summaryrefslogtreecommitdiff
path: root/kernel/bpf/bpf_struct_ops.c
blob: 042f95534f86db0b11148b72d64db98162dd0439 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2019 Facebook */

#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/btf.h>
#include <linux/filter.h>
#include <linux/slab.h>
#include <linux/numa.h>
#include <linux/seq_file.h>
#include <linux/refcount.h>
#include <linux/mutex.h>

enum bpf_struct_ops_state {
	BPF_STRUCT_OPS_STATE_INIT,
	BPF_STRUCT_OPS_STATE_INUSE,
	BPF_STRUCT_OPS_STATE_TOBEFREE,
};

#define BPF_STRUCT_OPS_COMMON_VALUE			\
	refcount_t refcnt;				\
	enum bpf_struct_ops_state state

struct bpf_struct_ops_value {
	BPF_STRUCT_OPS_COMMON_VALUE;
	char data[0] ____cacheline_aligned_in_smp;
};

struct bpf_struct_ops_map {
	struct bpf_map map;
	const struct bpf_struct_ops *st_ops;
	/* protect map_update */
	struct mutex lock;
	/* progs has all the bpf_prog that is populated
	 * to the func ptr of the kernel's struct
	 * (in kvalue.data).
	 */
	struct bpf_prog **progs;
	/* image is a page that has all the trampolines
	 * that stores the func args before calling the bpf_prog.
	 * A PAGE_SIZE "image" is enough to store all trampoline for
	 * "progs[]".
	 */
	void *image;
	/* uvalue->data stores the kernel struct
	 * (e.g. tcp_congestion_ops) that is more useful
	 * to userspace than the kvalue.  For example,
	 * the bpf_prog's id is stored instead of the kernel
	 * address of a func ptr.
	 */
	struct bpf_struct_ops_value *uvalue;
	/* kvalue.data stores the actual kernel's struct
	 * (e.g. tcp_congestion_ops) that will be
	 * registered to the kernel subsystem.
	 */
	struct bpf_struct_ops_value kvalue;
};

#define VALUE_PREFIX "bpf_struct_ops_"
#define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)

/* bpf_struct_ops_##_name (e.g. bpf_struct_ops_tcp_congestion_ops) is
 * the map's value exposed to the userspace and its btf-type-id is
 * stored at the map->btf_vmlinux_value_type_id.
 *
 */
#define BPF_STRUCT_OPS_TYPE(_name)				\
extern struct bpf_struct_ops bpf_##_name;			\
								\
struct bpf_struct_ops_##_name {						\
	BPF_STRUCT_OPS_COMMON_VALUE;				\
	struct _name data ____cacheline_aligned_in_smp;		\
};
#include "bpf_struct_ops_types.h"
#undef BPF_STRUCT_OPS_TYPE

enum {
#define BPF_STRUCT_OPS_TYPE(_name) BPF_STRUCT_OPS_TYPE_##_name,
#include "bpf_struct_ops_types.h"
#undef BPF_STRUCT_OPS_TYPE
	__NR_BPF_STRUCT_OPS_TYPE,
};

static struct bpf_struct_ops * const bpf_struct_ops[] = {
#define BPF_STRUCT_OPS_TYPE(_name)				\
	[BPF_STRUCT_OPS_TYPE_##_name] = &bpf_##_name,
#include "bpf_struct_ops_types.h"
#undef BPF_STRUCT_OPS_TYPE
};

const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
};

const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
};

static const struct btf_type *module_type;

void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
{
	s32 type_id, value_id, module_id;
	const struct btf_member *member;
	struct bpf_struct_ops *st_ops;
	const struct btf_type *t;
	char value_name[128];
	const char *mname;
	u32 i, j;

	/* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
#define BPF_STRUCT_OPS_TYPE(_name) BTF_TYPE_EMIT(struct bpf_struct_ops_##_name);
#include "bpf_struct_ops_types.h"
#undef BPF_STRUCT_OPS_TYPE

	module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
	if (module_id < 0) {
		pr_warn("Cannot find struct module in btf_vmlinux\n");
		return;
	}
	module_type = btf_type_by_id(btf, module_id);

