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

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Message-ID: <4b728523-2e82-42f1-997c-792ce8e3219f@email.android.com>
Date:	Thu, 08 May 2014 06:50:18 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Sven Joachim <svenjoac@....de>
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

Actually it could use KVM instead of CPU emulation on nearly all modern processors...

On May 7, 2014 11:43:59 PM PDT, Sven Joachim <svenjoac@....de> wrote:
>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

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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