linux-kernel - Re: [PATCH 3/4] x86/boot: use -fno-builtin-bcmp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202008181224.4C682B38@keescook>
Date:   Tue, 18 Aug 2020 12:24:40 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tony Luck <tony.luck@...el.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Joe Perches <joe@...ches.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Daniel Axtens <dja@...ens.net>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Yury Norov <yury.norov@...il.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Bruce Ashfield <bruce.ashfield@...il.com>,
        Marco Elver <elver@...gle.com>,
        Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>,
        Andi Kleen <ak@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dávid Bolvanský <david.bolvansky@...il.com>,
        Eli Friedman <efriedma@...cinc.com>
Subject: Re: [PATCH 3/4] x86/boot: use -fno-builtin-bcmp

On Mon, Aug 17, 2020 at 03:02:11PM -0700, Nick Desaulniers wrote:
> We're reverting
> commit 5f074f3e192f ("lib/string.c: implement a basic bcmp")
> in favor of -fno-builtin-bcmp. Remove the additional definition here,
> too.
> 
> arch/x86/purgatory/Makefile uses -ffreestanding, so there's no risk of
> this libcall optimization occurring for arch/x86/boot/purgatory.ro.
> 
> arch/x86/boot/Makefile resets KBUILD_CFLAGS, so make sure to reset this
> flag that was set for the top level Makefile.
> 
> Fixes: 4ce97317f41d ("x86/purgatory: Do not use __builtin_memcpy and __builtin_memset")
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook