1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2021. Huawei Technologies Co., Ltd
4 */
5#include <linux/kernel.h>
6#include <linux/bpf_verifier.h>
7#include <linux/bpf.h>
8#include <linux/btf.h>
9
10static struct bpf_struct_ops bpf_bpf_dummy_ops;
11
12/* A common type for test_N with return value in bpf_dummy_ops */
13typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);
14
15static int dummy_ops_test_ret_function(struct bpf_dummy_ops_state *state, ...)
16{
17 return 0;
18}
19
20struct bpf_dummy_ops_test_args {
21 u64 args[MAX_BPF_FUNC_ARGS];
22 struct bpf_dummy_ops_state state;
23};
24
25static struct btf *bpf_dummy_ops_btf;
26
27static struct bpf_dummy_ops_test_args *
28dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
29{
30 __u32 size_in;
31 struct bpf_dummy_ops_test_args *args;
32 void __user *ctx_in;
33 void __user *u_state;
34
35 size_in = kattr->test.ctx_size_in;
36 if (size_in != sizeof(u64) * nr)
37 return ERR_PTR(error: -EINVAL);
38
39 args = kzalloc(size: sizeof(*args), GFP_KERNEL);
40 if (!args)
41 return ERR_PTR(error: -ENOMEM);
42
43 ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
44 if (copy_from_user(to: args->args, from: ctx_in, n: size_in))
45 goto out;
46
47 /* args[0] is 0 means state argument of test_N will be NULL */
48 u_state = u64_to_user_ptr(args->args[0]);
49 if (u_state && copy_from_user(to: &args->state, from: u_state,
50 n: sizeof(args->state)))
51 goto out;
52
53 return args;
54out:
55 kfree(objp: args);
56 return ERR_PTR(error: -EFAULT);
57}
58
59static int dummy_ops_copy_args(struct bpf_dummy_ops_test_args *args)
60{
61 void __user *u_state;
62
63 u_state = u64_to_user_ptr(args->args[0]);
64 if (u_state && copy_to_user(to: u_state, from: &args->state, n: sizeof(args->state)))
65 return -EFAULT;
66
67 return 0;
68}
69
70static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
71{
72 dummy_ops_test_ret_fn test = (void *)image + cfi_get_offset();
73 struct bpf_dummy_ops_state *state = NULL;
74
75 /* state needs to be NULL if args[0] is 0 */
76 if (args->args[0])
77 state = &args->state;
78 return test(state, args->args[1], args->args[2],
79 args->args[3], args->args[4]);
80}
81
82extern const struct bpf_link_ops bpf_struct_ops_link_lops;
83
84int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
85 union bpf_attr __user *uattr)
86{
87 const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
88 const struct btf_type *func_proto;
89 struct bpf_dummy_ops_test_args *args;
90 struct bpf_tramp_links *tlinks;
91 struct bpf_tramp_link *link = NULL;
92 void *image = NULL;
93 unsigned int op_idx;
94 u32 image_off = 0;
95 int prog_ret;
96 s32 type_id;
97 int err;
98
99 type_id = btf_find_by_name_kind(btf: bpf_dummy_ops_btf,
100 name: bpf_bpf_dummy_ops.name,
101 kind: BTF_KIND_STRUCT);
102 if (type_id < 0)
103 return -EINVAL;
104 if (prog->aux->attach_btf_id != type_id)
105 return -EOPNOTSUPP;
106
107 func_proto = prog->aux->attach_func_proto;
108 args = dummy_ops_init_args(kattr, nr: btf_type_vlen(t: func_proto));
109 if (IS_ERR(ptr: args))
110 return PTR_ERR(ptr: args);
111
112 tlinks = kcalloc(n: BPF_TRAMP_MAX, size: sizeof(*tlinks), GFP_KERNEL);
113 if (!tlinks) {
114 err = -ENOMEM;
115 goto out;
116 }
117
118 link = kzalloc(size: sizeof(*link), GFP_USER);
119 if (!link) {
120 err = -ENOMEM;
121 goto out;
122 }
123 /* prog doesn't take the ownership of the reference from caller */
124 bpf_prog_inc(prog);
125 bpf_link_init(link: &link->link, type: BPF_LINK_TYPE_STRUCT_OPS, ops: &bpf_struct_ops_link_lops, prog);
126
127 op_idx = prog->expected_attach_type;
128 err = bpf_struct_ops_prepare_trampoline(tlinks, link,
129 model: &st_ops->func_models[op_idx],
