linux-kernel - Re: [PATCH v7 3/3] x86: Make the GDT remapping read-only on 64-bit

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Message-ID: <20170314210424.GA5023@amd>
Date:   Tue, 14 Mar 2017 22:04:24 +0100
From:   Pavel Machek <pavel@....cz>
To:     Thomas Garnier <thgarnie@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
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Subject: Re: [PATCH v7 3/3] x86: Make the GDT remapping read-only on 64-bit

On Tue 2017-03-14 10:05:08, Thomas Garnier wrote:
> This patch makes the GDT remapped pages read-only to prevent corruption.
> This change is done only on 64-bit.
> 
> The native_load_tr_desc function was adapted to correctly handle a
> read-only GDT. The LTR instruction always writes to the GDT TSS entry.
> This generates a page fault if the GDT is read-only. This change checks
> if the current GDT is a remap and swap GDTs as needed. This function was
> tested by booting multiple machines and checking hibernation works
> properly.
> 
> KVM SVM and VMX were adapted to use the writeable GDT. On VMX, the
> per-cpu variable was removed for functions to fetch the original GDT.
> Instead of reloading the previous GDT, VMX will reload the fixmap GDT as
> expected. For testing, VMs were started and restored on multiple
> configurations.
> 
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>

Can we get the same change for 32-bit, too? Growing differences
between 32 and 64 bit are a bit of a problem...
								Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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