linux-kernel - Re: [PATCH 3/4] tracing/filters: Fix MATCH_FRONT

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Message-ID: <4B259849.6030205@cn.fujitsu.com>
Date:	Mon, 14 Dec 2009 09:43:37 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
	Wenji Huang <wenji.huang@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] tracing/filters: Fix MATCH_FRONT_ONLY filter	matching

Frederic Weisbecker wrote:
> On Fri, Dec 11, 2009 at 05:59:28PM +0800, Li Zefan wrote:
>> MATCH_FRONT_ONLY matching works exactly as MATCH_FULL.
>>
>> We should pass the length of the pattern to strncmp().
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
>> ---
>>  kernel/trace/trace_events_filter.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
>> index c8eb1c0..bd492ce 100644
>> --- a/kernel/trace/trace_events_filter.c
>> +++ b/kernel/trace/trace_events_filter.c
>> @@ -262,7 +262,7 @@ static int regex_match_full(char *str, struct regex *r, int len)
>>  
>>  static int regex_match_front(char *str, struct regex *r, int len)
>>  {
>> -	if (strncmp(str, r->pattern, len) == 0)
>> +	if (strncmp(str, r->pattern, r->len) == 0)
>>  		return 1;
>>  	return 0;
>>  }
> 
> 
> But it was working before the fix to match full.

No, it was not working for dyn_string and static_string.
And as I explained it happened to work for ptr_string by
the mixture of 2 bugs.

> The MATCH_FULL fix is nice but it also brings a new bug that
> is fixed in this patch.
> 
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