Increase DATA_LIMIT to 64 KiB

WHCP System.Fundamentals.Firmware.UEFISecureBoot point 30 dictates:

Reserved Memory for Windows Secure Boot UEFI Variables. A total of at
least 128 KB of non-volatile NVRAM storage memory must be available for
NV UEFI variables (authenticated and unauthenticated, BS and RT) used by
UEFI Secure Boot and Windows, and the maximum supported variable size
must be at least 64 KB. There is no maximum NVRAM storage limit. Note
that this is an increase from Windows 10, version 1703 requirements of
64 KB total and 32 KB variable size. This requirement will become
enforced in the next release cycle, after April 2018.

Signed-off-by: Tu Dinh <[email protected]>

Author: dinhngtu

include/handler.h

@@ -35,7 +35,8 @@
 #include "efi.h"
 
 #define NAME_LIMIT 4096 /* Maximum length of name */
-#define DATA_LIMIT 57344 /* Maximum length of a single variable */
+/* The following limits must respect the minimum prescribed by WHCP. */
+#define DATA_LIMIT 65536 /* Maximum length of a single variable */
 #define TOTAL_LIMIT 131072 /* Maximum total storage */
 
 /*