git.rot13.org Git - linux/blob - kernel/bpf/queue_stack_maps.c

   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 "percpu_freelist.h"
  11
  12 #define QUEUE_STACK_CREATE_FLAG_MASK \
  13         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
  14
  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         /* check sanity of attributes */
  49         if (attr->max_entries == 0 || attr->key_size != 0 ||
  50             attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
  51                 return -EINVAL;
  52
  53         if (attr->value_size > KMALLOC_MAX_SIZE)
  54                 /* if value_size is bigger, the user space won't be able to
  55                  * access the elements.
  56                  */
  57                 return -E2BIG;
  58
  59         return 0;
  60 }
  61
  62 static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
  63 {
  64         int ret, numa_node = bpf_map_attr_numa_node(attr);
  65         struct bpf_queue_stack *qs;
  66         u32 size, value_size;
  67         u64 queue_size, cost;
  68
  69         size = attr->max_entries + 1;
  70         value_size = attr->value_size;
  71
  72         queue_size = sizeof(*qs) + (u64) value_size * size;
  73
  74         cost = queue_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 */
 101 static 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
 115 static 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                 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                 err = -ENOENT;
 155                 goto out;
 156         }
 157
 158         index = qs->head - 1;
 159         if (unlikely(index >= qs->size))
 160                 index = qs->size - 1;
 161
 162         ptr = &qs->elements[index * qs->map.value_size];
 163         memcpy(value, ptr, qs->map.value_size);
 164
 165         if (delete)
 166                 qs->head = index;
 167
 168 out:
 169         raw_spin_unlock_irqrestore(&qs->lock, flags);
 170         return err;
 171 }
 172
 173 /* Called from syscall or from eBPF program */
 174 static int queue_map_peek_elem(struct bpf_map *map, void *value)
 175 {
 176         return __queue_map_get(map, value, false);
 177 }
 178
 179 /* Called from syscall or from eBPF program */
 180 static int stack_map_peek_elem(struct bpf_map *map, void *value)
 181 {
 182         return __stack_map_get(map, value, false);
 183 }
 184
 185 /* Called from syscall or from eBPF program */
 186 static int queue_map_pop_elem(struct bpf_map *map, void *value)
 187 {
 188         return __queue_map_get(map, value, true);
 189 }
 190
 191 /* Called from syscall or from eBPF program */
 192 static int stack_map_pop_elem(struct bpf_map *map, void *value)
 193 {
 194         return __stack_map_get(map, value, true);
 195 }
 196
 197 /* Called from syscall or from eBPF program */
 198 static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
 199                                      u64 flags)
 200 {
 201         struct bpf_queue_stack *qs = bpf_queue_stack(map);
 202         unsigned long irq_flags;
 203         int err = 0;
 204         void *dst;
 205
 206         /* BPF_EXIST is used to force making room for a new element in case the
 207          * map is full
 208          */
 209         bool replace = (flags & BPF_EXIST);
 210
 211         /* Check supported flags for queue and stack maps */
 212         if (flags & BPF_NOEXIST || flags > BPF_EXIST)
 213                 return -EINVAL;
 214
 215         raw_spin_lock_irqsave(&qs->lock, irq_flags);
 216
 217         if (queue_stack_map_is_full(qs)) {
 218                 if (!replace) {
 219                         err = -E2BIG;
 220                         goto out;
 221                 }
 222                 /* advance tail pointer to overwrite oldest element */
 223                 if (unlikely(++qs->tail >= qs->size))
 224                         qs->tail = 0;
 225         }
 226
 227         dst = &qs->elements[qs->head * qs->map.value_size];
 228         memcpy(dst, value, qs->map.value_size);
 229
 230         if (unlikely(++qs->head >= qs->size))
 231                 qs->head = 0;
 232
 233 out:
 234         raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
 235         return err;
 236 }
 237
 238 /* Called from syscall or from eBPF program */
 239 static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
 240 {
 241         return NULL;
 242 }
 243
 244 /* Called from syscall or from eBPF program */
 245 static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
 246                                        void *value, u64 flags)
 247 {
 248         return -EINVAL;
 249 }
 250
 251 /* Called from syscall or from eBPF program */
 252 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
 253 {
 254         return -EINVAL;
 255 }
 256
 257 /* Called from syscall */
 258 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
 259                                         void *next_key)
 260 {
 261         return -EINVAL;
 262 }
 263
 264 const struct bpf_map_ops queue_map_ops = {
 265         .map_alloc_check = queue_stack_map_alloc_check,
 266         .map_alloc = queue_stack_map_alloc,
 267         .map_free = queue_stack_map_free,
 268         .map_lookup_elem = queue_stack_map_lookup_elem,
 269         .map_update_elem = queue_stack_map_update_elem,
 270         .map_delete_elem = queue_stack_map_delete_elem,
 271         .map_push_elem = queue_stack_map_push_elem,
 272         .map_pop_elem = queue_map_pop_elem,
 273         .map_peek_elem = queue_map_peek_elem,
 274         .map_get_next_key = queue_stack_map_get_next_key,
 275 };
 276
 277 const struct bpf_map_ops stack_map_ops = {
 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 };