xref: /openbmc/linux/drivers/media/rc/bpf-lirc.c (revision da2ef666)
1 // SPDX-License-Identifier: GPL-2.0
2 // bpf-lirc.c - handles bpf
3 //
4 // Copyright (C) 2018 Sean Young <sean@mess.org>
5 
6 #include <linux/bpf.h>
7 #include <linux/filter.h>
8 #include <linux/bpf_lirc.h>
9 #include "rc-core-priv.h"
10 
11 /*
12  * BPF interface for raw IR
13  */
14 const struct bpf_prog_ops lirc_mode2_prog_ops = {
15 };
16 
17 BPF_CALL_1(bpf_rc_repeat, u32*, sample)
18 {
19 	struct ir_raw_event_ctrl *ctrl;
20 
21 	ctrl = container_of(sample, struct ir_raw_event_ctrl, bpf_sample);
22 
23 	rc_repeat(ctrl->dev);
24 
25 	return 0;
26 }
27 
28 static const struct bpf_func_proto rc_repeat_proto = {
29 	.func	   = bpf_rc_repeat,
30 	.gpl_only  = true, /* rc_repeat is EXPORT_SYMBOL_GPL */
31 	.ret_type  = RET_INTEGER,
32 	.arg1_type = ARG_PTR_TO_CTX,
33 };
34 
35 /*
36  * Currently rc-core does not support 64-bit scancodes, but there are many
37  * known protocols with more than 32 bits. So, define the interface as u64
38  * as a future-proof.
39  */
40 BPF_CALL_4(bpf_rc_keydown, u32*, sample, u32, protocol, u64, scancode,
41 	   u32, toggle)
42 {
43 	struct ir_raw_event_ctrl *ctrl;
44 
45 	ctrl = container_of(sample, struct ir_raw_event_ctrl, bpf_sample);
46 
47 	rc_keydown(ctrl->dev, protocol, scancode, toggle != 0);
48 
49 	return 0;
50 }
51 
52 static const struct bpf_func_proto rc_keydown_proto = {
53 	.func	   = bpf_rc_keydown,
54 	.gpl_only  = true, /* rc_keydown is EXPORT_SYMBOL_GPL */
55 	.ret_type  = RET_INTEGER,
56 	.arg1_type = ARG_PTR_TO_CTX,
57 	.arg2_type = ARG_ANYTHING,
58 	.arg3_type = ARG_ANYTHING,
59 	.arg4_type = ARG_ANYTHING,
60 };
61 
62 static const struct bpf_func_proto *
63 lirc_mode2_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
64 {
65 	switch (func_id) {
66 	case BPF_FUNC_rc_repeat:
67 		return &rc_repeat_proto;
68 	case BPF_FUNC_rc_keydown:
69 		return &rc_keydown_proto;
70 	case BPF_FUNC_map_lookup_elem:
71 		return &bpf_map_lookup_elem_proto;
72 	case BPF_FUNC_map_update_elem:
73 		return &bpf_map_update_elem_proto;
74 	case BPF_FUNC_map_delete_elem:
75 		return &bpf_map_delete_elem_proto;
76 	case BPF_FUNC_ktime_get_ns:
77 		return &bpf_ktime_get_ns_proto;
78 	case BPF_FUNC_tail_call:
79 		return &bpf_tail_call_proto;
80 	case BPF_FUNC_get_prandom_u32:
81 		return &bpf_get_prandom_u32_proto;
82 	case BPF_FUNC_trace_printk:
83 		if (capable(CAP_SYS_ADMIN))
84 			return bpf_get_trace_printk_proto();
85 		/* fall through */
86 	default:
87 		return NULL;
88 	}
89 }
90 
91 static bool lirc_mode2_is_valid_access(int off, int size,
92 				       enum bpf_access_type type,
93 				       const struct bpf_prog *prog,
94 				       struct bpf_insn_access_aux *info)
95 {
96 	/* We have one field of u32 */
97 	return type == BPF_READ && off == 0 && size == sizeof(u32);
98 }
99 
100 const struct bpf_verifier_ops lirc_mode2_verifier_ops = {
101 	.get_func_proto  = lirc_mode2_func_proto,
102 	.is_valid_access = lirc_mode2_is_valid_access
103 };
104 
105 #define BPF_MAX_PROGS 64
106 
107 static int lirc_bpf_attach(struct rc_dev *rcdev, struct bpf_prog *prog)
108 {
109 	struct bpf_prog_array __rcu *old_array;
110 	struct bpf_prog_array *new_array;
111 	struct ir_raw_event_ctrl *raw;
112 	int ret;
113 
114 	if (rcdev->driver_type != RC_DRIVER_IR_RAW)
115 		return -EINVAL;
116 
117 	ret = mutex_lock_interruptible(&ir_raw_handler_lock);
118 	if (ret)
119 		return ret;
120 
121 	raw = rcdev->raw;
122 	if (!raw) {
123 		ret = -ENODEV;
124 		goto unlock;
125 	}
126 
127 	if (raw->progs && bpf_prog_array_length(raw->progs) >= BPF_MAX_PROGS) {
128 		ret = -E2BIG;
129 		goto unlock;
130 	}
131 
132 	old_array = raw->progs;
133 	ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
134 	if (ret < 0)
135 		goto unlock;
136 
137 	rcu_assign_pointer(raw->progs, new_array);
138 	bpf_prog_array_free(old_array);
139 
140 unlock:
141 	mutex_unlock(&ir_raw_handler_lock);
