Re: [PATCH] selftest/vDSO: Fix cross build for the random tests

["Jason A. Donenfeld" <Jason@zx2c4.com>]

On Fri, Aug 30, 2024 at 03:06:35PM +0100, Mark Brown wrote:
> Unlike the check for the standalone x86 test the check for building the
> vDSO getrandom and chacaha tests looks at the architecture for the host
> rather than the architecture for the target when deciding if they should
> be built. Since the chacha test includes some assembler code this means
> that cross building with x86 as either the target or host is broken. Use
> a check for ARCH instead.
> 
> Fixes: 4920a2590e91 ("selftests/vDSO: add tests for vgetrandom")
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> The x86_64 build is still broken for me because nothing installs
> tools/arch/x86_64/vdso/vgetrandom-chacha.S (I beleive it's supposed to
> be copied from ./arch/x86/entry/vdso/vgetrandom-chacha.S but I don't see
> how?) but this at least fixes all the other architectures.
> ---
>  tools/testing/selftests/vDSO/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile
> index e21e78aae24d..7fb59310718c 100644
> --- a/tools/testing/selftests/vDSO/Makefile
> +++ b/tools/testing/selftests/vDSO/Makefile
> @@ -10,7 +10,7 @@ ifeq ($(ARCH),$(filter $(ARCH),x86 x86_64))
>  TEST_GEN_PROGS += vdso_standalone_test_x86
>  endif
>  TEST_GEN_PROGS += vdso_test_correctness
> -ifeq ($(uname_M),x86_64)
> +ifeq ($(ARCH),$(filter $(ARCH),x86_64))

Actually... this doesn't work. Because:

ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)

The x86_64 gets turned into an x86. It's a little trickier when
considering subarch. I'll send a followup here and not queue this.