linux-kernel - Re: "arm64: vdso: Substitute gettimeofday() with C implementation" breaks clang build

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Message-ID: <5113362e-1256-6712-6ce8-9599b1806cf1@arm.com>
Date:   Tue, 25 Jun 2019 15:11:21 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Qian Cai <cai@....pw>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        natechancellor@...il.com, ndesaulniers@...gle.com
Subject: Re: "arm64: vdso: Substitute gettimeofday() with C implementation"
 breaks clang build

Hi Qian,

On 25/06/2019 14:51, Qian Cai wrote:
> On Tue, 2019-06-25 at 14:40 +0100, Vincenzo Frascino wrote:
>> On 25/06/2019 13:56, Qian Cai wrote:
>>> On Tue, 2019-06-25 at 13:47 +0100, Vincenzo Frascino wrote:
>>>> Hi Qian,
>>>>
>>>> On 25/06/2019 13:16, Qian Cai wrote:
>>>>> The linux-next commit "arm64: vdso: Substitute gettimeofday() with C
>>>>> implementation" [1] breaks clang build.
>>>>>
>>>>> error: invalid value 'tiny' in '-mcode-model tiny'
>>>>> make[1]: *** [scripts/Makefile.build:279:
>>>>> arch/arm64/kernel/vdso/vgettimeofday.o] Error 1
>>>>> make[1]: *** Waiting for unfinished jobs....
>>>>> make: *** [arch/arm64/Makefile:180: vdso_prepare] Error 2
>>>>>
>>>>> [1] https://patchwork.kernel.org/patch/11009663/
>>>>>
>>>>
>>>> I am not sure what does exactly break from your report. Could you please
>>>> provide
>>>> more details?
>>>
>>> Here is the config to reproduce.
>>>
>>> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
>>>
>>> # make CC=clang -j $(nr_cpus)
>>>
>>> I can get it working again by removing "-mcmodel=tiny" in
>>> arch/arm64/kernel/vdso/Makefile
>>>
>>
>> With your defconfig I can't still reproduce the problem. Which version of
>> clang
>> are you using?
> 
> Compiler: clang version 7.0.1 (tags/RELEASE_701/final)
> 

I am using clang 8.0.0. Could you please try with it and see if the issue goes away?

Thanks,
Vincenzo

>>
>>>>
>>>> On my env:
>>>>
>>>> $ make mrproper && make defconfig && make CC=clang HOSTCC=clang -j$(nproc)
>>>>
>>>> ...
>>>>
>>>> arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT is clang, the compat vDSO
>>>> will
>>>> not
>>>> be built
>>>>
>>>> ...
>>>>
>>>>   LDS     arch/arm64/kernel/vdso/vdso.lds
>>>>   AS      arch/arm64/kernel/vdso/note.o
>>>>   AS      arch/arm64/kernel/vdso/sigreturn.o
>>>>   CC      arch/arm64/kernel/vdso/vgettimeofday.o
>>>>   LD      arch/arm64/kernel/vdso/vdso.so.dbg
>>>>   VDSOCHK arch/arm64/kernel/vdso/vdso.so.dbg
>>>>   VDSOSYM include/generated/vdso-offsets.h
>>>>
>>>> ...
>>>>
>>>>   LD      vmlinux.o
>>>>   MODPOST vmlinux.o
>>>>   MODINFO modules.builtin.modinfo
>>>>   KSYM    .tmp_kallsyms1.o
>>>>   KSYM    .tmp_kallsyms2.o
>>>>   LD      vmlinux
>>>>   SORTEX  vmlinux
>>>>   SYSMAP  System.map
>>>>   Building modules, stage 2.
>>>>   OBJCOPY arch/arm64/boot/Image
>>>>   MODPOST 483 modules
>>>>
>>
>>

-- 
Regards,
Vincenzo