH,	"Param type doesn't match synthetic event field type"), \
	C(SYNTH_COUNT_MISMATCH,	"Param count doesn't match synthetic event field count"), \
	C(FIELD_VAR_PARSE_FAIL,	"Couldn't parse field variable"),	\
	C(VAR_CREATE_FIND_FAIL,	"Couldn't create or find variable"),	\
	C(ONX_NOT_VAR,		"For onmax(x) or onchange(x), x must be a variable"), \
	C(ONX_VAR_NOT_FOUND,	"Couldn't find onmax or onchange variable"), \
	C(ONX_VAR_CREATE_FAIL,	"Couldn't create onmax or onchange variable"), \
	C(FIELD_VAR_CREATE_FAIL,"Couldn't create field variable"),	\
	C(TOO_MANY_PARAMS,	"Too many action params"),		\
	C(PARAM_NOT_FOUND,	"Couldn't find param"),			\
	C(INVALID_PARAM,	"Invalid action param"),		\
	C(ACTION_NOT_FOUND,	"No action found"),			\
	C(NO_SAVE_PARAMS,	"No params found for save()"),		\
	C(TOO_MANY_SAVE_ACTIONS,"Can't have more than one save() action per hist"), \
	C(ACTION_MISMATCH,	"Handler doesn't support action"),	\
	C(NO_CLOSING_PAREN,	"No closing paren found"),		\
	C(SUBSYS_NOT_FOUND,	"Missing subsystem"),			\
	C(INVALID_SUBSYS_EVENT,	"Invalid subsystem or event name"),	\
	C(INVALID_REF_KEY,	"Using variable references in keys not supported"), \
	C(VAR_NOT_FOUND,	"Couldn't find variable"),		\
	C(FIELD_NOT_FOUND,	"Couldn't find field"),			\
	C(EMPTY_ASSIGNMENT,	"Empty assignment"),			\
	C(INVALID_SORT_MODIFIER,"Invalid sort modifier"),		\
	C(EMPTY_SORT_FIELD,	"Empty sort field"),			\
	C(TOO_MANY_SORT_FIELDS,	"Too many sort fields (Max = 2)"),	\
	C(INVALID_SORT_FIELD,	"Sort field must be a key or a val"),	\
	C(INVALID_STR_OPERAND,	"String type can not be an operand in expression"), \
	C(EXPECT_NUMBER,	"Expecting numeric literal"),		\
	C(UNARY_MINUS_SUBEXPR,	"Unary minus not supported in sub-expressions"), \
	C(DIVISION_BY_ZERO,	"Division by zero"),			\
	C(NEED_NOHC_VAL,	"Non-hitcount value is required for 'nohitcount'"),

#undef C
#define C(a, b)		HIST_ERR_##a

enum { ERRORS };

#undef C
#define C(a, b)		b

static const char *err_text[] = { ERRORS };

struct hist_field;

typedef u64 (*hist_field_fn_t) (struct hist_field *field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event);

#define HIST_FIELD_OPERANDS_MAX	2
#define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
#define HIST_ACTIONS_MAX	8
#define HIST_CONST_DIGITS_MAX	21
#define HIST_DIV_SHIFT		20  /* For optimizing division by constants */

enum field_op_id {
	FIELD_OP_NONE,
	FIELD_OP_PLUS,
	FIELD_OP_MINUS,
	FIELD_OP_UNARY_MINUS,
	FIELD_OP_DIV,
	FIELD_OP_MULT,
};

enum hist_field_fn {
	HIST_FIELD_FN_NOP,
	HIST_FIELD_FN_VAR_REF,
	HIST_FIELD_FN_COUNTER,
	HIST_FIELD_FN_CONST,
	HIST_FIELD_FN_LOG2,
	HIST_FIELD_FN_BUCKET,
	HIST_FIELD_FN_TIMESTAMP,
	HIST_FIELD_FN_CPU,
	HIST_FIELD_FN_STRING,
	HIST_FIELD_FN_DYNSTRING,
	HIST_FIELD_FN_RELDYNSTRING,
	HIST_FIELD_FN_PSTRING,
	HIST_FIELD_FN_S64,
	HIST_FIELD_FN_U64,
	HIST_FIELD_FN_S32,
	HIST_FIELD_FN_U32,
	HIST_FIELD_FN_S16,
	HIST_FIELD_FN_U16,
	HIST_FIELD_FN_S8,
	HIST_FIELD_FN_U8,
	HIST_FIELD_FN_UMINUS,
	HIST_FIELD_FN_MINUS,
	HIST_FIELD_FN_PLUS,
	HIST_FIELD_FN_DIV,
	HIST_FIELD_FN_MULT,
	HIST_FIELD_FN_DIV_POWER2,
	HIST_FIELD_FN_DIV_NOT_POWER2,
	HIST_FIELD_FN_DIV_MULT_SHIFT,
	HIST_FIELD_FN_EXECNAME,
	HIST_FIELD_FN_STACK,
};

/*
 * A hist_var (histogram variable) contains variable information for
 * hist_fields having the HIST_FIELD_FL_VAR or HIST_FIELD_FL_VAR_REF
 * flag set.  A hist_var has a variable name e.g. ts0, and is
 * associated with a given histogram trigger, as specified by
 * hist_data.  The hist_var idx is the unique index assigned to the
 * variable by the hist trigger's tracing_map.  The idx is what is
 * used to set a variable's value and, by a variable reference, to
 * retrieve it.
 */
struct hist_var {
	char				*name;
	struct hist_trigger_data	*hist_data;
	unsigned int			idx;
};

struct hist_field {
	struct ftrace_event_field	*field;
	unsigned long			flags;
	unsigned long			buckets;
	const char			*type;
	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
	struct hist_trigger_data	*hist_data;
	enum hist_field_fn		fn_num;
	unsigned int			ref;
	unsigned int			size;
	unsigned int			offset;
	unsigned int                    is_signed;

	/*
	 * Variable fields contain variable-specific info in var.
	 */
	struct hist_var			var;
	enum field_op_id		operator;
	char				*system;
	char				*event_name;

	/*
	 * The name field is used for EXPR and VAR_REF fields.  VAR
	 * fields contain the variable name in var.name.
	 */
	char				*name;

	/*
	 * When a histogram trigger is hit, if it has any references
	 * to variables, the values of those variables are collected
	 * into a var_ref_vals array by resolve_var_refs().  The
	 * current value of each variable is read from the tracing_map
	 * using the hist field's hist_var.idx and entered into the
	 * var_ref_idx entry i.e. var_ref_vals[var_ref_idx].
	 */
	unsigned int			var_ref_idx;
	bool                            read_once;

	unsigned int			var_str_idx;

	/* Numeric literals are represented as u64 */
	u64				constant;
	/* Used to optimize division by constants */
	u64				div_multiplier;
};

static u64 hist_fn_call(struct hist_field *hist_field,
			struct tracing_map_elt *elt,
			struct trace_buffer *buffer,
			struct ring_buffer_event *rbe,
			void *event);

static u64 hist_field_const(struct hist_field *field,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer,
			   struct ring_buffer_event *rbe,
			   void *event)
{
	return field->constant;
}

static u64 hist_field_counter(struct hist_field *field,
			      struct tracing_map_elt *elt,
			      struct trace_buffer *buffer,
			      struct ring_buffer_event *rbe,
			      void *event)
{
	return 1;
}

static u64 hist_field_string(struct hist_field *hist_field,
			     struct tracing_map_elt *elt,
			     struct trace_buffer *buffer,
			     struct ring_buffer_event *rbe,
			     void *event)
{
	char *addr = (char *)(event + hist_field->field->offset);

	return (u64)(unsigned long)addr;
}

static u64 hist_field_dynstring(struct hist_field *hist_field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event)
{
	u32 str_item = *(u32 *)(event + hist_field->field->offset);
	int str_loc = str_item & 0xffff;
	char *addr = (char *)(event + str_loc);

	return (u64)(unsigned long)addr;
}

static u64 hist_field_reldynstring(struct hist_field *hist_field,
				   struct tracing_map_elt *elt,
				   struct trace_buffer *buffer,
				   struct ring_buffer_event *rbe,
				   void *event)
{
	u32 *item = event + hist_field->field->offset;
	u32 str_item = *item;
	int str_loc = str_item & 0xffff;
	char *addr = (char *)&item[1] + str_loc;

	return (u64)(unsigned long)addr;
}

static u64 hist_field_pstring(struct hist_field *hist_field,
			      struct tracing_map_elt *elt,
			      struct trace_buffer *buffer,
			      struct ring_buffer_event *rbe,
			      void *event)
{
	char **addr = (char **)(event + hist_field->field->offset);

	return (u64)(unsigned long)*addr;
}

static u64 hist_field_log2(struct hist_field *hist_field,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer,
			   struct ring_buffer_event *rbe,
			   void *event)
{
	struct hist_field *operand = hist_field->operands[0];

	u64 val = hist_fn_call(operand, elt, buffer, rbe, event);

	return (u64) ilog2(roundup_pow_of_two(val));
}

static u64 hist_field_bucket(struct hist_field *hist_field,
			     struct tracing_map_elt *elt,
			     struct trace_buffer *buffer,
			     struct ring_buffer_event *rbe,
			     void *event)
{
	struct hist_field *operand = hist_field->operands[0];
	unsigned long buckets = hist_field->buckets;

	u64 val = hist_fn_call(operand, elt, buffer, rbe, event);

	if (WARN_ON_ONCE(!buckets))
		return val;

	if (val >= LONG_MAX)
		val = div64_ul(val, buckets);
	else
		val = (u64)((unsigned long)val / buckets);
	return val * buckets;
}

static u64 hist_field_plus(struct hist_field *hist_field,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer,
			   struct ring_buffer_event *rbe,
			   void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);
	u64 val2 = hist_fn_call(operand2, elt, buffer, rbe, event);

	return val1 + val2;
}

static u64 hist_field_minus(struct hist_field *hist_field,
			    struct tracing_map_elt *elt,
			    struct trace_buffer *buffer,
			    struct ring_buffer_event *rbe,
			    void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);
	u64 val2 = hist_fn_call(operand2, elt, buffer, rbe, event);

	return val1 - val2;
}

static u64 hist_field_div(struct hist_field *hist_field,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer,
			   struct ring_buffer_event *rbe,
			   void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);
	u64 val2 = hist_fn_call(operand2, elt, buffer, rbe, event);

	/* Return -1 for the undefined case */
	if (!val2)
		return -1;

	/* Use shift if the divisor is a power of 2 */
	if (!(val2 & (val2 - 1)))
		return val1 >> __ffs64(val2);

	return div64_u64(val1, val2);
}

static u64 div_by_power_of_two(struct hist_field *hist_field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);

	return val1 >> __ffs64(operand2->constant);
}

static u64 div_by_not_power_of_two(struct hist_field *hist_field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);

	return div64_u64(val1, operand2->constant);
}

static u64 div_by_mult_and_shift(struct hist_field *hist_field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);

	/*
	 * If the divisor is a constant, do a multiplication and shift instead.
	 *
	 * Choose Z = some power of 2. If Y <= Z, then:
	 *     X / Y = (X * (Z / Y)) / Z
	 *
	 * (Z / Y) is a constant (mult) which is calculated at parse time, so:
	 *     X / Y = (X * mult) / Z
	 *
	 * The division by Z can be replaced by a shift since Z is a power of 2:
	 *     X / Y = (X * mult) >> HIST_DIV_SHIFT
	 *
	 * As long, as X < Z the results will not be off by more than 1.
	 */
	if (val1 < (1 << HIST_DIV_SHIFT)) {
		u64 mult = operand2->div_multiplier;

		return (val1 * mult + ((1 << HIST_DIV_SHIFT) - 1)) >> HIST_DIV_SHIFT;
	}

	return div64_u64(val1, operand2->constant);
}

static u64 hist_field_mult(struct hist_field *hist_field,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer,
			   struct ring_buffer_event *rbe,
			   void *event)
{
	struct hist_field *operand1 = hist_field->operands[0];
	struct hist_field *operand2 = hist_field->operands[1];

	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);
	u64 val2 = hist_fn_call(operand2, elt, buffer, rbe, event);

	return val1 * val2;
}

static u64 hist_field_unary_minus(struct hist_field *hist_field,
				  struct tracing_map_elt *elt,
				  struct trace_buffer *buffer,
				  struct ring_buffer_event *rbe,
				  void *event)
{
	struct hist_field *operand = hist_field->operands[0];

	s64 sval = (s64)hist_fn_call(operand, elt, buffer, rbe, event);
	u64 val = (u64)-sval;

	return val;
}

#define DEFINE_HIST_FIELD_FN(type)					\
	static u64 hist_field_##type(struct hist_field *hist_field,	\
				     struct tracing_map_elt *elt,	\
				     struct trace_buffer *buffer,	\
				     struct ring_buffer_event *rbe,	\
				     void *event)			\
{									\
	type *addr = (type *)(event + hist_field->field->offset);	\
									\
	return (u64)(unsigned long)*addr;				\
}

DEFINE_HIST_FIELD_FN(s64);
DEFINE_HIST_FIELD_FN(u64);
DEFINE_HIST_FIELD_FN(s32);
DEFINE_HIST_FIELD_FN(u32);
DEFINE_HIST_FIELD_FN(s16);
DEFINE_HIST_FIELD_FN(u16);
DEFINE_HIST_FIELD_FN(s8);
DEFINE_HIST_FIELD_FN(u8);

#define for_each_hist_field(i, hist_data)	\
	for ((i) = 0; (i) < (hist_data)->n_fields; (i)++)

#define for_each_hist_val_field(i, hist_data)	\
	for ((i) = 0; (i) < (hist_data)->n_vals; (i)++)

#define for_each_hist_key_field(i, hist_data)	\
	for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)

#define HITCOUNT_IDX		0
#define HIST_KEY_SIZE_MAX	(MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)

enum hist_field_flags {
	HIST_FIELD_FL_HITCOUNT		= 1 << 0,
	HIST_FIELD_FL_KEY		= 1 << 1,
	HIST_FIELD_FL_STRING		= 1 << 2,
	HIST_FIELD_FL_HEX		= 1 << 3,
	HIST_FIELD_FL_SYM		= 1 << 4,
	HIST_FIELD_FL_SYM_OFFSET	= 1 << 5,
	HIST_FIELD_FL_EXECNAME		= 1 << 6,
	HIST_FIELD_FL_SYSCALL		= 1 << 7,
	HIST_FIELD_FL_STACKTRACE	= 1 << 8,
	HIST_FIELD_FL_LOG2		= 1 << 9,
	HIST_FIELD_FL_TIMESTAMP		= 1 << 10,
	HIST_FIELD_FL_TIMESTAMP_USECS	= 1 << 11,
	HIST_FIELD_FL_VAR		= 1 << 12,
	HIST_FIELD_FL_EXPR		= 1 << 13,
	HIST_FIELD_FL_VAR_REF		= 1 << 14,
	HIST_FIELD_FL_CPU		= 1 << 15,
	HIST_FIELD_FL_ALIAS		= 1 << 16,
	HIST_FIELD_FL_BUCKET		= 1 << 17,
	HIST_FIELD_FL_CONST		= 1 << 18,
	HIST_FIELD_FL_PERCENT		= 1 << 19,
	HIST_FIELD_FL_GRAPH		= 1 << 20,
};

struct var_defs {
	unsigned int	n_vars;
	char		*name[TRACING_MAP_VARS_MAX];
	char		*expr[TRACING_MAP_VARS_MAX];
};

struct hist_trigger_attrs {
	char		*keys_str;
	char		*vals_str;
	char		*sort_key_str;
	char		*name;
	char		*clock;
	bool		pause;
	bool		cont;
	bool		clear;
	bool		ts_in_usecs;
	bool		no_hitcount;
	unsigned int	map_bits;

	char		*assignment_str[TRACING_MAP_VARS_MAX];
	unsigned int	n_assignments;

	char		*action_str[HIST_ACTIONS_MAX];
	unsigned int	n_actions;

	struct var_defs	var_defs;
};

struct field_var {
	struct hist_field	*var;
	struct hist_field	*val;
};

struct field_var_hist {
	struct hist_trigger_data	*hist_data;
	char				*cmd;
};

struct hist_trigger_data {
	struct hist_field               *fields[HIST_FIELDS_MAX];
	unsigned int			n_vals;
	unsigned int			n_keys;
	unsigned int			n_fields;
	unsigned int			n_vars;
	unsigned int			n_var_str;
	unsigned int			key_size;
	struct tracing_map_sort_key	sort_keys[TRACING_MAP_SORT_KEYS_MAX];
	unsigned int			n_sort_keys;
	struct trace_event_file		*event_file;
	struct hist_trigger_attrs	*attrs;
	struct tracing_map		*map;
	bool				enable_timestamps;
	bool				remove;
	struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
	unsigned int			n_var_refs;

	struct action_data		*actions[HIST_ACTIONS_MAX];
	unsigned int			n_actions;

	struct field_var		*field_vars[SYNTH_FIELDS_MAX];
	unsigned int			n_field_vars;
	unsigned int			n_field_var_str;
	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
	unsigned int			n_field_var_hists;

	struct field_var		*save_vars[SYNTH_FIELDS_MAX];
	unsigned int			n_save_vars;
	unsigned int			n_save_var_str;
};

struct action_data;

typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
			     struct tracing_map_elt *elt,
			     struct trace_buffer *buffer, void *rec,
			     struct ring_buffer_event *rbe, void *key,
			     struct action_data *data, u64 *var_ref_vals);

typedef bool (*check_track_val_fn_t) (u64 track_val, u64 var_val);

enum handler_id {
	HANDLER_ONMATCH = 1,
	HANDLER_ONMAX,
	HANDLER_ONCHANGE,
};

enum action_id {
	ACTION_SAVE = 1,
	ACTION_TRACE,
	ACTION_SNAPSHOT,
};

struct action_data {
	enum handler_id		handler;
	enum action_id		action;
	char			*action_name;
	action_fn_t		fn;

	unsigned int		n_params;
	char			*params[SYNTH_FIELDS_MAX];

	/*
	 * When a histogram trigger is hit, the values of any
	 * references to variables, including variables being passed
	 * as parameters to synthetic events, are collected into a
	 * var_ref_vals array.  This var_ref_idx array is an array of
	 * indices into the var_ref_vals array, one for each synthetic
	 * event param, and is passed to the synthetic event
	 * invocation.
	 */
	unsigned int		var_ref_idx[SYNTH_FIELDS_MAX];
	struct synth_event	*synth_event;
	bool			use_trace_keyword;
	char			*synth_event_name;

	union {
		struct {
			char			*event;
			char			*event_system;
		} match_data;

		struct {
			/*
			 * var_str contains the $-unstripped variable
			 * name referenced by var_ref, and used when
			 * printing the action.  Because var_ref
			 * creation is deferred to create_actions(),
			 * we need a per-action way to save it until
			 * then, thus var_str.
			 */
			char			*var_str;

			/*
			 * var_ref refers to the variable being
			 * tracked e.g onmax($var).
			 */
			struct hist_field	*var_ref;

			/*
			 * track_var contains the 'invisible' tracking
			 * variable created to keep the current
			 * e.g. max value.
			 */
			struct hist_field	*track_var;

			check_track_val_fn_t	check_val;
			action_fn_t		save_data;
		} track_data;
	};
};

struct track_data {
	u64				track_val;
	bool				updated;

	unsigned int			key_len;
	void				*key;
	struct tracing_map_elt		elt;

	struct action_data		*action_data;
	struct hist_trigger_data	*hist_data;
};

struct hist_elt_data {
	char *comm;
	u64 *var_ref_vals;
	char **field_var_str;
	int n_field_var_str;
};

struct snapshot_context {
	struct tracing_map_elt	*elt;
	void			*key;
};

/*
 * Returns the specific division function to use if the divisor
 * is constant. This avoids extra branches when the trigger is hit.
 */
static enum hist_field_fn hist_field_get_div_fn(struct hist_field *divisor)
{
	u64 div = divisor->constant;

	if (!(div & (div - 1)))
		return HIST_FIELD_FN_DIV_POWER2;

	/* If the divisor is too large, do a regular division */
	if (div > (1 << HIST_DIV_SHIFT))
		return HIST_FIELD_FN_DIV_NOT_POWER2;

	divisor->div_multiplier = div64_u64((u64)(1 << HIST_DIV_SHIFT), div);
	return HIST_FIELD_FN_DIV_MULT_SHIFT;
}

static void track_data_free(struct track_data *track_data)
{
	struct hist_elt_data *elt_data;

	if (!track_data)
		return;

	kfree(track_data->key);

	elt_data = track_data->elt.private_data;
	if (elt_data) {
		kfree(elt_data->comm);
		kfree(elt_data);
	}

	kfree(track_data);
}

static struct track_data *track_data_alloc(unsigned int key_len,
					   struct action_data *action_data,
					   struct hist_trigger_data *hist_data)
{
	struct track_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
	struct hist_elt_data *elt_data;

	if (!data)
		return ERR_PTR(-ENOMEM);

	data->key = kzalloc(key_len, GFP_KERNEL);
	if (!data->key) {
		track_data_free(data);
		return ERR_PTR(-ENOMEM);
	}

	data->key_len = key_len;
	data->action_data = action_data;
	data->hist_data = hist_data;

	elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
	if (!elt_data) {
		track_data_free(data);
		return ERR_PTR(-ENOMEM);
	}

	data->elt.private_data = elt_data;

	elt_data->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
	if (!elt_data->comm) {
		track_data_free(data);
		return ERR_PTR(-ENOMEM);
	}

	return data;
}

#define HIST_PREFIX "hist:"

static char *last_cmd;
static char last_cmd_loc[MAX_FILTER_STR_VAL];

static int errpos(char *str)
{
	if (!str || !last_cmd)
		return 0;

	return err_pos(last_cmd, str);
}

static void last_cmd_set(struct trace_event_file *file, char *str)
{
	const char *system = NULL, *name = NULL;
	struct trace_event_call *call;
	int len;

	if (!str)
		return;

