On Sun, Jul 7, 2019 at 8:10 AM Andy Lutomirski <l...@kernel.org> wrote: > > On Thu, Jul 4, 2019 at 1:03 PM Peter Zijlstra <pet...@infradead.org> wrote: > > > > Despire the current efforts to read CR2 before tracing happens there > > still exist a number of possible holes: > > > > idtentry page_fault do_page_fault has_error_code=1 > > call error_entry > > TRACE_IRQS_OFF > > call trace_hardirqs_off* > > #PF // modifies CR2 > > > > CALL_enter_from_user_mode > > __context_tracking_exit() > > trace_user_exit(0) > > #PF // modifies CR2 > > > > call do_page_fault > > address = read_cr2(); /* whoopsie */ > > > > And similar for i386. > > > > Fix it by pulling the CR2 read into the entry code, before any of that > > stuff gets a chance to run and ruin things. > > Reviewed-by: Andy Lutomirski <l...@kernel.org> > > Subject to the discussion as to whether this is the right approach at all.
FWIW, I'm leaning toward suggesting that we apply the trivial tracing fix and backport *that*. Then, in -tip, we could revert it and apply this patch instead.
