From patchwork Wed Aug 24 03:00:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 12952809 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 094BBC38145 for ; Wed, 24 Aug 2022 03:01:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233254AbiHXDBL (ORCPT ); Tue, 23 Aug 2022 23:01:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232487AbiHXDBG (ORCPT ); Tue, 23 Aug 2022 23:01:06 -0400 Received: from mail-pl1-x64a.google.com (mail-pl1-x64a.google.com [IPv6:2607:f8b0:4864:20::64a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4660078BDF for ; Tue, 23 Aug 2022 20:01:04 -0700 (PDT) Received: by mail-pl1-x64a.google.com with SMTP id s8-20020a170902ea0800b00172e456031eso5227893plg.3 for ; Tue, 23 Aug 2022 20:01:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:from:to:cc; bh=WCcoNm9CfHUDlUWZghP4aILEOIaDe7b2CCdf6VUxjwc=; b=fBatBLiBPpjR1tTxMKb+x51jaRF8xUSzeaOY8P7+Swi5+DftfrdA+Yq+a9DYCk6K4b kT6dAQlviv1dFJs0jq6rAvNjxv8EAO6EO027nP6LMlY+ks+fXp6mDXMBwmXcCskMF6NF pl60w3hJgIJCb3Or4OIE//C0DQCWlYrGfqPMP1UMewXKSmZ4ottcHrsFHlCIqMAR1zFa K/nHe3sP84d4AL/S70Fj98dALAlzCMakbQY/oqeYIHSA0Oe1KfAqsZI+8/S2IzAVFyua tHHCnek/md8rsQBoeYBF4CZVfLLMkXX+lrznpj6ePdPB/VrqTrl2ifYWUt9LQsWUpMb+ QQig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:x-gm-message-state:from:to:cc; bh=WCcoNm9CfHUDlUWZghP4aILEOIaDe7b2CCdf6VUxjwc=; b=W9+htOvyA7vF0KDuorbtwhDyE00fJ92oElBqqJ98NPZ9JGzRGAwKMRF1Iacln0j6hJ DI7+FVFBIP0H04SJceKBjCM6mzuxYvWw7tfm+aIuQ07hIG+RlrbjDystT9HBIBa4Lemi 36NtiH5FIoLBDb7TQrHMYexA20Lt8RW4S90EwGGg4yDaEFYsuCfuysoIUTgfcYMcA6Q+ X7ydrlws7+hzjpM4nhFjbfJYaxxptFgKP+KIwQIWVXAcGgOP4gjEerQjgCg98T5EHSMB 4mcviCC0v+MJsEtTT0dY1B3YSm24n/OfqSELw0/4Pdw6GqDCYUQXq9cmTjbs7AxrrVv4 PMQw== X-Gm-Message-State: ACgBeo3xp7e9hzeI1i/Q7foGpvXAqr0O/IgPkPnTRXv458nm8i15G8SZ gAO/Wmb4ScBSgWFFXBWcEc9zchehmwI= X-Google-Smtp-Source: AA6agR5WGCecoGjEFrLrW0NHrXcyyaIpUGavfdkjS3NUNtEkPfh4ocdNswmQObbIowmxGr1eV6jzq8qw8aY= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2d4:203:87e3:473b:a297:1247]) (user=haoluo job=sendgmr) by 2002:a17:90b:1e50:b0:1fb:811b:27b1 with SMTP id pi16-20020a17090b1e5000b001fb811b27b1mr1044972pjb.172.1661310063793; Tue, 23 Aug 2022 20:01:03 -0700 (PDT) Date: Tue, 23 Aug 2022 20:00:27 -0700 In-Reply-To: <20220824030031.1013441-1-haoluo@google.com> Message-Id: <20220824030031.1013441-2-haoluo@google.com> Mime-Version: 1.0 References: <20220824030031.1013441-1-haoluo@google.com> X-Mailer: git-send-email 2.37.1.595.g718a3a8f04-goog Subject: [PATCH bpf-next v9 1/5] bpf: Introduce cgroup iter From: Hao Luo To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, cgroups@vger.kernel.org, netdev@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Tejun Heo , Zefan Li , KP Singh , Johannes Weiner , Michal Hocko , John Fastabend , Jiri Olsa , Michal Koutny , Roman Gushchin , David Rientjes , Stanislav Fomichev , Shakeel Butt , Yosry Ahmed , Hao Luo Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Cgroup_iter is a type of bpf_iter. It walks over cgroups in four modes: - walking a cgroup's descendants in pre-order. - walking a cgroup's descendants in post-order. - walking a cgroup's ancestors. - process only the given cgroup. When attaching cgroup_iter, one can set a cgroup to the iter_link created from attaching. This cgroup is passed as a file descriptor or cgroup id and serves as the starting point of the walk. If no cgroup is specified, the starting point will be the root cgroup v2. For walking descendants, one can specify the order: either pre-order or post-order. For walking ancestors, the walk starts at the specified cgroup and ends at the root. One can also terminate the walk early by returning 1 