linux-kernel - Re: [PATCH 2/4] tracing/filters: Fix MATCH_FULL filter matching for PTR

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Date:	Mon, 14 Dec 2009 09:40:56 +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 2/4] tracing/filters: Fix MATCH_FULL filter matching	for
 PTR_STRING

Frederic Weisbecker wrote:
> On Fri, Dec 11, 2009 at 05:59:06PM +0800, Li Zefan wrote:
>> MATCH_FULL matching for PTR_STRING is not working correctly:
>>
>>   # echo 'func == vt' > events/bkl/lock_kernel/filter
>>   # echo 1 > events/bkl/lock_kernel/enable
>>   ...
>>   # cat trace
>>    Xorg-1484  [000]  1973.392586: lock_kernel: ... func=vt_ioctl()
>>     gpm-1402  [001]  1974.027740: lock_kernel: ... func=vt_ioctl()
>>
>> We should pass to regex.match(..., len) the length (including '\0')
>> of the source string instead of the length of the pattern string.
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> 
> This patch is cool but it seems to also break middle and end
> matching (at least what was working with end matching :)
> 

No, it won't, unless I miss something.

I changed what value ptr_string passes the length param to match(),
but this param is not used in match_middle and match_end.

It does break match_front for ptr_string, but that's because
the mixture of 2 bugs happened to make things right. I can
sort this out by reordering the 2 patches.

> I know you fix that in the subsequent patches, but please
> avoid that. A fix should not bring another known bug,
> event if it's fixed in the same batch.
> 
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