Commit 1a891cf1 authored Jun 12, 2013 by Steven Rostedt

tracing: Add binary '&' filter for events

There are some cases when filtering on a set flag of a field of a tracepoint
is useful. But currently the only filtering commands for numbered fields
is ==, !=, <, <=, >, >=. This does not help when you just want to trace if
a specific flag is set. For example:

 > # sudo trace-cmd record -e brcmfmac:brcmf_dbg -f 'level & 0x40000'
 > disable all
 > enable brcmfmac:brcmf_dbg
 > path = /sys/kernel/debug/tracing/events/brcmfmac/brcmf_dbg/enable
 > (level & 0x40000)
 > ^
 > parse_error: Invalid operator
 >

When trying to trace brcmf_dbg when level has its 1 << 18 bit set, the
filter fails to perform.

By allowing a binary '&' operation, this gives the user the ability to
test a bit.

Note, a binary '|' is not added, as it doesn't make sense as fields must
be compared to constants (for now), and ORing a constant will always return
true.

Link: http://lkml.kernel.org/r/1371057385.9844.261.camel@gandalf.local.home



Suggested-by: Arend van Spriel <arend@broadcom.com>
Tested-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent aaf6ac0f

Documentation/trace/events.txt

+1 −1

Original line number	Diff line number	Diff line
		@@ -183,7 +183,7 @@ The relational-operators depend on the type of the field being tested:

		The operators available for numeric fields are:

		==, !=, <, <=, >, >=
		==, !=, <, <=, >, >=, &

		And for string fields they are:

kernel/trace/trace_events_filter.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -44,6 +44,7 @@ enum filter_op_ids
		OP_LE,
		OP_GT,
		OP_GE,
		OP_BAND,
		OP_NONE,
		OP_OPEN_PAREN,
		};
		@@ -54,6 +55,7 @@ struct filter_op {
		int precedence;
		};

		/* Order must be the same as enum filter_op_ids above */
		static struct filter_op filter_ops[] = {
		{ OP_OR, "\|\|", 1 },
		{ OP_AND, "&&", 2 },
		@@ -64,6 +66,7 @@ static struct filter_op filter_ops[] = {
		{ OP_LE, "<=", 5 },
		{ OP_GT, ">", 5 },
		{ OP_GE, ">=", 5 },
		{ OP_BAND, "&", 6 },
		{ OP_NONE, "OP_NONE", 0 },
		{ OP_OPEN_PAREN, "(", 0 },
		};
		@@ -156,6 +159,9 @@ static int filter_pred_##type(struct filter_pred pred, void event) \
		case OP_GE: \
		match = (*addr >= val); \
		break; \
		case OP_BAND: \
		match = (*addr & val); \
		break; \
		default: \
		break; \
		} \

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