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0d92898e85db875159634adefcc19066d34bcf37
systemd/src/shared/bpf-util.c
T
Yu Watanabe a74b3e1778 dlopen-note: move all dlopen notes to dlopen-note.h 
This also switches all these notes to be defined via SD_ELF_NOTE_DLOPEN_ANCHORED().
Consequently, any notes added within unreachable or unused functions will be
automatically garbage-collected by the linker (--gc-sections) instead of
bloating the final binary.

E.g. unused p11-kit library dependency is now dropped from
systemd-repart.standalone binary.

Before:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE    DESCRIPTION                                                SONAME                        PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12           recommended
blkid      Support for block device identification                    libblkid.so.1                 required
libcrypto  Support for cryptographic operations                       libcrypto.so.4 libcrypto.so.3 recommended
mount      Support for mount enumeration                              libmount.so.1                 required
fdisk      Support for reading and writing partition tables           libfdisk.so.1                 required
blkid      Support for block device identification                    libblkid.so.1                 recommended
libcrypto  Support for cryptographic operations                       libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12           suggested
fdisk      Support for reading and writing partition tables           libfdisk.so.1                 suggested
idn        Support for internationalized domain names                 libidn2.so.0                  suggested
mount      Support for mount enumeration                              libmount.so.1                 recommended
selinux    Support for SELinux                                        libselinux.so.1               recommended
tpm        Support for TPM                                            libtss2-esys.so.0             suggested
tpm        Support for TPM                                            libtss2-rc.so.0               suggested
tpm        Support for TPM                                            libtss2-mu.so.0               suggested
tpm        Support for TPM                                            libtss2-tcti-device.so.0      suggested
p11-kit    Support for PKCS11 hardware tokens                         libp11-kit.so.0               suggested
```

After:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE    DESCRIPTION                                                SONAME                        PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12           recommended
blkid      Support for block device identification                    libblkid.so.1                 required
libcrypto  Support for cryptographic operations                       libcrypto.so.4 libcrypto.so.3 recommended
mount      Support for mount enumeration                              libmount.so.1                 required
fdisk      Support for reading and writing partition tables           libfdisk.so.1                 required
blkid      Support for block device identification                    libblkid.so.1                 recommended
libcrypto  Support for cryptographic operations                       libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12           suggested
fdisk      Support for reading and writing partition tables           libfdisk.so.1                 suggested
mount      Support for mount enumeration                              libmount.so.1                 recommended
selinux    Support for SELinux                                        libselinux.so.1               recommended
tpm        Support for TPM                                            libtss2-esys.so.0             suggested
tpm        Support for TPM                                            libtss2-rc.so.0               suggested
tpm        Support for TPM                                            libtss2-mu.so.0               suggested
tpm        Support for TPM                                            libtss2-tcti-device.so.0      suggested
```
2026-07-10 16:34:26 +09:00

181 lines
7.6 KiB
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "bpf-util.h"
#include "dlfcn-util.h"
#include "initrd-util.h"
#include "log.h"
#include "strv.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
static DLSYM_PROTOTYPE(libbpf_get_error) = NULL;
DLSYM_PROTOTYPE(bpf_create_map) = NULL;
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_create) = 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_obj_get_info_by_fd) = 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__next_map) = 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(bpf_program__set_autoload) = NULL;
static int missing_bpf_token_create(int bpffs_fd, struct bpf_token_create_opts *opts) {
return -ENOSYS;
}
DLSYM_PROTOTYPE(bpf_token_create) = missing_bpf_token_create;
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;
_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);
}
#endif
int dlopen_bpf(int log_level) {
#if HAVE_LIBBPF
static void *bpf_dl = NULL;
static int cached = 0;
int r = -ENOENT;
if (bpf_dl)
return 1; /* Already loaded */
if (cached < 0)
return cached; /* Already tried, and failed. */
LIBBPF_NOTE(suggested);
DISABLE_WARNING_DEPRECATED_DECLARATIONS;
FOREACH_STRING(soname, "libbpf.so.1", "libbpf.so.0") {
r = dlopen_many_sym_or_warn(
&bpf_dl, soname, 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_obj_get_info_by_fd),
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(bpf_program__set_autoload),
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)
break;
}
REENABLE_WARNING;
if (r < 0)
return cached = log_full_errno(in_initrd() ? LOG_DEBUG : log_level, r,
"Neither libbpf.so.1 nor libbpf.so.0 are installed, cgroup BPF features disabled.");
/* Version-specific symbols: bpf_create_map exists only in libbpf < 1.0; bpf_map_create and
* bpf_object__next_map only in 0.7+. bpf_token_create only in 1.5+. Unresolved prototypes keep
* their initializers (NULL, or a fallback returning -ENOSYS for bpf_token_create). */
DLSYM_OPTIONAL(bpf_dl, bpf_create_map);
DLSYM_OPTIONAL(bpf_dl, bpf_map_create);
DLSYM_OPTIONAL(bpf_dl, bpf_object__next_map);
DLSYM_OPTIONAL(bpf_dl, bpf_token_create);
/* We set the print helper unconditionally. Otherwise libbpf will emit not useful log messages. */
(void) sym_libbpf_set_print(bpf_print_func);
return 1;
#else
return log_once_errno(log_level, SYNTHETIC_ERRNO(EOPNOTSUPP),
"libbpf support is not compiled in, cgroup BPF features disabled.");
#endif
}
#if HAVE_LIBBPF
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;
}
}
#endif
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