libbpf.h

/*
 * 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 __BPF_LIBBPF_H
#define __BPF_LIBBPF_H

#include <stdio.h>
#include <stdbool.h>
#include <linux/err.h>

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__END,
};

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

/*
 * In include/linux/compiler-gcc.h, __printf is defined. However
 * it should be better if libbpf.h doesn't depend on Linux header file.
 * So instead of __printf, here we use gcc attribute directly.
 */
typedef int (*libbpf_print_fn_t)(const char *, ...)
	__attribute__((format(printf, 1, 2)));

void libbpf_set_print(libbpf_print_fn_t warn,
		      libbpf_print_fn_t info,
		      libbpf_print_fn_t debug);

/* Hide internal to user */
struct bpf_object;

struct bpf_object *bpf_object__open(const char *path);
struct bpf_object *bpf_object__open_buffer(void *obj_buf,
					   size_t obj_buf_sz,
					   const char *name);
void bpf_object__close(struct bpf_object *object);

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

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))

/* Accessors of bpf_program. */
struct bpf_program;
struct bpf_program *bpf_program__next(struct bpf_program *prog,
				      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)))

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

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

void *bpf_program__priv(struct bpf_program *prog);

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

int bpf_program__fd(struct bpf_program *prog);

struct bpf_insn;

/*
 * Libbpf allows callers to adjust BPF programs before being loaded
 * into kernel. One program in an object file can be transform into
 * multiple variants to be attached to different code.
 *
 * bpf_program_prep_t, bpf_program__set_prep and bpf_program__nth_fd
 * are APIs for this propose.
 *
 * - bpf_program_prep_t:
 *   It defines '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 instances according to the number
 *   passed to it.
 *
 * - bpf_program__set_prep:
 *   Attachs a preprocessor to a BPF program. The number of instances
 *   whould be created is also passed through this function.
 *
 * - bpf_program__nth_fd:
 *   After the program is loaded, get resuling fds from bpf program for
 *   each instances.
 *
 * If bpf_program__set_prep() is not used, the program whould 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 set 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, 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);

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

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

/*
 * We don't need __attribute__((packed)) now since it is
 * unnecessary for 'bpf_map_def' because they are all aligned.
 * In addition, using it will trigger -Wpacked warning message,
 * and will be treated as an error due to -Werror.
 */
struct bpf_map_def {
	unsigned int type;
	unsigned int key_size;
	unsigned int value_size;
	unsigned int max_entries;
};

/*
 * There is another 'struct bpf_map' in include/linux/map.h. However,
 * it is not a uapi header so no need to consider name clash.
 */
struct bpf_map;
struct bpf_map *
bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);

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

int bpf_map__fd(struct bpf_map *map);
const struct bpf_map_def *bpf_map__def(struct bpf_map *map);
const char *bpf_map__name(struct bpf_map *map);

typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
int bpf_map__set_priv(struct bpf_map *map, void *priv,
		      bpf_map_clear_priv_t clear_priv);
void *bpf_map__priv(struct bpf_map *map);

#endif