1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2020 Facebook 4 * Copyright 2020 Google LLC. 5 */ 6 7 #include <linux/pid.h> 8 #include <linux/sched.h> 9 #include <linux/rculist.h> 10 #include <linux/list.h> 11 #include <linux/hash.h> 12 #include <linux/types.h> 13 #include <linux/spinlock.h> 14 #include <linux/bpf.h> 15 #include <linux/bpf_local_storage.h> 16 #include <linux/filter.h> 17 #include <uapi/linux/btf.h> 18 #include <linux/btf_ids.h> 19 #include <linux/fdtable.h> 20 #include <linux/rcupdate_trace.h> 21 22 DEFINE_BPF_STORAGE_CACHE(task_cache); 23 24 static DEFINE_PER_CPU(int, bpf_task_storage_busy); 25 26 static void bpf_task_storage_lock(void) 27 { 28 migrate_disable(); 29 this_cpu_inc(bpf_task_storage_busy); 30 } 31 32 static void bpf_task_storage_unlock(void) 33 { 34 this_cpu_dec(bpf_task_storage_busy); 35 migrate_enable(); 36 } 37 38 static bool bpf_task_storage_trylock(void) 39 { 40 migrate_disable(); 41 if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) { 42 this_cpu_dec(bpf_task_storage_busy); 43 migrate_enable(); 44 return false; 45 } 46 return true; 47 } 48 49 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner) 50 { 51 struct task_struct *task = owner; 52 53 return &task->bpf_storage; 54 } 55 56 static struct bpf_local_storage_data * 57 task_storage_lookup(struct task_struct *task, struct bpf_map *map, 58 bool cacheit_lockit) 59 { 60 struct bpf_local_storage *task_storage; 61 struct bpf_local_storage_map *smap; 62 63 task_storage = 64 rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held()); 65 if (!task_storage) 66 return NULL; 67 68 smap = (struct bpf_local_storage_map *)map; 69 return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit); 70 } 71 72 void bpf_task_storage_free(struct task_struct *task) 73 { 74 struct bpf_local_storage *local_storage; 75 76 rcu_read_lock(); 77 78 local_storage = rcu_dereference(task->bpf_storage); 79 if (!local_storage) { 80 rcu_read_unlock(); 81 return; 82 } 83 84 bpf_task_storage_lock(); 85 bpf_local_storage_destroy(local_storage); 86 bpf_task_storage_unlock(); 87 rcu_read_unlock(); 88 } 89 90 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) 91 { 92 struct bpf_local_storage_data *sdata; 93 struct task_struct *task; 94 unsigned int f_flags; 95 struct pid *pid; 96 int fd, err; 97 98 fd = *(int *)key; 99 pid = pidfd_get_pid(fd, &f_flags); 100 if (IS_ERR(pid)) 101 return ERR_CAST(pid); 102 103 /* We should be in an RCU read side critical section, it should be safe 104 * to call pid_task. 105 */ 106 WARN_ON_ONCE(!rcu_read_lock_held()); 107 task = pid_task(pid, PIDTYPE_PID); 108 if (!task) { 109 err = -ENOENT; 110 goto out; 111 } 112 113 bpf_task_storage_lock(); 114 sdata = task_storage_lookup(task, map, true); 115 bpf_task_storage_unlock(); 116 put_pid(pid); 117 return sdata ? sdata->data : NULL; 118 out: 119 put_pid(pid); 120 return ERR_PTR(err); 121 } 122 123 static long bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key, 124 void *value, u64 map_flags) 125 { 126 struct bpf_local_storage_data *sdata; 127 struct task_struct *task; 128 unsigned int f_flags; 129 struct pid *pid; 130 int fd, err; 131 132 if ((map_flags & BPF_F_LOCK) && btf_record_has_field(map->record, BPF_UPTR)) 133 return -EOPNOTSUPP; 134 135 fd = *(int *)key; 136 pid = pidfd_get_pid(fd, &f_flags); 137 if (IS_ERR(pid)) 138 return PTR_ERR(pid); 139 140 /* We should be in an RCU read side critical section, it should be safe 141 * to call pid_task. 142 */ 143 WARN_ON_ONCE(!rcu_read_lock_held()); 