	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
		st_ops = bpf_struct_ops[i];

		if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
		    sizeof(value_name)) {
			pr_warn("struct_ops name %s is too long\n",
				st_ops->name);
			continue;
		}
		sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);

		value_id = btf_find_by_name_kind(btf, value_name,
						 BTF_KIND_STRUCT);
		if (value_id < 0) {
			pr_warn("Cannot find struct %s in btf_vmlinux\n",
				value_name);
			continue;
		}

		type_id = btf_find_by_name_kind(btf, st_ops->name,
						BTF_KIND_STRUCT);
		if (type_id < 0) {
			pr_warn("Cannot find struct %s in btf_vmlinux\n",
				st_ops->name);
			continue;
		}
		t = btf_type_by_id(btf, type_id);
		if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
			pr_warn("Cannot support #%u members in struct %s\n",
				btf_type_vlen(t), st_ops->name);
			continue;
		}

		for_each_member(j, t, member) {
			const struct btf_type *func_proto;

			mname = btf_name_by_offset(btf, member->name_off);
			if (!*mname) {
				pr_warn("anon member in struct %s is not supported\n",
					st_ops->name);
				break;
			}

			if (btf_member_bitfield_size(t, member)) {
				pr_warn("bit field member %s in struct %s is not supported\n",
					mname, st_ops->name);
				break;
			}

			func_proto = btf_type_resolve_func_ptr(btf,
							       member->type,
							       NULL);
			if (func_proto &&
			    btf_distill_func_proto(log, btf,
						   func_proto, mname,
						   &st_ops->func_models[j])) {
				pr_warn("Error in parsing func ptr %s in struct %s\n",
					mname, st_ops->name);
				break;
			}
		}

		if (j == btf_type_vlen(t)) {
			if (st_ops->init(btf)) {
				pr_warn("Error in init bpf_struct_ops %s\n",
					st_ops->name);
			} else {
				st_ops->type_id = type_id;
				st_ops->type = t;
				st_ops->value_id = value_id;
				st_ops->value_type = btf_type_by_id(btf,
								    value_id);
			}
		}
	}
}

extern struct btf *btf_vmlinux;

static const struct bpf_struct_ops *
bpf_struct_ops_find_value(u32 value_id)
{
	unsigned int i;

	if (!value_id || !btf_vmlinux)
		return NULL;

	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
		if (bpf_struct_ops[i]->value_id == value_id)
			return bpf_struct_ops[i];
	}

	return NULL;
}

const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
{
	unsigned int i;

	if (!type_id || !btf_vmlinux)
		return NULL;

	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
		if (bpf_struct_ops[i]->type_id == type_id)
			return bpf_struct_ops[i];
	}

	return NULL;
}

static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
					   void *next_key)
{
	if (key && *(u32 *)key == 0)
		return -ENOENT;

	*(u32 *)next_key = 0;
	return 0;
}

int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
				       void *value)
{
	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
	struct bpf_struct_ops_value *uvalue, *kvalue;
	enum bpf_struct_ops_state state;

	if (unlikely(*(u32 *)key != 0))
		return -ENOENT;

	kvalue = &st_map->kvalue;
	/* Pair with smp_store_release() during map_update */
	state = smp_load_acquire(&kvalue->state);
	if (state == BPF_STRUCT_OPS_STATE_INIT) {
		memset(value, 0, map->value_size);
		return 0;
	}

	/* No lock is needed.  state and refcnt do not need
	 * to be updated together under atomic context.
	 */
	uvalue = (struct bpf_struct_ops_value *)value;
	memcpy(uvalue, st_map->uvalue, map->value_size);
	uvalue->state = state;
	refcount_set(&uvalue->refcnt, refcount_read(&kvalue->refcnt));

	return 0;
}

static void *bpf_struct_ops_map_lookup_elem(struct bpf_map *map, void *key)
{
	return ERR_PTR(-EINVAL);
}

static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
{
	const struct btf_type *t = st_map->st_ops->type;
	u32 i;

	for (i = 0; i < btf_type_vlen(t); i++) {
		if (st_map->progs[i]) {
			bpf_prog_put(st_map->progs[i]);
			st_map->progs[i] = NULL;
		}
	}
}

static int check_zero_holes(const struct btf_type *t, void *data)
{
	const struct btf_member *member;
	u32 i, moff, msize, prev_mend = 0;
	const struct btf_type *mtype;

	for_each_member(i, t, member) {
		moff = btf_member_bit_offset(t, member) / 8;
		if (moff > prev_mend &&
		    memchr_inv(data + prev_mend, 0, moff - prev_mend))
			return -EINVAL;

		mtype = btf_type_by_id(btf_vmlinux, member->type);
		mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
					 NULL, NULL);
		if (IS_ERR(mtype))
			return PTR_ERR(mtype);
		prev_mend = moff + msize;
	}

	if (t->size > prev_mend &&
	    memchr_inv(data + prev_mend, 0, t->size - prev_mend))
		return -EINVAL;

