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

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Message-ID: <fe8ea6a6-71d7-4cfc-b20b-fa0a7f39a4be@csgroup.eu>
Date: Mon, 2 Sep 2024 14:22:38 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 Adhemerval Zanella <adhemerval.zanella@...aro.org>,
 Xi Ruoyao <xry111@...111.site>, broonie@...nel.org
Subject: Re: [PATCH] selftests: vDSO: Do not rely on $ARCH for
 vdso_test_getrandom && vdso_test_chacha

Hi Jason,

Le 01/09/2024 à 15:22, Jason A. Donenfeld a écrit :
> Hi Christophe,
> 
> Hmm, I'm not so sure I like this very much. I think it's important for
> these tests to fail when an arch tries to hook up the function to the
> vDSO, but it's still not exported for some reason. This also regresses
> the ARCH=x86_64 vs ARCH=x86 thing, which SRCARCH fixes.
> 
If we take the exemple of getcpu:

Only powerpc and s390 implement __kernel_getcpu.
Until recently, it was implemented on ppc64 but not on ppc32

Only loongarch, riscv and x86 implement __vdso_getcpu.

Nevertheless, vdso_test_getcpu is always builts, regardless of the 
architecture.

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.

Christophe