EX.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the EX.H header at

d:\th\minkernel\ntos\inc

and draws from it the following type definitions:

Line Number	Type
36	struct _CALL_HASH_ENTRY
43	struct _CALL_PERFORMANCE_DATA
273	enum _PP_NPAGED_LOOKASIDE_NUMBER
510	enum _EXQUEUEINDEX
518	struct _EX_WORK_QUEUE
588	enum _EX_BALANCE_OBJECT
595	struct _ENODE
744	struct _HANDLE_TABLE_ENTRY_INFO
833	union _HANDLE_TABLE_ENTRY
969	struct _HANDLE_TRACE_DB_ENTRY
981	struct _HANDLE_TRACE_DEBUG_INFO
1051	struct _HANDLE_TABLE_FREE_LIST
1071	struct _HANDLE_TABLE
1948	struct _EX_FAST_REF
3365	enum _EX_GEN_RANDOM_DOMAIN

The header EX.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).