perf/bpf: Create bpf_overflow_handler() stub for !CONFIG_BPF_SYSCALL

This will allow __perf_event_overflow() (which is independent of
CONFIG_BPF_SYSCALL) to call bpf_overflow_handler().
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240412015019.7060-3-khuey@kylehuey.com

kernel/events/core.c

@@ -9643,6 +9643,12 @@ static void perf_event_free_bpf_handler(struct perf_event *event)
 	bpf_prog_put(prog);
 }
 #else
+static void bpf_overflow_handler(struct perf_event *event,
+				 struct perf_sample_data *data,
+				 struct pt_regs *regs)
+{
+}
+
 static int perf_event_set_bpf_handler(struct perf_event *event,
 				      struct bpf_prog *prog,
 				      u64 bpf_cookie)