linux-hardening - Re: [PATCH v2] x86/build: don't build CONFIG_X86

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Message-ID: <CAKwvOd=7ZDMhnX6Da5_ZMM9yLgrnhjwwPhYwO-RT-3yrPy+RLw@mail.gmail.com>
Date:   Thu, 3 Feb 2022 12:45:49 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     x86@...nel.org, Arvind Sankar <nivedita@...m.mit.edu>,
        Fangrui Song <maskray@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] x86/build: don't build CONFIG_X86_32 as -ffreestanding

On Thu, Feb 3, 2022 at 12:40 PM Kees Cook <keescook@...omium.org> wrote:
>
> From: Nick Desaulniers <ndesaulniers@...gle.com>
>
> -ffreestanding typically inhibits "libcall optimizations" where calls to
> certain library functions can be replaced by the compiler in certain
> cases to calls to other library functions that may be more efficient.
> This can be problematic for embedded targets that don't provide full
> libc implementations.

While the bcmp shenanigans were ultimately resolved by
commit 5f074f3e192f ("lib/string.c: implement a basic bcmp")
(and this popped up again in
commit 1e1b6d63d634 ("lib/string.c: implement stpcpy")
).  I'm still very much in favor of this patch, and should have
pursued it. Thanks for resending!

-- 
Thanks,
~Nick Desaulniers