Re: [PATCH v5 22/34] x86/fred: FRED initialization code

[Peter Zijlstra]

On Fri, Mar 17, 2023 at 02:32:28PM -0700, H. Peter Anvin wrote:
> The purpose of separate stacks for NMI, #DB and #MC *in the kernel*
> (remember that user space faults are always taken on stack level 0) is
> to avoid overflowing the kernel stack. #DB in the kernel would imply
> the use of a kernel debugger.

Perf (and through it bpf) also has access to #DB. They can set
breakpoints on kernel instructions/memory just fine provided permission
etc.