linux-kernel - Re: How can I turn off/disable -O2/-Os optimization?

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Message-ID: <CAChaegmgw_8KsmOAt=WpHN6KTa9qkgh-EmHC-PGqCQxGRQ2U6w@mail.gmail.com>
Date:	Sat, 5 May 2012 23:00:48 -0300
From:	Renato Westphal <renatowestphal@...il.com>
To:	Zhihua Che <zhihua.che@...il.com>
Cc:	Randy Dunlap <rdunlap@...otime.net>, linux-kernel@...r.kernel.org
Subject: Re: How can I turn off/disable -O2/-Os optimization?

2012/4/2 Zhihua Che <zhihua.che@...il.com>:
> 在 2012年4月2日 上午12:49，Randy Dunlap <rdunlap@...otime.net> 写道：
>> On 04/01/2012 09:31 AM, Zhihua Che wrote:
>>
>>> Hi, everyone
>>>
>>>     I'm debugging linux kernel using kgdb/qemu， but I find that the
>>> execution order didn't math the program order usually.  I guess it was
>>> because the compiling optimization. So I decided to remove -O options
>>> in Makefiles.
>>>     First I removed -Ox in variables HOSTCFLAGS/HOSTCXXFLAGS in
>>> <src_root_dir>/Makefile around line 248 and -Ox in variable
>>> KBUILD_CFLAGS in <src_root_dir>/arch/x86/boot/Makefile around line 55.
>>> But it didn't work, the step execution still didn't follow the program
>>> order. Then I found I missed -Ox in KBUILD_CFLAGS in
>>> <src_root_dir>/Makefile around line 562, so I removed them, but this
>>> time, the compiling failed, complaining
>>>     rcupdate.h:917:2: error: size of unnamed array is negative
>>>    And finally, after grep, I find there are a load of -O2 option are
>>> assigned in a load of Makefiles. So, How could I disable -O
>>> optimization for debugging?
>>>
>>>    Thanks for any tips
>>> --
>>
>>
>> You could try the new CONFIG_READABLE_ASM patch:
>>  http://marc.info/?l=linux-kernel&m=133296079716268&w=2
>>
>>
>> --
>> ~Randy
>
> Hi,
>    I tried your patch, and it seemed not to work:-(. It still didn't
> follow the program order


Hi Zhihua Che,

Have you found a solution for this? I'm facing the same problem with KGDB..

-- 
Renato Westphal
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