[thirdparty/systemd.git] / src / shared / bpf-dlopen.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include "bpf-dlopen.h"
#include "dlfcn-util.h"
#include "log.h"

#if HAVE_LIBBPF

/* libbpf changed types of function prototypes around, so we need to disable some type checking for older
 * libbpf. We consider everything older than 0.7 too old for accurate type checks. */
#if defined(__LIBBPF_CURRENT_VERSION_GEQ)
#if __LIBBPF_CURRENT_VERSION_GEQ(0, 7)
#define MODERN_LIBBPF 1
#endif
#endif
#if !defined(MODERN_LIBBPF)
#define MODERN_LIBBPF 0
#endif

DLSYM_PROTOTYPE(bpf_link__destroy) = NULL;
DLSYM_PROTOTYPE(bpf_link__fd) = NULL;
DLSYM_PROTOTYPE(bpf_link__open) = NULL;
DLSYM_PROTOTYPE(bpf_link__pin) = NULL;
DLSYM_PROTOTYPE(bpf_map__fd) = NULL;
DLSYM_PROTOTYPE(bpf_map__name) = NULL;
DLSYM_PROTOTYPE(bpf_map__set_inner_map_fd) = NULL;
DLSYM_PROTOTYPE(bpf_map__set_max_entries) = NULL;
DLSYM_PROTOTYPE(bpf_map__set_pin_path) = NULL;
DLSYM_PROTOTYPE(bpf_map_delete_elem) = NULL;
DLSYM_PROTOTYPE(bpf_map_get_fd_by_id) = NULL;
DLSYM_PROTOTYPE(bpf_map_lookup_elem) = NULL;
DLSYM_PROTOTYPE(bpf_map_update_elem) = NULL;
DLSYM_PROTOTYPE(bpf_object__attach_skeleton) = NULL;
DLSYM_PROTOTYPE(bpf_object__destroy_skeleton) = NULL;
DLSYM_PROTOTYPE(bpf_object__detach_skeleton) = NULL;
DLSYM_PROTOTYPE(bpf_object__load_skeleton) = NULL;
DLSYM_PROTOTYPE(bpf_object__name) = NULL;
DLSYM_PROTOTYPE(bpf_object__open_skeleton) = NULL;
DLSYM_PROTOTYPE(bpf_object__pin_maps) = NULL;
DLSYM_PROTOTYPE(bpf_program__attach) = NULL;
DLSYM_PROTOTYPE(bpf_program__attach_cgroup) = NULL;
DLSYM_PROTOTYPE(bpf_program__attach_lsm) = NULL;
DLSYM_PROTOTYPE(bpf_program__name) = NULL;
DLSYM_PROTOTYPE(libbpf_get_error) = NULL;
DLSYM_PROTOTYPE(libbpf_set_print) = NULL;
DLSYM_PROTOTYPE(ring_buffer__epoll_fd) = NULL;
DLSYM_PROTOTYPE(ring_buffer__free) = NULL;
DLSYM_PROTOTYPE(ring_buffer__new) = NULL;
DLSYM_PROTOTYPE(ring_buffer__poll) = NULL;

/* new symbols available from libbpf 0.7.0 */
int (*sym_bpf_map_create)(enum bpf_map_type,  const char *, __u32, __u32, __u32, const struct bpf_map_create_opts *);
struct bpf_map* (*sym_bpf_object__next_map)(const struct bpf_object *obj, const struct bpf_map *map);

/* compat symbols removed in libbpf 1.0 */
int (*sym_bpf_create_map)(enum bpf_map_type,  int key_size, int value_size, int max_entries, __u32 map_flags);

_printf_(2,0)
static int bpf_print_func(enum libbpf_print_level level, const char *fmt, va_list ap) {
#if !LOG_TRACE
        /* libbpf logs a lot of details at its debug level, which we don't need to see. */
        if (level == LIBBPF_DEBUG)
                return 0;
#endif
        /* All other levels are downgraded to LOG_DEBUG */

        /* errno is used here, on the assumption that if the log message uses %m, errno will be set to
         * something useful. Otherwise, it shouldn't matter, we may pass 0 or some bogus value. */
        return log_internalv(LOG_DEBUG, errno, NULL, 0, NULL, fmt, ap);
}

int dlopen_bpf_full(int log_level) {
        static int cached = 0;
        void *dl;
        int r;

        if (cached != 0)
                return cached;