130 stub_func: &dummy_ops_test_ret_function,
131 image: &image, image_off: &image_off,
132 allow_alloc: true);
133 if (err < 0)
134 goto out;
135
136 arch_protect_bpf_trampoline(image, PAGE_SIZE);
137 prog_ret = dummy_ops_call_op(image, args);
138
139 err = dummy_ops_copy_args(args);
140 if (err)
141 goto out;
142 if (put_user(prog_ret, &uattr->test.retval))
143 err = -EFAULT;
144out:
145 kfree(objp: args);
146 bpf_struct_ops_image_free(image);
147 if (link)
148 bpf_link_put(link: &link->link);
149 kfree(objp: tlinks);
150 return err;
151}
152
153static int bpf_dummy_init(struct btf *btf)
154{
155 bpf_dummy_ops_btf = btf;
156 return 0;
157}
158
159static bool bpf_dummy_ops_is_valid_access(int off, int size,
160 enum bpf_access_type type,
161 const struct bpf_prog *prog,
162 struct bpf_insn_access_aux *info)
163{
164 return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
165}
166
167static int bpf_dummy_ops_check_member(const struct btf_type *t,
168 const struct btf_member *member,
169 const struct bpf_prog *prog)
170{
171 u32 moff = __btf_member_bit_offset(struct_type: t, member) / 8;
172
173 switch (moff) {
174 case offsetof(struct bpf_dummy_ops, test_sleepable):
175 break;
176 default:
177 if (prog->sleepable)
178 return -EINVAL;
179 }
180
181 return 0;
182}
183
184static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
185 const struct bpf_reg_state *reg,
186 int off, int size)
187{
188 const struct btf_type *state;
189 const struct btf_type *t;
190 s32 type_id;
191
192 type_id = btf_find_by_name_kind(btf: reg->btf, name: "bpf_dummy_ops_state",
193 kind: BTF_KIND_STRUCT);
194 if (type_id < 0)
195 return -EINVAL;
196
197 t = btf_type_by_id(btf: reg->btf, type_id: reg->btf_id);
198 state = btf_type_by_id(btf: reg->btf, type_id);
199 if (t != state) {
200 bpf_log(log, fmt: "only access to bpf_dummy_ops_state is supported\n");
201 return -EACCES;
202 }
203
204 if (off + size > sizeof(struct bpf_dummy_ops_state)) {
205 bpf_log(log, fmt: "write access at off %d with size %d\n", off, size);
206 return -EACCES;
207 }
208
209 return NOT_INIT;
210}
211
212static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
213 .is_valid_access = bpf_dummy_ops_is_valid_access,
214 .btf_struct_access = bpf_dummy_ops_btf_struct_access,
215};
216
217static int bpf_dummy_init_member(const struct btf_type *t,
218 const struct btf_member *member,
219 void *kdata, const void *udata)
220{
221 return -EOPNOTSUPP;
222}
223
224static int bpf_dummy_reg(void *kdata)
225{
226 return -EOPNOTSUPP;
227}
228
229static void bpf_dummy_unreg(void *kdata)
230{
231}
232
233static int bpf_dummy_test_1(struct bpf_dummy_ops_state *cb)
234{
235 return 0;
236}
237
238static int bpf_dummy_test_2(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
239 char a3, unsigned long a4)
240{
241 return 0;
242}
243
244static int bpf_dummy_test_sleepable(struct bpf_dummy_ops_state *cb)
245{
246 return 0;
247}
248
249static struct bpf_dummy_ops __bpf_bpf_dummy_ops = {
250 .test_1 = bpf_dummy_test_1,
251 .test_2 = bpf_dummy_test_2,
252 .test_sleepable = bpf_dummy_test_sleepable,
253};
254
255static struct bpf_struct_ops bpf_bpf_dummy_ops = {
256 .verifier_ops = &bpf_dummy_verifier_ops,
257 .init = bpf_dummy_init,
258 .check_member = bpf_dummy_ops_check_member,
259 .init_member = bpf_dummy_init_member,
260 .reg = bpf_dummy_reg,
261 .unreg = bpf_dummy_unreg,
262 .name = "bpf_dummy_ops",
263 .cfi_stubs = &__bpf_bpf_dummy_ops,
264 .owner = THIS_MODULE,
265};
266
267static int __init bpf_dummy_struct_ops_init(void)
268{
269 return register_bpf_struct_ops(&bpf_bpf_dummy_ops, bpf_dummy_ops);
270}
271late_initcall(bpf_dummy_struct_ops_init);
272

source code of linux/net/bpf/bpf_dummy_struct_ops.c