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

[Andrew Lutomirski]

On Tue, Feb 21, 2012 at 11:03 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 02/21/2012 10:54 AM, Andrew Lutomirski wrote:
>>
>> uclibc hardcodes a call to the vsyscall gettimeofday implementation in
>> its locking primitives, which probably gives terrible performance, but
>> that's a separate issue.  I think do_emulate_vsyscall should send a
>> segfault if called by an x32 task -- there's some security benefit to
>> doing so, and there's unlikely to be any downside.
>>
>
> 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.

--Andy
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