On Tue, Aug 20, 2013 at 4:05 PM, Anton Blanchard <an...@samba.org> wrote: > > The VSX alignment handler needs to write out the existing VSX > state to memory before operating on it (flush_vsx_to_thread()). > If we take a VSX alignment exception in the kernel bad things > will happen. It looks like we could write the kernel state out > to the user process, or we could handle the kernel exception > using data from the user process (depending if MSR_VSX is set > or not). > > Worse still, if the code to read or write the VSX state causes an > alignment exception, we will recurse forever. I ended up with > hundreds of megabytes of kernel stack to look through as a result. > > Floating point and SPE code have similar issues but already include > a user check. Add the same check to emulate_vsx(). >
Can you say what will happen when you apply this patch. ie It produces one oops rather than megabytes of crap making it easier to debug. Also, can you give a clue as to how you can hit this since it should never happen in the first place. I assume it's some LE corner case... Mikey > Signed-off-by: Anton Blanchard <an...@samba.org> > --- > > Index: b/arch/powerpc/kernel/align.c > =================================================================== > --- a/arch/powerpc/kernel/align.c > +++ b/arch/powerpc/kernel/align.c > @@ -651,6 +651,10 @@ static int emulate_vsx(unsigned char __u > int sw = 0; > int i, j; > > + /* userland only */ > + if (unlikely(!user_mode(regs))) > + return 0; > + > flush_vsx_to_thread(current); > > if (reg < 32) > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
