Re: [PATCH v2 5/7] ubsan: Enable for all*config builds

Arnd Bergmann
2020-12-09T19:26:15Z

On Wed, Dec 9, 2020 at 7:46 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Dec 03, 2020 at 09:51:40AM +0100, Arnd Bergmann wrote:
> > On Thu, Dec 3, 2020 at 1:44 AM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > With UBSAN_OBJECT_SIZE disabled for GCC, only UBSAN_ALIGNMENT remained
> > > a noisy UBSAN option. Disable it for COMPILE_TEST so the rest of UBSAN
> > > can be used for full all*config builds or other large combinations.
> > >
> > > Link: https://lore.kernel.org/lkml/CAHk-=wgXW=YLxGN0QVpp-1w5GDd2pf1W-FqY15poKzoVfik2qA@mail.gmail.com/
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> >
> > Have you checked if this has a notable impact on allmodconfig compile speed
> > with gcc or clang? I think I've seen significant increases in build times before
> > with this, but I don't remember the actual magnitude.
> >
> > Making it 20% slower would probably be ok, but making it twice as slow might
> > be too much.
>
> And for Clang, it's about 7m40s before and 8m30s after, so roughly 12% slower.

Ok, that doesn't sound too bad then.

Arnd