Messages in this thread | | | Date | Sat, 19 Jun 2021 20:13:15 -0700 | From | "Andy Lutomirski" <> | Subject | Re: [RFC PATCH 1/4] x86/entry/nmi: Switch to the entry stack b efore switching to the thread stack |
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On Sat, Jun 19, 2021, at 3:51 PM, Thomas Gleixner wrote: > On Tue, Jun 01 2021 at 14:52, Lai Jiangshan wrote: > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > > > Current kernel has no code to enforce data breakpoint not on the thread > > stack. If there is any data breakpoint on the top area of the thread > > stack, there might be problem. > > And because the kernel does not prevent data breakpoints on the thread > stack we need to do more complicated things in the already horrible > entry code instead of just doing the obvious and preventing data > breakpoints on the thread stack?
Preventing breakpoints on the thread stack is a bit messy: it’s possible for a breakpoint to be set before the address in question is allocated for the thread stack.
None of this is NMI-specific. #DB itself has the same problem. We could plausibly solve it differently by disarming breakpoints in the entry asm before switching stacks. I’m not sure how much I like that approach.
> > Confused. > > Thanks, > > tglx >
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