1d4ccaf58SHao Luo // SPDX-License-Identifier: GPL-2.0-only
2d4ccaf58SHao Luo /* Copyright (c) 2022 Google */
3d4ccaf58SHao Luo #include <linux/bpf.h>
4d4ccaf58SHao Luo #include <linux/btf_ids.h>
5d4ccaf58SHao Luo #include <linux/cgroup.h>
6d4ccaf58SHao Luo #include <linux/kernel.h>
7d4ccaf58SHao Luo #include <linux/seq_file.h>
8d4ccaf58SHao Luo
9d4ccaf58SHao Luo #include "../cgroup/cgroup-internal.h" /* cgroup_mutex and cgroup_is_dead */
10d4ccaf58SHao Luo
11d4ccaf58SHao Luo /* cgroup_iter provides four modes of traversal to the cgroup hierarchy.
12d4ccaf58SHao Luo *
13d4ccaf58SHao Luo * 1. Walk the descendants of a cgroup in pre-order.
14d4ccaf58SHao Luo * 2. Walk the descendants of a cgroup in post-order.
15d4ccaf58SHao Luo * 3. Walk the ancestors of a cgroup.
16d4ccaf58SHao Luo * 4. Show the given cgroup only.
17d4ccaf58SHao Luo *
18d4ccaf58SHao Luo * For walking descendants, cgroup_iter can walk in either pre-order or
19d4ccaf58SHao Luo * post-order. For walking ancestors, the iter walks up from a cgroup to
20d4ccaf58SHao Luo * the root.
21d4ccaf58SHao Luo *
22d4ccaf58SHao Luo * The iter program can terminate the walk early by returning 1. Walk
23d4ccaf58SHao Luo * continues if prog returns 0.
24d4ccaf58SHao Luo *
25d4ccaf58SHao Luo * The prog can check (seq->num == 0) to determine whether this is
26d4ccaf58SHao Luo * the first element. The prog may also be passed a NULL cgroup,
27d4ccaf58SHao Luo * which means the walk has completed and the prog has a chance to
28d4ccaf58SHao Luo * do post-processing, such as outputting an epilogue.
29d4ccaf58SHao Luo *
30d4ccaf58SHao Luo * Note: the iter_prog is called with cgroup_mutex held.
31d4ccaf58SHao Luo *
32d4ccaf58SHao Luo * Currently only one session is supported, which means, depending on the
33d4ccaf58SHao Luo * volume of data bpf program intends to send to user space, the number
34d4ccaf58SHao Luo * of cgroups that can be walked is limited. For example, given the current
35d4ccaf58SHao Luo * buffer size is 8 * PAGE_SIZE, if the program sends 64B data for each
36d4ccaf58SHao Luo * cgroup, assuming PAGE_SIZE is 4kb, the total number of cgroups that can
37d4ccaf58SHao Luo * be walked is 512. This is a limitation of cgroup_iter. If the output data
38d4ccaf58SHao Luo * is larger than the kernel buffer size, after all data in the kernel buffer
39d4ccaf58SHao Luo * is consumed by user space, the subsequent read() syscall will signal
40d4ccaf58SHao Luo * EOPNOTSUPP. In order to work around, the user may have to update their
41d4ccaf58SHao Luo * program to reduce the volume of data sent to output. For example, skip
42d4ccaf58SHao Luo * some uninteresting cgroups.
43d4ccaf58SHao Luo */
44d4ccaf58SHao Luo
45d4ccaf58SHao Luo struct bpf_iter__cgroup {
46d4ccaf58SHao Luo __bpf_md_ptr(struct bpf_iter_meta *, meta);
47d4ccaf58SHao Luo __bpf_md_ptr(struct cgroup *, cgroup);
48d4ccaf58SHao Luo };
49d4ccaf58SHao Luo
50d4ccaf58SHao Luo struct cgroup_iter_priv {
51d4ccaf58SHao Luo struct cgroup_subsys_state *start_css;
52d4ccaf58SHao Luo bool visited_all;
53d4ccaf58SHao Luo bool terminate;
54d4ccaf58SHao Luo int order;
55d4ccaf58SHao Luo };
56d4ccaf58SHao Luo
cgroup_iter_seq_start(struct seq_file * seq,loff_t * pos)57d4ccaf58SHao Luo static void *cgroup_iter_seq_start(struct seq_file *seq, loff_t *pos)
58d4ccaf58SHao Luo {
59d4ccaf58SHao Luo struct cgroup_iter_priv *p = seq->private;
60d4ccaf58SHao Luo
61*4cdb91b0SKamalesh Babulal cgroup_lock();
62d4ccaf58SHao Luo
63d4ccaf58SHao Luo /* cgroup_iter doesn't support read across multiple sessions. */
64d4ccaf58SHao Luo if (*pos > 0) {
65d4ccaf58SHao Luo if (p->visited_all)
66d4ccaf58SHao Luo return NULL;
67d4ccaf58SHao Luo
68d4ccaf58SHao Luo /* Haven't visited all, but because cgroup_mutex has dropped,
69d4ccaf58SHao Luo * return -EOPNOTSUPP to indicate incomplete iteration.
