linux-kernel - Re: [PATCH] mm: provide a fallback for PAGE_KERNEL

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Date:   Wed, 9 May 2018 01:04:38 +0000
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>,
        Tony Luck <tony.luck@...el.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>, arnd@...db.de,
        gregkh@...uxfoundation.org, linux-arch@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Fenghua Yu <fenghua.yu@...el.com>,
        linux-ia64@...r.kernel.org
Subject: Re: [PATCH] mm: provide a fallback for PAGE_KERNEL_RO for
 architectures

On Fri, Apr 27, 2018 at 08:18:10PM -0700, Matthew Wilcox wrote:
> On Fri, Apr 27, 2018 at 05:15:26PM -0700, Luis R. Rodriguez wrote:
> > Some architectures do not define PAGE_KERNEL_RO, best we can do
> > for them is to provide a fallback onto PAGE_KERNEL. Remove the
> > hack from the firmware loader and move it onto the asm-generic
> > header, and document while at it the affected architectures
> > which do not have a PAGE_KERNEL_RO:
> > 
> >   o alpha
> >   o ia64
> >   o m68k
> >   o mips
> >   o sparc64
> >   o sparc
> 
> ia64 doesn't have it?
> 
> *fx: riffles through architecture book*
> 
> That seems like an oversight of the Linux port.  Tony, Fenghua, any thoughts?

Poke *Tony, Fenghua* ?

> (also, Luis, maybe move the PAGE_KERNEL_EXEC fallback the same way you
> moved the PAGE_KERNEL_RO fallback?)

Done. Will queue in the generic PAGE_KERNEL_EXEC patch to my series.

> --- >8 ---
> 
> ia64: Add PAGE_KERNEL_RO and PAGE_KERNEL_EXEC
> 
> The rest of the kernel was falling back to simple PAGE_KERNEL pages; using
> PAGE_KERNEL_RO and PAGE_KERNEL_EXEC provide better protection against
> unintended writes.
> 
> Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>

Nice, should I queue this into my series as well?

  Luis