On Tue, Jul 12, 2016 at 3:55 PM, H. Peter Anvin <[email protected]> wrote: > On 07/12/16 08:32, Dave Hansen wrote: >> On 07/09/2016 02:27 PM, Andy Lutomirski wrote: >>> is_prefetch in arch/x86/mm/fault.c can be called on a user address >>> that's not readable due to PKRU. This could break it. You might need >>> to add a get_user_exec or similar. >> >> Thanks for the heads-up. I think I'll just need a version that does >> something along the lines of stac/clac, but with PKRU. >> >> I think I can do it with an "_exec" variant of probe_kernel_address(), >> but it's a bit messy. >> > > Can this particular codepath even be executed on a PKRU-equipped > machine? I thought it was a bug fix for a specific AMD CPU line.
It can certainly be executed -- do_sigbus will execute it every time. But I guess it doesn't matter if it fails on a PKRU machine, because a failure will just report the signal, and the erratum case can't happen in the first place. > > -hpa > -- Andy Lutomirski AMA Capital Management, LLC
