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
10struct 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 struct fd f;
15 int ret;
16
17 f = fdget(fd: inner_map_ufd);
18 inner_map = __bpf_map_get(f);
19 if (IS_ERR(ptr: inner_map))
20 return inner_map;
21
22 /* Does not support >1 level map-in-map */
23 if (inner_map->inner_map_meta) {
24 ret = -EINVAL;
25 goto put;
26 }
27
28 if (!inner_map->ops->map_meta_equal) {
29 ret = -ENOTSUPP;
30 goto put;
31 }
32
33 inner_map_meta_size = sizeof(*inner_map_meta);
34 /* In some cases verifier needs to access beyond just base map. */
35 if (inner_map->ops == &array_map_ops)
36 inner_map_meta_size = sizeof(struct bpf_array);
37
38 inner_map_meta = kzalloc(size: inner_map_meta_size, GFP_USER);
39 if (!inner_map_meta) {
40 ret = -ENOMEM;
41 goto put;
42 }
43
44 inner_map_meta->map_type = inner_map->map_type;
45 inner_map_meta->key_size = inner_map->key_size;
46 inner_map_meta->value_size = inner_map->value_size;
47 inner_map_meta->map_flags = inner_map->map_flags;
48 inner_map_meta->max_entries = inner_map->max_entries;
49
50 inner_map_meta->record = btf_record_dup(rec: inner_map->record);
51 if (IS_ERR(ptr: inner_map_meta->record)) {
52 /* btf_record_dup returns NULL or valid pointer in case of
53 * invalid/empty/valid, but ERR_PTR in case of errors. During
54 * equality NULL or IS_ERR is equivalent.
55 */
56 ret = PTR_ERR(ptr: inner_map_meta->record);
57 goto free;
58 }
59 /* Note: We must use the same BTF, as we also used btf_record_dup above
60 * which relies on BTF being same for both maps, as some members like
61 * record->fields.list_head have pointers like value_rec pointing into
62 * inner_map->btf.
63 */
64 if (inner_map->btf) {
65 btf_get(btf: inner_map->btf);
66 inner_map_meta->btf = inner_map->btf;
67 }
68
69 /* Misc members not needed in bpf_map_meta_equal() check. */
70 inner_map_meta->ops = inner_map->ops;
71 if (inner_map->ops == &array_map_ops) {
72 struct bpf_array *inner_array_meta =
73 container_of(inner_map_meta, struct bpf_array, map);
74 struct bpf_array *inner_array = container_of(inner_map, struct bpf_array, map);
75
76 inner_array_meta->index_mask = inner_array->index_mask;
77 inner_array_meta->elem_size = inner_array->elem_size;
78 inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;
79 }
80
81 fdput(fd: f);
82 return inner_map_meta;
83free:
84 kfree(objp: inner_map_meta);
85put:
86 fdput(fd: f);
87 return ERR_PTR(error: ret);
88}
89
90void bpf_map_meta_free(struct bpf_map *map_meta)
91{
92 bpf_map_free_record(map: map_meta);
93 btf_put(btf: map_meta->btf);
94 kfree(objp: map_meta);
95}
96
97bool bpf_map_meta_equal(const struct bpf_map *meta0,
98 const struct bpf_map *meta1)
99{
100 /* No need to compare ops because it is covered by map_type */
101 return meta0->map_type == meta1->map_type &&
102 meta0->key_size == meta1->key_size &&
103 meta0->value_size == meta1->value_size &&
104 meta0->map_flags == meta1->map_flags &&
105 btf_record_equal(rec_a: meta0->record, rec_b: meta1->record);
106}
107
108void *bpf_map_fd_get_ptr(struct bpf_map *map,
109 struct file *map_file /* not used */,
110 int ufd)
111{
112 struct bpf_map *inner_map, *inner_map_meta;
113 struct fd f;
114
115 f = fdget(fd: ufd);
116 inner_map = __bpf_map_get(f);
117 if (IS_ERR(ptr: inner_map))
118 return inner_map;
119
120 inner_map_meta = map->inner_map_meta;
121 if (inner_map_meta->ops->map_meta_equal(inner_map_meta, inner_map))
122 bpf_map_inc(map: inner_map);
123 else
124 inner_map = ERR_PTR(error: -EINVAL);
125
126 fdput(fd: f);
127 return inner_map;
128}
129
130void bpf_map_fd_put_ptr(void *ptr)
131{
132 /* ptr->ops->map_free() has to go through one
133 * rcu grace period by itself.
134 */
135 bpf_map_put(map: ptr);
136}
137
138u32 bpf_map_fd_sys_lookup_elem(void *ptr)
139{
140 return ((struct bpf_map *)ptr)->id;
141}
142

source code of linux/kernel/bpf/map_in_map.c