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

H. Peter Anvin
2014-05-08T13:51:09Z

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@gmx.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

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