[PATCH 0/3] x86/debug: Fixes

[Peter Zijlstra]

Hi,

Triggered by the x86/entry rework, the resulting #DB cleanup (obviously :/)
broke something. Kyle reported that ptrace_get_debugreg(6) no longer contained
DR_STEP after PTRACE_SINGLESTEP which broke RR.

While looking at this, I realized that a kernel #DB should not consume a
userspace BTF, and equally a kernel #DB should not clobber the (userspace)
ptrace DR6 state. Both these have been busted since forever afaict.

I've added a few Wine folks to Cc, with the hope that they can test Wine
on 5.10-rc and make sure it all still works as expected. There have been
significant changes. Although hopefully it all works again after these
patches.