On Thu, Jul 23, 2015 at 01:38:33PM -0700, Linus Torvalds wrote: > And the "take them and disable them" is really simple. No "am I in an > NMI contect" thing (because that leads to the whole question about > "what is NMI context"). That's not the real rule anyway. > > No, make it very simple and straightforward. Make the test be "uhhuh, > I got a #DB in kernel mode, and interrupts were disabled - I know I'm > going to return with "ret", so I'm just going to have to disable this > breakpoint". > > Nothing clever. Nothing subtle. Nothing that needs "this range of > instructions is magical". No. Just a very simple rule: if the context > we return to is kernel mode and interrupts are disabled, we're using > 'ret', so we cannot suppress debug faults. > > Did I miss something? There were a lot of emails flying around, but I > *thought* I saw them all..
So the NMI could trigger userspace debug register faults, and simply disabling them would make the whole debug register thing entirely unreliable. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
