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 <linux/capability.h>
  11 #include <linux/btf_ids.h>
  12 #include "percpu_freelist.h"
  13
  14 #define QUEUE_STACK_CREATE_FLAG_MASK \
  15         (BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
  16
  17 struct 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[] __aligned(8);
  24 };
  25
  26 static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
  27 {
  28         return container_of(map, struct bpf_queue_stack, map);
  29 }
  30
  31 static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
  32 {
  33         return qs->head == qs->tail;
  34 }
  35
  36 static 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 */
  47 static int queue_stack_map_alloc_check(union bpf_attr *attr)
  48 {
  49         if (!bpf_capable())
  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             !bpf_map_flags_access_ok(attr->map_flags))
  57                 return -EINVAL;
  58
  59         if (attr->value_size > KMALLOC_MAX_SIZE)
  60                 /* if value_size is bigger, the user space won't be able to
  61                  * access the elements.
  62                  */
  63                 return -E2BIG;
  64
  65         return 0;
  66 }
  67
  68 static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
  69 {
  70         int numa_node = bpf_map_attr_numa_node(attr);
  71         struct bpf_queue_stack *qs;
  72         u64 size, queue_size;
  73
  74         size = (u64) attr->max_entries + 1;
  75         queue_size = sizeof(*qs) + size * attr->value_size;
  76
  77         qs = bpf_map_area_alloc(queue_size, numa_node);
  78         if (!qs)
  79                 return ERR_PTR(-ENOMEM);
  80
  81         memset(qs, 0, sizeof(*qs));
  82
  83         bpf_map_init_from_attr(&qs->map, attr);
  84
  85         qs->size = size;
  86
  87         raw_spin_lock_init(&qs->lock);
  88
  89         return &qs->map;
  90 }
  91
  92 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
  93 static void queue_stack_map_free(struct bpf_map *map)
  94 {
  95         struct bpf_queue_stack *qs = bpf_queue_stack(map);
  96
  97         bpf_map_area_free(qs);
  98 }
  99
 100 static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
 101 {
 102         struct bpf_queue_stack *qs = bpf_queue_stack(map);
 103         unsigned long flags;
 104         int err = 0;
 105         void *ptr;
 106
 107         raw_spin_lock_irqsave(&qs->lock, flags);
 108
 109         if (queue_stack_map_is_empty(qs)) {
 110                 memset(value, 0, qs->map.value_size);
 111                 err = -ENOENT;
 112                 goto out;
 113         }
 114
 115         ptr = &qs->elements[qs->tail * qs->map.value_size];
 116         memcpy(value, ptr, qs->map.value_size);
 117
 118         if (delete) {
 119                 if (unlikely(++qs->tail >= qs->size))
 120                         qs->tail = 0;
 121         }
 122
 123 out:
 124         raw_spin_unlock_irqrestore(&qs->lock, flags);
 125         return err;
 126 }
 127
 128
 129 static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
 130 {
 131         struct bpf_queue_stack *qs = bpf_queue_stack(map);
 132         unsigned long flags;
 133         int err = 0;
 134         void *ptr;
 135         u32 index;
 136
 137         raw_spin_lock_irqsave(&qs->lock, flags);
 138
 139         if (queue_stack_map_is_empty(qs)) {
 140                 memset(value, 0, qs->map.value_size);
 141                 err = -ENOENT;
 142                 goto out;
 143         }
 144
 145         index = qs->head - 1;
 146         if (unlikely(index >= qs->size))
 147                 index = qs->size - 1;
 148
 149         ptr = &qs->elements[index * qs->map.value_size];
 150         memcpy(value, ptr, qs->map.value_size);
 151
 152         if (delete)
 153                 qs->head = index;
 154
 155 out:
 156         raw_spin_unlock_irqrestore(&qs->lock, flags);
 157         return err;
 158 }
 159
 160 /* Called from syscall or from eBPF program */
 161 static int queue_map_peek_elem(struct bpf_map *map, void *value)
 162 {
 163         return __queue_map_get(map, value, false);
 164 }
 165
 166 /* Called from syscall or from eBPF program */