        ELF_NOTE_DLOPEN("bpf",
                        "Support firewalling and sandboxing with BPF",
                        ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED,
                        "libbpf.so.1", "libbpf.so.0");

        DISABLE_WARNING_DEPRECATED_DECLARATIONS;

        dl = dlopen("libbpf.so.1", RTLD_NOW|RTLD_NODELETE);
        if (!dl) {
                /* libbpf < 1.0.0 (we rely on 0.1.0+) provide most symbols we care about, but
                 * unfortunately not all until 0.7.0. See bpf-compat.h for more details.
                 * Once we consider we can assume 0.7+ is present we can just use the same symbol
                 * list for both files, and when we assume 1.0+ is present we can remove this dlopen */
                dl = dlopen("libbpf.so.0", RTLD_NOW|RTLD_NODELETE);
                if (!dl)
                        return cached = log_full_errno(log_level, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                                       "Neither libbpf.so.1 nor libbpf.so.0 are installed, cgroup BPF features disabled: %s",
                                                       dlerror());

                log_debug("Loaded 'libbpf.so.0' via dlopen()");

                /* symbols deprecated in 1.0 we use as compat */
                r = dlsym_many_or_warn(
                                dl, LOG_DEBUG,
#if MODERN_LIBBPF
                                /* Don't exist anymore in new libbpf, hence cannot type check them */
                                DLSYM_ARG_FORCE(bpf_create_map)
#else
                                DLSYM_ARG(bpf_create_map)
#endif
                );

                /* NB: we don't try to load bpf_object__next_map() on old versions */
        } else {
                log_debug("Loaded 'libbpf.so.1' via dlopen()");

                /* symbols available from 0.7.0 */
                r = dlsym_many_or_warn(
                                dl, LOG_DEBUG,
#if MODERN_LIBBPF
                                DLSYM_ARG(bpf_map_create),
                                DLSYM_ARG(bpf_object__next_map)
#else
                                /* These symbols did not exist in old libbpf, hence we cannot type check them */
                                DLSYM_ARG_FORCE(bpf_map_create),
                                DLSYM_ARG_FORCE(bpf_object__next_map)
#endif
                );
        }
        if (r < 0)
                return cached = log_full_errno(log_level, r, "Failed to load libbpf symbols, cgroup BPF features disabled: %m");

        r = dlsym_many_or_warn(
                        dl, LOG_DEBUG,
                        DLSYM_ARG(bpf_link__destroy),
                        DLSYM_ARG(bpf_link__fd),
                        DLSYM_ARG(bpf_link__open),
                        DLSYM_ARG(bpf_link__pin),
                        DLSYM_ARG(bpf_map__fd),
                        DLSYM_ARG(bpf_map__name),
                        DLSYM_ARG(bpf_map__set_inner_map_fd),
                        DLSYM_ARG(bpf_map__set_max_entries),
                        DLSYM_ARG(bpf_map__set_pin_path),
                        DLSYM_ARG(bpf_map_delete_elem),
                        DLSYM_ARG(bpf_map_get_fd_by_id),
                        DLSYM_ARG(bpf_map_lookup_elem),
                        DLSYM_ARG(bpf_map_update_elem),
                        DLSYM_ARG(bpf_object__attach_skeleton),
                        DLSYM_ARG(bpf_object__destroy_skeleton),
                        DLSYM_ARG(bpf_object__detach_skeleton),
                        DLSYM_ARG(bpf_object__load_skeleton),
                        DLSYM_ARG(bpf_object__name),
                        DLSYM_ARG(bpf_object__open_skeleton),
                        DLSYM_ARG(bpf_object__pin_maps),
#if MODERN_LIBBPF
                        DLSYM_ARG(bpf_program__attach),
                        DLSYM_ARG(bpf_program__attach_cgroup),
                        DLSYM_ARG(bpf_program__attach_lsm),
#else
                        /* libbpf added a "const" to function parameters where it should not have, ignore this type incompatibility */
                        DLSYM_ARG_FORCE(bpf_program__attach),
                        DLSYM_ARG_FORCE(bpf_program__attach_cgroup),
                        DLSYM_ARG_FORCE(bpf_program__attach_lsm),
#endif
                        DLSYM_ARG(bpf_program__name),
                        DLSYM_ARG(libbpf_get_error),
                        DLSYM_ARG(libbpf_set_print),
                        DLSYM_ARG(ring_buffer__epoll_fd),
                        DLSYM_ARG(ring_buffer__free),
                        DLSYM_ARG(ring_buffer__new),
                        DLSYM_ARG(ring_buffer__poll));
        if (r < 0)
                return cached = log_full_errno(log_level, r, "Failed to load libbpf symbols, cgroup BPF features disabled: %m");

