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Date: Tue, 23 Aug 2011 16:04:17 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
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Subject: Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re:
 [RFC] weird crap with vdso on uml/i386)
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On 08/23/2011 02:20 PM, Linus Torvalds wrote:
> On Tue, Aug 23, 2011 at 2:08 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> Again, can we steal one of the padding fields to use for that state
>> variable?  We have two 16-bit padding fields; one for cs and one for ss.
> 
> We can steal them for passing the information to the user, but no, I
> don't think we can use them to then take the information *from* the
> user.
> 
> Somebody may well be setting up a 'pt_regs' structure on his own, and
> simply not fill in the padding, resulting in random data in those
> fields.
> 

That would be fine, I'd think... just gives the user space application
enough information to know how it would have to reshuffle the registers
if it needs to.

	-hpa