xref: /openbmc/linux/kernel/bpf/queue_stack_maps.c (revision abe9af53)
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 
16 struct 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 
25 static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
26 {
27 	return container_of(map, struct bpf_queue_stack, map);
28 }
29 
30 static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
31 {
32 	return qs->head == qs->tail;
33 }
34 
35 static 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 */
46 static 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 
67 static 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 */
100 static 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 
107 static 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 
130 out:
131 	raw_spin_unlock_irqrestore(&qs->lock, flags);
132 	return err;
133 }
134 
135 
136 static 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 
162 out:
163 	raw_spin_unlock_irqrestore(&qs->lock, flags);
164 	return err;
165 }
166 
167 /* Called from syscall or from eBPF program */
168 static 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 */
174 static 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 */
180 static 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 */
186 static 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 */
192 static 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 
227 out:
228 	raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
229 	return err;
230 }
231 
232 /* Called from syscall or from eBPF program */
233 static 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 */
239 static 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 */
246 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
247 {
248 	return -EINVAL;
249 }
250 
251 /* Called from syscall */
252 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
253 					void *next_key)
254 {
255 	return -EINVAL;
256 }
257 
258 static int queue_map_btf_id;
259 const struct bpf_map_ops queue_map_ops = {
260 	.map_meta_equal = bpf_map_meta_equal,
261 	.map_alloc_check = queue_stack_map_alloc_check,
262 	.map_alloc = queue_stack_map_alloc,
263 	.map_free = queue_stack_map_free,
264 	.map_lookup_elem = queue_stack_map_lookup_elem,
265 	.map_update_elem = queue_stack_map_update_elem,
266 	.map_delete_elem = queue_stack_map_delete_elem,
267 	.map_push_elem = queue_stack_map_push_elem,
268 	.map_pop_elem = queue_map_pop_elem,
269 	.map_peek_elem = queue_map_peek_elem,
270 	.map_get_next_key = queue_stack_map_get_next_key,
271 	.map_btf_name = "bpf_queue_stack",
272 	.map_btf_id = &queue_map_btf_id,
273 };
274 
275 static int stack_map_btf_id;
276 const struct bpf_map_ops stack_map_ops = {
277 	.map_meta_equal = bpf_map_meta_equal,
278 	.map_alloc_check = queue_stack_map_alloc_check,
279 	.map_alloc = queue_stack_map_alloc,
280 	.map_free = queue_stack_map_free,
281 	.map_lookup_elem = queue_stack_map_lookup_elem,
282 	.map_update_elem = queue_stack_map_update_elem,
283 	.map_delete_elem = queue_stack_map_delete_elem,
284 	.map_push_elem = queue_stack_map_push_elem,
285 	.map_pop_elem = stack_map_pop_elem,
286 	.map_peek_elem = stack_map_peek_elem,
287 	.map_get_next_key = queue_stack_map_get_next_key,
288 	.map_btf_name = "bpf_queue_stack",
289 	.map_btf_id = &stack_map_btf_id,
290 };
291