[PATCH bpf-next 2/2] selftests/bpf: ensure snprintf_btf/bpf_iter tests compatibility with old vmlinux.h

[Alan Maguire <alan.maguire@xxxxxxxxxx>]

Andrii reports that bpf selftests relying on "struct btf_ptr" and BTF_F_*
values will not build as vmlinux.h for older kernels will not include
"struct btf_ptr" or the BTF_F_* enum values.  Undefine and redefine
them to work around this.

Fixes: b72091bd4ee4 ("selftests/bpf: Add test for bpf_seq_printf_btf helper")
Fixes: 076a95f5aff2 ("selftests/bpf: Add bpf_snprintf_btf helper tests")
Reported-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/progs/bpf_iter.h       | 23 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/btf_ptr.h        | 27 ++++++++++++++++++++++
 .../selftests/bpf/progs/netif_receive_skb.c        |  2 +-
 3 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/btf_ptr.h

diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h
index df682af..6a12554 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter.h
+++ b/tools/testing/selftests/bpf/progs/bpf_iter.h
@@ -14,6 +14,11 @@
 #define bpf_iter__bpf_map_elem bpf_iter__bpf_map_elem___not_used
 #define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
 #define bpf_iter__sockmap bpf_iter__sockmap___not_used
+#define btf_ptr btf_ptr___not_used
+#define BTF_F_COMPACT BTF_F_COMPACT___not_used
+#define BTF_F_NONAME BTF_F_NONAME___not_used
+#define BTF_F_PTR_RAW BTF_F_PTR_RAW___not_used
+#define BTF_F_ZERO BTF_F_ZERO___not_used
 #include "vmlinux.h"
 #undef bpf_iter_meta
 #undef bpf_iter__bpf_map
@@ -28,6 +33,11 @@
 #undef bpf_iter__bpf_map_elem
 #undef bpf_iter__bpf_sk_storage_map
 #undef bpf_iter__sockmap
+#undef btf_ptr
+#undef BTF_F_COMPACT
+#undef BTF_F_NONAME
+#undef BTF_F_PTR_RAW
+#undef BTF_F_ZERO
 
 struct bpf_iter_meta {
 	struct seq_file *seq;
@@ -105,3 +115,16 @@ struct bpf_iter__sockmap {
 	void *key;
 	struct sock *sk;
 };
+
+struct btf_ptr {
+	void *ptr;
+	__u32 type_id;
+	__u32 flags;
+};
+
+enum {
+	BTF_F_COMPACT	=	(1ULL << 0),
+	BTF_F_NONAME	=	(1ULL << 1),
+	BTF_F_PTR_RAW	=	(1ULL << 2),
+	BTF_F_ZERO	=	(1ULL << 3),
+};
diff --git a/tools/testing/selftests/bpf/progs/btf_ptr.h b/tools/testing/selftests/bpf/progs/btf_ptr.h
new file mode 100644
index 0000000..c3c9797
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf_ptr.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2020, Oracle and/or its affiliates. */
+/* "undefine" structs in vmlinux.h, because we "override" them below */
+#define btf_ptr btf_ptr___not_used
+#define BTF_F_COMPACT BTF_F_COMPACT___not_used
+#define BTF_F_NONAME BTF_F_NONAME___not_used
+#define BTF_F_PTR_RAW BTF_F_PTR_RAW___not_used
+#define BTF_F_ZERO BTF_F_ZERO___not_used
+#include "vmlinux.h"
+#undef btf_ptr
+#undef BTF_F_COMPACT
+#undef BTF_F_NONAME
+#undef BTF_F_PTR_RAW
+#undef BTF_F_ZERO
+
+struct btf_ptr {
+	void *ptr;
+	__u32 type_id;
+	__u32 flags;
+};
+
+enum {
+	BTF_F_COMPACT	=	(1ULL << 0),
+	BTF_F_NONAME	=	(1ULL << 1),
+	BTF_F_PTR_RAW	=	(1ULL << 2),
+	BTF_F_ZERO	=	(1ULL << 3),
+};
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
index b873d80..6b67003 100644
--- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c
+++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2020, Oracle and/or its affiliates. */
 
-#include "vmlinux.h"
+#include "btf_ptr.h"
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include <bpf/bpf_core_read.h>
-- 
1.8.3.1