src/bpf_parser.y

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2011 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   5  * Swiss federal institute of technology (ETH Zurich)
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 %{
  10
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <stdbool.h>
  14 #include <signal.h>
  15 #include <stdint.h>
  16 #include <errno.h>
  17
  18 #include "bpf.h"
  19 #include "xmalloc.h"
  20 #include "bpf_parser.tab.h"
  21 #include "built_in.h"
  22 #include "die.h"
  23
  24 #define MAX_INSTRUCTIONS        4096
  25
  26 int compile_filter(char *file, int verbose, int bypass);
  27
  28 static int curr_instr = 0;
  29
  30 static struct sock_filter out[MAX_INSTRUCTIONS];
  31
  32 static char *labels[MAX_INSTRUCTIONS];
  33
  34 static char *labels_jt[MAX_INSTRUCTIONS];
  35 static char *labels_jf[MAX_INSTRUCTIONS];
  36 static char *labels_k[MAX_INSTRUCTIONS];
  37
  38 #define YYERROR_VERBOSE         0
  39 #define YYDEBUG                 0
  40 #define YYENABLE_NLS            1
  41 #define YYLTYPE_IS_TRIVIAL      1
  42 #define ENABLE_NLS              1
  43
  44 extern FILE *yyin;
  45 extern int yylex(void);
  46 extern void yyerror(const char *);
  47 extern int yylineno;
  48 extern char *yytext;
  49
  50 static inline void set_curr_instr(uint16_t code, uint8_t jt, uint8_t jf, uint32_t k)
  51 {
  52         if (curr_instr >= MAX_INSTRUCTIONS)
  53                 panic("Exceeded maximal number of instructions!\n");
  54
  55         out[curr_instr].code = code;
  56         out[curr_instr].jt = jt;
  57         out[curr_instr].jf = jf;
  58         out[curr_instr].k = k;
  59
  60         curr_instr++;
  61 }
  62
  63 static inline void set_curr_label(char *label)
  64 {
  65         if (curr_instr >= MAX_INSTRUCTIONS)
  66                 panic("Exceeded maximal number of instructions!\n");
  67
  68         labels[curr_instr] = label;
  69 }
  70
  71 #define JTL 1
  72 #define JFL 2
  73 #define JKL 3
  74
  75 static inline void set_jmp_label(char *label, int which)
  76 {
  77         if (curr_instr >= MAX_INSTRUCTIONS)
  78                 panic("Exceeded maximal number of instructions!\n");
  79
  80         bug_on(which != JTL && which != JFL && which != JKL);
  81
  82         if (which == JTL)
  83                 labels_jt[curr_instr] = label;
  84         else if (which == JFL)
  85                 labels_jf[curr_instr] = label;
  86         else
  87                 labels_k[curr_instr] = label;
  88 }
  89
  90 static int find_intr_offset_or_panic(char *label_to_search)
  91 {
  92         int i, max = curr_instr, ret = -ENOENT;
  93
  94         bug_on(!label_to_search);
  95
  96         for (i = 0; i < max; ++i) {
  97                 if (labels[i] != NULL) {
  98                         /* Both are \0-terminated! */
  99                         if (!strcmp(label_to_search, labels[i])) {
 100                                 ret = i;
 101                                 break;
 102                         }
 103                 }
 104         }
 105
 106         if (ret == -ENOENT)
 107                 panic("No such label!\n");
 108
 109         return ret;
 110 }
 111
 112 %}
 113
 114 %union {
 115         char *label;
 116         long int number;
 117 }
 118
 119 %token OP_LDB OP_LDH OP_LD OP_LDX OP_ST OP_STX OP_JMP OP_JEQ OP_JGT OP_JGE
 120 %token OP_JSET OP_ADD OP_SUB OP_MUL OP_DIV OP_AND OP_OR OP_XOR OP_LSH OP_RSH
 121 %token OP_RET OP_TAX OP_TXA OP_LDXB OP_MOD OP_NEG K_PKT_LEN K_PROTO K_TYPE
 122 %token K_NLATTR K_NLATTR_NEST K_MARK K_QUEUE K_HATYPE K_RXHASH K_CPU K_IFIDX
 123
 124 %token ':' ',' '[' ']' '(' ')' 'x' 'a' '+' 'M' '*' '&' '#'
 125
 126 %token number_hex number_dec number_oct number_bin label
 127
 128 %type <number> number_hex number_dec number_oct number_bin number
 129 %type <label> label
 130
 131 %%
 132
 133 prog
 134         : line
 135         | prog line
 136         ;
 137
 138 line
 139         : instr
 140         | labeled_instr
 141         ;
 142
 143 labeled_instr
 144         : do_label instr
 145         ;
 146
 147 instr
 148         : do_ldb
 149         | do_ldh
 150         | do_ld
 151         | do_ldx
 152         | do_st
