diff options
Diffstat (limited to 'src/shared/bpf-dlopen.c')
| -rw-r--r-- | src/shared/bpf-dlopen.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/src/shared/bpf-dlopen.c b/src/shared/bpf-dlopen.c new file mode 100644 index 0000000..15301ae --- /dev/null +++ b/src/shared/bpf-dlopen.c @@ -0,0 +1,146 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "dlfcn-util.h" +#include "bpf-dlopen.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 + +struct bpf_link* (*sym_bpf_program__attach_cgroup)(const struct bpf_program *, int); +struct bpf_link* (*sym_bpf_program__attach_lsm)(const struct bpf_program *); +int (*sym_bpf_link__fd)(const struct bpf_link *); +int (*sym_bpf_link__destroy)(struct bpf_link *); +int (*sym_bpf_map__fd)(const struct bpf_map *); +const char* (*sym_bpf_map__name)(const struct bpf_map *); +int (*sym_bpf_map_create)(enum bpf_map_type, const char *, __u32, __u32, __u32, const struct bpf_map_create_opts *); +int (*sym_bpf_map__set_max_entries)(struct bpf_map *, __u32); +int (*sym_bpf_map_update_elem)(int, const void *, const void *, __u64); +int (*sym_bpf_map_delete_elem)(int, const void *); +int (*sym_bpf_map__set_inner_map_fd)(struct bpf_map *, int); +int (*sym_bpf_object__open_skeleton)(struct bpf_object_skeleton *, const struct bpf_object_open_opts *); +int (*sym_bpf_object__load_skeleton)(struct bpf_object_skeleton *); +int (*sym_bpf_object__attach_skeleton)(struct bpf_object_skeleton *); +void (*sym_bpf_object__detach_skeleton)(struct bpf_object_skeleton *); +void (*sym_bpf_object__destroy_skeleton)(struct bpf_object_skeleton *); +int (*sym_libbpf_probe_bpf_prog_type)(enum bpf_prog_type, const void *); +const char* (*sym_bpf_program__name)(const struct bpf_program *); +libbpf_print_fn_t (*sym_libbpf_set_print)(libbpf_print_fn_t); +long (*sym_libbpf_get_error)(const void *); + +/* 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); +bool (*sym_bpf_probe_prog_type)(enum bpf_prog_type, __u32); + +_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(void) { + void *dl; + int r; + + DISABLE_WARNING_DEPRECATED_DECLARATIONS; + + dl = dlopen("libbpf.so.1", RTLD_LAZY); + 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_LAZY); + if (!dl) + return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), + "neither libbpf.so.1 nor libbpf.so.0 are installed: %s", dlerror()); + + /* 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), + DLSYM_ARG_FORCE(bpf_probe_prog_type)); +#else + DLSYM_ARG(bpf_create_map), + DLSYM_ARG(bpf_probe_prog_type)); +#endif + } else { + /* symbols available from 0.7.0 */ + r = dlsym_many_or_warn( + dl, LOG_DEBUG, +#if MODERN_LIBBPF + DLSYM_ARG(bpf_map_create), + DLSYM_ARG(libbpf_probe_bpf_prog_type) +#else + /* These symbols did not exist in old libbpf, hence we cannot type check them */ + DLSYM_ARG_FORCE(bpf_map_create), + DLSYM_ARG_FORCE(libbpf_probe_bpf_prog_type) +#endif + ); + } + + r = dlsym_many_or_warn( + dl, LOG_DEBUG, + DLSYM_ARG(bpf_link__destroy), + DLSYM_ARG(bpf_link__fd), + DLSYM_ARG(bpf_map__fd), + DLSYM_ARG(bpf_map__name), + DLSYM_ARG(bpf_map__set_max_entries), + DLSYM_ARG(bpf_map_update_elem), + DLSYM_ARG(bpf_map_delete_elem), + DLSYM_ARG(bpf_map__set_inner_map_fd), + DLSYM_ARG(bpf_object__open_skeleton), + DLSYM_ARG(bpf_object__load_skeleton), + DLSYM_ARG(bpf_object__attach_skeleton), + DLSYM_ARG(bpf_object__detach_skeleton), + DLSYM_ARG(bpf_object__destroy_skeleton), +#if MODERN_LIBBPF + 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_cgroup), + DLSYM_ARG_FORCE(bpf_program__attach_lsm), +#endif + DLSYM_ARG(bpf_program__name), + DLSYM_ARG(libbpf_set_print), + DLSYM_ARG(libbpf_get_error)); + if (r < 0) + return r; + + /* 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 r; +} + +#else + +int dlopen_bpf(void) { + return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), + "libbpf support is not compiled in."); +} +#endif |