Re: [PATCH] selftests: vDSO: Do not rely on $ARCH for vdso_test_getrandom && vdso_test_chacha

[Christophe Leroy]

Le 01/09/2024 à 20:02, Jason A. Donenfeld a écrit :
> On Sun, Sep 01, 2024 at 08:00:30PM +0200, Christophe Leroy wrote:
> > 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.
> > >
> > > What about, instead, something like below, replacing the other commit?
> >
> > I need to look at it in more details and perfom a test, but after first
> > look I can't figure out how it would work.
> >
> > When I build selftests,
> >
> > to build 32 bits selftests I do:
> >
> > 	make ARCH=powerpc CROSS_COMPILE=ppc-linux-
> >
> > to build a 64 bits BE selftests I do:
> >
> > 	make ARCH=powerpc CROSS_COMPILE=powerpc64-linux-
> >
> > to build a 64 bits LE selftests I do:
> >
> > 	make ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-
> >
> >
> > I addition, in case someone does the build on a native platform directly,
> >
> > On 32 bits, uname -m returns 'ppc'
> > On 64 bits, uname -m returns 'ppc64'
> > On 64 bits little endian, uname -m returns 'ppc64le'
> >
> > How would this fit in the logic where IIUC you just remove '_64' from
> > 'x86_64' to get 'x86'
>
> Huh? That's not what tools/scripts/Makefile.arch does.

Hum ... yes sorry I looked at it too quickly and mixed things up with 
the other patch.

Nevertheless, if I understand well what tools/scripts/Makefile.arch does 
on an x86_64 for instance:

uname -m returns x86_64
HOSTARCH = x86 (sed -e s/x86_64/x86)
ARCH = x86
SRCARCH = x86

If you build with make ARCH=x86_64,
SRCARCH = x86

So I still can't see how you can use that to know if it is a x86_64 or not.

I don't see either what could be the result for powerpc.

By the way, in your patch I don't think you can use CONFIG_X86_32, 
CONFIG symbols are not known when building selftests.

Christophe