 153         | do_stx
 154         | do_jmp
 155         | do_jeq
 156         | do_jgt
 157         | do_jge
 158         | do_jset
 159         | do_add
 160         | do_sub
 161         | do_mul
 162         | do_div
 163         | do_mod
 164         | do_neg
 165         | do_and
 166         | do_or
 167         | do_xor
 168         | do_lsh
 169         | do_rsh
 170         | do_ret
 171         | do_tax
 172         | do_txa
 173         ;
 174
 175 number
 176         : number_dec { $$ = $1; }
 177         | number_hex { $$ = $1; }
 178         | number_oct { $$ = $1; }
 179         | number_bin { $$ = $1; }
 180         ;
 181
 182 do_label
 183         : label ':' { set_curr_label($1); }
 184         ;
 185
 186 do_ldb
 187         : OP_LDB '[' 'x' '+' number ']' {
 188                 set_curr_instr(BPF_LD | BPF_B | BPF_IND, 0, 0, $5); }
 189         | OP_LDB '[' number ']' {
 190                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0, $3); }
 191         | OP_LDB '#' K_PROTO {
 192                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 193                                SKF_AD_OFF + SKF_AD_PROTOCOL); }
 194         | OP_LDB '#' K_TYPE {
 195                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 196                                SKF_AD_OFF + SKF_AD_PKTTYPE); }
 197         | OP_LDB '#' K_IFIDX {
 198                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 199                                SKF_AD_OFF + SKF_AD_IFINDEX); }
 200         | OP_LDB '#' K_NLATTR {
 201                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 202                                SKF_AD_OFF + SKF_AD_NLATTR); }
 203         | OP_LDB '#' K_NLATTR_NEST {
 204                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 205                                SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
 206         | OP_LDB '#' K_MARK {
 207                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 208                                SKF_AD_OFF + SKF_AD_MARK); }
 209         | OP_LDB '#' K_QUEUE {
 210                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 211                                SKF_AD_OFF + SKF_AD_QUEUE); }
 212         | OP_LDB '#' K_HATYPE {
 213                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 214                                SKF_AD_OFF + SKF_AD_HATYPE); }
 215         | OP_LDB '#' K_RXHASH {
 216                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 217                                SKF_AD_OFF + SKF_AD_RXHASH); }
 218         | OP_LDB '#' K_CPU {
 219                 set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
 220                                SKF_AD_OFF + SKF_AD_CPU); }
 221         ;
 222
 223 do_ldh
 224         : OP_LDH '[' 'x' '+' number ']' {
 225                 set_curr_instr(BPF_LD | BPF_H | BPF_IND, 0, 0, $5); }
 226         | OP_LDH '[' number ']' {
 227                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0, $3); }
 228         | OP_LDH '#' K_PROTO {
 229                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 230                                SKF_AD_OFF + SKF_AD_PROTOCOL); }
 231         | OP_LDH '#' K_TYPE {
 232                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 233                                SKF_AD_OFF + SKF_AD_PKTTYPE); }
 234         | OP_LDH '#' K_IFIDX {
 235                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 236                                SKF_AD_OFF + SKF_AD_IFINDEX); }
 237         | OP_LDH '#' K_NLATTR {
 238                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 239                                SKF_AD_OFF + SKF_AD_NLATTR); }
 240         | OP_LDH '#' K_NLATTR_NEST {
 241                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 242                                SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
 243         | OP_LDH '#' K_MARK {
 244                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 245                                SKF_AD_OFF + SKF_AD_MARK); }
 246         | OP_LDH '#' K_QUEUE {
