libbpf_common.h

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */

/*
 * Common user-facing libbpf helpers.
 *
 * Copyright (c) 2019 Facebook
 */

#ifndef __LIBBPF_LIBBPF_COMMON_H
#define __LIBBPF_LIBBPF_COMMON_H

#include <string.h>
#include "libbpf_version.h"

#ifndef LIBBPF_API
#define LIBBPF_API __attribute__((visibility("default")))
#endif

#define LIBBPF_DEPRECATED(msg) __attribute__((deprecated(msg)))

/* Mark a symbol as deprecated when libbpf version is >= {major}.{minor} */
#define LIBBPF_DEPRECATED_SINCE(major, minor, msg)			    \
	__LIBBPF_MARK_DEPRECATED_ ## major ## _ ## minor		    \
		(LIBBPF_DEPRECATED("libbpf v" # major "." # minor "+: " msg))

#define __LIBBPF_CURRENT_VERSION_GEQ(major, minor)			    \
	(LIBBPF_MAJOR_VERSION > (major) ||				    \
	 (LIBBPF_MAJOR_VERSION == (major) && LIBBPF_MINOR_VERSION >= (minor)))

/* Add checks for other versions below when planning deprecation of API symbols
 * with the LIBBPF_DEPRECATED_SINCE macro.
 */
#if __LIBBPF_CURRENT_VERSION_GEQ(1, 0)
#define __LIBBPF_MARK_DEPRECATED_1_0(X) X
#else
#define __LIBBPF_MARK_DEPRECATED_1_0(X)
#endif

/* This set of internal macros allows to do "function overloading" based on
 * number of arguments provided by used in backwards-compatible way during the
 * transition to libbpf 1.0
 * It's ugly but necessary evil that will be cleaned up when we get to 1.0.
 * See bpf_prog_load() overload for example.
 */
#define ___libbpf_cat(A, B) A ## B
#define ___libbpf_select(NAME, NUM) ___libbpf_cat(NAME, NUM)
#define ___libbpf_nth(_1, _2, _3, _4, _5, _6, N, ...) N
#define ___libbpf_cnt(...) ___libbpf_nth(__VA_ARGS__, 6, 5, 4, 3, 2, 1)
#define ___libbpf_overload(NAME, ...) ___libbpf_select(NAME, ___libbpf_cnt(__VA_ARGS__))(__VA_ARGS__)

/* Helper macro to declare and initialize libbpf options struct
 *
 * This dance with uninitialized declaration, followed by memset to zero,
 * followed by assignment using compound literal syntax is done to preserve
 * ability to use a nice struct field initialization syntax and **hopefully**
 * have all the padding bytes initialized to zero. It's not guaranteed though,
 * when copying literal, that compiler won't copy garbage in literal's padding
 * bytes, but that's the best way I've found and it seems to work in practice.
 *
 * Macro declares opts struct of given type and name, zero-initializes,
 * including any extra padding, it with memset() and then assigns initial
 * values provided by users in struct initializer-syntax as varargs.
 */
#define LIBBPF_OPTS(TYPE, NAME, ...)					    \
	struct TYPE NAME = ({ 						    \
		memset(&NAME, 0, sizeof(struct TYPE));			    \
		(struct TYPE) {						    \
			.sz = sizeof(struct TYPE),			    \
			__VA_ARGS__					    \
		};							    \
	})

/* Helper macro to clear and optionally reinitialize libbpf options struct
 *
 * Small helper macro to reset all fields and to reinitialize the common
 * structure size member. Values provided by users in struct initializer-
 * syntax as varargs can be provided as well to reinitialize options struct
 * specific members.
 */
#define LIBBPF_OPTS_RESET(NAME, ...)					    \
	do {								    \
		typeof(NAME) ___##NAME = ({ 				    \
			memset(&___##NAME, 0, sizeof(NAME));		    \
			(typeof(NAME)) {				    \
				.sz = sizeof(NAME),			    \
				__VA_ARGS__				    \
			};						    \
		});							    \
		memcpy(&NAME, &___##NAME, sizeof(NAME));		    \
	} while (0)

#endif /* __LIBBPF_LIBBPF_COMMON_H */