from the iter program. Note that because walking cgroup hierarchy holds cgroup_mutex, the iter program is called with cgroup_mutex held. Currently only one session is supported, which means, depending on the volume of data bpf program intends to send to user space, the number of cgroups that can be walked is limited. For example, given the current buffer size is 8 * PAGE_SIZE, if the program sends 64B data for each cgroup, assuming PAGE_SIZE is 4kb, the total number of cgroups that can be walked is 512. This is a limitation of cgroup_iter. If the output data is larger than the kernel buffer size, after all data in the kernel buffer is consumed by user space, the subsequent read() syscall will signal EOPNOTSUPP. In order to work around, the user may have to update their program to reduce the volume of data sent to output. For example, skip some uninteresting cgroups. In future, we may extend bpf_iter flags to allow customizing buffer size. Acked-by: Yonghong Song Acked-by: Tejun Heo Signed-off-by: Hao Luo Signed-off-by: Michal Koutný --- include/linux/bpf.h | 8 + include/uapi/linux/bpf.h | 30 ++ kernel/bpf/Makefile | 3 + kernel/bpf/cgroup_iter.c | 284 ++++++++++++++++++ tools/include/uapi/linux/bpf.h | 30 ++ .../selftests/bpf/prog_tests/btf_dump.c | 4 +- 6 files changed, 357 insertions(+), 2 deletions(-) create mode 100644 kernel/bpf/cgroup_iter.c diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 39bd36359c1e..dc9bf5e95ebf 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -48,6 +48,7 @@ struct mem_cgroup; struct module; struct bpf_func_state; struct ftrace_ops; +struct cgroup; extern struct idr btf_idr; extern spinlock_t btf_idr_lock; @@ -1730,7 +1731,14 @@ int bpf_obj_get_user(const char __user *pathname, int flags); int __init bpf_iter_ ## target(args) { return 0; } struct bpf_iter_aux_info { + /* for map_elem iter */ struct bpf_map *map; + + /* for cgroup iter */ + struct { + struct cgroup *start; /* starting cgroup */ + enum bpf_cgroup_iter_order order; + } cgroup; }; typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog, diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 934a2a8beb87..1c4e1c583880 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -87,10 +87,29 @@ struct bpf_cgroup_storage_key { __u32 attach_type; /* program attach type (enum bpf_attach_type) */ }; +enum bpf_cgroup_iter_order { + BPF_ITER_ORDER_UNSPEC = 0, + BPF_ITER_SELF_ONLY, /* process only a single object. */ + BPF_ITER_DESCENDANTS_PRE, /* walk descendants in pre-order. */ + BPF_ITER_DESCENDANTS_POST, /* walk descendants in post-order. */ + BPF_ITER_ANCESTORS_UP, /* walk ancestors upward. */ +}; + union bpf_iter_link_info { struct { __u32 map_fd; } map; + struct { + enum bpf_cgroup_iter_order order; + + /* At most one of cgroup_fd and cgroup_id can be non-zero. If + * both are zero, the walk starts from the default cgroup v2 + * root. For walking v1 hierarchy, one should always explicitly + * specify cgroup_fd. + */ + __u32 cgroup_fd; + __u64 cgroup_id; + } cgroup; }; /* BPF syscall commands, see bpf(2) man-page for more details. */ @@ -6159,11 +6178,22 @@ struct bpf_link_info { struct { __aligned_u64 target_name; /* in/out: target_name buffer ptr */ __u32 target_name_len; /* in/out: target_name buffer len */ + + /* If the iter specific field is 32 bits, it can be put + * in the first or second union. Otherwise it should be + * put in the second union. + */ union { struct { __u32 map_id; } map; }; + union { + struct { + __u64 cgroup_id; + __u32 order; + } cgroup; + }; } iter; struct { __u32 netns_ino; diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 057ba8e01e70..00e05b69a4df 