summaryrefslogtreecommitdiff
path: root/tools/bpf/bpf_jit_disasm.c
blob: c8ae95804728141654cd4e50b2a612d5f28ed151 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Minimal BPF JIT image disassembler
 *
 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
 * debugging or verification purposes.
 *
 * To get the disassembly of the JIT code, do the following:
 *
 *  1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
 *  2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
 *  3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
 *
 * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
 */

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <bfd.h>
#include <dis-asm.h>
#include <regex.h>
#include <fcntl.h>
#include <sys/klog.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>

#define CMD_ACTION_SIZE_BUFFER		10
#define CMD_ACTION_READ_ALL		3

static void get_exec_path(char *tpath, size_t size)
{
	char *path;
	ssize_t len;

	snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
	tpath[size - 1] = 0;

	path = strdup(tpath);
	assert(path);

	len = readlink(path, tpath, size);
	tpath[len] = 0;

	free(path);
}

static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
{
	int count, i, pc = 0;
	char tpath[PATH_MAX];
	struct disassemble_info info;
	disassembler_ftype disassemble;
	bfd *bfdf;

	memset(tpath, 0, sizeof(tpath));
	get_exec_path(tpath, sizeof(tpath));

	bfdf = bfd_openr(tpath, NULL);
	assert(bfdf);
	assert(bfd_check_format(bfdf, bfd_object));

	init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
	info.arch = bfd_get_arch(bfdf);
	info.mach = bfd_get_mach(bfdf);
	info.buffer = image;
	info.buffer_length = len;

	disassemble_init_for_target(&info);

#ifdef DISASM_FOUR_ARGS_SIGNATURE
	disassemble = disassembler(info.arch,
				   bfd_big_endian(bfdf),
				   info.mach,
				   bfdf);
#else
	disassemble = disassembler(bfdf);
#endif
	assert(disassemble);

	do {
		printf("%4x:\t", pc);

		count = disassemble(pc, &info);

		if (opcodes) {
			printf("\n\t");
			for (i = 0; i < count; ++i)
				printf("%02x ", (uint8_t) image[pc + i]);
		}
		printf("\n");

		pc += count;
	} while(count > 0 && pc < len);

	bfd_close(bfdf);
}

static char *get_klog_buff(unsigned int *klen)
{
	int ret, len;
	char *buff;

	len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
	if (len < 0)
		return NULL;

	buff = malloc(len);
	if (!buff)
		return NULL;

	ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
	if (ret < 0) {
		free(buff);
		return NULL;
	}

	*klen = ret;
	return buff;
}

static char *get_flog_buff(const char *file, unsigned int *klen)
{
	int fd, ret, len;
	struct stat fi;
	char *buff;

	fd = open(file, O_RDONLY);
	if (fd < 0)
		return NULL;

	ret = fstat(fd, &fi);
	if (ret < 0 || !S_ISREG(fi.st_mode))
		goto out;

	len = fi.st_size + 1;
	buff = malloc(len);
	if (!buff)
		goto out;

	memset(buff, 0, len);
	ret = read(fd, buff, len - 1);
	if (ret <= 0)
		goto out_free;

	close(fd);
	*klen = ret;
	return buff;
out_free:
	free(buff);
out:
	close(fd);
	return NULL;
}

static char *get_log_buff(const char *file, unsigned int *klen)
{
	return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
}

static void put_log_buff(char *buff)
{
	free(buff);
}

static uint8_t *get_last_jit_image(char *haystack, size_t hlen,
				   unsigned int *ilen)
{
	char *ptr, *pptr, *tmp;
	off_t off = 0;
	unsigned int proglen;
	int ret, flen, pass, ulen = 0;
	regmatch_t pmatch[1];
	unsigned long base;
	regex_t regex;
	uint8_t *image;

	if (hlen == 0)
		return NULL;

	ret = regcomp(&regex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
		      "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
	assert(ret == 0);

	ptr = haystack;
	memset(pmatch, 0, sizeof(pmatch));

	while (1) {
		ret = regexec(&regex, ptr, 1, pmatch, 0);
		if (ret == 0) {
			ptr += pmatch[0].rm_eo;
			off += pmatch[0].rm_eo;
			assert(off < hlen);
		} else
			break;
	}

	ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
	ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",
		     &flen, &proglen, &pass, &base);
	if (ret != 4) {
		regfree(&regex);
		return NULL;
	}
	if (proglen > 1000000) {
		printf("proglen of %d too big, stopping\n", proglen);
		return NULL;
	}

	image = malloc(proglen);
	if (!image) {
		printf("Out of memory\n");
		return NULL;
	}
	memset(image, 0, proglen);

	tmp = ptr = haystack + off;
	while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {
		tmp = NULL;
		if (!strstr(ptr, "JIT code"))
			continue;
		pptr = ptr;
		while ((ptr = strstr(pptr, ":")))
			pptr = ptr + 1;
		ptr = pptr;
		do {
			image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
			if (ptr == pptr) {
				ulen--;
				break;
			}
			if (ulen >= proglen)
				break;
			ptr = pptr;
		} while (1);
	}

	assert(ulen == proglen);
	printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
	       proglen, pass, flen);
	printf("%lx + <x>:\n", base);

	regfree(&regex);
	*ilen = ulen;
	return image;
}

static void usage(void)
{
	printf("Usage: bpf_jit_disasm [...]\n");
	printf("       -o          Also display related opcodes (default: off).\n");
	printf("       -O <file>   Write binary image of code to file, don't disassemble to stdout.\n");
	printf("       -f <file>   Read last image dump from file or stdin (default: klog).\n");
	printf("       -h          Display this help.\n");
}

int main(int argc, char **argv)
{
	unsigned int len, klen, opt, opcodes = 0;
	char *kbuff, *file = NULL;
	char *ofile = NULL;
	int ofd;
	ssize_t nr;
	uint8_t *pos;
	uint8_t *image = NULL;

	while ((opt = getopt(argc, argv, "of:O:")) != -1) {
		switch (opt) {
		case 'o':
			opcodes = 1;
			break;
		case 'O':
			ofile = optarg;
			break;
		case 'f':
			file = optarg;
			break;
		default:
			usage();
			return -1;
		}
	}

	bfd_init();

	kbuff = get_log_buff(file, &klen);
	if (!kbuff) {
		fprintf(stderr, "Could not retrieve log buffer!\n");
		return -1;
	}

	image = get_last_jit_image(kbuff, klen, &len);
	if (!image) {
		fprintf(stderr, "No JIT image found!\n");
		goto done;
	}
	if (!ofile) {
		get_asm_insns(image, len, opcodes);
		goto done;
	}

	ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
	if (ofd < 0) {
		fprintf(stderr, "Could not open file %s for writing: ", ofile);
		perror(NULL);
		goto done;
	}
	pos = image;
	do {
		nr = write(ofd, pos, len);
		if (nr < 0) {
			fprintf(stderr, "Could not write data to %s: ", ofile);
			perror(NULL);
			goto done;
		}
		len -= nr;
		pos += nr;
	} while (len);
	close(ofd);

done:
	put_log_buff(kbuff);
	free(image);
	return 0;
}