/*
 * trace_events_filter - generic event filtering
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) 2009 Tom Zanussi <tzanussi@gmail.com>
 */

#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/mutex.h>
#include <linux/perf_event.h>
#include <linux/slab.h>

#include "trace.h"
#include "trace_output.h"

enum filter_op_ids
{
        OP_OR,
        OP_AND,
        OP_GLOB,
        OP_NE,
        OP_EQ,
        OP_LT,
        OP_LE,
        OP_GT,
        OP_GE,
        OP_NONE,
        OP_OPEN_PAREN,
};

struct filter_op {
        int id;
        char *string;
        int precedence;
};

static struct filter_op filter_ops[] = {
        { OP_OR,        "||",           1 },
        { OP_AND,       "&&",           2 },
        { OP_GLOB,      "~",            4 },
        { OP_NE,        "!=",           4 },
        { OP_EQ,        "==",           4 },
        { OP_LT,        "<",            5 },
        { OP_LE,        "<=",           5 },
        { OP_GT,        ">",            5 },
        { OP_GE,        ">=",           5 },
        { OP_NONE,      "OP_NONE",      0 },
        { OP_OPEN_PAREN, "(",           0 },
};

enum {
        FILT_ERR_NONE,
        FILT_ERR_INVALID_OP,
        FILT_ERR_UNBALANCED_PAREN,
        FILT_ERR_TOO_MANY_OPERANDS,
        FILT_ERR_OPERAND_TOO_LONG,
        FILT_ERR_FIELD_NOT_FOUND,
        FILT_ERR_ILLEGAL_FIELD_OP,
        FILT_ERR_ILLEGAL_INTVAL,
        FILT_ERR_BAD_SUBSYS_FILTER,
        FILT_ERR_TOO_MANY_PREDS,
        FILT_ERR_MISSING_FIELD,
        FILT_ERR_INVALID_FILTER,
};

static char *err_text[] = {
        "No error",
        "Invalid operator",
        "Unbalanced parens",
        "Too many operands",
        "Operand too long",
        "Field not found",
        "Illegal operation for field type",
        "Illegal integer value",
        "Couldn't find or set field in one of a subsystem's events",
        "Too many terms in predicate expression",
        "Missing field name and/or value",
        "Meaningless filter expression",
};

struct opstack_op {
        int op;
        struct list_head list;
};

struct postfix_elt {
        int op;
        char *operand;
        struct list_head list;
};

struct filter_parse_state {
        struct filter_op *ops;
        struct list_head opstack;
        struct list_head postfix;
        int lasterr;
        int lasterr_pos;

        struct {
                char *string;
                unsigned int cnt;
                unsigned int tail;
        } infix;

        struct {
                char string[MAX_FILTER_STR_VAL];
                int pos;
                unsigned int tail;
        } operand;
};

#define DEFINE_COMPARISON_PRED(type)                                    \
static int filter_pred_##type(struct filter_pred *pred, void *event,    \
                              int val1, int val2)                       \
{                                                                       \
        type *addr = (type *)(event + pred->offset);                    \
        type val = (type)pred->val;                                     \
        int match = 0;                                                  \
                                                                        \
        switch (pred->op) {                                             \
        case OP_LT:                                                     \
                match = (*addr < val);                                  \
                break;                                                  \
        case OP_LE:                                                     \
                match = (*addr <= val);                                 \
                break;                                                  \
        case OP_GT:                                                     \
                match = (*addr > val);                                  \
                break;                                                  \
        case OP_GE:                                                     \
                match = (*addr >= val);                                 \
                break;                                                  \
        default:                                                        \
                break;                                                  \
        }                                                               \
                                                                        \
        return match;                                                   \
}

#define DEFINE_EQUALITY_PRED(size)                                      \
static int filter_pred_##size(struct filter_pred *pred, void *event,    \
                              int val1, int val2)                       \
{                                                                       \
        u##size *addr = (u##size *)(event + pred->offset);              \
        u##size val = (u##size)pred->val;                               \
        int match;                                                      \
                                                                        \
        match = (val == *addr) ^ pred->not;                             \
                                                                        \
        return match;                                                   \
}

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

DEFINE_EQUALITY_PRED(64);
DEFINE_EQUALITY_PRED(32);
DEFINE_EQUALITY_PRED(16);
DEFINE_EQUALITY_PRED(8);

static int filter_pred_and(struct filter_pred *pred __attribute((unused)),
                           void *event __attribute((unused)),
                           int val1, int val2)
{
        return val1 && val2;
}

static int filter_pred_or(struct filter_pred *pred __attribute((unused)),
                          void *event __attribute((unused)),
                          int val1, int val2)
{
        return val1 || val2;
}