	/* sizeof() contains the nul byte */
	len = sizeof(HIST_PREFIX) + strlen(str);
	kfree(last_cmd);
	last_cmd = kzalloc(len, GFP_KERNEL);
	if (!last_cmd)
		return;

	strcpy(last_cmd, HIST_PREFIX);
	/* Again, sizeof() contains the nul byte */
	len -= sizeof(HIST_PREFIX);
	strncat(last_cmd, str, len);

	if (file) {
		call = file->event_call;
		system = call->class->system;
		if (system) {
			name = trace_event_name(call);
			if (!name)
				system = NULL;
		}
	}

	if (system)
		snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, HIST_PREFIX "%s:%s", system, name);
}

static void hist_err(struct trace_array *tr, u8 err_type, u16 err_pos)
{
	if (!last_cmd)
		return;

	tracing_log_err(tr, last_cmd_loc, last_cmd, err_text,
			err_type, err_pos);
}

static void hist_err_clear(void)
{
	if (last_cmd)
		last_cmd[0] = '\0';
	last_cmd_loc[0] = '\0';
}

typedef void (*synth_probe_func_t) (void *__data, u64 *var_ref_vals,
				    unsigned int *var_ref_idx);

static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
			       unsigned int *var_ref_idx)
{
	struct tracepoint *tp = event->tp;

	if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
		struct tracepoint_func *probe_func_ptr;
		synth_probe_func_t probe_func;
		void *__data;

		if (!(cpu_online(raw_smp_processor_id())))
			return;

		probe_func_ptr = rcu_dereference_sched((tp)->funcs);
		if (probe_func_ptr) {
			do {
				probe_func = probe_func_ptr->func;
				__data = probe_func_ptr->data;
				probe_func(__data, var_ref_vals, var_ref_idx);
			} while ((++probe_func_ptr)->func);
		}
	}
}

static void action_trace(struct hist_trigger_data *hist_data,
			 struct tracing_map_elt *elt,
			 struct trace_buffer *buffer, void *rec,
			 struct ring_buffer_event *rbe, void *key,
			 struct action_data *data, u64 *var_ref_vals)
{
	struct synth_event *event = data->synth_event;

	trace_synth(event, var_ref_vals, data->var_ref_idx);
}

struct hist_var_data {
	struct list_head list;
	struct hist_trigger_data *hist_data;
};

static u64 hist_field_timestamp(struct hist_field *hist_field,
				struct tracing_map_elt *elt,
				struct trace_buffer *buffer,
				struct ring_buffer_event *rbe,
				void *event)
{
	struct hist_trigger_data *hist_data = hist_field->hist_data;
	struct trace_array *tr = hist_data->event_file->tr;

	u64 ts = ring_buffer_event_time_stamp(buffer, rbe);

	if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))
		ts = ns2usecs(ts);

	return ts;
}

static u64 hist_field_cpu(struct hist_field *hist_field,
			  struct tracing_map_elt *elt,
			  struct trace_buffer *buffer,
			  struct ring_buffer_event *rbe,
			  void *event)
{
	int cpu = smp_processor_id();

	return cpu;
}

/**
 * check_field_for_var_ref - Check if a VAR_REF field references a variable
 * @hist_field: The VAR_REF field to check
 * @var_data: The hist trigger that owns the variable
 * @var_idx: The trigger variable identifier
 *
 * Check the given VAR_REF field to see whether or not it references
 * the given variable associated with the given trigger.
 *
 * Return: The VAR_REF field if it does reference the variable, NULL if not
 */
static struct hist_field *
check_field_for_var_ref(struct hist_field *hist_field,
			struct hist_trigger_data *var_data,
			unsigned int var_idx)
{
	WARN_ON(!(hist_field && hist_field->flags & HIST_FIELD_FL_VAR_REF));

	if (hist_field && hist_field->var.idx == var_idx &&
	    hist_field->var.hist_data == var_data)
		return hist_field;

	return NULL;
}

/**
 * find_var_ref - Check if a trigger has a reference to a trigger variable
 * @hist_data: The hist trigger that might have a reference to the variable
 * @var_data: The hist trigger that owns the variable
 * @var_idx: The trigger variable identifier
 *
 * Check the list of var_refs[] on the first hist trigger to see
 * whether any of them are references to the variable on the second
 * trigger.
 *
 * Return: The VAR_REF field referencing the variable if so, NULL if not
 */
static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
				       struct hist_trigger_data *var_data,
				       unsigned int var_idx)
{
	struct hist_field *hist_field;
	unsigned int i;

	for (i = 0; i < hist_data->n_var_refs; i++) {
		hist_field = hist_data->var_refs[i];
		if (check_field_for_var_ref(hist_field, var_data, var_idx))
			return hist_field;
	}

	return NULL;
}

/**
 * find_any_var_ref - Check if there is a reference to a given trigger variable
 * @hist_data: The hist trigger
 * @var_idx: The trigger variable identifier
 *
 * Check to see whether the given variable is currently referenced by
 * any other trigger.
 *
 * The trigger the variable is defined on is explicitly excluded - the
 * assumption being that a self-reference doesn't prevent a trigger
 * from being removed.
 *
 * Return: The VAR_REF field referencing the variable if so, NULL if not
 */
static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
					   unsigned int var_idx)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *found = NULL;
	struct hist_var_data *var_data;

	list_for_each_entry(var_data, &tr->hist_vars, list) {
		if (var_data->hist_data == hist_data)
			continue;
		found = find_var_ref(var_data->hist_data, hist_data, var_idx);
		if (found)
			break;
	}

	return found;
}

/**
 * check_var_refs - Check if there is a reference to any of trigger's variables
 * @hist_data: The hist trigger
 *
 * A trigger can define one or more variables.  If any one of them is
 * currently referenced by any other trigger, this function will
 * determine that.
 *
 * Typically used to determine whether or not a trigger can be removed
 * - if there are any references to a trigger's variables, it cannot.
 *
 * Return: True if there is a reference to any of trigger's variables
 */
static bool check_var_refs(struct hist_trigger_data *hist_data)
{
	struct hist_field *field;
	bool found = false;
	int i;

	for_each_hist_field(i, hist_data) {
		field = hist_data->fields[i];
		if (field && field->flags & HIST_FIELD_FL_VAR) {
			if (find_any_var_ref(hist_data, field->var.idx)) {
				found = true;
				break;
			}
		}
	}

	return found;
}

static struct hist_var_data *find_hist_vars(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_var_data *var_data, *found = NULL;

	list_for_each_entry(var_data, &tr->hist_vars, list) {
		if (var_data->hist_data == hist_data) {
			found = var_data;
			break;
		}
	}

	return found;
}

static bool field_has_hist_vars(struct hist_field *hist_field,
				unsigned int level)
{
	int i;

	if (level > 3)
		return false;

	if (!hist_field)
		return false;

	if (hist_field->flags & HIST_FIELD_FL_VAR ||
	    hist_field->flags & HIST_FIELD_FL_VAR_REF)
		return true;

	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++) {
		struct hist_field *operand;

		operand = hist_field->operands[i];
		if (field_has_hist_vars(operand, level + 1))
			return true;
	}

	return false;
}

static bool has_hist_vars(struct hist_trigger_data *hist_data)
{
	struct hist_field *hist_field;
	int i;

	for_each_hist_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		if (field_has_hist_vars(hist_field, 0))
			return true;
	}

	return false;
}

static int save_hist_vars(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_var_data *var_data;

	var_data = find_hist_vars(hist_data);
	if (var_data)
		return 0;

	if (tracing_check_open_get_tr(tr))
		return -ENODEV;

	var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);
	if (!var_data) {
		trace_array_put(tr);
		return -ENOMEM;
	}

	var_data->hist_data = hist_data;
	list_add(&var_data->list, &tr->hist_vars);

	return 0;
}

static void remove_hist_vars(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_var_data *var_data;

	var_data = find_hist_vars(hist_data);
	if (!var_data)
		return;

	if (WARN_ON(check_var_refs(hist_data)))
		return;

	list_del(&var_data->list);

	kfree(var_data);

	trace_array_put(tr);
}

static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
					 const char *var_name)
{
	struct hist_field *hist_field, *found = NULL;
	int i;

	for_each_hist_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
		    strcmp(hist_field->var.name, var_name) == 0) {
			found = hist_field;
			break;
		}
	}

	return found;
}

static struct hist_field *find_var(struct hist_trigger_data *hist_data,
				   struct trace_event_file *file,
				   const char *var_name)
{
	struct hist_trigger_data *test_data;
	struct event_trigger_data *test;
	struct hist_field *hist_field;

	lockdep_assert_held(&event_mutex);

	hist_field = find_var_field(hist_data, var_name);
	if (hist_field)
		return hist_field;

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			test_data = test->private_data;
			hist_field = find_var_field(test_data, var_name);
			if (hist_field)
				return hist_field;
		}
	}

	return NULL;
}

static struct trace_event_file *find_var_file(struct trace_array *tr,
					      char *system,
					      char *event_name,
					      char *var_name)
{
	struct hist_trigger_data *var_hist_data;
	struct hist_var_data *var_data;
	struct trace_event_file *file, *found = NULL;

	if (system)
		return find_event_file(tr, system, event_name);

	list_for_each_entry(var_data, &tr->hist_vars, list) {
		var_hist_data = var_data->hist_data;
		file = var_hist_data->event_file;
		if (file == found)
			continue;

		if (find_var_field(var_hist_data, var_name)) {
			if (found) {
				hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE, errpos(var_name));
				return NULL;
			}

			found = file;
		}
	}

	return found;
}

static struct hist_field *find_file_var(struct trace_event_file *file,
					const char *var_name)
{
	struct hist_trigger_data *test_data;
	struct event_trigger_data *test;
	struct hist_field *hist_field;

	lockdep_assert_held(&event_mutex);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			test_data = test->private_data;
			hist_field = find_var_field(test_data, var_name);
			if (hist_field)
				return hist_field;
		}
	}

	return NULL;
}

static struct hist_field *
find_match_var(struct hist_trigger_data *hist_data, char *var_name)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *hist_field, *found = NULL;
	struct trace_event_file *file;
	unsigned int i;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];

		if (data->handler == HANDLER_ONMATCH) {
			char *system = data->match_data.event_system;
			char *event_name = data->match_data.event;

			file = find_var_file(tr, system, event_name, var_name);
			if (!file)
				continue;
			hist_field = find_file_var(file, var_name);
			if (hist_field) {
				if (found) {
					hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE,
						 errpos(var_name));
					return ERR_PTR(-EINVAL);
				}

				found = hist_field;
			}
		}
	}
	return found;
}

static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
					 char *system,
					 char *event_name,
					 char *var_name)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *hist_field = NULL;
	struct trace_event_file *file;

	if (!system || !event_name) {
		hist_field = find_match_var(hist_data, var_name);
		if (IS_ERR(hist_field))
			return NULL;
		if (hist_field)
			return hist_field;
	}

	file = find_var_file(tr, system, event_name, var_name);
	if (!file)
		return NULL;

	hist_field = find_file_var(file, var_name);

	return hist_field;
}

static u64 hist_field_var_ref(struct hist_field *hist_field,
			      struct tracing_map_elt *elt,
			      struct trace_buffer *buffer,
			      struct ring_buffer_event *rbe,
			      void *event)
{
	struct hist_elt_data *elt_data;
	u64 var_val = 0;

	if (WARN_ON_ONCE(!elt))
		return var_val;

	elt_data = elt->private_data;
	var_val = elt_data->var_ref_vals[hist_field->var_ref_idx];

	return var_val;
}

static bool resolve_var_refs(struct hist_trigger_data *hist_data, void *key,
			     u64 *var_ref_vals, bool self)
{
	struct hist_trigger_data *var_data;
	struct tracing_map_elt *var_elt;
	struct hist_field *hist_field;
	unsigned int i, var_idx;
	bool resolved = true;
	u64 var_val = 0;

	for (i = 0; i < hist_data->n_var_refs; i++) {
		hist_field = hist_data->var_refs[i];
		var_idx = hist_field->var.idx;
		var_data = hist_field->var.hist_data;

		if (var_data == NULL) {
			resolved = false;
			break;
		}

		if ((self && var_data != hist_data) ||
		    (!self && var_data == hist_data))
			continue;

		var_elt = tracing_map_lookup(var_data->map, key);
		if (!var_elt) {
			resolved = false;
			break;
		}

		if (!tracing_map_var_set(var_elt, var_idx)) {
			resolved = false;
			break;
		}

		if (self || !hist_field->read_once)
			var_val = tracing_map_read_var(var_elt, var_idx);
		else
			var_val = tracing_map_read_var_once(var_elt, var_idx);

		var_ref_vals[i] = var_val;
	}

	return resolved;
}

static const char *hist_field_name(struct hist_field *field,
				   unsigned int level)
{
	const char *field_name = "";

	if (WARN_ON_ONCE(!field))
		return field_name;

	if (level > 1)
		return field_name;

	if (field->field)
		field_name = field->field->name;
	else if (field->flags & HIST_FIELD_FL_LOG2 ||
		 field->flags & HIST_FIELD_FL_ALIAS ||
		 field->flags & HIST_FIELD_FL_BUCKET)
		field_name = hist_field_name(field->operands[0], ++level);
	else if (field->flags & HIST_FIELD_FL_CPU)
		field_name = "common_cpu";
	else if (field->flags & HIST_FIELD_FL_EXPR ||
		 field->flags & HIST_FIELD_FL_VAR_REF) {
		if (field->system) {
			static char full_name[MAX_FILTER_STR_VAL];

			strcat(full_name, field->system);
			strcat(full_name, ".");
			strcat(full_name, field->event_name);
			strcat(full_name, ".");
			strcat(full_name, field->name);
			field_name = full_name;
		} else
			field_name = field->name;
	} else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
		field_name = "common_timestamp";
	else if (field->flags & HIST_FIELD_FL_STACKTRACE) {
		if (field->field)
			field_name = field->field->name;
		else
			field_name = "common_stacktrace";
	} else if (field->flags & HIST_FIELD_FL_HITCOUNT)
		field_name = "hitcount";

	if (field_name == NULL)
		field_name = "";

	return field_name;
}

static enum hist_field_fn select_value_fn(int field_size, int field_is_signed)
{
	switch (field_size) {
	case 8:
		if (field_is_signed)
			return HIST_FIELD_FN_S64;
		else
			return HIST_FIELD_FN_U64;
	case 4:
		if (field_is_signed)
			return HIST_FIELD_FN_S32;
		else
			return HIST_FIELD_FN_U32;
	case 2:
		if (field_is_signed)
			return HIST_FIELD_FN_S16;
		else
			return HIST_FIELD_FN_U16;
	case 1:
		if (field_is_signed)
			return HIST_FIELD_FN_S8;
		else
			return HIST_FIELD_FN_U8;
	}

	return HIST_FIELD_FN_NOP;
}

static int parse_map_size(char *str)
{
	unsigned long size, map_bits;
	int ret;

	ret = kstrtoul(str, 0, &size);
	if (ret)
		goto out;

	map_bits = ilog2(roundup_pow_of_two(size));
	if (map_bits < TRACING_MAP_BITS_MIN ||
	    map_bits > TRACING_MAP_BITS_MAX)
		ret = -EINVAL;
	else
		ret = map_bits;
 out:
	return ret;
}

static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
{
	unsigned int i;

	if (!attrs)
		return;

	for (i = 0; i < attrs->n_assignments; i++)
		kfree(attrs->assignment_str[i]);

	for (i = 0; i < attrs->n_actions; i++)
		kfree(attrs->action_str[i]);

	kfree(attrs->name);
	kfree(attrs->sort_key_str);
	kfree(attrs->keys_str);
	kfree(attrs->vals_str);
	kfree(attrs->clock);
	kfree(attrs);
}

static int parse_action(char *str, struct hist_trigger_attrs *attrs)
{
	int ret = -EINVAL;

	if (attrs->n_actions >= HIST_ACTIONS_MAX)
		return ret;

	if ((str_has_prefix(str, "onmatch(")) ||
	    (str_has_prefix(str, "onmax(")) ||
	    (str_has_prefix(str, "onchange("))) {
		attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
		if (!attrs->action_str[attrs->n_actions]) {
			ret = -ENOMEM;
			return ret;
		}
		attrs->n_actions++;
		ret = 0;
	}
	return ret;
}

static int parse_assignment(struct trace_array *tr,
			    char *str, struct hist_trigger_attrs *attrs)
{
	int len, ret = 0;

	if ((len = str_has_prefix(str, "key=")) ||
	    (len = str_has_prefix(str, "keys="))) {
		attrs->keys_str = kstrdup(str + len, GFP_KERNEL);
		if (!attrs->keys_str) {
			ret = -ENOMEM;
			goto out;
		}
	} else if ((len = str_has_prefix(str, "val=")) ||
		   (len = str_has_prefix(str, "vals=")) ||
		   (len = str_has_prefix(str, "values="))) {
		attrs->vals_str = kstrdup(str + len, GFP_KERNEL);
		if (!attrs->vals_str) {
			ret = -ENOMEM;
			goto out;
		}
	} else if ((len = str_has_prefix(str, "sort="))) {
		attrs->sort_key_str = kstrdup(str + len, GFP_KERNEL);
		if (!attrs->sort_key_str) {
			ret = -ENOMEM;
			goto out;
		}
	} else if (str_has_prefix(str, "name=")) {
		attrs->name = kstrdup(str, GFP_KERNEL);
		if (!attrs->name) {
			ret = -ENOMEM;
			goto out;
		}
	} else if ((len = str_has_prefix(str, "clock="))) {
		str += len;

		str = strstrip(str);
		attrs->clock = kstrdup(str, GFP_KERNEL);
		if (!attrs->clock) {
			ret = -ENOMEM;
			goto out;
		}
	} else if ((len = str_has_prefix(str, "size="))) {
		int map_bits = parse_map_size(str + len);

		if (map_bits < 0) {
			ret = map_bits;
			goto out;
		}
		attrs->map_bits = map_bits;
	} else {
		char *assignment;

		if (attrs->n_assignments == TRACING_MAP_VARS_MAX) {
			hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(str));
			ret = -EINVAL;
			goto out;
		}

		assignment = kstrdup(str, GFP_KERNEL);
		if (!assignment) {
			ret = -ENOMEM;
			goto out;
		}

		attrs->assignment_str[attrs->n_assignments++] = assignment;
	}
 out:
	return ret;
}

static struct hist_trigger_attrs *
parse_hist_trigger_attrs(struct trace_array *tr, char *trigger_str)
{
	struct hist_trigger_attrs *attrs;
	int ret = 0;

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

	while (trigger_str) {
		char *str = strsep(&trigger_str, ":");
		char *rhs;

		rhs = strchr(str, '=');
		if (rhs) {
			if (!strlen(++rhs)) {
				ret = -EINVAL;
				hist_err(tr, HIST_ERR_EMPTY_ASSIGNMENT, errpos(str));
				goto free;
			}
			ret = parse_assignment(tr, str, attrs);
			if (ret)
				goto free;
		} else if (strcmp(str, "nohitcount") == 0 ||
			   strcmp(str, "NOHC") == 0)
			attrs->no_hitcount = true;
		else if (strcmp(str, "pause") == 0)
			attrs->pause = true;
		else if ((strcmp(str, "cont") == 0) ||
			 (strcmp(str, "continue") == 0))
			attrs->cont = true;
		else if (strcmp(str, "clear") == 0)
			attrs->clear = true;
		else {
			ret = parse_action(str, attrs);
			if (ret)
				goto free;
		}
	}

	if (!attrs->keys_str) {
		ret = -EINVAL;
		goto free;
	}

	if (!attrs->clock) {
		attrs->clock = kstrdup("global", GFP_KERNEL);
		if (!attrs->clock) {
			ret = -ENOMEM;
			goto free;
		}
	}

	return attrs;
 free:
	destroy_hist_trigger_attrs(attrs);

	return ERR_PTR(ret);
}

static inline void save_comm(char *comm, struct task_struct *task)
{
	if (!task->pid) {
		strcpy(comm, "<idle>");
		return;
	}

	if (WARN_ON_ONCE(task->pid < 0)) {
		strcpy(comm, "<XXX>");
		return;
	}

	strncpy(comm, task->comm, TASK_COMM_LEN);
}

static void hist_elt_data_free(struct hist_elt_data *elt_data)
{
	unsigned int i;

	for (i = 0; i < elt_data->n_field_var_str; i++)
		kfree(elt_data->field_var_str[i]);

	kfree(elt_data->field_var_str);

	kfree(elt_data->comm);
	kfree(elt_data);
}

static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
{
	struct hist_elt_data *elt_data = elt->private_data;

	hist_elt_data_free(elt_data);
}

static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
{
	struct hist_trigger_data *hist_data = elt->map->private_data;
	unsigned int size = TASK_COMM_LEN;
	struct hist_elt_data *elt_data;
	struct hist_field *hist_field;
	unsigned int i, n_str;

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

	for_each_hist_field(i, hist_data) {
		hist_field = hist_data->fields[i];

		if (hist_field->flags & HIST_FIELD_FL_EXECNAME) {
			elt_data->comm = kzalloc(size, GFP_KERNEL);
			if (!elt_data->comm) {
				kfree(elt_data);
				return -ENOMEM;
			}
			break;
		}
	}

	n_str = hist_data->n_field_var_str + hist_data->n_save_var_str +
		hist_data->n_var_str;
	if (n_str > SYNTH_FIELDS_MAX) {
		hist_elt_data_free(elt_data);
		return -EINVAL;
	}

	BUILD_BUG_ON(STR_VAR_LEN_MAX & (sizeof(u64) - 1));

	size = STR_VAR_LEN_MAX;

	elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL);
	if (!elt_data->field_var_str) {
		hist_elt_data_free(elt_data);
		return -EINVAL;
	}
	elt_data->n_field_var_str = n_str;

	for (i = 0; i < n_str; i++) {
		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
		if (!elt_data->field_var_str[i]) {
			hist_elt_data_free(elt_data);
			return -ENOMEM;
		}
	}

	elt->private_data = elt_data;

	return 0;
}

static void hist_trigger_elt_data_init(struct tracing_map_elt *elt)
{
	struct hist_elt_data *elt_data = elt->private_data;

	if (elt_data->comm)
		save_comm(elt_data->comm, current);
}

static const struct tracing_map_ops hist_trigger_elt_data_ops = {
	.elt_alloc	= hist_trigger_elt_data_alloc,
	.elt_free	= hist_trigger_elt_data_free,
	.elt_init	= hist_trigger_elt_data_init,
};

static const char *get_hist_field_flags(struct hist_field *hist_field)
{
	const char *flags_str = NULL;

	if (hist_field->flags & HIST_FIELD_FL_HEX)
		flags_str = "hex";
	else if (hist_field->flags & HIST_FIELD_FL_SYM)
		flags_str = "sym";
	else if (hist_field->flags & HIST_FIELD_FL_SYM_OFFSET)
		flags_str = "sym-offset";
	else if (hist_field->flags & HIST_FIELD_FL_EXECNAME)
		flags_str = "execname";
	else if (hist_field->flags & HIST_FIELD_FL_SYSCALL)
		flags_str = "syscall";
	else if (hist_field->flags & HIST_FIELD_FL_LOG2)
		flags_str = "log2";
	else if (hist_field->flags & HIST_FIELD_FL_BUCKET)
		flags_str = "buckets";
	else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
		flags_str = "usecs";
	else if (hist_field->flags & HIST_FIELD_FL_PERCENT)
		flags_str = "percent";
	else if (hist_field->flags & HIST_FIELD_FL_GRAPH)
		flags_str = "graph";
	else if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
		flags_str = "stacktrace";

	return flags_str;
}

static void expr_field_str(struct hist_field *field, char *expr)
{
	if (field->flags & HIST_FIELD_FL_VAR_REF)
		strcat(expr, "$");
	else if (field->flags & HIST_FIELD_FL_CONST) {
		char str[HIST_CONST_DIGITS_MAX];

		snprintf(str, HIST_CONST_DIGITS_MAX, "%llu", field->constant);
		strcat(expr, str);
	}

	strcat(expr, hist_field_name(field, 0));

	if (field->flags && !(field->flags & HIST_FIELD_FL_VAR_REF)) {
		const char *flags_str = get_hist_field_flags(field);

		if (flags_str) {
			strcat(expr, ".");
			strcat(expr, flags_str);
		}
	}
}

static char *expr_str(struct hist_field *field, unsigned int level)
{
	char *expr;

	if (level > 1)
		return NULL;

	expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
	if (!expr)
		return NULL;

	if (!field->operands[0]) {
		expr_field_str(field, expr);
		return expr;
	}

	if (field->operator == FIELD_OP_UNARY_MINUS) {
		char *subexpr;

		strcat(expr, "-(");
		subexpr = expr_str(field->operands[0], ++level);
		if (!subexpr) {
			kfree(expr);
			return NULL;
		}
		strcat(expr, subexpr);
		strcat(expr, ")");

		kfree(subexpr);

		return expr;
	}

	expr_field_str(field->operands[0], expr);

	switch (field->operator) {
	case FIELD_OP_MINUS:
		strcat(expr, "-");
		break;
	case FIELD_OP_PLUS:
		strcat(expr, "+");
		break;
	case FIELD_OP_DIV:
		strcat(expr, "/");
		break;
	case FIELD_OP_MULT:
		strcat(expr, "*");
		break;
	default:
		kfree(expr);
		return NULL;
	}

	expr_field_str(field->operands[1], expr);

	return expr;
}

/*
 * If field_op != FIELD_OP_NONE, *sep points to the root operator
 * of the expression tree to be evaluated.
 */
static int contains_operator(char *str, char **sep)
{
	enum field_op_id field_op = FIELD_OP_NONE;
	char *minus_op, *plus_op, *div_op, *mult_op;