 167 static int stack_map_peek_elem(struct bpf_map *map, void *value)
 168 {
 169         return __stack_map_get(map, value, false);
 170 }
 171
 172 /* Called from syscall or from eBPF program */
 173 static int queue_map_pop_elem(struct bpf_map *map, void *value)
 174 {
 175         return __queue_map_get(map, value, true);
 176 }
 177
 178 /* Called from syscall or from eBPF program */
 179 static int stack_map_pop_elem(struct bpf_map *map, void *value)
 180 {
 181         return __stack_map_get(map, value, true);
 182 }
 183
 184 /* Called from syscall or from eBPF program */
 185 static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
 186                                      u64 flags)
 187 {
 188         struct bpf_queue_stack *qs = bpf_queue_stack(map);
 189         unsigned long irq_flags;
 190         int err = 0;
 191         void *dst;
 192
 193         /* BPF_EXIST is used to force making room for a new element in case the
 194          * map is full
 195          */
 196         bool replace = (flags & BPF_EXIST);
 197
 198         /* Check supported flags for queue and stack maps */
 199         if (flags & BPF_NOEXIST || flags > BPF_EXIST)
 200                 return -EINVAL;
 201
 202         raw_spin_lock_irqsave(&qs->lock, irq_flags);
 203
 204         if (queue_stack_map_is_full(qs)) {
 205                 if (!replace) {
 206                         err = -E2BIG;
 207                         goto out;
 208                 }
 209                 /* advance tail pointer to overwrite oldest element */
 210                 if (unlikely(++qs->tail >= qs->size))
 211                         qs->tail = 0;
 212         }
 213
 214         dst = &qs->elements[qs->head * qs->map.value_size];
 215         memcpy(dst, value, qs->map.value_size);
 216
 217         if (unlikely(++qs->head >= qs->size))
 218                 qs->head = 0;
 219
 220 out:
 221         raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
 222         return err;
 223 }
 224
 225 /* Called from syscall or from eBPF program */
 226 static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
 227 {
 228         return NULL;
 229 }
 230
 231 /* Called from syscall or from eBPF program */
 232 static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
 233                                        void *value, u64 flags)
 234 {
 235         return -EINVAL;
 236 }
 237
 238 /* Called from syscall or from eBPF program */
 239 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
 240 {
 241         return -EINVAL;
 242 }
 243
 244 /* Called from syscall */
 245 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
 246                                         void *next_key)
 247 {
 248         return -EINVAL;
 249 }
 250
 251 BTF_ID_LIST_SINGLE(queue_map_btf_ids, struct, bpf_queue_stack)
 252 const struct bpf_map_ops queue_map_ops = {
 253         .map_meta_equal = bpf_map_meta_equal,
 254         .map_alloc_check = queue_stack_map_alloc_check,
 255         .map_alloc = queue_stack_map_alloc,
 256         .map_free = queue_stack_map_free,
 257         .map_lookup_elem = queue_stack_map_lookup_elem,
 258         .map_update_elem = queue_stack_map_update_elem,
 259         .map_delete_elem = queue_stack_map_delete_elem,
 260         .map_push_elem = queue_stack_map_push_elem,
 261         .map_pop_elem = queue_map_pop_elem,
 262         .map_peek_elem = queue_map_peek_elem,
 263         .map_get_next_key = queue_stack_map_get_next_key,
 264         .map_btf_id = &queue_map_btf_ids[0],
 265 };
 266
 267 const struct bpf_map_ops stack_map_ops = {
 268         .map_meta_equal = bpf_map_meta_equal,
 269         .map_alloc_check = queue_stack_map_alloc_check,
 270         .map_alloc = queue_stack_map_alloc,
 271         .map_free = queue_stack_map_free,
 272         .map_lookup_elem = queue_stack_map_lookup_elem,
 273         .map_update_elem = queue_stack_map_update_elem,
 274         .map_delete_elem = queue_stack_map_delete_elem,
 275         .map_push_elem = queue_stack_map_push_elem,
 276         .map_pop_elem = stack_map_pop_elem,
 277         .map_peek_elem = stack_map_peek_elem,
 278         .map_get_next_key = queue_stack_map_get_next_key,
 279         .map_btf_id = &queue_map_btf_ids[0],
 280 };