diff --git a/src/libbpf.c b/src/libbpf.c index 8f579c6..9d99183 100644 --- a/src/libbpf.c +++ b/src/libbpf.c @@ -8993,9 +8993,57 @@ int bpf_link__unpin(struct bpf_link *link) return 0; } +static int poke_kprobe_events(bool add, const char *name, bool retprobe, uint64_t offset) +{ + int fd, ret = 0; + pid_t p = getpid(); + char cmd[260], probename[128], probefunc[128]; + const char *file = "/sys/kernel/debug/tracing/kprobe_events"; + + if (retprobe) + snprintf(probename, sizeof(probename), "kretprobes/%s_libbpf_%u", name, p); + else + snprintf(probename, sizeof(probename), "kprobes/%s_libbpf_%u", name, p); + + if (offset) + snprintf(probefunc, sizeof(probefunc), "%s+%zu", name, (size_t)offset); + + if (add) { + snprintf(cmd, sizeof(cmd), "%c:%s %s", + retprobe ? 'r' : 'p', + probename, + offset ? probefunc : name); + } else { + snprintf(cmd, sizeof(cmd), "-:%s", probename); + } + + fd = open(file, O_WRONLY | O_APPEND, 0); + if (!fd) + return -errno; + ret = write(fd, cmd, strlen(cmd)); + if (ret < 0) + ret = -errno; + close(fd); + + return ret; +} + +static inline int add_kprobe_event_legacy(const char *name, bool retprobe, uint64_t offset) +{ + return poke_kprobe_events(true, name, retprobe, offset); +} + +static inline int remove_kprobe_event_legacy(const char *name, bool retprobe) +{ + return poke_kprobe_events(false, name, retprobe, 0); +} + struct bpf_link_perf { struct bpf_link link; int perf_event_fd; + /* legacy kprobe support: keep track of probe identifier and type */ + char *legacy_probe_name; + bool legacy_is_retprobe; }; static int bpf_link_perf_detach(struct bpf_link *link) @@ -9010,13 +9058,19 @@ static int bpf_link_perf_detach(struct bpf_link *link) close(perf_link->perf_event_fd); close(link->fd); - return libbpf_err(err); + /* legacy kprobe needs to be removed after perf event fd closure */ + if (perf_link->legacy_probe_name) + err = remove_kprobe_event_legacy(perf_link->legacy_probe_name, + perf_link->legacy_is_retprobe); + + return err; } static void bpf_link_perf_dealloc(struct bpf_link *link) { struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); + free(perf_link->legacy_probe_name); free(perf_link); } @@ -9130,6 +9184,18 @@ static int parse_uint_from_file(const char *file, const char *fmt) return ret; } +static int determine_kprobe_perf_type_legacy(const char *func_name, bool is_retprobe) +{ + char file[192]; + + snprintf(file, sizeof(file), + "/sys/kernel/debug/tracing/events/%s/%s_libbpf_%d/id", + is_retprobe ? "kretprobes" : "kprobes", + func_name, getpid()); + + return parse_uint_from_file(file, "%d\n"); +} + static int determine_kprobe_perf_type(void) { const char *file = "/sys/bus/event_source/devices/kprobe/type"; @@ -9212,6 +9278,41 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, return pfd; } +static int perf_event_kprobe_open_legacy(bool retprobe, const char *name, uint64_t offset, int pid) +{ + struct perf_event_attr attr = {}; + char errmsg[STRERR_BUFSIZE]; + int type, pfd, err; + + err = add_kprobe_event_legacy(name, retprobe, offset); + if (err < 0) { + pr_warn("failed to add legacy kprobe event: %s\n", + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + return err; + } + type = determine_kprobe_perf_type_legacy(name, retprobe); + if (type < 0) { + pr_warn("failed to determine legacy kprobe event id: %s\n", + libbpf_strerror_r(type, errmsg, sizeof(errmsg))); + return type; + } + attr.size = sizeof(attr); + attr.config = type; + attr.type = PERF_TYPE_TRACEPOINT; + + pfd = syscall(__NR_perf_event_open, &attr, + pid < 0 ? -1 : pid, /* pid */ + pid == -1 ? 0 : -1, /* cpu */ + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC); + if (pfd < 0) { + err = -errno; + pr_warn("legacy kprobe perf_event_open() failed: %s\n", + libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + return err; + } + return pfd; +} + struct bpf_link * bpf_program__attach_kprobe_opts(struct bpf_program *prog, const char *func_name, @@ -9219,9 +9320,10 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, { DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts); char errmsg[STRERR_BUFSIZE]; + char *legacy_probe = NULL; struct bpf_link *link; unsigned long offset; - bool retprobe; + bool retprobe, legacy; int pfd, err; if (!OPTS_VALID(opts, bpf_kprobe_opts)) @@ -9231,8 +9333,19 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, offset = OPTS_GET(opts, offset, 0); pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0); - pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name, - offset, -1 /* pid */, 0 /* ref_ctr_off */); + legacy = determine_kprobe_perf_type() < 0; + if (!legacy) { + pfd = perf_event_open_probe(false /* uprobe */, retprobe, + func_name, offset, + -1 /* pid */, 0 /* ref_ctr_off */); + } else { + legacy_probe = strdup(func_name); + if (!legacy_probe) + return libbpf_err_ptr(-ENOMEM); + + pfd = perf_event_kprobe_open_legacy(retprobe, func_name, + offset, -1 /* pid */); + } if (pfd < 0) { pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", prog->name, retprobe ? "kretprobe" : "kprobe", func_name, @@ -9248,6 +9361,13 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); return libbpf_err_ptr(err); } + if (legacy) { + struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); + + perf_link->legacy_probe_name = legacy_probe; + perf_link->legacy_is_retprobe = retprobe; + } + return link; }