1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
  4 */
  5
  6#include <linux/types.h>
  7#include <linux/bpf.h>
  8#include <linux/bpf_local_storage.h>
  9#include <uapi/linux/btf.h>
 10#include <linux/btf_ids.h>
 11
 12DEFINE_BPF_STORAGE_CACHE(cgroup_cache);
 13
 14static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy);
 15
 16static void bpf_cgrp_storage_lock(void)
 17{
 18	migrate_disable();
 19	this_cpu_inc(bpf_cgrp_storage_busy);
 20}
 21
 22static void bpf_cgrp_storage_unlock(void)
 23{
 24	this_cpu_dec(bpf_cgrp_storage_busy);
 25	migrate_enable();
 26}
 27
 28static bool bpf_cgrp_storage_trylock(void)
 29{
 30	migrate_disable();
 31	if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) {
 32		this_cpu_dec(bpf_cgrp_storage_busy);
 33		migrate_enable();
 34		return false;
 35	}
 36	return true;
 37}
 38
 39static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner)
 40{
 41	struct cgroup *cg = owner;
 42
 43	return &cg->bpf_cgrp_storage;
 44}
 45
 46void bpf_cgrp_storage_free(struct cgroup *cgroup)
 47{
 48	struct bpf_local_storage *local_storage;
 49	bool free_cgroup_storage = false;
 50	unsigned long flags;
 51
 52	rcu_read_lock();
 53	local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
 54	if (!local_storage) {
 55		rcu_read_unlock();
 56		return;
 57	}
 58
 59	bpf_cgrp_storage_lock();
 60	raw_spin_lock_irqsave(&local_storage->lock, flags);
 61	free_cgroup_storage = bpf_local_storage_unlink_nolock(local_storage);
 62	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 63	bpf_cgrp_storage_unlock();
 64	rcu_read_unlock();
 65
 66	if (free_cgroup_storage)
 67		kfree_rcu(local_storage, rcu);
 68}
 69
 70static struct bpf_local_storage_data *
 71cgroup_storage_lookup(struct cgroup *cgroup, struct bpf_map *map, bool cacheit_lockit)
 72{
 73	struct bpf_local_storage *cgroup_storage;
 74	struct bpf_local_storage_map *smap;
 75
 76	cgroup_storage = rcu_dereference_check(cgroup->bpf_cgrp_storage,
 77					       bpf_rcu_lock_held());
 78	if (!cgroup_storage)
 79		return NULL;
 80
 81	smap = (struct bpf_local_storage_map *)map;
 82	return bpf_local_storage_lookup(cgroup_storage, smap, cacheit_lockit);
 83}
 84
 85static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key)
 86{
 87	struct bpf_local_storage_data *sdata;
 88	struct cgroup *cgroup;
 89	int fd;
 90
 91	fd = *(int *)key;
 92	cgroup = cgroup_get_from_fd(fd);
 93	if (IS_ERR(cgroup))
 94		return ERR_CAST(cgroup);
 95
 96	bpf_cgrp_storage_lock();
 97	sdata = cgroup_storage_lookup(cgroup, map, true);
 98	bpf_cgrp_storage_unlock();
 99	cgroup_put(cgroup);
100	return sdata ? sdata->data : NULL;
101}
102
103static int bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,
104					  void *value, u64 map_flags)
105{
106	struct bpf_local_storage_data *sdata;
107	struct cgroup *cgroup;
108	int fd;
109
110	fd = *(int *)key;
111	cgroup = cgroup_get_from_fd(fd);
112	if (IS_ERR(cgroup))
113		return PTR_ERR(cgroup);
114
115	bpf_cgrp_storage_lock();
116	sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
117					 value, map_flags, GFP_ATOMIC);
118	bpf_cgrp_storage_unlock();
119	cgroup_put(cgroup);
120	return PTR_ERR_OR_ZERO(sdata);
121}
122
123static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map)
124{
125	struct bpf_local_storage_data *sdata;
126
127	sdata = cgroup_storage_lookup(cgroup, map, false);
128	if (!sdata)
129		return -ENOENT;
130
