1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * queue_stack_maps.c: BPF queue and stack maps
  4 *
  5 * Copyright (c) 2018 Politecnico di Torino
  6 */
  7#include <linux/bpf.h>
  8#include <linux/list.h>
  9#include <linux/slab.h>
 10#include <linux/capability.h>
 11#include "percpu_freelist.h"
 12
 13#define QUEUE_STACK_CREATE_FLAG_MASK \
 14	(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
 15
 16struct bpf_queue_stack {
 17	struct bpf_map map;
 18	raw_spinlock_t lock;
 19	u32 head, tail;
 20	u32 size; /* max_entries + 1 */
 21
 22	char elements[] __aligned(8);
 23};
 24
 25static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
 26{
 27	return container_of(map, struct bpf_queue_stack, map);
 28}
 29
 30static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
 31{
 32	return qs->head == qs->tail;
 33}
 34
 35static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
 36{
 37	u32 head = qs->head + 1;
 38
 39	if (unlikely(head >= qs->size))
 40		head = 0;
 41
 42	return head == qs->tail;
 43}
 44
 45/* Called from syscall */
 46static int queue_stack_map_alloc_check(union bpf_attr *attr)
 47{
 48	if (!bpf_capable())
 49		return -EPERM;
 50
 51	/* check sanity of attributes */
 52	if (attr->max_entries == 0 || attr->key_size != 0 ||
 53	    attr->value_size == 0 ||
 54	    attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK ||
 55	    !bpf_map_flags_access_ok(attr->map_flags))
 56		return -EINVAL;
 57
 58	if (attr->value_size > KMALLOC_MAX_SIZE)
 59		/* if value_size is bigger, the user space won't be able to
 60		 * access the elements.
 61		 */
 62		return -E2BIG;
 63
 64	return 0;
 65}
 66
 67static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
 68{
 69	int ret, numa_node = bpf_map_attr_numa_node(attr);
 70	struct bpf_map_memory mem = {0};
 71	struct bpf_queue_stack *qs;
 72	u64 size, queue_size, cost;
 73
 74	size = (u64) attr->max_entries + 1;
 75	cost = queue_size = sizeof(*qs) + size * attr->value_size;
 76
 77	ret = bpf_map_charge_init(&mem, cost);
 78	if (ret < 0)
 79		return ERR_PTR(ret);
 80
 81	qs = bpf_map_area_alloc(queue_size, numa_node);
 82	if (!qs) {
 83		bpf_map_charge_finish(&mem);
 84		return ERR_PTR(-ENOMEM);
 85	}
 86
 87	memset(qs, 0, sizeof(*qs));
 88
 89	bpf_map_init_from_attr(&qs->map, attr);
 90
 91	bpf_map_charge_move(&qs->map.memory, &mem);
 92	qs->size = size;
 93
 94	raw_spin_lock_init(&qs->lock);
 95
 96	return &qs->map;
 97}
 98
 99/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
100static void queue_stack_map_free(struct bpf_map *map)
101{
102	struct bpf_queue_stack *qs = bpf_queue_stack(map);
103
104	bpf_map_area_free(qs);
105}
106
107static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
108{
109	struct bpf_queue_stack *qs = bpf_queue_stack(map);
110	unsigned long flags;
111	int err = 0;
112	void *ptr;
113
114	raw_spin_lock_irqsave(&qs->lock, flags);
115
116	if (queue_stack_map_is_empty(qs)) {
117		memset(value, 0, qs->map.value_size);
118		err = -ENOENT;
119		goto out;
120	}
121
122	ptr = &qs->elements[qs->tail * qs->map.value_size];
123	memcpy(value, ptr, qs->map.value_size);
124
125	if (delete) {
126		if (unlikely(++qs->tail >= qs->size))
127			qs->tail = 0;
128	}
129
130out:
131	raw_spin_unlock_irqrestore(&qs->lock, flags);
132	return err;
133}
134
135
136static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
137{
138	struct bpf_queue_stack *qs = bpf_queue_stack(map);
139	unsigned long flags;
140	int err = 0;
141	void *ptr;
142	u32 index;
143
144	raw_spin_lock_irqsave(&qs->lock, flags);
145
146	if (queue_stack_map_is_empty(qs)) {
147		memset(value, 0, qs->map.value_size);
148		err = -ENOENT;
149		goto out;
150	}
151
152	index = qs->head - 1;
153	if (unlikely(index >= qs->size))
154		index = qs->size - 1;
155
156	ptr = &qs->elements[index * qs->map.value_size];
