lkml.org 
[lkml]   [2021]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 1/4] x86/entry/nmi: Switch to the entry stack b efore switching to the thread stack


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
>

\
 
 \ /
  Last update: 2021-06-20 05:14    [W:0.220 / U:1.256 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site