On Thu, 10 Nov 2016 12:35:59 +1100 Michael Ellerman <m...@ellerman.id.au> wrote:
> Nicholas Piggin <npig...@gmail.com> writes: > > > When exiting xmon with 'x' (exit and recover), oops_begin bails > > out immediately, but die then calls __die() and oops_end(), which > > cause a lot of bad things to happen. > > In fact oops_begin() returns 1, which oops_end() then passes directly to > raw_local_irq_restore() as flags. On 64-bit that actually works because > arch_local_irq_restore() takes just "en" (enable), not real flags. But > on 32-bit it's supposed to be the MSR value. So that's impressively > broken. Yeah, I guess most of the time you either go to debugger with sysrq, or in case of a crash don't try to graceful recover. When sending debug NMIs down via system reset it becomes a problem! > > > If the debugger was attached then went to graceful recovery, exit > > from die() immediately. > > Right. Crucially it doesn't change anything in terms of the actual logic > of oops_begin(), ie. previously oops_begin() did nothing prior to > calling debugger(), and after this patch that remains the same (which > you did mention above but just spelling it out for myself). Right. Thanks, Nick
