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From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Ingo Molnar <mingo@redhat.com>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>, peterz@infradead.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andrea Righi <righi.andrea@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH v2 8/9] kprobes: Prohibit probing on RCU debug routine
Date:   Sat, 12 Jan 2019 11:29:27 +0900
Message-Id: <154726016731.18060.5873805314873726998.stgit@devbox>
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Since kprobe itself depends on RCU, probing on RCU debug
routine can cause recursive breakpoint problem.
Prohibit probing on RCU debug routines.

int3
 ->do_int3()
   ->ist_enter()
     ->RCU_LOCKDEP_WARN()
       ->debug_lockdep_rcu_enabled() -> int3

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/rcu/update.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 1971869c4072..f4ca36d92138 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -52,6 +52,7 @@
 #include <linux/tick.h>
 #include <linux/rcupdate_wait.h>
 #include <linux/sched/isolation.h>
+#include <linux/kprobes.h>
 
 #define CREATE_TRACE_POINTS
 
@@ -249,6 +250,7 @@ int notrace debug_lockdep_rcu_enabled(void)
 	       current->lockdep_recursion == 0;
 }
 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
+NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled);
 
 /**
  * rcu_read_lock_held() - might we be in RCU read-side critical section?