 247                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 248                                SKF_AD_OFF + SKF_AD_QUEUE); }
 249         | OP_LDH '#' K_HATYPE {
 250                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 251                                SKF_AD_OFF + SKF_AD_HATYPE); }
 252         | OP_LDH '#' K_RXHASH {
 253                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 254                                SKF_AD_OFF + SKF_AD_RXHASH); }
 255         | OP_LDH '#' K_CPU {
 256                 set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
 257                                SKF_AD_OFF + SKF_AD_CPU); }
 258         ;
 259
 260 do_ld
 261         : OP_LD '#' number {
 262                 set_curr_instr(BPF_LD | BPF_IMM, 0, 0, $3); }
 263         | OP_LD '#' K_PKT_LEN {
 264                 set_curr_instr(BPF_LD | BPF_W | BPF_LEN, 0, 0, 0); }
 265         | OP_LD '#' K_PROTO {
 266                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 267                                SKF_AD_OFF + SKF_AD_PROTOCOL); }
 268         | OP_LD '#' K_TYPE {
 269                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 270                                SKF_AD_OFF + SKF_AD_PKTTYPE); }
 271         | OP_LD '#' K_IFIDX {
 272                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 273                                SKF_AD_OFF + SKF_AD_IFINDEX); }
 274         | OP_LD '#' K_NLATTR {
 275                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 276                                SKF_AD_OFF + SKF_AD_NLATTR); }
 277         | OP_LD '#' K_NLATTR_NEST {
 278                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 279                                SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
 280         | OP_LD '#' K_MARK {
 281                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 282                                SKF_AD_OFF + SKF_AD_MARK); }
 283         | OP_LD '#' K_QUEUE {
 284                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 285                                SKF_AD_OFF + SKF_AD_QUEUE); }
 286         | OP_LD '#' K_HATYPE {
 287                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 288                                SKF_AD_OFF + SKF_AD_HATYPE); }
 289         | OP_LD '#' K_RXHASH {
 290                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 291                                SKF_AD_OFF + SKF_AD_RXHASH); }
 292         | OP_LD '#' K_CPU {
 293                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
 294                                SKF_AD_OFF + SKF_AD_CPU); }
 295         | OP_LD 'M' '[' number ']' {
 296                 set_curr_instr(BPF_LD | BPF_MEM, 0, 0, $4); }
 297         | OP_LD '[' 'x' '+' number ']' {
 298                 set_curr_instr(BPF_LD | BPF_W | BPF_IND, 0, 0, $5); }
 299         | OP_LD '[' number ']' {
 300                 set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0, $3); }
 301         ;
 302
 303 do_ldx
 304         : OP_LDX '#' number {
 305                 set_curr_instr(BPF_LDX | BPF_IMM, 0, 0, $3); }
 306         | OP_LDX 'M' '[' number ']' {
 307                 set_curr_instr(BPF_LDX | BPF_MEM, 0, 0, $4); }
 308         | OP_LDXB number '*' '(' '[' number ']' '&' number ')' {
 309                 if ($2 != 4 || $9 != 0xf) {
 310                         panic("ldxb offset not supported!\n");
 311                 } else {
 312                         set_curr_instr(BPF_LDX | BPF_MSH | BPF_B, 0, 0, $6); } }
 313         | OP_LDX number '*' '(' '[' number ']' '&' number ')' {
 314                 if ($2 != 4 || $9 != 0xf) {
 315                         panic("ldxb offset not supported!\n");
 316                 } else {
 317                         set_curr_instr(BPF_LDX | BPF_MSH | BPF_B, 0, 0, $6); } }
 318         ;
 319
 320 do_st
 321         : OP_ST 'M' '[' number ']' {
 322                 set_curr_instr(BPF_ST, 0, 0, $4); }
 323         ;
 324
 325 do_stx
 326         : OP_STX 'M' '[' number ']' {
 327                 set_curr_instr(BPF_STX, 0, 0, $4); }
 328         ;
 329
 330 do_jmp
 331         : OP_JMP label {
 332                 set_jmp_label($2, JKL);
