bpf_dummy_struct_ops.c

  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(-EINVAL);
 38
 39	args = kzalloc(sizeof(*args), GFP_KERNEL);
 40	if (!args)
 41		return ERR_PTR(-ENOMEM);
 42
 43	ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
 44	if (copy_from_user(args->args, ctx_in, 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(&args->state, u_state,
 50				      sizeof(args->state)))
 51		goto out;
 52
 53	return args;
 54out:
 55	kfree(args);
 56	return ERR_PTR(-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(u_state, &args->state, 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
 82static const struct bpf_ctx_arg_aux *find_ctx_arg_info(struct bpf_prog_aux *aux, int offset)
 83{
 84	int i;
 85
 86	for (i = 0; i < aux->ctx_arg_info_size; i++)
 87		if (aux->ctx_arg_info[i].offset == offset)
 88			return &aux->ctx_arg_info[i];
 89
 90	return NULL;
 91}
 92
 93/* There is only one check at the moment:
 94 * - zero should not be passed for pointer parameters not marked as nullable.
 95 */
 96static int check_test_run_args(struct bpf_prog *prog, struct bpf_dummy_ops_test_args *args)
 97{
 98	const struct btf_type *func_proto = prog->aux->attach_func_proto;
 99
100	for (u32 arg_no = 0; arg_no < btf_type_vlen(func_proto) ; ++arg_no) {
101		const struct btf_param *param = &btf_params(func_proto)[arg_no];
102		const struct bpf_ctx_arg_aux *info;
103		const struct btf_type *t;
104		int offset;
105
106		if (args->args[arg_no] != 0)
107			continue;
108
109		/* Program is validated already, so there is no need
110		 * to check if t is NULL.
111		 */
112		t = btf_type_skip_modifiers(bpf_dummy_ops_btf, param->type, NULL);
113		if (!btf_type_is_ptr(t))
114			continue;
115
116		offset = btf_ctx_arg_offset(bpf_dummy_ops_btf, func_proto, arg_no);
117		info = find_ctx_arg_info(prog->aux, offset);
118		if (info && type_may_be_null(info->reg_type))
119			continue;
120
121		return -EINVAL;
122	}
123
124	return 0;
125}
126
127extern const struct bpf_link_ops bpf_struct_ops_link_lops;
128
129int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
130			    union bpf_attr __user *uattr)
131{
132	const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
133	const struct btf_type *func_proto;
134	struct bpf_dummy_ops_test_args *args;
135	struct bpf_tramp_links *tlinks = NULL;
136	struct bpf_tramp_link *link = NULL;
137	void *image = NULL;
138	unsigned int op_idx;
139	u32 image_off = 0;
140	int prog_ret;
141	s32 type_id;
142	int err;
143
144	type_id = btf_find_by_name_kind(bpf_dummy_ops_btf,
145					bpf_bpf_dummy_ops.name,
146					BTF_KIND_STRUCT);
147	if (type_id < 0)
148		return -EINVAL;
149	if (prog->aux->attach_btf_id != type_id)
150		return -EOPNOTSUPP;
151
152	func_proto = prog->aux->attach_func_proto;
153	args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
154	if (IS_ERR(args))
155		return PTR_ERR(args);
156
157	err = check_test_run_args(prog, args);
158	if (err)
159		goto out;
160
161	tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
162	if (!tlinks) {
163		err = -ENOMEM;
164		goto out;
165	}
166
167	link = kzalloc(sizeof(*link), GFP_USER);
168	if (!link) {
169		err = -ENOMEM;
170		goto out;
171	}
172	/* prog doesn't take the ownership of the reference from caller */
173	bpf_prog_inc(prog);
174	bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_link_lops, prog,
175		      prog->expected_attach_type);
176
177	op_idx = prog->expected_attach_type;
178	err = bpf_struct_ops_prepare_trampoline(tlinks, link,
179						&st_ops->func_models[op_idx],
180						&dummy_ops_test_ret_function,
181						&image, &image_off,
182						true);
