debugobjects: insulate non-fixup logic related to static obj from fixup callbacks

When activating a static object we need make sure that the object is
tracked in the object tracker.  If it is a non-static object then the
activation is illegal.

In previous implementation, each subsystem need take care of this in
their fixup callbacks.  Actually we can put it into debugobjects core.
Thus we can save duplicated code, and have *pure* fixup callbacks.

To achieve this, a new callback "is_static_object" is introduced to let
the type specific code decide whether a object is static or not.  If
yes, we take it into object tracker, otherwise give warning and invoke
fixup callback.

This change has paassed debugobjects selftest, and I also do some test
with all debugobjects supports enabled.

At last, I have a concern about the fixups that can it change the object
which is in incorrect state on fixup? Because the 'addr' may not point
to any valid object if a non-static object is not tracked.  Then Change
such object can overwrite someone's memory and cause unexpected
behaviour.  For example, the timer_fixup_activate bind timer to function
stub_timer.

Link: http://lkml.kernel.org/r/1462576157-14539-1-git-send-email-changbin.du@intel.com
[changbin.du@intel.com: improve code comments where invoke the new is_static_object callback]
  Link: http://lkml.kernel.org/r/1462777431-8171-1-git-send-email-changbin.du@intel.com
Signed-off-by: Du, Changbin <changbin.du@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h
index a899f10c9365..46056cb161fc 100644
--- a/include/linux/debugobjects.h
+++ b/include/linux/debugobjects.h
@@ -38,6 +38,7 @@ struct debug_obj {
  * @name:               name of the object typee
  * @debug_hint:         function returning address, which have associated
  *                      kernel symbol, to allow identify the object
+ * @is_static_object    return true if the obj is static, otherwise return false
  * @fixup_init:         fixup function, which is called when the init check
  *                      fails. All fixup functions must return true if fixup
  *                      was successful, otherwise return false
@@ -53,6 +54,7 @@ struct debug_obj {
 struct debug_obj_descr {
         const char              *name;
         void *(*debug_hint)(void *addr);
+        bool (*is_static_object)(void *addr);
         bool (*fixup_init)(void *addr, enum debug_obj_state state);
         bool (*fixup_activate)(void *addr, enum debug_obj_state state);
         bool (*fixup_destroy)(void *addr, enum debug_obj_state state);