[umalloc] Formalise the user memory allocation API

src/include/gpxe/umalloc.h

@@ -8,10 +8,58 @@
  *
  */
 
+#include <gpxe/api.h>
+#include <config/umalloc.h>
 #include <gpxe/uaccess.h>
 
-extern userptr_t umalloc ( size_t size );
-extern userptr_t urealloc ( userptr_t ptr, size_t new_size );
-extern void ufree ( userptr_t ptr );
+/**
+ * Provide a user memory allocation API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_UMALLOC( _subsys, _api_func, _func ) \
+	PROVIDE_SINGLE_API ( UMALLOC_PREFIX_ ## _subsys, _api_func, _func )
+
+/* Include all architecture-independent I/O API headers */
+
+/* Include all architecture-dependent I/O API headers */
+#include <bits/umalloc.h>
+
+/**
+ * Reallocate external memory
+ *
+ * @v userptr		Memory previously allocated by umalloc(), or UNULL
+ * @v new_size		Requested size
+ * @ret userptr		Allocated memory, or UNULL
+ *
+ * Calling realloc() with a new size of zero is a valid way to free a
+ * memory block.
+ */
+userptr_t urealloc ( userptr_t userptr, size_t new_size );
+
+/**
+ * Allocate external memory
+ *
+ * @v size		Requested size
+ * @ret userptr		Memory, or UNULL
+ *
+ * Memory is guaranteed to be aligned to a page boundary.
+ */
+static inline __always_inline userptr_t umalloc ( size_t size ) {
+	return urealloc ( UNULL, size );
+}
+
+/**
+ * Free external memory
+ *
+ * @v userptr		Memory allocated by umalloc(), or UNULL
+ *
+ * If @c ptr is UNULL, no action is taken.
+ */
+static inline __always_inline void ufree ( userptr_t userptr ) {
+	urealloc ( userptr, 0 );
+}
 
 #endif /* _GPXE_UMALLOC_H */