From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753180AbdLFWrB (ORCPT ); Wed, 6 Dec 2017 17:47:01 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:54510 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752772AbdLFWpY (ORCPT ); Wed, 6 Dec 2017 17:45:24 -0500 Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig102.frc2.facebook.com To: , , , , , , CC: , Song Liu Smtp-Origin-Cluster: frc2c02 Subject: [PATCH v5] bcc: Try use new API to create [k,u]probe with perf_event_open Date: Wed, 6 Dec 2017 14:45:11 -0800 Message-ID: <20171206224518.3598254-2-songliubraving@fb.com> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20171206224518.3598254-1-songliubraving@fb.com> References: <20171206224518.3598254-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-12-06_08:,, signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org New kernel API allows creating [k,u]probe with perf_event_open. This patch tries to use the new API. If the new API doesn't work, we fall back to old API. bpf_detach_probe() looks up the event being removed. If the event is not found, we skip the clean up procedure. Signed-off-by: Song Liu --- src/cc/libbpf.c | 264 +++++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 196 insertions(+), 68 deletions(-) diff --git a/src/cc/libbpf.c b/src/cc/libbpf.c index ef6daf3..1ac685f 100644 --- a/src/cc/libbpf.c +++ b/src/cc/libbpf.c @@ -526,38 +526,113 @@ int bpf_attach_socket(int sock, int prog) { return setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog, sizeof(prog)); } -static int bpf_attach_tracing_event(int progfd, const char *event_path, - struct perf_reader *reader, int pid, int cpu, int group_fd) { - int efd, pfd; - ssize_t bytes; - char buf[256]; - struct perf_event_attr attr = {}; +#define PMU_TYPE_FILE "/sys/bus/event_source/devices/%s/type" +static int bpf_find_probe_type(const char *event_type) +{ + int fd; + int ret; + char buf[64]; - snprintf(buf, sizeof(buf), "%s/id", event_path); - efd = open(buf, O_RDONLY, 0); - if (efd < 0) { - fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); + snprintf(buf, sizeof(buf), PMU_TYPE_FILE, event_type); + + fd = open(buf, O_RDONLY); + if (fd < 0) return -1; - } + ret = read(fd, buf, sizeof(buf)); + close(fd); + if (ret < 0 || ret >= sizeof(buf)) + return -1; + ret = (int)strtol(buf, NULL, 10); + return errno ? -1 : ret; +} - bytes = read(efd, buf, sizeof(buf)); - if (bytes <= 0 || bytes >= sizeof(buf)) { - fprintf(stderr, "read(%s): %s\n", buf, strerror(errno)); - close(efd); +#define PMU_RETPROBE_FILE "/sys/bus/event_source/devices/%s/format/retprobe" +static int bpf_get_retprobe_bit(const char *event_type) +{ + int fd; + int ret; + char buf[64]; + + snprintf(buf, sizeof(buf), PMU_RETPROBE_FILE, event_type); + fd = open(buf, O_RDONLY); + if (fd < 0) + return -1; + ret = read(fd, buf, sizeof(buf)); + close(fd); + if (ret < 0 || ret >= sizeof(buf)) + return -1; + if (strlen(buf) < strlen("config:")) + return -1; + ret = (int)strtol(buf + strlen("config:"), NULL, 10); + return errno ? -1 : ret; +} + +/* + * new kernel API allows creating [k,u]probe with perf_event_open, which + * makes it easier to clean up the [k,u]probe. This function tries to + * create pfd with the new API. + */ +static int bpf_try_perf_event_open_with_probe(const char *name, uint64_t offs, + int pid, int cpu, int group_fd, char *event_type, int is_return) +{ + struct perf_event_attr attr = {}; + int type = bpf_find_probe_type(event_type); + int is_return_bit = bpf_get_retprobe_bit(event_type); + + if (type < 0 || is_return_bit < 0) return -1; - } - close(efd); - buf[bytes] = '\0'; - attr.config = strtol(buf, NULL, 0); - attr.type = PERF_TYPE_TRACEPOINT; attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN; attr.sample_period = 1; attr.wakeup_events = 1; - pfd = syscall(__NR_perf_event_open, &attr, pid, cpu, group_fd, PERF_FLAG_FD_CLOEXEC); + if (is_return) + attr.config |= 1 << is_return_bit; + attr.probe_offset = offs; /* for kprobe, if name