linux-kernel - [PATCH 2/2] tracing/filters: use strcmp() instead of strncmp()

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Date:	Fri, 29 May 2009 16:41:16 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>
CC:	Tom Zanussi <tzanussi@...il.com>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] tracing/filters: use strcmp() instead of strncmp()

Trace filter is not working normally:

  # echo 'name == et' > tracing/events/irq/irq_handler_entry/filter
  # echo 1 > tracing/events/irq/irq_handler_entry/enable
  # cat trace_pipe
      <idle>-0     [001]  1363.423175: irq_handler_entry: irq=18 handler=eth0
      <idle>-0     [001]  1363.934528: irq_handler_entry: irq=18 handler=eth0
      ...

It's because we pass to trace_define_field() the information of
__str_loc_##item, but not the actual string, so pred->str_len == field->size
== sizeof(unsigned short), thus it always compare at most 2 bytes when
filtering on __string() field.

Since __string() is dynamic size, we are not able to set field->size to
string length. Thus this patch uses strcmp() instead of strncmp().

[ Impact: make filter facility working normally for __string() field ]

Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---
 kernel/trace/trace.h               |    1 -
 kernel/trace/trace_events_filter.c |    7 ++-----
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6e735d4..ec8970b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -758,7 +758,6 @@ struct filter_pred {
 	filter_pred_fn_t fn;
 	u64 val;
 	char str_val[MAX_FILTER_STR_VAL];
-	int str_len;
 	char *field_name;
 	int offset;
 	int not;
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index a854eed..8362586 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -158,7 +158,7 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
 	char *addr = (char *)(event + pred->offset);
 	int cmp, match;
 
-	cmp = strncmp(addr, pred->str_val, pred->str_len);
+	cmp = strcmp(addr, pred->str_val);
 
 	match = (!cmp) ^ pred->not;
 
@@ -182,7 +182,7 @@ static int filter_pred_strloc(struct filter_pred *pred, void *event,
 	char *addr = (char *)(event + str_loc);
 	int cmp, match;
 
-	cmp = strncmp(addr, pred->str_val, pred->str_len);
+	cmp = strcmp(addr, pred->str_val);
 
 	match = (!cmp) ^ pred->not;
 
@@ -341,7 +341,6 @@ static void filter_clear_pred(struct filter_pred *pred)
 {
 	kfree(pred->field_name);
 	pred->field_name = NULL;
-	pred->str_len = 0;
 }
 
 static int filter_set_pred(struct filter_pred *dest,
@@ -576,7 +575,6 @@ static int filter_add_pred(struct filter_parse_state *ps,
 			fn = filter_pred_string;
 		else
 			fn = filter_pred_strloc;
-		pred->str_len = field->size;
 		if (pred->op == OP_NE)
 			pred->not = 1;
 		return filter_add_pred_fn(ps, call, pred, fn);
@@ -957,7 +955,6 @@ static struct filter_pred *create_pred(int op, char *operand1, char *operand2)
 	}
 
 	strcpy(pred->str_val, operand2);
-	pred->str_len = strlen(operand2);
 
 	pred->op = op;
 
-- 
1.5.4.rc3

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