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Subject: Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL
To: Andy Lutomirski <luto@kernel.org>
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From: Dave Hansen <dave.hansen@linux.intel.com>
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Date: Thu, 9 Nov 2017 22:31:30 -0800
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On 11/09/2017 06:25 PM, Andy Lutomirski wrote:
> Here are two proposals to address this without breaking vsyscalls.
> 
> 1. Set NX on low mappings that are _PAGE_USER.  Don't set NX on high
> mappings but, optionally, warn if you see _PAGE_USER on any address
> that isn't the vsyscall page.
> 
> 2. Ignore _PAGE_USER entirely and just mark the EFI mm as special so
> KAISER doesn't muck with it.

These are totally doable.  But, what's the big deal with breaking native
vsyscall?  We can still do the emulation so nothing breaks: it is just slow.