is NULL, this the addr */ + attr.size = sizeof(attr); + attr.type = type; + attr.kprobe_func = ptr_to_u64((void *)name); /* also work for uprobe_path */ + return syscall(__NR_perf_event_open, &attr, pid, cpu, group_fd, + PERF_FLAG_FD_CLOEXEC); +} + +static int bpf_attach_tracing_event(int progfd, const char *event_path, + struct perf_reader *reader, int pid, int cpu, int group_fd, int pfd) { + int efd; + ssize_t bytes; + char buf[256]; + struct perf_event_attr attr = {}; + + /* + * Only look up id and call perf_event_open when + * bpf_try_perf_event_open_with_probe() didn't returns valid pfd. + */ if (pfd < 0) { - fprintf(stderr, "perf_event_open(%s/id): %s\n", event_path, strerror(errno)); - return -1; + snprintf(buf, sizeof(buf), "%s/id", event_path); + efd = open(buf, O_RDONLY, 0); + if (efd < 0) { + fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); + return -1; + } + + bytes = read(efd, buf, sizeof(buf)); + if (bytes <= 0 || bytes >= sizeof(buf)) { + fprintf(stderr, "read(%s): %s\n", buf, strerror(errno)); + close(efd); + return -1; + } + close(efd); + buf[bytes] = '\0'; + attr.config = strtol(buf, NULL, 0); + attr.type = PERF_TYPE_TRACEPOINT; + attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN; + attr.sample_period = 1; + attr.wakeup_events = 1; + pfd = syscall(__NR_perf_event_open, &attr, pid, cpu, group_fd, PERF_FLAG_FD_CLOEXEC); + if (pfd < 0) { + fprintf(stderr, "perf_event_open(%s/id): %s\n", event_path, strerror(errno)); + return -1; + } } + perf_reader_set_fd(reader, pfd); if (perf_reader_mmap(reader, attr.type, attr.sample_type) < 0) @@ -585,31 +660,39 @@ void * bpf_attach_kprobe(int progfd, enum bpf_probe_attach_type attach_type, con char event_alias[128]; struct perf_reader *reader = NULL; static char *event_type = "kprobe"; + int pfd; reader = perf_reader_new(cb, NULL, NULL, cb_cookie, probe_perf_reader_page_cnt); if (!reader) goto error; - snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); - kfd = open(buf, O_WRONLY | O_APPEND, 0); - if (kfd < 0) { - fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); - goto error; - } + /* try use new API to create kprobe */ + pfd = bpf_try_perf_event_open_with_probe(fn_name, 0, pid, cpu, group_fd, + event_type, + attach_type != BPF_PROBE_ENTRY); - snprintf(event_alias, sizeof(event_alias), "%s_bcc_%d", ev_name, getpid()); - snprintf(buf, sizeof(buf), "%c:%ss/%s %s", attach_type==BPF_PROBE_ENTRY ? 'p' : 'r', - event_type, event_alias, fn_name); - if (write(kfd, buf, strlen(buf)) < 0) { - if (errno == EINVAL) - fprintf(stderr, "check dmesg output for possible cause\n"); + if (pfd < 0) { + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); + kfd = open(buf, O_WRONLY | O_APPEND, 0); + if (kfd < 0) { + fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); + goto error; + } + + snprintf(event_alias, sizeof(event_alias), "%s_bcc_%d", ev_name, getpid()); + snprintf(buf, sizeof(buf), "%c:%ss/%s %s", attach_type==BPF_PROBE_ENTRY ? 'p' : 'r', + event_type, event_alias, fn_name); + if (write(kfd, buf, strlen(buf)) < 0) { + if (errno == EINVAL) + fprintf(stderr, "check dmesg output for possible cause\n"); + close(kfd); + goto error; + } close(kfd); - goto error; + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s", event_type, event_alias); } - close(kfd); - snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s", event_type, event_alias); - if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd) < 0) + if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd, pfd) < 0) goto error; return reader; @@ -691,42 +774,50 @@ void * bpf_attach_uprobe(int progfd, enum bpf_probe_attach_type attach_type, con struct perf_reader *reader = NULL; static char *event_type = "uprobe"; int res, kfd = -1, ns_fd = -1; + int pfd = -1; reader = perf_reader_new(cb, NULL, NULL, cb_cookie, probe_perf_reader_page_cnt); if (!reader) goto error; - snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); - kfd = open(buf, O_WRONLY | O_APPEND, 0); - if (kfd < 0) { - fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); - goto error; - } + /* try use new API to create uprobe */ + pfd = bpf_try_perf_event_open_with_probe(binary_path, offset, pid, cpu, + group_fd, event_type, attach_type != BPF_PROBE_ENTRY); - res = snprintf(event_alias, sizeof(event_alias), "%s_bcc_%d", ev_name, getpid()); - if (res < 0 || res >= sizeof(event_alias)) { - fprintf(stderr, "Event name (%s) is too long for buffer\n", ev_name); - goto error; - } - res = snprintf(buf, sizeof(buf), "%c:%ss/%s %s:0x%lx", attach_type==BPF_PROBE_ENTRY ? 