        /* We set the print helper unconditionally. Otherwise libbpf will emit not useful log messages. */
        (void) sym_libbpf_set_print(bpf_print_func);

        REENABLE_WARNING;

        return cached = true;
}

int bpf_get_error_translated(const void *ptr) {
        int r;

        r = sym_libbpf_get_error(ptr);

        switch (r) {
        case -524:
                /* Workaround for kernel bug, BPF returns an internal error instead of translating it, until
                 * it is fixed:
                 * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/errno.h?h=v6.9&id=a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6#n27
                 */
                return -EOPNOTSUPP;
        default:
                return r;
        }
}

#else

int dlopen_bpf_full(int log_level) {
        return log_once_errno(log_level, SYNTHETIC_ERRNO(EOPNOTSUPP),
                              "libbpf support is not compiled in, cgroup BPF features disabled.");
}
#endif
Commit	Line	Data
	1	/* SPDX-License-Identifier: LGPL-2.1-or-later */
	2
	3	#include "bpf-dlopen.h"
	4	#include "dlfcn-util.h"
	5	#include "log.h"
	6
	7	#if HAVE_LIBBPF
	8
	9	/* libbpf changed types of function prototypes around, so we need to disable some type checking for older
	10	* libbpf. We consider everything older than 0.7 too old for accurate type checks. */
	11	#if defined(__LIBBPF_CURRENT_VERSION_GEQ)
	12	#if __LIBBPF_CURRENT_VERSION_GEQ(0, 7)
	13	#define MODERN_LIBBPF 1
	14	#endif
	15	#endif
	16	#if !defined(MODERN_LIBBPF)
	17	#define MODERN_LIBBPF 0
	18	#endif
	19
	20	DLSYM_PROTOTYPE(bpf_link__destroy) = NULL;
	21	DLSYM_PROTOTYPE(bpf_link__fd) = NULL;
	22	DLSYM_PROTOTYPE(bpf_link__open) = NULL;
	23	DLSYM_PROTOTYPE(bpf_link__pin) = NULL;
	24	DLSYM_PROTOTYPE(bpf_map__fd) = NULL;
	25	DLSYM_PROTOTYPE(bpf_map__name) = NULL;
	26	DLSYM_PROTOTYPE(bpf_map__set_inner_map_fd) = NULL;
	27	DLSYM_PROTOTYPE(bpf_map__set_max_entries) = NULL;
	28	DLSYM_PROTOTYPE(bpf_map__set_pin_path) = NULL;
	29	DLSYM_PROTOTYPE(bpf_map_delete_elem) = NULL;
	30	DLSYM_PROTOTYPE(bpf_map_get_fd_by_id) = NULL;
	31	DLSYM_PROTOTYPE(bpf_map_lookup_elem) = NULL;
	32	DLSYM_PROTOTYPE(bpf_map_update_elem) = NULL;
	33	DLSYM_PROTOTYPE(bpf_object__attach_skeleton) = NULL;
	34	DLSYM_PROTOTYPE(bpf_object__destroy_skeleton) = NULL;
	35	DLSYM_PROTOTYPE(bpf_object__detach_skeleton) = NULL;
	36	DLSYM_PROTOTYPE(bpf_object__load_skeleton) = NULL;
	37	DLSYM_PROTOTYPE(bpf_object__name) = NULL;
	38	DLSYM_PROTOTYPE(bpf_object__open_skeleton) = NULL;
	39	DLSYM_PROTOTYPE(bpf_object__pin_maps) = NULL;
	40	DLSYM_PROTOTYPE(bpf_program__attach) = NULL;
	41	DLSYM_PROTOTYPE(bpf_program__attach_cgroup) = NULL;
	42	DLSYM_PROTOTYPE(bpf_program__attach_lsm) = NULL;
	43	DLSYM_PROTOTYPE(bpf_program__name) = NULL;
	44	DLSYM_PROTOTYPE(libbpf_get_error) = NULL;
	45	DLSYM_PROTOTYPE(libbpf_set_print) = NULL;
	46	DLSYM_PROTOTYPE(ring_buffer__epoll_fd) = NULL;
