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libbpf: add compat helpers for libbpf down to 0.1.0
- new symbols are available from libbpf 0.6.0 so could be used with libbpf.so.0, but we're sure the old symbols will be there and this simplifies code - detection at runtime should always work, regardless of whether systemd has been compiled with older or newer libbpf and runs with older or newer libbpf
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5a967e2887
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@ -1050,7 +1050,7 @@ want_bpf_framework = get_option('bpf-framework')
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bpf_compiler = get_option('bpf-compiler')
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bpf_framework_required = want_bpf_framework == 'true'
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libbpf_version_requirement = '>= 0.7.0'
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libbpf_version_requirement = '>= 0.1.0'
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if bpf_compiler == 'gcc'
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libbpf_version_requirement = '>= 1.0.0'
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endif
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@ -72,7 +72,7 @@ static int prepare_restrict_fs_bpf(struct restrict_fs_bpf **ret_obj) {
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sym_bpf_map__name(obj->maps.cgroup_hash));
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/* Dummy map to satisfy the verifier */
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inner_map_fd = sym_bpf_map_create(BPF_MAP_TYPE_HASH, NULL, sizeof(uint32_t), sizeof(uint32_t), 128U, NULL);
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inner_map_fd = compat_bpf_map_create(BPF_MAP_TYPE_HASH, NULL, sizeof(uint32_t), sizeof(uint32_t), 128U, NULL);
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if (inner_map_fd < 0)
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return log_error_errno(errno, "bpf-lsm: Failed to create BPF map: %m");
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@ -202,7 +202,7 @@ int lsm_bpf_unit_restrict_filesystems(Unit *u, const Set *filesystems, bool allo
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return log_unit_error_errno(u, SYNTHETIC_ERRNO(EINVAL),
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"bpf-lsm: BPF LSM object is not installed, has setup failed?");
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int inner_map_fd = sym_bpf_map_create(
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int inner_map_fd = compat_bpf_map_create(
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BPF_MAP_TYPE_HASH,
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NULL,
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sizeof(uint32_t),
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@ -120,7 +120,7 @@ int bpf_socket_bind_supported(void) {
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if (!cgroup_bpf_supported())
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return false;
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if (!sym_libbpf_probe_bpf_prog_type(BPF_PROG_TYPE_CGROUP_SOCK_ADDR, /*opts=*/NULL)) {
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if (!compat_libbpf_probe_bpf_prog_type(BPF_PROG_TYPE_CGROUP_SOCK_ADDR, /*opts=*/NULL)) {
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log_debug("bpf-socket-bind: BPF program type cgroup_sock_addr is not supported");
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return false;
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}
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@ -83,7 +83,7 @@ int restrict_network_interfaces_supported(void) {
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if (!cgroup_bpf_supported())
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return (supported = false);
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if (!sym_libbpf_probe_bpf_prog_type(BPF_PROG_TYPE_CGROUP_SKB, /*opts=*/NULL)) {
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if (!compat_libbpf_probe_bpf_prog_type(BPF_PROG_TYPE_CGROUP_SKB, /*opts=*/NULL)) {
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log_debug("restrict-interfaces: BPF program type cgroup_skb is not supported");
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return (supported = false);
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}
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54
src/shared/bpf-compat.h
Normal file
54
src/shared/bpf-compat.h
Normal file
@ -0,0 +1,54 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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/* libbpf has been moving quickly.
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* They added new symbols in the 0.x versions and shortly after removed
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* deprecated symbols in 1.0.
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* We only need bpf_map_create and libbpf_probe_bpf_prog_type so we work
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* around the incompatibility here by:
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* - declaring both symbols, and looking for either depending on the libbpf
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* so version we found
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* - having helpers that automatically use the appropriate version behind the
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* new API for easy cleanup later
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*
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* The advantage of doing this instead of only looking for the symbols declared at
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* compile time is that we can then load either the old or the new symbols at runtime
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* regardless of the version we were compiled with */
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/* declare the struct for libbpf <= 0.6.0 -- it causes no harm on newer versions */
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struct bpf_map_create_opts;
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/* new symbols available from 0.7.0.
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* We need the symbols here:
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* - after bpf_map_create_opts struct has been defined for older libbpf
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* - before the compat static inline helpers that use them.
