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Daniel Borkmanne306e2c2013-03-20 12:11:47 +00001/*
2 * Minimal BPF JIT image disassembler
3 *
4 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
5 * debugging or verification purposes.
6 *
7 * To get the disassembly of the JIT code, do the following:
8 *
9 * 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
10 * 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
11 * 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
12 *
13 * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
14 * Licensed under the GNU General Public License, version 2.0 (GPLv2)
15 */
16
17#include <stdint.h>
18#include <stdio.h>
19#include <stdlib.h>
20#include <assert.h>
21#include <unistd.h>
22#include <string.h>
23#include <bfd.h>
24#include <dis-asm.h>
Daniel Borkmanna6ed3832015-07-30 16:04:22 +020025#include <regex.h>
26#include <fcntl.h>
Daniel Borkmanne306e2c2013-03-20 12:11:47 +000027#include <sys/klog.h>
28#include <sys/types.h>
Daniel Borkmanna6ed3832015-07-30 16:04:22 +020029#include <sys/stat.h>
30
31#define CMD_ACTION_SIZE_BUFFER 10
32#define CMD_ACTION_READ_ALL 3
Daniel Borkmanne306e2c2013-03-20 12:11:47 +000033
34static void get_exec_path(char *tpath, size_t size)
35{
36 char *path;
37 ssize_t len;
38
39 snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
40 tpath[size - 1] = 0;
41
42 path = strdup(tpath);
43 assert(path);
44
45 len = readlink(path, tpath, size);
46 tpath[len] = 0;
47
48 free(path);
49}
50
Alexei Starovoitoved4afd42014-05-15 15:56:38 -070051static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
Daniel Borkmanne306e2c2013-03-20 12:11:47 +000052{
53 int count, i, pc = 0;
54 char tpath[256];
55 struct disassemble_info info;
56 disassembler_ftype disassemble;
57 bfd *bfdf;
58
59 memset(tpath, 0, sizeof(tpath));
60 get_exec_path(tpath, sizeof(tpath));
61
62 bfdf = bfd_openr(tpath, NULL);
63 assert(bfdf);
64 assert(bfd_check_format(bfdf, bfd_object));
65
66 init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
67 info.arch = bfd_get_arch(bfdf);
68 info.mach = bfd_get_mach(bfdf);
69 info.buffer = image;
70 info.buffer_length = len;
71
72 disassemble_init_for_target(&info);
73
74 disassemble = disassembler(bfdf);
75 assert(disassemble);
76
77 do {
78 printf("%4x:\t", pc);
79
80 count = disassemble(pc, &info);
81
82 if (opcodes) {
83 printf("\n\t");
84 for (i = 0; i < count; ++i)
85 printf("%02x ", (uint8_t) image[pc + i]);
86 }
87 printf("\n");
88
89 pc += count;
90 } while(count > 0 && pc < len);
91
92 bfd_close(bfdf);
93}
94
Daniel Borkmanna6ed3832015-07-30 16:04:22 +020095static char *get_klog_buff(unsigned int *klen)
Daniel Borkmanne306e2c2013-03-20 12:11:47 +000096{
Daniel Borkmanna6ed3832015-07-30 16:04:22 +020097 int ret, len;
98 char *buff;
Daniel Borkmanne306e2c2013-03-20 12:11:47 +000099
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200100 len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
Colin Ian King25a54342016-05-05 23:39:33 +0100101 if (len < 0)
102 return NULL;
103
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200104 buff = malloc(len);
105 if (!buff)
106 return NULL;
107
108 ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
109 if (ret < 0) {
110 free(buff);
111 return NULL;
112 }
113
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000114 *klen = ret;
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000115 return buff;
116}
117
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200118static char *get_flog_buff(const char *file, unsigned int *klen)
119{
120 int fd, ret, len;
121 struct stat fi;
122 char *buff;
123
124 fd = open(file, O_RDONLY);
125 if (fd < 0)
126 return NULL;
127
128 ret = fstat(fd, &fi);
129 if (ret < 0 || !S_ISREG(fi.st_mode))
130 goto out;
131
132 len = fi.st_size + 1;
133 buff = malloc(len);
134 if (!buff)
135 goto out;
136
137 memset(buff, 0, len);
138 ret = read(fd, buff, len - 1);
139 if (ret <= 0)
140 goto out_free;
141
142 close(fd);
143 *klen = ret;
144 return buff;
145out_free:
146 free(buff);
147out:
148 close(fd);
149 return NULL;
150}
151
152static char *get_log_buff(const char *file, unsigned int *klen)
153{
154 return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
155}
156
157static void put_log_buff(char *buff)
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000158{
159 free(buff);
160}
161
Andrzej Hajda4de61ba2015-09-25 08:45:43 +0200162static unsigned int get_last_jit_image(char *haystack, size_t hlen,
163 uint8_t *image, size_t ilen)
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000164{
165 char *ptr, *pptr, *tmp;
166 off_t off = 0;
167 int ret, flen, proglen, pass, ulen = 0;
168 regmatch_t pmatch[1];
Alexei Starovoitoved4afd42014-05-15 15:56:38 -0700169 unsigned long base;
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000170 regex_t regex;
171
172 if (hlen == 0)
173 return 0;
174
