xref: /openbmc/linux/kernel/bpf/bpf_cgrp_storage.c (revision 91571a51)
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 
bpf_cgrp_storage_lock(void)16 static void bpf_cgrp_storage_lock(void)
17 {
18 	migrate_disable();
19 	this_cpu_inc(bpf_cgrp_storage_busy);
20 }
21 
bpf_cgrp_storage_unlock(void)22 static void bpf_cgrp_storage_unlock(void)
23 {
24 	this_cpu_dec(bpf_cgrp_storage_busy);
25 	migrate_enable();
26 }
27 
bpf_cgrp_storage_trylock(void)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 
cgroup_storage_ptr(void * owner)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 
bpf_cgrp_storage_free(struct cgroup * cgroup)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 *
cgroup_storage_lookup(struct cgroup * cgroup,struct bpf_map * map,bool cacheit_lockit)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 
bpf_cgrp_storage_lookup_elem(struct bpf_map * map,void * key)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_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 
bpf_cgrp_storage_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)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_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 
cgroup_storage_delete(struct cgroup * cgroup,struct bpf_map * map)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 
bpf_cgrp_storage_delete_elem(struct bpf_map * map,void * key)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_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 
notsupp_get_next_key(struct bpf_map * map,void * key,void * next_key)145 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
146 {
147 	return -ENOTSUPP;
148 }
149 
cgroup_storage_map_alloc(union bpf_attr * attr)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 
cgroup_storage_map_free(struct bpf_map * map)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 */
BPF_CALL_5(bpf_cgrp_storage_get,struct bpf_map *,map,struct cgroup *,cgroup,void *,value,u64,flags,gfp_t,gfp_flags)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 
BPF_CALL_2(bpf_cgrp_storage_delete,struct bpf_map *,map,struct cgroup *,cgroup)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