Re: [RFC] selftests/x86: Add test_vsyscall

[Andy Lutomirski]

> On Jan 5, 2018, at 11:28 AM, Borislav Petkov <bp@xxxxxxxxx> wrote:
> 
>> On Fri, Jan 05, 2018 at 11:22:21AM -0800, Andy Lutomirski wrote:
>> It's emulated!  We catch the page fault and fake the whole thing :)
> 
> Then I'm really confused. It says "ro" above, which means _PAGE_RW is
> not set so page is read-only.
> 
> I must be missing something...
> 

It's meant to be read-only, user-acccessible, NX as far as the CPU is concerned.  When user code calls it, we get an instruction fetch fault, and the kernel fixes it up.

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