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[0] __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 (!capable(CAP_SYS_ADMIN)) 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 if (cost >= U32_MAX - PAGE_SIZE) 77 return ERR_PTR(-E2BIG); 78 79 cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 80 81 ret = bpf_map_charge_init(&mem, cost); 82 if (ret < 0) 83 return ERR_PTR(ret); 84 85 qs = bpf_map_area_alloc(queue_size, numa_node); 86 if (!qs) { 87 bpf_map_charge_finish(&mem); 88 return ERR_PTR(-ENOMEM); 89 } 90 91 memset(qs, 0, sizeof(*qs)); 92 93 bpf_map_init_from_attr(&qs->map, attr); 94 95 bpf_map_charge_move(&qs->map.memory, &mem); 96 qs->size = size; 97 98 raw_spin_lock_init(&qs->lock); 99 100 return &qs->map; 101 } 102 103 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ 104 static void queue_stack_map_free(struct bpf_map *map) 105 { 106 struct bpf_queue_stack *qs = bpf_queue_stack(map); 107 108 /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0, 109 * so the programs (can be more than one that used this map) were 110 * disconnected from events. Wait for outstanding critical sections in 111 * these programs to complete 112 */ 113 synchronize_rcu(); 114 115 bpf_map_area_free(qs); 116 } 117 118 static int __queue_map_get(struct bpf_map *map, void *value, bool delete) 119 { 120 struct bpf_queue_stack *qs = bpf_queue_stack(map); 121 unsigned long flags; 122 int err = 0; 123 void *ptr; 124 125 raw_spin_lock_irqsave(&qs->lock, flags); 126 127 if (queue_stack_map_is_empty(qs)) { 128 memset(value, 0, qs->map.value_size); 129 err = -ENOENT; 130 goto out; 131 } 132 133 ptr = &qs->elements[qs->tail * qs->map.value_size]; 134 memcpy(value, ptr, qs->map.value_size); 135 136 if (delete) { 137 if (unlikely(++qs->tail >= qs->size)) 138 qs->tail = 0; 139 } 140 141 out: 142 raw_spin_unlock_irqrestore(&qs->lock, flags); 143 return err; 144 } 145 146 147 static int __stack_map_get(struct bpf_map *map, void *value, bool delete) 148 { 149 struct bpf_queue_stack *qs = bpf_queue_stack(map); 150 unsigned long flags; 151 int err = 0; 152 void *ptr; 153 u32 index; 154 155 raw_spin_lock_irqsave(&qs->lock, flags); 156 157 if (queue_stack_map_is_empty(qs)) { 158 memset(value, 0, qs->map.value_size); 159 err = -ENOENT; 160 goto out; 161 } 162 163 index = qs->head - 1; 164 if (unlikely(index >= qs->size)) 165 index = qs->size - 1; 166 167 ptr = &qs->elements[index * qs->map.value_size]; 168 memcpy(value, ptr, qs->map.value_size); 169 170 if (delete) 171 qs->head = index; 172 173 out: 174 raw_spin_unlock_irqrestore(&qs->lock, flags); 175 return err; 176 } 177 178 /* Called from syscall or from eBPF program */ 179 static int queue_map_peek_elem(struct bpf_map *map, void *value) 180 { 181 return __queue_map_get(map, value, false); 182 } 183 184 /* Called from syscall or from eBPF program */ 185 static int stack_map_peek_elem(struct bpf_map *map, void *value) 186 { 187 return __stack_map_get(map, value, false); 188 } 189 190 /* Called from syscall or from eBPF program */ 191 static int queue_map_pop_elem(struct bpf_map *map, void *value) 192 { 193 return __queue_map_get(map, value, true); 194 } 195 196 /* Called from syscall or from eBPF program */ 197 static int stack_map_pop_elem(struct bpf_map *map, void *value) 198 { 199 return __stack_map_get(map, value, true); 200 } 201 202 /* Called from syscall or from eBPF program */ 203 static int queue_stack_map_push_elem(struct bpf_map *map, void *value, 204 u64 flags) 205 { 206 struct bpf_queue_stack *qs = bpf_queue_stack(map); 207 unsigned long irq_flags; 208 int err = 0; 209 void *dst; 210 211 /* BPF_EXIST is used to force making room for a new element in case the 212 * map is full 213 */ 214 bool replace = (flags & BPF_EXIST); 215 216 /* Check supported flags for queue and stack maps */ 217 if (flags & BPF_NOEXIST || flags > BPF_EXIST) 218 return -EINVAL; 219 220 raw_spin_lock_irqsave(&qs->lock, irq_flags); 221 222 if (queue_stack_map_is_full(qs)) { 223 if (!replace) { 224 err = -E2BIG; 225 goto out; 226 } 227 /* advance tail pointer to overwrite oldest element */ 228 if (unlikely(++qs->tail >= qs->size)) 229 qs->tail = 0; 230 } 231 232 dst = &qs->elements[qs->head * qs->map.value_size]; 233 memcpy(dst, value, qs->map.value_size); 234 235 if (unlikely(++qs->head >= qs->size)) 236 qs->head = 0; 237 238 out: 239 raw_spin_unlock_irqrestore(&qs->lock, irq_flags); 240 return err; 241 } 242 243 /* Called from syscall or from eBPF program */ 244 static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key) 245 { 246 return NULL; 247 } 248 249 /* Called from syscall or from eBPF program */ 250 static int queue_stack_map_update_elem(struct bpf_map *map, void *key, 251 void *value, u64 flags) 252 { 253 return -EINVAL; 254 } 255 256 /* Called from syscall or from eBPF program */ 257 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key) 258 { 259 return -EINVAL; 260 } 261 262 /* Called from syscall */ 263 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key, 264 void *next_key) 265 { 266 return -EINVAL; 267 } 268 269 const struct bpf_map_ops queue_map_ops = { 270 .map_alloc_check = queue_stack_map_alloc_check, 271 .map_alloc = queue_stack_map_alloc, 272 .map_free = queue_stack_map_free, 273 .map_lookup_elem = queue_stack_map_lookup_elem, 274 .map_update_elem = queue_stack_map_update_elem, 275 .map_delete_elem = queue_stack_map_delete_elem, 276 .map_push_elem = queue_stack_map_push_elem, 277 .map_pop_elem = queue_map_pop_elem, 278 .map_peek_elem = queue_map_peek_elem, 279 .map_get_next_key = queue_stack_map_get_next_key, 280 }; 281 282 const struct bpf_map_ops stack_map_ops = { 283 .map_alloc_check = queue_stack_map_alloc_check, 284 .map_alloc = queue_stack_map_alloc, 285 .map_free = queue_stack_map_free, 286 .map_lookup_elem = queue_stack_map_lookup_elem, 287 .map_update_elem = queue_stack_map_update_elem, 288 .map_delete_elem = queue_stack_map_delete_elem, 289 .map_push_elem = queue_stack_map_push_elem, 290 .map_pop_elem = stack_map_pop_elem, 291 .map_peek_elem = stack_map_peek_elem, 292 .map_get_next_key = queue_stack_map_get_next_key, 293 }; 294