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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 75852C4338F for ; Sun, 1 Aug 2021 05:11:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4752B61058 for ; Sun, 1 Aug 2021 05:11:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229491AbhHAFLg (ORCPT ); Sun, 1 Aug 2021 01:11:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229451AbhHAFLg (ORCPT ); Sun, 1 Aug 2021 01:11:36 -0400 Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0B13C06175F for ; Sat, 31 Jul 2021 22:11:28 -0700 (PDT) Received: by mail-qk1-x72c.google.com with SMTP id c18so13640061qke.2 for ; Sat, 31 Jul 2021 22:11:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=tu+g1PbF2qC1dgZLK4PaRMVsVFJ5AJPHZu8bzgWwdLQ=; b=rKreJpcwgWwT7Hcw8UF2wVDno4rrxsFCYBPz15FtPOTVU7C26i3kI08etquKI9owg2 GICv72vsr5msALS2lPo1mVFhV7lBF4wExvprEk6VeCp5O1TTocARMDhGp6UN6qt8DKmS oHWoiyWhcvZZXjy2DOeUK0NBtR9CJV8aXx+kY74HzRztpzDgPznYMFgyqcjKkdIoM3RR RWLRgHLPIwXRVTTGZirc+WP52k6tTDQqah/MYnB2lIhzmDdoFoEFv3JjXImx+QmbqBR7 5jFOVZ2h+IJ5y9XQshqGkx3qt2QR9PzTYjh+tJgeY+lKCtjLQQZgmTjM6iSkpBQS167o DU0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=tu+g1PbF2qC1dgZLK4PaRMVsVFJ5AJPHZu8bzgWwdLQ=; b=j7MnkVhCZuhvzy03QM3Ef0/csvzwrHP/bTKkwaEOs1RQrR29iVjSdSvYwzMmF52S5h y4agEtXxET/PJbkVYJdpCuv/t7FDyxXTy4lT2d1qmtBEFH8EepzSQwDVHjsyvp9ImCPH wV2aJ7mB/oOzqNp1g0wncwFrQROcpdnSaORqBLqn3157t1LE3D/UjL7qe5F/sWu9uZb3 mmvunGdvh92S9ODKNN23lNLz6MZy2+af8u+R02uNgIjVZ2nLI6ZhjS4lm6YK/Jqm7Alq OvR4lKr7JElesjUKLeJuumgPVKaYbLruAiHT+s7umDawxxtIeHIIRvx+RhBpeBPLm0q7 4Jvw== X-Gm-Message-State: AOAM530jAu2XEf3h2w6v1/Bg8cml2/HfvI5aB51Gf3l/0SdpTmhH671b 7UdDK0QcmVDWwmxCLlE9A8gAuV323TyM X-Google-Smtp-Source: ABdhPJzlR2tEP3e/ICtIF+fTdU412JvLwdFYg6p2TB3wOWSp0tfSGnu+XSVGpd8A1NTRcZUc8OH8Wg== X-Received: by 2002:ae9:e315:: with SMTP id v21mr9542362qkf.81.1627794687245; Sat, 31 Jul 2021 22:11:27 -0700 (PDT) Received: from fujitsu.celeiro.cu ([191.177.175.120]) by smtp.gmail.com with ESMTPSA id h2sm3903345qkf.106.2021.07.31.22.11.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Jul 2021 22:11:26 -0700 (PDT) From: Rafael David Tinoco To: bpf@vger.kernel.org Cc: rafaeldtinoco@gmail.com, andrii.nakryiko@gmail.com Subject: [PATCH bpf-next v4] libbpf: introduce legacy kprobe events support Date: Sun, 1 Aug 2021 02:11:23 -0300 Message-Id: <20210801051123.3822498-1-rafaeldtinoco@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210730053413.1090371-1-andrii@kernel.org> References: <20210730053413.1090371-1-andrii@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Allow kprobe tracepoint events creation through legacy interface, as the kprobe dynamic PMUs support, used by default, was only created in v4.17. After commit "bpf: implement minimal BPF perf link", it was allowed that some extra - to the link - information is accessed through container_of struct bpf_link. This allows the tracing perf event legacy name, and information whether it is a retprobe, to be saved outside bpf_link structure, which would not be optimal. This enables CO.RE support for older kernels. Cc: Andrii Nakryiko Signed-off-by: Rafael David Tinoco --- tools/lib/bpf/libbpf.c | 127 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 125 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index e1b7b2b6618c..40037340a3e7 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -8985,9 +8985,55 @@ 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[192] = {}, 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+%lu", name, 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; + char *legacy_name; + bool is_retprobe; }; static int bpf_link_perf_detach(struct bpf_link *link) @@ -9002,6 +9048,10 @@ static int bpf_link_perf_detach(struct bpf_link *link) close(perf_link->perf_event_fd); close(link->fd); + /* legacy kprobe needs to be removed after perf event fd closure */ + if (perf_link->legacy_name) + remove_kprobe_event_legacy(perf_link->legacy_name, perf_link->is_retprobe); + return libbpf_err(err); } @@ -9009,6 +9059,9 @@ static void bpf_link_perf_dealloc(struct bpf_link *link) { struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); + if (perf_link->legacy_name) + free(perf_link->legacy_name); + free(perf_link); } @@ -9122,6 +9175,26 @@ static int parse_uint_from_file(const char *file, const char *fmt) return ret; } +static bool determine_kprobe_legacy(void) +{ + const char *file = "/sys/bus/event_source/devices/kprobe/type"; + + return access(file, 0) == 0 ? false : true; +} + +static int determine_kprobe_perf_type_legacy(const char *func_name, bool is_retprobe) +{ + char file[192]; + + const char *fname = "/sys/kernel/debug/tracing/events/%s/%s_libbpf_%d/id"; + + snprintf(file, sizeof(file), fname, + 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"; @@ -9197,6 +9270,41 @@ 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, @@ -9208,6 +9316,7 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, unsigned long offset; bool retprobe; int pfd, err; + bool legacy; if (!OPTS_VALID(opts, bpf_kprobe_opts)) return libbpf_err_ptr(-EINVAL); @@ -9216,8 +9325,16 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, offset = OPTS_GET(opts, offset, 0); pe_opts.user_ctx = OPTS_GET(opts, user_ctx, 0); - pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name, - offset, -1 /* pid */); + legacy = determine_kprobe_legacy(); + if (!legacy) { + pfd = perf_event_open_probe(false /* uprobe */, + retprobe, func_name, + offset, -1 /* pid */); + } else { + pfd = perf_event_kprobe_open_legacy(retprobe, func_name, + 0 /* 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, @@ -9233,6 +9350,12 @@ 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_name = strdup(func_name); + perf_link->is_retprobe = retprobe; + } + return link; } -- 2.30.2