157	memcpy(value, ptr, qs->map.value_size);
158
159	if (delete)
160		qs->head = index;
161
162out:
163	raw_spin_unlock_irqrestore(&qs->lock, flags);
164	return err;
165}
166
167/* Called from syscall or from eBPF program */
168static int queue_map_peek_elem(struct bpf_map *map, void *value)
169{
170	return __queue_map_get(map, value, false);
171}
172
173/* Called from syscall or from eBPF program */
174static int stack_map_peek_elem(struct bpf_map *map, void *value)
175{
176	return __stack_map_get(map, value, false);
177}
178
179/* Called from syscall or from eBPF program */
180static int queue_map_pop_elem(struct bpf_map *map, void *value)
181{
182	return __queue_map_get(map, value, true);
183}
184
185/* Called from syscall or from eBPF program */
186static int stack_map_pop_elem(struct bpf_map *map, void *value)
187{
188	return __stack_map_get(map, value, true);
189}
190
191/* Called from syscall or from eBPF program */
192static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
193				     u64 flags)
194{
195	struct bpf_queue_stack *qs = bpf_queue_stack(map);
196	unsigned long irq_flags;
197	int err = 0;
198	void *dst;
199
200	/* BPF_EXIST is used to force making room for a new element in case the
201	 * map is full
202	 */
203	bool replace = (flags & BPF_EXIST);
204
205	/* Check supported flags for queue and stack maps */
206	if (flags & BPF_NOEXIST || flags > BPF_EXIST)
207		return -EINVAL;
208
209	raw_spin_lock_irqsave(&qs->lock, irq_flags);
210
211	if (queue_stack_map_is_full(qs)) {
212		if (!replace) {
213			err = -E2BIG;
214			goto out;
215		}
216		/* advance tail pointer to overwrite oldest element */
217		if (unlikely(++qs->tail >= qs->size))
218			qs->tail = 0;
219	}
220
221	dst = &qs->elements[qs->head * qs->map.value_size];
222	memcpy(dst, value, qs->map.value_size);
223
224	if (unlikely(++qs->head >= qs->size))
225		qs->head = 0;
226
227out:
228	raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
229	return err;
230}
231
232/* Called from syscall or from eBPF program */
233static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
234{
235	return NULL;
236}
237
238/* Called from syscall or from eBPF program */
239static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
240				       void *value, u64 flags)
241{
242	return -EINVAL;
243}
244
245/* Called from syscall or from eBPF program */
246static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
247{
248	return -EINVAL;
249}
250
251/* Called from syscall */
252static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
253					void *next_key)
254{
255	return -EINVAL;
256}
257
258static int queue_map_btf_id;
259const struct bpf_map_ops queue_map_ops = {
260	.map_alloc_check = queue_stack_map_alloc_check,
261	.map_alloc = queue_stack_map_alloc,
262	.map_free = queue_stack_map_free,
263	.map_lookup_elem = queue_stack_map_lookup_elem,
264	.map_update_elem = queue_stack_map_update_elem,
265	.map_delete_elem = queue_stack_map_delete_elem,
266	.map_push_elem = queue_stack_map_push_elem,
267	.map_pop_elem = queue_map_pop_elem,
268	.map_peek_elem = queue_map_peek_elem,
269	.map_get_next_key = queue_stack_map_get_next_key,
270	.map_btf_name = "bpf_queue_stack",
271	.map_btf_id = &queue_map_btf_id,
272};
273
274static int stack_map_btf_id;
275const struct bpf_map_ops stack_map_ops = {
276	.map_alloc_check = queue_stack_map_alloc_check,
277	.map_alloc = queue_stack_map_alloc,
278	.map_free = queue_stack_map_free,
279	.map_lookup_elem = queue_stack_map_lookup_elem,
280	.map_update_elem = queue_stack_map_update_elem,
281	.map_delete_elem = queue_stack_map_delete_elem,
282	.map_push_elem = queue_stack_map_push_elem,
283	.map_pop_elem = stack_map_pop_elem,
284	.map_peek_elem = stack_map_peek_elem,
285	.map_get_next_key = queue_stack_map_get_next_key,
286	.map_btf_name = "bpf_queue_stack",
287	.map_btf_id = &stack_map_btf_id,
288};