ntoskrnl: Add ExGetPreviousMode and test.

dlls/ntoskrnl.exe/ntoskrnl.c

@@ -4566,6 +4566,12 @@ NTSTATUS WINAPI KdEnableDebugger(void)
     return STATUS_DEBUGGER_INACTIVE;
 }
 
+KPROCESSOR_MODE WINAPI ExGetPreviousMode(void)
+{
+    TRACE("\n");
+    return PsIsSystemThread((PETHREAD)KeGetCurrentThread()) ? KernelMode : UserMode;
+}
+
 #ifdef __x86_64__
 
 void WINAPI KfRaiseIrql(KIRQL new, KIRQL *old)

dlls/ntoskrnl.exe/ntoskrnl.exe.spec

@@ -154,7 +154,7 @@
 @ stub ExGetCurrentProcessorCounts
 @ stub ExGetCurrentProcessorCpuUsage
 @ stdcall ExGetExclusiveWaiterCount(ptr)
-@ stub ExGetPreviousMode
+@ stdcall ExGetPreviousMode()
 @ stdcall ExGetSharedWaiterCount(ptr)
 @ stdcall ExInitializeNPagedLookasideList(ptr ptr ptr long long long long)
 @ stdcall ExInitializePagedLookasideList(ptr ptr ptr long long long long)

dlls/ntoskrnl.exe/tests/driver.c

@@ -454,6 +454,7 @@ static void test_current_thread(BOOL is_system)
 
     ok(PsGetThreadId((PETHREAD)KeGetCurrentThread()) == PsGetCurrentThreadId(), "thread IDs don't match\n");
     ok(PsIsSystemThread((PETHREAD)KeGetCurrentThread()) == is_system, "unexpected system thread\n");
+    ok(ExGetPreviousMode() == is_system ? KernelMode : UserMode, "previous mode is not correct\n");
     if (!is_system)
     {
         ok(create_caller_thread == KeGetCurrentThread(), "thread is not create caller thread\n");

include/ddk/wdm.h

@@ -1683,6 +1683,7 @@ void      WINAPI ExDeleteNPagedLookasideList(PNPAGED_LOOKASIDE_LIST);
 void      WINAPI ExDeletePagedLookasideList(PPAGED_LOOKASIDE_LIST);
 NTSTATUS  WINAPI ExDeleteResourceLite(ERESOURCE*);
 ULONG     WINAPI ExGetExclusiveWaiterCount(ERESOURCE*);
+KPROCESSOR_MODE WINAPI ExGetPreviousMode(void);
 ULONG     WINAPI ExGetSharedWaiterCount(ERESOURCE*);
 void      WINAPI ExInitializeNPagedLookasideList(PNPAGED_LOOKASIDE_LIST,PALLOCATE_FUNCTION,PFREE_FUNCTION,ULONG,SIZE_T,ULONG,USHORT);
 void      WINAPI ExInitializePagedLookasideList(PPAGED_LOOKASIDE_LIST,PALLOCATE_FUNCTION,PFREE_FUNCTION,ULONG,SIZE_T,ULONG,USHORT);