target/armv7m,cortex_m: introduce checked arch_info cast routines

[fw/openocd] / src / target / armv7m.h

diff --git a/src/target/armv7m.h b/src/target/armv7m.h
index d33e574928b6e071c18df1645965210b0ed41f1f..9ac121ac316be0a058132b6252bb658c91c4281d 100644 (file)
--- a/src/target/armv7m.h
+++ b/src/target/armv7m.h
@@ -255,15 +255,48 @@ struct armv7m_common {
        void (*pre_restore_context)(struct target *target);
 };
 
+static inline bool is_armv7m(const struct armv7m_common *armv7m)
+{
+       return armv7m->common_magic == ARMV7M_COMMON_MAGIC;
+}
+
+/**
+ * @returns the pointer to the target specific struct
+ * without matching a magic number.
+ * Use in target specific service routines, where the correct
+ * type of arch_info is certain.
+ */
 static inline struct armv7m_common *
 target_to_armv7m(struct target *target)
 {
        return container_of(target->arch_info, struct armv7m_common, arm);
 }
 
-static inline bool is_armv7m(const struct armv7m_common *armv7m)
+/**
+ * @returns the pointer to the target specific struct
+ * or NULL if the magic number does not match.
+ * Use in a flash driver or any place where mismatch of the arch_info
+ * type can happen.
+ */
+static inline struct armv7m_common *
+target_to_armv7m_safe(struct target *target)
 {
-       return armv7m->common_magic == ARMV7M_COMMON_MAGIC;
+       if (!target)
+               return NULL;
+
+       if (!target->arch_info)
+               return NULL;
+
+       /* Check the parent type first to prevent peeking memory too far
+        * from arch_info pointer */
+       if (!is_arm(target_to_arm(target)))
+               return NULL;
+
+       struct armv7m_common *armv7m = target_to_armv7m(target);
+       if (!is_armv7m(armv7m))
+               return NULL;
+
+       return armv7m;
 }
 
 struct armv7m_algorithm {