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