kernel/bpf/map_in_map.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2017 Facebook
   3  */
   4 #include <linux/slab.h>
   5 #include <linux/bpf.h>
   6 #include <linux/btf.h>
   7
   8 #include "map_in_map.h"
   9
  10 struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
  11 {
  12         struct bpf_map *inner_map, *inner_map_meta;
  13         u32 inner_map_meta_size;
  14         CLASS(fd, f)(inner_map_ufd);
  15
  16         inner_map = __bpf_map_get(f);
  17         if (IS_ERR(inner_map))
  18                 return inner_map;
  19
  20         /* Does not support >1 level map-in-map */
  21         if (inner_map->inner_map_meta)
  22                 return ERR_PTR(-EINVAL);
  23
  24         if (!inner_map->ops->map_meta_equal)
  25                 return ERR_PTR(-ENOTSUPP);
  26
  27         inner_map_meta_size = sizeof(*inner_map_meta);
  28         /* In some cases verifier needs to access beyond just base map. */
  29         if (inner_map->ops == &array_map_ops || inner_map->ops == &percpu_array_map_ops)
  30                 inner_map_meta_size = sizeof(struct bpf_array);
  31
  32         inner_map_meta = kzalloc(inner_map_meta_size, GFP_USER);
  33         if (!inner_map_meta)
  34                 return ERR_PTR(-ENOMEM);
  35
  36         inner_map_meta->map_type = inner_map->map_type;
  37         inner_map_meta->key_size = inner_map->key_size;
  38         inner_map_meta->value_size = inner_map->value_size;
  39         inner_map_meta->map_flags = inner_map->map_flags;
  40         inner_map_meta->max_entries = inner_map->max_entries;
  41
  42         inner_map_meta->record = btf_record_dup(inner_map->record);
  43         if (IS_ERR(inner_map_meta->record)) {
  44                 /* btf_record_dup returns NULL or valid pointer in case of
  45                  * invalid/empty/valid, but ERR_PTR in case of errors. During
  46                  * equality NULL or IS_ERR is equivalent.
  47                  */
  48                 struct bpf_map *ret = ERR_CAST(inner_map_meta->record);
  49                 kfree(inner_map_meta);
  50                 return ret;
  51         }
  52         /* Note: We must use the same BTF, as we also used btf_record_dup above
  53          * which relies on BTF being same for both maps, as some members like
  54          * record->fields.list_head have pointers like value_rec pointing into
  55          * inner_map->btf.
  56          */
  57         if (inner_map->btf) {
  58                 btf_get(inner_map->btf);
  59                 inner_map_meta->btf = inner_map->btf;
  60         }
  61
  62         /* Misc members not needed in bpf_map_meta_equal() check. */
  63         inner_map_meta->ops = inner_map->ops;
  64         if (inner_map->ops == &array_map_ops || inner_map->ops == &percpu_array_map_ops) {
  65                 struct bpf_array *inner_array_meta =
  66                         container_of(inner_map_meta, struct bpf_array, map);
  67                 struct bpf_array *inner_array = container_of(inner_map, struct bpf_array, map);
  68
  69                 inner_array_meta->index_mask = inner_array->index_mask;
  70                 inner_array_meta->elem_size = inner_array->elem_size;
  71                 inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;
  72         }
  73         return inner_map_meta;
  74 }
  75
  76 void bpf_map_meta_free(struct bpf_map *map_meta)
  77 {
  78         bpf_map_free_record(map_meta);
  79         btf_put(map_meta->btf);
  80         kfree(map_meta);
  81 }
  82
  83 bool bpf_map_meta_equal(const struct bpf_map *meta0,
  84                         const struct bpf_map *meta1)
  85 {
  86         /* No need to compare ops because it is covered by map_type */
  87         return meta0->map_type == meta1->map_type &&
  88                 meta0->key_size == meta1->key_size &&
  89                 meta0->value_size == meta1->value_size &&
  90                 meta0->map_flags == meta1->map_flags &&
  91                 btf_record_equal(meta0->record, meta1->record);
  92 }
  93
  94 void *bpf_map_fd_get_ptr(struct bpf_map *map,
  95                          struct file *map_file /* not used */,
  96                          int ufd)
  97 {
  98         struct bpf_map *inner_map, *inner_map_meta;
  99         CLASS(fd, f)(ufd);
 100
 101         inner_map = __bpf_map_get(f);
 102         if (IS_ERR(inner_map))
 103                 return inner_map;
 104
 105         inner_map_meta = map->inner_map_meta;
 106         if (inner_map_meta->ops->map_meta_equal(inner_map_meta, inner_map))
 107                 bpf_map_inc(inner_map);
 108         else
 109                 inner_map = ERR_PTR(-EINVAL);
 110
 111         return inner_map;
 112 }
 113
 114 void bpf_map_fd_put_ptr(struct bpf_map *map, void *ptr, bool need_defer)
 115 {
 116         struct bpf_map *inner_map = ptr;
 117
 118         /* Defer the freeing of inner map according to the sleepable attribute
 119          * of bpf program which owns the outer map, so unnecessary waiting for
 120          * RCU tasks trace grace period can be avoided.
 121          */
 122         if (need_defer) {
 123                 if (atomic64_read(&map->sleepable_refcnt))
 124                         WRITE_ONCE(inner_map->free_after_mult_rcu_gp, true);
 125                 else
 126                         WRITE_ONCE(inner_map->free_after_rcu_gp, true);
 127         }
 128         bpf_map_put(inner_map);
 129 }
 130
 131 u32 bpf_map_fd_sys_lookup_elem(void *ptr)
 132 {
 133         return ((struct bpf_map *)ptr)->id;
 134 }