libbpf.h

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

/*
 * Common eBPF ELF object loading operations.
 *
 * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
 * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
 * Copyright (C) 2015 Huawei Inc.
 */
#ifndef __LIBBPF_LIBBPF_H
#define __LIBBPF_LIBBPF_H

#include <stdarg.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <sys/types.h>  // for size_t
#include <linux/bpf.h>

#ifdef __cplusplus
extern "C" {
#endif

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

enum libbpf_errno {
	__LIBBPF_ERRNO__START = 4000,

	/* Something wrong in libelf */
	LIBBPF_ERRNO__LIBELF = __LIBBPF_ERRNO__START,
	LIBBPF_ERRNO__FORMAT,	/* BPF object format invalid */
	LIBBPF_ERRNO__KVERSION,	/* Incorrect or no 'version' section */
	LIBBPF_ERRNO__ENDIAN,	/* Endian mismatch */
	LIBBPF_ERRNO__INTERNAL,	/* Internal error in libbpf */
	LIBBPF_ERRNO__RELOC,	/* Relocation failed */
	LIBBPF_ERRNO__LOAD,	/* Load program failure for unknown reason */
	LIBBPF_ERRNO__VERIFY,	/* Kernel verifier blocks program loading */
	LIBBPF_ERRNO__PROG2BIG,	/* Program too big */
	LIBBPF_ERRNO__KVER,	/* Incorrect kernel version */
	LIBBPF_ERRNO__PROGTYPE,	/* Kernel doesn't support this program type */
	LIBBPF_ERRNO__WRNGPID,	/* Wrong pid in netlink message */
	LIBBPF_ERRNO__INVSEQ,	/* Invalid netlink sequence */
	LIBBPF_ERRNO__NLPARSE,	/* netlink parsing error */
	__LIBBPF_ERRNO__END,
};

LIBBPF_API int libbpf_strerror(int err, char *buf, size_t size);

enum libbpf_print_level {
        LIBBPF_WARN,
        LIBBPF_INFO,
        LIBBPF_DEBUG,
};

typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level,
				 const char *, va_list ap);

LIBBPF_API libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn);

/* Hide internal to user */
struct bpf_object;

struct bpf_object_open_attr {
	const char *file;
	enum bpf_prog_type prog_type;
};

/* 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.
 */
#define LIBBPF_OPTS(TYPE, NAME, ...)					    \
	struct TYPE NAME;						    \
	memset(&NAME, 0, sizeof(struct TYPE));				    \
	NAME = (struct TYPE) {						    \
		.sz = sizeof(struct TYPE),				    \
		__VA_ARGS__						    \
	}

struct bpf_object_open_opts {
	/* size of this struct, for forward/backward compatiblity */
	size_t sz;
	/* object name override, if provided:
	 * - for object open from file, this will override setting object
	 *   name from file path's base name;
	 * - for object open from memory buffer, this will specify an object
	 *   name and will override default "<addr>-<buf-size>" name;
	 */
	const char *object_name;
	/* parse map definitions non-strictly, allowing extra attributes/data */
	bool relaxed_maps;
};
#define bpf_object_open_opts__last_field relaxed_maps

LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
LIBBPF_API struct bpf_object *
bpf_object__open_file(const char *path, struct bpf_object_open_opts *opts);
LIBBPF_API struct bpf_object *
bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
		     struct bpf_object_open_opts *opts);

/* deprecated bpf_object__open variants */
LIBBPF_API struct bpf_object *
bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,
			const char *name);
LIBBPF_API struct bpf_object *
bpf_object__open_xattr(struct bpf_object_open_attr *attr);

int bpf_object__section_size(const struct bpf_object *obj, const char *name,
			     __u32 *size);
int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,
				__u32 *off);
LIBBPF_API int bpf_object__pin_maps(struct bpf_object *obj, const char *path);
LIBBPF_API int bpf_object__unpin_maps(struct bpf_object *obj,
				      const char *path);
LIBBPF_API int bpf_object__pin_programs(struct bpf_object *obj,
					const char *path);
LIBBPF_API int bpf_object__unpin_programs(struct bpf_object *obj,
					  const char *path);
LIBBPF_API int bpf_object__pin(struct bpf_object *object, const char *path);
LIBBPF_API void bpf_object__close(struct bpf_object *object);

struct bpf_object_load_attr {
	struct bpf_object *obj;
	int log_level;
	const char *target_btf_path;
};