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* When removing this file move these back to bpf-dlopen.h */
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extern int (*sym_bpf_map_create)(enum bpf_map_type, const char *, __u32, __u32, __u32, const struct bpf_map_create_opts *);
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extern bool (*sym_libbpf_probe_bpf_prog_type)(enum bpf_prog_type, const void *);
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/* compat symbols removed in libbpf 1.0 */
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extern int (*sym_bpf_create_map)(enum bpf_map_type, int key_size, int value_size, int max_entries, __u32 map_flags);
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extern bool (*sym_bpf_probe_prog_type)(enum bpf_prog_type, __u32);
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/* helpers to use the available variant behind new API */
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static inline int compat_bpf_map_create(enum bpf_map_type map_type,
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const char *map_name,
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__u32 key_size,
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__u32 value_size,
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__u32 max_entries,
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const struct bpf_map_create_opts *opts) {
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if (sym_bpf_map_create)
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return sym_bpf_map_create(map_type, map_name, key_size,
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value_size, max_entries, opts);
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return sym_bpf_create_map(map_type, key_size, value_size, max_entries,
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0 /* opts->map_flags, but opts is always NULL for us so skip build dependency on the type */);
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}
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static inline int compat_libbpf_probe_bpf_prog_type(enum bpf_prog_type prog_type, const void *opts) {
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if (sym_libbpf_probe_bpf_prog_type)
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return sym_libbpf_probe_bpf_prog_type(prog_type, opts);
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return sym_bpf_probe_prog_type(prog_type, 0);
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}
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@ -6,8 +6,6 @@
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#include "strv.h"
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#if HAVE_LIBBPF
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static void *bpf_dl = NULL;
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struct bpf_link* (*sym_bpf_program__attach_cgroup)(struct bpf_program *, int);
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struct bpf_link* (*sym_bpf_program__attach_lsm)(struct bpf_program *);
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int (*sym_bpf_link__fd)(const struct bpf_link *);
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@ -29,6 +27,10 @@ const char* (*sym_bpf_program__name)(const struct bpf_program *);
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libbpf_print_fn_t (*sym_libbpf_set_print)(libbpf_print_fn_t);
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long (*sym_libbpf_get_error)(const void *);
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/* compat symbols removed in libbpf 1.0 */
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int (*sym_bpf_create_map)(enum bpf_map_type, int key_size, int value_size, int max_entries, __u32 map_flags);
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bool (*sym_bpf_probe_prog_type)(enum bpf_prog_type, __u32);
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_printf_(2,0)
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static int bpf_print_func(enum libbpf_print_level level, const char *fmt, va_list ap) {
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#if !LOG_TRACE
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@ -44,16 +46,37 @@ static int bpf_print_func(enum libbpf_print_level level, const char *fmt, va_lis
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}
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int dlopen_bpf(void) {
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void *dl;
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int r;
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FOREACH_STRING(f, "libbpf.so.1", "libbpf.so.0") {
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r = dlopen_many_sym_or_warn(
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&bpf_dl, f, LOG_DEBUG,
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dl = dlopen("libbpf.so.1", RTLD_LAZY);
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if (!dl) {
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/* libbpf < 1.0.0 (we rely on 0.1.0+) provide most symbols we care about, but
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* unfortunately not all until 0.7.0. See bpf-compat.h for more details.
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* Once we consider we can assume 0.7+ is present we can just use the same symbol
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* list for both files, and when we assume 1.0+ is present we can remove this dlopen */
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dl = dlopen("libbpf.so.0", RTLD_LAZY);
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if (!dl)
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return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
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"neither libbpf.so.1 nor libbpf.so.0 are installed: %s", dlerror());
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/* symbols deprecated in 1.0 we use as compat */
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r = dlsym_many_or_warn(dl, LOG_DEBUG,
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DLSYM_ARG(bpf_create_map),
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DLSYM_ARG(bpf_probe_prog_type));
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} else {
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/* symbols available from 0.7.0 */
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r = dlsym_many_or_warn(dl, LOG_DEBUG,
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DLSYM_ARG(bpf_map_create),
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DLSYM_ARG(libbpf_probe_bpf_prog_type));
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}
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r = dlsym_many_or_warn(
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dl, LOG_DEBUG,
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DLSYM_ARG(bpf_link__destroy),
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DLSYM_ARG(bpf_link__fd),
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DLSYM_ARG(bpf_map__fd),
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DLSYM_ARG(bpf_map__name),
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DLSYM_ARG(bpf_map_create),
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DLSYM_ARG(bpf_map__set_max_entries),
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DLSYM_ARG(bpf_map_update_elem),
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DLSYM_ARG(bpf_map_delete_elem),
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@ -66,12 +89,8 @@ int dlopen_bpf(void) {
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DLSYM_ARG(bpf_program__attach_cgroup),
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DLSYM_ARG(bpf_program__attach_lsm),
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DLSYM_ARG(bpf_program__name),
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DLSYM_ARG(libbpf_probe_bpf_prog_type),
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DLSYM_ARG(libbpf_set_print),
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DLSYM_ARG(libbpf_get_error));
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if (r >= 0)
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break;
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}
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if (r < 0)
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return r;
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@ -6,13 +6,14 @@
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#include <bpf/bpf.h>
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#include <bpf/libbpf.h>
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#include "bpf-compat.h"
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extern struct bpf_link* (*sym_bpf_program__attach_cgroup)(struct bpf_program *, int);
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extern struct bpf_link* (*sym_bpf_program__attach_lsm)(struct bpf_program *);
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extern int (*sym_bpf_link__fd)(const struct bpf_link *);
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extern int (*sym_bpf_link__destroy)(struct bpf_link *);
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extern int (*sym_bpf_map__fd)(const struct bpf_map *);
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extern const char* (*sym_bpf_map__name)(const struct bpf_map *);
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extern int (*sym_bpf_map_create)(enum bpf_map_type, const char *, __u32, __u32, __u32, const struct bpf_map_create_opts *);
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extern int (*sym_bpf_map__set_max_entries)(struct bpf_map *, __u32);
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extern int (*sym_bpf_map_update_elem)(int, const void *, const void *, __u64);
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extern int (*sym_bpf_map_delete_elem)(int, const void *);
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@ -25,7 +26,6 @@ extern int (*sym_bpf_object__attach_skeleton)(struct bpf_object_skeleton *);
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extern void (*sym_bpf_object__detach_skeleton)(struct bpf_object_skeleton *);
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extern void (*sym_bpf_object__destroy_skeleton)(struct bpf_object_skeleton *);
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extern const char* (*sym_bpf_program__name)(const struct bpf_program *);
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extern bool (*sym_libbpf_probe_bpf_prog_type)(enum bpf_prog_type, const void *);
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extern libbpf_print_fn_t (*sym_libbpf_set_print)(libbpf_print_fn_t);
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extern long (*sym_libbpf_get_error)(const void *);
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