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

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Message-ID: <00a78980-6b9c-5d5b-ed01-b28bb34be022@arm.com>
Date:   Tue, 25 Jun 2019 14:40:38 +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 Qin,

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?

>>
>> 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