Messages in this thread | | | Date | Mon, 25 May 2020 11:18:32 +0200 | From | Peter Zijlstra <> | Subject | Re: x86/entry vs kgdb |
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On Mon, May 25, 2020 at 10:36:05AM +0200, Peter Zijlstra wrote: > Hi! > > Since you seem to care about kgdb, I figured you might want to fix this > before I mark it broken on x86 (we've been considering doing that for a > while). > > AFAICT the whole debugreg usage of kgdb-x86_64 is completely hosed; it > doesn't respsect the normal exclusion zones as per arch_build_bp_info(). > > That is, breakpoints must never be in: > > - in the cpu_entry_area > - in .entry.text > - in .noinstr.text > - in anything else marked NOKPROBE > > by not respecting these constraints it is trivial to completely and > utterly hose the machine. The entry rework that is current underway will > explicitly not deal with #DB triggering in any of those places.
This also very much includes single stepping those bits. Which KGDB obviously also does not respects.
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