	47	DLSYM_PROTOTYPE(ring_buffer__free) = NULL;
	48	DLSYM_PROTOTYPE(ring_buffer__new) = NULL;
	49	DLSYM_PROTOTYPE(ring_buffer__poll) = NULL;
	50
	51	/* new symbols available from libbpf 0.7.0 */
	52	int (sym_bpf_map_create)(enum bpf_map_type, const char , __u32, __u32, __u32, const struct bpf_map_create_opts *);
	53	struct bpf_map* (sym_bpf_object__next_map)(const struct bpf_object obj, const struct bpf_map *map);
	54
	55	/* compat symbols removed in libbpf 1.0 */
	56	int (*sym_bpf_create_map)(enum bpf_map_type, int key_size, int value_size, int max_entries, __u32 map_flags);
	57
	58	_printf_(2,0)
	59	static int bpf_print_func(enum libbpf_print_level level, const char *fmt, va_list ap) {
	60	#if !LOG_TRACE
	61	/* libbpf logs a lot of details at its debug level, which we don't need to see. */
	62	if (level == LIBBPF_DEBUG)
	63	return 0;
	64	#endif
	65	/* All other levels are downgraded to LOG_DEBUG */
	66
	67	/* errno is used here, on the assumption that if the log message uses %m, errno will be set to
	68	* something useful. Otherwise, it shouldn't matter, we may pass 0 or some bogus value. */
	69	return log_internalv(LOG_DEBUG, errno, NULL, 0, NULL, fmt, ap);
	70	}
	71
	72	int dlopen_bpf_full(int log_level) {
	73	static int cached = 0;
	74	void *dl;
	75	int r;
	76
	77	if (cached != 0)
	78	return cached;
	79
	80	ELF_NOTE_DLOPEN("bpf",
	81	"Support firewalling and sandboxing with BPF",
	82	ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED,
	83	"libbpf.so.1", "libbpf.so.0");
	84
	85	DISABLE_WARNING_DEPRECATED_DECLARATIONS;
	86
	87	dl = dlopen("libbpf.so.1", RTLD_NOW\|RTLD_NODELETE);
	88	if (!dl) {
	89	/* libbpf < 1.0.0 (we rely on 0.1.0+) provide most symbols we care about, but
	90	* unfortunately not all until 0.7.0. See bpf-compat.h for more details.
	91	* Once we consider we can assume 0.7+ is present we can just use the same symbol
	92	* list for both files, and when we assume 1.0+ is present we can remove this dlopen */
	93	dl = dlopen("libbpf.so.0", RTLD_NOW\|RTLD_NODELETE);
	94	if (!dl)
	95	return cached = log_full_errno(log_level, SYNTHETIC_ERRNO(EOPNOTSUPP),
	96	"Neither libbpf.so.1 nor libbpf.so.0 are installed, cgroup BPF features disabled: %s",
	97	dlerror());
	98
	99	log_debug("Loaded 'libbpf.so.0' via dlopen()");
	100
	101	/* symbols deprecated in 1.0 we use as compat */
	102	r = dlsym_many_or_warn(
	103	dl, LOG_DEBUG,
	104	#if MODERN_LIBBPF
	105	/* Don't exist anymore in new libbpf, hence cannot type check them */
	106	DLSYM_ARG_FORCE(bpf_create_map)
	107	#else
	108	DLSYM_ARG(bpf_create_map)
	109	#endif
	110	);
	111
	112	/* NB: we don't try to load bpf_object__next_map() on old versions */
	113	} else {
	114	log_debug("Loaded 'libbpf.so.1' via dlopen()");
	115
	116	/* symbols available from 0.7.0 */
	117	r = dlsym_many_or_warn(
	118	dl, LOG_DEBUG,
	119	#if MODERN_LIBBPF
	120	DLSYM_ARG(bpf_map_create),
