On Tue, 2018-09-25 at 09:36:47 UTC, Michael Neuling wrote: > Current we store the userspace r1 to PACATMSCRATCH before finally > saving it to the thread struct. > > In theory an exception could be taken here (like a machine check or > SLB miss) that could write PACATMSCRATCH and hence corrupt the > userspace r1. The SLB fault currently doesn't touch PACATMSCRATCH, but > others do. > > We've never actually seen this happen but it's theoretically > possible. Either way, the code is fragile as it is. > > This patch saves r1 to the kernel stack (which can't fault) before we > turn MSR[RI] back on. PACATMSCRATCH is still used but only with > MSR[RI] off. We then copy r1 from the kernel stack to the thread > struct once we have MSR[RI] back on. > > Suggested-by: Breno Leitao <lei...@debian.org> > Signed-off-by: Michael Neuling <mi...@neuling.org>
Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/96dc89d526ef77604376f06220e3d2 cheers