/* Filter predicate for fixed sized arrays of characters */
static int filter_pred_string(struct filter_pred *pred, void *event,
                              int val1, int val2)
{
        char *addr = (char *)(event + pred->offset);
        int cmp, match;

        cmp = pred->regex.match(addr, &pred->regex, pred->regex.field_len);

        match = cmp ^ pred->not;

        return match;
}

/* Filter predicate for char * pointers */
static int filter_pred_pchar(struct filter_pred *pred, void *event,
                             int val1, int val2)
{
        char **addr = (char **)(event + pred->offset);
        int cmp, match;
        int len = strlen(*addr) + 1;    /* including tailing '\0' */

        cmp = pred->regex.match(*addr, &pred->regex, len);

        match = cmp ^ pred->not;

        return match;
}

/*
 * Filter predicate for dynamic sized arrays of characters.
 * These are implemented through a list of strings at the end
 * of the entry.
 * Also each of these strings have a field in the entry which
 * contains its offset from the beginning of the entry.
 * We have then first to get this field, dereference it
 * and add it to the address of the entry, and at last we have
 * the address of the string.
 */
static int filter_pred_strloc(struct filter_pred *pred, void *event,
                              int val1, int val2)
{
        u32 str_item = *(u32 *)(event + pred->offset);
        int str_loc = str_item & 0xffff;
        int str_len = str_item >> 16;
        char *addr = (char *)(event + str_loc);
        int cmp, match;

        cmp = pred->regex.match(addr, &pred->regex, str_len);

        match = cmp ^ pred->not;

        return match;
}

static int filter_pred_none(struct filter_pred *pred, void *event,
                            int val1, int val2)
{
        return 0;
}

/*
 * regex_match_foo - Basic regex callbacks
 *
 * @str: the string to be searched
 * @r:   the regex structure containing the pattern string
 * @len: the length of the string to be searched (including '\0')
 *
 * Note:
 * - @str might not be NULL-terminated if it's of type DYN_STRING
 *   or STATIC_STRING
 */

static int regex_match_full(char *str, struct regex *r, int len)
{
        if (strncmp(str, r->pattern, len) == 0)
                return 1;
        return 0;
}

static int regex_match_front(char *str, struct regex *r, int len)
{
        if (strncmp(str, r->pattern, r->len) == 0)
                return 1;
        return 0;
}

static int regex_match_middle(char *str, struct regex *r, int len)
{
        if (strnstr(str, r->pattern, len))
                return 1;
        return 0;
}

static int regex_match_end(char *str, struct regex *r, int len)
{
        int strlen = len - 1;

        if (strlen >= r->len &&
            memcmp(str + strlen - r->len, r->pattern, r->len) == 0)
                return 1;
        return 0;
}

/**
 * filter_parse_regex - parse a basic regex
 * @buff:   the raw regex
 * @len:    length of the regex
 * @search: will point to the beginning of the string to compare
 * @not:    tell whether the match will have to be inverted
 *
 * This passes in a buffer containing a regex and this function will
 * set search to point to the search part of the buffer and
 * return the type of search it is (see enum above).
 * This does modify buff.
 *
 * Returns enum type.
 *  search returns the pointer to use for comparison.
 *  not returns 1 if buff started with a '!'
 *     0 otherwise.
 */
enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
{
        int type = MATCH_FULL;
        int i;

        if (buff[0] == '!') {
                *not = 1;
                buff++;
                len--;
        } else
                *not = 0;

        *search = buff;

        for (i = 0; i < len; i++) {
                if (buff[i] == '*') {
                        if (!i) {
                                *search = buff + 1;
                                type = MATCH_END_ONLY;
                        } else {
                                if (type == MATCH_END_ONLY)
                                        type = MATCH_MIDDLE_ONLY;
                                else
                                        type = MATCH_FRONT_ONLY;
                                buff[i] = 0;
                                break;
                        }
                }
        }

        return type;
}

static void filter_build_regex(struct filter_pred *pred)
{
        struct regex *r = &pred->regex;
        char *search;
        enum regex_type type = MATCH_FULL;
        int not = 0;

        if (pred->op == OP_GLOB) {
                type = filter_parse_regex(r->pattern, r->len, &search, &not);
                r->len = strlen(search);
                memmove(r->pattern, search, r->len+1);
        }

        switch (type) {
        case MATCH_FULL:
                r->match = regex_match_full;
                break;
        case MATCH_FRONT_ONLY:
                r->match = regex_match_front;
                break;
        case MATCH_MIDDLE_ONLY:
                r->match = regex_match_middle;
                break;
        case MATCH_END_ONLY:
                r->match = regex_match_end;
                break;
        }

