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

[Arnd Bergmann]

On Thu, Dec 3, 2020 at 1:44 AM Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxxxxxxx/
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

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.

       Arnd