Fix valgrind errors in sw_tree1

The sw_tree1 testcase has accumulated some valgrind errors, at least in
the "realloc" mode.
  * It had both a realloc_fdt() and explicit xmalloc() for the initial
allocation which was redundant and caused errors.
  * It doesn't make sense to call fdt_resize() until after we've created
the initial stub tree
  * Alignment gaps inserted into the tree contain uninitialized data, which
trips an error when we write it out.  We could zero the buffer, but that
would make it easier to miss real bugs, so we add suppressions for the
valgrind warnings instead.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/tests/sw_tree1.c b/tests/sw_tree1.c
index de00707..6d4c531 100644
--- a/tests/sw_tree1.c
+++ b/tests/sw_tree1.c
@@ -37,7 +37,7 @@
 	REALLOC,
 } alloc_mode;
 
-static void realloc_fdt(void **fdt, size_t *size)
+static void realloc_fdt(void **fdt, size_t *size, bool created)
 {
 	switch (alloc_mode) {
 	case FIXED:
@@ -61,7 +61,8 @@
 	case REALLOC:
 		*size += 1;
 		*fdt = xrealloc(*fdt, *size);
-		fdt_resize(*fdt, *fdt, *size);
+		if (created)
+			fdt_resize(*fdt, *fdt, *size);
 		return;
 
 	default:
@@ -73,7 +74,7 @@
 	do {			      \
 		err = (code);			     \
 		if (err == -FDT_ERR_NOSPACE)			\
-			realloc_fdt(&fdt, &size);			\
+			realloc_fdt(&fdt, &size, created);		\
 		else if (err)						\
 			FAIL(#code ": %s", fdt_strerror(err));		\
 	} while (err != 0)
@@ -83,6 +84,7 @@
 	void *fdt = NULL;
 	size_t size;
 	int err;
+	bool created = false;
 
 	test_init(argc, argv);
 
@@ -108,12 +110,13 @@
 		}
 	}
 
-	realloc_fdt(&fdt, &size);
-	
 	fdt = xmalloc(size);
 	CHECK(fdt_create(fdt, size));
 
+	created = true;
+
 	CHECK(fdt_add_reservemap_entry(fdt, TEST_ADDR_1, TEST_SIZE_1));
+
 	CHECK(fdt_add_reservemap_entry(fdt, TEST_ADDR_2, TEST_SIZE_2));
 	CHECK(fdt_finish_reservemap(fdt));
 
diff --git a/tests/sw_tree1.supp b/tests/sw_tree1.supp
new file mode 100644
index 0000000..279f9e5
--- /dev/null
+++ b/tests/sw_tree1.supp
@@ -0,0 +1,18 @@
+{
+   allocation methods causes uninitialized data in alignment gap
+   Memcheck:Param
+   write(buf)
+   fun:__write_nocancel
+   fun:utilfdt_write_err
+   fun:save_blob
+   fun:main
+}
+{
+   allocation methods causes uninitialized data in alignment gap
+   Memcheck:Param
+   write(buf)
+   fun:__write_nocancel
+   fun:utilfdt_write_err
+   fun:save_blob
+   fun:main
+}