linux-kernel - Re: [PATCH v2] x86, mem: move memmove to out of line assembler

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Message-ID: <202209271333.10AE3E1D@keescook>
Date:   Tue, 27 Sep 2022 13:36:08 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        llvm@...ts.linux.dev, Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2] x86, mem: move memmove to out of line assembler

On Tue, Sep 27, 2022 at 01:01:35PM -0700, Nick Desaulniers wrote:
> > Found it (need to use %di instead of %dx). With this changed, the kunit
> > test passes again:
> >
> 
> That was stupid of me, I updated the scratch register operand in the
> instruction 2 before the one at issue and forgot to update the operand
> for the register in question, breaking the swap.

No worries! It meant I got to do a very careful review of the port. :)

> Off thread, can you show me how to run the kunit tests, please?

It's literally just what I put in the original email. KUnit is super
easy to use. In the root of the kernel source tree, just run:

	./tools/testing/kunit/kunit.py run --arch=i386 memcpy

Without --arch, it'll default to um.

-- 
Kees Cook