linux-kernel - Re: [tip:x86/urgent] x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels

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Message-ID: <CAMzpN2jj3dwQG7qC__8zLPhkg_ER6n4CcNxa5eg7okRN+k_VUA@mail.gmail.com>
Date:	Fri, 11 Apr 2014 14:45:12 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	stable <stable@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [tip:x86/urgent] x86-64, modify_ldt: Ban 16-bit segments on
 64-bit kernels

On Fri, Apr 11, 2014 at 2:41 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Apr 11, 2014 at 11:27 AM, Brian Gerst <brgerst@...il.com> wrote:
>> Is this bug really still present in modern CPUs?  This change breaks
>> running 16-bit apps in Wine.  I have a few really old games I like to
>> play on occasion, and I don't have a copy of Win 3.11 to put in a VM.
>
> Ok, so you actually do this on x86-64, and it currently works? For
> some reason I thought that 16-bit windows apps already didn't work.
>
> Because if we have working users of this, then I don't think we can do
> the "we don't support 16-bit segments", or at least we need to make it
> runtime configurable.
>
>              Linus

I haven't tested it recently but I do know it has worked on 64-bit
kernels.  There is no reason for it not to, the only thing not
supported in long mode is vm86.  16-bit protected mode is unchanged.
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