Addendum to 608032bd and 835c3023.
The IRQL is actually raised by KeFreezeExecution() and lowered by
KeThawExecution(), always to HIGH_IRQL on MP systems, or if necessary
on UP. These functions are called respectively by KdEnterDebugger()
and KdExitDebugger().
KD64: Raise to HIGH_LEVEL when entering trap
KDBG: lower to DISPATCH_LEVEL when applying IRQL hack & use a worker thread to load symbols
KD&KDBG: Actually unload symbols when required
Raise IRQL before entering debugger, so that KeAcquireSpinLockAtDpcLevel works as expected.
- HIGH_LEVEL since we don't know where we are coming from.
Do not try to read debug symbol from files in KDBG.
- There is no reason that this works if Mm didn't map it in the first place.