/* Load/unload object into/from kernel */
LIBBPF_API int bpf_object__load(struct bpf_object *obj);
LIBBPF_API int bpf_object__load_xattr(struct bpf_object_load_attr *attr);
LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
LIBBPF_API const char *bpf_object__name(const struct bpf_object *obj);
LIBBPF_API unsigned int bpf_object__kversion(const struct bpf_object *obj);

struct btf;
LIBBPF_API struct btf *bpf_object__btf(const struct bpf_object *obj);
LIBBPF_API int bpf_object__btf_fd(const struct bpf_object *obj);

LIBBPF_API struct bpf_program *
bpf_object__find_program_by_title(const struct bpf_object *obj,
				  const char *title);

LIBBPF_API struct bpf_object *bpf_object__next(struct bpf_object *prev);
#define bpf_object__for_each_safe(pos, tmp)			\
	for ((pos) = bpf_object__next(NULL),		\
		(tmp) = bpf_object__next(pos);		\
	     (pos) != NULL;				\
	     (pos) = (tmp), (tmp) = bpf_object__next(tmp))

typedef void (*bpf_object_clear_priv_t)(struct bpf_object *, void *);
LIBBPF_API int bpf_object__set_priv(struct bpf_object *obj, void *priv,
				    bpf_object_clear_priv_t clear_priv);
LIBBPF_API void *bpf_object__priv(const struct bpf_object *prog);

LIBBPF_API int
libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
			 enum bpf_attach_type *expected_attach_type);
LIBBPF_API int libbpf_attach_type_by_name(const char *name,
					  enum bpf_attach_type *attach_type);

/* Accessors of bpf_program */
struct bpf_program;
LIBBPF_API struct bpf_program *bpf_program__next(struct bpf_program *prog,
						 const struct bpf_object *obj);

#define bpf_object__for_each_program(pos, obj)		\
	for ((pos) = bpf_program__next(NULL, (obj));	\
	     (pos) != NULL;				\
	     (pos) = bpf_program__next((pos), (obj)))

LIBBPF_API struct bpf_program *bpf_program__prev(struct bpf_program *prog,
						 const struct bpf_object *obj);

typedef void (*bpf_program_clear_priv_t)(struct bpf_program *, void *);

LIBBPF_API int bpf_program__set_priv(struct bpf_program *prog, void *priv,
				     bpf_program_clear_priv_t clear_priv);

LIBBPF_API void *bpf_program__priv(const struct bpf_program *prog);
LIBBPF_API void bpf_program__set_ifindex(struct bpf_program *prog,
					 __u32 ifindex);

LIBBPF_API const char *bpf_program__title(const struct bpf_program *prog,
					  bool needs_copy);

LIBBPF_API int bpf_program__load(struct bpf_program *prog, char *license,
				 __u32 kern_version);
LIBBPF_API int bpf_program__fd(const struct bpf_program *prog);
LIBBPF_API int bpf_program__pin_instance(struct bpf_program *prog,
					 const char *path,
					 int instance);
LIBBPF_API int bpf_program__unpin_instance(struct bpf_program *prog,
					   const char *path,
					   int instance);
LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
LIBBPF_API void bpf_program__unload(struct bpf_program *prog);

struct bpf_link;

LIBBPF_API int bpf_link__destroy(struct bpf_link *link);

LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
LIBBPF_API struct bpf_link *
bpf_program__attach_kprobe(struct bpf_program *prog, bool retprobe,
			   const char *func_name);
LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
			   pid_t pid, const char *binary_path,
			   size_t func_offset);
LIBBPF_API struct bpf_link *
bpf_program__attach_tracepoint(struct bpf_program *prog,
			       const char *tp_category,
			       const char *tp_name);
LIBBPF_API struct bpf_link *
bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
				   const char *tp_name);

struct bpf_insn;

