livepatch: add (un)patch callbacks

Provide livepatch modules a klp_object (un)patching notification
mechanism.  Pre and post-(un)patch callbacks allow livepatch modules to
setup or synchronize changes that would be difficult to support in only
patched-or-unpatched code contexts.

Callbacks can be registered for target module or vmlinux klp_objects,
but each implementation is klp_object specific.

  - Pre-(un)patch callbacks run before any (un)patching transition
    starts.

  - Post-(un)patch callbacks run once an object has been (un)patched and
    the klp_patch fully transitioned to its target state.

Example use cases include modification of global data and registration
of newly available services/handlers.

See Documentation/livepatch/callbacks.txt for details and
samples/livepatch/ for examples.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 38 insertions, 0 deletions

diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index c74f24c47837..6fc907b54e71 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -1,6 +1,44 @@
 #ifndef _LIVEPATCH_CORE_H
 #define _LIVEPATCH_CORE_H
 
+#include <linux/livepatch.h>
+
 extern struct mutex klp_mutex;
 
+static inline bool klp_is_object_loaded(struct klp_object *obj)
+{
+	return !obj->name || obj->mod;
+}
+
+static inline int klp_pre_patch_callback(struct klp_object *obj)
+{
+	int ret;
+
+	ret = (obj->callbacks.pre_patch) ?
+		(*obj->callbacks.pre_patch)(obj) : 0;
+
+	obj->callbacks.post_unpatch_enabled = !ret;
+
+	return ret;
+}
+
+static inline void klp_post_patch_callback(struct klp_object *obj)
+{
+	if (obj->callbacks.post_patch)
+		(*obj->callbacks.post_patch)(obj);
+}
+
+static inline void klp_pre_unpatch_callback(struct klp_object *obj)
+{
+	if (obj->callbacks.pre_unpatch)
+		(*obj->callbacks.pre_unpatch)(obj);
+}
+
+static inline void klp_post_unpatch_callback(struct klp_object *obj)
+{
+	if (obj->callbacks.post_unpatch_enabled &&
+	    obj->callbacks.post_unpatch)
+		(*obj->callbacks.post_unpatch)(obj);
+}
+
 #endif /* _LIVEPATCH_CORE_H */