// 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; cgroup_lock(); /* 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_CGROUP_ITER_DESCENDANTS_PRE) return css_next_descendant_pre(NULL, p->start_css); else if (p->order == BPF_CGROUP_ITER_DESCENDANTS_POST) return css_next_descendant_post(NULL, p->start_css); else /* BPF_CGROUP_ITER_SELF_ONLY and BPF_CGROUP_ITER_ANCESTORS_UP */ 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; cgroup_unlock(); /* 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_CGROUP_ITER_DESCENDANTS_PRE) return css_next_descendant_pre(curr, p->start_css); else if (p->order == BPF_CGROUP_ITER_DESCENDANTS_POST) return css_next_descendant_post(curr, p->start_css); else if (p->order == BPF_CGROUP_ITER_ANCESTORS_UP) return curr->parent; else /* BPF_CGROUP_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_GLOBAL_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; /* bpf_iter_attach_cgroup() has already acquired an extra reference * for the start cgroup, but the reference may be released after * cgroup_iter_seq_init(), so acquire another reference for the * start cgroup. */ p->start_css = &cgrp->self; css_get(p->start_css); p->terminate = false; p->visited_all = false; p->order = aux->cgroup.order; return 0; } static void cgroup_iter_seq_fini(void *priv) { struct cgroup_iter_priv *p = (struct cgroup_iter_priv *)priv; css_put(p->start_css); } static const struct bpf_iter_seq_info cgroup_iter_seq_info = { .seq_ops = &cgroup_iter_seq_ops, .init_seq_private = cgroup_iter_seq_init, .fini_seq_private = cgroup_iter_seq_fini, .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_CGROUP_ITER_DESCENDANTS_PRE && order != BPF_CGROUP_ITER_DESCENDANTS_POST && order != BPF_CGROUP_ITER_ANCESTORS_UP && order != BPF_CGROUP_ITER_SELF_ONLY) return -EINVAL; if (fd && id) return -EINVAL; if (fd) cgrp = cgroup_v1v2_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_CGROUP_ITER_DESCENDANTS_PRE) seq_puts(seq, "order: descendants_pre\n"); else if (aux->cgroup.order == BPF_CGROUP_ITER_DESCENDANTS_POST) seq_puts(seq, "order: descendants_post\n"); else if (aux->cgroup.order == BPF_CGROUP_ITER_ANCESTORS_UP) seq_puts(seq, "order: ancestors_up\n"); else /* BPF_CGROUP_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 | PTR_TRUSTED }, }, .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); struct bpf_iter_css { __u64 __opaque[3]; } __attribute__((aligned(8))); struct bpf_iter_css_kern { struct cgroup_subsys_state *start; struct cgroup_subsys_state *pos; unsigned int flags; } __attribute__((aligned(8))); __bpf_kfunc_start_defs(); __bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it, struct cgroup_subsys_state *start, unsigned int flags) { struct bpf_iter_css_kern *kit = (void *)it; BUILD_BUG_ON(sizeof(struct bpf_iter_css_kern) > sizeof(struct bpf_iter_css)); BUILD_BUG_ON(__alignof__(struct bpf_iter_css_kern) != __alignof__(struct bpf_iter_css)); kit->start = NULL; switch (flags) { case BPF_CGROUP_ITER_DESCENDANTS_PRE: case BPF_CGROUP_ITER_DESCENDANTS_POST: case BPF_CGROUP_ITER_ANCESTORS_UP: break; default: return -EINVAL; } kit->start = start; kit->pos = NULL; kit->flags = flags; return 0; } __bpf_kfunc struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) { struct bpf_iter_css_kern *kit = (void *)it; if (!kit->start) return NULL; switch (kit->flags) { case BPF_CGROUP_ITER_DESCENDANTS_PRE: kit->pos = css_next_descendant_pre(kit->pos, kit->start); break; case BPF_CGROUP_ITER_DESCENDANTS_POST: kit->pos = css_next_descendant_post(kit->pos, kit->start); break; case BPF_CGROUP_ITER_ANCESTORS_UP: kit->pos = kit->pos ? kit->pos->parent : kit->start; } return kit->pos; } __bpf_kfunc void bpf_iter_css_destroy(struct bpf_iter_css *it) { } __bpf_kfunc_end_defs();