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

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Message-ID: <ZtXEUZC_jRBSAG9k@zx2c4.com>
Date: Mon, 2 Sep 2024 15:57:37 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
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

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?

In general I'm not crazy about this approach.