tracing/kprobes: Dump the culprit kprobe in case of kprobe recursion

Kprobes can enter into a probing recursion, ie: a kprobe that does an
endless loop because one of its core mechanism function used during
probing is also probed itself.

This patch helps pinpointing the kprobe that raised such recursion
by dumping it and raising a BUG instead of a warning (we also disarm
the kprobe to try avoiding recursion in BUG itself). Having a BUG
instead of a warning stops the stacktrace in the right place and
doesn't pollute the logs with hundreds of traces that eventually end
up in a stack overflow.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ef177d653b2c..f72e96c25a38 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1141,6 +1141,13 @@ static void __kprobes kill_kprobe(struct kprobe *p)
         arch_remove_kprobe(p);
 }
 
+void __kprobes dump_kprobe(struct kprobe *kp)
+{
+        printk(KERN_WARNING "Dumping kprobe:\n");
+        printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n",
+               kp->symbol_name, kp->addr, kp->offset);
+}
+
 /* Module notifier call back, checking kprobes on the module */
 static int __kprobes kprobes_module_callback(struct notifier_block *nb,
                                              unsigned long val, void *data)