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

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Date:   Tue, 27 Sep 2022 10:03:51 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
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>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] x86, mem: move memmove to out of line assembler

Oh, yeah my patch essentially _is_
commit 9599ec0471de ("x86-64, mem: Convert memmove() to assembly file
and fix return value bug")
but for 32b (and no return value bug).  I should probably amend a
reference to that in the commit message for this patch.

Also, I'm missing an EXPORT_SYMBOL in my v1, so modules that reference
memmove will fail to build during modpost. v2 is required.

On Fri, Sep 23, 2022 at 11:06 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> But I'm looking at that x86-64 memcpy_orig, and I think it looks
> fairly good as a template for doing the same on x86-32. And we could
> get rid of the duplication on the x86-64 side.

Is the suggestion that 64b memcpy_orig could be replaced with __memmove?

Sorry, I'm not sure I follow either suggestions for code reuse opportunities.

Also, any ideas which machines for QEMU don't have ERMS for testing
these non-ERMS implementations?

>
> That said, your patch looks fine too, as a "minimal changes" thing.
>
>                 Linus

--
Thanks,
~Nick Desaulniers