 333                 set_curr_instr(BPF_JMP | BPF_JA, 0, 0, 0); }
 334         ;
 335
 336 do_jeq
 337         : OP_JEQ '#' number ',' label ',' label {
 338                 set_jmp_label($5, JTL);
 339                 set_jmp_label($7, JFL);
 340                 set_curr_instr(BPF_JMP | BPF_JEQ | BPF_K, 0, 0, $3); }
 341         | OP_JEQ 'x' ',' label ',' label {
 342                 set_jmp_label($4, JTL);
 343                 set_jmp_label($6, JFL);
 344                 set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
 345         ;
 346
 347 do_jgt
 348         : OP_JGT '#' number ',' label ',' label {
 349                 set_jmp_label($5, JTL);
 350                 set_jmp_label($7, JFL);
 351                 set_curr_instr(BPF_JMP | BPF_JGT | BPF_K, 0, 0, $3); }
 352         | OP_JGT 'x' ',' label ',' label {
 353                 set_jmp_label($4, JTL);
 354                 set_jmp_label($6, JFL);
 355                 set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
 356         ;
 357
 358 do_jge
 359         : OP_JGE '#' number ',' label ',' label {
 360                 set_jmp_label($5, JTL);
 361                 set_jmp_label($7, JFL);
 362                 set_curr_instr(BPF_JMP | BPF_JGE | BPF_K, 0, 0, $3); }
 363         | OP_JGE 'x' ',' label ',' label {
 364                 set_jmp_label($4, JTL);
 365                 set_jmp_label($6, JFL);
 366                 set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
 367         ;
 368
 369 do_jset
 370         : OP_JSET '#' number ',' label ',' label {
 371                 set_jmp_label($5, JTL);
 372                 set_jmp_label($7, JFL);
 373                 set_curr_instr(BPF_JMP | BPF_JSET | BPF_K, 0, 0, $3); }
 374         | OP_JSET 'x' ',' label ',' label {
 375                 set_jmp_label($4, JTL);
 376                 set_jmp_label($6, JFL);
 377                 set_curr_instr(BPF_JMP | BPF_JSET | BPF_X, 0, 0, 0); }
 378         ;
 379
 380 do_add
 381         : OP_ADD '#' number {
 382                 set_curr_instr(BPF_ALU | BPF_ADD | BPF_K, 0, 0, $3); }
 383         | OP_ADD 'x' {
 384                 set_curr_instr(BPF_ALU | BPF_ADD | BPF_X, 0, 0, 0); }
 385         ;
 386
 387 do_sub
 388         : OP_SUB '#' number {
 389                 set_curr_instr(BPF_ALU | BPF_SUB | BPF_K, 0, 0, $3); }
 390         | OP_SUB 'x' {
 391                 set_curr_instr(BPF_ALU | BPF_SUB | BPF_X, 0, 0, 0); }
 392         ;
 393
 394 do_mul
 395         : OP_MUL '#' number {
 396                 set_curr_instr(BPF_ALU | BPF_MUL | BPF_K, 0, 0, $3); }
 397         | OP_MUL 'x' {
 398                 set_curr_instr(BPF_ALU | BPF_MUL | BPF_X, 0, 0, 0); }
 399         ;
 400
 401 do_div
 402         : OP_DIV '#' number {
 403                 set_curr_instr(BPF_ALU | BPF_DIV | BPF_K, 0, 0, $3); }
 404         | OP_DIV 'x' {
 405                 set_curr_instr(BPF_ALU | BPF_DIV | BPF_X, 0, 0, 0); }
 406         ;
 407
 408 do_mod
 409         : OP_MOD '#' number {
 410                 set_curr_instr(BPF_ALU | BPF_MOD | BPF_K, 0, 0, $3); }
 411         | OP_MOD 'x' {
 412                 set_curr_instr(BPF_ALU | BPF_MOD | BPF_X, 0, 0, 0); }
 413         ;
 414
 415 do_neg
 416         : OP_NEG {
 417                 set_curr_instr(BPF_ALU | BPF_NEG, 0, 0, 0); }
 418         ;
 419
 420 do_and
 421         : OP_AND '#' number {
 422                 set_curr_instr(BPF_ALU | BPF_AND | BPF_K, 0, 0, $3); }
 423         | OP_AND 'x' {
 424                 set_curr_instr(BPF_ALU | BPF_AND | BPF_X, 0, 0, 0); }
 425         ;
 426
 427 do_or
 428         : OP_OR '#' number {
 429                 set_curr_instr(BPF_ALU | BPF_OR | BPF_K, 0, 0, $3); }
 430         | OP_OR 'x' {
 431                 set_curr_instr(BPF_ALU | BPF_OR | BPF_X, 0, 0, 0); }
 432         ;
 433
 434 do_xor
 435         : OP_XOR '#' number {
 436                 set_curr_instr(BPF_ALU | BPF_XOR | BPF_K, 0, 0, $3); }
 437         | OP_XOR 'x' {
 438                 set_curr_instr(BPF_ALU | BPF_XOR | BPF_X, 0, 0, 0); }
 439         ;
 440
 441 do_lsh
 442         : OP_LSH '#' number {
 443                 set_curr_instr(BPF_ALU | BPF_LSH | BPF_K, 0, 0, $3); }
 444         | OP_LSH 'x' {