        pred->not ^= not;
}

/* return 1 if event matches, 0 otherwise (discard) */
int filter_match_preds(struct event_filter *filter, void *rec)
{
        int match, top = 0, val1 = 0, val2 = 0;
        int stack[MAX_FILTER_PRED];
        struct filter_pred *pred;
        int i;

        for (i = 0; i < filter->n_preds; i++) {
                pred = filter->preds[i];
                if (!pred->pop_n) {
                        match = pred->fn(pred, rec, val1, val2);
                        stack[top++] = match;
                        continue;
                }
                if (pred->pop_n > top) {
                        WARN_ON_ONCE(1);
                        return 0;
                }
                val1 = stack[--top];
                val2 = stack[--top];
                match = pred->fn(pred, rec, val1, val2);
                stack[top++] = match;
        }

        return stack[--top];
}
EXPORT_SYMBOL_GPL(filter_match_preds);

static void parse_error(struct filter_parse_state *ps, int err, int pos)
{
        ps->lasterr = err;
        ps->lasterr_pos = pos;
}

static void remove_filter_string(struct event_filter *filter)
{
        kfree(filter->filter_string);
        filter->filter_string = NULL;
}

static int replace_filter_string(struct event_filter *filter,
                                 char *filter_string)
{
        kfree(filter->filter_string);
        filter->filter_string = kstrdup(filter_string, GFP_KERNEL);
        if (!filter->filter_string)
                return -ENOMEM;

        return 0;
}

static int append_filter_string(struct event_filter *filter,
                                char *string)
{
        int newlen;
        char *new_filter_string;

        BUG_ON(!filter->filter_string);
        newlen = strlen(filter->filter_string) + strlen(string) + 1;
        new_filter_string = kmalloc(newlen, GFP_KERNEL);
        if (!new_filter_string)
                return -ENOMEM;

        strcpy(new_filter_string, filter->filter_string);
        strcat(new_filter_string, string);
        kfree(filter->filter_string);
        filter->filter_string = new_filter_string;

        return 0;
}

static void append_filter_err(struct filter_parse_state *ps,
                              struct event_filter *filter)
{
        int pos = ps->lasterr_pos;
        char *buf, *pbuf;

        buf = (char *)__get_free_page(GFP_TEMPORARY);
        if (!buf)
                return;

        append_filter_string(filter, "\n");
        memset(buf, ' ', PAGE_SIZE);
        if (pos > PAGE_SIZE - 128)
                pos = 0;
        buf[pos] = '^';
        pbuf = &buf[pos] + 1;

        sprintf(pbuf, "\nparse_error: %s\n", err_text[ps->lasterr]);
        append_filter_string(filter, buf);
        free_page((unsigned long) buf);
}

void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s)
{
        struct event_filter *filter = call->filter;

        mutex_lock(&event_mutex);
        if (filter && filter->filter_string)
                trace_seq_printf(s, "%s\n", filter->filter_string);
        else
                trace_seq_printf(s, "none\n");
        mutex_unlock(&event_mutex);
}

void print_subsystem_event_filter(struct event_subsystem *system,
                                  struct trace_seq *s)
{
        struct event_filter *filter = system->filter;

        mutex_lock(&event_mutex);
        if (filter && filter->filter_string)
                trace_seq_printf(s, "%s\n", filter->filter_string);
        else
                trace_seq_printf(s, "none\n");
        mutex_unlock(&event_mutex);
}

static struct ftrace_event_field *
__find_event_field(struct list_head *head, char *name)
{
        struct ftrace_event_field *field;

        list_for_each_entry(field, head, link) {
                if (!strcmp(field->name, name))
                        return field;
        }

        return NULL;
}

static struct ftrace_event_field *
find_event_field(struct ftrace_event_call *call, char *name)
{
        struct ftrace_event_field *field;
        struct list_head *head;

        field = __find_event_field(&ftrace_common_fields, name);
        if (field)
                return field;

        head = trace_get_fields(call);
        return __find_event_field(head, name);
}

static void filter_free_pred(struct filter_pred *pred)
{
        if (!pred)
                return;

        kfree(pred->field_name);
        kfree(pred);
}

static void filter_clear_pred(struct filter_pred *pred)
{
        kfree(pred->field_name);
        pred->field_name = NULL;
        pred->regex.len = 0;
}

