libfdt: Add support for disabling rollback handling

Allow enabling FDT_ASSUME_NO_ROLLBACK to disable rolling back after a
failed operation.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20200220214557.176528-6-sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/fdt_rw.c

@@ -114,6 +114,15 @@ static int fdt_splice_string_(void *fdt, int newlen)
 	return 0;
 }
 
+/**
+ * fdt_find_add_string_() - Find or allocate a string
+ *
+ * @fdt: pointer to the device tree to check/adjust
+ * @s: string to find/add
+ * @allocated: Set to 0 if the string was found, 1 if not found and so
+ *	allocated. Ignored if can_assume(NO_ROLLBACK)
+ * @return offset of string in the string table (whether found or added)
+ */
 static int fdt_find_add_string_(void *fdt, const char *s, int *allocated)
 {
 	char *strtab = (char *)fdt + fdt_off_dt_strings(fdt);
@@ -122,7 +131,8 @@ static int fdt_find_add_string_(void *fdt, const char *s, int *allocated)
 	int len = strlen(s) + 1;
 	int err;
 
-	*allocated = 0;
+	if (!can_assume(NO_ROLLBACK))
+		*allocated = 0;
 
 	p = fdt_find_string_(strtab, fdt_size_dt_strings(fdt), s);
 	if (p)
@@ -134,7 +144,8 @@ static int fdt_find_add_string_(void *fdt, const char *s, int *allocated)
 	if (err)
 		return err;
 
-	*allocated = 1;
+	if (!can_assume(NO_ROLLBACK))
+		*allocated = 1;
 
 	memcpy(new, s, len);
 	return (new - strtab);
@@ -208,7 +219,8 @@ static int fdt_add_property_(void *fdt, int nodeoffset, const char *name,
 
 	err = fdt_splice_struct_(fdt, *prop, 0, proplen);
 	if (err) {
-		if (allocated)
+		/* Delete the string if we failed to add it */
+		if (!can_assume(NO_ROLLBACK) && allocated)
 			fdt_del_last_string_(fdt, name);
 		return err;
 	}