70d4ccaf58SHao Luo */
71d4ccaf58SHao Luo return ERR_PTR(-EOPNOTSUPP);
72d4ccaf58SHao Luo }
73d4ccaf58SHao Luo
74d4ccaf58SHao Luo ++*pos;
75d4ccaf58SHao Luo p->terminate = false;
76d4ccaf58SHao Luo p->visited_all = false;
77d4ffb6f3SHao Luo if (p->order == BPF_CGROUP_ITER_DESCENDANTS_PRE)
78d4ccaf58SHao Luo return css_next_descendant_pre(NULL, p->start_css);
79d4ffb6f3SHao Luo else if (p->order == BPF_CGROUP_ITER_DESCENDANTS_POST)
80d4ccaf58SHao Luo return css_next_descendant_post(NULL, p->start_css);
81ccf365eaSJiapeng Chong else /* BPF_CGROUP_ITER_SELF_ONLY and BPF_CGROUP_ITER_ANCESTORS_UP */
82d4ccaf58SHao Luo return p->start_css;
83d4ccaf58SHao Luo }
84d4ccaf58SHao Luo
85d4ccaf58SHao Luo static int __cgroup_iter_seq_show(struct seq_file *seq,
86d4ccaf58SHao Luo struct cgroup_subsys_state *css, int in_stop);
87d4ccaf58SHao Luo
cgroup_iter_seq_stop(struct seq_file * seq,void * v)88d4ccaf58SHao Luo static void cgroup_iter_seq_stop(struct seq_file *seq, void *v)
89d4ccaf58SHao Luo {
90d4ccaf58SHao Luo struct cgroup_iter_priv *p = seq->private;
91d4ccaf58SHao Luo
92*4cdb91b0SKamalesh Babulal cgroup_unlock();
93d4ccaf58SHao Luo
94d4ccaf58SHao Luo /* pass NULL to the prog for post-processing */
95d4ccaf58SHao Luo if (!v) {
96d4ccaf58SHao Luo __cgroup_iter_seq_show(seq, NULL, true);
97d4ccaf58SHao Luo p->visited_all = true;
98d4ccaf58SHao Luo }
99d4ccaf58SHao Luo }
100d4ccaf58SHao Luo
cgroup_iter_seq_next(struct seq_file * seq,void * v,loff_t * pos)101d4ccaf58SHao Luo static void *cgroup_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos)
102d4ccaf58SHao Luo {
103d4ccaf58SHao Luo struct cgroup_subsys_state *curr = (struct cgroup_subsys_state *)v;
104d4ccaf58SHao Luo struct cgroup_iter_priv *p = seq->private;
105d4ccaf58SHao Luo
106d4ccaf58SHao Luo ++*pos;
107d4ccaf58SHao Luo if (p->terminate)
108d4ccaf58SHao Luo return NULL;
109d4ccaf58SHao Luo
110d4ffb6f3SHao Luo if (p->order == BPF_CGROUP_ITER_DESCENDANTS_PRE)
111d4ccaf58SHao Luo return css_next_descendant_pre(curr, p->start_css);
112d4ffb6f3SHao Luo else if (p->order == BPF_CGROUP_ITER_DESCENDANTS_POST)
113d4ccaf58SHao Luo return css_next_descendant_post(curr, p->start_css);
114d4ffb6f3SHao Luo else if (p->order == BPF_CGROUP_ITER_ANCESTORS_UP)
115d4ccaf58SHao Luo return curr->parent;
116d4ffb6f3SHao Luo else /* BPF_CGROUP_ITER_SELF_ONLY */
117d4ccaf58SHao Luo return NULL;
118d4ccaf58SHao Luo }
119d4ccaf58SHao Luo