static int filter_set_pred(struct filter_pred *dest,
                           struct filter_pred *src,
                           filter_pred_fn_t fn)
{
        *dest = *src;
        if (src->field_name) {
                dest->field_name = kstrdup(src->field_name, GFP_KERNEL);
                if (!dest->field_name)
                        return -ENOMEM;
        }
        dest->fn = fn;

        return 0;
}

static void filter_disable_preds(struct ftrace_event_call *call)
{
        struct event_filter *filter = call->filter;
        int i;

        call->flags &= ~TRACE_EVENT_FL_FILTERED;
        filter->n_preds = 0;

        for (i = 0; i < MAX_FILTER_PRED; i++)
                filter->preds[i]->fn = filter_pred_none;
}

static void __free_preds(struct event_filter *filter)
{
        int i;

        if (!filter)
                return;

        for (i = 0; i < MAX_FILTER_PRED; i++) {
                if (filter->preds[i])
                        filter_free_pred(filter->preds[i]);
        }
        kfree(filter->preds);
        kfree(filter->filter_string);
        kfree(filter);
}

void destroy_preds(struct ftrace_event_call *call)
{
        __free_preds(call->filter);
        call->filter = NULL;
        call->flags &= ~TRACE_EVENT_FL_FILTERED;
}

static struct event_filter *__alloc_preds(void)
{
        struct event_filter *filter;
        struct filter_pred *pred;
        int i;

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

        filter->n_preds = 0;

        filter->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred), GFP_KERNEL);
        if (!filter->preds)
                goto oom;

        for (i = 0; i < MAX_FILTER_PRED; i++) {
                pred = kzalloc(sizeof(*pred), GFP_KERNEL);
                if (!pred)
                        goto oom;
                pred->fn = filter_pred_none;
                filter->preds[i] = pred;
        }

        return filter;

oom:
        __free_preds(filter);
        return ERR_PTR(-ENOMEM);
}

static int init_preds(struct ftrace_event_call *call)
{
        if (call->filter)
                return 0;

        call->flags &= ~TRACE_EVENT_FL_FILTERED;
        call->filter = __alloc_preds();
        if (IS_ERR(call->filter))
                return PTR_ERR(call->filter);

        return 0;
}

static int init_subsystem_preds(struct event_subsystem *system)
{
        struct ftrace_event_call *call;
        int err;

        list_for_each_entry(call, &ftrace_events, list) {
                if (strcmp(call->class->system, system->name) != 0)
                        continue;

                err = init_preds(call);
                if (err)
                        return err;
        }

        return 0;
}

static void filter_free_subsystem_preds(struct event_subsystem *system)
{
        struct ftrace_event_call *call;

        list_for_each_entry(call, &ftrace_events, list) {
                if (strcmp(call->class->system, system->name) != 0)
                        continue;

                filter_disable_preds(call);
                remove_filter_string(call->filter);
        }
}

static int filter_add_pred_fn(struct filter_parse_state *ps,
                              struct ftrace_event_call *call,
                              struct event_filter *filter,
                              struct filter_pred *pred,
                              filter_pred_fn_t fn)
{
        int idx, err;

        if (filter->n_preds == MAX_FILTER_PRED) {
                parse_error(ps, FILT_ERR_TOO_MANY_PREDS, 0);
                return -ENOSPC;
        }

        idx = filter->n_preds;
        filter_clear_pred(filter->preds[idx]);
        err = filter_set_pred(filter->preds[idx], pred, fn);
        if (err)
                return err;

        filter->n_preds++;

        return 0;
}

int filter_assign_type(const char *type)
{
        if (strstr(type, "__data_loc") && strstr(type, "char"))
                return FILTER_DYN_STRING;

        if (strchr(type, '[') && strstr(type, "char"))
                return FILTER_STATIC_STRING;

        return FILTER_OTHER;
}

static bool is_string_field(struct ftrace_event_field *field)
{
        return field->filter_type == FILTER_DYN_STRING ||
               field->filter_type == FILTER_STATIC_STRING ||
               field->filter_type == FILTER_PTR_STRING;
}

static int is_legal_op(struct ftrace_event_field *field, int op)
{
        if (is_string_field(field) &&
            (op != OP_EQ && op != OP_NE && op != OP_GLOB))
                return 0;
        if (!is_string_field(field) && op == OP_GLOB)
                return 0;

        return 1;
}

static filter_pred_fn_t select_comparison_fn(int op, int field_size,
                                             int field_is_signed)
{
        filter_pred_fn_t fn = NULL;