	/*
	 * Report the last occurrence of the operators first, so that the
	 * expression is evaluated left to right. This is important since
	 * subtraction and division are not associative.
	 *
	 *	e.g
	 *		64/8/4/2 is 1, i.e 64/8/4/2 = ((64/8)/4)/2
	 *		14-7-5-2 is 0, i.e 14-7-5-2 = ((14-7)-5)-2
	 */

	/*
	 * First, find lower precedence addition and subtraction
	 * since the expression will be evaluated recursively.
	 */
	minus_op = strrchr(str, '-');
	if (minus_op) {
		/*
		 * Unary minus is not supported in sub-expressions. If
		 * present, it is always the next root operator.
		 */
		if (minus_op == str) {
			field_op = FIELD_OP_UNARY_MINUS;
			goto out;
		}

		field_op = FIELD_OP_MINUS;
	}

	plus_op = strrchr(str, '+');
	if (plus_op || minus_op) {
		/*
		 * For operators of the same precedence use to rightmost as the
		 * root, so that the expression is evaluated left to right.
		 */
		if (plus_op > minus_op)
			field_op = FIELD_OP_PLUS;
		goto out;
	}

	/*
	 * Multiplication and division have higher precedence than addition and
	 * subtraction.
	 */
	div_op = strrchr(str, '/');
	if (div_op)
		field_op = FIELD_OP_DIV;

	mult_op = strrchr(str, '*');
	/*
	 * For operators of the same precedence use to rightmost as the
	 * root, so that the expression is evaluated left to right.
	 */
	if (mult_op > div_op)
		field_op = FIELD_OP_MULT;

out:
	if (sep) {
		switch (field_op) {
		case FIELD_OP_UNARY_MINUS:
		case FIELD_OP_MINUS:
			*sep = minus_op;
			break;
		case FIELD_OP_PLUS:
			*sep = plus_op;
			break;
		case FIELD_OP_DIV:
			*sep = div_op;
			break;
		case FIELD_OP_MULT:
			*sep = mult_op;
			break;
		case FIELD_OP_NONE:
		default:
			*sep = NULL;
			break;
		}
	}

	return field_op;
}

static void get_hist_field(struct hist_field *hist_field)
{
	hist_field->ref++;
}

static void __destroy_hist_field(struct hist_field *hist_field)
{
	if (--hist_field->ref > 1)
		return;

	kfree(hist_field->var.name);
	kfree(hist_field->name);

	/* Can likely be a const */
	kfree_const(hist_field->type);

	kfree(hist_field->system);
	kfree(hist_field->event_name);

	kfree(hist_field);
}

static void destroy_hist_field(struct hist_field *hist_field,
			       unsigned int level)
{
	unsigned int i;

	if (level > 3)
		return;

	if (!hist_field)
		return;

	if (hist_field->flags & HIST_FIELD_FL_VAR_REF)
		return; /* var refs will be destroyed separately */

	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
		destroy_hist_field(hist_field->operands[i], level + 1);

	__destroy_hist_field(hist_field);
}

static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
					    struct ftrace_event_field *field,
					    unsigned long flags,
					    char *var_name)
{
	struct hist_field *hist_field;

	if (field && is_function_field(field))
		return NULL;

	hist_field = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
	if (!hist_field)
		return NULL;

	hist_field->ref = 1;

	hist_field->hist_data = hist_data;

	if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
		goto out; /* caller will populate */

	if (flags & HIST_FIELD_FL_VAR_REF) {
		hist_field->fn_num = HIST_FIELD_FN_VAR_REF;
		goto out;
	}

	if (flags & HIST_FIELD_FL_HITCOUNT) {
		hist_field->fn_num = HIST_FIELD_FN_COUNTER;
		hist_field->size = sizeof(u64);
		hist_field->type = "u64";
		goto out;
	}

	if (flags & HIST_FIELD_FL_CONST) {
		hist_field->fn_num = HIST_FIELD_FN_CONST;
		hist_field->size = sizeof(u64);
		hist_field->type = kstrdup("u64", GFP_KERNEL);
		if (!hist_field->type)
			goto free;
		goto out;
	}

	if (flags & HIST_FIELD_FL_STACKTRACE) {
		if (field)
			hist_field->fn_num = HIST_FIELD_FN_STACK;
		else
			hist_field->fn_num = HIST_FIELD_FN_NOP;
		hist_field->size = HIST_STACKTRACE_SIZE;
		hist_field->type = kstrdup_const("unsigned long[]", GFP_KERNEL);
		if (!hist_field->type)
			goto free;
		goto out;
	}

	if (flags & (HIST_FIELD_FL_LOG2 | HIST_FIELD_FL_BUCKET)) {
		unsigned long fl = flags & ~(HIST_FIELD_FL_LOG2 | HIST_FIELD_FL_BUCKET);
		hist_field->fn_num = flags & HIST_FIELD_FL_LOG2 ? HIST_FIELD_FN_LOG2 :
			HIST_FIELD_FN_BUCKET;
		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
		if (!hist_field->operands[0])
			goto free;
		hist_field->size = hist_field->operands[0]->size;
		hist_field->type = kstrdup_const(hist_field->operands[0]->type, GFP_KERNEL);
		if (!hist_field->type)
			goto free;
		goto out;
	}

	if (flags & HIST_FIELD_FL_TIMESTAMP) {
		hist_field->fn_num = HIST_FIELD_FN_TIMESTAMP;
		hist_field->size = sizeof(u64);
		hist_field->type = "u64";
		goto out;
	}

	if (flags & HIST_FIELD_FL_CPU) {
		hist_field->fn_num = HIST_FIELD_FN_CPU;
		hist_field->size = sizeof(int);
		hist_field->type = "unsigned int";
		goto out;
	}

	if (WARN_ON_ONCE(!field))
		goto out;

	/* Pointers to strings are just pointers and dangerous to dereference */
	if (is_string_field(field) &&
	    (field->filter_type != FILTER_PTR_STRING)) {
		flags |= HIST_FIELD_FL_STRING;

		hist_field->size = MAX_FILTER_STR_VAL;
		hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
		if (!hist_field->type)
			goto free;

		if (field->filter_type == FILTER_STATIC_STRING) {
			hist_field->fn_num = HIST_FIELD_FN_STRING;
			hist_field->size = field->size;
		} else if (field->filter_type == FILTER_DYN_STRING) {
			hist_field->fn_num = HIST_FIELD_FN_DYNSTRING;
		} else if (field->filter_type == FILTER_RDYN_STRING)
			hist_field->fn_num = HIST_FIELD_FN_RELDYNSTRING;
		else
			hist_field->fn_num = HIST_FIELD_FN_PSTRING;
	} else {
		hist_field->size = field->size;
		hist_field->is_signed = field->is_signed;
		hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
		if (!hist_field->type)
			goto free;

		hist_field->fn_num = select_value_fn(field->size,
						     field->is_signed);
		if (hist_field->fn_num == HIST_FIELD_FN_NOP) {
			destroy_hist_field(hist_field, 0);
			return NULL;
		}
	}
 out:
	hist_field->field = field;
	hist_field->flags = flags;

	if (var_name) {
		hist_field->var.name = kstrdup(var_name, GFP_KERNEL);
		if (!hist_field->var.name)
			goto free;
	}

	return hist_field;
 free:
	destroy_hist_field(hist_field, 0);
	return NULL;
}

static void destroy_hist_fields(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < HIST_FIELDS_MAX; i++) {
		if (hist_data->fields[i]) {
			destroy_hist_field(hist_data->fields[i], 0);
			hist_data->fields[i] = NULL;
		}
	}

	for (i = 0; i < hist_data->n_var_refs; i++) {
		WARN_ON(!(hist_data->var_refs[i]->flags & HIST_FIELD_FL_VAR_REF));
		__destroy_hist_field(hist_data->var_refs[i]);
		hist_data->var_refs[i] = NULL;
	}
}

static int init_var_ref(struct hist_field *ref_field,
			struct hist_field *var_field,
			char *system, char *event_name)
{
	int err = 0;

	ref_field->var.idx = var_field->var.idx;
	ref_field->var.hist_data = var_field->hist_data;
	ref_field->size = var_field->size;
	ref_field->is_signed = var_field->is_signed;
	ref_field->flags |= var_field->flags &
		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);

	if (system) {
		ref_field->system = kstrdup(system, GFP_KERNEL);
		if (!ref_field->system)
			return -ENOMEM;
	}

	if (event_name) {
		ref_field->event_name = kstrdup(event_name, GFP_KERNEL);
		if (!ref_field->event_name) {
			err = -ENOMEM;
			goto free;
		}
	}

	if (var_field->var.name) {
		ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
		if (!ref_field->name) {
			err = -ENOMEM;
			goto free;
		}
	} else if (var_field->name) {
		ref_field->name = kstrdup(var_field->name, GFP_KERNEL);
		if (!ref_field->name) {
			err = -ENOMEM;
			goto free;
		}
	}

	ref_field->type = kstrdup_const(var_field->type, GFP_KERNEL);
	if (!ref_field->type) {
		err = -ENOMEM;
		goto free;
	}
 out:
	return err;
 free:
	kfree(ref_field->system);
	ref_field->system = NULL;
	kfree(ref_field->event_name);
	ref_field->event_name = NULL;
	kfree(ref_field->name);
	ref_field->name = NULL;

	goto out;
}

static int find_var_ref_idx(struct hist_trigger_data *hist_data,
			    struct hist_field *var_field)
{
	struct hist_field *ref_field;
	int i;

	for (i = 0; i < hist_data->n_var_refs; i++) {
		ref_field = hist_data->var_refs[i];
		if (ref_field->var.idx == var_field->var.idx &&
		    ref_field->var.hist_data == var_field->hist_data)
			return i;
	}

	return -ENOENT;
}

/**
 * create_var_ref - Create a variable reference and attach it to trigger
 * @hist_data: The trigger that will be referencing the variable
 * @var_field: The VAR field to create a reference to
 * @system: The optional system string
 * @event_name: The optional event_name string
 *
 * Given a variable hist_field, create a VAR_REF hist_field that
 * represents a reference to it.
 *
 * This function also adds the reference to the trigger that
 * now references the variable.
 *
 * Return: The VAR_REF field if successful, NULL if not
 */
static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data,
					 struct hist_field *var_field,
					 char *system, char *event_name)
{
	unsigned long flags = HIST_FIELD_FL_VAR_REF;
	struct hist_field *ref_field;
	int i;

	/* Check if the variable already exists */
	for (i = 0; i < hist_data->n_var_refs; i++) {
		ref_field = hist_data->var_refs[i];
		if (ref_field->var.idx == var_field->var.idx &&
		    ref_field->var.hist_data == var_field->hist_data) {
			get_hist_field(ref_field);
			return ref_field;
		}
	}
	/* Sanity check to avoid out-of-bound write on 'hist_data->var_refs' */
	if (hist_data->n_var_refs >= TRACING_MAP_VARS_MAX)
		return NULL;
	ref_field = create_hist_field(var_field->hist_data, NULL, flags, NULL);
	if (ref_field) {
		if (init_var_ref(ref_field, var_field, system, event_name)) {
			destroy_hist_field(ref_field, 0);
			return NULL;
		}

		hist_data->var_refs[hist_data->n_var_refs] = ref_field;
		ref_field->var_ref_idx = hist_data->n_var_refs++;
	}

	return ref_field;
}

static bool is_var_ref(char *var_name)
{
	if (!var_name || strlen(var_name) < 2 || var_name[0] != '$')
		return false;

	return true;
}

static char *field_name_from_var(struct hist_trigger_data *hist_data,
				 char *var_name)
{
	char *name, *field;
	unsigned int i;

	for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
		name = hist_data->attrs->var_defs.name[i];

		if (strcmp(var_name, name) == 0) {
			field = hist_data->attrs->var_defs.expr[i];
			if (contains_operator(field, NULL) || is_var_ref(field))
				continue;
			return field;
		}
	}

	return NULL;
}

static char *local_field_var_ref(struct hist_trigger_data *hist_data,
				 char *system, char *event_name,
				 char *var_name)
{
	struct trace_event_call *call;

	if (system && event_name) {
		call = hist_data->event_file->event_call;

		if (strcmp(system, call->class->system) != 0)
			return NULL;

		if (strcmp(event_name, trace_event_name(call)) != 0)
			return NULL;
	}

	if (!!system != !!event_name)
		return NULL;

	if (!is_var_ref(var_name))
		return NULL;

	var_name++;

	return field_name_from_var(hist_data, var_name);
}

static struct hist_field *parse_var_ref(struct hist_trigger_data *hist_data,
					char *system, char *event_name,
					char *var_name)
{
	struct hist_field *var_field = NULL, *ref_field = NULL;
	struct trace_array *tr = hist_data->event_file->tr;

	if (!is_var_ref(var_name))
		return NULL;

	var_name++;

	var_field = find_event_var(hist_data, system, event_name, var_name);
	if (var_field)
		ref_field = create_var_ref(hist_data, var_field,
					   system, event_name);

	if (!ref_field)
		hist_err(tr, HIST_ERR_VAR_NOT_FOUND, errpos(var_name));

	return ref_field;
}

static struct ftrace_event_field *
parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
	    char *field_str, unsigned long *flags, unsigned long *buckets)
{
	struct ftrace_event_field *field = NULL;
	char *field_name, *modifier, *str;
	struct trace_array *tr = file->tr;

	modifier = str = kstrdup(field_str, GFP_KERNEL);
	if (!modifier)
		return ERR_PTR(-ENOMEM);

	field_name = strsep(&modifier, ".");
	if (modifier) {
		if (strcmp(modifier, "hex") == 0)
			*flags |= HIST_FIELD_FL_HEX;
		else if (strcmp(modifier, "sym") == 0)
			*flags |= HIST_FIELD_FL_SYM;
		/*
		 * 'sym-offset' occurrences in the trigger string are modified
		 * to 'symXoffset' to simplify arithmetic expression parsing.
		 */
		else if (strcmp(modifier, "symXoffset") == 0)
			*flags |= HIST_FIELD_FL_SYM_OFFSET;
		else if ((strcmp(modifier, "execname") == 0) &&
			 (strcmp(field_name, "common_pid") == 0))
			*flags |= HIST_FIELD_FL_EXECNAME;
		else if (strcmp(modifier, "syscall") == 0)
			*flags |= HIST_FIELD_FL_SYSCALL;
		else if (strcmp(modifier, "stacktrace") == 0)
			*flags |= HIST_FIELD_FL_STACKTRACE;
		else if (strcmp(modifier, "log2") == 0)
			*flags |= HIST_FIELD_FL_LOG2;
		else if (strcmp(modifier, "usecs") == 0)
			*flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
		else if (strncmp(modifier, "bucket", 6) == 0) {
			int ret;

			modifier += 6;

			if (*modifier == 's')
				modifier++;
			if (*modifier != '=')
				goto error;
			modifier++;
			ret = kstrtoul(modifier, 0, buckets);
			if (ret || !(*buckets))
				goto error;
			*flags |= HIST_FIELD_FL_BUCKET;
		} else if (strncmp(modifier, "percent", 7) == 0) {
			if (*flags & (HIST_FIELD_FL_VAR | HIST_FIELD_FL_KEY))
				goto error;
			*flags |= HIST_FIELD_FL_PERCENT;
		} else if (strncmp(modifier, "graph", 5) == 0) {
			if (*flags & (HIST_FIELD_FL_VAR | HIST_FIELD_FL_KEY))
				goto error;
			*flags |= HIST_FIELD_FL_GRAPH;
		} else {
 error:
			hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
			field = ERR_PTR(-EINVAL);
			goto out;
		}
	}

	if (strcmp(field_name, "common_timestamp") == 0) {
		*flags |= HIST_FIELD_FL_TIMESTAMP;
		hist_data->enable_timestamps = true;
		if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
			hist_data->attrs->ts_in_usecs = true;
	} else if (strcmp(field_name, "common_stacktrace") == 0) {
		*flags |= HIST_FIELD_FL_STACKTRACE;
	} else if (strcmp(field_name, "common_cpu") == 0)
		*flags |= HIST_FIELD_FL_CPU;
	else if (strcmp(field_name, "hitcount") == 0)
		*flags |= HIST_FIELD_FL_HITCOUNT;
	else {
		field = trace_find_event_field(file->event_call, field_name);
		if (!field || !field->size) {
			/*
			 * For backward compatibility, if field_name
			 * was "cpu" or "stacktrace", then we treat this
			 * the same as common_cpu and common_stacktrace
			 * respectively. This also works for "CPU", and
			 * "STACKTRACE".
			 */
			if (field && field->filter_type == FILTER_CPU) {
				*flags |= HIST_FIELD_FL_CPU;
			} else if (field && field->filter_type == FILTER_STACKTRACE) {
				*flags |= HIST_FIELD_FL_STACKTRACE;
			} else {
				hist_err(tr, HIST_ERR_FIELD_NOT_FOUND,
					 errpos(field_name));
				field = ERR_PTR(-EINVAL);
				goto out;
			}
		}
	}
 out:
	kfree(str);

	return field;
}

static struct hist_field *create_alias(struct hist_trigger_data *hist_data,
				       struct hist_field *var_ref,
				       char *var_name)
{
	struct hist_field *alias = NULL;
	unsigned long flags = HIST_FIELD_FL_ALIAS | HIST_FIELD_FL_VAR;

	alias = create_hist_field(hist_data, NULL, flags, var_name);
	if (!alias)
		return NULL;

	alias->fn_num = var_ref->fn_num;
	alias->operands[0] = var_ref;

	if (init_var_ref(alias, var_ref, var_ref->system, var_ref->event_name)) {
		destroy_hist_field(alias, 0);
		return NULL;
	}

	alias->var_ref_idx = var_ref->var_ref_idx;

	return alias;
}

static struct hist_field *parse_const(struct hist_trigger_data *hist_data,
				      char *str, char *var_name,
				      unsigned long *flags)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *field = NULL;
	u64 constant;

	if (kstrtoull(str, 0, &constant)) {
		hist_err(tr, HIST_ERR_EXPECT_NUMBER, errpos(str));
		return NULL;
	}

	*flags |= HIST_FIELD_FL_CONST;
	field = create_hist_field(hist_data, NULL, *flags, var_name);
	if (!field)
		return NULL;

	field->constant = constant;

	return field;
}

static struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
				     struct trace_event_file *file, char *str,
				     unsigned long *flags, char *var_name)
{
	char *s, *ref_system = NULL, *ref_event = NULL, *ref_var = str;
	struct ftrace_event_field *field = NULL;
	struct hist_field *hist_field = NULL;
	unsigned long buckets = 0;
	int ret = 0;

	if (isdigit(str[0])) {
		hist_field = parse_const(hist_data, str, var_name, flags);
		if (!hist_field) {
			ret = -EINVAL;
			goto out;
		}
		return hist_field;
	}

	s = strchr(str, '.');
	if (s) {
		s = strchr(++s, '.');
		if (s) {
			ref_system = strsep(&str, ".");
			if (!str) {
				ret = -EINVAL;
				goto out;
			}
			ref_event = strsep(&str, ".");
			if (!str) {
				ret = -EINVAL;
				goto out;
			}
			ref_var = str;
		}
	}

	s = local_field_var_ref(hist_data, ref_system, ref_event, ref_var);
	if (!s) {
		hist_field = parse_var_ref(hist_data, ref_system,
					   ref_event, ref_var);
		if (hist_field) {
			if (var_name) {
				hist_field = create_alias(hist_data, hist_field, var_name);
				if (!hist_field) {
					ret = -ENOMEM;
					goto out;
				}
			}
			return hist_field;
		}
	} else
		str = s;

	field = parse_field(hist_data, file, str, flags, &buckets);
	if (IS_ERR(field)) {
		ret = PTR_ERR(field);
		goto out;
	}

	hist_field = create_hist_field(hist_data, field, *flags, var_name);
	if (!hist_field) {
		ret = -ENOMEM;
		goto out;
	}
	hist_field->buckets = buckets;

	return hist_field;
 out:
	return ERR_PTR(ret);
}

static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
				     struct trace_event_file *file,
				     char *str, unsigned long flags,
				     char *var_name, unsigned int *n_subexprs);

static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
				      struct trace_event_file *file,
				      char *str, unsigned long flags,
				      char *var_name, unsigned int *n_subexprs)
{
	struct hist_field *operand1, *expr = NULL;
	unsigned long operand_flags;
	int ret = 0;
	char *s;

	/* Unary minus operator, increment n_subexprs */
	++*n_subexprs;

