netdev - Re: [net-next:master 488/665] verifier.c:undefined reference to `_

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Date:   Sat, 11 Nov 2017 17:51:34 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Fengguang Wu <fengguang.wu@...el.com>,
        Alexei Starovoitov <ast@...com>
Cc:     kbuild-all@...org, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: Re: [net-next:master 488/665] verifier.c:undefined reference to
 `__multi3'

Le 11/11/17 à 17:34, Fengguang Wu a écrit :
> On Sun, Nov 12, 2017 at 09:23:52AM +0800, Alexei Starovoitov wrote:
>> On 11/12/17 9:18 AM, Fengguang Wu wrote:
>>> On Sun, Nov 12, 2017 at 09:14:14AM +0800, Alexei Starovoitov wrote:
>>>> On 11/12/17 8:23 AM, kbuild test robot wrote:
>>>>> tree:
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
>>>>> master
>>>>> head:   7c5556decd0a629e9ee02e93653f75ba7b7da03c
>>>>> commit: 638f5b90d46016372a8e3e0a434f199cc5e12b8c [488/665] bpf:
>>>>> reduce verifier memory consumption
>>>>> config: mips-64r6el_defconfig (attached as .config)
>>>>> compiler: mips64el-linux-gnuabi64-gcc (Debian 7.2.0-11) 7.2.0
>>>>> reproduce:
>>>>>         git checkout 638f5b90d46016372a8e3e0a434f199cc5e12b8c
>>>>>         # save the attached .config to linux build tree
>>>>>         make.cross ARCH=mips
>>>>>
>>>>> All errors (new ones prefixed by >>):
>>>>>
>>>>>    kernel/bpf/verifier.o: In function
>>>>> `realloc_verifier_state.isra.19':
>>>>>>> verifier.c:(.text+0x36fc): undefined reference to `__multi3'
>>>>
>>>> that's a known issue with gcc 7 on mips that is "optimizing"
>>>> normal 64-bit multiply into 128-bit variant.
>>>> Nothing to fix on the kernel side.
>>>
>>> Good to know that! Do you think it a good idea to blacklist __multi3
>>> errors in mips builds?
>>
>> I would do so. yes.
> 
> OK.
> 
>> Though digging further this function was added to
>> arch/sparc/lib/multi3.S
>> since gcc doing the same "optimization" there.
>> Adding asm code doesn't look right to me. I'd rather push
>> gcc folks to avoid such codegen.
> 
> Sure, I just forwarded the original report to GCC list.

Thomas encountered a similar problem, reported on linux-mips here:

https://www.linux-mips.org/archives/linux-mips/2017-08/msg00041.html
-- 
Florian