        switch (field_size) {
        case 8:
                if (op == OP_EQ || op == OP_NE)
                        fn = filter_pred_64;
                else if (field_is_signed)
                        fn = filter_pred_s64;
                else
                        fn = filter_pred_u64;
                break;
        case 4:
                if (op == OP_EQ || op == OP_NE)
                        fn = filter_pred_32;
                else if (field_is_signed)
                        fn = filter_pred_s32;
                else
                        fn = filter_pred_u32;
                break;
        case 2:
                if (op == OP_EQ || op == OP_NE)
                        fn = filter_pred_16;
                else if (field_is_signed)
                        fn = filter_pred_s16;
                else
                        fn = filter_pred_u16;
                break;
        case 1:
                if (op == OP_EQ || op == OP_NE)
                        fn = filter_pred_8;
                else if (field_is_signed)
                        fn = filter_pred_s8;
                else
                        fn = filter_pred_u8;
                break;
        }

        return fn;
}

static int filter_add_pred(struct filter_parse_state *ps,
                           struct ftrace_event_call *call,
                           struct event_filter *filter,
                           struct filter_pred *pred,
                           bool dry_run)
{
        struct ftrace_event_field *field;
        filter_pred_fn_t fn;
        unsigned long long val;
        int ret;

        pred->fn = filter_pred_none;

        if (pred->op == OP_AND) {
                pred->pop_n = 2;
                fn = filter_pred_and;
                goto add_pred_fn;
        } else if (pred->op == OP_OR) {
                pred->pop_n = 2;
                fn = filter_pred_or;
                goto add_pred_fn;
        }

        field = find_event_field(call, pred->field_name);
        if (!field) {
                parse_error(ps, FILT_ERR_FIELD_NOT_FOUND, 0);
                return -EINVAL;
        }

        pred->offset = field->offset;

        if (!is_legal_op(field, pred->op)) {
                parse_error(ps, FILT_ERR_ILLEGAL_FIELD_OP, 0);
                return -EINVAL;
        }

        if (is_string_field(field)) {
                filter_build_regex(pred);

                if (field->filter_type == FILTER_STATIC_STRING) {
                        fn = filter_pred_string;
                        pred->regex.field_len = field->size;
                } else if (field->filter_type == FILTER_DYN_STRING)
                        fn = filter_pred_strloc;
                else
                        fn = filter_pred_pchar;
        } else {
                if (field->is_signed)
                        ret = strict_strtoll(pred->regex.pattern, 0, &val);
                else
                        ret = strict_strtoull(pred->regex.pattern, 0, &val);
                if (ret) {
                        parse_error(ps, FILT_ERR_ILLEGAL_INTVAL, 0);
                        return -EINVAL;
                }
                pred->val = val;

                fn = select_comparison_fn(pred->op, field->size,
                                          field->is_signed);
                if (!fn) {
                        parse_error(ps, FILT_ERR_INVALID_OP, 0);
                        return -EINVAL;
                }
        }

        if (pred->op == OP_NE)
                pred->not = 1;

add_pred_fn:
        if (!dry_run)
                return filter_add_pred_fn(ps, call, filter, pred, fn);
        return 0;
}

static void parse_init(struct filter_parse_state *ps,
                       struct filter_op *ops,
                       char *infix_string)
{
        memset(ps, '\0', sizeof(*ps));

        ps->infix.string = infix_string;
        ps->infix.cnt = strlen(infix_string);
        ps->ops = ops;

        INIT_LIST_HEAD(&ps->opstack);
        INIT_LIST_HEAD(&ps->postfix);
}

static char infix_next(struct filter_parse_state *ps)
{
        ps->infix.cnt--;

        return ps->infix.string[ps->infix.tail++];
}

static char infix_peek(struct filter_parse_state *ps)
{
        if (ps->infix.tail == strlen(ps->infix.string))
                return 0;

        return ps->infix.string[ps->infix.tail];
}

static void infix_advance(struct filter_parse_state *ps)
{
        ps->infix.cnt--;
        ps->infix.tail++;
}

static inline int is_precedence_lower(struct filter_parse_state *ps,
                                      int a, int b)
{
        return ps->ops[a].precedence < ps->ops[b].precedence;
}

static inline int is_op_char(struct filter_parse_state *ps, char c)
{
        int i;

        for (i = 0; strcmp(ps->ops[i].string, "OP_NONE"); i++) {
                if (ps->ops[i].string[0] == c)
                        return 1;
        }

        return 0;
}

static int infix_get_op(struct filter_parse_state *ps, char firstc)
{
        char nextc = infix_peek(ps);
        char opstr[3];
        int i;

        opstr[0] = firstc;
        opstr[1] = nextc;
        opstr[2] = '\0';

