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 fd = *(int *)key; 133 pid = pidfd_get_pid(fd, &f_flags); 134 if (IS_ERR(pid)) 135 return PTR_ERR(pid); 136 137 /* We should be in an RCU read side critical section, it should be safe 138 * to call pid_task. 139 */ 140 WARN_ON_ONCE(!rcu_read_lock_held()); 141 task = pid_task(pid, PIDTYPE_PID); 142 if (!task) { 143 err = -ENOENT; 144 goto out; 145 } 146 147 bpf_task_storage_lock(); 148 sdata = bpf_local_storage_update( 149 task, (struct bpf_local_storage_map *)map, value, map_flags, 150 GFP_ATOMIC); 151 bpf_task_storage_unlock(); 152 153 err = PTR_ERR_OR_ZERO(sdata); 154 out: 155 put_pid(pid); 156 return err; 157 } 158 159 static int task_storage_delete(struct task_struct *task, struct bpf_map *map, 160 bool nobusy) 161 { 162 struct bpf_local_storage_data *sdata; 163 164 sdata = task_storage_lookup(task, map, false); 165 if (!sdata) 166 return -ENOENT; 167 168 if (!nobusy) 169 return -EBUSY; 170 171 bpf_selem_unlink(SELEM(sdata), false); 172 173 return 0; 174 } 175 176 static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) 177 { 178 struct task_struct *task; 179 unsigned int f_flags; 180 struct pid *pid; 181 int fd, err; 182 183 fd = *(int *)key; 184 pid = pidfd_get_pid(fd, &f_flags); 185 if (IS_ERR(pid)) 186 return PTR_ERR(pid); 187 188 /* We should be in an RCU read side critical section, it should be safe 189 * to call pid_task. 190 */ 191 WARN_ON_ONCE(!rcu_read_lock_held()); 192 task = pid_task(pid, PIDTYPE_PID); 193 if (!task) { 194 err = -ENOENT; 195 goto out; 196 } 197 198 bpf_task_storage_lock(); 199 err = task_storage_delete(task, map, true); 200 bpf_task_storage_unlock(); 201 out: 202 put_pid(pid); 203 return err; 204 } 205 206 /* Called by bpf_task_storage_get*() helpers */ 207 static void *__bpf_task_storage_get(struct bpf_map *map, 208 struct task_struct *task, void *value, 209 u64 flags, gfp_t gfp_flags, bool nobusy) 210 { 211 struct bpf_local_storage_data *sdata; 212 213 sdata = task_storage_lookup(task, map, nobusy); 214 if (sdata) 215 return sdata->data; 216 217 /* only allocate new storage, when the task is refcounted */ 218 if (refcount_read(&task->usage) && 219 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) { 220 sdata = bpf_local_storage_update( 221 task, (struct bpf_local_storage_map *)map, value, 222 BPF_NOEXIST, gfp_flags); 223 return IS_ERR(sdata) ? NULL : sdata->data; 224 } 225 226 return NULL; 227 } 228 229 /* *gfp_flags* is a hidden argument provided by the verifier */ 230 BPF_CALL_5(bpf_task_storage_get_recur, struct bpf_map *, map, struct task_struct *, 231 task, void *, value, u64, flags, gfp_t, gfp_flags) 232 { 233 bool nobusy; 234 void *data; 235 236 WARN_ON_ONCE(!bpf_rcu_lock_held()); 237 if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) 238 return (unsigned long)NULL; 239 240 nobusy = bpf_task_storage_trylock(); 241 data = __bpf_task_storage_get(map, task, value, flags, 242 gfp_flags, nobusy); 243 if (nobusy) 244 bpf_task_storage_unlock(); 245 return (unsigned long)data; 246 } 247 248 /* *gfp_flags* is a hidden argument provided by the verifier */ 249 BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, 250 task, void *, value, u64, flags, gfp_t, gfp_flags) 251 { 252 void *data; 253 254 WARN_ON_ONCE(!bpf_rcu_lock_held()); 255 if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) 256 return (unsigned long)NULL; 257 258 bpf_task_storage_lock(); 259 data = __bpf_task_storage_get(map, task, value, flags, 260 gfp_flags, true); 261 bpf_task_storage_unlock(); 262 return (unsigned long)data; 263 } 264 265 BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *, 266 task) 267 { 268 bool nobusy; 269 int ret; 270 271 WARN_ON_ONCE(!bpf_rcu_lock_held()); 272 if (!task) 273 return -EINVAL; 274 275 nobusy = bpf_task_storage_trylock(); 276 /* This helper must only be called from places where the lifetime of the task 277 * is guaranteed. Either by being refcounted or by being protected 278 * by an RCU read-side critical section. 