Re: [PATCH 30/30] x32: Add x32 VDSO support

[H. Peter Anvin]

On 02/21/2012 11:29 AM, Andrew Lutomirski wrote:
>>
>> The vsyscall page shouldn't be mapped for x32 tasks...
> 
> How is that possible?  It lives in the fixmap and is presumably
> visible from any 64-bit code.
> 
> Admittedly, x32 tasks are probably somewhat difficult to trick into
> calling addresses with high bits set, but it's not necessarily
> impossible.
> 

Fair enough, and it's not necessarily all that hard either.

And it's visible even in a 32-bit task, although a 32-bit task has to
switch into 64-bit mode.  Yet another reason the vsyscall page needs to die.

I was having delusions that we could have a task-owned PDT in negative
space, but that would require unsharing the third level, too, which is
just way too messy.

	-hpa
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