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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Minimal BPF JIT image disassembler4 *5 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for6 * debugging or verification purposes.7 *8 * To get the disassembly of the JIT code, do the following:9 *10 * 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`11 * 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)12 * 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code13 *14 * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>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>25#include <regex.h>26#include <fcntl.h>27#include <sys/klog.h>28#include <sys/types.h>29#include <sys/stat.h>30#include <limits.h>31#include <tools/dis-asm-compat.h>32 33#define CMD_ACTION_SIZE_BUFFER 1034#define CMD_ACTION_READ_ALL 335 36static void get_exec_path(char *tpath, size_t size)37{38 char *path;39 ssize_t len;40 41 snprintf(tpath, size, "/proc/%d/exe", (int) getpid());42 tpath[size - 1] = 0;43 44 path = strdup(tpath);45 assert(path);46 47 len = readlink(path, tpath, size);48 tpath[len] = 0;49 50 free(path);51}52 53static void get_asm_insns(uint8_t *image, size_t len, int opcodes)54{55 int count, i, pc = 0;56 char tpath[PATH_MAX];57 struct disassemble_info info;58 disassembler_ftype disassemble;59 bfd *bfdf;60 61 memset(tpath, 0, sizeof(tpath));62 get_exec_path(tpath, sizeof(tpath));63 64 bfdf = bfd_openr(tpath, NULL);65 assert(bfdf);66 assert(bfd_check_format(bfdf, bfd_object));67 68 init_disassemble_info_compat(&info, stdout,69 (fprintf_ftype) fprintf,70 fprintf_styled);71 info.arch = bfd_get_arch(bfdf);72 info.mach = bfd_get_mach(bfdf);73 info.buffer = image;74 info.buffer_length = len;75 76 disassemble_init_for_target(&info);77 78#ifdef DISASM_FOUR_ARGS_SIGNATURE79 disassemble = disassembler(info.arch,80 bfd_big_endian(bfdf),81 info.mach,82 bfdf);83#else84 disassemble = disassembler(bfdf);85#endif86 assert(disassemble);87 88 do {89 printf("%4x:\t", pc);90 91 count = disassemble(pc, &info);92 93 if (opcodes) {94 printf("\n\t");95 for (i = 0; i < count; ++i)96 printf("%02x ", (uint8_t) image[pc + i]);97 }98 printf("\n");99 100 pc += count;101 } while(count > 0 && pc < len);102 103 bfd_close(bfdf);104}105 106static char *get_klog_buff(unsigned int *klen)107{108 int ret, len;109 char *buff;110 111 len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);112 if (len < 0)113 return NULL;114 115 buff = malloc(len);116 if (!buff)117 return NULL;118 119 ret = klogctl(CMD_ACTION_READ_ALL, buff, len);120 if (ret < 0) {121 free(buff);122 return NULL;123 }124 125 *klen = ret;126 return buff;127}128 129static char *get_flog_buff(const char *file, unsigned int *klen)130{131 int fd, ret, len;132 struct stat fi;133 char *buff;134 135 fd = open(file, O_RDONLY);136 if (fd < 0)137 return NULL;138 139 ret = fstat(fd, &fi);140 if (ret < 0 || !S_ISREG(fi.st_mode))141 goto out;142 143 len = fi.st_size + 1;144 buff = malloc(len);145 if (!buff)146 goto out;147 148 memset(buff, 0, len);149 ret = read(fd, buff, len - 1);150 if (ret <= 0)151 goto out_free;152 153 close(fd);154 *klen = ret;155 return buff;156out_free:157 free(buff);158out:159 close(fd);160 return NULL;161}162 163static char *get_log_buff(const char *file, unsigned int *klen)164{165 return file ? get_flog_buff(file, klen) : get_klog_buff(klen);166}167 168static void put_log_buff(char *buff)169{170 free(buff);171}172 173static uint8_t *get_last_jit_image(char *haystack, size_t hlen,174 unsigned int *ilen)175{176 char *ptr, *pptr, *tmp;177 off_t off = 0;178 unsigned int proglen;179 int ret, flen, pass, ulen = 0;180 regmatch_t pmatch[1];181 unsigned long base;182 regex_t regex;183 uint8_t *image;184 185 if (hlen == 0)186 return NULL;187 188 ret = regcomp(®ex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "189 "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);190 assert(ret == 0);191 192 ptr = haystack;193 memset(pmatch, 0, sizeof(pmatch));194 195 while (1) {196 ret = regexec(®ex, ptr, 1, pmatch, 0);197 if (ret == 0) {198 ptr += pmatch[0].rm_eo;199 off += pmatch[0].rm_eo;200 assert(off < hlen);201 } else202 break;203 }204 205 ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);206 ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",207 &flen, &proglen, &pass, &base);208 if (ret != 4) {209 regfree(®ex);210 return NULL;211 }212 if (proglen > 1000000) {213 printf("proglen of %d too big, stopping\n", proglen);214 return NULL;215 }216 217 image = malloc(proglen);218 if (!image) {219 printf("Out of memory\n");220 return NULL;221 }222 memset(image, 0, proglen);223 224 tmp = ptr = haystack + off;225 while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {226 tmp = NULL;227 if (!strstr(ptr, "JIT code"))228 continue;229 pptr = ptr;230 while ((ptr = strstr(pptr, ":")))231 pptr = ptr + 1;232 ptr = pptr;233 do {234 image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);235 if (ptr == pptr) {236 ulen--;237 break;238 }239 if (ulen >= proglen)240 break;241 ptr = pptr;242 } while (1);243 }244 245 assert(ulen == proglen);246 printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",247 proglen, pass, flen);248 printf("%lx + <x>:\n", base);249 250 regfree(®ex);251 *ilen = ulen;252 return image;253}254 255static void usage(void)256{257 printf("Usage: bpf_jit_disasm [...]\n");258 printf(" -o Also display related opcodes (default: off).\n");259 printf(" -O <file> Write binary image of code to file, don't disassemble to stdout.\n");260 printf(" -f <file> Read last image dump from file or stdin (default: klog).\n");261 printf(" -h Display this help.\n");262}263 264int main(int argc, char **argv)265{266 unsigned int len, klen, opt, opcodes = 0;267 char *kbuff, *file = NULL;268 char *ofile = NULL;269 int ofd;270 ssize_t nr;271 uint8_t *pos;272 uint8_t *image = NULL;273 274 while ((opt = getopt(argc, argv, "of:O:")) != -1) {275 switch (opt) {276 case 'o':277 opcodes = 1;278 break;279 case 'O':280 ofile = optarg;281 break;282 case 'f':283 file = optarg;284 break;285 default:286 usage();287 return -1;288 }289 }290 291 bfd_init();292 293 kbuff = get_log_buff(file, &klen);294 if (!kbuff) {295 fprintf(stderr, "Could not retrieve log buffer!\n");296 return -1;297 }298 299 image = get_last_jit_image(kbuff, klen, &len);300 if (!image) {301 fprintf(stderr, "No JIT image found!\n");302 goto done;303 }304 if (!ofile) {305 get_asm_insns(image, len, opcodes);306 goto done;307 }308 309 ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);310 if (ofd < 0) {311 fprintf(stderr, "Could not open file %s for writing: ", ofile);312 perror(NULL);313 goto done;314 }315 pos = image;316 do {317 nr = write(ofd, pos, len);318 if (nr < 0) {319 fprintf(stderr, "Could not write data to %s: ", ofile);320 perror(NULL);321 goto done;322 }323 len -= nr;324 pos += nr;325 } while (len);326 close(ofd);327 328done:329 put_log_buff(kbuff);330 free(image);331 return 0;332}333