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 EF301C4338F for ; Fri, 30 Jul 2021 05:34:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D906960F9B for ; Fri, 30 Jul 2021 05:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236399AbhG3Fel convert rfc822-to-8bit (ORCPT ); Fri, 30 Jul 2021 01:34:41 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:19698 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236802AbhG3Fek (ORCPT ); Fri, 30 Jul 2021 01:34:40 -0400 Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 16U5VbcG002745 for ; Thu, 29 Jul 2021 22:34:36 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3a3vrtdwa1-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 29 Jul 2021 22:34:36 -0700 Received: from intmgw001.37.frc1.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:11d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 29 Jul 2021 22:34:35 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id AA47A3D405B3; Thu, 29 Jul 2021 22:34:34 -0700 (PDT) From: Andrii Nakryiko To: , , CC: , , Peter Zijlstra , Rafael David Tinoco Subject: [PATCH v3 bpf-next 09/14] libbpf: use BPF perf link when supported by kernel Date: Thu, 29 Jul 2021 22:34:08 -0700 Message-ID: <20210730053413.1090371-10-andrii@kernel.org> 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 X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-ORIG-GUID: ajQC4bIB91OGMzFgYxhpj6kQFgd3Vc1O X-Proofpoint-GUID: ajQC4bIB91OGMzFgYxhpj6kQFgd3Vc1O X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-30_03:2021-07-29,2021-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 adultscore=0 priorityscore=1501 mlxlogscore=999 impostorscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 mlxscore=0 phishscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2107300032 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Detect kernel support for BPF perf link and prefer it when attaching to perf_event, tracepoint, kprobe/uprobe. Underlying perf_event FD will be kept open until BPF link is destroyed, at which point both perf_event FD and BPF link FD will be closed. This preserves current behavior in which perf_event FD is open for the duration of bpf_link's lifetime and user is able to "disconnect" bpf_link from underlying FD (with bpf_link__disconnect()), so that bpf_link__destroy() doesn't close underlying perf_event FD.When BPF perf link is used, disconnect will keep both perf_event and bpf_link FDs open, so it will be up to (advanced) user to close them. This approach is demonstrated in bpf_cookie.c selftests, added in this patch set. Cc: Rafael David Tinoco Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 111 +++++++++++++++++++++++++++++++++-------- 1 file changed, 90 insertions(+), 21 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9654b2569ed0..d2230454e2d9 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -193,6 +193,8 @@ enum kern_feature_id { FEAT_MODULE_BTF, /* BTF_KIND_FLOAT support */ FEAT_BTF_FLOAT, + /* BPF perf link support */ + FEAT_PERF_LINK, __FEAT_CNT, }; @@ -4337,6 +4339,37 @@ static int probe_module_btf(void) return !err; } +static int probe_perf_link(void) +{ + struct bpf_load_program_attr attr; + struct bpf_insn insns[] = { + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }; + int prog_fd, link_fd, err; + + memset(&attr, 0, sizeof(attr)); + attr.prog_type = BPF_PROG_TYPE_TRACEPOINT; + attr.insns = insns; + attr.insns_cnt = ARRAY_SIZE(insns); + attr.license = "GPL"; + prog_fd = bpf_load_program_xattr(&attr, NULL, 0); + if (prog_fd < 0) + return -errno; + + /* use invalid perf_event FD to get EBADF, if link is supported; + * otherwise EINVAL should be returned + */ + link_fd = bpf_link_create(prog_fd, -1, BPF_PERF_EVENT, NULL); + err = -errno; /* close() can clobber errno */ + + if (link_fd >= 0) + close(link_fd); + close(prog_fd); + + return link_fd < 0 && err == -EBADF; +} + enum kern_feature_result { FEAT_UNKNOWN = 0, FEAT_SUPPORTED = 1, @@ -4387,6 +4420,9 @@ static struct kern_feature_desc { [FEAT_BTF_FLOAT] = { "BTF_KIND_FLOAT support", probe_kern_btf_float, }, + [FEAT_PERF_LINK] = { + "BPF perf link support", probe_perf_link, + }, }; static bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id) @@ -8949,23 +8985,38 @@ int bpf_link__unpin(struct bpf_link *link) return 0; } -static int bpf_link__detach_perf_event(struct bpf_link *link) +struct bpf_link_perf { + struct bpf_link link; + int perf_event_fd; +}; + +static int bpf_link_perf_detach(struct bpf_link *link) { - int err; + struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link); + int err = 0; - err = ioctl(link->fd, PERF_EVENT_IOC_DISABLE, 0); - if (err) + if (ioctl(perf_link->perf_event_fd, PERF_EVENT_IOC_DISABLE, 0) < 0) err = -errno; + if (perf_link->perf_event_fd != link->fd) + close(perf_link->perf_event_fd); close(link->fd); + return libbpf_err(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); +} + struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, int pfd) { char errmsg[STRERR_BUFSIZE]; - struct bpf_link *link; - int prog_fd, err; + struct bpf_link_perf *link; + int prog_fd, link_fd = -1, err; if (pfd < 0) { pr_warn("prog '%s': invalid perf event FD %d\n", @@ -8982,27 +9033,45 @@ struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog, int pf link = calloc(1, sizeof(*link)); if (!link) return libbpf_err_ptr(-ENOMEM); - link->detach = &bpf_link__detach_perf_event; - link->fd = pfd; + link->link.detach = &bpf_link_perf_detach; + link->link.dealloc = &bpf_link_perf_dealloc; + link->perf_event_fd = pfd; - if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) { - err = -errno; - free(link); - pr_warn("prog '%s': failed to attach to pfd %d: %s\n", - prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); - if (err == -EPROTO) - pr_warn("prog '%s': try add PERF_SAMPLE_CALLCHAIN to or remove exclude_callchain_[kernel|user] from pfd %d\n", - prog->name, pfd); - return libbpf_err_ptr(err); + if (kernel_supports(prog->obj, FEAT_PERF_LINK)) { + link_fd = bpf_link_create(prog_fd, pfd, BPF_PERF_EVENT, NULL); + if (link_fd < 0) { + err = -errno; + pr_warn("prog '%s': failed to create BPF link for perf_event FD %d: %d (%s)\n", + prog->name, pfd, + err, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + goto err_out; + } + link->link.fd = link_fd; + } else { + if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) { + err = -errno; + pr_warn("prog '%s': failed to attach to perf_event FD %d: %s\n", + prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); + if (err == -EPROTO) + pr_warn("prog '%s': try add PERF_SAMPLE_CALLCHAIN to or remove exclude_callchain_[kernel|user] from pfd %d\n", + prog->name, pfd); + goto err_out; + } + link->link.fd = pfd; } if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) { err = -errno; - free(link); - pr_warn("prog '%s': failed to enable pfd %d: %s\n", + pr_warn("prog '%s': failed to enable perf_event FD %d: %s\n", prog->name, pfd, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); - return libbpf_err_ptr(err); + goto err_out; } - return link; + + return &link->link; +err_out: + if (link_fd >= 0) + close(link_fd); + free(link); + return libbpf_err_ptr(err); } /* -- 2.30.2