	/* we support only -(xxx) i.e. explicit parens required */

	if (*n_subexprs > 3) {
		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
		ret = -EINVAL;
		goto free;
	}

	str++; /* skip leading '-' */

	s = strchr(str, '(');
	if (s)
		str++;
	else {
		ret = -EINVAL;
		goto free;
	}

	s = strrchr(str, ')');
	if (s) {
		 /* unary minus not supported in sub-expressions */
		if (*(s+1) != '\0') {
			hist_err(file->tr, HIST_ERR_UNARY_MINUS_SUBEXPR,
				 errpos(str));
			ret = -EINVAL;
			goto free;
		}
		*s = '\0';
	}
	else {
		ret = -EINVAL; /* no closing ')' */
		goto free;
	}

	flags |= HIST_FIELD_FL_EXPR;
	expr = create_hist_field(hist_data, NULL, flags, var_name);
	if (!expr) {
		ret = -ENOMEM;
		goto free;
	}

	operand_flags = 0;
	operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, n_subexprs);
	if (IS_ERR(operand1)) {
		ret = PTR_ERR(operand1);
		goto free;
	}
	if (operand1->flags & HIST_FIELD_FL_STRING) {
		/* String type can not be the operand of unary operator. */
		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(str));
		destroy_hist_field(operand1, 0);
		ret = -EINVAL;
		goto free;
	}

	expr->flags |= operand1->flags &
		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
	expr->fn_num = HIST_FIELD_FN_UMINUS;
	expr->operands[0] = operand1;
	expr->size = operand1->size;
	expr->is_signed = operand1->is_signed;
	expr->operator = FIELD_OP_UNARY_MINUS;
	expr->name = expr_str(expr, 0);
	expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
	if (!expr->type) {
		ret = -ENOMEM;
		goto free;
	}

	return expr;
 free:
	destroy_hist_field(expr, 0);
	return ERR_PTR(ret);
}

/*
 * If the operands are var refs, return pointers the
 * variable(s) referenced in var1 and var2, else NULL.
 */
static int check_expr_operands(struct trace_array *tr,
			       struct hist_field *operand1,
			       struct hist_field *operand2,
			       struct hist_field **var1,
			       struct hist_field **var2)
{
	unsigned long operand1_flags = operand1->flags;
	unsigned long operand2_flags = operand2->flags;

	if ((operand1_flags & HIST_FIELD_FL_VAR_REF) ||
	    (operand1_flags & HIST_FIELD_FL_ALIAS)) {
		struct hist_field *var;

		var = find_var_field(operand1->var.hist_data, operand1->name);
		if (!var)
			return -EINVAL;
		operand1_flags = var->flags;
		*var1 = var;
	}

	if ((operand2_flags & HIST_FIELD_FL_VAR_REF) ||
	    (operand2_flags & HIST_FIELD_FL_ALIAS)) {
		struct hist_field *var;

		var = find_var_field(operand2->var.hist_data, operand2->name);
		if (!var)
			return -EINVAL;
		operand2_flags = var->flags;
		*var2 = var;
	}

	if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
	    (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS)) {
		hist_err(tr, HIST_ERR_TIMESTAMP_MISMATCH, 0);
		return -EINVAL;
	}

	return 0;
}

static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
				     struct trace_event_file *file,
				     char *str, unsigned long flags,
				     char *var_name, unsigned int *n_subexprs)
{
	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
	struct hist_field *var1 = NULL, *var2 = NULL;
	unsigned long operand_flags, operand2_flags;
	int field_op, ret = -EINVAL;
	char *sep, *operand1_str;
	enum hist_field_fn op_fn;
	bool combine_consts;

	if (*n_subexprs > 3) {
		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
		return ERR_PTR(-EINVAL);
	}

	field_op = contains_operator(str, &sep);

	if (field_op == FIELD_OP_NONE)
		return parse_atom(hist_data, file, str, &flags, var_name);

	if (field_op == FIELD_OP_UNARY_MINUS)
		return parse_unary(hist_data, file, str, flags, var_name, n_subexprs);

	/* Binary operator found, increment n_subexprs */
	++*n_subexprs;

	/* Split the expression string at the root operator */
	if (!sep)
		return ERR_PTR(-EINVAL);

	*sep = '\0';
	operand1_str = str;
	str = sep+1;

	/* Binary operator requires both operands */
	if (*operand1_str == '\0' || *str == '\0')
		return ERR_PTR(-EINVAL);

	operand_flags = 0;

	/* LHS of string is an expression e.g. a+b in a+b+c */
	operand1 = parse_expr(hist_data, file, operand1_str, operand_flags, NULL, n_subexprs);
	if (IS_ERR(operand1))
		return ERR_CAST(operand1);

	if (operand1->flags & HIST_FIELD_FL_STRING) {
		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(operand1_str));
		ret = -EINVAL;
		goto free_op1;
	}

	/* RHS of string is another expression e.g. c in a+b+c */
	operand_flags = 0;
	operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, n_subexprs);
	if (IS_ERR(operand2)) {
		ret = PTR_ERR(operand2);
		goto free_op1;
	}
	if (operand2->flags & HIST_FIELD_FL_STRING) {
		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(str));
		ret = -EINVAL;
		goto free_operands;
	}

	switch (field_op) {
	case FIELD_OP_MINUS:
		op_fn = HIST_FIELD_FN_MINUS;
		break;
	case FIELD_OP_PLUS:
		op_fn = HIST_FIELD_FN_PLUS;
		break;
	case FIELD_OP_DIV:
		op_fn = HIST_FIELD_FN_DIV;
		break;
	case FIELD_OP_MULT:
		op_fn = HIST_FIELD_FN_MULT;
		break;
	default:
		ret = -EINVAL;
		goto free_operands;
	}

	ret = check_expr_operands(file->tr, operand1, operand2, &var1, &var2);
	if (ret)
		goto free_operands;

	operand_flags = var1 ? var1->flags : operand1->flags;
	operand2_flags = var2 ? var2->flags : operand2->flags;

	/*
	 * If both operands are constant, the expression can be
	 * collapsed to a single constant.
	 */
	combine_consts = operand_flags & operand2_flags & HIST_FIELD_FL_CONST;

	flags |= combine_consts ? HIST_FIELD_FL_CONST : HIST_FIELD_FL_EXPR;

	flags |= operand1->flags &
		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);

	expr = create_hist_field(hist_data, NULL, flags, var_name);
	if (!expr) {
		ret = -ENOMEM;
		goto free_operands;
	}

	operand1->read_once = true;
	operand2->read_once = true;

	/* The operands are now owned and free'd by 'expr' */
	expr->operands[0] = operand1;
	expr->operands[1] = operand2;

	if (field_op == FIELD_OP_DIV &&
			operand2_flags & HIST_FIELD_FL_CONST) {
		u64 divisor = var2 ? var2->constant : operand2->constant;

		if (!divisor) {
			hist_err(file->tr, HIST_ERR_DIVISION_BY_ZERO, errpos(str));
			ret = -EDOM;
			goto free_expr;
		}

		/*
		 * Copy the divisor here so we don't have to look it up
		 * later if this is a var ref
		 */
		operand2->constant = divisor;
		op_fn = hist_field_get_div_fn(operand2);
	}

	expr->fn_num = op_fn;

	if (combine_consts) {
		if (var1)
			expr->operands[0] = var1;
		if (var2)
			expr->operands[1] = var2;

		expr->constant = hist_fn_call(expr, NULL, NULL, NULL, NULL);
		expr->fn_num = HIST_FIELD_FN_CONST;

		expr->operands[0] = NULL;
		expr->operands[1] = NULL;

		/*
		 * var refs won't be destroyed immediately
		 * See: destroy_hist_field()
		 */
		destroy_hist_field(operand2, 0);
		destroy_hist_field(operand1, 0);

		expr->name = expr_str(expr, 0);
	} else {
		/* The operand sizes should be the same, so just pick one */
		expr->size = operand1->size;
		expr->is_signed = operand1->is_signed;

		expr->operator = field_op;
		expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
		if (!expr->type) {
			ret = -ENOMEM;
			goto free_expr;
		}

		expr->name = expr_str(expr, 0);
	}

	return expr;

free_operands:
	destroy_hist_field(operand2, 0);
free_op1:
	destroy_hist_field(operand1, 0);
	return ERR_PTR(ret);

free_expr:
	destroy_hist_field(expr, 0);
	return ERR_PTR(ret);
}

static char *find_trigger_filter(struct hist_trigger_data *hist_data,
				 struct trace_event_file *file)
{
	struct event_trigger_data *test;

	lockdep_assert_held(&event_mutex);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (test->private_data == hist_data)
				return test->filter_str;
		}
	}

	return NULL;
}

static struct event_command trigger_hist_cmd;
static int event_hist_trigger_parse(struct event_command *cmd_ops,
				    struct trace_event_file *file,
				    char *glob, char *cmd,
				    char *param_and_filter);

static bool compatible_keys(struct hist_trigger_data *target_hist_data,
			    struct hist_trigger_data *hist_data,
			    unsigned int n_keys)
{
	struct hist_field *target_hist_field, *hist_field;
	unsigned int n, i, j;

	if (hist_data->n_fields - hist_data->n_vals != n_keys)
		return false;

	i = hist_data->n_vals;
	j = target_hist_data->n_vals;

	for (n = 0; n < n_keys; n++) {
		hist_field = hist_data->fields[i + n];
		target_hist_field = target_hist_data->fields[j + n];

		if (strcmp(hist_field->type, target_hist_field->type) != 0)
			return false;
		if (hist_field->size != target_hist_field->size)
			return false;
		if (hist_field->is_signed != target_hist_field->is_signed)
			return false;
	}

	return true;
}

static struct hist_trigger_data *
find_compatible_hist(struct hist_trigger_data *target_hist_data,
		     struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data;
	struct event_trigger_data *test;
	unsigned int n_keys;

	lockdep_assert_held(&event_mutex);

	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			hist_data = test->private_data;

			if (compatible_keys(target_hist_data, hist_data, n_keys))
				return hist_data;
		}
	}

	return NULL;
}

static struct trace_event_file *event_file(struct trace_array *tr,
					   char *system, char *event_name)
{
	struct trace_event_file *file;

	file = __find_event_file(tr, system, event_name);
	if (!file)
		return ERR_PTR(-EINVAL);

	return file;
}

static struct hist_field *
find_synthetic_field_var(struct hist_trigger_data *target_hist_data,
			 char *system, char *event_name, char *field_name)
{
	struct hist_field *event_var;
	char *synthetic_name;

	synthetic_name = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
	if (!synthetic_name)
		return ERR_PTR(-ENOMEM);

	strcpy(synthetic_name, "synthetic_");
	strcat(synthetic_name, field_name);

	event_var = find_event_var(target_hist_data, system, event_name, synthetic_name);

	kfree(synthetic_name);

	return event_var;
}

/**
 * create_field_var_hist - Automatically create a histogram and var for a field
 * @target_hist_data: The target hist trigger
 * @subsys_name: Optional subsystem name
 * @event_name: Optional event name
 * @field_name: The name of the field (and the resulting variable)
 *
 * Hist trigger actions fetch data from variables, not directly from
 * events.  However, for convenience, users are allowed to directly
 * specify an event field in an action, which will be automatically
 * converted into a variable on their behalf.
 *
 * If a user specifies a field on an event that isn't the event the
 * histogram currently being defined (the target event histogram), the
 * only way that can be accomplished is if a new hist trigger is
 * created and the field variable defined on that.
 *
 * This function creates a new histogram compatible with the target
 * event (meaning a histogram with the same key as the target
 * histogram), and creates a variable for the specified field, but
 * with 'synthetic_' prepended to the variable name in order to avoid
 * collision with normal field variables.
 *
 * Return: The variable created for the field.
 */
static struct hist_field *
create_field_var_hist(struct hist_trigger_data *target_hist_data,
		      char *subsys_name, char *event_name, char *field_name)
{
	struct trace_array *tr = target_hist_data->event_file->tr;
	struct hist_trigger_data *hist_data;
	unsigned int i, n, first = true;
	struct field_var_hist *var_hist;
	struct trace_event_file *file;
	struct hist_field *key_field;
	struct hist_field *event_var;
	char *saved_filter;
	char *cmd;
	int ret;

	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
		return ERR_PTR(-EINVAL);
	}

	file = event_file(tr, subsys_name, event_name);

	if (IS_ERR(file)) {
		hist_err(tr, HIST_ERR_EVENT_FILE_NOT_FOUND, errpos(field_name));
		ret = PTR_ERR(file);
		return ERR_PTR(ret);
	}

	/*
	 * Look for a histogram compatible with target.  We'll use the
	 * found histogram specification to create a new matching
	 * histogram with our variable on it.  target_hist_data is not
	 * yet a registered histogram so we can't use that.
	 */
	hist_data = find_compatible_hist(target_hist_data, file);
	if (!hist_data) {
		hist_err(tr, HIST_ERR_HIST_NOT_FOUND, errpos(field_name));
		return ERR_PTR(-EINVAL);
	}

	/* See if a synthetic field variable has already been created */
	event_var = find_synthetic_field_var(target_hist_data, subsys_name,
					     event_name, field_name);
	if (!IS_ERR_OR_NULL(event_var))
		return event_var;

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

	cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
	if (!cmd) {
		kfree(var_hist);
		return ERR_PTR(-ENOMEM);
	}

	/* Use the same keys as the compatible histogram */
	strcat(cmd, "keys=");

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];
		if (!first)
			strcat(cmd, ",");
		strcat(cmd, key_field->field->name);
		first = false;
	}

	/* Create the synthetic field variable specification */
	strcat(cmd, ":synthetic_");
	strcat(cmd, field_name);
	strcat(cmd, "=");
	strcat(cmd, field_name);

	/* Use the same filter as the compatible histogram */
	saved_filter = find_trigger_filter(hist_data, file);
	if (saved_filter) {
		strcat(cmd, " if ");
		strcat(cmd, saved_filter);
	}

	var_hist->cmd = kstrdup(cmd, GFP_KERNEL);
	if (!var_hist->cmd) {
		kfree(cmd);
		kfree(var_hist);
		return ERR_PTR(-ENOMEM);
	}

	/* Save the compatible histogram information */
	var_hist->hist_data = hist_data;

	/* Create the new histogram with our variable */
	ret = event_hist_trigger_parse(&trigger_hist_cmd, file,
				       "", "hist", cmd);
	if (ret) {
		kfree(cmd);
		kfree(var_hist->cmd);
		kfree(var_hist);
		hist_err(tr, HIST_ERR_HIST_CREATE_FAIL, errpos(field_name));
		return ERR_PTR(ret);
	}

	kfree(cmd);

	/* If we can't find the variable, something went wrong */
	event_var = find_synthetic_field_var(target_hist_data, subsys_name,
					     event_name, field_name);
	if (IS_ERR_OR_NULL(event_var)) {
		kfree(var_hist->cmd);
		kfree(var_hist);
		hist_err(tr, HIST_ERR_SYNTH_VAR_NOT_FOUND, errpos(field_name));
		return ERR_PTR(-EINVAL);
	}

	n = target_hist_data->n_field_var_hists;
	target_hist_data->field_var_hists[n] = var_hist;
	target_hist_data->n_field_var_hists++;

	return event_var;
}

static struct hist_field *
find_target_event_var(struct hist_trigger_data *hist_data,
		      char *subsys_name, char *event_name, char *var_name)
{
	struct trace_event_file *file = hist_data->event_file;
	struct hist_field *hist_field = NULL;

	if (subsys_name) {
		struct trace_event_call *call;

		if (!event_name)
			return NULL;

		call = file->event_call;

		if (strcmp(subsys_name, call->class->system) != 0)
			return NULL;

		if (strcmp(event_name, trace_event_name(call)) != 0)
			return NULL;
	}

	hist_field = find_var_field(hist_data, var_name);

	return hist_field;
}

static inline void __update_field_vars(struct tracing_map_elt *elt,
				       struct trace_buffer *buffer,
				       struct ring_buffer_event *rbe,
				       void *rec,
				       struct field_var **field_vars,
				       unsigned int n_field_vars,
				       unsigned int field_var_str_start)
{
	struct hist_elt_data *elt_data = elt->private_data;
	unsigned int i, j, var_idx;
	u64 var_val;

	/* Make sure stacktrace can fit in the string variable length */
	BUILD_BUG_ON((HIST_STACKTRACE_DEPTH + 1) * sizeof(long) >= STR_VAR_LEN_MAX);

	for (i = 0, j = field_var_str_start; i < n_field_vars; i++) {
		struct field_var *field_var = field_vars[i];
		struct hist_field *var = field_var->var;
		struct hist_field *val = field_var->val;

		var_val = hist_fn_call(val, elt, buffer, rbe, rec);
		var_idx = var->var.idx;

		if (val->flags & (HIST_FIELD_FL_STRING |
				  HIST_FIELD_FL_STACKTRACE)) {
			char *str = elt_data->field_var_str[j++];
			char *val_str = (char *)(uintptr_t)var_val;
			unsigned int size;

			if (val->flags & HIST_FIELD_FL_STRING) {
				size = min(val->size, STR_VAR_LEN_MAX);
				strscpy(str, val_str, size);
			} else {
				char *stack_start = str + sizeof(unsigned long);
				int e;

				e = stack_trace_save((void *)stack_start,
						     HIST_STACKTRACE_DEPTH,
						     HIST_STACKTRACE_SKIP);
				if (e < HIST_STACKTRACE_DEPTH - 1)
					((unsigned long *)stack_start)[e] = 0;
				*((unsigned long *)str) = e;
			}
			var_val = (u64)(uintptr_t)str;
		}
		tracing_map_set_var(elt, var_idx, var_val);
	}
}

static void update_field_vars(struct hist_trigger_data *hist_data,
			      struct tracing_map_elt *elt,
			      struct trace_buffer *buffer,
			      struct ring_buffer_event *rbe,
			      void *rec)
{
	__update_field_vars(elt, buffer, rbe, rec, hist_data->field_vars,
			    hist_data->n_field_vars, 0);
}

static void save_track_data_vars(struct hist_trigger_data *hist_data,
				 struct tracing_map_elt *elt,
				 struct trace_buffer *buffer,  void *rec,
				 struct ring_buffer_event *rbe, void *key,
				 struct action_data *data, u64 *var_ref_vals)
{
	__update_field_vars(elt, buffer, rbe, rec, hist_data->save_vars,
			    hist_data->n_save_vars, hist_data->n_field_var_str);
}

static struct hist_field *create_var(struct hist_trigger_data *hist_data,
				     struct trace_event_file *file,
				     char *name, int size, const char *type)
{
	struct hist_field *var;
	int idx;

	if (find_var(hist_data, file, name) && !hist_data->remove) {
		var = ERR_PTR(-EINVAL);
		goto out;
	}

	var = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
	if (!var) {
		var = ERR_PTR(-ENOMEM);
		goto out;
	}

	idx = tracing_map_add_var(hist_data->map);
	if (idx < 0) {
		kfree(var);
		var = ERR_PTR(-EINVAL);
		goto out;
	}

	var->ref = 1;
	var->flags = HIST_FIELD_FL_VAR;
	var->var.idx = idx;
	var->var.hist_data = var->hist_data = hist_data;
	var->size = size;
	var->var.name = kstrdup(name, GFP_KERNEL);
	var->type = kstrdup_const(type, GFP_KERNEL);
	if (!var->var.name || !var->type) {
		kfree_const(var->type);
		kfree(var->var.name);
		kfree(var);
		var = ERR_PTR(-ENOMEM);
	}
 out:
	return var;
}

static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
					  struct trace_event_file *file,
					  char *field_name)
{
	struct hist_field *val = NULL, *var = NULL;
	unsigned long flags = HIST_FIELD_FL_VAR;
	struct trace_array *tr = file->tr;
	struct field_var *field_var;
	int ret = 0;

	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
		ret = -EINVAL;
		goto err;
	}

	val = parse_atom(hist_data, file, field_name, &flags, NULL);
	if (IS_ERR(val)) {
		hist_err(tr, HIST_ERR_FIELD_VAR_PARSE_FAIL, errpos(field_name));
		ret = PTR_ERR(val);
		goto err;
	}

	var = create_var(hist_data, file, field_name, val->size, val->type);
	if (IS_ERR(var)) {
		hist_err(tr, HIST_ERR_VAR_CREATE_FIND_FAIL, errpos(field_name));
		kfree(val);
		ret = PTR_ERR(var);
		goto err;
	}

	field_var = kzalloc(sizeof(struct field_var), GFP_KERNEL);
	if (!field_var) {
		kfree(val);
		kfree(var);
		ret =  -ENOMEM;
		goto err;
	}

	field_var->var = var;
	field_var->val = val;
 out:
	return field_var;
 err:
	field_var = ERR_PTR(ret);
	goto out;
}

