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Message-ID: <56157F60.1000503@sr71.net>
Date: Wed, 7 Oct 2015 13:24:00 -0700
From: Dave Hansen <dave@...1.net>
To: Ingo Molnar <mingo@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Kees Cook <keescook@...gle.com>,
Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH 26/26] x86, pkeys: Documentation
On 10/03/2015 01:17 AM, Ingo Molnar wrote:
> Right now the native x86 PTE format allows two protection related bits for
> user-space pages:
>
> _PAGE_BIT_RW: if 0 the page is read-only, if 1 then it's read-write
> _PAGE_BIT_NX: if 0 the page is executable, if 1 then it's not executable
>
> As discussed previously, pkeys allows 'true execute only (--x)' mappings.
>
> Another possibility would be 'true write-only (-w-)' mappings.
How would those work?
Protection Keys has a Write-Disable and an Access-Disable bit. But,
Access-Disable denies _all_ data access to the region. There's no way
to allow only writes.
Or am I missing something?
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