summaryrefslogtreecommitdiff
path: root/tools/lib/bpf/btf.c
blob: c36a3a76986a5ee17ad51a876af10ddb06492fba (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
// SPDX-License-Identifier: LGPL-2.1
/* Copyright (c) 2018 Facebook */

#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <linux/err.h>
#include <linux/btf.h>
#include "btf.h"
#include "bpf.h"

#define elog(fmt, ...) { if (err_log) err_log(fmt, ##__VA_ARGS__); }
#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) < (b) ? (a) : (b))

#define BTF_MAX_NR_TYPES 65535

static struct btf_type btf_void;

struct btf {
	union {
		struct btf_header *hdr;
		void *data;
	};
	struct btf_type **types;
	const char *strings;
	void *nohdr_data;
	__u32 nr_types;
	__u32 types_size;
	__u32 data_size;
	int fd;
};

static const char *btf_name_by_offset(const struct btf *btf, __u32 offset)
{
	if (offset < btf->hdr->str_len)
		return &btf->strings[offset];
	else
		return NULL;
}

static int btf_add_type(struct btf *btf, struct btf_type *t)
{
	if (btf->types_size - btf->nr_types < 2) {
		struct btf_type **new_types;
		__u32 expand_by, new_size;

		if (btf->types_size == BTF_MAX_NR_TYPES)
			return -E2BIG;

		expand_by = max(btf->types_size >> 2, 16);
		new_size = min(BTF_MAX_NR_TYPES, btf->types_size + expand_by);

		new_types = realloc(btf->types, sizeof(*new_types) * new_size);
		if (!new_types)
			return -ENOMEM;

		if (btf->nr_types == 0)
			new_types[0] = &btf_void;

		btf->types = new_types;
		btf->types_size = new_size;
	}

	btf->types[++(btf->nr_types)] = t;

	return 0;
}

static int btf_parse_hdr(struct btf *btf, btf_print_fn_t err_log)
{
	const struct btf_header *hdr = btf->hdr;
	__u32 meta_left;

	if (btf->data_size < sizeof(struct btf_header)) {
		elog("BTF header not found\n");
		return -EINVAL;
	}

	if (hdr->magic != BTF_MAGIC) {
		elog("Invalid BTF magic:%x\n", hdr->magic);
		return -EINVAL;
	}

	if (hdr->version != BTF_VERSION) {
		elog("Unsupported BTF version:%u\n", hdr->version);
		return -ENOTSUP;
	}

	if (hdr->flags) {
		elog("Unsupported BTF flags:%x\n", hdr->flags);
		return -ENOTSUP;
	}

	meta_left = btf->data_size - sizeof(*hdr);
	if (!meta_left) {
		elog("BTF has no data\n");
		return -EINVAL;
	}

	if (meta_left < hdr->type_off) {
		elog("Invalid BTF type section offset:%u\n", hdr->type_off);
		return -EINVAL;
	}

	if (meta_left < hdr->str_off) {
		elog("Invalid BTF string section offset:%u\n", hdr->str_off);
		return -EINVAL;
	}

	if (hdr->type_off >= hdr->str_off) {
		elog("BTF type section offset >= string section offset. No type?\n");
		return -EINVAL;
	}

	if (hdr->type_off & 0x02) {
		elog("BTF type section is not aligned to 4 bytes\n");
		return -EINVAL;
	}

	btf->nohdr_data = btf->hdr + 1;

	return 0;
}

static int btf_parse_str_sec(struct btf *btf, btf_print_fn_t err_log)
{
	const struct btf_header *hdr = btf->hdr;
	const char *start = btf->nohdr_data + hdr->str_off;
	const char *end = start + btf->hdr->str_len;

	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
	    start[0] || end[-1]) {
		elog("Invalid BTF string section\n");
		return -EINVAL;
	}

	btf->strings = start;

	return 0;
}

static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
{
	struct btf_header *hdr = btf->hdr;
	void *nohdr_data = btf->nohdr_data;
	void *next_type = nohdr_data + hdr->type_off;
	void *end_type = nohdr_data + hdr->str_off;

	while (next_type < end_type) {
		struct btf_type *t = next_type;
		__u16 vlen = BTF_INFO_VLEN(t->info);
		int err;