/*
 * Libbpf allows callers to adjust BPF programs before being loaded
 * into kernel. One program in an object file can be transformed into
 * multiple variants to be attached to different hooks.
 *
 * bpf_program_prep_t, bpf_program__set_prep and bpf_program__nth_fd
 * form an API for this purpose.
 *
 * - bpf_program_prep_t:
 *   Defines a 'preprocessor', which is a caller defined function
 *   passed to libbpf through bpf_program__set_prep(), and will be
 *   called before program is loaded. The processor should adjust
 *   the program one time for each instance according to the instance id
 *   passed to it.
 *
 * - bpf_program__set_prep:
 *   Attaches a preprocessor to a BPF program. The number of instances
 *   that should be created is also passed through this function.
 *
 * - bpf_program__nth_fd:
 *   After the program is loaded, get resulting FD of a given instance
 *   of the BPF program.
 *
 * If bpf_program__set_prep() is not used, the program would be loaded
 * without adjustment during bpf_object__load(). The program has only
 * one instance. In this case bpf_program__fd(prog) is equal to
 * bpf_program__nth_fd(prog, 0).
 */

struct bpf_prog_prep_result {
	/*
	 * If not NULL, load new instruction array.
	 * If set to NULL, don't load this instance.
	 */
	struct bpf_insn *new_insn_ptr;
	int new_insn_cnt;

	/* If not NULL, result FD is written to it. */
	int *pfd;
};

/*
 * Parameters of bpf_program_prep_t:
 *  - prog:	The bpf_program being loaded.
 *  - n:	Index of instance being generated.
 *  - insns:	BPF instructions array.
 *  - insns_cnt:Number of instructions in insns.
 *  - res:	Output parameter, result of transformation.
 *
 * Return value:
 *  - Zero:	pre-processing success.
 *  - Non-zero:	pre-processing error, stop loading.
 */
typedef int (*bpf_program_prep_t)(struct bpf_program *prog, int n,
				  struct bpf_insn *insns, int insns_cnt,
				  struct bpf_prog_prep_result *res);

LIBBPF_API int bpf_program__set_prep(struct bpf_program *prog, int nr_instance,
				     bpf_program_prep_t prep);

LIBBPF_API int bpf_program__nth_fd(const struct bpf_program *prog, int n);

/*
 * Adjust type of BPF program. Default is kprobe.
 */
LIBBPF_API int bpf_program__set_socket_filter(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_tracepoint(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_raw_tracepoint(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_kprobe(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_sched_cls(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_sched_act(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_xdp(struct bpf_program *prog);
LIBBPF_API int bpf_program__set_perf_event(struct bpf_program *prog);
LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
				      enum bpf_prog_type type);
LIBBPF_API void
bpf_program__set_expected_attach_type(struct bpf_program *prog,
				      enum bpf_attach_type type);

LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_kprobe(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_sched_cls(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_sched_act(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_xdp(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_perf_event(const struct bpf_program *prog);

/*
 * No need for __attribute__((packed)), all members of 'bpf_map_def'
 * are all aligned.  In addition, using __attribute__((packed))
 * would trigger a -Wpacked warning message, and lead to an error
 * if -Werror is set.
 */
struct bpf_map_def {
	unsigned int type;
	unsigned int key_size;
	unsigned int value_size;
	unsigned int max_entries;
	unsigned int map_flags;
};

/*
 * The 'struct bpf_map' in include/linux/bpf.h is internal to the kernel,
 * so no need to worry about a name clash.
 */
struct bpf_map;
LIBBPF_API struct bpf_map *
bpf_object__find_map_by_name(const struct bpf_object *obj, const char *name);

LIBBPF_API int
bpf_object__find_map_fd_by_name(const struct bpf_object *obj, const char *name);

/*
 * Get bpf_map through the offset of corresponding struct bpf_map_def
 * in the BPF object file.
 */
LIBBPF_API struct bpf_map *
bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset);

LIBBPF_API struct bpf_map *
bpf_map__next(const struct bpf_map *map, const struct bpf_object *obj);
#define bpf_object__for_each_map(pos, obj)		\
	for ((pos) = bpf_map__next(NULL, (obj));	\
	     (pos) != NULL;				\
	     (pos) = bpf_map__next((pos), (obj)))
#define bpf_map__for_each bpf_object__for_each_map

LIBBPF_API struct bpf_map *
bpf_map__prev(const struct bpf_map *map, const struct bpf_object *obj);

