// 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();