linux-kernel - Re: [PATCH 2/2] x86-64/Xen: eliminate W+X mappings

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Date:   Tue, 12 Dec 2017 11:54:07 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Jan Beulich <JBeulich@...e.com>
Cc:     mingo@...e.hu, tglx@...utronix.de,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        hpa@...or.com
Subject: Re: [PATCH 2/2] x86-64/Xen: eliminate W+X mappings


* Jan Beulich <JBeulich@...e.com> wrote:

> >>> On 12.12.17 at 11:38, <mingo@...nel.org> wrote:
> > * Jan Beulich <JBeulich@...e.com> wrote:
> >> --- 4.15-rc3/arch/x86/xen/mmu_pv.c
> >> +++ 4.15-rc3-x86_64-Xen-avoid-W+X/arch/x86/xen/mmu_pv.c
> >> @@ -1902,6 +1902,16 @@ void __init xen_setup_kernel_pagetable(p
> >>  	/* Graft it onto L4[511][510] */
> >>  	copy_page(level2_kernel_pgt, l2);
> >>  
> >> +	/* Zap execute permission from the ident map. Due to the sharing of
> >> +	 * L1 entries we need to do this in the L2. */
> > 
> > please use the customary (multi-line) comment style:
> > 
> >   /*
> >    * Comment .....
> >    * ...... goes here.
> >    */
> > 
> > specified in Documentation/CodingStyle.
> 
> I would have but didn't because all other comments in this function
> use this (wrong) style. I've concluded that consistency is better
> here than matching the style doc. If the Xen maintainers tell me
> otherwise, I'll happily adjust the patch.

Then it should be cleaned up in a separate patch. The file is in arch/x86/ and 
both Documentation/CodingStyle and Linus's position is pretty unambiguous on this, 
there's no special exceptions for ugliness in arch/x86/ as far as I'm concerned.

Please guys fix this mess, NAK otherwise.

Thanks,

	Ingo