Outline user<->secure page copying.

exosphere/userpage.h

@@ -0,0 +1,22 @@
+#ifndef EXOSPHERE_USERPAGE_H
+#define EXOSPHERE_USERPAGE_H
+
+#include <stdint.h>
+
+#define SECURE_USER_PAGE_ADDR (0x1F01F4000ULL)
+
+typedef struct {
+    uint64_t user_page;
+    uint64_t secure_page;
+} upage_ref_t;
+
+int upage_init(upage_ref_t *user_page, void *user_address);
+
+void user_copy_to_secure(upage_ref_t *user_page, void *secure_dst, void *user_src, size_t size);
+void secure_copy_to_user(upage_ref_t *user_page, void *user_dst, void *secure_src, size_t size);
+
+static inline uint64_t get_page_for_address(void *address) {
+    return ((uint64_t)(address)) & 0xFFFFFFFFFFFFF000ULL;
+}
+
+#endif