/**
 * create_target_field_var - Automatically create a variable for a field
 * @target_hist_data: The target hist trigger
 * @subsys_name: Optional subsystem name
 * @event_name: Optional event name
 * @var_name: The name of the field (and the resulting variable)
 *
 * Hist trigger actions fetch data from variables, not directly from
 * events.  However, for convenience, users are allowed to directly
 * specify an event field in an action, which will be automatically
 * converted into a variable on their behalf.
 *
 * This function creates a field variable with the name var_name on
 * the hist trigger currently being defined on the target event.  If
 * subsys_name and event_name are specified, this function simply
 * verifies that they do in fact match the target event subsystem and
 * event name.
 *
 * Return: The variable created for the field.
 */
static struct field_var *
create_target_field_var(struct hist_trigger_data *target_hist_data,
			char *subsys_name, char *event_name, char *var_name)
{
	struct trace_event_file *file = target_hist_data->event_file;

	if (subsys_name) {
		struct trace_event_call *call;

		if (!event_name)
			return NULL;

		call = file->event_call;

		if (strcmp(subsys_name, call->class->system) != 0)
			return NULL;

		if (strcmp(event_name, trace_event_name(call)) != 0)
			return NULL;
	}

	return create_field_var(target_hist_data, file, var_name);
}

static bool check_track_val_max(u64 track_val, u64 var_val)
{
	if (var_val <= track_val)
		return false;

	return true;
}

static bool check_track_val_changed(u64 track_val, u64 var_val)
{
	if (var_val == track_val)
		return false;

	return true;
}

static u64 get_track_val(struct hist_trigger_data *hist_data,
			 struct tracing_map_elt *elt,
			 struct action_data *data)
{
	unsigned int track_var_idx = data->track_data.track_var->var.idx;
	u64 track_val;

	track_val = tracing_map_read_var(elt, track_var_idx);

	return track_val;
}

static void save_track_val(struct hist_trigger_data *hist_data,
			   struct tracing_map_elt *elt,
			   struct action_data *data, u64 var_val)
{
	unsigned int track_var_idx = data->track_data.track_var->var.idx;

	tracing_map_set_var(elt, track_var_idx, var_val);
}

static void save_track_data(struct hist_trigger_data *hist_data,
			    struct tracing_map_elt *elt,
			    struct trace_buffer *buffer, void *rec,
			    struct ring_buffer_event *rbe, void *key,
			    struct action_data *data, u64 *var_ref_vals)
{
	if (data->track_data.save_data)
		data->track_data.save_data(hist_data, elt, buffer, rec, rbe,
					   key, data, var_ref_vals);
}

static bool check_track_val(struct tracing_map_elt *elt,
			    struct action_data *data,
			    u64 var_val)
{
	struct hist_trigger_data *hist_data;
	u64 track_val;

	hist_data = data->track_data.track_var->hist_data;
	track_val = get_track_val(hist_data, elt, data);

	return data->track_data.check_val(track_val, var_val);
}

#ifdef CONFIG_TRACER_SNAPSHOT
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
	/* called with tr->max_lock held */
	struct track_data *track_data = tr->cond_snapshot->cond_data;
	struct hist_elt_data *elt_data, *track_elt_data;
	struct snapshot_context *context = cond_data;
	struct action_data *action;
	u64 track_val;

	if (!track_data)
		return false;

	action = track_data->action_data;

	track_val = get_track_val(track_data->hist_data, context->elt,
				  track_data->action_data);

	if (!action->track_data.check_val(track_data->track_val, track_val))
		return false;

	track_data->track_val = track_val;
	memcpy(track_data->key, context->key, track_data->key_len);

	elt_data = context->elt->private_data;
	track_elt_data = track_data->elt.private_data;
	if (elt_data->comm)
		strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);

	track_data->updated = true;

	return true;
}

static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
				     struct tracing_map_elt *elt,
				     struct trace_buffer *buffer, void *rec,
				     struct ring_buffer_event *rbe, void *key,
				     struct action_data *data,
				     u64 *var_ref_vals)
{
	struct trace_event_file *file = hist_data->event_file;
	struct snapshot_context context;

	context.elt = elt;
	context.key = key;

	tracing_snapshot_cond(file->tr, &context);
}

static void hist_trigger_print_key(struct seq_file *m,
				   struct hist_trigger_data *hist_data,
				   void *key,
				   struct tracing_map_elt *elt);

static struct action_data *snapshot_action(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	if (!hist_data->n_actions)
		return NULL;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];

		if (data->action == ACTION_SNAPSHOT)
			return data;
	}

	return NULL;
}

static void track_data_snapshot_print(struct seq_file *m,
				      struct hist_trigger_data *hist_data)
{
	struct trace_event_file *file = hist_data->event_file;
	struct track_data *track_data;
	struct action_data *action;

	track_data = tracing_cond_snapshot_data(file->tr);
	if (!track_data)
		return;

	if (!track_data->updated)
		return;

	action = snapshot_action(hist_data);
	if (!action)
		return;

	seq_puts(m, "\nSnapshot taken (see tracing/snapshot).  Details:\n");
	seq_printf(m, "\ttriggering value { %s(%s) }: %10llu",
		   action->handler == HANDLER_ONMAX ? "onmax" : "onchange",
		   action->track_data.var_str, track_data->track_val);

	seq_puts(m, "\ttriggered by event with key: ");
	hist_trigger_print_key(m, hist_data, track_data->key, &track_data->elt);
	seq_putc(m, '\n');
}
#else
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
	return false;
}
static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
				     struct tracing_map_elt *elt,
				     struct trace_buffer *buffer, void *rec,
				     struct ring_buffer_event *rbe, void *key,
				     struct action_data *data,
				     u64 *var_ref_vals) {}
static void track_data_snapshot_print(struct seq_file *m,
				      struct hist_trigger_data *hist_data) {}
#endif /* CONFIG_TRACER_SNAPSHOT */

static void track_data_print(struct seq_file *m,
			     struct hist_trigger_data *hist_data,
			     struct tracing_map_elt *elt,
			     struct action_data *data)
{
	u64 track_val = get_track_val(hist_data, elt, data);
	unsigned int i, save_var_idx;

	if (data->handler == HANDLER_ONMAX)
		seq_printf(m, "\n\tmax: %10llu", track_val);
	else if (data->handler == HANDLER_ONCHANGE)
		seq_printf(m, "\n\tchanged: %10llu", track_val);

	if (data->action == ACTION_SNAPSHOT)
		return;

	for (i = 0; i < hist_data->n_save_vars; i++) {
		struct hist_field *save_val = hist_data->save_vars[i]->val;
		struct hist_field *save_var = hist_data->save_vars[i]->var;
		u64 val;

		save_var_idx = save_var->var.idx;

		val = tracing_map_read_var(elt, save_var_idx);

		if (save_val->flags & HIST_FIELD_FL_STRING) {
			seq_printf(m, "  %s: %-32s", save_var->var.name,
				   (char *)(uintptr_t)(val));
		} else
			seq_printf(m, "  %s: %10llu", save_var->var.name, val);
	}
}

static void ontrack_action(struct hist_trigger_data *hist_data,
			   struct tracing_map_elt *elt,
			   struct trace_buffer *buffer, void *rec,
			   struct ring_buffer_event *rbe, void *key,
			   struct action_data *data, u64 *var_ref_vals)
{
	u64 var_val = var_ref_vals[data->track_data.var_ref->var_ref_idx];

	if (check_track_val(elt, data, var_val)) {
		save_track_val(hist_data, elt, data, var_val);
		save_track_data(hist_data, elt, buffer, rec, rbe,
				key, data, var_ref_vals);
	}
}

static void action_data_destroy(struct action_data *data)
{
	unsigned int i;

	lockdep_assert_held(&event_mutex);

	kfree(data->action_name);

	for (i = 0; i < data->n_params; i++)
		kfree(data->params[i]);

	if (data->synth_event)
		data->synth_event->ref--;

	kfree(data->synth_event_name);

	kfree(data);
}

static void track_data_destroy(struct hist_trigger_data *hist_data,
			       struct action_data *data)
{
	struct trace_event_file *file = hist_data->event_file;

	destroy_hist_field(data->track_data.track_var, 0);

	if (data->action == ACTION_SNAPSHOT) {
		struct track_data *track_data;

		track_data = tracing_cond_snapshot_data(file->tr);
		if (track_data && track_data->hist_data == hist_data) {
			tracing_snapshot_cond_disable(file->tr);
			track_data_free(track_data);
		}
	}

	kfree(data->track_data.var_str);

	action_data_destroy(data);
}

static int action_create(struct hist_trigger_data *hist_data,
			 struct action_data *data);

static int track_data_create(struct hist_trigger_data *hist_data,
			     struct action_data *data)
{
	struct hist_field *var_field, *ref_field, *track_var = NULL;
	struct trace_event_file *file = hist_data->event_file;
	struct trace_array *tr = file->tr;
	char *track_data_var_str;
	int ret = 0;

	track_data_var_str = data->track_data.var_str;
	if (track_data_var_str[0] != '$') {
		hist_err(tr, HIST_ERR_ONX_NOT_VAR, errpos(track_data_var_str));
		return -EINVAL;
	}
	track_data_var_str++;

	var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
	if (!var_field) {
		hist_err(tr, HIST_ERR_ONX_VAR_NOT_FOUND, errpos(track_data_var_str));
		return -EINVAL;
	}

	ref_field = create_var_ref(hist_data, var_field, NULL, NULL);
	if (!ref_field)
		return -ENOMEM;

	data->track_data.var_ref = ref_field;

	if (data->handler == HANDLER_ONMAX)
		track_var = create_var(hist_data, file, "__max", sizeof(u64), "u64");
	if (IS_ERR(track_var)) {
		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
		ret = PTR_ERR(track_var);
		goto out;
	}

	if (data->handler == HANDLER_ONCHANGE)
		track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
	if (IS_ERR(track_var)) {
		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
		ret = PTR_ERR(track_var);
		goto out;
	}
	data->track_data.track_var = track_var;

	ret = action_create(hist_data, data);
 out:
	return ret;
}

static int parse_action_params(struct trace_array *tr, char *params,
			       struct action_data *data)
{
	char *param, *saved_param;
	bool first_param = true;
	int ret = 0;

	while (params) {
		if (data->n_params >= SYNTH_FIELDS_MAX) {
			hist_err(tr, HIST_ERR_TOO_MANY_PARAMS, 0);
			ret = -EINVAL;
			goto out;
		}

		param = strsep(&params, ",");
		if (!param) {
			hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, 0);
			ret = -EINVAL;
			goto out;
		}

		param = strstrip(param);
		if (strlen(param) < 2) {
			hist_err(tr, HIST_ERR_INVALID_PARAM, errpos(param));
			ret = -EINVAL;
			goto out;
		}

		saved_param = kstrdup(param, GFP_KERNEL);
		if (!saved_param) {
			ret = -ENOMEM;
			goto out;
		}

		if (first_param && data->use_trace_keyword) {
			data->synth_event_name = saved_param;
			first_param = false;
			continue;
		}
		first_param = false;

		data->params[data->n_params++] = saved_param;
	}
 out:
	return ret;
}

static int action_parse(struct trace_array *tr, char *str, struct action_data *data,
			enum handler_id handler)
{
	char *action_name;
	int ret = 0;

	strsep(&str, ".");
	if (!str) {
		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
		ret = -EINVAL;
		goto out;
	}

	action_name = strsep(&str, "(");
	if (!action_name || !str) {
		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
		ret = -EINVAL;
		goto out;
	}

	if (str_has_prefix(action_name, "save")) {
		char *params = strsep(&str, ")");

		if (!params) {
			hist_err(tr, HIST_ERR_NO_SAVE_PARAMS, 0);
			ret = -EINVAL;
			goto out;
		}

		ret = parse_action_params(tr, params, data);
		if (ret)
			goto out;

		if (handler == HANDLER_ONMAX)
			data->track_data.check_val = check_track_val_max;
		else if (handler == HANDLER_ONCHANGE)
			data->track_data.check_val = check_track_val_changed;
		else {
			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
			ret = -EINVAL;
			goto out;
		}

		data->track_data.save_data = save_track_data_vars;
		data->fn = ontrack_action;
		data->action = ACTION_SAVE;
	} else if (str_has_prefix(action_name, "snapshot")) {
		char *params = strsep(&str, ")");

		if (!str) {
			hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(params));
			ret = -EINVAL;
			goto out;
		}

		if (handler == HANDLER_ONMAX)
			data->track_data.check_val = check_track_val_max;
		else if (handler == HANDLER_ONCHANGE)
			data->track_data.check_val = check_track_val_changed;
		else {
			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
			ret = -EINVAL;
			goto out;
		}

		data->track_data.save_data = save_track_data_snapshot;
		data->fn = ontrack_action;
		data->action = ACTION_SNAPSHOT;
	} else {
		char *params = strsep(&str, ")");

		if (str_has_prefix(action_name, "trace"))
			data->use_trace_keyword = true;

		if (params) {
			ret = parse_action_params(tr, params, data);
			if (ret)
				goto out;
		}

		if (handler == HANDLER_ONMAX)
			data->track_data.check_val = check_track_val_max;
		else if (handler == HANDLER_ONCHANGE)
			data->track_data.check_val = check_track_val_changed;

		if (handler != HANDLER_ONMATCH) {
			data->track_data.save_data = action_trace;
			data->fn = ontrack_action;
		} else
			data->fn = action_trace;

		data->action = ACTION_TRACE;
	}

	data->action_name = kstrdup(action_name, GFP_KERNEL);
	if (!data->action_name) {
		ret = -ENOMEM;
		goto out;
	}

	data->handler = handler;
 out:
	return ret;
}

static struct action_data *track_data_parse(struct hist_trigger_data *hist_data,
					    char *str, enum handler_id handler)
{
	struct action_data *data;
	int ret = -EINVAL;
	char *var_str;

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

	var_str = strsep(&str, ")");
	if (!var_str || !str) {
		ret = -EINVAL;
		goto free;
	}

	data->track_data.var_str = kstrdup(var_str, GFP_KERNEL);
	if (!data->track_data.var_str) {
		ret = -ENOMEM;
		goto free;
	}

	ret = action_parse(hist_data->event_file->tr, str, data, handler);
	if (ret)
		goto free;
 out:
	return data;
 free:
	track_data_destroy(hist_data, data);
	data = ERR_PTR(ret);
	goto out;
}

static void onmatch_destroy(struct action_data *data)
{
	kfree(data->match_data.event);
	kfree(data->match_data.event_system);

	action_data_destroy(data);
}

static void destroy_field_var(struct field_var *field_var)
{
	if (!field_var)
		return;

	destroy_hist_field(field_var->var, 0);
	destroy_hist_field(field_var->val, 0);

	kfree(field_var);
}

static void destroy_field_vars(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < hist_data->n_field_vars; i++)
		destroy_field_var(hist_data->field_vars[i]);

	for (i = 0; i < hist_data->n_save_vars; i++)
		destroy_field_var(hist_data->save_vars[i]);
}

static void save_field_var(struct hist_trigger_data *hist_data,
			   struct field_var *field_var)
{
	hist_data->field_vars[hist_data->n_field_vars++] = field_var;

	/* Stack traces are saved in the string storage too */
	if (field_var->val->flags & (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
		hist_data->n_field_var_str++;
}


static int check_synth_field(struct synth_event *event,
			     struct hist_field *hist_field,
			     unsigned int field_pos)
{
	struct synth_field *field;

	if (field_pos >= event->n_fields)
		return -EINVAL;

	field = event->fields[field_pos];

	/*
	 * A dynamic string synth field can accept static or
	 * dynamic. A static string synth field can only accept a
	 * same-sized static string, which is checked for later.
	 */
	if (strstr(hist_field->type, "char[") && field->is_string
	    && field->is_dynamic)
		return 0;

	if (strstr(hist_field->type, "long[") && field->is_stack)
		return 0;

	if (strcmp(field->type, hist_field->type) != 0) {
		if (field->size != hist_field->size ||
		    (!field->is_string && field->is_signed != hist_field->is_signed))
			return -EINVAL;
	}

	return 0;
}

static struct hist_field *
trace_action_find_var(struct hist_trigger_data *hist_data,
		      struct action_data *data,
		      char *system, char *event, char *var)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *hist_field;

	var++; /* skip '$' */

	hist_field = find_target_event_var(hist_data, system, event, var);
	if (!hist_field) {
		if (!system && data->handler == HANDLER_ONMATCH) {
			system = data->match_data.event_system;
			event = data->match_data.event;
		}

		hist_field = find_event_var(hist_data, system, event, var);
	}

	if (!hist_field)
		hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, errpos(var));

	return hist_field;
}

static struct hist_field *
trace_action_create_field_var(struct hist_trigger_data *hist_data,
			      struct action_data *data, char *system,
			      char *event, char *var)
{
	struct hist_field *hist_field = NULL;
	struct field_var *field_var;

	/*
	 * First try to create a field var on the target event (the
	 * currently being defined).  This will create a variable for
	 * unqualified fields on the target event, or if qualified,
	 * target fields that have qualified names matching the target.
	 */
	field_var = create_target_field_var(hist_data, system, event, var);

	if (field_var && !IS_ERR(field_var)) {
		save_field_var(hist_data, field_var);
		hist_field = field_var->var;
	} else {
		field_var = NULL;
		/*
		 * If no explicit system.event is specified, default to
		 * looking for fields on the onmatch(system.event.xxx)
		 * event.
		 */
		if (!system && data->handler == HANDLER_ONMATCH) {
			system = data->match_data.event_system;
			event = data->match_data.event;
		}

		if (!event)
			goto free;
		/*
		 * At this point, we're looking at a field on another
		 * event.  Because we can't modify a hist trigger on
		 * another event to add a variable for a field, we need
		 * to create a new trigger on that event and create the
		 * variable at the same time.
		 */
		hist_field = create_field_var_hist(hist_data, system, event, var);
		if (IS_ERR(hist_field))
			goto free;
	}
 out:
	return hist_field;
 free:
	destroy_field_var(field_var);
	hist_field = NULL;
	goto out;
}

static int trace_action_create(struct hist_trigger_data *hist_data,
			       struct action_data *data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	char *event_name, *param, *system = NULL;
	struct hist_field *hist_field, *var_ref;
	unsigned int i;
	unsigned int field_pos = 0;
	struct synth_event *event;
	char *synth_event_name;
	int var_ref_idx, ret = 0;

	lockdep_assert_held(&event_mutex);

	/* Sanity check to avoid out-of-bound write on 'data->var_ref_idx' */
	if (data->n_params > SYNTH_FIELDS_MAX)
		return -EINVAL;

	if (data->use_trace_keyword)
		synth_event_name = data->synth_event_name;
	else
		synth_event_name = data->action_name;

	event = find_synth_event(synth_event_name);
	if (!event) {
		hist_err(tr, HIST_ERR_SYNTH_EVENT_NOT_FOUND, errpos(synth_event_name));
		return -EINVAL;
	}

	event->ref++;

	for (i = 0; i < data->n_params; i++) {
		char *p;

		p = param = kstrdup(data->params[i], GFP_KERNEL);
		if (!param) {
			ret = -ENOMEM;
			goto err;
		}

		system = strsep(&param, ".");
		if (!param) {
			param = (char *)system;
			system = event_name = NULL;
		} else {
			event_name = strsep(&param, ".");
			if (!param) {
				kfree(p);
				ret = -EINVAL;
				goto err;
			}
		}

		if (param[0] == '$')
			hist_field = trace_action_find_var(hist_data, data,
							   system, event_name,
							   param);
		else
			hist_field = trace_action_create_field_var(hist_data,
								   data,
								   system,
								   event_name,
								   param);

		if (!hist_field) {
			kfree(p);
			ret = -EINVAL;
			goto err;
		}

		if (check_synth_field(event, hist_field, field_pos) == 0) {
			var_ref = create_var_ref(hist_data, hist_field,
						 system, event_name);
			if (!var_ref) {
				kfree(p);
				ret = -ENOMEM;
				goto err;
			}

			var_ref_idx = find_var_ref_idx(hist_data, var_ref);
			if (WARN_ON(var_ref_idx < 0)) {
				kfree(p);
				ret = var_ref_idx;
				goto err;
			}

			data->var_ref_idx[i] = var_ref_idx;

			field_pos++;
			kfree(p);
			continue;
		}

		hist_err(tr, HIST_ERR_SYNTH_TYPE_MISMATCH, errpos(param));
		kfree(p);
		ret = -EINVAL;
		goto err;
	}

	if (field_pos != event->n_fields) {
		hist_err(tr, HIST_ERR_SYNTH_COUNT_MISMATCH, errpos(event->name));
		ret = -EINVAL;
		goto err;
	}

	data->synth_event = event;
 out:
	return ret;
 err:
	event->ref--;

	goto out;
}

static int action_create(struct hist_trigger_data *hist_data,
			 struct action_data *data)
{
	struct trace_event_file *file = hist_data->event_file;
	struct trace_array *tr = file->tr;
	struct track_data *track_data;
	struct field_var *field_var;
	unsigned int i;
	char *param;
	int ret = 0;

	if (data->action == ACTION_TRACE)
		return trace_action_create(hist_data, data);

	if (data->action == ACTION_SNAPSHOT) {
		track_data = track_data_alloc(hist_data->key_size, data, hist_data);
		if (IS_ERR(track_data)) {
			ret = PTR_ERR(track_data);
			goto out;
		}

		ret = tracing_snapshot_cond_enable(file->tr, track_data,
						   cond_snapshot_update);
		if (ret)
			track_data_free(track_data);

		goto out;
	}

	if (data->action == ACTION_SAVE) {
		if (hist_data->n_save_vars) {
			ret = -EEXIST;
			hist_err(tr, HIST_ERR_TOO_MANY_SAVE_ACTIONS, 0);
			goto out;
		}

		for (i = 0; i < data->n_params; i++) {
			param = kstrdup(data->params[i], GFP_KERNEL);
			if (!param) {
				ret = -ENOMEM;
				goto out;
			}

			field_var = create_target_field_var(hist_data, NULL, NULL, param);
			if (IS_ERR(field_var)) {
				hist_err(tr, HIST_ERR_FIELD_VAR_CREATE_FAIL,
					 errpos(param));
				ret = PTR_ERR(field_var);
				kfree(param);
				goto out;
			}

			hist_data->save_vars[hist_data->n_save_vars++] = field_var;
			if (field_var->val->flags &
			    (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
				hist_data->n_save_var_str++;
			kfree(param);
		}
	}
 out:
	return ret;
}

static int onmatch_create(struct hist_trigger_data *hist_data,
			  struct action_data *data)
{
	return action_create(hist_data, data);
}

static struct action_data *onmatch_parse(struct trace_array *tr, char *str)
{
	char *match_event, *match_event_system;
	struct action_data *data;
	int ret = -EINVAL;

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

	match_event = strsep(&str, ")");
	if (!match_event || !str) {
		hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(match_event));
		goto free;
	}

	match_event_system = strsep(&match_event, ".");
	if (!match_event) {
		hist_err(tr, HIST_ERR_SUBSYS_NOT_FOUND, errpos(match_event_system));
		goto free;
	}

	if (IS_ERR(event_file(tr, match_event_system, match_event))) {
		hist_err(tr, HIST_ERR_INVALID_SUBSYS_EVENT, errpos(match_event));
		goto free;
	}

	data->match_data.event = kstrdup(match_event, GFP_KERNEL);
	if (!data->match_data.event) {
		ret = -ENOMEM;
		goto free;
	}

	data->match_data.event_system = kstrdup(match_event_system, GFP_KERNEL);
	if (!data->match_data.event_system) {
		ret = -ENOMEM;
		goto free;
	}

	ret = action_parse(tr, str, data, HANDLER_ONMATCH);
	if (ret)
		goto free;
 out:
	return data;
 free:
	onmatch_destroy(data);
	data = ERR_PTR(ret);
	goto out;
}

static int create_hitcount_val(struct hist_trigger_data *hist_data)
{
	hist_data->fields[HITCOUNT_IDX] =
		create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT, NULL);
	if (!hist_data->fields[HITCOUNT_IDX])
		return -ENOMEM;

	hist_data->n_vals++;
	hist_data->n_fields++;

	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
		return -EINVAL;

	return 0;
}

static int __create_val_field(struct hist_trigger_data *hist_data,
			      unsigned int val_idx,
			      struct trace_event_file *file,
			      char *var_name, char *field_str,
			      unsigned long flags)
{
	struct hist_field *hist_field;
	int ret = 0, n_subexprs = 0;

	hist_field = parse_expr(hist_data, file, field_str, flags, var_name, &n_subexprs);
	if (IS_ERR(hist_field)) {
		ret = PTR_ERR(hist_field);
		goto out;
	}

	/* values and variables should not have some modifiers */
	if (hist_field->flags & HIST_FIELD_FL_VAR) {
		/* Variable */
		if (hist_field->flags & (HIST_FIELD_FL_GRAPH | HIST_FIELD_FL_PERCENT |
					 HIST_FIELD_FL_BUCKET | HIST_FIELD_FL_LOG2))
			goto err;
	} else {
		/* Value */
		if (hist_field->flags & (HIST_FIELD_FL_GRAPH | HIST_FIELD_FL_PERCENT |
					 HIST_FIELD_FL_BUCKET | HIST_FIELD_FL_LOG2 |
					 HIST_FIELD_FL_SYM | HIST_FIELD_FL_SYM_OFFSET |
					 HIST_FIELD_FL_SYSCALL | HIST_FIELD_FL_STACKTRACE))
			goto err;
	}

	hist_data->fields[val_idx] = hist_field;

	++hist_data->n_vals;
	++hist_data->n_fields;