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -24,6 +24,9 @@ endif ifeq ($(CONFIG_PERF_EVENTS),y) obj-$(CONFIG_BPF_SYSCALL) += stackmap.o endif +ifeq ($(CONFIG_CGROUPS),y) +obj-$(CONFIG_BPF_SYSCALL) += cgroup_iter.o +endif obj-$(CONFIG_CGROUP_BPF) += cgroup.o ifeq ($(CONFIG_INET),y) obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c new file mode 100644 index 000000000000..cf6d763a57d5 --- /dev/null +++ b/kernel/bpf/cgroup_iter.c @@ -0,0 +1,284 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2022 Google */ +#include +#include +#include +#include +#include + +#include "../cgroup/cgroup-internal.h" /* cgroup_mutex and cgroup_is_dead */ + +/* cgroup_iter provides four modes of traversal to the cgroup hierarchy. + * + * 1. Walk the descendants of a cgroup in pre-order. + * 2. Walk the descendants of a cgroup in post-order. + * 3. Walk the ancestors of a cgroup. + * 4. Show the given cgroup only. + * + * For walking descendants, cgroup_iter can walk in either pre-order or + * post-order. For walking ancestors, the iter walks up from a cgroup to + * the root. + * + * The iter program can terminate the walk early by returning 1. Walk + * continues if prog returns 0. + * + * The prog can check (seq->num == 0) to determine whether this is + * the first element. The prog may also be passed a NULL cgroup, + * which means the walk has completed and the prog has a chance to + * do post-processing, such as outputting an epilogue. + * + * Note: the iter_prog is called with cgroup_mutex held. + * + * Currently only one session is supported, which means, depending on the + * volume of data bpf program intends to send to user space, the number + * of cgroups that can be walked is limited. For example, given the current + * buffer size is 8 * PAGE_SIZE, if the program sends 64B data for each + * cgroup, assuming PAGE_SIZE is 4kb, the total number of cgroups that can + * be walked is 512. This is a limitation of cgroup_iter. If the output data + * is larger than the kernel buffer size, after all data in the kernel buffer + * is consumed by user space, the subsequent read() syscall will signal + * EOPNOTSUPP. In order to work around, the user may have to update their + * program to reduce the volume of data sent to output. For example, skip + * some uninteresting cgroups. + */ + +struct bpf_iter__cgroup { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct cgroup *, cgroup); +}; + +struct cgroup_iter_priv { + struct cgroup_subsys_state *start_css; + bool visited_all; + bool terminate; + int order; +}; + +static void *cgroup_iter_seq_start(struct seq_file *seq, loff_t *pos) +{ + struct cgroup_iter_priv *p = seq->private; + + mutex_lock(&cgroup_mutex); + + /* cgroup_iter doesn't support read across multiple sessions. */ + if (*pos > 0) { + if (p->visited_all) + return NULL; + + /* Haven't visited all, but because cgroup_mutex has dropped, + * return -EOPNOTSUPP to indicate incomplete iteration. + */ + return ERR_PTR(-EOPNOTSUPP); + } + + ++*pos; + p->terminate = false; + p->visited_all = false; + if (p->order == BPF_ITER_DESCENDANTS_PRE) + return css_next_descendant_pre(NULL, p->start_css); + else if (p->order == BPF_ITER_DESCENDANTS_POST) + return css_next_descendant_post(NULL, p->start_css); + else if (p->order == BPF_ITER_ANCESTORS_UP) + return p->start_css; + else /* BPF_ITER_SELF_ONLY */ + return p->start_css; +} + +static int __cgroup_iter_seq_show(struct seq_file *seq, + struct cgroup_subsys_state *css, int in_stop); + +static void cgroup_iter_seq_stop(struct seq_file *seq, void *v) +{ + struct cgroup_iter_priv *p = seq->private; + + mutex_unlock(&cgroup_mutex); + + /* pass