Re: [RFC] selftests/x86: Add test_vsyscall

[Andy Lutomirski]

> On Jan 5, 2018, at 11:10 AM, Borislav Petkov <bp@xxxxxxxxx> wrote:
> 
>> On Fri, Jan 05, 2018 at 10:45:49AM -0800, Andy Lutomirski wrote:
>> Not _PAGE_RW.  Probably _PAGE_USER somewhere in the hierarchy.
> 
> Yeah, just realized that. But it must be somewhere in the PT hierarchy
> because:
> 
> 0xffffffffff600000-0xffffffffff601000           4K USR ro                     NX pte
> 
> So something up needs to take _PAGE_USER too.
> 
> But WTF does it say NX there for and still can execute the vsyscall
> test? Oh boy, what a mess...
> 

It's emulated!  We catch the page fault and fake the whole thing :)

> -- 
> Regards/Gruss,
>    Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.