linux-kernel - Re: [PATCH] x86/uaccess: fix code generation in put

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Date:   Fri, 23 Oct 2020 13:55:22 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/uaccess: fix code generation in put_user()

Thanks, applied.

On Fri, Oct 23, 2020 at 1:32 PM Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
>
> I'm wondering if one would also need to make __ptr_pu and __ret_pu
> explicitly "%"_ASM_CX".

No, the "c"/"0" thing is much better, and makes it properly atomic wrt
the actual asm.

As mentioned to Andy, the "register asm()" thing is not uncommon and
often useful, but when you can specify the register directly in asm,
that's certainly simpler and more straightforward and preferred.

              Linus