        for (i = 0; strcmp(ps->ops[i].string, "OP_NONE"); i++) {
                if (!strcmp(opstr, ps->ops[i].string)) {
                        infix_advance(ps);
                        return ps->ops[i].id;
                }
        }

        opstr[1] = '\0';

        for (i = 0; strcmp(ps->ops[i].string, "OP_NONE"); i++) {
                if (!strcmp(opstr, ps->ops[i].string))
                        return ps->ops[i].id;
        }

        return OP_NONE;
}

static inline void clear_operand_string(struct filter_parse_state *ps)
{
        memset(ps->operand.string, '\0', MAX_FILTER_STR_VAL);
        ps->operand.tail = 0;
}

static inline int append_operand_char(struct filter_parse_state *ps, char c)
{
        if (ps->operand.tail == MAX_FILTER_STR_VAL - 1)
                return -EINVAL;

        ps->operand.string[ps->operand.tail++] = c;

        return 0;
}

static int filter_opstack_push(struct filter_parse_state *ps, int op)
{
        struct opstack_op *opstack_op;

        opstack_op = kmalloc(sizeof(*opstack_op), GFP_KERNEL);
        if (!opstack_op)
                return -ENOMEM;

        opstack_op->op = op;
        list_add(&opstack_op->list, &ps->opstack);

        return 0;
}

static int filter_opstack_empty(struct filter_parse_state *ps)
{
        return list_empty(&ps->opstack);
}

static int filter_opstack_top(struct filter_parse_state *ps)
{
        struct opstack_op *opstack_op;

        if (filter_opstack_empty(ps))
                return OP_NONE;

        opstack_op = list_first_entry(&ps->opstack, struct opstack_op, list);

        return opstack_op->op;
}

static int filter_opstack_pop(struct filter_parse_state *ps)
{
        struct opstack_op *opstack_op;
        int op;

        if (filter_opstack_empty(ps))
                return OP_NONE;

        opstack_op = list_first_entry(&ps->opstack, struct opstack_op, list);
        op = opstack_op->op;
        list_del(&opstack_op->list);

        kfree(opstack_op);

        return op;
}

static void filter_opstack_clear(struct filter_parse_state *ps)
{
        while (!filter_opstack_empty(ps))
                filter_opstack_pop(ps);
}

static char *curr_operand(struct filter_parse_state *ps)
{
        return ps->operand.string;
}

static int postfix_append_operand(struct filter_parse_state *ps, char *operand)
{
        struct postfix_elt *elt;

        elt = kmalloc(sizeof(*elt), GFP_KERNEL);
        if (!elt)
                return -ENOMEM;

        elt->op = OP_NONE;
        elt->operand = kstrdup(operand, GFP_KERNEL);

        if (!elt->operand) {
                kfree(elt);
                return -ENOMEM;
        }

        list_add_tail(&elt->list, &ps->postfix);

        return 0;
}

static int postfix_append_op(struct filter_parse_state *ps, int op)
{
        struct postfix_elt *elt;

        elt = kmalloc(sizeof(*elt), GFP_KERNEL);
        if (!elt)
                return -ENOMEM;

        elt->op = op;
        elt->operand = NULL;

        list_add_tail(&elt->list, &ps->postfix);

        return 0;
}

static void postfix_clear(struct filter_parse_state *ps)
{
        struct postfix_elt *elt;

        while (!list_empty(&ps->postfix)) {
                elt = list_first_entry(&ps->postfix, struct postfix_elt, list);
                list_del(&elt->list);
                kfree(elt->operand);
                kfree(elt);
        }
}

static int filter_parse(struct filter_parse_state *ps)
{
        int in_string = 0;
        int op, top_op;
        char ch;

        while ((ch = infix_next(ps))) {
                if (ch == '"') {
                        in_string ^= 1;
                        continue;
                }

                if (in_string)
                        goto parse_operand;

                if (isspace(ch))
                        continue;

                if (is_op_char(ps, ch)) {
                        op = infix_get_op(ps, ch);
                        if (op == OP_NONE) {
                                parse_error(ps, FILT_ERR_INVALID_OP, 0);
                                return -EINVAL;
                        }

                        if (strlen(curr_operand(ps))) {
                                postfix_append_operand(ps, curr_operand(ps));
                                clear_operand_string(ps);
                        }

                        while (!filter_opstack_empty(ps)) {
                                top_op = filter_opstack_top(ps);
                                if (!is_precedence_lower(ps, top_op, op)) {
                                        top_op = filter_opstack_pop(ps);
                                        postfix_append_op(ps, top_op);
                                        continue;
                                }
                                break;
                        }

