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 /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0, 105 * so the programs (can be more than one that used this map) were 106 * disconnected from events. Wait for outstanding critical sections in 107 * these programs to complete 108 */ 109 synchronize_rcu(); 110 111 bpf_map_area_free(qs); 112 } 113 114 static int __queue_map_get(struct bpf_map *map, void *value, bool delete) 115 { 116 struct bpf_queue_stack *qs = bpf_queue_stack(map); 117 unsigned long flags; 118 int err = 0; 119 void *ptr; 120 121 raw_spin_lock_irqsave(&qs->lock, flags); 122 123 if (queue_stack_map_is_empty(qs)) { 124 memset(value, 0, qs->map.value_size); 125 err = -ENOENT; 126 goto out; 127 } 128 129 ptr = &qs->elements[qs->tail * qs->map.value_size]; 130 memcpy(value, ptr, qs->map.value_size); 131 132 if (delete) { 133 if (unlikely(++qs->tail >= qs->size)) 134 qs->tail = 0; 135 } 136 137 out: 138 raw_spin_unlock_irqrestore(&qs->lock, flags); 139 return err; 140 } 141 142 143 static int __stack_map_get(struct bpf_map *map, void *value, bool delete) 144 { 145 struct bpf_queue_stack *qs = bpf_queue_stack(map); 146 unsigned long flags; 147 int err = 0; 148 void *ptr; 149 u32 index; 150 151 raw_spin_lock_irqsave(&qs->lock, flags); 152 153 if (queue_stack_map_is_empty(qs)) { 154 memset(value, 0, qs->map.value_size); 155 err = -ENOENT; 156 goto out; 157 } 158 159 index = qs->head - 1; 160 if (unlikely(index >= qs->size)) 161 index = qs->size - 1; 162 163 ptr = &qs->elements[index * qs->map.value_size]; 164 memcpy(value, ptr, qs->map.value_size); 165 166 if (delete) 167 qs->head = index; 168 169 out: 170 raw_spin_unlock_irqrestore(&qs->lock, flags); 171 return err; 172 } 173 174 /* Called from syscall or from eBPF program */ 175 static int queue_map_peek_elem(struct bpf_map *map, void *value) 176 { 177 return __queue_map_get(map, value, false); 178 } 179 180 /* Called from syscall or from eBPF program */ 181 static int stack_map_peek_elem(struct bpf_map *map, void *value) 182 { 183 return __stack_map_get(map, value, false); 184 } 185 186 /* Called from syscall or from eBPF program */ 187 static int queue_map_pop_elem(struct bpf_map *map, void *value) 188 { 189 return __queue_map_get(map, value, true); 190 } 191 192 /* Called from syscall or from eBPF program */ 193 static int stack_map_pop_elem(struct bpf_map *map, void *value) 194 { 195 return __stack_map_get(map, value, true); 196 } 197 198 /* Called from syscall or from eBPF program */ 199 static int queue_stack_map_push_elem(struct bpf_map *map, void *value, 200 u64 flags) 201 { 202 struct bpf_queue_stack *qs = bpf_queue_stack(map); 203 unsigned long irq_flags; 204 int err = 0; 205 void *dst; 206 207 /* BPF_EXIST is used to force making room for a new element in case the 208 * map is full 209 */ 210 bool replace = (flags & BPF_EXIST); 211 212 /* Check supported flags for queue and stack maps */ 213 if (flags & BPF_NOEXIST || flags > BPF_EXIST) 214 return -EINVAL; 215 216 raw_spin_lock_irqsave(&qs->lock, irq_flags); 217 218 if (queue_stack_map_is_full(qs)) { 219 if (!replace) { 220 err = -E2BIG; 221 goto out; 222 } 223 /* advance tail pointer to overwrite oldest element */ 224 if (unlikely(++qs->tail >= qs->size)) 225 qs->tail = 0; 226 } 227 228 dst = &qs->elements[qs->head * qs->map.value_size]; 229 memcpy(dst, value, qs->map.value_size); 230 231 if (unlikely(++qs->head >= qs->size)) 232 qs->head = 0; 233 234 out: 235 raw_spin_unlock_irqrestore(&qs->lock, irq_flags); 236 return err; 237 } 238 239 /* Called from syscall or from eBPF program */ 240 static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key) 241 { 242 return NULL; 243 } 244 245 /* Called from syscall or from eBPF program */ 246 static int queue_stack_map_update_elem(struct bpf_map *map, void *key, 247 void *value, u64 flags) 248 { 249 return -EINVAL; 250 } 251 252 /* Called from syscall or from eBPF program */ 253 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key) 254 { 255 return -EINVAL; 256 } 257 258 /* Called from syscall */ 259 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key, 260 void *next_key) 261 { 262 return -EINVAL; 263 } 264 265 const struct bpf_map_ops queue_map_ops = { 266 .map_alloc_check = queue_stack_map_alloc_check, 267 .map_alloc = queue_stack_map_alloc, 268 .map_free = queue_stack_map_free, 269 .map_lookup_elem = queue_stack_map_lookup_elem, 270 .map_update_elem = queue_stack_map_update_elem, 271 .map_delete_elem = queue_stack_map_delete_elem, 272 .map_push_elem = queue_stack_map_push_elem, 273 .map_pop_elem = queue_map_pop_elem, 274 .map_peek_elem = queue_map_peek_elem, 275 .map_get_next_key = queue_stack_map_get_next_key, 276 }; 277 278 const struct bpf_map_ops stack_map_ops = { 279 .map_alloc_check = queue_stack_map_alloc_check, 280 .map_alloc = queue_stack_map_alloc, 281 .map_free = queue_stack_map_free, 282 .map_lookup_elem = queue_stack_map_lookup_elem, 283 .map_update_elem = queue_stack_map_update_elem, 284 .map_delete_elem = queue_stack_map_delete_elem, 285 .map_push_elem = queue_stack_map_push_elem, 286 .map_pop_elem = stack_map_pop_elem, 287 .map_peek_elem = stack_map_peek_elem, 288 .map_get_next_key = queue_stack_map_get_next_key, 289 }; 290