'p' : 'r', - event_type, event_alias, binary_path, offset); - if (res < 0 || res >= sizeof(buf)) { - fprintf(stderr, "Event alias (%s) too long for buffer\n", event_alias); - goto error; - } + if (pfd < 0) { + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); + kfd = open(buf, O_WRONLY | O_APPEND, 0); + if (kfd < 0) { + fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); + goto error; + } - ns_fd = enter_mount_ns(pid); - if (write(kfd, buf, strlen(buf)) < 0) { - if (errno == EINVAL) - fprintf(stderr, "check dmesg output for possible cause\n"); - goto error; + res = snprintf(event_alias, sizeof(event_alias), "%s_bcc_%d", ev_name, getpid()); + if (res < 0 || res >= sizeof(event_alias)) { + fprintf(stderr, "Event name (%s) is too long for buffer\n", ev_name); + goto error; + } + res = snprintf(buf, sizeof(buf), "%c:%ss/%s %s:0x%lx", attach_type==BPF_PROBE_ENTRY ? 'p' : 'r', + event_type, event_alias, binary_path, offset); + if (res < 0 || res >= sizeof(buf)) { + fprintf(stderr, "Event alias (%s) too long for buffer\n", event_alias); + goto error; + } + + ns_fd = enter_mount_ns(pid); + if (write(kfd, buf, strlen(buf)) < 0) { + if (errno == EINVAL) + fprintf(stderr, "check dmesg output for possible cause\n"); + goto error; + } + close(kfd); + exit_mount_ns(ns_fd); + ns_fd = -1; + + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s", event_type, event_alias); } - close(kfd); - exit_mount_ns(ns_fd); - ns_fd = -1; - snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s", event_type, event_alias); - if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd) < 0) + if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd, pfd) < 0) goto error; return reader; @@ -741,8 +832,43 @@ error: static int bpf_detach_probe(const char *ev_name, const char *event_type) { - int kfd, res; + int kfd = -1, res; char buf[PATH_MAX]; + int found_event = 0; + size_t bufsize = 0; + char *cptr = NULL; + FILE *fp; + + /* + * For [k,u]probe created with perf_event_open (on newer kernel), it is + * not necessary to clean it up in [k,u]probe_events. We first look up + * the %s_bcc_%d line in [k,u]probe_events. If the event is not found, + * it is safe to skip the cleaning up process (write -:... to the file). + */ + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); + fp = fopen(buf, "r"); + if (!fp) { + fprintf(stderr, "open(%s): %s\n", buf, strerror(errno)); + goto error; + } + + res = snprintf(buf, sizeof(buf), "%ss/%s_bcc_%d", event_type, ev_name, getpid()); + if (res < 0 || res >= sizeof(buf)) { + fprintf(stderr, "snprintf(%s): %d\n", ev_name, res); + goto error; + } + + while (getline(&cptr, &bufsize, fp) != -1) + if (strstr(cptr, buf) != NULL) { + found_event = 1; + break; + } + fclose(fp); + fp = NULL; + + if (!found_event) + return 0; + snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events", event_type); kfd = open(buf, O_WRONLY | O_APPEND, 0); if (kfd < 0) { @@ -766,6 +892,8 @@ static int bpf_detach_probe(const char *ev_name, const char *event_type) error: if (kfd >= 0) close(kfd); + if (fp) + fclose(fp); return -1; } @@ -792,7 +920,7 @@ void * bpf_attach_tracepoint(int progfd, const char *tp_category, snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%s/%s", tp_category, tp_name); - if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd) < 0) + if (bpf_attach_tracing_event(progfd, buf, reader, pid, cpu, group_fd, -1) < 0) goto error; return reader; -- 2.9.5