	return 0;
}

static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
					  void *value, u64 flags)
{
	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
	const struct bpf_struct_ops *st_ops = st_map->st_ops;
	struct bpf_struct_ops_value *uvalue, *kvalue;
	const struct btf_member *member;
	const struct btf_type *t = st_ops->type;
	void *udata, *kdata;
	int prog_fd, err = 0;
	void *image;
	u32 i;

	if (flags)
		return -EINVAL;

	if (*(u32 *)key != 0)
		return -E2BIG;

	err = check_zero_holes(st_ops->value_type, value);
	if (err)
		return err;

	uvalue = (struct bpf_struct_ops_value *)value;
	err = check_zero_holes(t, uvalue->data);
	if (err)
		return err;

	if (uvalue->state || refcount_read(&uvalue->refcnt))
		return -EINVAL;

	uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
	kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;

	mutex_lock(&st_map->lock);

	if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
		err = -EBUSY;
		goto unlock;
	}

	memcpy(uvalue, value, map->value_size);

	udata = &uvalue->data;
	kdata = &kvalue->data;
	image = st_map->image;

	for_each_member(i, t, member) {
		const struct btf_type *mtype, *ptype;
		struct bpf_prog *prog;
		u32 moff;

		moff = btf_member_bit_offset(t, member) / 8;
		ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
		if (ptype == module_type) {
			if (*(void **)(udata + moff))
				goto reset_unlock;
			*(void **)(kdata + moff) = BPF_MODULE_OWNER;
			continue;
		}

		err = st_ops->init_member(t, member, kdata, udata);
		if (err < 0)
			goto reset_unlock;

		/* The ->init_member() has handled this member */
		if (err > 0)
			continue;

		/* If st_ops->init_member does not handle it,
		 * we will only handle func ptrs and zero-ed members
		 * here.  Reject everything else.
		 */

		/* All non func ptr member must be 0 */
		if (!ptype || !btf_type_is_func_proto(ptype)) {
			u32 msize;

			mtype = btf_type_by_id(btf_vmlinux, member->type);
			mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
						 NULL, NULL);
			if (IS_ERR(mtype)) {
				err = PTR_ERR(mtype);
				goto reset_unlock;
			}

			if (memchr_inv(udata + moff, 0, msize)) {
				err = -EINVAL;
				goto reset_unlock;
			}

			continue;
		}

		prog_fd = (int)(*(unsigned long *)(udata + moff));
		/* Similar check as the attr->attach_prog_fd */
		if (!prog_fd)
			continue;

		prog = bpf_prog_get(prog_fd);
		if (IS_ERR(prog)) {
			err = PTR_ERR(prog);
			goto reset_unlock;
		}
		st_map->progs[i] = prog;

		if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
		    prog->aux->attach_btf_id != st_ops->type_id ||
		    prog->expected_attach_type != i) {
			err = -EINVAL;
			goto reset_unlock;
		}

		err = arch_prepare_bpf_trampoline(image,
						  st_map->image + PAGE_SIZE,
						  &st_ops->func_models[i], 0,
						  &prog, 1, NULL, 0, NULL);
		if (err < 0)
			goto reset_unlock;

		*(void **)(kdata + moff) = image;
		image += err;

		/* put prog_id to udata */
		*(unsigned long *)(udata + moff) = prog->aux->id;
	}

	refcount_set(&kvalue->refcnt, 1);
	bpf_map_inc(map);

	set_memory_ro((long)st_map->image, 1);
	set_memory_x((long)st_map->image, 1);
	err = st_ops->reg(kdata);
	if (likely(!err)) {
		/* Pair with smp_load_acquire() during lookup_elem().
		 * It ensures the above udata updates (e.g. prog->aux->id)
		 * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
		 */
		smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
		goto unlock;
	}

	/* Error during st_ops->reg().  It is very unlikely since
	 * the above init_member() should have caught it earlier
	 * before reg().  The only possibility is if there was a race
	 * in registering the struct_ops (under the same name) to
	 * a sub-system through different struct_ops's maps.
	 */
	set_memory_nx((long)st_map->image, 1);
	set_memory_rw((long)st_map->image, 1);
	bpf_map_put(map);

reset_unlock:
	bpf_struct_ops_map_put_progs(st_map);
	memset(uvalue, 0, map->value_size);
	memset(kvalue, 0, map->value_size);
unlock:
	mutex_unlock(&st_map->lock);
	return err;
}

static int bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
{
	enum bpf_struct_ops_state prev_state;
	struct bpf_struct_ops_map *st_map;

