linux-kernel - Re: linux-next: Tree for May 14 (objtool 2/2)

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Message-ID: <202005291229.37DE69E@keescook>
Date:   Fri, 29 May 2020 12:30:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: linux-next: Tree for May 14 (objtool 2/2)

On Fri, May 29, 2020 at 12:54:56PM -0500, Josh Poimboeuf wrote:
> On Thu, May 28, 2020 at 11:06:32PM -0700, Kees Cook wrote:
> > diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
> > index 929211039bac..27bcc2568c95 100644
> > --- a/lib/Kconfig.ubsan
> > +++ b/lib/Kconfig.ubsan
> > @@ -63,7 +63,7 @@ config UBSAN_SANITIZE_ALL
> >  config UBSAN_ALIGNMENT
> >         bool "Enable checks for pointers alignment"
> >         default !HAVE_EFFICIENT_UNALIGNED_ACCESS
> > -       depends on !X86 || !COMPILE_TEST
> > +       depends on !UBSAN_TRAP
> >         help
> >           This option enables the check of unaligned memory accesses.
> >           Enabling this option on architectures that support unaligned
> > 
> > How about that?
> 
> But I thought you said the alignment traps might be useful on other
> arches?  Should it be
> 
> 	depends on !X86 || !UBSAN_TRAP
> 
> ?

I was just trying to avoid objtool there, but really, UBSAN_TRAP is
likely insane for unaligned access checks entirely. If anyone ever needs
it, they can adjust. :)

-- 
Kees Cook