netdev - [PATCH bpf-next 1/4] bpftool: add header guards to generated vmlinux.h

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Date:   Sat, 29 Feb 2020 15:11:09 -0800
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next 1/4] bpftool: add header guards to generated vmlinux.h

Add canonical #ifndef/#define/#endif guard for generated vmlinux.h header with
__VMLINUX_H__ symbol. __VMLINUX_H__ is also going to play double role of
identifying whether vmlinux.h is being used, versus, say, BCC or non-CO-RE
libbpf modes with dependency on kernel headers. This will make it possible to
write helper macro/functions, agnostic to exact BPF program set up.

Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/bpf/bpftool/btf.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index b3745ed711ba..bcaf55b59498 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -389,6 +389,9 @@ static int dump_btf_c(const struct btf *btf,
 	if (IS_ERR(d))
 		return PTR_ERR(d);
 
+	printf("#ifndef __VMLINUX_H__\n");
+	printf("#define __VMLINUX_H__\n");
+	printf("\n");
 	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
 	printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
 	printf("#endif\n\n");
@@ -412,6 +415,8 @@ static int dump_btf_c(const struct btf *btf,
 	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
 	printf("#pragma clang attribute pop\n");
 	printf("#endif\n");
+	printf("\n");
+	printf("#endif /* __VMLINUX_H__ */\n");
 
 done:
 	btf_dump__free(d);
-- 
2.17.1