[PATCH 2/2] tracing: wprobe: Make wprobe_handler default overflow_handler compatible

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

To fix arm64 repeating watchpoint exception on the same instruction
bug, markthe wprobe handler as compatible with the default overflow
handler.

Since do_watchpoint() on arm64 does not configure the single step
execution correctly if the overflow_handler is not compatible with
default perf overflow handlers, custom handler will loop on the
same instruction by repeating watchpoint exception. But if the
overflow handler is compatible with the default handlers, it
configures the single step. So set the compatible flag since
wprobe_handler will not care arch-dependent case.

Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/aPvwGhMBJqMKcC9D@finisterre.sirena.org.uk/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/trace_wprobe.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
index 98605b207f43..f2c2f26fd668 100644
--- a/kernel/trace/trace_wprobe.c
+++ b/kernel/trace/trace_wprobe.c
@@ -163,6 +163,8 @@ static void wprobe_perf_handler(struct perf_event *bp,
 static int __register_trace_wprobe(struct trace_wprobe *tw)
 {
 	struct perf_event_attr attr;
+	struct perf_event *bp;
+	int cpu;
 
 	if (tw->bp_event)
 		return -EINVAL;
@@ -179,6 +181,11 @@ static int __register_trace_wprobe(struct trace_wprobe *tw)
 		tw->bp_event = NULL;
 		return ret;
 	}
+	/* Mark wprobe_perf_handler is compatible with default one. */
+	for_each_online_cpu(cpu) {
+		bp = per_cpu(*tw->bp_event, cpu);
+		bp->default_overflow_compatible = true;
+	}
 
 	return 0;
 }