tools/lib/bpf/libbpf_common.h

   1 /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
   2
   3 /*
   4  * Common user-facing libbpf helpers.
   5  *
   6  * Copyright (c) 2019 Facebook
   7  */
   8
   9 #ifndef __LIBBPF_LIBBPF_COMMON_H
  10 #define __LIBBPF_LIBBPF_COMMON_H
  11
  12 #include <string.h>
  13
  14 #ifndef LIBBPF_API
  15 #define LIBBPF_API __attribute__((visibility("default")))
  16 #endif
  17
  18 /* Helper macro to declare and initialize libbpf options struct
  19  *
  20  * This dance with uninitialized declaration, followed by memset to zero,
  21  * followed by assignment using compound literal syntax is done to preserve
  22  * ability to use a nice struct field initialization syntax and **hopefully**
  23  * have all the padding bytes initialized to zero. It's not guaranteed though,
  24  * when copying literal, that compiler won't copy garbage in literal's padding
  25  * bytes, but that's the best way I've found and it seems to work in practice.
  26  *
  27  * Macro declares opts struct of given type and name, zero-initializes,
  28  * including any extra padding, it with memset() and then assigns initial
  29  * values provided by users in struct initializer-syntax as varargs.
  30  */
  31 #define DECLARE_LIBBPF_OPTS(TYPE, NAME, ...)                                \
  32         struct TYPE NAME = ({                                               \
  33                 memset(&NAME, 0, sizeof(struct TYPE));                      \
  34                 (struct TYPE) {                                             \
  35                         .sz = sizeof(struct TYPE),                          \
  36                         __VA_ARGS__                                         \
  37                 };                                                          \
  38         })
  39
  40 #endif /* __LIBBPF_LIBBPF_COMMON_H */