selftests: bpf: test writable buffers in raw tps

This tests that:
  * a BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE cannot be attached if it
    uses either:
    * a variable offset to the tracepoint buffer, or
    * an offset beyond the size of the tracepoint buffer
  * a tracer can modify the buffer provided when attached to a writable
    tracepoint in bpf_prog_test_run

Signed-off-by: Matt Mullins <mmullins@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

net/bpf/test_run.c

@@ -13,6 +13,9 @@
 #include <net/sock.h>
 #include <net/tcp.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/bpf_test_run.h>
+
 static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
 			u32 *retval, u32 *time)
 {
@@ -100,6 +103,7 @@ static int bpf_test_finish(const union bpf_attr *kattr,
 	if (err != -ENOSPC)
 		err = 0;
 out:
+	trace_bpf_test_finish(&err);
 	return err;
 }