|Priority:||4 - Normal|
|Created by:||Former user|
|Reported by:||Former user|
|Assigned to:||Former user|
Fixed: A fix for this issue is checked into the tree and tested.
(Resolution Date: 2018-01-23T19:51:30.308Z)
KMDB has vestigial support for two features, ::step branch and ::branches. The former allows you to step to the next branch point, while the latter reports the "last few" branches, as recorded in MSRs such as the LBR.
However, this was never properly implemented for 64-bit, thus is effectively non-existent on any reasonably modern system. While it could be resurrected, fixing this would complicate KPTI implementation. As it's already broken, it's hard to argue that it will be missed; we'll just remove all the relevant code.
Side note: if we ever decide to reimplement this, it can likely be in greatly simplified form, as the CPU support long since solidified.
Tested this with debug and non-debug, from bootloaded and modloaded KMDB, along with a bunch of step/bpt testing.
OS-6565 remove KMDB branch debugging support
OS-6566 ::crregs could do with cr2/cr3 support
OS-6567 ::ttrace should be able to filter by thread
Reviewed by: Patrick Mooney <email@example.com>
Approved by: Patrick Mooney <firstname.lastname@example.org>