[NTOS:KD64,KE] IRQL is automatically adjusted during calls to KdEnterDebugger() and KdExitDebugger(). (#3942)

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().

ntoskrnl/kd64/kdapi.c

@@ -1890,7 +1890,7 @@ KdEnterDebugger(IN PKTRAP_FRAME TrapFrame,
     /* Save the current IRQL */
     KeGetCurrentPrcb()->DebuggerSavedIRQL = KeGetCurrentIrql();
 
-    /* Freeze all CPUs */
+    /* Freeze all CPUs, raising also the IRQL to HIGH_LEVEL */
     Enable = KeFreezeExecution(TrapFrame, ExceptionFrame);
 
     /* Lock the port, save the state and set debugger entered */
@@ -1929,7 +1929,7 @@ KdExitDebugger(IN BOOLEAN Enable)
     KdRestore(FALSE);
     if (KdpPortLocked) KdpPortUnlock();
 
-    /* Unfreeze the CPUs */
+    /* Unfreeze the CPUs, restoring also the IRQL */
     KeThawExecution(Enable);
 
     /* Compare time with the one from KdEnterDebugger */

ntoskrnl/kd64/kdtrap.c

@@ -144,11 +144,6 @@ KdpTrap(IN PKTRAP_FRAME TrapFrame,
     BOOLEAN Handled;
     NTSTATUS ReturnStatus;
     USHORT ReturnLength;
-    KIRQL OldIrql = DISPATCH_LEVEL;
-
-    /* Raise if we have to. */
-    if (KeGetCurrentIrql() < DISPATCH_LEVEL)
-        OldIrql = KeRaiseIrqlToDpcLevel();
 
     /*
      * Check if we got a STATUS_BREAKPOINT with a SubID for Print, Prompt or
@@ -262,9 +257,6 @@ KdpTrap(IN PKTRAP_FRAME TrapFrame,
                             SecondChanceException);
     }
 
-    if (OldIrql < DISPATCH_LEVEL)
-        KeLowerIrql(OldIrql);
-
     /* Return TRUE or FALSE to caller */
     return Handled;
 }

ntoskrnl/ke/freeze.c

@@ -27,15 +27,33 @@ KeFreezeExecution(IN PKTRAP_FRAME TrapFrame,
                   IN PKEXCEPTION_FRAME ExceptionFrame)
 {
     BOOLEAN Enable;
+    KIRQL OldIrql;
 
-    /* Disable interrupts and get previous state */
+#ifndef CONFIG_SMP
+    UNREFERENCED_PARAMETER(TrapFrame);
+    UNREFERENCED_PARAMETER(ExceptionFrame);
+#endif
+
+    /* Disable interrupts, get previous state and set the freeze flag */
     Enable = KeDisableInterrupts();
-
-    /* Save freeze flag */
     KiFreezeFlag = 4;
 
-    /* Save the old IRQL */
+#ifndef CONFIG_SMP
-    KiOldIrql = KeGetCurrentIrql();
+    /* Raise IRQL if we have to */
+    OldIrql = KeGetCurrentIrql();
+    if (OldIrql < DISPATCH_LEVEL)
+        OldIrql = KeRaiseIrqlToDpcLevel();
+#else
+    /* Raise IRQL to HIGH_LEVEL */
+    KeRaiseIrql(HIGH_LEVEL, &OldIrql);
+#endif
+
+#ifdef CONFIG_SMP
+    // TODO: Add SMP support.
+#endif
+
+    /* Save the old IRQL to be restored on unfreeze */
+    KiOldIrql = OldIrql;
 
     /* Return whether interrupts were enabled */
     return Enable;
@@ -45,9 +63,22 @@ VOID
 NTAPI
 KeThawExecution(IN BOOLEAN Enable)
 {
+#ifdef CONFIG_SMP
+    // TODO: Add SMP support.
+#endif
+
+    /* Clear the freeze flag */
+    KiFreezeFlag = 0;
+
     /* Cleanup CPU caches */
     KeFlushCurrentTb();
 
+    /* Restore the old IRQL */
+#ifndef CONFIG_SMP
+    if (KiOldIrql < DISPATCH_LEVEL)
+#endif
+    KeLowerIrql(KiOldIrql);
+
     /* Re-enable interrupts */
-    if (Enable) _enable();
+    KeRestoreInterrupts(Enable);
 }