Hi Andrey, On Thu, Nov 08, 2018 at 03:48:10PM +0100, Andrey Konovalov wrote: > On Thu, Nov 8, 2018 at 3:36 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > Changes in v8: > > - Rebased onto 65102238 (4.20-rc1). > > - Added a note to the cover letter on why syscall wrappers/shims that untag > > user pointers won't work. > > - Added a note to the cover letter that this patchset has been merged into > > the Pixel 2 kernel tree. > > - Documentation fixes, in particular added a list of syscalls that don't > > support tagged user pointers. > > I've changed the documentation to be more specific, please take a look. > > I haven't done anything about adding a way for the user to find out > that the kernel supports this ABI extension. I don't know what would > the the preferred way to do this, and we haven't received any comments > on that from anybody else. Probing "on some innocuous syscall > currently returning -EFAULT on tagged pointer arguments" works though, > as you mentioned. We've had some internal discussions and also talked to some people at Plumbers. I think the best option is to introduce an AT_FLAGS bit to describe the ABI relaxation on tagged pointers. Vincenzo is going to propose a patch on top of this series. > As mentioned in the cover letter, this patchset has been merged into > the Pixel 2 kernel tree. I just hope it's not enabled on production kernels, it would introduce a user ABI that may differ from what ends up upstream. -- Catalin
