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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376// SPDX-License-Identifier: GPL-2.0-only/* Copyright (c) 2022 Google */#include <linux/bpf.h>#include <linux/btf_ids.h>#include <linux/cgroup.h>#include <linux/kernel.h>#include <linux/seq_file.h>
#include "../cgroup/cgroup-internal.h" /* cgroup_mutex and cgroup_is_dead */
/* cgroup_iter provides five 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. * 5. Walk the children of a given parent cgroup. * * 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 if (p->order == BPF_CGROUP_ITER_CHILDREN) return css_next_child(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 if (p->order == BPF_CGROUP_ITER_CHILDREN) return css_next_child(curr, p->start_css); 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;
switch (order) { case BPF_CGROUP_ITER_DESCENDANTS_PRE: case BPF_CGROUP_ITER_DESCENDANTS_POST: case BPF_CGROUP_ITER_ANCESTORS_UP: case BPF_CGROUP_ITER_SELF_ONLY: case BPF_CGROUP_ITER_CHILDREN: break; default: 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<unknown>\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 if (aux->cgroup.order == BPF_CGROUP_ITER_CHILDREN) seq_puts(seq, "order: children\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: case BPF_CGROUP_ITER_CHILDREN: 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_CHILDREN: kit->pos = css_next_child(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();