[SPARC64]: Fix MD property lifetime bugs.
Property values cannot be referenced outside of
mdesc_grab()/mdesc_release() pairs. The only major
offender was the VIO bus layer, easily fixed.
Add some commentary to mdesc.h describing these rules.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/asm-sparc64/mdesc.h b/include/asm-sparc64/mdesc.h
index bbb0c0b..dc372df 100644
--- a/include/asm-sparc64/mdesc.h
+++ b/include/asm-sparc64/mdesc.h
@@ -23,8 +23,28 @@
(__node) != MDESC_NODE_NULL; \
__node = mdesc_node_by_name(__hdl, __node, __name))
+/* Access to property values returned from mdesc_get_property() are
+ * only valid inside of a mdesc_grab()/mdesc_release() sequence.
+ * Once mdesc_release() is called, the memory backed up by these
+ * pointers may reference freed up memory.
+ *
+ * Therefore callers must make copies of any property values
+ * they need.
+ *
+ * These same rules apply to mdesc_node_name().
+ */
extern const void *mdesc_get_property(struct mdesc_handle *handle,
u64 node, const char *name, int *lenp);
+extern const char *mdesc_node_name(struct mdesc_handle *hp, u64 node);
+
+/* MD arc iteration, the standard sequence is:
+ *
+ * unsigned long arc;
+ * mdesc_for_each_arc(arc, handle, node, MDESC_ARC_TYPE_{FWD,BACK}) {
+ * unsigned long target = mdesc_arc_target(handle, arc);
+ * ...
+ * }
+ */
#define MDESC_ARC_TYPE_FWD "fwd"
#define MDESC_ARC_TYPE_BACK "back"
@@ -38,8 +58,6 @@
extern u64 mdesc_arc_target(struct mdesc_handle *hp, u64 arc);
-extern const char *mdesc_node_name(struct mdesc_handle *hp, u64 node);
-
extern void mdesc_update(void);
extern void sun4v_mdesc_init(void);