sandbox: Add a function to read a host file

Add a way to read a file from the host filesystem. This can be useful for
reading test data, for example. Also fix up the writing function which was
not the right version, and drop the debugging lines.

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

include/os.h

@@ -350,4 +350,18 @@ int os_mprotect_allow(void *start, size_t len);
  */
 int os_write_file(const char *name, const void *buf, int size);
 
+/**
+ * os_read_file() - Read a file from the host filesystem
+ *
+ * This can be useful when reading test data into sandbox for use by test
+ * routines. The data is allocated using os_malloc() and should be freed by
+ * the caller.
+ *
+ * @name:	File path to read from
+ * @bufp:	Returns buffer containing data read
+ * @sizep:	Returns size of data
+ * @return 0 if OK, -ve on error
+ */
+int os_read_file(const char *name, void **bufp, int *sizep);
+
 #endif