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 #include "libbpf_version.h"
  14
  15 #ifndef LIBBPF_API
  16 #define LIBBPF_API __attribute__((visibility("default")))
  17 #endif
  18
  19 #define LIBBPF_DEPRECATED(msg) __attribute__((deprecated(msg)))
  20
  21 /* Mark a symbol as deprecated when libbpf version is >= {major}.{minor} */
  22 #define LIBBPF_DEPRECATED_SINCE(major, minor, msg)                          \
  23         __LIBBPF_MARK_DEPRECATED_ ## major ## _ ## minor                    \
  24                 (LIBBPF_DEPRECATED("libbpf v" # major "." # minor "+: " msg))
  25
  26 #define __LIBBPF_CURRENT_VERSION_GEQ(major, minor)                          \
  27         (LIBBPF_MAJOR_VERSION > (major) ||                                  \
  28          (LIBBPF_MAJOR_VERSION == (major) && LIBBPF_MINOR_VERSION >= (minor)))
  29
  30 /* Add checks for other versions below when planning deprecation of API symbols
  31  * with the LIBBPF_DEPRECATED_SINCE macro.
  32  */
  33 #if __LIBBPF_CURRENT_VERSION_GEQ(1, 0)
  34 #define __LIBBPF_MARK_DEPRECATED_1_0(X) X
  35 #else
  36 #define __LIBBPF_MARK_DEPRECATED_1_0(X)
  37 #endif
  38
  39 /* This set of internal macros allows to do "function overloading" based on
  40  * number of arguments provided by used in backwards-compatible way during the
  41  * transition to libbpf 1.0
  42  * It's ugly but necessary evil that will be cleaned up when we get to 1.0.
  43  * See bpf_prog_load() overload for example.
  44  */
  45 #define ___libbpf_cat(A, B) A ## B
  46 #define ___libbpf_select(NAME, NUM) ___libbpf_cat(NAME, NUM)
  47 #define ___libbpf_nth(_1, _2, _3, _4, _5, _6, N, ...) N
  48 #define ___libbpf_cnt(...) ___libbpf_nth(__VA_ARGS__, 6, 5, 4, 3, 2, 1)
  49 #define ___libbpf_overload(NAME, ...) ___libbpf_select(NAME, ___libbpf_cnt(__VA_ARGS__))(__VA_ARGS__)
  50
  51 /* Helper macro to declare and initialize libbpf options struct
  52  *
  53  * This dance with uninitialized declaration, followed by memset to zero,
  54  * followed by assignment using compound literal syntax is done to preserve
  55  * ability to use a nice struct field initialization syntax and **hopefully**
  56  * have all the padding bytes initialized to zero. It's not guaranteed though,
  57  * when copying literal, that compiler won't copy garbage in literal's padding
  58  * bytes, but that's the best way I've found and it seems to work in practice.
  59  *
  60  * Macro declares opts struct of given type and name, zero-initializes,
  61  * including any extra padding, it with memset() and then assigns initial
  62  * values provided by users in struct initializer-syntax as varargs.
  63  */
  64 #define LIBBPF_OPTS(TYPE, NAME, ...)                                        \
  65         struct TYPE NAME = ({                                               \
  66                 memset(&NAME, 0, sizeof(struct TYPE));                      \
  67                 (struct TYPE) {                                             \
  68                         .sz = sizeof(struct TYPE),                          \
  69                         __VA_ARGS__                                         \
  70                 };                                                          \
  71         })
  72
  73 /* Helper macro to clear and optionally reinitialize libbpf options struct
  74  *
  75  * Small helper macro to reset all fields and to reinitialize the common
  76  * structure size member. Values provided by users in struct initializer-
  77  * syntax as varargs can be provided as well to reinitialize options struct
  78  * specific members.
  79  */
  80 #define LIBBPF_OPTS_RESET(NAME, ...)                                        \
  81         do {                                                                \
  82                 typeof(NAME) ___##NAME = ({                                 \
  83                         memset(&___##NAME, 0, sizeof(NAME));                \
  84                         (typeof(NAME)) {                                    \
  85                                 .sz = sizeof(NAME),                         \
  86                                 __VA_ARGS__                                 \
  87                         };                                                  \
  88                 });                                                         \
  89                 memcpy(&NAME, &___##NAME, sizeof(NAME));                    \
  90         } while (0)
  91
  92 #endif /* __LIBBPF_LIBBPF_COMMON_H */