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SubjectRe: [PATCH 1/4] ubsan: Move cc-option tests into Kconfig
On Sun, Oct 04, 2020 at 12:08:47AM -0700, Nathan Chancellor wrote:
> On Fri, Oct 02, 2020 at 03:15:24PM -0700, Kees Cook wrote:
> > Instead of doing if/endif blocks with cc-option calls in the UBSAN
> > Makefile, move all the tests into Kconfig and use the Makefile to
> > collect the results.
> >
> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
>
> I tested menuconfig to make sure all the flags when CONFIG_UBSAN_MISC is
> flipped.
>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> Tested-by: Nathan Chancellor <natechancellor@gmail.com>

Awesome, thank you!

> One comment below.
>
> > [...]
> > diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> > index 9716dab06bc7..72862da47baf 100644
> > --- a/scripts/Makefile.ubsan
> > +++ b/scripts/Makefile.ubsan
> > @@ -1,37 +1,21 @@
> > # SPDX-License-Identifier: GPL-2.0
> >
> > -export CFLAGS_UBSAN :=
> > +# -fsanitize=* options makes GCC less smart than usual and
> > +# increases the number of 'maybe-uninitialized' false-positives.
> > +ubsan-cflags-$(CONFIG_UBSAN) += $(call cc-disable-warning, maybe-uninitialized)
>
> Is this just to force -Wno-maybe-uninitialized even when W=2?
> -Wmaybe-uninitialized is already disabled globally after
> commit 78a5255ffb6a ("Stop the ad-hoc games with
> -Wno-maybe-initialized"). I feel like it might be worth a comment in
> case that changes in the future but maybe that is a bit much.
>
> > [...]
> > - # -fsanitize=* options makes GCC less smart than usual and
> > - # increase number of 'maybe-uninitialized false-positives
> > - CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)

It's just a direct copying of the existing logic, but into the new
"ubsan-cflags-y" style. But yes, AFAICT, that was the intent when it was
added in commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized
warning for "make W=1"").

So for this patch, I kept the logic as it was.

--
Kees Cook

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