                        filter_opstack_push(ps, op);
                        continue;
                }

                if (ch == '(') {
                        filter_opstack_push(ps, OP_OPEN_PAREN);
                        continue;
                }

                if (ch == ')') {
                        if (strlen(curr_operand(ps))) {
                                postfix_append_operand(ps, curr_operand(ps));
                                clear_operand_string(ps);
                        }

                        top_op = filter_opstack_pop(ps);
                        while (top_op != OP_NONE) {
                                if (top_op == OP_OPEN_PAREN)
                                        break;
                                postfix_append_op(ps, top_op);
                                top_op = filter_opstack_pop(ps);
                        }
                        if (top_op == OP_NONE) {
                                parse_error(ps, FILT_ERR_UNBALANCED_PAREN, 0);
                                return -EINVAL;
                        }
                        continue;
                }
parse_operand:
                if (append_operand_char(ps, ch)) {
                        parse_error(ps, FILT_ERR_OPERAND_TOO_LONG, 0);
                        return -EINVAL;
                }
        }

        if (strlen(curr_operand(ps)))
                postfix_append_operand(ps, curr_operand(ps));

        while (!filter_opstack_empty(ps)) {
                top_op = filter_opstack_pop(ps);
                if (top_op == OP_NONE)
                        break;
                if (top_op == OP_OPEN_PAREN) {
                        parse_error(ps, FILT_ERR_UNBALANCED_PAREN, 0);
                        return -EINVAL;
                }
                postfix_append_op(ps, top_op);
        }

        return 0;
}

static struct filter_pred *create_pred(int op, char *operand1, char *operand2)
{
        struct filter_pred *pred;

        pred = kzalloc(sizeof(*pred), GFP_KERNEL);
        if (!pred)
                return NULL;

        pred->field_name = kstrdup(operand1, GFP_KERNEL);
        if (!pred->field_name) {
                kfree(pred);
                return NULL;
        }

        strcpy(pred->regex.pattern, operand2);
        pred->regex.len = strlen(pred->regex.pattern);

        pred->op = op;

        return pred;
}

static struct filter_pred *create_logical_pred(int op)
{
        struct filter_pred *pred;

        pred = kzalloc(sizeof(*pred), GFP_KERNEL);
        if (!pred)
                return NULL;

        pred->op = op;

        return pred;
}

static int check_preds(struct filter_parse_state *ps)
{
        int n_normal_preds = 0, n_logical_preds = 0;
        struct postfix_elt *elt;

        list_for_each_entry(elt, &ps->postfix, list) {
                if (elt->op == OP_NONE)
                        continue;

                if (elt->op == OP_AND || elt->op == OP_OR) {
                        n_logical_preds++;
                        continue;
                }
                n_normal_preds++;
        }

        if (!n_normal_preds || n_logical_preds >= n_normal_preds) {
                parse_error(ps, FILT_ERR_INVALID_FILTER, 0);
                return -EINVAL;
        }

        return 0;
}

static int replace_preds(struct ftrace_event_call *call,
                         struct event_filter *filter,
                         struct filter_parse_state *ps,
                         char *filter_string,
                         bool dry_run)
{
        char *operand1 = NULL, *operand2 = NULL;
        struct filter_pred *pred;
        struct postfix_elt *elt;
        int err;
        int n_preds = 0;

        err = check_preds(ps);
        if (err)
                return err;

        list_for_each_entry(elt, &ps->postfix, list) {
                if (elt->op == OP_NONE) {
                        if (!operand1)
                                operand1 = elt->operand;
                        else if (!operand2)
                                operand2 = elt->operand;
                        else {
                                parse_error(ps, FILT_ERR_TOO_MANY_OPERANDS, 0);
                                return -EINVAL;
                        }
                        continue;
                }

                if (n_preds++ == MAX_FILTER_PRED) {
                        parse_error(ps, FILT_ERR_TOO_MANY_PREDS, 0);
                        return -ENOSPC;
                }

                if (elt->op == OP_AND || elt->op == OP_OR) {
                        pred = create_logical_pred(elt->op);
                        goto add_pred;
                }

                if (!operand1 || !operand2) {
                        parse_error(ps, FILT_ERR_MISSING_FIELD, 0);
                        return -EINVAL;
                }

                pred = create_pred(elt->op, operand1, operand2);
add_pred:
                if (!pred)
                        return -ENOMEM;
                err = filter_add_pred(ps, call, filter, pred, dry_run);
                filter_free_pred(pred);
                if (err)
                        return err;

                operand1 = operand2 = NULL;
        }

        return 0;
}

static int replace_system_preds(struct event_subsystem *system,
                                struct filter_parse_state *ps,
                                char *filter_string)
{
        struct ftrace_event_call *call;
        bool fail = true;
        int err;

        list_for_each_entry(call, &ftrace_events, list) {
                struct event_filter *filter = call->filter;

                if (strcmp(call->class->system, system->name) != 0)
                        continue;

