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Commit e8808c10 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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tracing/filters: support for filters of dynamic sized arrays 



Currently the filtering infrastructure supports well the
numeric types and fixed sized array types.

But the recently added __string() field uses a specific
indirect offset mechanism which requires a specific
predicate. Until now it wasn't supported.

This patch adds this support and implies very few changes,
only a new predicate is needed, the management of this specific
field can be done through the usual string helpers in the
filtering infrastructure.

[ Impact: support all kinds of strings in the tracing filters ]

Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 8ae79a13

kernel/trace/trace_events_filter.c

+41 −3
Original line number Diff line number Diff line
@@ -151,6 +151,7 @@ static int filter_pred_or(struct filter_pred *pred __attribute((unused)), 
	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)

{
@@ -164,6 +165,30 @@ static int filter_pred_string(struct filter_pred *pred, void *event, 
	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)

{

	int str_loc = *(int *)(event + pred->offset);

	char *addr = (char *)(event + str_loc);

	int cmp, match;



	cmp = strncmp(addr, pred->str_val, pred->str_len);



	match = (!cmp) ^ pred->not;



	return match;

}



static int filter_pred_none(struct filter_pred *pred, void *event,

			    int val1, int val2)

{
@@ -446,10 +471,18 @@ static int filter_add_pred_fn(struct filter_parse_state *ps, 
	return 0;

}



enum {

	FILTER_STATIC_STRING = 1,

	FILTER_DYN_STRING

};



static int is_string_field(const char *type)

{

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

		return 1;

		return FILTER_STATIC_STRING;



	if (!strcmp(type, "__str_loc"))

		return FILTER_DYN_STRING;



	return 0;

}
@@ -512,6 +545,7 @@ static int filter_add_pred(struct filter_parse_state *ps, 
	struct ftrace_event_field *field;

	filter_pred_fn_t fn;

	unsigned long long val;

	int string_type;



	pred->fn = filter_pred_none;
@@ -536,8 +570,12 @@ static int filter_add_pred(struct filter_parse_state *ps, 
		return -EINVAL;

	}



	if (is_string_field(field->type)) {

	string_type = is_string_field(field->type);

	if (string_type) {

		if (string_type == FILTER_STATIC_STRING)

			fn = filter_pred_string;

		else

			fn = filter_pred_strloc;

		pred->str_len = field->size;

		if (pred->op == OP_NE)

			pred->not = 1;