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

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Date:	Wed, 07 May 2014 11:18:49 +0200
From:	Sven Joachim <svenjoac@....de>
To:	Alexandre Julliard <julliard@...ehq.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>,
	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 2014-04-14 09:48 +0200, Alexandre Julliard wrote:

> Linus Torvalds <torvalds@...ux-foundation.org> writes:
>
>> On Fri, Apr 11, 2014 at 11:45 AM, Brian Gerst <brgerst@...il.com> wrote:
>>>
>>> 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.
>>
>> Afaik 64-bit windows doesn't support 16-bit binaries, so I just
>> assumed Wine wouldn't do it either on x86-64. Not for any real
>> technical reasons, though.
>>
>> HOWEVER. I'd like to hear something more definitive than "I haven't
>> tested recently". The "we don't break user space" is about having
>> actual real *users*, not about test programs.
>>
>> Are there people actually using 16-bit old windows programs under
>> wine? That's what matters.

It seems that at least some 32-bit programs are also broken, since after
upgrading the kernel to 3.14.3 I can no longer start my old chess
database program:

,----
| % file CB70.exe 
| CB70.exe: PE32 executable (GUI) Intel 80386, for MS Windows
| % LANG=C wine CB70.exe
| modify_ldt: Invalid argument
| modify_ldt: Invalid argument
| modify_ldt: Invalid argument
| modify_ldt: Invalid argument
| modify_ldt: Invalid argument
`----

And here it just hangs, with wineboot.exe taking 100% CPU.  I had to
kill first wineboot.exe and then CB70.exe. :-(

> Yes, there is still a significant number of users, and we still
> regularly get bug reports about specific 16-bit apps. It would be really
> nice if we could continue to support them on x86-64, particularly since
> Microsoft doesn't ;-)

I would rather not set up a virtual machine just for wine (I don't have
Windows anymore).

Cheers,
       Sven
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