netdev - [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf

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Date:   Sat, 9 May 2020 10:59:19 -0700
From:   Yonghong Song <yhs@...com>
To:     Andrii Nakryiko <andriin@...com>, <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>, <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf_helpers.h

These two helpers will be used later in bpf_iter bpf program
bpf_iter_netlink.c. Put them in bpf_helpers.h since they could
be useful in other cases.

Acked-by: Andrii Nakryiko <andriin@...com>
Signed-off-by: Yonghong Song <yhs@...com>
---
 tools/lib/bpf/bpf_helpers.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index da00b87aa199..f67dce2af802 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -36,6 +36,20 @@
 #define __weak __attribute__((weak))
 #endif
 
+/*
+ * Helper macro to manipulate data structures
+ */
+#ifndef offsetof
+#define offsetof(TYPE, MEMBER)  ((size_t)&((TYPE *)0)->MEMBER)
+#endif
+#ifndef container_of
+#define container_of(ptr, type, member)				\
+	({							\
+		void *__mptr = (void *)(ptr);			\
+		((type *)(__mptr - offsetof(type, member)));	\
+	})
+#endif
+
 /*
  * Helper structure used by eBPF C program
  * to describe BPF map attributes to libbpf loader
-- 
2.24.1