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
22DEFINE_BPF_STORAGE_CACHE(task_cache);
23
24static DEFINE_PER_CPU(int, bpf_task_storage_busy);
25
26static void bpf_task_storage_lock(void)
27{
28	migrate_disable();
29	this_cpu_inc(bpf_task_storage_busy);
30}
31
32static void bpf_task_storage_unlock(void)
33{
34	this_cpu_dec(bpf_task_storage_busy);
35	migrate_enable();
36}
37
38static 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
49static 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
56static struct bpf_local_storage_data *
57task_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
72void 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
90static 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;
118out:
119	put_pid(pid);
120	return ERR_PTR(err);
121}
122
123static 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);
154out:
155	put_pid(pid);
156	return err;
157}
158
159static 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
176static 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();
201out:
202	put_pid(pid);
203	return err;
204}
205
206/* Called by bpf_task_storage_get*() helpers */
207static 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 */
230BPF_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 */
249BPF_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
265BPF_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
286BPF_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
305static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
306{
307	return -ENOTSUPP;
308}
309
310static 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
315static 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
320BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map)
321const 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
336const 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
347const 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
358const 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
367const 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