sandbox: Allow reading/writing of RAM buffer

It is useful to be able to save and restore the RAM contents of sandbox
U-Boot either for setting up tests, for later analysys, or for chaining
together multiple tests which need to keep the same memory contents.

Add a function to provide a memory file for U-Boot. This is read on
start-up and written when shutting down. If the file does not exist
on start-up, it will be created when shutting down.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

include/os.h

@@ -229,4 +229,20 @@ void os_putc(int ch);
  */
 void os_puts(const char *str);
 
+/**
+ * Write the sandbox RAM buffer to a existing file
+ *
+ * @param fname		Filename to write memory to (simple binary format)
+ * @return 0 if OK, -ve on error
+ */
+int os_write_ram_buf(const char *fname);
+
+/**
+ * Read the sandbox RAM buffer from an existing file
+ *
+ * @param fname		Filename containing memory (simple binary format)
+ * @return 0 if OK, -ve on error
+ */
+int os_read_ram_buf(const char *fname);
+
 #endif