projects/linux·blob eac61655 · refs

290 lines · 6.8 KiB

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_RDONLY | BPF_F_WRONLY)
15
16
17struct bpf_queue_stack {
18 struct bpf_map map;
19 raw_spinlock_t lock;
20 u32 head, tail;
21 u32 size; /* max_entries + 1 */
22
23 char elements[0] __aligned(8);
24};
25
26static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
27{
28 return container_of(map, struct bpf_queue_stack, map);
29}
30
31static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
32{
33 return qs->head == qs->tail;
34}
35
36static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
37{
38 u32 head = qs->head + 1;
39
40 if (unlikely(head >= qs->size))
41 head = 0;
42
43 return head == qs->tail;
44}
45
46/* Called from syscall */
47static int queue_stack_map_alloc_check(union bpf_attr *attr)
48{
49 if (!capable(CAP_SYS_ADMIN))
50 return -EPERM;
51
52 /* check sanity of attributes */
53 if (attr->max_entries == 0 || attr->key_size != 0 ||
54 attr->value_size == 0 ||
55 attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
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_queue_stack *qs;
71 u64 size, queue_size, cost;
72
73 size = (u64) attr->max_entries + 1;
74 cost = queue_size = sizeof(*qs) + size * attr->value_size;
75 if (cost >= U32_MAX - PAGE_SIZE)
76 return ERR_PTR(-E2BIG);
77
78 cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
79
80 ret = bpf_map_precharge_memlock(cost);
81 if (ret < 0)
82 return ERR_PTR(ret);
83
84 qs = bpf_map_area_alloc(queue_size, numa_node);
85 if (!qs)
86 return ERR_PTR(-ENOMEM);
87
88 memset(qs, 0, sizeof(*qs));
89
90 bpf_map_init_from_attr(&qs->map, attr);
91
92 qs->map.pages = cost;
93 qs->size = size;
94
95 raw_spin_lock_init(&qs->lock);
96
97 return &qs->map;
98}
99
100/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
101static void queue_stack_map_free(struct bpf_map *map)
102{
103 struct bpf_queue_stack *qs = bpf_queue_stack(map);
104
105 /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
106 * so the programs (can be more than one that used this map) were
107 * disconnected from events. Wait for outstanding critical sections in
108 * these programs to complete
109 */
110 synchronize_rcu();
111
112 bpf_map_area_free(qs);
113}
114
115static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
116{
117 struct bpf_queue_stack *qs = bpf_queue_stack(map);
118 unsigned long flags;
119 int err = 0;
120 void *ptr;
121
122 raw_spin_lock_irqsave(&qs->lock, flags);
123
124 if (queue_stack_map_is_empty(qs)) {
125 memset(value, 0, qs->map.value_size);
126 err = -ENOENT;
127 goto out;
128 }
129
130 ptr = &qs->elements[qs->tail * qs->map.value_size];
131 memcpy(value, ptr, qs->map.value_size);
132
133 if (delete) {
134 if (unlikely(++qs->tail >= qs->size))
135 qs->tail = 0;
136 }
137
138out:
139 raw_spin_unlock_irqrestore(&qs->lock, flags);
140 return err;
141}
142
143
144static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
145{
146 struct bpf_queue_stack *qs = bpf_queue_stack(map);
147 unsigned long flags;
148 int err = 0;
149 void *ptr;
150 u32 index;
151
152 raw_spin_lock_irqsave(&qs->lock, flags);
153
154 if (queue_stack_map_is_empty(qs)) {
155 memset(value, 0, qs->map.value_size);
156 err = -ENOENT;
157 goto out;
158 }
159
160 index = qs->head - 1;
161 if (unlikely(index >= qs->size))
162 index = qs->size - 1;
163
164 ptr = &qs->elements[index * qs->map.value_size];
165 memcpy(value, ptr, qs->map.value_size);
166
167 if (delete)
168 qs->head = index;
169
170out:
171 raw_spin_unlock_irqrestore(&qs->lock, flags);
172 return err;
173}
174
175/* Called from syscall or from eBPF program */
176static int queue_map_peek_elem(struct bpf_map *map, void *value)
177{
178 return __queue_map_get(map, value, false);
179}
180
181/* Called from syscall or from eBPF program */
182static int stack_map_peek_elem(struct bpf_map *map, void *value)
183{
184 return __stack_map_get(map, value, false);
185}
186
187/* Called from syscall or from eBPF program */
188static int queue_map_pop_elem(struct bpf_map *map, void *value)
189{
190 return __queue_map_get(map, value, true);
191}
192
193/* Called from syscall or from eBPF program */
194static int stack_map_pop_elem(struct bpf_map *map, void *value)
195{
196 return __stack_map_get(map, value, true);
197}
198
199/* Called from syscall or from eBPF program */
200static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
201 u64 flags)
202{
203 struct bpf_queue_stack *qs = bpf_queue_stack(map);
204 unsigned long irq_flags;
205 int err = 0;
206 void *dst;
207
208 /* BPF_EXIST is used to force making room for a new element in case the
209 * map is full
210 */
211 bool replace = (flags & BPF_EXIST);
212
213 /* Check supported flags for queue and stack maps */
214 if (flags & BPF_NOEXIST || flags > BPF_EXIST)
215 return -EINVAL;
216
217 raw_spin_lock_irqsave(&qs->lock, irq_flags);
218
219 if (queue_stack_map_is_full(qs)) {
220 if (!replace) {
221 err = -E2BIG;
222 goto out;
223 }
224 /* advance tail pointer to overwrite oldest element */
225 if (unlikely(++qs->tail >= qs->size))
226 qs->tail = 0;
227 }
228
229 dst = &qs->elements[qs->head * qs->map.value_size];
230 memcpy(dst, value, qs->map.value_size);
231
232 if (unlikely(++qs->head >= qs->size))
233 qs->head = 0;
234
235out:
236 raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
237 return err;
238}
239
240/* Called from syscall or from eBPF program */
241static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
242{
243 return NULL;
244}
245
246/* Called from syscall or from eBPF program */
247static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
248 void *value, u64 flags)
249{
250 return -EINVAL;
251}
252
253/* Called from syscall or from eBPF program */
254static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
255{
256 return -EINVAL;
257}
258
259/* Called from syscall */
260static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
261 void *next_key)
262{
263 return -EINVAL;
264}
265
266const struct bpf_map_ops queue_map_ops = {
267 .map_alloc_check = queue_stack_map_alloc_check,
268 .map_alloc = queue_stack_map_alloc,
269 .map_free = queue_stack_map_free,
270 .map_lookup_elem = queue_stack_map_lookup_elem,
271 .map_update_elem = queue_stack_map_update_elem,
272 .map_delete_elem = queue_stack_map_delete_elem,
273 .map_push_elem = queue_stack_map_push_elem,
274 .map_pop_elem = queue_map_pop_elem,
275 .map_peek_elem = queue_map_peek_elem,
276 .map_get_next_key = queue_stack_map_get_next_key,
277};
278
279const struct bpf_map_ops stack_map_ops = {
280 .map_alloc_check = queue_stack_map_alloc_check,
281 .map_alloc = queue_stack_map_alloc,
282 .map_free = queue_stack_map_free,
283 .map_lookup_elem = queue_stack_map_lookup_elem,
284 .map_update_elem = queue_stack_map_update_elem,
285 .map_delete_elem = queue_stack_map_delete_elem,
286 .map_push_elem = queue_stack_map_push_elem,
287 .map_pop_elem = stack_map_pop_elem,
288 .map_peek_elem = stack_map_peek_elem,
289 .map_get_next_key = queue_stack_map_get_next_key,
290};