	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
		ret = -EINVAL;
 out:
	return ret;
 err:
	hist_err(file->tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(field_str));
	return -EINVAL;
}

static int create_val_field(struct hist_trigger_data *hist_data,
			    unsigned int val_idx,
			    struct trace_event_file *file,
			    char *field_str)
{
	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
		return -EINVAL;

	return __create_val_field(hist_data, val_idx, file, NULL, field_str, 0);
}

static const char no_comm[] = "(no comm)";

static u64 hist_field_execname(struct hist_field *hist_field,
			       struct tracing_map_elt *elt,
			       struct trace_buffer *buffer,
			       struct ring_buffer_event *rbe,
			       void *event)
{
	struct hist_elt_data *elt_data;

	if (WARN_ON_ONCE(!elt))
		return (u64)(unsigned long)no_comm;

	elt_data = elt->private_data;

	if (WARN_ON_ONCE(!elt_data->comm))
		return (u64)(unsigned long)no_comm;

	return (u64)(unsigned long)(elt_data->comm);
}

static u64 hist_field_stack(struct hist_field *hist_field,
			    struct tracing_map_elt *elt,
			    struct trace_buffer *buffer,
			    struct ring_buffer_event *rbe,
			    void *event)
{
	u32 str_item = *(u32 *)(event + hist_field->field->offset);
	int str_loc = str_item & 0xffff;
	char *addr = (char *)(event + str_loc);

	return (u64)(unsigned long)addr;
}

static u64 hist_fn_call(struct hist_field *hist_field,
			struct tracing_map_elt *elt,
			struct trace_buffer *buffer,
			struct ring_buffer_event *rbe,
			void *event)
{
	switch (hist_field->fn_num) {
	case HIST_FIELD_FN_VAR_REF:
		return hist_field_var_ref(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_COUNTER:
		return hist_field_counter(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_CONST:
		return hist_field_const(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_LOG2:
		return hist_field_log2(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_BUCKET:
		return hist_field_bucket(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_TIMESTAMP:
		return hist_field_timestamp(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_CPU:
		return hist_field_cpu(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_STRING:
		return hist_field_string(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_DYNSTRING:
		return hist_field_dynstring(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_RELDYNSTRING:
		return hist_field_reldynstring(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_PSTRING:
		return hist_field_pstring(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_S64:
		return hist_field_s64(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_U64:
		return hist_field_u64(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_S32:
		return hist_field_s32(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_U32:
		return hist_field_u32(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_S16:
		return hist_field_s16(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_U16:
		return hist_field_u16(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_S8:
		return hist_field_s8(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_U8:
		return hist_field_u8(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_UMINUS:
		return hist_field_unary_minus(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_MINUS:
		return hist_field_minus(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_PLUS:
		return hist_field_plus(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_DIV:
		return hist_field_div(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_MULT:
		return hist_field_mult(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_DIV_POWER2:
		return div_by_power_of_two(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_DIV_NOT_POWER2:
		return div_by_not_power_of_two(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_DIV_MULT_SHIFT:
		return div_by_mult_and_shift(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_EXECNAME:
		return hist_field_execname(hist_field, elt, buffer, rbe, event);
	case HIST_FIELD_FN_STACK:
		return hist_field_stack(hist_field, elt, buffer, rbe, event);
	default:
		return 0;
	}
}

/* Convert a var that points to common_pid.execname to a string */
static void update_var_execname(struct hist_field *hist_field)
{
	hist_field->flags = HIST_FIELD_FL_STRING | HIST_FIELD_FL_VAR |
		HIST_FIELD_FL_EXECNAME;
	hist_field->size = MAX_FILTER_STR_VAL;
	hist_field->is_signed = 0;

	kfree_const(hist_field->type);
	hist_field->type = "char[]";

	hist_field->fn_num = HIST_FIELD_FN_EXECNAME;
}

static int create_var_field(struct hist_trigger_data *hist_data,
			    unsigned int val_idx,
			    struct trace_event_file *file,
			    char *var_name, char *expr_str)
{
	struct trace_array *tr = hist_data->event_file->tr;
	unsigned long flags = 0;
	int ret;

	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
		return -EINVAL;

	if (find_var(hist_data, file, var_name) && !hist_data->remove) {
		hist_err(tr, HIST_ERR_DUPLICATE_VAR, errpos(var_name));
		return -EINVAL;
	}

	flags |= HIST_FIELD_FL_VAR;
	hist_data->n_vars++;
	if (WARN_ON(hist_data->n_vars > TRACING_MAP_VARS_MAX))
		return -EINVAL;

	ret = __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags);

	if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME)
		update_var_execname(hist_data->fields[val_idx]);

	if (!ret && hist_data->fields[val_idx]->flags &
	    (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
		hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++;

	return ret;
}

static int create_val_fields(struct hist_trigger_data *hist_data,
			     struct trace_event_file *file)
{
	unsigned int i, j = 1, n_hitcount = 0;
	char *fields_str, *field_str;
	int ret;

	ret = create_hitcount_val(hist_data);
	if (ret)
		goto out;

	fields_str = hist_data->attrs->vals_str;
	if (!fields_str)
		goto out;

	for (i = 0, j = 1; i < TRACING_MAP_VALS_MAX &&
		     j < TRACING_MAP_VALS_MAX; i++) {
		field_str = strsep(&fields_str, ",");
		if (!field_str)
			break;

		if (strcmp(field_str, "hitcount") == 0) {
			if (!n_hitcount++)
				continue;
		}

		ret = create_val_field(hist_data, j++, file, field_str);
		if (ret)
			goto out;
	}

	if (fields_str && (strcmp(fields_str, "hitcount") != 0))
		ret = -EINVAL;
 out:
	/* There is only raw hitcount but nohitcount suppresses it. */
	if (j == 1 && hist_data->attrs->no_hitcount) {
		hist_err(hist_data->event_file->tr, HIST_ERR_NEED_NOHC_VAL, 0);
		ret = -ENOENT;
	}

	return ret;
}

static int create_key_field(struct hist_trigger_data *hist_data,
			    unsigned int key_idx,
			    unsigned int key_offset,
			    struct trace_event_file *file,
			    char *field_str)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct hist_field *hist_field = NULL;
	unsigned long flags = 0;
	unsigned int key_size;
	int ret = 0, n_subexprs = 0;

	if (WARN_ON(key_idx >= HIST_FIELDS_MAX))
		return -EINVAL;

	flags |= HIST_FIELD_FL_KEY;

	if (strcmp(field_str, "stacktrace") == 0) {
		flags |= HIST_FIELD_FL_STACKTRACE;
		key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
		hist_field = create_hist_field(hist_data, NULL, flags, NULL);
	} else {
		hist_field = parse_expr(hist_data, file, field_str, flags,
					NULL, &n_subexprs);
		if (IS_ERR(hist_field)) {
			ret = PTR_ERR(hist_field);
			goto out;
		}

		if (field_has_hist_vars(hist_field, 0))	{
			hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field_str));
			destroy_hist_field(hist_field, 0);
			ret = -EINVAL;
			goto out;
		}

		key_size = hist_field->size;
	}

	hist_data->fields[key_idx] = hist_field;

	key_size = ALIGN(key_size, sizeof(u64));
	hist_data->fields[key_idx]->size = key_size;
	hist_data->fields[key_idx]->offset = key_offset;

	hist_data->key_size += key_size;

	if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
		ret = -EINVAL;
		goto out;
	}

	hist_data->n_keys++;
	hist_data->n_fields++;

	if (WARN_ON(hist_data->n_keys > TRACING_MAP_KEYS_MAX))
		return -EINVAL;

	ret = key_size;
 out:
	return ret;
}

static int create_key_fields(struct hist_trigger_data *hist_data,
			     struct trace_event_file *file)
{
	unsigned int i, key_offset = 0, n_vals = hist_data->n_vals;
	char *fields_str, *field_str;
	int ret = -EINVAL;

	fields_str = hist_data->attrs->keys_str;
	if (!fields_str)
		goto out;

	for (i = n_vals; i < n_vals + TRACING_MAP_KEYS_MAX; i++) {
		field_str = strsep(&fields_str, ",");
		if (!field_str)
			break;
		ret = create_key_field(hist_data, i, key_offset,
				       file, field_str);
		if (ret < 0)
			goto out;
		key_offset += ret;
	}
	if (fields_str) {
		ret = -EINVAL;
		goto out;
	}
	ret = 0;
 out:
	return ret;
}

static int create_var_fields(struct hist_trigger_data *hist_data,
			     struct trace_event_file *file)
{
	unsigned int i, j = hist_data->n_vals;
	int ret = 0;

	unsigned int n_vars = hist_data->attrs->var_defs.n_vars;

	for (i = 0; i < n_vars; i++) {
		char *var_name = hist_data->attrs->var_defs.name[i];
		char *expr = hist_data->attrs->var_defs.expr[i];

		ret = create_var_field(hist_data, j++, file, var_name, expr);
		if (ret)
			goto out;
	}
 out:
	return ret;
}

static void free_var_defs(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
		kfree(hist_data->attrs->var_defs.name[i]);
		kfree(hist_data->attrs->var_defs.expr[i]);
	}

	hist_data->attrs->var_defs.n_vars = 0;
}

static int parse_var_defs(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	char *s, *str, *var_name, *field_str;
	unsigned int i, j, n_vars = 0;
	int ret = 0;

	for (i = 0; i < hist_data->attrs->n_assignments; i++) {
		str = hist_data->attrs->assignment_str[i];
		for (j = 0; j < TRACING_MAP_VARS_MAX; j++) {
			field_str = strsep(&str, ",");
			if (!field_str)
				break;

			var_name = strsep(&field_str, "=");
			if (!var_name || !field_str) {
				hist_err(tr, HIST_ERR_MALFORMED_ASSIGNMENT,
					 errpos(var_name));
				ret = -EINVAL;
				goto free;
			}

			if (n_vars == TRACING_MAP_VARS_MAX) {
				hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(var_name));
				ret = -EINVAL;
				goto free;
			}

			s = kstrdup(var_name, GFP_KERNEL);
			if (!s) {
				ret = -ENOMEM;
				goto free;
			}
			hist_data->attrs->var_defs.name[n_vars] = s;

			s = kstrdup(field_str, GFP_KERNEL);
			if (!s) {
				kfree(hist_data->attrs->var_defs.name[n_vars]);
				hist_data->attrs->var_defs.name[n_vars] = NULL;
				ret = -ENOMEM;
				goto free;
			}
			hist_data->attrs->var_defs.expr[n_vars++] = s;

			hist_data->attrs->var_defs.n_vars = n_vars;
		}
	}

	return ret;
 free:
	free_var_defs(hist_data);

	return ret;
}

static int create_hist_fields(struct hist_trigger_data *hist_data,
			      struct trace_event_file *file)
{
	int ret;

	ret = parse_var_defs(hist_data);
	if (ret)
		return ret;

	ret = create_val_fields(hist_data, file);
	if (ret)
		goto out;

	ret = create_var_fields(hist_data, file);
	if (ret)
		goto out;

	ret = create_key_fields(hist_data, file);

 out:
	free_var_defs(hist_data);

	return ret;
}

static int is_descending(struct trace_array *tr, const char *str)
{
	if (!str)
		return 0;

	if (strcmp(str, "descending") == 0)
		return 1;

	if (strcmp(str, "ascending") == 0)
		return 0;

	hist_err(tr, HIST_ERR_INVALID_SORT_MODIFIER, errpos((char *)str));

	return -EINVAL;
}

static int create_sort_keys(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	char *fields_str = hist_data->attrs->sort_key_str;
	struct tracing_map_sort_key *sort_key;
	int descending, ret = 0;
	unsigned int i, j, k;

	hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */

	if (!fields_str)
		goto out;

	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
		struct hist_field *hist_field;
		char *field_str, *field_name;
		const char *test_name;

		sort_key = &hist_data->sort_keys[i];

		field_str = strsep(&fields_str, ",");
		if (!field_str)
			break;

		if (!*field_str) {
			ret = -EINVAL;
			hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
			break;
		}

		if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
			hist_err(tr, HIST_ERR_TOO_MANY_SORT_FIELDS, errpos("sort="));
			ret = -EINVAL;
			break;
		}

		field_name = strsep(&field_str, ".");
		if (!field_name || !*field_name) {
			ret = -EINVAL;
			hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
			break;
		}

		if (strcmp(field_name, "hitcount") == 0) {
			descending = is_descending(tr, field_str);
			if (descending < 0) {
				ret = descending;
				break;
			}
			sort_key->descending = descending;
			continue;
		}

		for (j = 1, k = 1; j < hist_data->n_fields; j++) {
			unsigned int idx;

			hist_field = hist_data->fields[j];
			if (hist_field->flags & HIST_FIELD_FL_VAR)
				continue;

			idx = k++;

			test_name = hist_field_name(hist_field, 0);

			if (strcmp(field_name, test_name) == 0) {
				sort_key->field_idx = idx;
				descending = is_descending(tr, field_str);
				if (descending < 0) {
					ret = descending;
					goto out;
				}
				sort_key->descending = descending;
				break;
			}
		}
		if (j == hist_data->n_fields) {
			ret = -EINVAL;
			hist_err(tr, HIST_ERR_INVALID_SORT_FIELD, errpos(field_name));
			break;
		}
	}

	hist_data->n_sort_keys = i;
 out:
	return ret;
}

static void destroy_actions(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];

		if (data->handler == HANDLER_ONMATCH)
			onmatch_destroy(data);
		else if (data->handler == HANDLER_ONMAX ||
			 data->handler == HANDLER_ONCHANGE)
			track_data_destroy(hist_data, data);
		else
			kfree(data);
	}
}

static int parse_actions(struct hist_trigger_data *hist_data)
{
	struct trace_array *tr = hist_data->event_file->tr;
	struct action_data *data;
	unsigned int i;
	int ret = 0;
	char *str;
	int len;

	for (i = 0; i < hist_data->attrs->n_actions; i++) {
		str = hist_data->attrs->action_str[i];

		if ((len = str_has_prefix(str, "onmatch("))) {
			char *action_str = str + len;

			data = onmatch_parse(tr, action_str);
			if (IS_ERR(data)) {
				ret = PTR_ERR(data);
				break;
			}
		} else if ((len = str_has_prefix(str, "onmax("))) {
			char *action_str = str + len;

			data = track_data_parse(hist_data, action_str,
						HANDLER_ONMAX);
			if (IS_ERR(data)) {
				ret = PTR_ERR(data);
				break;
			}
		} else if ((len = str_has_prefix(str, "onchange("))) {
			char *action_str = str + len;

			data = track_data_parse(hist_data, action_str,
						HANDLER_ONCHANGE);
			if (IS_ERR(data)) {
				ret = PTR_ERR(data);
				break;
			}
		} else {
			ret = -EINVAL;
			break;
		}

		hist_data->actions[hist_data->n_actions++] = data;
	}

	return ret;
}

static int create_actions(struct hist_trigger_data *hist_data)
{
	struct action_data *data;
	unsigned int i;
	int ret = 0;

	for (i = 0; i < hist_data->attrs->n_actions; i++) {
		data = hist_data->actions[i];

		if (data->handler == HANDLER_ONMATCH) {
			ret = onmatch_create(hist_data, data);
			if (ret)
				break;
		} else if (data->handler == HANDLER_ONMAX ||
			   data->handler == HANDLER_ONCHANGE) {
			ret = track_data_create(hist_data, data);
			if (ret)
				break;
		} else {
			ret = -EINVAL;
			break;
		}
	}

	return ret;
}

static void print_actions(struct seq_file *m,
			  struct hist_trigger_data *hist_data,
			  struct tracing_map_elt *elt)
{
	unsigned int i;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];

		if (data->action == ACTION_SNAPSHOT)
			continue;

		if (data->handler == HANDLER_ONMAX ||
		    data->handler == HANDLER_ONCHANGE)
			track_data_print(m, hist_data, elt, data);
	}
}

static void print_action_spec(struct seq_file *m,
			      struct hist_trigger_data *hist_data,
			      struct action_data *data)
{
	unsigned int i;

	if (data->action == ACTION_SAVE) {
		for (i = 0; i < hist_data->n_save_vars; i++) {
			seq_printf(m, "%s", hist_data->save_vars[i]->var->var.name);
			if (i < hist_data->n_save_vars - 1)
				seq_puts(m, ",");
		}
	} else if (data->action == ACTION_TRACE) {
		if (data->use_trace_keyword)
			seq_printf(m, "%s", data->synth_event_name);
		for (i = 0; i < data->n_params; i++) {
			if (i || data->use_trace_keyword)
				seq_puts(m, ",");
			seq_printf(m, "%s", data->params[i]);
		}
	}
}

static void print_track_data_spec(struct seq_file *m,
				  struct hist_trigger_data *hist_data,
				  struct action_data *data)
{
	if (data->handler == HANDLER_ONMAX)
		seq_puts(m, ":onmax(");
	else if (data->handler == HANDLER_ONCHANGE)
		seq_puts(m, ":onchange(");
	seq_printf(m, "%s", data->track_data.var_str);
	seq_printf(m, ").%s(", data->action_name);

	print_action_spec(m, hist_data, data);

	seq_puts(m, ")");
}

static void print_onmatch_spec(struct seq_file *m,
			       struct hist_trigger_data *hist_data,
			       struct action_data *data)
{
	seq_printf(m, ":onmatch(%s.%s).", data->match_data.event_system,
		   data->match_data.event);

	seq_printf(m, "%s(", data->action_name);

	print_action_spec(m, hist_data, data);

	seq_puts(m, ")");
}

static bool actions_match(struct hist_trigger_data *hist_data,
			  struct hist_trigger_data *hist_data_test)
{
	unsigned int i, j;

	if (hist_data->n_actions != hist_data_test->n_actions)
		return false;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];
		struct action_data *data_test = hist_data_test->actions[i];
		char *action_name, *action_name_test;

		if (data->handler != data_test->handler)
			return false;
		if (data->action != data_test->action)
			return false;

		if (data->n_params != data_test->n_params)
			return false;

		for (j = 0; j < data->n_params; j++) {
			if (strcmp(data->params[j], data_test->params[j]) != 0)
				return false;
		}

		if (data->use_trace_keyword)
			action_name = data->synth_event_name;
		else
			action_name = data->action_name;

		if (data_test->use_trace_keyword)
			action_name_test = data_test->synth_event_name;
		else
			action_name_test = data_test->action_name;

		if (strcmp(action_name, action_name_test) != 0)
			return false;

		if (data->handler == HANDLER_ONMATCH) {
			if (strcmp(data->match_data.event_system,
				   data_test->match_data.event_system) != 0)
				return false;
			if (strcmp(data->match_data.event,
				   data_test->match_data.event) != 0)
				return false;
		} else if (data->handler == HANDLER_ONMAX ||
			   data->handler == HANDLER_ONCHANGE) {
			if (strcmp(data->track_data.var_str,
				   data_test->track_data.var_str) != 0)
				return false;
		}
	}

	return true;
}


static void print_actions_spec(struct seq_file *m,
			       struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *data = hist_data->actions[i];

		if (data->handler == HANDLER_ONMATCH)
			print_onmatch_spec(m, hist_data, data);
		else if (data->handler == HANDLER_ONMAX ||
			 data->handler == HANDLER_ONCHANGE)
			print_track_data_spec(m, hist_data, data);
	}
}

static void destroy_field_var_hists(struct hist_trigger_data *hist_data)
{
	unsigned int i;

	for (i = 0; i < hist_data->n_field_var_hists; i++) {
		kfree(hist_data->field_var_hists[i]->cmd);
		kfree(hist_data->field_var_hists[i]);
	}
}

static void destroy_hist_data(struct hist_trigger_data *hist_data)
{
	if (!hist_data)
		return;

	destroy_hist_trigger_attrs(hist_data->attrs);
	destroy_hist_fields(hist_data);
	tracing_map_destroy(hist_data->map);

	destroy_actions(hist_data);
	destroy_field_vars(hist_data);
	destroy_field_var_hists(hist_data);

	kfree(hist_data);
}

static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
{
	struct tracing_map *map = hist_data->map;
	struct ftrace_event_field *field;
	struct hist_field *hist_field;
	int i, idx = 0;

	for_each_hist_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		if (hist_field->flags & HIST_FIELD_FL_KEY) {
			tracing_map_cmp_fn_t cmp_fn;

			field = hist_field->field;

			if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
				cmp_fn = tracing_map_cmp_none;
			else if (!field || hist_field->flags & HIST_FIELD_FL_CPU)
				cmp_fn = tracing_map_cmp_num(hist_field->size,
							     hist_field->is_signed);
			else if (is_string_field(field))
				cmp_fn = tracing_map_cmp_string;
			else
				cmp_fn = tracing_map_cmp_num(field->size,
							     field->is_signed);
			idx = tracing_map_add_key_field(map,
							hist_field->offset,
							cmp_fn);
		} else if (!(hist_field->flags & HIST_FIELD_FL_VAR))
			idx = tracing_map_add_sum_field(map);

		if (idx < 0)
			return idx;

		if (hist_field->flags & HIST_FIELD_FL_VAR) {
			idx = tracing_map_add_var(map);
			if (idx < 0)
				return idx;
			hist_field->var.idx = idx;
			hist_field->var.hist_data = hist_data;
		}
	}

	return 0;
}

static struct hist_trigger_data *
create_hist_data(unsigned int map_bits,
		 struct hist_trigger_attrs *attrs,
		 struct trace_event_file *file,
		 bool remove)
{
	const struct tracing_map_ops *map_ops = NULL;
	struct hist_trigger_data *hist_data;
	int ret = 0;

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

	hist_data->attrs = attrs;
	hist_data->remove = remove;
	hist_data->event_file = file;

	ret = parse_actions(hist_data);
	if (ret)
		goto free;

	ret = create_hist_fields(hist_data, file);
	if (ret)
		goto free;

	ret = create_sort_keys(hist_data);
	if (ret)
		goto free;

	map_ops = &hist_trigger_elt_data_ops;

	hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
					    map_ops, hist_data);
	if (IS_ERR(hist_data->map)) {
		ret = PTR_ERR(hist_data->map);
		hist_data->map = NULL;
		goto free;
	}

	ret = create_tracing_map_fields(hist_data);
	if (ret)
		goto free;
 out:
	return hist_data;
 free:
	hist_data->attrs = NULL;

	destroy_hist_data(hist_data);

	hist_data = ERR_PTR(ret);

	goto out;
}

static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
				    struct tracing_map_elt *elt,
				    struct trace_buffer *buffer, void *rec,
				    struct ring_buffer_event *rbe,
				    u64 *var_ref_vals)
{
	struct hist_elt_data *elt_data;
	struct hist_field *hist_field;
	unsigned int i, var_idx;
	u64 hist_val;

	elt_data = elt->private_data;
	elt_data->var_ref_vals = var_ref_vals;

	for_each_hist_val_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		hist_val = hist_fn_call(hist_field, elt, buffer, rbe, rec);
		if (hist_field->flags & HIST_FIELD_FL_VAR) {
			var_idx = hist_field->var.idx;

			if (hist_field->flags &
			    (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE)) {
				unsigned int str_start, var_str_idx, idx;
				char *str, *val_str;
				unsigned int size;

				str_start = hist_data->n_field_var_str +
					hist_data->n_save_var_str;
				var_str_idx = hist_field->var_str_idx;
				idx = str_start + var_str_idx;

				str = elt_data->field_var_str[idx];
				val_str = (char *)(uintptr_t)hist_val;

				if (hist_field->flags & HIST_FIELD_FL_STRING) {
					size = min(hist_field->size, STR_VAR_LEN_MAX);
					strscpy(str, val_str, size);
				} else {
					char *stack_start = str + sizeof(unsigned long);
					int e;

					e = stack_trace_save((void *)stack_start,
							     HIST_STACKTRACE_DEPTH,
							     HIST_STACKTRACE_SKIP);
					if (e < HIST_STACKTRACE_DEPTH - 1)
						((unsigned long *)stack_start)[e] = 0;
					*((unsigned long *)str) = e;
				}
				hist_val = (u64)(uintptr_t)str;
			}
			tracing_map_set_var(elt, var_idx, hist_val);
			continue;
		}
		tracing_map_update_sum(elt, i, hist_val);
	}

	for_each_hist_key_field(i, hist_data) {
		hist_field = hist_data->fields[i];
		if (hist_field->flags & HIST_FIELD_FL_VAR) {
			hist_val = hist_fn_call(hist_field, elt, buffer, rbe, rec);
			var_idx = hist_field->var.idx;
			tracing_map_set_var(elt, var_idx, hist_val);
		}
	}

	update_field_vars(hist_data, elt, buffer, rbe, rec);
}

static inline void add_to_key(char *compound_key, void *key,
			      struct hist_field *key_field, void *rec)
{
	size_t size = key_field->size;

	if (key_field->flags & HIST_FIELD_FL_STRING) {
		struct ftrace_event_field *field;

		field = key_field->field;
		if (field->filter_type == FILTER_DYN_STRING ||
		    field->filter_type == FILTER_RDYN_STRING)
			size = *(u32 *)(rec + field->offset) >> 16;
		else if (field->filter_type == FILTER_STATIC_STRING)
			size = field->size;