__cgroup_iter_seq_show(struct seq_file * seq,struct cgroup_subsys_state * css,int in_stop)120d4ccaf58SHao Luo static int __cgroup_iter_seq_show(struct seq_file *seq,
121d4ccaf58SHao Luo struct cgroup_subsys_state *css, int in_stop)
122d4ccaf58SHao Luo {
123d4ccaf58SHao Luo struct cgroup_iter_priv *p = seq->private;
124d4ccaf58SHao Luo struct bpf_iter__cgroup ctx;
125d4ccaf58SHao Luo struct bpf_iter_meta meta;
126d4ccaf58SHao Luo struct bpf_prog *prog;
127d4ccaf58SHao Luo int ret = 0;
128d4ccaf58SHao Luo
129d4ccaf58SHao Luo /* cgroup is dead, skip this element */
130d4ccaf58SHao Luo if (css && cgroup_is_dead(css->cgroup))
131d4ccaf58SHao Luo return 0;
132d4ccaf58SHao Luo
133d4ccaf58SHao Luo ctx.meta = &meta;
134d4ccaf58SHao Luo ctx.cgroup = css ? css->cgroup : NULL;
135d4ccaf58SHao Luo meta.seq = seq;
136d4ccaf58SHao Luo prog = bpf_iter_get_info(&meta, in_stop);
137d4ccaf58SHao Luo if (prog)
138d4ccaf58SHao Luo ret = bpf_iter_run_prog(prog, &ctx);
139d4ccaf58SHao Luo
140d4ccaf58SHao Luo /* if prog returns > 0, terminate after this element. */
141d4ccaf58SHao Luo if (ret != 0)
142d4ccaf58SHao Luo p->terminate = true;
143d4ccaf58SHao Luo
144d4ccaf58SHao Luo return 0;
145d4ccaf58SHao Luo }
146d4ccaf58SHao Luo
cgroup_iter_seq_show(struct seq_file * seq,void * v)147d4ccaf58SHao Luo static int cgroup_iter_seq_show(struct seq_file *seq, void *v)
148d4ccaf58SHao Luo {
149d4ccaf58SHao Luo return __cgroup_iter_seq_show(seq, (struct cgroup_subsys_state *)v,
150d4ccaf58SHao Luo false);
151d4ccaf58SHao Luo }
152d4ccaf58SHao Luo
153d4ccaf58SHao Luo static const struct seq_operations cgroup_iter_seq_ops = {
154d4ccaf58SHao Luo .start = cgroup_iter_seq_start,
155d4ccaf58SHao Luo .next = cgroup_iter_seq_next,
156d4ccaf58SHao Luo .stop = cgroup_iter_seq_stop,
157d4ccaf58SHao Luo .show = cgroup_iter_seq_show,
158d4ccaf58SHao Luo };
159d4ccaf58SHao Luo
BTF_ID_LIST_GLOBAL_SINGLE(bpf_cgroup_btf_id,struct,cgroup)1605e67b8efSYonghong Song BTF_ID_LIST_GLOBAL_SINGLE(bpf_cgroup_btf_id, struct, cgroup)
161d4ccaf58SHao Luo
162d4ccaf58SHao Luo static int cgroup_iter_seq_init(void *priv, struct bpf_iter_aux_info *aux)
163d4ccaf58SHao Luo {
164d4ccaf58SHao Luo struct cgroup_iter_priv *p = (struct cgroup_iter_priv *)priv;
165d4ccaf58SHao Luo struct cgroup *cgrp = aux->cgroup.start;
166d4ccaf58SHao Luo
1671a5160d4SHou Tao /* bpf_iter_attach_cgroup() has already acquired an extra reference
1681a5160d4SHou Tao * for the start cgroup, but the reference may be released after
1691a5160d4SHou Tao * cgroup_iter_seq_init(), so acquire another reference for the
1701a5160d4SHou Tao * start cgroup.