		next_type += sizeof(*t);
		switch (BTF_INFO_KIND(t->info)) {
		case BTF_KIND_INT:
			next_type += sizeof(int);
			break;
		case BTF_KIND_ARRAY:
			next_type += sizeof(struct btf_array);
			break;
		case BTF_KIND_STRUCT:
		case BTF_KIND_UNION:
			next_type += vlen * sizeof(struct btf_member);
			break;
		case BTF_KIND_ENUM:
			next_type += vlen * sizeof(struct btf_enum);
			break;
		case BTF_KIND_TYPEDEF:
		case BTF_KIND_PTR:
		case BTF_KIND_FWD:
		case BTF_KIND_VOLATILE:
		case BTF_KIND_CONST:
		case BTF_KIND_RESTRICT:
			break;
		default:
			elog("Unsupported BTF_KIND:%u\n",
			     BTF_INFO_KIND(t->info));
			return -EINVAL;
		}

		err = btf_add_type(btf, t);
		if (err)
			return err;
	}

	return 0;
}

const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
{
	if (type_id > btf->nr_types)
		return NULL;

	return btf->types[type_id];
}

static bool btf_type_is_void(const struct btf_type *t)
{
	return t == &btf_void || BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
}

static bool btf_type_is_void_or_null(const struct btf_type *t)
{
	return !t || btf_type_is_void(t);
}

static __s64 btf_type_size(const struct btf_type *t)
{
	switch (BTF_INFO_KIND(t->info)) {
	case BTF_KIND_INT:
	case BTF_KIND_STRUCT:
	case BTF_KIND_UNION:
	case BTF_KIND_ENUM:
		return t->size;
	case BTF_KIND_PTR:
		return sizeof(void *);
	default:
		return -EINVAL;
	}
}

#define MAX_RESOLVE_DEPTH 32

__s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
{
	const struct btf_array *array;
	const struct btf_type *t;
	__u32 nelems = 1;
	__s64 size = -1;
	int i;

	t = btf__type_by_id(btf, type_id);
	for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
	     i++) {
		size = btf_type_size(t);
		if (size >= 0)
			break;

		switch (BTF_INFO_KIND(t->info)) {
		case BTF_KIND_TYPEDEF:
		case BTF_KIND_VOLATILE:
		case BTF_KIND_CONST:
		case BTF_KIND_RESTRICT:
			type_id = t->type;
			break;
		case BTF_KIND_ARRAY:
			array = (const struct btf_array *)(t + 1);
			if (nelems && array->nelems > UINT32_MAX / nelems)
				return -E2BIG;
			nelems *= array->nelems;
			type_id = array->type;
			break;
		default:
			return -EINVAL;
		}

		t = btf__type_by_id(btf, type_id);
	}

	if (size < 0)
		return -EINVAL;

	if (nelems && size > UINT32_MAX / nelems)
		return -E2BIG;

	return nelems * size;
}

__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
{
	__u32 i;

	if (!strcmp(type_name, "void"))
		return 0;

	for (i = 1; i <= btf->nr_types; i++) {
		const struct btf_type *t = btf->types[i];
		const char *name = btf_name_by_offset(btf, t->name_off);

		if (name && !strcmp(type_name, name))
			return i;
	}

	return -ENOENT;
}

void btf__free(struct btf *btf)
{
	if (!btf)
		return;

	if (btf->fd != -1)
		close(btf->fd);

	free(btf->data);
	free(btf->types);
	free(btf);
}

struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
{
	__u32 log_buf_size = 0;
	char *log_buf = NULL;
	struct btf *btf;
	int err;

	btf = calloc(1, sizeof(struct btf));
	if (!btf)
		return ERR_PTR(-ENOMEM);

	btf->fd = -1;

	if (err_log) {
		log_buf = malloc(BPF_LOG_BUF_SIZE);
		if (!log_buf) {
			err = -ENOMEM;
			goto done;
		}
		*log_buf = 0;
		log_buf_size = BPF_LOG_BUF_SIZE;
	}

	btf->data = malloc(size);
	if (!btf->data) {
		err = -ENOMEM;
		goto done;
	}

	memcpy(btf->data, data, size);
	btf->data_size = size;

	btf->fd = bpf_load_btf(btf->data, btf->data_size,
			       log_buf, log_buf_size, false);

	if (btf->fd == -1) {
		err = -errno;
		elog("Error loading BTF: %s(%d)\n", strerror(errno), errno);
		if (log_buf && *log_buf)
			elog("%s\n", log_buf);
		goto done;
	}

	err = btf_parse_hdr(btf, err_log);
	if (err)
		goto done;

	err = btf_parse_str_sec(btf, err_log);
	if (err)
		goto done;

	err = btf_parse_type_sec(btf, err_log);

done:
	free(log_buf);

	if (err) {
		btf__free(btf);
		return ERR_PTR(err);
	}

	return btf;
}

int btf__fd(const struct btf *btf)
{
	return btf->fd;
}