		/* ensure NULL-termination */
		if (size > key_field->size - 1)
			size = key_field->size - 1;

		strncpy(compound_key + key_field->offset, (char *)key, size);
	} else
		memcpy(compound_key + key_field->offset, key, size);
}

static void
hist_trigger_actions(struct hist_trigger_data *hist_data,
		     struct tracing_map_elt *elt,
		     struct trace_buffer *buffer, void *rec,
		     struct ring_buffer_event *rbe, void *key,
		     u64 *var_ref_vals)
{
	struct action_data *data;
	unsigned int i;

	for (i = 0; i < hist_data->n_actions; i++) {
		data = hist_data->actions[i];
		data->fn(hist_data, elt, buffer, rec, rbe, key, data, var_ref_vals);
	}
}

static void event_hist_trigger(struct event_trigger_data *data,
			       struct trace_buffer *buffer, void *rec,
			       struct ring_buffer_event *rbe)
{
	struct hist_trigger_data *hist_data = data->private_data;
	bool use_compound_key = (hist_data->n_keys > 1);
	unsigned long entries[HIST_STACKTRACE_DEPTH];
	u64 var_ref_vals[TRACING_MAP_VARS_MAX];
	char compound_key[HIST_KEY_SIZE_MAX];
	struct tracing_map_elt *elt = NULL;
	struct hist_field *key_field;
	u64 field_contents;
	void *key = NULL;
	unsigned int i;

	if (unlikely(!rbe))
		return;

	memset(compound_key, 0, hist_data->key_size);

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];

		if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
			memset(entries, 0, HIST_STACKTRACE_SIZE);
			if (key_field->field) {
				unsigned long *stack, n_entries;

				field_contents = hist_fn_call(key_field, elt, buffer, rbe, rec);
				stack = (unsigned long *)(long)field_contents;
				n_entries = *stack;
				memcpy(entries, ++stack, n_entries * sizeof(unsigned long));
			} else {
				stack_trace_save(entries, HIST_STACKTRACE_DEPTH,
						 HIST_STACKTRACE_SKIP);
			}
			key = entries;
		} else {
			field_contents = hist_fn_call(key_field, elt, buffer, rbe, rec);
			if (key_field->flags & HIST_FIELD_FL_STRING) {
				key = (void *)(unsigned long)field_contents;
				use_compound_key = true;
			} else
				key = (void *)&field_contents;
		}

		if (use_compound_key)
			add_to_key(compound_key, key, key_field, rec);
	}

	if (use_compound_key)
		key = compound_key;

	if (hist_data->n_var_refs &&
	    !resolve_var_refs(hist_data, key, var_ref_vals, false))
		return;

	elt = tracing_map_insert(hist_data->map, key);
	if (!elt)
		return;

	hist_trigger_elt_update(hist_data, elt, buffer, rec, rbe, var_ref_vals);

	if (resolve_var_refs(hist_data, key, var_ref_vals, true))
		hist_trigger_actions(hist_data, elt, buffer, rec, rbe, key, var_ref_vals);
}

static void hist_trigger_stacktrace_print(struct seq_file *m,
					  unsigned long *stacktrace_entries,
					  unsigned int max_entries)
{
	unsigned int spaces = 8;
	unsigned int i;

	for (i = 0; i < max_entries; i++) {
		if (!stacktrace_entries[i])
			return;

		seq_printf(m, "%*c", 1 + spaces, ' ');
		seq_printf(m, "%pS\n", (void*)stacktrace_entries[i]);
	}
}

static void hist_trigger_print_key(struct seq_file *m,
				   struct hist_trigger_data *hist_data,
				   void *key,
				   struct tracing_map_elt *elt)
{
	struct hist_field *key_field;
	bool multiline = false;
	const char *field_name;
	unsigned int i;
	u64 uval;

	seq_puts(m, "{ ");

	for_each_hist_key_field(i, hist_data) {
		key_field = hist_data->fields[i];

		if (i > hist_data->n_vals)
			seq_puts(m, ", ");

		field_name = hist_field_name(key_field, 0);

		if (key_field->flags & HIST_FIELD_FL_HEX) {
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: %llx", field_name, uval);
		} else if (key_field->flags & HIST_FIELD_FL_SYM) {
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: [%llx] %-45ps", field_name,
				   uval, (void *)(uintptr_t)uval);
		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: [%llx] %-55pS", field_name,
				   uval, (void *)(uintptr_t)uval);
		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
			struct hist_elt_data *elt_data = elt->private_data;
			char *comm;

			if (WARN_ON_ONCE(!elt_data))
				return;

			comm = elt_data->comm;

			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: %-16s[%10llu]", field_name,
				   comm, uval);
		} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
			const char *syscall_name;

			uval = *(u64 *)(key + key_field->offset);
			syscall_name = get_syscall_name(uval);
			if (!syscall_name)
				syscall_name = "unknown_syscall";

			seq_printf(m, "%s: %-30s[%3llu]", field_name,
				   syscall_name, uval);
		} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
			if (key_field->field)
				seq_printf(m, "%s.stacktrace", key_field->field->name);
			else
				seq_puts(m, "common_stacktrace:\n");
			hist_trigger_stacktrace_print(m,
						      key + key_field->offset,
						      HIST_STACKTRACE_DEPTH);
			multiline = true;
		} else if (key_field->flags & HIST_FIELD_FL_LOG2) {
			seq_printf(m, "%s: ~ 2^%-2llu", field_name,
				   *(u64 *)(key + key_field->offset));
		} else if (key_field->flags & HIST_FIELD_FL_BUCKET) {
			unsigned long buckets = key_field->buckets;
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: ~ %llu-%llu", field_name,
				   uval, uval + buckets -1);
		} else if (key_field->flags & HIST_FIELD_FL_STRING) {
			seq_printf(m, "%s: %-50s", field_name,
				   (char *)(key + key_field->offset));
		} else {
			uval = *(u64 *)(key + key_field->offset);
			seq_printf(m, "%s: %10llu", field_name, uval);
		}
	}

	if (!multiline)
		seq_puts(m, " ");

	seq_puts(m, "}");
}

/* Get the 100 times of the percentage of @val in @total */
static inline unsigned int __get_percentage(u64 val, u64 total)
{
	if (!total)
		goto div0;

	if (val < (U64_MAX / 10000))
		return (unsigned int)div64_ul(val * 10000, total);

	total = div64_u64(total, 10000);
	if (!total)
		goto div0;

	return (unsigned int)div64_ul(val, total);
div0:
	return val ? UINT_MAX : 0;
}

#define BAR_CHAR '#'

static inline const char *__fill_bar_str(char *buf, int size, u64 val, u64 max)
{
	unsigned int len = __get_percentage(val, max);
	int i;

	if (len == UINT_MAX) {
		snprintf(buf, size, "[ERROR]");
		return buf;
	}

	len = len * size / 10000;
	for (i = 0; i < len && i < size; i++)
		buf[i] = BAR_CHAR;
	while (i < size)
		buf[i++] = ' ';
	buf[size] = '\0';

	return buf;
}

struct hist_val_stat {
	u64 max;
	u64 total;
};

static void hist_trigger_print_val(struct seq_file *m, unsigned int idx,
				   const char *field_name, unsigned long flags,
				   struct hist_val_stat *stats,
				   struct tracing_map_elt *elt)
{
	u64 val = tracing_map_read_sum(elt, idx);
	unsigned int pc;
	char bar[21];

	if (flags & HIST_FIELD_FL_PERCENT) {
		pc = __get_percentage(val, stats[idx].total);
		if (pc == UINT_MAX)
			seq_printf(m, " %s (%%):[ERROR]", field_name);
		else
			seq_printf(m, " %s (%%): %3u.%02u", field_name,
					pc / 100, pc % 100);
	} else if (flags & HIST_FIELD_FL_GRAPH) {
		seq_printf(m, " %s: %20s", field_name,
			   __fill_bar_str(bar, 20, val, stats[idx].max));
	} else if (flags & HIST_FIELD_FL_HEX) {
		seq_printf(m, " %s: %10llx", field_name, val);
	} else {
		seq_printf(m, " %s: %10llu", field_name, val);
	}
}

static void hist_trigger_entry_print(struct seq_file *m,
				     struct hist_trigger_data *hist_data,
				     struct hist_val_stat *stats,
				     void *key,
				     struct tracing_map_elt *elt)
{
	const char *field_name;
	unsigned int i = HITCOUNT_IDX;
	unsigned long flags;

	hist_trigger_print_key(m, hist_data, key, elt);

	/* At first, show the raw hitcount if !nohitcount */
	if (!hist_data->attrs->no_hitcount)
		hist_trigger_print_val(m, i, "hitcount", 0, stats, elt);

	for (i = 1; i < hist_data->n_vals; i++) {
		field_name = hist_field_name(hist_data->fields[i], 0);
		flags = hist_data->fields[i]->flags;
		if (flags & HIST_FIELD_FL_VAR || flags & HIST_FIELD_FL_EXPR)
			continue;

		seq_puts(m, " ");
		hist_trigger_print_val(m, i, field_name, flags, stats, elt);
	}

	print_actions(m, hist_data, elt);

	seq_puts(m, "\n");
}

static int print_entries(struct seq_file *m,
			 struct hist_trigger_data *hist_data)
{
	struct tracing_map_sort_entry **sort_entries = NULL;
	struct tracing_map *map = hist_data->map;
	int i, j, n_entries;
	struct hist_val_stat *stats = NULL;
	u64 val;

	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
					     hist_data->n_sort_keys,
					     &sort_entries);
	if (n_entries < 0)
		return n_entries;

	/* Calculate the max and the total for each field if needed. */
	for (j = 0; j < hist_data->n_vals; j++) {
		if (!(hist_data->fields[j]->flags &
			(HIST_FIELD_FL_PERCENT | HIST_FIELD_FL_GRAPH)))
			continue;
		if (!stats) {
			stats = kcalloc(hist_data->n_vals, sizeof(*stats),
				       GFP_KERNEL);
			if (!stats) {
				n_entries = -ENOMEM;
				goto out;
			}
		}
		for (i = 0; i < n_entries; i++) {
			val = tracing_map_read_sum(sort_entries[i]->elt, j);
			stats[j].total += val;
			if (stats[j].max < val)
				stats[j].max = val;
		}
	}

	for (i = 0; i < n_entries; i++)
		hist_trigger_entry_print(m, hist_data, stats,
					 sort_entries[i]->key,
					 sort_entries[i]->elt);

	kfree(stats);
out:
	tracing_map_destroy_sort_entries(sort_entries, n_entries);

	return n_entries;
}

static void hist_trigger_show(struct seq_file *m,
			      struct event_trigger_data *data, int n)
{
	struct hist_trigger_data *hist_data;
	int n_entries;

	if (n > 0)
		seq_puts(m, "\n\n");

	seq_puts(m, "# event histogram\n#\n# trigger info: ");
	data->ops->print(m, data);
	seq_puts(m, "#\n\n");

	hist_data = data->private_data;
	n_entries = print_entries(m, hist_data);
	if (n_entries < 0)
		n_entries = 0;

	track_data_snapshot_print(m, hist_data);

	seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n",
		   (u64)atomic64_read(&hist_data->map->hits),
		   n_entries, (u64)atomic64_read(&hist_data->map->drops));
}

static int hist_show(struct seq_file *m, void *v)
{
	struct event_trigger_data *data;
	struct trace_event_file *event_file;
	int n = 0, ret = 0;

	mutex_lock(&event_mutex);

	event_file = event_file_data(m->private);
	if (unlikely(!event_file)) {
		ret = -ENODEV;
		goto out_unlock;
	}

	list_for_each_entry(data, &event_file->triggers, list) {
		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
			hist_trigger_show(m, data, n++);
	}

 out_unlock:
	mutex_unlock(&event_mutex);

	return ret;
}

static int event_hist_open(struct inode *inode, struct file *file)
{
	int ret;

	ret = security_locked_down(LOCKDOWN_TRACEFS);
	if (ret)
		return ret;

	return single_open(file, hist_show, file);
}

const struct file_operations event_hist_fops = {
	.open = event_hist_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

#ifdef CONFIG_HIST_TRIGGERS_DEBUG
static void hist_field_debug_show_flags(struct seq_file *m,
					unsigned long flags)
{
	seq_puts(m, "      flags:\n");

	if (flags & HIST_FIELD_FL_KEY)
		seq_puts(m, "        HIST_FIELD_FL_KEY\n");
	else if (flags & HIST_FIELD_FL_HITCOUNT)
		seq_puts(m, "        VAL: HIST_FIELD_FL_HITCOUNT\n");
	else if (flags & HIST_FIELD_FL_VAR)
		seq_puts(m, "        HIST_FIELD_FL_VAR\n");
	else if (flags & HIST_FIELD_FL_VAR_REF)
		seq_puts(m, "        HIST_FIELD_FL_VAR_REF\n");
	else
		seq_puts(m, "        VAL: normal u64 value\n");

	if (flags & HIST_FIELD_FL_ALIAS)
		seq_puts(m, "        HIST_FIELD_FL_ALIAS\n");
	else if (flags & HIST_FIELD_FL_CONST)
		seq_puts(m, "        HIST_FIELD_FL_CONST\n");
}

static int hist_field_debug_show(struct seq_file *m,
				 struct hist_field *field, unsigned long flags)
{
	if ((field->flags & flags) != flags) {
		seq_printf(m, "ERROR: bad flags - %lx\n", flags);
		return -EINVAL;
	}

	hist_field_debug_show_flags(m, field->flags);
	if (field->field)
		seq_printf(m, "      ftrace_event_field name: %s\n",
			   field->field->name);

	if (field->flags & HIST_FIELD_FL_VAR) {
		seq_printf(m, "      var.name: %s\n", field->var.name);
		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
			   field->var.idx);
	}

	if (field->flags & HIST_FIELD_FL_CONST)
		seq_printf(m, "      constant: %llu\n", field->constant);

	if (field->flags & HIST_FIELD_FL_ALIAS)
		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",
			   field->var_ref_idx);

	if (field->flags & HIST_FIELD_FL_VAR_REF) {
		seq_printf(m, "      name: %s\n", field->name);
		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
			   field->var.idx);
		seq_printf(m, "      var.hist_data: %p\n", field->var.hist_data);
		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",
			   field->var_ref_idx);
		if (field->system)
			seq_printf(m, "      system: %s\n", field->system);
		if (field->event_name)
			seq_printf(m, "      event_name: %s\n", field->event_name);
	}

	seq_printf(m, "      type: %s\n", field->type);
	seq_printf(m, "      size: %u\n", field->size);
	seq_printf(m, "      is_signed: %u\n", field->is_signed);

	return 0;
}

static int field_var_debug_show(struct seq_file *m,
				struct field_var *field_var, unsigned int i,
				bool save_vars)
{
	const char *vars_name = save_vars ? "save_vars" : "field_vars";
	struct hist_field *field;
	int ret = 0;

	seq_printf(m, "\n    hist_data->%s[%d]:\n", vars_name, i);

	field = field_var->var;

	seq_printf(m, "\n      %s[%d].var:\n", vars_name, i);

	hist_field_debug_show_flags(m, field->flags);
	seq_printf(m, "      var.name: %s\n", field->var.name);
	seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
		   field->var.idx);

	field = field_var->val;

	seq_printf(m, "\n      %s[%d].val:\n", vars_name, i);
	if (field->field)
		seq_printf(m, "      ftrace_event_field name: %s\n",
			   field->field->name);
	else {
		ret = -EINVAL;
		goto out;
	}

	seq_printf(m, "      type: %s\n", field->type);
	seq_printf(m, "      size: %u\n", field->size);
	seq_printf(m, "      is_signed: %u\n", field->is_signed);
out:
	return ret;
}

static int hist_action_debug_show(struct seq_file *m,
				  struct action_data *data, int i)
{
	int ret = 0;

	if (data->handler == HANDLER_ONMAX ||
	    data->handler == HANDLER_ONCHANGE) {
		seq_printf(m, "\n    hist_data->actions[%d].track_data.var_ref:\n", i);
		ret = hist_field_debug_show(m, data->track_data.var_ref,
					    HIST_FIELD_FL_VAR_REF);
		if (ret)
			goto out;

		seq_printf(m, "\n    hist_data->actions[%d].track_data.track_var:\n", i);
		ret = hist_field_debug_show(m, data->track_data.track_var,
					    HIST_FIELD_FL_VAR);
		if (ret)
			goto out;
	}

	if (data->handler == HANDLER_ONMATCH) {
		seq_printf(m, "\n    hist_data->actions[%d].match_data.event_system: %s\n",
			   i, data->match_data.event_system);
		seq_printf(m, "    hist_data->actions[%d].match_data.event: %s\n",
			   i, data->match_data.event);
	}
out:
	return ret;
}

static int hist_actions_debug_show(struct seq_file *m,
				   struct hist_trigger_data *hist_data)
{
	int i, ret = 0;

	if (hist_data->n_actions)
		seq_puts(m, "\n  action tracking variables (for onmax()/onchange()/onmatch()):\n");

	for (i = 0; i < hist_data->n_actions; i++) {
		struct action_data *action = hist_data->actions[i];

		ret = hist_action_debug_show(m, action, i);
		if (ret)
			goto out;
	}

	if (hist_data->n_save_vars)
		seq_puts(m, "\n  save action variables (save() params):\n");

	for (i = 0; i < hist_data->n_save_vars; i++) {
		ret = field_var_debug_show(m, hist_data->save_vars[i], i, true);
		if (ret)
			goto out;
	}
out:
	return ret;
}

static void hist_trigger_debug_show(struct seq_file *m,
				    struct event_trigger_data *data, int n)
{
	struct hist_trigger_data *hist_data;
	int i, ret;

	if (n > 0)
		seq_puts(m, "\n\n");

	seq_puts(m, "# event histogram\n#\n# trigger info: ");
	data->ops->print(m, data);
	seq_puts(m, "#\n\n");

	hist_data = data->private_data;

	seq_printf(m, "hist_data: %p\n\n", hist_data);
	seq_printf(m, "  n_vals: %u\n", hist_data->n_vals);
	seq_printf(m, "  n_keys: %u\n", hist_data->n_keys);
	seq_printf(m, "  n_fields: %u\n", hist_data->n_fields);

	seq_puts(m, "\n  val fields:\n\n");

	seq_puts(m, "    hist_data->fields[0]:\n");
	ret = hist_field_debug_show(m, hist_data->fields[0],
				    HIST_FIELD_FL_HITCOUNT);
	if (ret)
		return;

	for (i = 1; i < hist_data->n_vals; i++) {
		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);
		ret = hist_field_debug_show(m, hist_data->fields[i], 0);
		if (ret)
			return;
	}

	seq_puts(m, "\n  key fields:\n");

	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {
		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);
		ret = hist_field_debug_show(m, hist_data->fields[i],
					    HIST_FIELD_FL_KEY);
		if (ret)
			return;
	}

	if (hist_data->n_var_refs)
		seq_puts(m, "\n  variable reference fields:\n");

	for (i = 0; i < hist_data->n_var_refs; i++) {
		seq_printf(m, "\n    hist_data->var_refs[%d]:\n", i);
		ret = hist_field_debug_show(m, hist_data->var_refs[i],
					    HIST_FIELD_FL_VAR_REF);
		if (ret)
			return;
	}

	if (hist_data->n_field_vars)
		seq_puts(m, "\n  field variables:\n");

	for (i = 0; i < hist_data->n_field_vars; i++) {
		ret = field_var_debug_show(m, hist_data->field_vars[i], i, false);
		if (ret)
			return;
	}

	ret = hist_actions_debug_show(m, hist_data);
	if (ret)
		return;
}

static int hist_debug_show(struct seq_file *m, void *v)
{
	struct event_trigger_data *data;
	struct trace_event_file *event_file;
	int n = 0, ret = 0;

	mutex_lock(&event_mutex);

	event_file = event_file_data(m->private);
	if (unlikely(!event_file)) {
		ret = -ENODEV;
		goto out_unlock;
	}

	list_for_each_entry(data, &event_file->triggers, list) {
		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
			hist_trigger_debug_show(m, data, n++);
	}

 out_unlock:
	mutex_unlock(&event_mutex);

	return ret;
}

static int event_hist_debug_open(struct inode *inode, struct file *file)
{
	int ret;

	ret = security_locked_down(LOCKDOWN_TRACEFS);
	if (ret)
		return ret;

	return single_open(file, hist_debug_show, file);
}

const struct file_operations event_hist_debug_fops = {
	.open = event_hist_debug_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};
#endif

static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
{
	const char *field_name = hist_field_name(hist_field, 0);

	if (hist_field->var.name)
		seq_printf(m, "%s=", hist_field->var.name);

	if (hist_field->flags & HIST_FIELD_FL_CPU)
		seq_puts(m, "common_cpu");
	else if (hist_field->flags & HIST_FIELD_FL_CONST)
		seq_printf(m, "%llu", hist_field->constant);
	else if (field_name) {
		if (hist_field->flags & HIST_FIELD_FL_VAR_REF ||
		    hist_field->flags & HIST_FIELD_FL_ALIAS)
			seq_putc(m, '$');
		seq_printf(m, "%s", field_name);
	} else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
		seq_puts(m, "common_timestamp");

	if (hist_field->flags) {
		if (!(hist_field->flags & HIST_FIELD_FL_VAR_REF) &&
		    !(hist_field->flags & HIST_FIELD_FL_EXPR) &&
		    !(hist_field->flags & HIST_FIELD_FL_STACKTRACE)) {
			const char *flags = get_hist_field_flags(hist_field);

			if (flags)
				seq_printf(m, ".%s", flags);
		}
	}
	if (hist_field->buckets)
		seq_printf(m, "=%ld", hist_field->buckets);
}

static int event_hist_trigger_print(struct seq_file *m,
				    struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct hist_field *field;
	bool have_var = false;
	bool show_val = false;
	unsigned int i;

	seq_puts(m, HIST_PREFIX);

	if (data->name)
		seq_printf(m, "%s:", data->name);

	seq_puts(m, "keys=");

	for_each_hist_key_field(i, hist_data) {
		field = hist_data->fields[i];

		if (i > hist_data->n_vals)
			seq_puts(m, ",");

		if (field->flags & HIST_FIELD_FL_STACKTRACE) {
			if (field->field)
				seq_printf(m, "%s.stacktrace", field->field->name);
			else
				seq_puts(m, "common_stacktrace");
		} else
			hist_field_print(m, field);
	}

	seq_puts(m, ":vals=");

	for_each_hist_val_field(i, hist_data) {
		field = hist_data->fields[i];
		if (field->flags & HIST_FIELD_FL_VAR) {
			have_var = true;
			continue;
		}

		if (i == HITCOUNT_IDX) {
			if (hist_data->attrs->no_hitcount)
				continue;
			seq_puts(m, "hitcount");
		} else {
			if (show_val)
				seq_puts(m, ",");
			hist_field_print(m, field);
		}
		show_val = true;
	}

	if (have_var) {
		unsigned int n = 0;

		seq_puts(m, ":");

		for_each_hist_val_field(i, hist_data) {
			field = hist_data->fields[i];

			if (field->flags & HIST_FIELD_FL_VAR) {
				if (n++)
					seq_puts(m, ",");
				hist_field_print(m, field);
			}
		}
	}

	seq_puts(m, ":sort=");

	for (i = 0; i < hist_data->n_sort_keys; i++) {
		struct tracing_map_sort_key *sort_key;
		unsigned int idx, first_key_idx;

