Re: [PATCH 2/4] x86/vdso: Use 32-bit CHECKFLAGS for compat vDSO

Thomas Weißschuh
2026-01-16T08:09:36Z

On Fri, Jan 16, 2026 at 08:49:12AM +0100, Arnd Bergmann wrote:
> On Fri, Jan 16, 2026, at 08:40, Thomas Weißschuh wrote:
> > When building the compat vDSO the CHECKFLAGS from the 64-bit kernel
> > are used. These are combined with the 32-bit CFLAGS. This confuses
> > sparse, producing false-positive warnings or potentially missing
> > real issues.
> >
> > Manually override the CHECKFLAGS for the compat vDSO with the correct
> > 32-bit configuration.
> >
> > Reported-by: Sun Jian <sun.jian.kdev@gmail.com>
> > Closes:
> > https://lore.kernel.org/lkml/20260114084529.1676356-1-sun.jian.kdev@gmail.com/
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
> Acked-by: Arnd Bergmann <arnd@arndb.de>
>
> > +CHECKFLAGS_32 := $(CHECKFLAGS) -U__x86_64__ -D__i386__ -m32
> > +
> > $(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
> > +$(obj)/vdso32.so.dbg: CHECKFLAGS = $(CHECKFLAGS_32)
>
> Have you checked if something like this is needed for x32 as well?

It didn't show up in my testing. I think this is explained by the x32 vDSO
being built as 64-bit and only converted to x32 afterwards.

Thomas