linux-kernel - Re: [PATCH v3 07/11] kentry: Make entry/exit_to_user

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Date:   Sat, 13 Mar 2021 17:18:39 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 07/11] kentry: Make entry/exit_to_user_mode() arm64-only

On Mon, Mar 8, 2021 at 2:06 AM Mark Rutland <mark.rutland@....com> wrote:
>
> On Thu, Mar 04, 2021 at 11:06:00AM -0800, Andy Lutomirski wrote:
> > exit_to_user_mode() does part, but not all, of the exit-to-user-mode work.
> > It's used only by arm64, and arm64 should stop using it (hint, hint!).
> > Compile it out on other architectures to minimize the chance of error.
>
> For context, I do plan to move over, but there's a reasonable amount of
> preparatory work needed first (e.g. factoring out the remaining asm
> entry points, and reworking our pseudo-NMI management to play nicely
> with the common entry code).
>
> > enter_from_user_mode() is a legacy way to spell
> > kentry_enter_from_user_mode().  It's also only used by arm64.  Give it
> > the same treatment.
>
> I think you can remove these entirely, no ifdeferry necessary.
>
> Currently arm64 cannot select CONFIG_GENERIC_ENTRY, so we open-code
> copies of these in arch/arm64/kernel/entry-common.c, and doesn't use
> these common versions at all. When we move over to the common code we
> can move directly to the kentry_* versions. If we are relying on the
> prototypes anywhere, that's a bug as of itself.

I got faked out!  Fixed for the next version.