NULL to the prog for post-processing */ + if (!v) { + __cgroup_iter_seq_show(seq, NULL, true); + p->visited_all = true; + } +} + +static void *cgroup_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct cgroup_subsys_state *curr = (struct cgroup_subsys_state *)v; + struct cgroup_iter_priv *p = seq->private; + + ++*pos; + if (p->terminate) + return NULL; + + if (p->order == BPF_ITER_DESCENDANTS_PRE) + return css_next_descendant_pre(curr, p->start_css); + else if (p->order == BPF_ITER_DESCENDANTS_POST) + return css_next_descendant_post(curr, p->start_css); + else if (p->order == BPF_ITER_ANCESTORS_UP) + return curr->parent; + else /* BPF_ITER_SELF_ONLY */ + return NULL; +} + +static int __cgroup_iter_seq_show(struct seq_file *seq, + struct cgroup_subsys_state *css, int in_stop) +{ + struct cgroup_iter_priv *p = seq->private; + struct bpf_iter__cgroup ctx; + struct bpf_iter_meta meta; + struct bpf_prog *prog; + int ret = 0; + + /* cgroup is dead, skip this element */ + if (css && cgroup_is_dead(css->cgroup)) + return 0; + + ctx.meta = &meta; + ctx.cgroup = css ? css->cgroup : NULL; + meta.seq = seq; + prog = bpf_iter_get_info(&meta, in_stop); + if (prog) + ret = bpf_iter_run_prog(prog, &ctx); + + /* if prog returns > 0, terminate after this element. */ + if (ret != 0) + p->terminate = true; + + return 0; +} + +static int cgroup_iter_seq_show(struct seq_file *seq, void *v) +{ + return __cgroup_iter_seq_show(seq, (struct cgroup_subsys_state *)v, + false); +} + +static const struct seq_operations cgroup_iter_seq_ops = { + .start = cgroup_iter_seq_start, + .next = cgroup_iter_seq_next, + .stop = cgroup_iter_seq_stop, + .show = cgroup_iter_seq_show, +}; + +BTF_ID_LIST_SINGLE(bpf_cgroup_btf_id, struct, cgroup) + +static int cgroup_iter_seq_init(void *priv, struct bpf_iter_aux_info *aux) +{ + struct cgroup_iter_priv *p = (struct cgroup_iter_priv *)priv; + struct cgroup *cgrp = aux->cgroup.start; + + p->start_css = &cgrp->self; + p->terminate = false; + p->visited_all = false; + p->order = aux->cgroup.order; + return 0; +} + +static const struct bpf_iter_seq_info cgroup_iter_seq_info = { + .seq_ops = &cgroup_iter_seq_ops, + .init_seq_private = cgroup_iter_seq_init, + .seq_priv_size = sizeof(struct cgroup_iter_priv), +}; + +static int bpf_iter_attach_cgroup(struct bpf_prog *prog, + union bpf_iter_link_info *linfo, + struct bpf_iter_aux_info *aux) +{ + int fd = linfo->cgroup.cgroup_fd; + u64 id = linfo->cgroup.cgroup_id; + int order = linfo->cgroup.order; + struct cgroup *cgrp; + + if (order != BPF_ITER_DESCENDANTS_PRE && + order != BPF_ITER_DESCENDANTS_POST && + order != BPF_ITER_ANCESTORS_UP && + order != BPF_ITER_SELF_ONLY) + return -EINVAL; + + if (fd && id) + return -EINVAL; + + if (fd) + cgrp = cgroup_get_from_fd(fd); + else if (id) + cgrp = cgroup_get_from_id(id); + else /* walk the entire hierarchy by default. */ + cgrp = cgroup_get_from_path("/"); + + if (IS_ERR(cgrp)) + return PTR_ERR(cgrp); + + aux->cgroup.start = cgrp; + aux->cgroup.order = order; + return 0; +} + +static void bpf_iter_detach_cgroup(struct bpf_iter_aux_info *aux) +{ + cgroup_put(aux->cgroup.start); +} + +static void bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info *aux, + struct seq_file *seq) +{ + char *buf; + + buf = kzalloc(PATH_MAX, GFP_KERNEL); + if (!buf) { + seq_puts(seq, "cgroup_path:\t\n"); + goto show_order; + } + + /* If cgroup_path_ns() fails, buf will be an empty string, cgroup_path + * will print nothing. + * + * Path is in the calling process's cgroup namespace. + */ + cgroup_path_ns(aux->cgroup.start, buf, PATH_MAX, + current->nsproxy->cgroup_ns); + seq_printf(seq, "cgroup_path:\t%s\n", buf); + kfree(buf); + +show_order: + if (aux->cgroup.order == BPF_ITER_DESCENDANTS_PRE) + seq_puts(seq, "order: descendants_pre\n"); + else if (aux->cgroup.order == BPF_ITER_DESCENDANTS_POST) + seq_puts(seq, "order: descendants_post\n"); + else if (aux->cgroup.order == BPF_ITER_ANCESTORS_UP) + seq_puts(seq, "order: ancestors_up\n"); + else /* BPF_ITER_SELF_ONLY */ + seq_puts(seq, "order: self_only\n"); +} + +static int bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info *aux, + struct bpf_link_info *info) +{ + info->iter.cgroup.order = aux->cgroup.order; + info->iter.cgroup.cgroup_id = cgroup_id(aux->cgroup.start); + return 0; +} + +DEFINE_BPF_ITER_FUNC(cgroup, struct bpf_iter_meta *meta, + struct cgroup *cgroup) + +static struct bpf_iter_reg bpf_cgroup_reg_info = { + .target = "cgroup", + .feature = BPF_ITER_RESCHED, + .attach_target = bpf_iter_attach_cgroup, + .detach_target = bpf_iter_detach_cgroup, + .show_fdinfo = bpf_iter_cgroup_show_fdinfo, + .fill_link_info = bpf_iter_cgroup_fill_link_info, + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__cgroup, cgroup), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &cgroup_iter_seq_info, +}; + +static int __init bpf_cgroup_iter_init(void) +{ + bpf_cgroup_reg_info.ctx_arg_info[0].btf_id = bpf_cgroup_btf_id[0]; + return bpf_iter_reg_target(&bpf_cgroup_reg_info); +} + +late_initcall(bpf_cgroup_iter_init); diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 1d6085e15fc8..9696f05bc924 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -87,10 +87,29 @@ struct bpf_cgroup_storage_key { __u32 attach_type; /* program attach type (enum bpf_attach_type) */ }; +enum bpf_cgroup_iter_order { + BPF_ITER_ORDER_UNSPEC = 0, + BPF_ITER_SELF_ONLY, /* process only a single object. */ + BPF_ITER_DESCENDANTS_PRE, /* walk descendants in pre-order. */ + BPF_ITER_DESCENDANTS_POST, /* walk descendants in post-order. */ + BPF_ITER_ANCESTORS_UP, /* walk ancestors upward. */ +}; + union bpf_iter_link_info { struct { __u32 map_fd; } map; + struct { + enum bpf_cgroup_iter_order order; + + /* At most one of cgroup_fd and cgroup_id can be non-zero. If + * both are zero, the walk starts from the default cgroup v2 + * root. For walking v1 hierarchy, one should always explicitly + * specify cgroup_fd. + */ + __u32 cgroup_fd; + __u64 cgroup_id; + } cgroup; }; /* BPF syscall commands, see bpf(2) man-page for more details. */ @@ -6159,11 +6178,22 @@ struct bpf_link_info { struct { __aligned_u64 target_name; /* in/out: target_name buffer ptr */ __u32 target_name_len; /* in/out: target_name buffer len */ + + /* If the iter specific field is 32 bits, it can be put + * in the first or second union. Otherwise it should be + * put in the second union. + */ union { struct { __u32 map_id; } map; }; + union { + struct { + __u64 cgroup_id; + __u32 order; + } cgroup; + }; } iter; struct { __u32 netns_ino; diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c index 5fce7008d1ff..84c1cfaa2b02 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c @@ -764,8 +764,8 @@ static void test_btf_dump_struct_data(struct btf *btf, struct btf_dump *d, /* union with nested struct */ TEST_BTF_DUMP_DATA(btf, d, "union", str, union bpf_iter_link_info, BTF_F_COMPACT, - "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},}", - { .map = { .map_fd = 1 }}); + "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},.cgroup = (struct){.order = (__u32)1,.cgroup_fd = (__u32)1,},}", + { .cgroup = { .order = 1, .cgroup_fd = 1, }}); /* struct skb with nested structs/unions; because type output is so * complex, we don't do a string comparison, just verify we return