linux-kernel - Re: [v3 04/12] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions

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Date:   Thu, 25 Oct 2018 16:16:26 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Andrew Lutomirski <luto@...nel.org>
Cc:     "Bae, Chang Seok" <chang.seok.bae@...el.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Metzger, Markus T" <markus.t.metzger@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [v3 04/12] x86/fsgsbase/64: Enable FSGSBASE instructions in the
 helper functions

On Wed, Oct 24, 2018 at 12:16 PM Andy Lutomirski <luto@...nel.org> wrote:
>
> On Tue, Oct 23, 2018 at 11:43 AM Chang S. Bae <chang.seok.bae@...el.com> wrote:

> > +/*
> > + * Interrupts are disabled here. Out of line to be protected from kprobes.
> > + */
> > +static noinline __kprobes unsigned long rd_inactive_gsbase(void)
> > +{
> > +       unsigned long gsbase, flags;
> > +
> > +       local_irq_save(flags);
> > +       native_swapgs();
> > +       gsbase = rdgsbase();
> > +       native_swapgs();
> > +       local_irq_restore(flags);
> > +
> > +       return gsbase;
> > +}
>
> Please fold this into its only caller and make *that* noinline.
>

On further reading of the whole series, I retract this particular
comment.  But I do think that __rdgsbase_inactive() would be a better
name.