1711a5160d4SHou Tao */
172d4ccaf58SHao Luo p->start_css = &cgrp->self;
1731a5160d4SHou Tao css_get(p->start_css);
174d4ccaf58SHao Luo p->terminate = false;
175d4ccaf58SHao Luo p->visited_all = false;
176d4ccaf58SHao Luo p->order = aux->cgroup.order;
177d4ccaf58SHao Luo return 0;
178d4ccaf58SHao Luo }
179d4ccaf58SHao Luo
cgroup_iter_seq_fini(void * priv)1801a5160d4SHou Tao static void cgroup_iter_seq_fini(void *priv)
1811a5160d4SHou Tao {
1821a5160d4SHou Tao struct cgroup_iter_priv *p = (struct cgroup_iter_priv *)priv;
1831a5160d4SHou Tao
1841a5160d4SHou Tao css_put(p->start_css);
1851a5160d4SHou Tao }
1861a5160d4SHou Tao
187d4ccaf58SHao Luo static const struct bpf_iter_seq_info cgroup_iter_seq_info = {
188d4ccaf58SHao Luo .seq_ops = &cgroup_iter_seq_ops,
189d4ccaf58SHao Luo .init_seq_private = cgroup_iter_seq_init,
1901a5160d4SHou Tao .fini_seq_private = cgroup_iter_seq_fini,
191d4ccaf58SHao Luo .seq_priv_size = sizeof(struct cgroup_iter_priv),
192d4ccaf58SHao Luo };
193d4ccaf58SHao Luo
bpf_iter_attach_cgroup(struct bpf_prog * prog,union bpf_iter_link_info * linfo,struct bpf_iter_aux_info * aux)194d4ccaf58SHao Luo static int bpf_iter_attach_cgroup(struct bpf_prog *prog,
195d4ccaf58SHao Luo union bpf_iter_link_info *linfo,
196d4ccaf58SHao Luo struct bpf_iter_aux_info *aux)
197d4ccaf58SHao Luo {
198d4ccaf58SHao Luo int fd = linfo->cgroup.cgroup_fd;
199d4ccaf58SHao Luo u64 id = linfo->cgroup.cgroup_id;
200d4ccaf58SHao Luo int order = linfo->cgroup.order;
201d4ccaf58SHao Luo struct cgroup *cgrp;
202d4ccaf58SHao Luo
203d4ffb6f3SHao Luo if (order != BPF_CGROUP_ITER_DESCENDANTS_PRE &&
204d4ffb6f3SHao Luo order != BPF_CGROUP_ITER_DESCENDANTS_POST &&
205d4ffb6f3SHao Luo order != BPF_CGROUP_ITER_ANCESTORS_UP &&
206d4ffb6f3SHao Luo order != BPF_CGROUP_ITER_SELF_ONLY)
207d4ccaf58SHao Luo return -EINVAL;
208d4ccaf58SHao Luo
209d4ccaf58SHao Luo if (fd && id)
210d4ccaf58SHao Luo return -EINVAL;
211d4ccaf58SHao Luo
212d4ccaf58SHao Luo if (fd)
21335256d67SYosry Ahmed cgrp = cgroup_v1v2_get_from_fd(fd);
214d4ccaf58SHao Luo else if (id)
215d4ccaf58SHao Luo cgrp = cgroup_get_from_id(id);
216d4ccaf58SHao Luo else /* walk the entire hierarchy by default. */
217d4ccaf58SHao Luo cgrp = cgroup_get_from_path("/");
218d4ccaf58SHao Luo
219d4ccaf58SHao Luo if (IS_ERR(cgrp))
220d4ccaf58SHao Luo return PTR_ERR(cgrp);
221d4ccaf58SHao Luo
222d4ccaf58SHao Luo aux->cgroup.start = cgrp;
223d4ccaf58SHao Luo aux->cgroup.order = order;
224d4ccaf58SHao Luo return 0;
225d4ccaf58SHao Luo }
226d4ccaf58SHao Luo
bpf_iter_detach_cgroup(struct bpf_iter_aux_info * aux)227d4ccaf58SHao Luo static void bpf_iter_detach_cgroup(struct bpf_iter_aux_info *aux)
228d4ccaf58SHao Luo {
229d4ccaf58SHao Luo cgroup_put(aux->cgroup.start);
230d4ccaf58SHao Luo }
231d4ccaf58SHao Luo
bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info * aux,struct seq_file * seq)232d4ccaf58SHao Luo static void bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info *aux,
233d4ccaf58SHao Luo struct seq_file *seq)
234d4ccaf58SHao Luo {
235d4ccaf58SHao Luo char *buf;
236d4ccaf58SHao Luo
237d4ccaf58SHao Luo buf = kzalloc(PATH_MAX, GFP_KERNEL);
238d4ccaf58SHao Luo if (!buf) {
239d4ccaf58SHao Luo seq_puts(seq, "cgroup_path:\t<unknown>\n");
240d4ccaf58SHao Luo goto show_order;
241d4ccaf58SHao Luo }
242d4ccaf58SHao Luo
243d4ccaf58SHao Luo /* If cgroup_path_ns() fails, buf will be an empty string, cgroup_path
244d4ccaf58SHao Luo * will print nothing.
