kernel/bpf/bpf_cgrp_storage.c

   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_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_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_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 };