* grub-core/kern/misc.c (grub_vsnprintf_real): Handle %% properly.

* tests/printf_unit_test.c (printf_test): Add %% tests.
	Reported by: Paulo Flabiano Smorigo.

grub-core/kern/misc.c

@@ -910,6 +910,12 @@ grub_vsnprintf_real (char *str, grub_size_t max_len, const char *fmt0, va_list a
 	    }
 	}
 
+      if (c == '%')
+	{
+	  write_char (c);
+	  continue;
+	}
+
       if (curn >= count_args)
 	continue;