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-rw-r--r--src/shared/bpf-dlopen.c146
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