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Commit e12c09cf authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add NOT to filtering logic 

Ted noticed that he could not filter on an event for a bit being cleared.
That's because the filtering logic only tests event fields with a limited
number of comparisons which, for bit logic, only include "&", which can
test if a bit is set, but there's no good way to see if a bit is clear.

This adds a way to do: !(field & 2048)

Which returns true if the bit is not set, and false otherwise.

Note, currently !(field1 == 10 && field2 == 15) is not supported.
That is, the 'not' only works for direct comparisons, not for the
AND and OR logic.

Link: http://lkml.kernel.org/r/20141202021912.GA29096@thunk.org
Link: http://lkml.kernel.org/r/20141202120430.71979060@gandalf.local.home



Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Suggested-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 6a06bdbf

kernel/trace/trace_events_filter.c

+18 −2
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ enum filter_op_ids 
	OP_GT,

	OP_GE,

	OP_BAND,

	OP_NOT,

	OP_NONE,

	OP_OPEN_PAREN,

};
@@ -67,6 +68,7 @@ static struct filter_op filter_ops[] = { 
	{ OP_GT,	">",		5 },

	{ OP_GE,	">=",		5 },

	{ OP_BAND,	"&",		6 },

	{ OP_NOT,	"!",		6 },

	{ OP_NONE,	"OP_NONE",	0 },

	{ OP_OPEN_PAREN, "(",		0 },

};
@@ -85,6 +87,7 @@ enum { 
	FILT_ERR_MISSING_FIELD,

	FILT_ERR_INVALID_FILTER,

	FILT_ERR_IP_FIELD_ONLY,

	FILT_ERR_ILLEGAL_NOT_OP,

};



static char *err_text[] = {
@@ -101,6 +104,7 @@ static char *err_text[] = { 
	"Missing field name and/or value",

	"Meaningless filter expression",

	"Only 'ip' field is supported for function trace",

	"Illegal use of '!'",

};



struct opstack_op {
@@ -139,6 +143,7 @@ struct pred_stack { 
	int			index;

};



/* If not of not match is equal to not of not, then it is a match */

#define DEFINE_COMPARISON_PRED(type)					\

static int filter_pred_##type(struct filter_pred *pred, void *event)	\

{									\
@@ -166,7 +171,7 @@ static int filter_pred_##type(struct filter_pred *pred, void *event) \ 
		break;							\

	}								\

									\

	return match;							\

	return !!match == !pred->not;					\

}



#define DEFINE_EQUALITY_PRED(size)					\
@@ -1028,7 +1033,7 @@ static int init_pred(struct filter_parse_state *ps, 
	}



	if (pred->op == OP_NE)

		pred->not = 1;

		pred->not ^= 1;



	pred->fn = fn;

	return 0;
@@ -1590,6 +1595,17 @@ static int replace_preds(struct ftrace_event_call *call, 
			continue;

		}



		if (elt->op == OP_NOT) {

			if (!n_preds || operand1 || operand2) {

				parse_error(ps, FILT_ERR_ILLEGAL_NOT_OP, 0);

				err = -EINVAL;

				goto fail;

			}

			if (!dry_run)

				filter->preds[n_preds - 1].not ^= 1;

			continue;

		}



		if (WARN_ON(n_preds++ == MAX_FILTER_PRED)) {

			parse_error(ps, FILT_ERR_TOO_MANY_PREDS, 0);

			err = -ENOSPC;