279 */ 280 ret = task_storage_delete(task, map, nobusy); 281 if (nobusy) 282 bpf_task_storage_unlock(); 283 return ret; 284 } 285 286 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, 287 task) 288 { 289 int ret; 290 291 WARN_ON_ONCE(!bpf_rcu_lock_held()); 292 if (!task) 293 return -EINVAL; 294 295 bpf_task_storage_lock(); 296 /* This helper must only be called from places where the lifetime of the task 297 * is guaranteed. Either by being refcounted or by being protected 298 * by an RCU read-side critical section. 299 */ 300 ret = task_storage_delete(task, map, true); 301 bpf_task_storage_unlock(); 302 return ret; 303 } 304 305 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key) 306 { 307 return -ENOTSUPP; 308 } 309 310 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) 311 { 312 return bpf_local_storage_map_alloc(attr, &task_cache, true); 313 } 314 315 static void task_storage_map_free(struct bpf_map *map) 316 { 317 bpf_local_storage_map_free(map, &task_cache, &bpf_task_storage_busy); 318 } 319 320 BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map) 321 const struct bpf_map_ops task_storage_map_ops = { 322 .map_meta_equal = bpf_map_meta_equal, 323 .map_alloc_check = bpf_local_storage_map_alloc_check, 324 .map_alloc = task_storage_map_alloc, 325 .map_free = task_storage_map_free, 326 .map_get_next_key = notsupp_get_next_key, 327 .map_lookup_elem = bpf_pid_task_storage_lookup_elem, 328 .map_update_elem = bpf_pid_task_storage_update_elem, 329 .map_delete_elem = bpf_pid_task_storage_delete_elem, 330 .map_check_btf = bpf_local_storage_map_check_btf, 331 .map_mem_usage = bpf_local_storage_map_mem_usage, 332 .map_btf_id = &bpf_local_storage_map_btf_id[0], 333 .map_owner_storage_ptr = task_storage_ptr, 334 }; 335 336 const struct bpf_func_proto bpf_task_storage_get_recur_proto = { 337 .func = bpf_task_storage_get_recur, 338 .gpl_only = false, 339 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 340 .arg1_type = ARG_CONST_MAP_PTR, 341 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 342 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 343 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 344 .arg4_type = ARG_ANYTHING, 345 }; 346 347 const struct bpf_func_proto bpf_task_storage_get_proto = { 348 .func = bpf_task_storage_get, 349 .gpl_only = false, 350 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, 351 .arg1_type = ARG_CONST_MAP_PTR, 352 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 353 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 354 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, 355 .arg4_type = ARG_ANYTHING, 356 }; 357 358 const struct bpf_func_proto bpf_task_storage_delete_recur_proto = { 359 .func = bpf_task_storage_delete_recur, 360 .gpl_only = false, 361 .ret_type = RET_INTEGER, 362 .arg1_type = ARG_CONST_MAP_PTR, 363 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 364 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 365 }; 366 367 const struct bpf_func_proto bpf_task_storage_delete_proto = { 368 .func = bpf_task_storage_delete, 369 .gpl_only = false, 370 .ret_type = RET_INTEGER, 371 .arg1_type = ARG_CONST_MAP_PTR, 372 .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, 373 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], 374 }; 375