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systemd/src/shared/bpf-dlopen.c
Daan De Meyer 69a283c5f2 shared: Clean up includes 
Split out of #37344.
2025-05-24 14:00:44 +02:00

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/* 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
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