144 task = pid_task(pid, PIDTYPE_PID); 145 if (!task) { 146 err = -ENOENT; 147 goto out; 148 } 149 150 bpf_task_storage_lock(); 151 sdata = bpf_local_storage_update( 152 task, (struct bpf_local_storage_map *)map, value, map_flags, 153 true, GFP_ATOMIC); 154 bpf_task_storage_unlock(); 155 156 err = PTR_ERR_OR_ZERO(sdata); 157 out: 158 put_pid(pid); 159 return err; 160 } 161 162 static int task_storage_delete(struct task_struct *task, struct bpf_map *map, 163 bool nobusy) 164 { 165 struct bpf_local_storage_data *sdata; 166 167 sdata = task_storage_lookup(task, map, false); 168 if (!sdata) 169 return -ENOENT; 170 171 if (!nobusy) 172 return -EBUSY; 173 174 bpf_selem_unlink(SELEM(sdata), false); 175 176 return 0; 177 } 178 179 static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) 180 { 181 struct task_struct *task; 182 unsigned int f_flags; 183 struct pid *pid; 184 int fd, err; 185 186 fd = *(int *)key; 187 pid = pidfd_get_pid(fd, &f_flags); 188 if (IS_ERR(pid)) 189 return PTR_ERR(pid); 190 191 /* We should be in an RCU read side critical section, it should be safe 192 * to call pid_task. 193 */ 194 WARN_ON_ONCE(!rcu_read_lock_held()); 195 task = pid_task(pid, PIDTYPE_PID); 196 if (!task) { 197 err = -ENOENT; 198 goto out; 199 } 200 201 bpf_task_storage_lock(); 202 err = task_storage_delete(task, map, true); 203 bpf_task_storage_unlock(); 204 out: 205 put_pid(pid); 206 return err; 207 } 208 209 /* Called by bpf_task_storage_get*() helpers */ 210 static void *__bpf_task_storage_get(struct bpf_map *map, 211 struct task_struct *task, void *value, 212 u64 flags, gfp_t gfp_flags, bool nobusy) 213 { 214 struct bpf_local_storage_data *sdata; 215 216 sdata = task_storage_lookup(task, map, nobusy); 217 if (sdata) 218 return sdata->data; 219 220 /* only allocate new storage, when the task is refcounted */ 221 if (refcount_read(&task->usage) && 222 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) { 223 sdata = bpf_local_storage_update( 224 task, (struct bpf_local_storage_map *)map, value, 225 BPF_NOEXIST, false, gfp_flags); 226 return IS_ERR(sdata) ? NULL : sdata->data; 227 } 228 229 return NULL; 230 } 231 232 /* *gfp_flags* is a hidden argument provided by the verifier */ 233 BPF_CALL_5(bpf_task_storage_get_recur, struct bpf_map *, map, struct task_struct *, 234 task, void *, value, u64, flags, gfp_t, gfp_flags) 235 { 236 bool nobusy; 237 void *data; 238 239 WARN_ON_ONCE(!bpf_rcu_lock_held()); 240 if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) 241 return (unsigned long)NULL; 242 243 nobusy = bpf_task_storage_trylock(); 244 data = __bpf_task_storage_get(map, task, value, flags, 245 gfp_flags, nobusy); 246 if (nobusy) 247 bpf_task_storage_unlock(); 248 return (unsigned long)data; 249 } 250 251 /* *gfp_flags* is a hidden argument provided by the verifier */ 252 BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, 253 task, void *, value, u64, flags, gfp_t, gfp_flags) 254 { 255 void *data; 256 257 WARN_ON_ONCE(!bpf_rcu_lock_held()); 258 if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) 259 return (unsigned long)NULL; 260 261 bpf_task_storage_lock(); 262 data = __bpf_task_storage_get(map, task, value, flags, 263 gfp_flags, true); 264 bpf_task_storage_unlock(); 265 return (unsigned long)data; 266 } 267 268 BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *, 269 task) 270 { 271 bool nobusy; 272 int ret; 273 274 WARN_ON_ONCE(!bpf_rcu_lock_held()); 275 if (!task) 276 return -EINVAL; 277 278 nobusy = bpf_task_storage_trylock(); 279 /* This helper must only be called from places where the lifetime of the task 280 * is guaranteed. Either by being refcounted or by being protected 281 * by an RCU read-side critical section. 