183	if (err < 0)
184		goto out;
185
186	err = arch_protect_bpf_trampoline(image, PAGE_SIZE);
187	if (err)
188		goto out;
189	prog_ret = dummy_ops_call_op(image, args);
190
191	err = dummy_ops_copy_args(args);
192	if (err)
193		goto out;
194	if (put_user(prog_ret, &uattr->test.retval))
195		err = -EFAULT;
196out:
197	kfree(args);
198	bpf_struct_ops_image_free(image);
199	if (link)
200		bpf_link_put(&link->link);
201	kfree(tlinks);
202	return err;
203}
204
205static int bpf_dummy_init(struct btf *btf)
206{
207	bpf_dummy_ops_btf = btf;
208	return 0;
209}
210
211static bool bpf_dummy_ops_is_valid_access(int off, int size,
212					  enum bpf_access_type type,
213					  const struct bpf_prog *prog,
214					  struct bpf_insn_access_aux *info)
215{
216	return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
217}
218
219static int bpf_dummy_ops_check_member(const struct btf_type *t,
220				      const struct btf_member *member,
221				      const struct bpf_prog *prog)
222{
223	u32 moff = __btf_member_bit_offset(t, member) / 8;
224
225	switch (moff) {
226	case offsetof(struct bpf_dummy_ops, test_sleepable):
227		break;
228	default:
229		if (prog->sleepable)
230			return -EINVAL;
231	}
232
233	return 0;
234}
235
236static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
237					   const struct bpf_reg_state *reg,
238					   int off, int size)
239{
240	const struct btf_type *state;
241	const struct btf_type *t;
242	s32 type_id;
243
244	type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
245					BTF_KIND_STRUCT);
246	if (type_id < 0)
247		return -EINVAL;
248
249	t = btf_type_by_id(reg->btf, reg->btf_id);
250	state = btf_type_by_id(reg->btf, type_id);
251	if (t != state) {
252		bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
253		return -EACCES;
254	}
255
256	if (off + size > sizeof(struct bpf_dummy_ops_state)) {
257		bpf_log(log, "write access at off %d with size %d\n", off, size);
258		return -EACCES;
259	}
260
261	return NOT_INIT;
262}
263
264static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
265	.is_valid_access = bpf_dummy_ops_is_valid_access,
266	.btf_struct_access = bpf_dummy_ops_btf_struct_access,
267};
268
269static int bpf_dummy_init_member(const struct btf_type *t,
270				 const struct btf_member *member,
271				 void *kdata, const void *udata)
272{
273	return -EOPNOTSUPP;
274}
275
276static int bpf_dummy_reg(void *kdata, struct bpf_link *link)
277{
278	return -EOPNOTSUPP;
279}
280
281static void bpf_dummy_unreg(void *kdata, struct bpf_link *link)
282{
283}
284
285static int bpf_dummy_ops__test_1(struct bpf_dummy_ops_state *cb__nullable)
286{
287	return 0;
288}
289
290static int bpf_dummy_test_2(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
291			    char a3, unsigned long a4)
292{
293	return 0;
294}
295
296static int bpf_dummy_test_sleepable(struct bpf_dummy_ops_state *cb)
297{
298	return 0;
299}
300
301static struct bpf_dummy_ops __bpf_bpf_dummy_ops = {
302	.test_1 = bpf_dummy_ops__test_1,
303	.test_2 = bpf_dummy_test_2,
304	.test_sleepable = bpf_dummy_test_sleepable,
305};
306
307static struct bpf_struct_ops bpf_bpf_dummy_ops = {
308	.verifier_ops = &bpf_dummy_verifier_ops,
309	.init = bpf_dummy_init,
310	.check_member = bpf_dummy_ops_check_member,
311	.init_member = bpf_dummy_init_member,
312	.reg = bpf_dummy_reg,
313	.unreg = bpf_dummy_unreg,
314	.name = "bpf_dummy_ops",
315	.cfi_stubs = &__bpf_bpf_dummy_ops,
316	.owner = THIS_MODULE,
317};
318
319static int __init bpf_dummy_struct_ops_init(void)
320{
321	return register_bpf_struct_ops(&bpf_bpf_dummy_ops, bpf_dummy_ops);
322}
323late_initcall(bpf_dummy_struct_ops_init);