bpf_task_storage.c

   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 };