142 	return ret;
143 }
144 
145 static int lirc_bpf_detach(struct rc_dev *rcdev, struct bpf_prog *prog)
146 {
147 	struct bpf_prog_array __rcu *old_array;
148 	struct bpf_prog_array *new_array;
149 	struct ir_raw_event_ctrl *raw;
150 	int ret;
151 
152 	if (rcdev->driver_type != RC_DRIVER_IR_RAW)
153 		return -EINVAL;
154 
155 	ret = mutex_lock_interruptible(&ir_raw_handler_lock);
156 	if (ret)
157 		return ret;
158 
159 	raw = rcdev->raw;
160 	if (!raw) {
161 		ret = -ENODEV;
162 		goto unlock;
163 	}
164 
165 	old_array = raw->progs;
166 	ret = bpf_prog_array_copy(old_array, prog, NULL, &new_array);
167 	/*
168 	 * Do not use bpf_prog_array_delete_safe() as we would end up
169 	 * with a dummy entry in the array, and the we would free the
170 	 * dummy in lirc_bpf_free()
171 	 */
172 	if (ret)
173 		goto unlock;
174 
175 	rcu_assign_pointer(raw->progs, new_array);
176 	bpf_prog_array_free(old_array);
177 	bpf_prog_put(prog);
178 unlock:
179 	mutex_unlock(&ir_raw_handler_lock);
180 	return ret;
181 }
182 
183 void lirc_bpf_run(struct rc_dev *rcdev, u32 sample)
184 {
185 	struct ir_raw_event_ctrl *raw = rcdev->raw;
186 
187 	raw->bpf_sample = sample;
188 
189 	if (raw->progs)
190 		BPF_PROG_RUN_ARRAY(raw->progs, &raw->bpf_sample, BPF_PROG_RUN);
191 }
192 
193 /*
194  * This should be called once the rc thread has been stopped, so there can be
195  * no concurrent bpf execution.
196  */
197 void lirc_bpf_free(struct rc_dev *rcdev)
198 {
199 	struct bpf_prog_array_item *item;
200 
201 	if (!rcdev->raw->progs)
202 		return;
203 
204 	item = rcu_dereference(rcdev->raw->progs)->items;
205 	while (item->prog) {
206 		bpf_prog_put(item->prog);
207 		item++;
208 	}
209 
210 	bpf_prog_array_free(rcdev->raw->progs);
211 }
212 
213 int lirc_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
214 {
215 	struct rc_dev *rcdev;
216 	int ret;
217 
218 	if (attr->attach_flags)
219 		return -EINVAL;
220 
221 	rcdev = rc_dev_get_from_fd(attr->target_fd);
222 	if (IS_ERR(rcdev))
223 		return PTR_ERR(rcdev);
224 
225 	ret = lirc_bpf_attach(rcdev, prog);
226 
227 	put_device(&rcdev->dev);
228 
229 	return ret;
230 }
231 
232 int lirc_prog_detach(const union bpf_attr *attr)
233 {
234 	struct bpf_prog *prog;
235 	struct rc_dev *rcdev;
236 	int ret;
237 
238 	if (attr->attach_flags)
239 		return -EINVAL;
240 
241 	prog = bpf_prog_get_type(attr->attach_bpf_fd,
242 				 BPF_PROG_TYPE_LIRC_MODE2);
243 	if (IS_ERR(prog))
244 		return PTR_ERR(prog);
245 
246 	rcdev = rc_dev_get_from_fd(attr->target_fd);
247 	if (IS_ERR(rcdev)) {
248 		bpf_prog_put(prog);
249 		return PTR_ERR(rcdev);
250 	}
251 
252 	ret = lirc_bpf_detach(rcdev, prog);
253 
254 	bpf_prog_put(prog);
255 	put_device(&rcdev->dev);
256 
257 	return ret;
258 }
259 
260 int lirc_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
261 {
262 	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
263 	struct bpf_prog_array __rcu *progs;
264 	struct rc_dev *rcdev;
265 	u32 cnt, flags = 0;
266 	int ret;
267 
268 	if (attr->query.query_flags)
269 		return -EINVAL;
270 
271 	rcdev = rc_dev_get_from_fd(attr->query.target_fd);
272 	if (IS_ERR(rcdev))
273 		return PTR_ERR(rcdev);
274 
275 	if (rcdev->driver_type != RC_DRIVER_IR_RAW) {
276 		ret = -EINVAL;
277 		goto put;
278 	}
279 
280 	ret = mutex_lock_interruptible(&ir_raw_handler_lock);
281 	if (ret)
282 		goto put;
283 
284 	progs = rcdev->raw->progs;
285 	cnt = progs ? bpf_prog_array_length(progs) : 0;
286 
287 	if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt))) {
288 		ret = -EFAULT;
289 		goto unlock;
290 	}
291 
292 	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
293 		ret = -EFAULT;
294 		goto unlock;
295 	}
296 
297 	if (attr->query.prog_cnt != 0 && prog_ids && cnt)
298 		ret = bpf_prog_array_copy_to_user(progs, prog_ids, cnt);
299 
300 unlock:
301 	mutex_unlock(&ir_raw_handler_lock);
302 put:
303 	put_device(&rcdev->dev);
304 
305 	return ret;
306 }
307