282 */ 283 ret = task_storage_delete(task, map, nobusy); 284 if (nobusy) 285 bpf_task_storage_unlock(); 286 return ret; 287 } 288 289 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, 290 task) 291 { 292 int ret; 293 294 WARN_ON_ONCE(!bpf_rcu_lock_held()); 295 if (!task) 296 return -EINVAL; 297 298 bpf_task_storage_lock(); 299 /* This helper must only be called from places where the lifetime of the task 300 * is guaranteed. Either by being refcounted or by being protected 301 * by an RCU read-side critical section. 302 */ 303 ret = task_storage_delete(task, map, true); 304 bpf_task_storage_unlock(); 305 return ret; 306 } 307 308 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key) 309 { 310 return -ENOTSUPP; 311 } 312 313 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) 314 { 315 return bpf_local_storage_map_alloc(attr, &task_cache, true); 316 } 317 318 static void task_storage_map_free(struct bpf_map *map) 319 { 320 bpf_local_storage_map_free(map, &task_cache, &bpf_task_storage_busy); 321 } 322 323 BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map) 324 const struct bpf_map_ops task_storage_map_ops = { 325 .map_meta_equal = bpf_map_meta_equal, 326 .map_alloc_check = bpf_local_storage_map_alloc_check, 327 .map_alloc = task_storage_map_alloc, 328 .map_free = task_storage_map_free, 329 .map_get_next_key = notsupp_get_next_key, 330 .map_lookup_elem = bpf_pid_task_storage_lookup_elem, 331 .map_update_elem = bpf_pid_task_storage_update_elem, 332 .map_delete_elem = bpf_pid_task_storage_delete_elem, 333 .map_check_btf = bpf_local_storage_map_check_btf, 334 .map_mem_usage = bpf_local_storage_map_mem_usage, 335 .map_btf_id = &bpf_local_storage_map_btf_id[0], 336 .map_owner_storage_ptr = task_storage_ptr, 337 }; 338 339 const struct bpf_func_proto bpf_task_storage_get_recur_proto = { 340 .func = bpf_task_storage_get_recur, 341 .gpl_only = false, 342 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 343 .arg1_type = ARG_CONST_MAP_PTR, 344 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 345 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 346 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 347 .arg4_type = ARG_ANYTHING, 348 }; 349 350 const struct bpf_func_proto bpf_task_storage_get_proto = { 351 .func = bpf_task_storage_get, 352 .gpl_only = false, 353 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 354 .arg1_type = ARG_CONST_MAP_PTR, 355 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 356 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 357 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 358 .arg4_type = ARG_ANYTHING, 359 }; 360 361 const struct bpf_func_proto bpf_task_storage_delete_recur_proto = { 362 .func = bpf_task_storage_delete_recur, 363 .gpl_only = false, 364 .ret_type = RET_INTEGER, 365 .arg1_type = ARG_CONST_MAP_PTR, 366 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 367 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 368 }; 369 370 const struct bpf_func_proto bpf_task_storage_delete_proto = { 371 .func = bpf_task_storage_delete, 372 .gpl_only = false, 373 .ret_type = RET_INTEGER, 374 .arg1_type = ARG_CONST_MAP_PTR, 375 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 376 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 377 }; 378