linux-kernel - Re: [tip:x86/asm 3/3] lib/bug.c:135: undefined reference to `__start___bug

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Date:   Fri, 31 Mar 2017 08:27:27 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        tipbuild@...or.com, Ingo Molnar <mingo@...nel.org>
Subject: Re: [tip:x86/asm 3/3] lib/bug.c:135: undefined reference to
 `__start___bug_table'

On Thu, Mar 30, 2017 at 05:53:27PM +0200, Peter Zijlstra wrote:
>On Thu, Mar 30, 2017 at 05:49:27PM +0200, Peter Zijlstra wrote:
>> On Thu, Mar 30, 2017 at 09:02:31PM +0800, kbuild test robot wrote:
>> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
>> > head:   19d436268dde95389c616bb3819da73f0a8b28a8
>> > commit: 19d436268dde95389c616bb3819da73f0a8b28a8 [3/3] debug: Add _ONCE() logic to report_bug()
>> > config: arm-efm32_defconfig (attached as .config)
>> > compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
>> > reproduce:
>> >         wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>> >         chmod +x ~/bin/make.cross
>> >         git checkout 19d436268dde95389c616bb3819da73f0a8b28a8
>> >         # save the attached .config to linux build tree
>> >         make.cross ARCH=arm
>> >
>> > All errors (new ones prefixed by >>):
>> >
>> >    lib/lib.a(bug.o): In function `find_bug':
>> > >> lib/bug.c:135: undefined reference to `__start___bug_table'
>> > >> lib/bug.c:135: undefined reference to `__stop___bug_table'
>>
>> Blergh.. this cures it for me.
>>
>> Ideally all those would use RW_DATA_SECTION, but alas.
>>
>
>> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
>> index c74ae9c..c8a3b61 100644
>> --- a/arch/x86/kernel/vmlinux.lds.S
>> +++ b/arch/x86/kernel/vmlinux.lds.S
>> @@ -146,6 +146,7 @@ SECTIONS
>>  		_edata = .;
>>  	} :data
>>
>> +	BUG_TABLE
>>
>>  	. = ALIGN(PAGE_SIZE);
>>  	__vvar_page = .;
>
>Also, I have absolutely 0 clues as to why x86 builds without this :/

Yes there are no x86 build failures with this error message.
It only occurs in arm and c6x.

Regards,
Fengguang