175 ret = regcomp(&regex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
176 "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
177 assert(ret == 0);
178
179 ptr = haystack;
Daniel Borkmann082739a2015-05-25 14:08:03 +0200180 memset(pmatch, 0, sizeof(pmatch));
181
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000182 while (1) {
183 ret = regexec(&regex, ptr, 1, pmatch, 0);
184 if (ret == 0) {
185 ptr += pmatch[0].rm_eo;
186 off += pmatch[0].rm_eo;
187 assert(off < hlen);
188 } else
189 break;
190 }
191
192 ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
193 ret = sscanf(ptr, "flen=%d proglen=%d pass=%d image=%lx",
Alexei Starovoitoved4afd42014-05-15 15:56:38 -0700194 &flen, &proglen, &pass, &base);
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200195 if (ret != 4) {
196 regfree(&regex);
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000197 return 0;
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200198 }
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000199
200 tmp = ptr = haystack + off;
201 while ((ptr = strtok(tmp, "\n")) != NULL && ulen < ilen) {
202 tmp = NULL;
203 if (!strstr(ptr, "JIT code"))
204 continue;
205 pptr = ptr;
206 while ((ptr = strstr(pptr, ":")))
207 pptr = ptr + 1;
208 ptr = pptr;
209 do {
210 image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
211 if (ptr == pptr || ulen >= ilen) {
212 ulen--;
213 break;
214 }
215 ptr = pptr;
216 } while (1);
217 }
218
219 assert(ulen == proglen);
220 printf("%d bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
221 proglen, pass, flen);
Alexei Starovoitoved4afd42014-05-15 15:56:38 -0700222 printf("%lx + <x>:\n", base);
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000223
224 regfree(&regex);
225 return ulen;
226}
227
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200228static void usage(void)
229{
230 printf("Usage: bpf_jit_disasm [...]\n");
231 printf(" -o Also display related opcodes (default: off).\n");
David Daneyb6518e62017-04-11 14:30:52 -0700232 printf(" -O <file> Write binary image of code to file, don't disassemble to stdout.\n");
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200233 printf(" -f <file> Read last image dump from file or stdin (default: klog).\n");
234 printf(" -h Display this help.\n");
235}
236
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000237int main(int argc, char **argv)
238{
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200239 unsigned int len, klen, opt, opcodes = 0;
Alexei Starovoitov9bb1a202014-05-15 15:56:39 -0700240 static uint8_t image[32768];
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200241 char *kbuff, *file = NULL;
David Daneyb6518e62017-04-11 14:30:52 -0700242 char *ofile = NULL;
243 int ofd;
244 ssize_t nr;
245 uint8_t *pos;
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000246
David Daneyb6518e62017-04-11 14:30:52 -0700247 while ((opt = getopt(argc, argv, "of:O:")) != -1) {
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200248 switch (opt) {
249 case 'o':
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000250 opcodes = 1;
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200251 break;
David Daneyb6518e62017-04-11 14:30:52 -0700252 case 'O':
253 ofile = optarg;
254 break;
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200255 case 'f':
256 file = optarg;
257 break;
258 default:
259 usage();
260 return -1;
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000261 }
262 }
263
264 bfd_init();
265 memset(image, 0, sizeof(image));
266
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200267 kbuff = get_log_buff(file, &klen);
268 if (!kbuff) {
269 fprintf(stderr, "Could not retrieve log buffer!\n");
270 return -1;
271 }
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000272
Alexei Starovoitoved4afd42014-05-15 15:56:38 -0700273 len = get_last_jit_image(kbuff, klen, image, sizeof(image));
David Daneyb6518e62017-04-11 14:30:52 -0700274 if (len <= 0) {
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200275 fprintf(stderr, "No JIT image found!\n");
David Daneyb6518e62017-04-11 14:30:52 -0700276 goto done;
277 }
278 if (!ofile) {
279 get_asm_insns(image, len, opcodes);
280 goto done;
281 }
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000282
David Daneyb6518e62017-04-11 14:30:52 -0700283 ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
284 if (ofd < 0) {
285 fprintf(stderr, "Could not open file %s for writing: ", ofile);
286 perror(NULL);
287 goto done;
288 }
289 pos = image;
290 do {
291 nr = write(ofd, pos, len);
292 if (nr < 0) {
293 fprintf(stderr, "Could not write data to %s: ", ofile);
294 perror(NULL);
295 goto done;
296 }
297 len -= nr;
298 pos += nr;
299 } while (len);
300 close(ofd);
301
302done:
Daniel Borkmanna6ed3832015-07-30 16:04:22 +0200303 put_log_buff(kbuff);
Daniel Borkmanne306e2c2013-03-20 12:11:47 +0000304 return 0;
305}