linux-kernel - Re: [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk

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Message-ID: <f55d9563c432db15f8a768381103abe8e986a42b.camel@intel.com>
Date:   Wed, 1 Feb 2023 17:32:30 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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CC:     "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
Subject: Re: [PATCH v5 18/39] mm: Handle faultless write upgrades for shstk

On Wed, 2023-02-01 at 10:03 +0100, David Hildenbrand wrote:
> > 
> > The other problem is that one of NULL passers is not for kernel
> > memory.
> > huge_pte_mkwrite() calls pte_mkwrite(). Shadow stack memory can't
> > be
> > created with MAP_HUGETLB, so it is not needed. Using
> > pte_mkwrite_kernel() would look weird in this case, but making
> > huge_pte_mkwrite() take a VMA would be for no reason. Maybe making
> > huge_pte_mkwrite() take a VMA is the better of those two options.
> > Or
> > keep the NULL semantics...  Any thoughts?
> 
> Well, the reason would be consistency. From a core-mm point of view
> it 
> makes sense to handle this all consistency, even if the single user 
> (x86) wouldn't strictly require it right now.
> 
> I'd just pass in the VMA and call it a day :)

Ok, I'll give it a spin.