LIBBPF_API int bpf_map__fd(const struct bpf_map *map);
LIBBPF_API const struct bpf_map_def *bpf_map__def(const struct bpf_map *map);
LIBBPF_API const char *bpf_map__name(const struct bpf_map *map);
LIBBPF_API __u32 bpf_map__btf_key_type_id(const struct bpf_map *map);
LIBBPF_API __u32 bpf_map__btf_value_type_id(const struct bpf_map *map);

typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv,
				 bpf_map_clear_priv_t clear_priv);
LIBBPF_API void *bpf_map__priv(const struct bpf_map *map);
LIBBPF_API int bpf_map__reuse_fd(struct bpf_map *map, int fd);
LIBBPF_API int bpf_map__resize(struct bpf_map *map, __u32 max_entries);
LIBBPF_API bool bpf_map__is_offload_neutral(const struct bpf_map *map);
LIBBPF_API bool bpf_map__is_internal(const struct bpf_map *map);
LIBBPF_API void bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex);
LIBBPF_API int bpf_map__pin(struct bpf_map *map, const char *path);
LIBBPF_API int bpf_map__unpin(struct bpf_map *map, const char *path);

LIBBPF_API int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd);

LIBBPF_API long libbpf_get_error(const void *ptr);

struct bpf_prog_load_attr {
	const char *file;
	enum bpf_prog_type prog_type;
	enum bpf_attach_type expected_attach_type;
	int ifindex;
	int log_level;
	int prog_flags;
};

LIBBPF_API int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
				   struct bpf_object **pobj, int *prog_fd);
LIBBPF_API int bpf_prog_load(const char *file, enum bpf_prog_type type,
			     struct bpf_object **pobj, int *prog_fd);

LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);

struct perf_buffer;

typedef void (*perf_buffer_sample_fn)(void *ctx, int cpu,
				      void *data, __u32 size);
typedef void (*perf_buffer_lost_fn)(void *ctx, int cpu, __u64 cnt);

/* common use perf buffer options */
struct perf_buffer_opts {
	/* if specified, sample_cb is called for each sample */
	perf_buffer_sample_fn sample_cb;
	/* if specified, lost_cb is called for each batch of lost samples */
	perf_buffer_lost_fn lost_cb;
	/* ctx is provided to sample_cb and lost_cb */
	void *ctx;
};

LIBBPF_API struct perf_buffer *
perf_buffer__new(int map_fd, size_t page_cnt,
		 const struct perf_buffer_opts *opts);

enum bpf_perf_event_ret {
	LIBBPF_PERF_EVENT_DONE	= 0,
	LIBBPF_PERF_EVENT_ERROR	= -1,
	LIBBPF_PERF_EVENT_CONT	= -2,
};

struct perf_event_header;

typedef enum bpf_perf_event_ret
(*perf_buffer_event_fn)(void *ctx, int cpu, struct perf_event_header *event);

/* raw perf buffer options, giving most power and control */
struct perf_buffer_raw_opts {
	/* perf event attrs passed directly into perf_event_open() */
	struct perf_event_attr *attr;
	/* raw event callback */
	perf_buffer_event_fn event_cb;
	/* ctx is provided to event_cb */
	void *ctx;
	/* if cpu_cnt == 0, open all on all possible CPUs (up to the number of
	 * max_entries of given PERF_EVENT_ARRAY map)
	 */
	int cpu_cnt;
	/* if cpu_cnt > 0, cpus is an array of CPUs to open ring buffers on */
	int *cpus;
	/* if cpu_cnt > 0, map_keys specify map keys to set per-CPU FDs for */
	int *map_keys;
};

LIBBPF_API struct perf_buffer *
perf_buffer__new_raw(int map_fd, size_t page_cnt,
		     const struct perf_buffer_raw_opts *opts);

LIBBPF_API void perf_buffer__free(struct perf_buffer *pb);
LIBBPF_API int perf_buffer__poll(struct perf_buffer *pb, int timeout_ms);

typedef enum bpf_perf_event_ret
	(*bpf_perf_event_print_t)(struct perf_event_header *hdr,
				  void *private_data);
LIBBPF_API enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
			   void **copy_mem, size_t *copy_size,
			   bpf_perf_event_print_t fn, void *private_data);

struct nlattr;
typedef int (*libbpf_dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
int libbpf_netlink_open(unsigned int *nl_pid);
int libbpf_nl_get_link(int sock, unsigned int nl_pid,
		       libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie);
int libbpf_nl_get_class(int sock, unsigned int nl_pid, int ifindex,
			libbpf_dump_nlmsg_t dump_class_nlmsg, void *cookie);
int libbpf_nl_get_qdisc(int sock, unsigned int nl_pid, int ifindex,
			libbpf_dump_nlmsg_t dump_qdisc_nlmsg, void *cookie);
int libbpf_nl_get_filter(int sock, unsigned int nl_pid, int ifindex, int handle,
			 libbpf_dump_nlmsg_t dump_filter_nlmsg, void *cookie);

struct bpf_prog_linfo;
struct bpf_prog_info;

