This is a note to let you know that I've just added the patch titled
powerpc/kprobes: Pause function_graph tracing during jprobes handling
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-kprobes-pause-function_graph-tracing-during-jprobes-handling.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a9f8553e935f26cb5447f67e280946b0923cd2dc Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Date: Thu, 1 Jun 2017 16:18:15 +0530
Subject: powerpc/kprobes: Pause function_graph tracing during jprobes handling
From: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
commit a9f8553e935f26cb5447f67e280946b0923cd2dc upstream.
This fixes a crash when function_graph and jprobes are used together.
This is essentially commit 237d28db036e ("ftrace/jprobes/x86: Fix
conflict between jprobes and function graph tracing"), but for powerpc.
Jprobes breaks function_graph tracing since the jprobe hook needs to use
jprobe_return(), which never returns back to the hook, but instead to
the original jprobe'd function. The solution is to momentarily pause
function_graph tracing before invoking the jprobe hook and re-enable it
when returning back to the original jprobe'd function.
Fixes: 6794c78243bf ("powerpc64: port of the function graph tracer")
Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/kprobes.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -514,6 +514,15 @@ int __kprobes setjmp_pre_handler(struct
#endif
#endif
+ /*
+ * jprobes use jprobe_return() which skips the normal return
+ * path of the function, and this messes up the accounting of the
+ * function graph tracer.
+ *
+ * Pause function graph tracing while performing the jprobe function.
+ */
+ pause_graph_tracing();
+
return 1;
}
@@ -536,6 +545,8 @@ int __kprobes longjmp_break_handler(stru
* saved regs...
*/
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
+ /* It's OK to start function graph tracing again */
+ unpause_graph_tracing();
preempt_enable_no_resched();
return 1;
}
Patches currently in stable-queue which might be from naveen.n.rao@xxxxxxxxxxxxxxxxxx are
queue-3.18/powerpc-kprobes-pause-function_graph-tracing-during-jprobes-handling.patch