[PATCH 4.9 145/153] powerpc/xmon: Fix data-breakpoint

From: Greg Kroah-Hartman
Date: Fri Mar 10 2017 - 04:26:41 EST

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


From: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx>

commit c21a493a2b44650707d06741601894329486f2ad upstream.

Currently xmon data-breakpoint feature is broken.

Whenever there is a watchpoint match occurs, hw_breakpoint_handler will
be called by do_break via notifier chains mechanism. If watchpoint is
registered by xmon, hw_breakpoint_handler won't find any associated
perf_event and returns immediately with NOTIFY_STOP. Similarly, do_break
also returns without notifying to xmon.

Solve this by returning NOTIFY_DONE when hw_breakpoint_handler does not
find any perf_event associated with matched watchpoint, rather than
NOTIFY_STOP, which tells the core code to continue calling the other
breakpoint handlers including the xmon one.

Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/powerpc/kernel/hw_breakpoint.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -228,8 +228,10 @@ int hw_breakpoint_handler(struct die_arg

bp = __this_cpu_read(bp_per_reg);
- if (!bp)
+ if (!bp) {
goto out;
+ }
info = counter_arch_bp(bp);