LIBBPF_API void bpf_prog_linfo__free(struct bpf_prog_linfo *prog_linfo);
LIBBPF_API struct bpf_prog_linfo *
bpf_prog_linfo__new(const struct bpf_prog_info *info);
LIBBPF_API const struct bpf_line_info *
bpf_prog_linfo__lfind_addr_func(const struct bpf_prog_linfo *prog_linfo,
				__u64 addr, __u32 func_idx, __u32 nr_skip);
LIBBPF_API const struct bpf_line_info *
bpf_prog_linfo__lfind(const struct bpf_prog_linfo *prog_linfo,
		      __u32 insn_off, __u32 nr_skip);

/*
 * Probe for supported system features
 *
 * Note that running many of these probes in a short amount of time can cause
 * the kernel to reach the maximal size of lockable memory allowed for the
 * user, causing subsequent probes to fail. In this case, the caller may want
 * to adjust that limit with setrlimit().
 */
LIBBPF_API bool bpf_probe_prog_type(enum bpf_prog_type prog_type,
				    __u32 ifindex);
LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex);
LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id,
				 enum bpf_prog_type prog_type, __u32 ifindex);

/*
 * Get bpf_prog_info in continuous memory
 *
 * struct bpf_prog_info has multiple arrays. The user has option to choose
 * arrays to fetch from kernel. The following APIs provide an uniform way to
 * fetch these data. All arrays in bpf_prog_info are stored in a single
 * continuous memory region. This makes it easy to store the info in a
 * file.
 *
 * Before writing bpf_prog_info_linear to files, it is necessary to
 * translate pointers in bpf_prog_info to offsets. Helper functions
 * bpf_program__bpil_addr_to_offs() and bpf_program__bpil_offs_to_addr()
 * are introduced to switch between pointers and offsets.
 *
 * Examples:
 *   # To fetch map_ids and prog_tags:
 *   __u64 arrays = (1UL << BPF_PROG_INFO_MAP_IDS) |
 *           (1UL << BPF_PROG_INFO_PROG_TAGS);
 *   struct bpf_prog_info_linear *info_linear =
 *           bpf_program__get_prog_info_linear(fd, arrays);
 *
 *   # To save data in file
 *   bpf_program__bpil_addr_to_offs(info_linear);
 *   write(f, info_linear, sizeof(*info_linear) + info_linear->data_len);
 *
 *   # To read data from file
 *   read(f, info_linear, <proper_size>);
 *   bpf_program__bpil_offs_to_addr(info_linear);
 */
enum bpf_prog_info_array {
	BPF_PROG_INFO_FIRST_ARRAY = 0,
	BPF_PROG_INFO_JITED_INSNS = 0,
	BPF_PROG_INFO_XLATED_INSNS,
	BPF_PROG_INFO_MAP_IDS,
	BPF_PROG_INFO_JITED_KSYMS,
	BPF_PROG_INFO_JITED_FUNC_LENS,
	BPF_PROG_INFO_FUNC_INFO,
	BPF_PROG_INFO_LINE_INFO,
	BPF_PROG_INFO_JITED_LINE_INFO,
	BPF_PROG_INFO_PROG_TAGS,
	BPF_PROG_INFO_LAST_ARRAY,
};

struct bpf_prog_info_linear {
	/* size of struct bpf_prog_info, when the tool is compiled */
	__u32			info_len;
	/* total bytes allocated for data, round up to 8 bytes */
	__u32			data_len;
	/* which arrays are included in data */
	__u64			arrays;
	struct bpf_prog_info	info;
	__u8			data[];
};

LIBBPF_API struct bpf_prog_info_linear *
bpf_program__get_prog_info_linear(int fd, __u64 arrays);

LIBBPF_API void
bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);

LIBBPF_API void
bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);

/*
 * A helper function to get the number of possible CPUs before looking up
 * per-CPU maps. Negative errno is returned on failure.
 *
 * Example usage:
 *
 *     int ncpus = libbpf_num_possible_cpus();
 *     if (ncpus < 0) {
 *          // error handling
 *     }
 *     long values[ncpus];
 *     bpf_map_lookup_elem(per_cpu_map_fd, key, values);
 *
 */
LIBBPF_API int libbpf_num_possible_cpus(void);

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* __LIBBPF_LIBBPF_H */