linux-kernel - RE: [PATCH 2/2] perf tools: Fix find_perf_probe_point_from

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Message-ID: <50399556C9727B4D88A595C8584AAB3752606DC9@GSjpTKYDCembx32.service.hitachi.net>
Date:	Fri, 6 Nov 2015 06:28:58 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'acme@...nel.org'" <acme@...nel.org>
CC:	"'Wang Nan'" <wangnan0@...wei.com>,
	"namhyung@...nel.org" <namhyung@...nel.org>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	"pi3orama@....com" <pi3orama@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jolsa@...nel.org" <jolsa@...nel.org>
Subject: RE: [PATCH 2/2] perf tools: Fix find_perf_probe_point_from_map()
 which incorrectly returns success

From: acme@...nel.org [mailto:acme@...nel.org]
>
>Em Thu, Nov 05, 2015 at 02:08:48PM +0000, 平松雅巳 / HIRAMATU，MASAMI escreveu:
>> From: Wang Nan [mailto:wangnan0@...wei.com]
>> >
>> >It is possible that find_perf_probe_point_from_map() fails to find
>> >symbol but still returns 0 because of an small error when coding:
>> >find_perf_probe_point_from_map() set 'ret' to error code at first,
>> >but also use it to hold return value of
>> >kernel_get_symbol_address_by_name().
>>
>> OK, I didn't expect that there is a symbol which can be found by
>> kernel_get_symbol_address_by_name() but not by __find_kernel_function()...
>
>> Would you have any example of the error?
>>
>> >
>> >This patch resets 'ret' to error even kernel_get_symbol_address_by_name()
>> >success, so if !sym, the whole function returns error correctly.
>>
>> Hmm, that sounds tricky. I'd rather like to add *psym to kernel_get_symbol_address_by_name()
>> to save symbol and don't use __find_kernel_function() instead.
>
>Tricky? I don't think so, suboptimal? possibly, but it fixes an error,
>so should be processed quickly, right? I'm applying his patch and then
>whatever improvement can be done on top.

OK, then I'll send an improvement patch.

Thanks,

>
>- Arnaldo