                /* try to see if the filter can be applied */
                err = replace_preds(call, filter, ps, filter_string, true);
                if (err)
                        continue;

                /* really apply the filter */
                filter_disable_preds(call);
                err = replace_preds(call, filter, ps, filter_string, false);
                if (err)
                        filter_disable_preds(call);
                else {
                        call->flags |= TRACE_EVENT_FL_FILTERED;
                        replace_filter_string(filter, filter_string);
                }
                fail = false;
        }

        if (fail) {
                parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
                return -EINVAL;
        }
        return 0;
}

int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
{
        int err;
        struct filter_parse_state *ps;

        mutex_lock(&event_mutex);

        err = init_preds(call);
        if (err)
                goto out_unlock;

        if (!strcmp(strstrip(filter_string), "0")) {
                filter_disable_preds(call);
                remove_filter_string(call->filter);
                goto out_unlock;
        }

        err = -ENOMEM;
        ps = kzalloc(sizeof(*ps), GFP_KERNEL);
        if (!ps)
                goto out_unlock;

        filter_disable_preds(call);
        replace_filter_string(call->filter, filter_string);

        parse_init(ps, filter_ops, filter_string);
        err = filter_parse(ps);
        if (err) {
                append_filter_err(ps, call->filter);
                goto out;
        }

        err = replace_preds(call, call->filter, ps, filter_string, false);
        if (err)
                append_filter_err(ps, call->filter);
        else
                call->flags |= TRACE_EVENT_FL_FILTERED;
out:
        filter_opstack_clear(ps);
        postfix_clear(ps);
        kfree(ps);
out_unlock:
        mutex_unlock(&event_mutex);

        return err;
}

int apply_subsystem_event_filter(struct event_subsystem *system,
                                 char *filter_string)
{
        int err;
        struct filter_parse_state *ps;

        mutex_lock(&event_mutex);

        err = init_subsystem_preds(system);
        if (err)
                goto out_unlock;

        if (!strcmp(strstrip(filter_string), "0")) {
                filter_free_subsystem_preds(system);
                remove_filter_string(system->filter);
                goto out_unlock;
        }

        err = -ENOMEM;
        ps = kzalloc(sizeof(*ps), GFP_KERNEL);
        if (!ps)
                goto out_unlock;

        replace_filter_string(system->filter, filter_string);

        parse_init(ps, filter_ops, filter_string);
        err = filter_parse(ps);
        if (err) {
                append_filter_err(ps, system->filter);
                goto out;
        }

        err = replace_system_preds(system, ps, filter_string);
        if (err)
                append_filter_err(ps, system->filter);

out:
        filter_opstack_clear(ps);
        postfix_clear(ps);
        kfree(ps);
out_unlock:
        mutex_unlock(&event_mutex);

        return err;
}

#ifdef CONFIG_PERF_EVENTS

void ftrace_profile_free_filter(struct perf_event *event)
{
        struct event_filter *filter = event->filter;

        event->filter = NULL;
        __free_preds(filter);
}

int ftrace_profile_set_filter(struct perf_event *event, int event_id,
                              char *filter_str)
{
        int err;
        struct event_filter *filter;
        struct filter_parse_state *ps;
        struct ftrace_event_call *call = NULL;

        mutex_lock(&event_mutex);

        list_for_each_entry(call, &ftrace_events, list) {
                if (call->event.type == event_id)
                        break;
        }

        err = -EINVAL;
        if (&call->list == &ftrace_events)
                goto out_unlock;

        err = -EEXIST;
        if (event->filter)
                goto out_unlock;

        filter = __alloc_preds();
        if (IS_ERR(filter)) {
                err = PTR_ERR(filter);
                goto out_unlock;
        }

        err = -ENOMEM;
        ps = kzalloc(sizeof(*ps), GFP_KERNEL);
        if (!ps)
                goto free_preds;

        parse_init(ps, filter_ops, filter_str);
        err = filter_parse(ps);
        if (err)
                goto free_ps;

        err = replace_preds(call, filter, ps, filter_str, false);
        if (!err)
                event->filter = filter;

free_ps:
        filter_opstack_clear(ps);
        postfix_clear(ps);
        kfree(ps);

free_preds:
        if (err)
                __free_preds(filter);

out_unlock:
        mutex_unlock(&event_mutex);

        return err;
}

#endif /* CONFIG_PERF_EVENTS */