Michael Neuling <mi...@neuling.org> writes: > On Tue, 2018-09-25 at 22:00 +1000, Michael Ellerman wrote: >> Michael Neuling <mi...@neuling.org> writes: >> > 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> >> > --- >> > arch/powerpc/kernel/tm.S | 8 +++++++- >> > 1 file changed, 7 insertions(+), 1 deletion(-) >> > >> > diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S >> > index 701b0f5b09..8207816a1e 100644 >> > --- a/arch/powerpc/kernel/tm.S >> > +++ b/arch/powerpc/kernel/tm.S >> > @@ -178,6 +178,12 @@ _GLOBAL(tm_reclaim) >> > >> > std r11, GPR11(r1) /* Temporary stash */ >> > >> > + /* Move r1 to kernel stack in case PACATMSCRATCH is used once >> > + * we turn on RI >> > + */ >> >> I see we still need to send you to Comment Formatting Re-Education Camp. > > The rest of that file has they style, so I'm just keeping with that. I can > submit a patch later to fix them all up.
Sure, but let's not add new ones. And yeah fixing them all up in another patch would be good. cheers
