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[PATCH 3.18 07/16] powerpc/kprobes: Pause function_graph tracing during jprobes handling

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3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

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@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>

---
 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;
 }

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[PATCH 3.18 00/16] 3.18.59-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 02/16] autofs: sanity check status reported with AUTOFS_DEV_IOCTL_FAIL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 09/16] target: Fix kref->refcount underflow in transport_cmd_finish_abort Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 03/16] lib/cmdline.c: fix get_options() overflow while parsing ranges Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 06/16] signal: Only reschedule timers on signals timers have sent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 14/16] usb: gadget: f_fs: avoid out of bounds access on comp_desc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:00 +0200
  [PATCH 3.18 13/16] powerpc/slb: Force a full SLB flush when we insert for a bad EA Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  [PATCH 3.18 11/16] of: Add check to of_scan_flat_dt() before accessing initial_boot_params Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  [PATCH 3.18 04/16] KVM: PPC: Book3S HV: Preserve userspace HTM state properly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  [PATCH 3.18 07/16] powerpc/kprobes: Pause function_graph tracing during jprobes handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  [PATCH 3.18 15/16] net: phy: fix marvell phy status reading Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  [PATCH 3.18 05/16] CIFS: Improve readdir verbosity Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-27 15:10 +0200
  Re: [PATCH 3.18 00/16] 3.18.59-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-27 21:00 +0200
  Re: [PATCH 3.18 00/16] 3.18.59-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-28 16:00 +0200

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