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

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Message-ID: <87vbtgahxs.fsf@turtle.gmx.de>
Date:	Thu, 08 May 2014 08:43:59 +0200
From:	Sven Joachim <svenjoac@....de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexandre Julliard <julliard@...ehq.org>,
	Brian Gerst <brgerst@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	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 2014-05-07 19:09 +0200, H. Peter Anvin wrote:

> On 05/07/2014 09:57 AM, Linus Torvalds wrote:
>> 
>> Afaik, 16-bit programs under wine already need
>> 
>>   echo 0 > /proc/sys/vm/mmap_min_addr
>> 
>> because they want to map things at address 0, so this isn't a new concept.
>> 
>
> I think that applies to DOSEMU, but not to Wine.

DOSEMU does no longer need it either.  If vm.mmap_min_addr is > 0, it
turns on CPU emulation, which it has to use anyway due to lack of vm86
mode.

> Sven: if you have the ability to build your own kernel, could you also
> try the "x86/espfix" branch of the git tree:
>
> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/
>
> (clone URLs:)
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
>
> ... to make sure the proper solution works for you?

Works fine here, thanks.

> I'm somewhat curious if this program you have is actually a 32-bit
> program or if it is really a 16-bit program wrapped in a 32-bit
> installer of some kind.  Hard to know without seeing the program in
> question.

The main application (a chess database program) is 32-bit, but it comes
with several 16-bit analysis engines that are loaded on startup (I see
them in lsof output), so that's the situation described by Alexandre.

Cheers,
       Sven
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