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

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Message-ID: <551BE78A.6070800@huawei.com>
Date:	Wed, 1 Apr 2015 20:41:46 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	<acme@...nel.org>, <jolsa@...nel.org>, <namhyung@...nel.org>,
	<mingo@...hat.com>, <lizefan@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] perf tools: unwind: ensure unwind hooks return negative
 errorno.

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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