linux-kernel - Re: [PATCH] selftests: vDSO: Do not rely on $ARCH for vdso_test_getrandom && vdso_test

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Message-ID: <cae4fb76-224e-4858-a44a-1ebb71c25821@csgroup.eu>
Date: Mon, 2 Sep 2024 16:18:31 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org,
 Adhemerval Zanella <adhemerval.zanella@...aro.org>,
 Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH] selftests: vDSO: Do not rely on $ARCH for
 vdso_test_getrandom && vdso_test_chacha



Le 02/09/2024 à 15:57, Jason A. Donenfeld a écrit :
> On Mon, Sep 02, 2024 at 03:23:47PM +0200, Christophe Leroy wrote:
>>
>>
>> Le 02/09/2024 à 14:37, Mark Brown a écrit :
>>> On Mon, Sep 02, 2024 at 02:22:38PM +0200, Christophe Leroy wrote:
>>>
>>>> When vdso_test_getcpu doesn't find the vDSO entry point, it prints an error
>>>> text and returns KSFT_SKIP
>>>
>>>> I thought it would be more correct to have the same behaviour on
>>>> vdso_test_getrandom instead of trying to build it only when the underlying
>>>> kernel supports it.
>>>
>>> The problem is that the test incorporates assembler code so it simply
>>> won't build for architectures without explicit porting, the issue isn't
>>> if the target kernel supports it but rather that the test won't compile
>>> in the first place.
>>
>> Yes indeed and that was the purpose of my patch, have a macro in
>> vdso_config.h to tell where the assembler code is:
>>
>> diff --git a/tools/testing/selftests/vDSO/vdso_config.h
>> b/tools/testing/selftests/vDSO/vdso_config.h
>> index 740ce8c98d2e..693920471160 100644
>> --- a/tools/testing/selftests/vDSO/vdso_config.h
>> +++ b/tools/testing/selftests/vDSO/vdso_config.h
>> @@ -47,6 +47,7 @@
>>    #elif defined(__x86_64__)
>>    #define VDSO_VERSION		0
>>    #define VDSO_NAMES		1
>> +#define VDSO_GETRANDOM	
>> "../../../../arch/x86/entry/vdso/vgetrandom-chacha.S"
>>    #elif defined(__riscv__) || defined(__riscv)
>>    #define VDSO_VERSION		5
>>    #define VDSO_NAMES		1
>>
>>
>> And then:
>>
>> diff --git a/tools/testing/selftests/vDSO/vdso_test_chacha-asm.S
>> b/tools/testing/selftests/vDSO/vdso_test_chacha-asm.S
>> new file mode 100644
>> index 000000000000..8e704165f6f2
>> --- /dev/null
>> +++ b/tools/testing/selftests/vDSO/vdso_test_chacha-asm.S
>> @@ -0,0 +1,7 @@
>> +#include "vdso_config.h"
>> +
>> +#ifdef VDSO_GETRANDOM
>> +
>> +#include VDSO_GETRANDOM
>> +
>> +#endif
>>
>> I thought it was a lot easier to handle if through necessary #ifdefs in
>> vdso_config.h that implementing an additional logic in Makefiles.
> 
> Yet it still tripped up the test robot, right?

Yes I need to look at that.

> 
> In general I'm not crazy about this approach.

I have the feeling I get things done easier with that approach. But if 
you feel better playing up with the makefile, I incline.