kprobes: support probing module __exit function

Allows kprobes to probe __exit routine.  This adds flags member to struct
kprobe.  When module is freed(kprobes hooks module_notifier to get this
event), kprobes which probe the functions in that module are set to "Gone"
flag to the flags member.  These "Gone" probes are never be enabled.
Users can check the GONE flag through debugfs.

This also removes mod_refcounted, because we couldn't free a module if
kprobe incremented the refcount of that module.

[akpm@linux-foundation.org: document some locking]
[mhiramat@redhat.com: bugfix: pass aggr_kprobe to arch_remove_kprobe]
[mhiramat@redhat.com: bugfix: release old_p's insn_slot before error return]
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index b93e44ce2284..d6ea19e314bb 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -69,9 +69,6 @@ struct kprobe {
         /* list of kprobes for multi-handler support */
         struct list_head list;
 
-        /* Indicates that the corresponding module has been ref counted */
-        unsigned int mod_refcounted;
-
         /*count the number of times this probe was temporarily disarmed */
         unsigned long nmissed;
 
@@ -103,8 +100,19 @@ struct kprobe {
 
         /* copy of the original instruction */
         struct arch_specific_insn ainsn;
+
+        /* Indicates various status flags.  Protected by kprobe_mutex. */
+        u32 flags;
 };
 
+/* Kprobe status flags */
+#define KPROBE_FLAG_GONE        1 /* breakpoint has already gone */
+
+static inline int kprobe_gone(struct kprobe *p)
+{
+        return p->flags & KPROBE_FLAG_GONE;
+}
+
 /*
  * Special probe type that uses setjmp-longjmp type tricks to resume
  * execution at a specified entry with a matching prototype corresponding