samples/bpf: add tests for more perf event types

$ trace_event

tests attaching BPF program to HW_CPU_CYCLES, SW_CPU_CLOCK, HW_CACHE_L1D and other events.
It runs 'dd' in the background while bpf program collects user and kernel
stack trace on counter overflow.
User space expects to see sys_read and sys_write in the kernel stack.

$ tracex6

tests reading of various perf counters from BPF program.

Both tests were refactored to increase coverage and be more accurate.

Signed-off-by: Teng Qin <qinteng@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
index 9a9c95f..51e567b 100644
--- a/samples/bpf/bpf_helpers.h
+++ b/samples/bpf/bpf_helpers.h
@@ -31,7 +31,8 @@ static unsigned long long (*bpf_get_current_uid_gid)(void) =
 	(void *) BPF_FUNC_get_current_uid_gid;
 static int (*bpf_get_current_comm)(void *buf, int buf_size) =
 	(void *) BPF_FUNC_get_current_comm;
-static int (*bpf_perf_event_read)(void *map, int index) =
+static unsigned long long (*bpf_perf_event_read)(void *map,
+						 unsigned long long flags) =
 	(void *) BPF_FUNC_perf_event_read;
 static int (*bpf_clone_redirect)(void *ctx, int ifindex, int flags) =
 	(void *) BPF_FUNC_clone_redirect;