[NTOS:EX] Improve NtSystemDebugControl

- Add SEH probing for user buffer
- Mark some classes as i386 only
- Explicitly return STATUS_NOT_IMPLEMENTED on disabled classes (must use KdSystemDebugControl instead)
- Explicitly return STATUS_NOT_IMPLEMENTED on not implemented classes
- Return STATUS_INVALID_INFO_CLASS on all other classes

ntoskrnl/ex/dbgctrl.c

@@ -214,14 +214,40 @@ NtSystemDebugControl(
     _In_ ULONG OutputBufferLength,
     _Out_opt_ PULONG ReturnLength)
 {
+    KPROCESSOR_MODE PreviousMode = KeGetPreviousMode();
+    ULONG Length = 0;
+    NTSTATUS Status;
+
+    _SEH2_TRY
+    {
+        if (PreviousMode != KernelMode)
+        {
+            if (InputBufferLength)
+                ProbeForRead(InputBuffer, InputBufferLength, sizeof(ULONG));
+            if (OutputBufferLength)
+                ProbeForWrite(OutputBuffer, OutputBufferLength, sizeof(ULONG));
+            if (ReturnLength)
+                ProbeForWriteUlong(ReturnLength);
+        }
+
         switch (Command)
         {
             case SysDbgQueryModuleInformation:
+                /* Removed in WinNT4 */
+                Status = STATUS_INVALID_INFO_CLASS;
+                break;
+
+#ifdef _M_IX86
             case SysDbgQueryTraceInformation:
             case SysDbgSetTracepoint:
             case SysDbgSetSpecialCall:
             case SysDbgClearSpecialCalls:
             case SysDbgQuerySpecialCalls:
+                UNIMPLEMENTED;
+                Status = STATUS_NOT_IMPLEMENTED;
+                break;
+#endif
+
             case SysDbgQueryVersion:
             case SysDbgReadVirtual:
             case SysDbgWriteVirtual:
@@ -236,8 +262,10 @@ NtSystemDebugControl(
             case SysDbgReadBusData:
             case SysDbgWriteBusData:
             case SysDbgCheckLowMemory:
-        case SysDbgGetTriageDump:
+                /* Those are implemented in KdSystemDebugControl */
-            return STATUS_NOT_IMPLEMENTED;
+                Status = STATUS_NOT_IMPLEMENTED;
+                break;
+
             case SysDbgBreakPoint:
             case SysDbgEnableKernelDebugger:
             case SysDbgDisableKernelDebugger:
@@ -247,15 +275,26 @@ NtSystemDebugControl(
             case SysDbgSetPrintBufferSize:
             case SysDbgGetKdUmExceptionEnable:
             case SysDbgSetKdUmExceptionEnable:
-
+            case SysDbgGetTriageDump:
             case SysDbgGetKdBlockEnable:
             case SysDbgSetKdBlockEnable:
-            return KdSystemDebugControl(
+                UNIMPLEMENTED;
-                Command,
+                Status = STATUS_NOT_IMPLEMENTED;
-                InputBuffer, InputBufferLength,
+                break;
-                OutputBuffer, OutputBufferLength,
+
-                ReturnLength, KeGetPreviousMode());
             default:
-            return STATUS_INVALID_INFO_CLASS;
+                Status = STATUS_INVALID_INFO_CLASS;
+                break;
         }
+
+        if (ReturnLength)
+            *ReturnLength = Length;
+
+        _SEH2_YIELD(return Status);
+    }
+    _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
+    {
+        _SEH2_YIELD(return _SEH2_GetExceptionCode());
+    }
+    _SEH2_END;
 }