From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1325C433F5 for ; Mon, 20 Sep 2021 23:18:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 999096121E for ; Mon, 20 Sep 2021 23:18:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239668AbhITXUD convert rfc822-to-8bit (ORCPT ); Mon, 20 Sep 2021 19:20:03 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:7742 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232799AbhITXSC (ORCPT ); Mon, 20 Sep 2021 19:18:02 -0400 Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 18KHwI1J008496 for ; Mon, 20 Sep 2021 16:16:35 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 3b6mgsnmw4-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 20 Sep 2021 16:16:35 -0700 Received: from intmgw001.27.prn2.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::f) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Mon, 20 Sep 2021 16:16:32 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 3666A487A9E1; Mon, 20 Sep 2021 16:16:30 -0700 (PDT) From: Andrii Nakryiko To: , , CC: , Subject: [PATCH bpf-next 3/4] libbpf: refactor and simplify legacy kprobe code Date: Mon, 20 Sep 2021 16:16:16 -0700 Message-ID: <20210920231617.3141867-4-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210920231617.3141867-1-andrii@kernel.org> References: <20210920231617.3141867-1-andrii@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-FB-Source: Intern X-Proofpoint-GUID: UByT5-lawpbkLV8IXTIBqAJHTtOpCMuE X-Proofpoint-ORIG-GUID: UByT5-lawpbkLV8IXTIBqAJHTtOpCMuE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-09-20_07,2021-09-20_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 mlxscore=0 priorityscore=1501 clxscore=1034 phishscore=0 mlxlogscore=999 spamscore=0 impostorscore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109200135 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Refactor legacy kprobe handling code to follow the same logic as uprobe legacy logic added in the next patchs: - add append_to_file() helper that makes it simpler to work with tracefs file-based interface for creating and deleting probes; - move out probe/event name generation outside of the code that adds/removes it, which simplifies bookkeeping significantly; - change the probe name format to start with "libbpf_" prefix and include offset within kernel function; - switch 'unsigned long' to 'size_t' for specifying kprobe offsets, which is consistent with how uprobes define that, simplifies printf()-ing internally, and also avoids unnecessary complications on architectures where sizeof(long) != sizeof(void *). This patch also implicitly fixes the problem with invalid open() error handling present in poke_kprobe_events(), which (the function) this patch removes. Fixes: ca304b40c20d ("libbpf: Introduce legacy kprobe events support") Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 159 ++++++++++++++++++++++------------------- tools/lib/bpf/libbpf.h | 2 +- 2 files changed, 88 insertions(+), 73 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 6d2f12db6034..aa842f0721cb 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9011,59 +9011,17 @@ 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_kprobe; bool legacy_is_retprobe; }; +static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe); + static int bpf_link_perf_detach(struct bpf_link *link) { struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); @@ -9077,9 +9035,12 @@ static int bpf_link_perf_detach(struct bpf_link *link) close(link->fd); /* 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); + if (perf_link->legacy_probe_name) { + if (perf_link->legacy_is_kprobe) { + err = remove_kprobe_event_legacy(perf_link->legacy_probe_name, + perf_link->legacy_is_retprobe); + } + } return err; } @@ -9202,18 +9163,6 @@ 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"; @@ -9296,21 +9245,79 @@ 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) +static int append_to_file(const char *file, const char *fmt, ...) +{ + int fd, n, err = 0; + va_list ap; + + fd = open(file, O_WRONLY | O_APPEND, 0); + if (fd < 0) + return -errno; + + va_start(ap, fmt); + n = vdprintf(fd, fmt, ap); + va_end(ap); + + if (n < 0) + err = -errno; + + close(fd); + return err; +} + +static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, + const char *kfunc_name, size_t offset) +{ + snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset); +} + +static int add_kprobe_event_legacy(const char *probe_name, bool retprobe, + const char *kfunc_name, size_t offset) +{ + const char *file = "/sys/kernel/debug/tracing/kprobe_events"; + + return append_to_file(file, "%c:%s/%s %s+0x%zx", + retprobe ? 'r' : 'p', + retprobe ? "kretprobes" : "kprobes", + probe_name, kfunc_name, offset); +} + +static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe) +{ + const char *file = "/sys/kernel/debug/tracing/kprobe_events"; + + return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name); +} + +static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retprobe) +{ + char file[256]; + + snprintf(file, sizeof(file), + "/sys/kernel/debug/tracing/events/%s/%s/id", + retprobe ? "kretprobes" : "kprobes", probe_name); + + return parse_uint_from_file(file, "%d\n"); +} + +static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe, + const char *kfunc_name, size_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); + err = add_kprobe_event_legacy(probe_name, retprobe, kfunc_name, offset); if (err < 0) { - pr_warn("failed to add legacy kprobe event: %s\n", + pr_warn("failed to add legacy kprobe event for '%s+0x%zx': %s\n", + kfunc_name, offset, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); return err; } - type = determine_kprobe_perf_type_legacy(name, retprobe); + type = determine_kprobe_perf_type_legacy(probe_name, retprobe); if (type < 0) { - pr_warn("failed to determine legacy kprobe event id: %s\n", + pr_warn("failed to determine legacy kprobe event id for '%s+0x%zx': %s\n", + kfunc_name, offset, libbpf_strerror_r(type, errmsg, sizeof(errmsg))); return type; } @@ -9340,7 +9347,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, char errmsg[STRERR_BUFSIZE]; char *legacy_probe = NULL; struct bpf_link *link; - unsigned long offset; + size_t offset; bool retprobe, legacy; int pfd, err; @@ -9357,17 +9364,23 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, func_name, offset, -1 /* pid */, 0 /* ref_ctr_off */); } else { + char probe_name[256]; + + gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), + func_name, offset); + legacy_probe = strdup(func_name); if (!legacy_probe) return libbpf_err_ptr(-ENOMEM); - pfd = perf_event_kprobe_open_legacy(retprobe, func_name, + pfd = perf_event_kprobe_open_legacy(legacy_probe, retprobe, func_name, offset, -1 /* pid */); } if (pfd < 0) { - err = pfd; - pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", func_name, + err = -errno; + pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n", + prog->name, retprobe ? "kretprobe" : "kprobe", + func_name, offset, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); goto err_out; } @@ -9375,8 +9388,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, err = libbpf_get_error(link); if (err) { close(pfd); - pr_warn("prog '%s': failed to attach to %s '%s': %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", func_name, + pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n", + prog->name, retprobe ? "kretprobe" : "kprobe", + func_name, offset, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); goto err_out; } @@ -9384,6 +9398,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, 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_kprobe = true; perf_link->legacy_is_retprobe = retprobe; } diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index c90e3d79e72c..262eb3038e83 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -269,7 +269,7 @@ struct bpf_kprobe_opts { /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; /* function's offset to install kprobe to */ - unsigned long offset; + size_t offset; /* kprobe is return probe */ bool retprobe; size_t :0; -- 2.30.2