245d4ccaf58SHao Luo *
246d4ccaf58SHao Luo * Path is in the calling process's cgroup namespace.
247d4ccaf58SHao Luo */
248d4ccaf58SHao Luo cgroup_path_ns(aux->cgroup.start, buf, PATH_MAX,
249d4ccaf58SHao Luo current->nsproxy->cgroup_ns);
250d4ccaf58SHao Luo seq_printf(seq, "cgroup_path:\t%s\n", buf);
251d4ccaf58SHao Luo kfree(buf);
252d4ccaf58SHao Luo
253d4ccaf58SHao Luo show_order:
254d4ffb6f3SHao Luo if (aux->cgroup.order == BPF_CGROUP_ITER_DESCENDANTS_PRE)
255d4ccaf58SHao Luo seq_puts(seq, "order: descendants_pre\n");
256d4ffb6f3SHao Luo else if (aux->cgroup.order == BPF_CGROUP_ITER_DESCENDANTS_POST)
257d4ccaf58SHao Luo seq_puts(seq, "order: descendants_post\n");
258d4ffb6f3SHao Luo else if (aux->cgroup.order == BPF_CGROUP_ITER_ANCESTORS_UP)
259d4ccaf58SHao Luo seq_puts(seq, "order: ancestors_up\n");
260d4ffb6f3SHao Luo else /* BPF_CGROUP_ITER_SELF_ONLY */
261d4ccaf58SHao Luo seq_puts(seq, "order: self_only\n");
262d4ccaf58SHao Luo }
263d4ccaf58SHao Luo
bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info * aux,struct bpf_link_info * info)264d4ccaf58SHao Luo static int bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info *aux,
265d4ccaf58SHao Luo struct bpf_link_info *info)
266d4ccaf58SHao Luo {
267d4ccaf58SHao Luo info->iter.cgroup.order = aux->cgroup.order;
268d4ccaf58SHao Luo info->iter.cgroup.cgroup_id = cgroup_id(aux->cgroup.start);
269d4ccaf58SHao Luo return 0;
270d4ccaf58SHao Luo }
271d4ccaf58SHao Luo
272d4ccaf58SHao Luo DEFINE_BPF_ITER_FUNC(cgroup, struct bpf_iter_meta *meta,
273d4ccaf58SHao Luo struct cgroup *cgroup)
274d4ccaf58SHao Luo
275d4ccaf58SHao Luo static struct bpf_iter_reg bpf_cgroup_reg_info = {
276d4ccaf58SHao Luo .target = "cgroup",
277d4ccaf58SHao Luo .feature = BPF_ITER_RESCHED,
278d4ccaf58SHao Luo .attach_target = bpf_iter_attach_cgroup,
279d4ccaf58SHao Luo .detach_target = bpf_iter_detach_cgroup,
280d4ccaf58SHao Luo .show_fdinfo = bpf_iter_cgroup_show_fdinfo,
281d4ccaf58SHao Luo .fill_link_info = bpf_iter_cgroup_fill_link_info,
282d4ccaf58SHao Luo .ctx_arg_info_size = 1,
283d4ccaf58SHao Luo .ctx_arg_info = {
284d4ccaf58SHao Luo { offsetof(struct bpf_iter__cgroup, cgroup),
285d4ccaf58SHao Luo PTR_TO_BTF_ID_OR_NULL },
286d4ccaf58SHao Luo },
287d4ccaf58SHao Luo .seq_info = &cgroup_iter_seq_info,
288d4ccaf58SHao Luo };
289d4ccaf58SHao Luo
bpf_cgroup_iter_init(void)290d4ccaf58SHao Luo static int __init bpf_cgroup_iter_init(void)
291d4ccaf58SHao Luo {
292d4ccaf58SHao Luo bpf_cgroup_reg_info.ctx_arg_info[0].btf_id = bpf_cgroup_btf_id[0];
293d4ccaf58SHao Luo return bpf_iter_reg_target(&bpf_cgroup_reg_info);
294d4ccaf58SHao Luo }
295d4ccaf58SHao Luo
296d4ccaf58SHao Luo late_initcall(bpf_cgroup_iter_init);
297