	121	DLSYM_ARG(bpf_object__next_map)
	122	#else
	123	/* These symbols did not exist in old libbpf, hence we cannot type check them */
	124	DLSYM_ARG_FORCE(bpf_map_create),
	125	DLSYM_ARG_FORCE(bpf_object__next_map)
	126	#endif
	127	);
	128	}
	129	if (r < 0)
	130	return cached = log_full_errno(log_level, r, "Failed to load libbpf symbols, cgroup BPF features disabled: %m");
	131
	132	r = dlsym_many_or_warn(
	133	dl, LOG_DEBUG,
	134	DLSYM_ARG(bpf_link__destroy),
	135	DLSYM_ARG(bpf_link__fd),
	136	DLSYM_ARG(bpf_link__open),
	137	DLSYM_ARG(bpf_link__pin),
	138	DLSYM_ARG(bpf_map__fd),
	139	DLSYM_ARG(bpf_map__name),
	140	DLSYM_ARG(bpf_map__set_inner_map_fd),
	141	DLSYM_ARG(bpf_map__set_max_entries),
	142	DLSYM_ARG(bpf_map__set_pin_path),
	143	DLSYM_ARG(bpf_map_delete_elem),
	144	DLSYM_ARG(bpf_map_get_fd_by_id),
	145	DLSYM_ARG(bpf_map_lookup_elem),
	146	DLSYM_ARG(bpf_map_update_elem),
	147	DLSYM_ARG(bpf_object__attach_skeleton),
	148	DLSYM_ARG(bpf_object__destroy_skeleton),
	149	DLSYM_ARG(bpf_object__detach_skeleton),
	150	DLSYM_ARG(bpf_object__load_skeleton),
	151	DLSYM_ARG(bpf_object__name),
	152	DLSYM_ARG(bpf_object__open_skeleton),
	153	DLSYM_ARG(bpf_object__pin_maps),
	154	#if MODERN_LIBBPF
	155	DLSYM_ARG(bpf_program__attach),
	156	DLSYM_ARG(bpf_program__attach_cgroup),
	157	DLSYM_ARG(bpf_program__attach_lsm),
	158	#else
	159	/* libbpf added a "const" to function parameters where it should not have, ignore this type incompatibility */
	160	DLSYM_ARG_FORCE(bpf_program__attach),
	161	DLSYM_ARG_FORCE(bpf_program__attach_cgroup),
	162	DLSYM_ARG_FORCE(bpf_program__attach_lsm),
	163	#endif
	164	DLSYM_ARG(bpf_program__name),
	165	DLSYM_ARG(libbpf_get_error),
	166	DLSYM_ARG(libbpf_set_print),
	167	DLSYM_ARG(ring_buffer__epoll_fd),
	168	DLSYM_ARG(ring_buffer__free),
	169	DLSYM_ARG(ring_buffer__new),
	170	DLSYM_ARG(ring_buffer__poll));
	171	if (r < 0)
	172	return cached = log_full_errno(log_level, r, "Failed to load libbpf symbols, cgroup BPF features disabled: %m");
	173
	174	/* We set the print helper unconditionally. Otherwise libbpf will emit not useful log messages. */
	175	(void) sym_libbpf_set_print(bpf_print_func);
	176
	177	REENABLE_WARNING;
	178
	179	return cached = true;
	180	}
	181
	182	int bpf_get_error_translated(const void *ptr) {
	183	int r;
	184
	185	r = sym_libbpf_get_error(ptr);
	186
	187	switch (r) {
	188	case -524:
	189	/* Workaround for kernel bug, BPF returns an internal error instead of translating it, until
	190	* it is fixed:
	191	* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/errno.h?h=v6.9&id=a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6#n27
	192	*/
	193	return -EOPNOTSUPP;
	194	default:
	195	return r;
	196	}
	197	}
	198
	199	#else
	200
	201	int dlopen_bpf_full(int log_level) {
	202	return log_once_errno(log_level, SYNTHETIC_ERRNO(EOPNOTSUPP),
	203	"libbpf support is not compiled in, cgroup BPF features disabled.");
	204	}
	205	#endif