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
12 DEFINE_BPF_STORAGE_CACHE(cgroup_cache);
13
14 static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy);
15
16 static void bpf_cgrp_storage_lock(void)
17 {
18 migrate_disable();
19 this_cpu_inc(bpf_cgrp_storage_busy);
20 }
21
22 static void bpf_cgrp_storage_unlock(void)
23 {
24 this_cpu_dec(bpf_cgrp_storage_busy);
25 migrate_enable();
26 }
27
28 static 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
39 static 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
46 void bpf_cgrp_storage_free(struct cgroup *cgroup)
47 {
48 struct bpf_local_storage *local_storage;
49
50 rcu_read_lock();
51 local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
52 if (!local_storage) {
53 rcu_read_unlock();
54 return;
55 }
56
57 bpf_cgrp_storage_lock();
58 bpf_local_storage_destroy(local_storage);
59 bpf_cgrp_storage_unlock();
60 rcu_read_unlock();
61 }
62
63 static struct bpf_local_storage_data *
64 cgroup_storage_lookup(struct cgroup *cgroup, struct bpf_map *map, bool cacheit_lockit)
65 {
66 struct bpf_local_storage *cgroup_storage;
67 struct bpf_local_storage_map *smap;
68
69 cgroup_storage = rcu_dereference_check(cgroup->bpf_cgrp_storage,
70 bpf_rcu_lock_held());
71 if (!cgroup_storage)
72 return NULL;
73
74 smap = (struct bpf_local_storage_map *)map;
75 return bpf_local_storage_lookup(cgroup_storage, smap, cacheit_lockit);
76 }
77
78 static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key)
79 {
80 struct bpf_local_storage_data *sdata;
81 struct cgroup *cgroup;
82 int fd;
83
84 fd = *(int *)key;
85 cgroup = cgroup_v1v2_get_from_fd(fd);
86 if (IS_ERR(cgroup))
87 return ERR_CAST(cgroup);
88
89 bpf_cgrp_storage_lock();
90 sdata = cgroup_storage_lookup(cgroup, map, true);
91 bpf_cgrp_storage_unlock();
92 cgroup_put(cgroup);
93 return sdata ? sdata->data : NULL;
94 }
95
96 static long bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,
97 void *value, u64 map_flags)
98 {
99 struct bpf_local_storage_data *sdata;
100 struct cgroup *cgroup;
101 int fd;
102
103 fd = *(int *)key;
104 cgroup = cgroup_v1v2_get_from_fd(fd);
105 if (IS_ERR(cgroup))
106 return PTR_ERR(cgroup);
107
108 bpf_cgrp_storage_lock();
109 sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
110 value, map_flags, GFP_ATOMIC);
111 bpf_cgrp_storage_unlock();
112 cgroup_put(cgroup);
113 return PTR_ERR_OR_ZERO(sdata);
114 }
115
116 static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map)
117 {
118 struct bpf_local_storage_data *sdata;
119
120 sdata = cgroup_storage_lookup(cgroup, map, false);
121 if (!sdata)
122 return -ENOENT;
123
124 bpf_selem_unlink(SELEM(sdata), false);
125 return 0;
126 }
127
128 static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)
129 {
130 struct cgroup *cgroup;
131 int err, fd;
132
133 fd = *(int *)key;
134 cgroup = cgroup_v1v2_get_from_fd(fd);
135 if (IS_ERR(cgroup))
136 return PTR_ERR(cgroup);
137
138 bpf_cgrp_storage_lock();
139 err = cgroup_storage_delete(cgroup, map);
140 bpf_cgrp_storage_unlock();
141 cgroup_put(cgroup);
142 return err;
143 }
144
145 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
146 {
147 return -ENOTSUPP;
148 }
149
150 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
151 {
152 return bpf_local_storage_map_alloc(attr, &cgroup_cache, true);
153 }
154
155 static void cgroup_storage_map_free(struct bpf_map *map)
156 {
157 bpf_local_storage_map_free(map, &cgroup_cache, NULL);
158 }
159
160 /* *gfp_flags* is a hidden argument provided by the verifier */
161 BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup,
162 void *, value, u64, flags, gfp_t, gfp_flags)
163 {
164 struct bpf_local_storage_data *sdata;
165
166 WARN_ON_ONCE(!bpf_rcu_lock_held());
167 if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
168 return (unsigned long)NULL;
169
170 if (!cgroup)
171 return (unsigned long)NULL;
172
173 if (!bpf_cgrp_storage_trylock())
174 return (unsigned long)NULL;
175
176 sdata = cgroup_storage_lookup(cgroup, map, true);
177 if (sdata)
178 goto unlock;
179
180 /* only allocate new storage, when the cgroup is refcounted */
181 if (!percpu_ref_is_dying(&cgroup->self.refcnt) &&
182 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
183 sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
184 value, BPF_NOEXIST, gfp_flags);
185
186 unlock:
187 bpf_cgrp_storage_unlock();
188 return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data;
189 }
190
191 BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup)
192 {
193 int ret;
194
195 WARN_ON_ONCE(!bpf_rcu_lock_held());
196 if (!cgroup)
197 return -EINVAL;
198
199 if (!bpf_cgrp_storage_trylock())
200 return -EBUSY;
201
202 ret = cgroup_storage_delete(cgroup, map);
203 bpf_cgrp_storage_unlock();
204 return ret;
205 }
206
207 const struct bpf_map_ops cgrp_storage_map_ops = {
208 .map_meta_equal = bpf_map_meta_equal,
209 .map_alloc_check = bpf_local_storage_map_alloc_check,
210 .map_alloc = cgroup_storage_map_alloc,
211 .map_free = cgroup_storage_map_free,
212 .map_get_next_key = notsupp_get_next_key,
213 .map_lookup_elem = bpf_cgrp_storage_lookup_elem,
214 .map_update_elem = bpf_cgrp_storage_update_elem,
215 .map_delete_elem = bpf_cgrp_storage_delete_elem,
216 .map_check_btf = bpf_local_storage_map_check_btf,
217 .map_mem_usage = bpf_local_storage_map_mem_usage,
218 .map_btf_id = &bpf_local_storage_map_btf_id[0],
219 .map_owner_storage_ptr = cgroup_storage_ptr,
220 };
221
222 const struct bpf_func_proto bpf_cgrp_storage_get_proto = {
223 .func = bpf_cgrp_storage_get,
224 .gpl_only = false,
225 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
226 .arg1_type = ARG_CONST_MAP_PTR,
227 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL,
228 .arg2_btf_id = &bpf_cgroup_btf_id[0],
229 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
230 .arg4_type = ARG_ANYTHING,
231 };
232
233 const struct bpf_func_proto bpf_cgrp_storage_delete_proto = {
234 .func = bpf_cgrp_storage_delete,
235 .gpl_only = false,
236 .ret_type = RET_INTEGER,
237 .arg1_type = ARG_CONST_MAP_PTR,
238 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL,
239 .arg2_btf_id = &bpf_cgroup_btf_id[0],
240 };
241
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.