Commit 3ee9033e authored Jun 01, 2017 by Naveen N. Rao Committed by Greg Kroah-Hartman Jun 29, 2017

powerpc/kprobes: Pause function_graph tracing during jprobes handling

commit a9f8553e935f26cb5447f67e280946b0923cd2dc upstream.

This fixes a crash when function_graph and jprobes are used together.
This is essentially commit 237d28db ("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: 6794c782 ("powerpc64: port of the function graph tracer")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bc7b3e99

arch/powerpc/kernel/kprobes.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -514,6 +514,15 @@ int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
		#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(struct kprobe p, struct pt_regs regs)
		* 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;
		}