[PATCH] selftests/bpf: Add bpf_probe_read_str to bpf_helpers.h

[Tushar Dave <tushar.n.dave@oracle.com>]

Using bpf_probe_read_str() from samples/bpf causes compiler warning.
e.g.
warning: implicit declaration of function 'bpf_probe_read_str' is invalid in C99
      [-Wimplicit-function-declaration]
        num = bpf_probe_read_str(buf, sizeof(buf), ctx->di);
              ^
1 warning generated.

Add bpf_probe_read_str() to bpf_helpers.h so it can be used by
samples/bpf programs.

Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com>
---
 tools/testing/selftests/bpf/bpf_helpers.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index dde2c11..65a266d 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -65,6 +65,8 @@ static int (*bpf_xdp_adjust_head)(void *ctx, int offset) =
 	(void *) BPF_FUNC_xdp_adjust_head;
 static int (*bpf_xdp_adjust_meta)(void *ctx, int offset) =
 	(void *) BPF_FUNC_xdp_adjust_meta;
+static int (*bpf_probe_read_str)(void *dst, int size, void *unsafe_ptr) =
+	(void *) BPF_FUNC_probe_read_str;
 static int (*bpf_setsockopt)(void *ctx, int level, int optname, void *optval,
 			     int optlen) =
 	(void *) BPF_FUNC_setsockopt;
-- 
1.9.1