131	bpf_selem_unlink(SELEM(sdata), true);
132	return 0;
133}
134
135static int bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)
136{
137	struct cgroup *cgroup;
138	int err, fd;
139
140	fd = *(int *)key;
141	cgroup = cgroup_get_from_fd(fd);
142	if (IS_ERR(cgroup))
143		return PTR_ERR(cgroup);
144
145	bpf_cgrp_storage_lock();
146	err = cgroup_storage_delete(cgroup, map);
147	bpf_cgrp_storage_unlock();
148	cgroup_put(cgroup);
149	return err;
150}
151
152static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
153{
154	return -ENOTSUPP;
155}
156
157static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
158{
159	return bpf_local_storage_map_alloc(attr, &cgroup_cache);
160}
161
162static void cgroup_storage_map_free(struct bpf_map *map)
163{
164	bpf_local_storage_map_free(map, &cgroup_cache, NULL);
165}
166
167/* *gfp_flags* is a hidden argument provided by the verifier */
168BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup,
169	   void *, value, u64, flags, gfp_t, gfp_flags)
170{
171	struct bpf_local_storage_data *sdata;
172
173	WARN_ON_ONCE(!bpf_rcu_lock_held());
174	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
175		return (unsigned long)NULL;
176
177	if (!cgroup)
178		return (unsigned long)NULL;
179
180	if (!bpf_cgrp_storage_trylock())
181		return (unsigned long)NULL;
182
183	sdata = cgroup_storage_lookup(cgroup, map, true);
184	if (sdata)
185		goto unlock;
186
187	/* only allocate new storage, when the cgroup is refcounted */
188	if (!percpu_ref_is_dying(&cgroup->self.refcnt) &&
189	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
190		sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
191						 value, BPF_NOEXIST, gfp_flags);
192
193unlock:
194	bpf_cgrp_storage_unlock();
195	return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data;
196}
197
198BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup)
199{
200	int ret;
201
202	WARN_ON_ONCE(!bpf_rcu_lock_held());
203	if (!cgroup)
204		return -EINVAL;
205
206	if (!bpf_cgrp_storage_trylock())
207		return -EBUSY;
208
209	ret = cgroup_storage_delete(cgroup, map);
210	bpf_cgrp_storage_unlock();
211	return ret;
212}
213
214const struct bpf_map_ops cgrp_storage_map_ops = {
215	.map_meta_equal = bpf_map_meta_equal,
216	.map_alloc_check = bpf_local_storage_map_alloc_check,
217	.map_alloc = cgroup_storage_map_alloc,
218	.map_free = cgroup_storage_map_free,
219	.map_get_next_key = notsupp_get_next_key,
220	.map_lookup_elem = bpf_cgrp_storage_lookup_elem,
221	.map_update_elem = bpf_cgrp_storage_update_elem,
222	.map_delete_elem = bpf_cgrp_storage_delete_elem,
223	.map_check_btf = bpf_local_storage_map_check_btf,
224	.map_btf_id = &bpf_local_storage_map_btf_id[0],
225	.map_owner_storage_ptr = cgroup_storage_ptr,
226};
227
228const struct bpf_func_proto bpf_cgrp_storage_get_proto = {
229	.func		= bpf_cgrp_storage_get,
230	.gpl_only	= false,
231	.ret_type	= RET_PTR_TO_MAP_VALUE_OR_NULL,
232	.arg1_type	= ARG_CONST_MAP_PTR,
233	.arg2_type	= ARG_PTR_TO_BTF_ID,
234	.arg2_btf_id	= &bpf_cgroup_btf_id[0],
235	.arg3_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,
236	.arg4_type	= ARG_ANYTHING,
237};
238
239const struct bpf_func_proto bpf_cgrp_storage_delete_proto = {
240	.func		= bpf_cgrp_storage_delete,
241	.gpl_only	= false,
242	.ret_type	= RET_INTEGER,
243	.arg1_type	= ARG_CONST_MAP_PTR,
244	.arg2_type	= ARG_PTR_TO_BTF_ID,
245	.arg2_btf_id	= &bpf_cgroup_btf_id[0],
246};