		/* skip VAR vals */
		first_key_idx = hist_data->n_vals - hist_data->n_vars;

		sort_key = &hist_data->sort_keys[i];
		idx = sort_key->field_idx;

		if (WARN_ON(idx >= HIST_FIELDS_MAX))
			return -EINVAL;

		if (i > 0)
			seq_puts(m, ",");

		if (idx == HITCOUNT_IDX)
			seq_puts(m, "hitcount");
		else {
			if (idx >= first_key_idx)
				idx += hist_data->n_vars;
			hist_field_print(m, hist_data->fields[idx]);
		}

		if (sort_key->descending)
			seq_puts(m, ".descending");
	}
	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
	if (hist_data->enable_timestamps)
		seq_printf(m, ":clock=%s", hist_data->attrs->clock);
	if (hist_data->attrs->no_hitcount)
		seq_puts(m, ":nohitcount");

	print_actions_spec(m, hist_data);

	if (data->filter_str)
		seq_printf(m, " if %s", data->filter_str);

	if (data->paused)
		seq_puts(m, " [paused]");
	else
		seq_puts(m, " [active]");

	seq_putc(m, '\n');

	return 0;
}

static int event_hist_trigger_init(struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;

	if (!data->ref && hist_data->attrs->name)
		save_named_trigger(hist_data->attrs->name, data);

	data->ref++;

	return 0;
}

static void unregister_field_var_hists(struct hist_trigger_data *hist_data)
{
	struct trace_event_file *file;
	unsigned int i;
	char *cmd;
	int ret;

	for (i = 0; i < hist_data->n_field_var_hists; i++) {
		file = hist_data->field_var_hists[i]->hist_data->event_file;
		cmd = hist_data->field_var_hists[i]->cmd;
		ret = event_hist_trigger_parse(&trigger_hist_cmd, file,
					       "!hist", "hist", cmd);
		WARN_ON_ONCE(ret < 0);
	}
}

static void event_hist_trigger_free(struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;

	if (WARN_ON_ONCE(data->ref <= 0))
		return;

	data->ref--;
	if (!data->ref) {
		if (data->name)
			del_named_trigger(data);

		trigger_data_free(data);

		remove_hist_vars(hist_data);

		unregister_field_var_hists(hist_data);

		destroy_hist_data(hist_data);
	}
}

static struct event_trigger_ops event_hist_trigger_ops = {
	.trigger		= event_hist_trigger,
	.print			= event_hist_trigger_print,
	.init			= event_hist_trigger_init,
	.free			= event_hist_trigger_free,
};

static int event_hist_trigger_named_init(struct event_trigger_data *data)
{
	data->ref++;

	save_named_trigger(data->named_data->name, data);

	event_hist_trigger_init(data->named_data);

	return 0;
}

static void event_hist_trigger_named_free(struct event_trigger_data *data)
{
	if (WARN_ON_ONCE(data->ref <= 0))
		return;

	event_hist_trigger_free(data->named_data);

	data->ref--;
	if (!data->ref) {
		del_named_trigger(data);
		trigger_data_free(data);
	}
}

static struct event_trigger_ops event_hist_trigger_named_ops = {
	.trigger		= event_hist_trigger,
	.print			= event_hist_trigger_print,
	.init			= event_hist_trigger_named_init,
	.free			= event_hist_trigger_named_free,
};

static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
							    char *param)
{
	return &event_hist_trigger_ops;
}

static void hist_clear(struct event_trigger_data *data)
{
	struct hist_trigger_data *hist_data = data->private_data;

	if (data->name)
		pause_named_trigger(data);

	tracepoint_synchronize_unregister();

	tracing_map_clear(hist_data->map);

	if (data->name)
		unpause_named_trigger(data);
}

static bool compatible_field(struct ftrace_event_field *field,
			     struct ftrace_event_field *test_field)
{
	if (field == test_field)
		return true;
	if (field == NULL || test_field == NULL)
		return false;
	if (strcmp(field->name, test_field->name) != 0)
		return false;
	if (strcmp(field->type, test_field->type) != 0)
		return false;
	if (field->size != test_field->size)
		return false;
	if (field->is_signed != test_field->is_signed)
		return false;

	return true;
}

static bool hist_trigger_match(struct event_trigger_data *data,
			       struct event_trigger_data *data_test,
			       struct event_trigger_data *named_data,
			       bool ignore_filter)
{
	struct tracing_map_sort_key *sort_key, *sort_key_test;
	struct hist_trigger_data *hist_data, *hist_data_test;
	struct hist_field *key_field, *key_field_test;
	unsigned int i;

	if (named_data && (named_data != data_test) &&
	    (named_data != data_test->named_data))
		return false;

	if (!named_data && is_named_trigger(data_test))
		return false;

	hist_data = data->private_data;
	hist_data_test = data_test->private_data;

	if (hist_data->n_vals != hist_data_test->n_vals ||
	    hist_data->n_fields != hist_data_test->n_fields ||
	    hist_data->n_sort_keys != hist_data_test->n_sort_keys)
		return false;

	if (!ignore_filter) {
		if ((data->filter_str && !data_test->filter_str) ||
		   (!data->filter_str && data_test->filter_str))
			return false;
	}

	for_each_hist_field(i, hist_data) {
		key_field = hist_data->fields[i];
		key_field_test = hist_data_test->fields[i];

		if (key_field->flags != key_field_test->flags)
			return false;
		if (!compatible_field(key_field->field, key_field_test->field))
			return false;
		if (key_field->offset != key_field_test->offset)
			return false;
		if (key_field->size != key_field_test->size)
			return false;
		if (key_field->is_signed != key_field_test->is_signed)
			return false;
		if (!!key_field->var.name != !!key_field_test->var.name)
			return false;
		if (key_field->var.name &&
		    strcmp(key_field->var.name, key_field_test->var.name) != 0)
			return false;
	}

	for (i = 0; i < hist_data->n_sort_keys; i++) {
		sort_key = &hist_data->sort_keys[i];
		sort_key_test = &hist_data_test->sort_keys[i];

		if (sort_key->field_idx != sort_key_test->field_idx ||
		    sort_key->descending != sort_key_test->descending)
			return false;
	}

	if (!ignore_filter && data->filter_str &&
	    (strcmp(data->filter_str, data_test->filter_str) != 0))
		return false;

	if (!actions_match(hist_data, hist_data_test))
		return false;

	return true;
}

static bool existing_hist_update_only(char *glob,
				      struct event_trigger_data *data,
				      struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct event_trigger_data *test, *named_data = NULL;
	bool updated = false;

	if (!hist_data->attrs->pause && !hist_data->attrs->cont &&
	    !hist_data->attrs->clear)
		goto out;

	if (hist_data->attrs->name) {
		named_data = find_named_trigger(hist_data->attrs->name);
		if (named_data) {
			if (!hist_trigger_match(data, named_data, named_data,
						true))
				goto out;
		}
	}

	if (hist_data->attrs->name && !named_data)
		goto out;

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (!hist_trigger_match(data, test, named_data, false))
				continue;
			if (hist_data->attrs->pause)
				test->paused = true;
			else if (hist_data->attrs->cont)
				test->paused = false;
			else if (hist_data->attrs->clear)
				hist_clear(test);
			updated = true;
			goto out;
		}
	}
 out:
	return updated;
}

static int hist_register_trigger(char *glob,
				 struct event_trigger_data *data,
				 struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct event_trigger_data *test, *named_data = NULL;
	struct trace_array *tr = file->tr;
	int ret = 0;

	if (hist_data->attrs->name) {
		named_data = find_named_trigger(hist_data->attrs->name);
		if (named_data) {
			if (!hist_trigger_match(data, named_data, named_data,
						true)) {
				hist_err(tr, HIST_ERR_NAMED_MISMATCH, errpos(hist_data->attrs->name));
				ret = -EINVAL;
				goto out;
			}
		}
	}

	if (hist_data->attrs->name && !named_data)
		goto new;

	lockdep_assert_held(&event_mutex);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (hist_trigger_match(data, test, named_data, false)) {
				hist_err(tr, HIST_ERR_TRIGGER_EEXIST, 0);
				ret = -EEXIST;
				goto out;
			}
		}
	}
 new:
	if (hist_data->attrs->cont || hist_data->attrs->clear) {
		hist_err(tr, HIST_ERR_TRIGGER_ENOENT_CLEAR, 0);
		ret = -ENOENT;
		goto out;
	}

	if (hist_data->attrs->pause)
		data->paused = true;

	if (named_data) {
		data->private_data = named_data->private_data;
		set_named_trigger_data(data, named_data);
		data->ops = &event_hist_trigger_named_ops;
	}

	if (data->ops->init) {
		ret = data->ops->init(data);
		if (ret < 0)
			goto out;
	}

	if (hist_data->enable_timestamps) {
		char *clock = hist_data->attrs->clock;

		ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
		if (ret) {
			hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock));
			goto out;
		}

		tracing_set_filter_buffering(file->tr, true);
	}

	if (named_data)
		destroy_hist_data(hist_data);
 out:
	return ret;
}

static int hist_trigger_enable(struct event_trigger_data *data,
			       struct trace_event_file *file)
{
	int ret = 0;

	list_add_tail_rcu(&data->list, &file->triggers);

	update_cond_flag(file);

	if (trace_event_trigger_enable_disable(file, 1) < 0) {
		list_del_rcu(&data->list);
		update_cond_flag(file);
		ret--;
	}

	return ret;
}

static bool have_hist_trigger_match(struct event_trigger_data *data,
				    struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct event_trigger_data *test, *named_data = NULL;
	bool match = false;

	lockdep_assert_held(&event_mutex);

	if (hist_data->attrs->name)
		named_data = find_named_trigger(hist_data->attrs->name);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (hist_trigger_match(data, test, named_data, false)) {
				match = true;
				break;
			}
		}
	}

	return match;
}

static bool hist_trigger_check_refs(struct event_trigger_data *data,
				    struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data = data->private_data;
	struct event_trigger_data *test, *named_data = NULL;

	lockdep_assert_held(&event_mutex);

	if (hist_data->attrs->name)
		named_data = find_named_trigger(hist_data->attrs->name);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (!hist_trigger_match(data, test, named_data, false))
				continue;
			hist_data = test->private_data;
			if (check_var_refs(hist_data))
				return true;
			break;
		}
	}

	return false;
}

static void hist_unregister_trigger(char *glob,
				    struct event_trigger_data *data,
				    struct trace_event_file *file)
{
	struct event_trigger_data *test = NULL, *iter, *named_data = NULL;
	struct hist_trigger_data *hist_data = data->private_data;

	lockdep_assert_held(&event_mutex);

	if (hist_data->attrs->name)
		named_data = find_named_trigger(hist_data->attrs->name);

	list_for_each_entry(iter, &file->triggers, list) {
		if (iter->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (!hist_trigger_match(data, iter, named_data, false))
				continue;
			test = iter;
			list_del_rcu(&test->list);
			trace_event_trigger_enable_disable(file, 0);
			update_cond_flag(file);
			break;
		}
	}

	if (test && test->ops->free)
		test->ops->free(test);

	if (hist_data->enable_timestamps) {
		if (!hist_data->remove || test)
			tracing_set_filter_buffering(file->tr, false);
	}
}

static bool hist_file_check_refs(struct trace_event_file *file)
{
	struct hist_trigger_data *hist_data;
	struct event_trigger_data *test;

	lockdep_assert_held(&event_mutex);

	list_for_each_entry(test, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			hist_data = test->private_data;
			if (check_var_refs(hist_data))
				return true;
		}
	}

	return false;
}

static void hist_unreg_all(struct trace_event_file *file)
{
	struct event_trigger_data *test, *n;
	struct hist_trigger_data *hist_data;
	struct synth_event *se;
	const char *se_name;

	lockdep_assert_held(&event_mutex);

	if (hist_file_check_refs(file))
		return;

	list_for_each_entry_safe(test, n, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			hist_data = test->private_data;
			list_del_rcu(&test->list);
			trace_event_trigger_enable_disable(file, 0);

			se_name = trace_event_name(file->event_call);
			se = find_synth_event(se_name);
			if (se)
				se->ref--;

			update_cond_flag(file);
			if (hist_data->enable_timestamps)
				tracing_set_filter_buffering(file->tr, false);
			if (test->ops->free)
				test->ops->free(test);
		}
	}
}

static int event_hist_trigger_parse(struct event_command *cmd_ops,
				    struct trace_event_file *file,
				    char *glob, char *cmd,
				    char *param_and_filter)
{
	unsigned int hist_trigger_bits = TRACING_MAP_BITS_DEFAULT;
	struct event_trigger_data *trigger_data;
	struct hist_trigger_attrs *attrs;
	struct hist_trigger_data *hist_data;
	char *param, *filter, *p, *start;
	struct synth_event *se;
	const char *se_name;
	bool remove;
	int ret = 0;

	lockdep_assert_held(&event_mutex);

	if (WARN_ON(!glob))
		return -EINVAL;

	if (glob[0]) {
		hist_err_clear();
		last_cmd_set(file, param_and_filter);
	}

	remove = event_trigger_check_remove(glob);

	if (event_trigger_empty_param(param_and_filter))
		return -EINVAL;

	/*
	 * separate the trigger from the filter (k:v [if filter])
	 * allowing for whitespace in the trigger
	 */
	p = param = param_and_filter;
	do {
		p = strstr(p, "if");
		if (!p)
			break;
		if (p == param_and_filter)
			return -EINVAL;
		if (*(p - 1) != ' ' && *(p - 1) != '\t') {
			p++;
			continue;
		}
		if (p >= param_and_filter + strlen(param_and_filter) - (sizeof("if") - 1) - 1)
			return -EINVAL;
		if (*(p + sizeof("if") - 1) != ' ' && *(p + sizeof("if") - 1) != '\t') {
			p++;
			continue;
		}
		break;
	} while (1);

	if (!p)
		filter = NULL;
	else {
		*(p - 1) = '\0';
		filter = strstrip(p);
		param = strstrip(param);
	}

	/*
	 * To simplify arithmetic expression parsing, replace occurrences of
	 * '.sym-offset' modifier with '.symXoffset'
	 */
	start = strstr(param, ".sym-offset");
	while (start) {
		*(start + 4) = 'X';
		start = strstr(start + 11, ".sym-offset");
	}

	attrs = parse_hist_trigger_attrs(file->tr, param);
	if (IS_ERR(attrs))
		return PTR_ERR(attrs);

	if (attrs->map_bits)
		hist_trigger_bits = attrs->map_bits;

	hist_data = create_hist_data(hist_trigger_bits, attrs, file, remove);
	if (IS_ERR(hist_data)) {
		destroy_hist_trigger_attrs(attrs);
		return PTR_ERR(hist_data);
	}

	trigger_data = event_trigger_alloc(cmd_ops, cmd, param, hist_data);
	if (!trigger_data) {
		ret = -ENOMEM;
		goto out_free;
	}

	ret = event_trigger_set_filter(cmd_ops, file, filter, trigger_data);
	if (ret < 0)
		goto out_free;

	if (remove) {
		if (!have_hist_trigger_match(trigger_data, file))
			goto out_free;

		if (hist_trigger_check_refs(trigger_data, file)) {
			ret = -EBUSY;
			goto out_free;
		}

		event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
		se_name = trace_event_name(file->event_call);
		se = find_synth_event(se_name);
		if (se)
			se->ref--;
		ret = 0;
		goto out_free;
	}

	if (existing_hist_update_only(glob, trigger_data, file))
		goto out_free;

	ret = event_trigger_register(cmd_ops, file, glob, trigger_data);
	if (ret < 0)
		goto out_free;

	if (get_named_trigger_data(trigger_data))
		goto enable;

	if (has_hist_vars(hist_data))
		save_hist_vars(hist_data);

	ret = create_actions(hist_data);
	if (ret)
		goto out_unreg;

	ret = tracing_map_init(hist_data->map);
	if (ret)
		goto out_unreg;
enable:
	ret = hist_trigger_enable(trigger_data, file);
	if (ret)
		goto out_unreg;

	se_name = trace_event_name(file->event_call);
	se = find_synth_event(se_name);
	if (se)
		se->ref++;
 out:
	if (ret == 0 && glob[0])
		hist_err_clear();

	return ret;
 out_unreg:
	event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
 out_free:
	event_trigger_reset_filter(cmd_ops, trigger_data);

	remove_hist_vars(hist_data);

	kfree(trigger_data);

	destroy_hist_data(hist_data);
	goto out;
}

static struct event_command trigger_hist_cmd = {
	.name			= "hist",
	.trigger_type		= ETT_EVENT_HIST,
	.flags			= EVENT_CMD_FL_NEEDS_REC,
	.parse			= event_hist_trigger_parse,
	.reg			= hist_register_trigger,
	.unreg			= hist_unregister_trigger,
	.unreg_all		= hist_unreg_all,
	.get_trigger_ops	= event_hist_get_trigger_ops,
	.set_filter		= set_trigger_filter,
};

__init int register_trigger_hist_cmd(void)
{
	int ret;

	ret = register_event_command(&trigger_hist_cmd);
	WARN_ON(ret < 0);

	return ret;
}

static void
hist_enable_trigger(struct event_trigger_data *data,
		    struct trace_buffer *buffer,  void *rec,
		    struct ring_buffer_event *event)
{
	struct enable_trigger_data *enable_data = data->private_data;
	struct event_trigger_data *test;

	list_for_each_entry_rcu(test, &enable_data->file->triggers, list,
				lockdep_is_held(&event_mutex)) {
		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
			if (enable_data->enable)
				test->paused = false;
			else
				test->paused = true;
		}
	}
}

static void
hist_enable_count_trigger(struct event_trigger_data *data,
			  struct trace_buffer *buffer,  void *rec,
			  struct ring_buffer_event *event)
{
	if (!data->count)
		return;

	if (data->count != -1)
		(data->count)--;

	hist_enable_trigger(data, buffer, rec, event);
}

static struct event_trigger_ops hist_enable_trigger_ops = {
	.trigger		= hist_enable_trigger,
	.print			= event_enable_trigger_print,
	.init			= event_trigger_init,
	.free			= event_enable_trigger_free,
};

static struct event_trigger_ops hist_enable_count_trigger_ops = {
	.trigger		= hist_enable_count_trigger,
	.print			= event_enable_trigger_print,
	.init			= event_trigger_init,
	.free			= event_enable_trigger_free,
};

static struct event_trigger_ops hist_disable_trigger_ops = {
	.trigger		= hist_enable_trigger,
	.print			= event_enable_trigger_print,
	.init			= event_trigger_init,
	.free			= event_enable_trigger_free,
};

static struct event_trigger_ops hist_disable_count_trigger_ops = {
	.trigger		= hist_enable_count_trigger,
	.print			= event_enable_trigger_print,
	.init			= event_trigger_init,
	.free			= event_enable_trigger_free,
};

static struct event_trigger_ops *
hist_enable_get_trigger_ops(char *cmd, char *param)
{
	struct event_trigger_ops *ops;
	bool enable;

	enable = (strcmp(cmd, ENABLE_HIST_STR) == 0);

	if (enable)
		ops = param ? &hist_enable_count_trigger_ops :
			&hist_enable_trigger_ops;
	else
		ops = param ? &hist_disable_count_trigger_ops :
			&hist_disable_trigger_ops;

	return ops;
}

static void hist_enable_unreg_all(struct trace_event_file *file)
{
	struct event_trigger_data *test, *n;

	list_for_each_entry_safe(test, n, &file->triggers, list) {
		if (test->cmd_ops->trigger_type == ETT_HIST_ENABLE) {
			list_del_rcu(&test->list);
			update_cond_flag(file);
			trace_event_trigger_enable_disable(file, 0);
			if (test->ops->free)
				test->ops->free(test);
		}
	}
}

static struct event_command trigger_hist_enable_cmd = {
	.name			= ENABLE_HIST_STR,
	.trigger_type		= ETT_HIST_ENABLE,
	.parse			= event_enable_trigger_parse,
	.reg			= event_enable_register_trigger,
	.unreg			= event_enable_unregister_trigger,
	.unreg_all		= hist_enable_unreg_all,
	.get_trigger_ops	= hist_enable_get_trigger_ops,
	.set_filter		= set_trigger_filter,
};

static struct event_command trigger_hist_disable_cmd = {
	.name			= DISABLE_HIST_STR,
	.trigger_type		= ETT_HIST_ENABLE,
	.parse			= event_enable_trigger_parse,
	.reg			= event_enable_register_trigger,
	.unreg			= event_enable_unregister_trigger,
	.unreg_all		= hist_enable_unreg_all,
	.get_trigger_ops	= hist_enable_get_trigger_ops,
	.set_filter		= set_trigger_filter,
};

static __init void unregister_trigger_hist_enable_disable_cmds(void)
{
	unregister_event_command(&trigger_hist_enable_cmd);
	unregister_event_command(&trigger_hist_disable_cmd);
}

__init int register_trigger_hist_enable_disable_cmds(void)
{
	int ret;

	ret = register_event_command(&trigger_hist_enable_cmd);
	if (WARN_ON(ret < 0))
		return ret;
	ret = register_event_command(&trigger_hist_disable_cmd);
	if (WARN_ON(ret < 0))
		unregister_trigger_hist_enable_disable_cmds();

	return ret;
}