linux-kernel - Re: [PATCH 1/4] perf tools: unwind: ensure unwind hooks return negative errorno.

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Message-ID: <55239590.2020109@huawei.com>
Date:	Tue, 7 Apr 2015 16:30:08 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>, <acme@...nel.org>,
	<jolsa@...nel.org>, <mingo@...hat.com>
CC:	<namhyung@...nel.org>, <lizefan@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] perf tools: unwind: ensure unwind hooks return negative
 errorno.

Hi folks,

I'm rethinking --map-adjustment now, and I believe what we need should be something
like 'perf inject', which allows us to inject fake mmap events into perf.data to
make 'perf report' believe some //anon memory are file based mapping. Patch 2/4 - 4/4
seem not useful now. However, patch 1/4 is still useful because it is a bugfix. Could
you please drop the other 3 patches and merge this one?

Thank you.

On 2015/4/1 20:41, Wang Nan wrote:
> On 2015/4/1 20:12, Jiri Olsa wrote:
>> On Wed, Apr 01, 2015 at 10:33:12AM +0000, Wang Nan wrote:
>>> According to man pages of libunwind, unwind hooks should return
>>> 'negative value of one of the unw_error_t error-codes', they are
>>> different from generic error code. In addition, access_dso_mem()
>>> returns '!(size == sizeof(*data))', compiler never ensure it is
>>> negative when failure, which causes libunwind get undesire value
>>> when accessing //anon memory.
>>>
>>> This patch fixes this problem by force returning negative value when
>>> error, instead of returning 'ret' itself when it is non-zero.
>>
>> hum, how about find_proc_info callback.. should it follow the same rules?
>>
> 
> Yes, but it only returns -EINVAL and dwarf_search_unwind_table(....). The latter
> one is part of libunwind so we can trust it returns negative when fail.
> 
>> thanks,
>> jirka
>>
> 
> 
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