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>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index e1b653f7e1ca..0d883dc057d6 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -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;                                                  \
         }                                                               \