1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2020 Facebook
4 * Copyright 2020 Google LLC.
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>
22 DEFINE_BPF_STORAGE_CACHE(task_cache);
24 static DEFINE_PER_CPU(int, bpf_task_storage_busy);
26 static void bpf_task_storage_lock(void)
29 __this_cpu_inc(bpf_task_storage_busy);
32 static void bpf_task_storage_unlock(void)
34 __this_cpu_dec(bpf_task_storage_busy);
38 static bool bpf_task_storage_trylock(void)
41 if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
42 __this_cpu_dec(bpf_task_storage_busy);
49 static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
51 struct task_struct *task = owner;
53 return &task->bpf_storage;
56 static struct bpf_local_storage_data *
57 task_storage_lookup(struct task_struct *task, struct bpf_map *map,
60 struct bpf_local_storage *task_storage;
61 struct bpf_local_storage_map *smap;
64 rcu_dereference_check(task->bpf_storage, bpf_rcu_lock_held());
68 smap = (struct bpf_local_storage_map *)map;
69 return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
72 void bpf_task_storage_free(struct task_struct *task)
74 struct bpf_local_storage_elem *selem;
75 struct bpf_local_storage *local_storage;
76 bool free_task_storage = false;
82 local_storage = rcu_dereference(task->bpf_storage);
88 /* Neither the bpf_prog nor the bpf-map's syscall
89 * could be modifying the local_storage->list now.
90 * Thus, no elem can be added-to or deleted-from the
91 * local_storage->list by the bpf_prog or by the bpf-map's syscall.
93 * It is racing with bpf_local_storage_map_free() alone
94 * when unlinking elem from the local_storage->list and
95 * the map's bucket->list.
97 bpf_task_storage_lock();
98 raw_spin_lock_irqsave(&local_storage->lock, flags);
99 hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
100 /* Always unlink from map before unlinking from
103 bpf_selem_unlink_map(selem);
104 free_task_storage = bpf_selem_unlink_storage_nolock(
105 local_storage, selem, false);
107 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
108 bpf_task_storage_unlock();
111 /* free_task_storage should always be true as long as
112 * local_storage->list was non-empty.
114 if (free_task_storage)
115 kfree_rcu(local_storage, rcu);
118 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
120 struct bpf_local_storage_data *sdata;
121 struct task_struct *task;
122 unsigned int f_flags;
127 pid = pidfd_get_pid(fd, &f_flags);
129 return ERR_CAST(pid);
131 /* We should be in an RCU read side critical section, it should be safe
134 WARN_ON_ONCE(!rcu_read_lock_held());
135 task = pid_task(pid, PIDTYPE_PID);
141 bpf_task_storage_lock();
142 sdata = task_storage_lookup(task, map, true);
143 bpf_task_storage_unlock();
145 return sdata ? sdata->data : NULL;
151 static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
152 void *value, u64 map_flags)
154 struct bpf_local_storage_data *sdata;
155 struct task_struct *task;
156 unsigned int f_flags;
161 pid = pidfd_get_pid(fd, &f_flags);
165 /* We should be in an RCU read side critical section, it should be safe
168 WARN_ON_ONCE(!rcu_read_lock_held());
169 task = pid_task(pid, PIDTYPE_PID);
175 bpf_task_storage_lock();
176 sdata = bpf_local_storage_update(
177 task, (struct bpf_local_storage_map *)map, value, map_flags);
178 bpf_task_storage_unlock();
180 err = PTR_ERR_OR_ZERO(sdata);
186 static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
188 struct bpf_local_storage_data *sdata;
190 sdata = task_storage_lookup(task, map, false);
194 bpf_selem_unlink(SELEM(sdata));
199 static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
201 struct task_struct *task;
202 unsigned int f_flags;
207 pid = pidfd_get_pid(fd, &f_flags);
211 /* We should be in an RCU read side critical section, it should be safe
214 WARN_ON_ONCE(!rcu_read_lock_held());
215 task = pid_task(pid, PIDTYPE_PID);
221 bpf_task_storage_lock();
222 err = task_storage_delete(task, map);
223 bpf_task_storage_unlock();
229 BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
230 task, void *, value, u64, flags)
232 struct bpf_local_storage_data *sdata;
234 WARN_ON_ONCE(!bpf_rcu_lock_held());
235 if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
236 return (unsigned long)NULL;
239 return (unsigned long)NULL;
241 if (!bpf_task_storage_trylock())
242 return (unsigned long)NULL;
244 sdata = task_storage_lookup(task, map, true);
248 /* only allocate new storage, when the task is refcounted */
249 if (refcount_read(&task->usage) &&
250 (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
251 sdata = bpf_local_storage_update(
252 task, (struct bpf_local_storage_map *)map, value,
256 bpf_task_storage_unlock();
257 return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL :
258 (unsigned long)sdata->data;
261 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
266 WARN_ON_ONCE(!bpf_rcu_lock_held());
270 if (!bpf_task_storage_trylock())
273 /* This helper must only be called from places where the lifetime of the task
274 * is guaranteed. Either by being refcounted or by being protected
275 * by an RCU read-side critical section.
277 ret = task_storage_delete(task, map);
278 bpf_task_storage_unlock();
282 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
287 static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
289 struct bpf_local_storage_map *smap;
291 smap = bpf_local_storage_map_alloc(attr);
293 return ERR_CAST(smap);
295 smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
299 static void task_storage_map_free(struct bpf_map *map)
301 struct bpf_local_storage_map *smap;
303 smap = (struct bpf_local_storage_map *)map;
304 bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
305 bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
308 static int task_storage_map_btf_id;
309 const struct bpf_map_ops task_storage_map_ops = {
310 .map_meta_equal = bpf_map_meta_equal,
311 .map_alloc_check = bpf_local_storage_map_alloc_check,
312 .map_alloc = task_storage_map_alloc,
313 .map_free = task_storage_map_free,
314 .map_get_next_key = notsupp_get_next_key,
315 .map_lookup_elem = bpf_pid_task_storage_lookup_elem,
316 .map_update_elem = bpf_pid_task_storage_update_elem,
317 .map_delete_elem = bpf_pid_task_storage_delete_elem,
318 .map_check_btf = bpf_local_storage_map_check_btf,
319 .map_btf_name = "bpf_local_storage_map",
320 .map_btf_id = &task_storage_map_btf_id,
321 .map_owner_storage_ptr = task_storage_ptr,
324 const struct bpf_func_proto bpf_task_storage_get_proto = {
325 .func = bpf_task_storage_get,
327 .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
328 .arg1_type = ARG_CONST_MAP_PTR,
329 .arg2_type = ARG_PTR_TO_BTF_ID,
330 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
331 .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
332 .arg4_type = ARG_ANYTHING,
335 const struct bpf_func_proto bpf_task_storage_delete_proto = {
336 .func = bpf_task_storage_delete,
338 .ret_type = RET_INTEGER,
339 .arg1_type = ARG_CONST_MAP_PTR,
340 .arg2_type = ARG_PTR_TO_BTF_ID,
341 .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],