	st_map = (struct bpf_struct_ops_map *)map;
	prev_state = cmpxchg(&st_map->kvalue.state,
			     BPF_STRUCT_OPS_STATE_INUSE,
			     BPF_STRUCT_OPS_STATE_TOBEFREE);
	if (prev_state == BPF_STRUCT_OPS_STATE_INUSE) {
		st_map->st_ops->unreg(&st_map->kvalue.data);
		if (refcount_dec_and_test(&st_map->kvalue.refcnt))
			bpf_map_put(map);
	}

	return 0;
}

static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
					     struct seq_file *m)
{
	void *value;
	int err;

	value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
	if (!value)
		return;

	err = bpf_struct_ops_map_sys_lookup_elem(map, key, value);
	if (!err) {
		btf_type_seq_show(btf_vmlinux, map->btf_vmlinux_value_type_id,
				  value, m);
		seq_puts(m, "\n");
	}

	kfree(value);
}

static void bpf_struct_ops_map_free(struct bpf_map *map)
{
	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;

	if (st_map->progs)
		bpf_struct_ops_map_put_progs(st_map);
	bpf_map_area_free(st_map->progs);
	bpf_jit_free_exec(st_map->image);
	bpf_map_area_free(st_map->uvalue);
	bpf_map_area_free(st_map);
}

static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
{
	if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
	    attr->map_flags || !attr->btf_vmlinux_value_type_id)
		return -EINVAL;
	return 0;
}

static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
{
	const struct bpf_struct_ops *st_ops;
	size_t map_total_size, st_map_size;
	struct bpf_struct_ops_map *st_map;
	const struct btf_type *t, *vt;
	struct bpf_map_memory mem;
	struct bpf_map *map;
	int err;

	if (!capable(CAP_SYS_ADMIN))
		return ERR_PTR(-EPERM);

	st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
	if (!st_ops)
		return ERR_PTR(-ENOTSUPP);

	vt = st_ops->value_type;
	if (attr->value_size != vt->size)
		return ERR_PTR(-EINVAL);

	t = st_ops->type;

	st_map_size = sizeof(*st_map) +
		/* kvalue stores the
		 * struct bpf_struct_ops_tcp_congestions_ops
		 */
		(vt->size - sizeof(struct bpf_struct_ops_value));
	map_total_size = st_map_size +
		/* uvalue */
		sizeof(vt->size) +
		/* struct bpf_progs **progs */
		 btf_type_vlen(t) * sizeof(struct bpf_prog *);
	err = bpf_map_charge_init(&mem, map_total_size);
	if (err < 0)
		return ERR_PTR(err);

	st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
	if (!st_map) {
		bpf_map_charge_finish(&mem);
		return ERR_PTR(-ENOMEM);
	}
	st_map->st_ops = st_ops;
	map = &st_map->map;

	st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
	st_map->progs =
		bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_prog *),
				   NUMA_NO_NODE);
	st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
	if (!st_map->uvalue || !st_map->progs || !st_map->image) {
		bpf_struct_ops_map_free(map);
		bpf_map_charge_finish(&mem);
		return ERR_PTR(-ENOMEM);
	}

	mutex_init(&st_map->lock);
	set_vm_flush_reset_perms(st_map->image);
	bpf_map_init_from_attr(map, attr);
	bpf_map_charge_move(&map->memory, &mem);

	return map;
}

const struct bpf_map_ops bpf_struct_ops_map_ops = {
	.map_alloc_check = bpf_struct_ops_map_alloc_check,
	.map_alloc = bpf_struct_ops_map_alloc,
	.map_free = bpf_struct_ops_map_free,
	.map_get_next_key = bpf_struct_ops_map_get_next_key,
	.map_lookup_elem = bpf_struct_ops_map_lookup_elem,
	.map_delete_elem = bpf_struct_ops_map_delete_elem,
	.map_update_elem = bpf_struct_ops_map_update_elem,
	.map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
};

/* "const void *" because some subsystem is
 * passing a const (e.g. const struct tcp_congestion_ops *)
 */
bool bpf_struct_ops_get(const void *kdata)
{
	struct bpf_struct_ops_value *kvalue;

	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);

	return refcount_inc_not_zero(&kvalue->refcnt);
}

void bpf_struct_ops_put(const void *kdata)
{
	struct bpf_struct_ops_value *kvalue;

	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
	if (refcount_dec_and_test(&kvalue->refcnt)) {
		struct bpf_struct_ops_map *st_map;

		st_map = container_of(kvalue, struct bpf_struct_ops_map,
				      kvalue);
		bpf_map_put(&st_map->map);
	}
}