 445                 set_curr_instr(BPF_ALU | BPF_LSH | BPF_X, 0, 0, 0); }
 446         ;
 447
 448 do_rsh
 449         : OP_RSH '#' number {
 450                 set_curr_instr(BPF_ALU | BPF_RSH | BPF_K, 0, 0, $3); }
 451         | OP_RSH 'x' {
 452                 set_curr_instr(BPF_ALU | BPF_RSH | BPF_X, 0, 0, 0); }
 453         ;
 454
 455 do_ret
 456         : OP_RET 'a' {
 457                 set_curr_instr(BPF_RET | BPF_A, 0, 0, 0); }
 458         | OP_RET '#' number {
 459                 set_curr_instr(BPF_RET | BPF_K, 0, 0, $3); }
 460         ;
 461
 462 do_tax
 463         : OP_TAX {
 464                 set_curr_instr(BPF_MISC | BPF_TAX, 0, 0, 0); }
 465         ;
 466
 467 do_txa
 468         : OP_TXA {
 469                 set_curr_instr(BPF_MISC | BPF_TXA, 0, 0, 0); }
 470         ;
 471
 472 %%
 473
 474 static void stage_1_inline(void)
 475 {
 476         yyparse();
 477 }
 478
 479 static void stage_2_label_reduce(void)
 480 {
 481         int i, max = curr_instr, off;
 482
 483         /* 1. reduce k jumps */
 484         for (i = 0; i < max; ++i) {
 485                 if (labels_k[i] != NULL) {
 486                         off = find_intr_offset_or_panic(labels_k[i]);
 487                         out[i].k = (uint32_t) (off - i - 1);
 488                 }
 489         }
 490
 491         /* 1. reduce jt jumps */
 492         for (i = 0; i < max; ++i) {
 493                 if (labels_jt[i] != NULL) {
 494                         off = find_intr_offset_or_panic(labels_jt[i]);
 495                         out[i].jt = (uint8_t) (off - i -1);
 496                 }
 497         }
 498
 499         /* 1. reduce jf jumps */
 500         for (i = 0; i < max; ++i) {
 501                 if (labels_jf[i] != NULL) {
 502                         off = find_intr_offset_or_panic(labels_jf[i]);
 503                         out[i].jf = (uint8_t) (off - i - 1);
 504                 }
 505         }
 506 }
 507
 508 int compile_filter(char *file, int verbose, int bypass)
 509 {
 510         int i;
 511         struct sock_fprog res;
 512
 513         if (!strncmp("-", file, strlen("-")))
 514                 yyin = stdin;
 515         else
 516                 yyin = fopen(file, "r");
 517         if (!yyin)
 518                 panic("Cannot open file!\n");
 519
 520         memset(out, 0, sizeof(out));
 521         memset(labels, 0, sizeof(labels));
 522         memset(labels_jf, 0, sizeof(labels_jf));
 523         memset(labels_jt, 0, sizeof(labels_jt));
 524         memset(labels_k, 0, sizeof(labels_k));
 525
 526         stage_1_inline();
 527         stage_2_label_reduce();
 528
 529         res.filter = out;
 530         res.len = curr_instr;
 531
 532         if (verbose) {
 533                 printf("Generated program:\n");
 534                 bpf_dump_all(&res);
 535         }
 536
 537         if (!bypass) {
 538                 if (verbose) {
 539                         printf("Validating: ");
 540                         fflush(stdout);
 541                 }
 542
 543                 if (bpf_validate(&res) == 0) {
 544                         if (verbose)
 545                                 whine("Semantic error! BPF validation "
 546                                       "failed!\n");
 547                         else
 548                                 panic("Semantic error! BPF validation failed! "
 549                                       "Try -V for debugging output!\n");
 550                 } else if (verbose) {
 551                         printf("is runnable!\n");
 552                 }
 553         }
 554
 555         if (verbose)
 556                 printf("Result:\n");
 557         for (i = 0; i < res.len; ++i) {
 558                 printf("{ 0x%x, %u, %u, 0x%08x },\n",
 559                        res.filter[i].code, res.filter[i].jt,
 560                        res.filter[i].jf, res.filter[i].k);
 561                 if (labels[i] != NULL)
 562                         xfree(labels[i]);
 563                 if (labels_jt[i] != NULL)
 564                         xfree(labels_jt[i]);
 565                 if (labels_jf[i] != NULL)
 566                         xfree(labels_jf[i]);
 567                 if (labels_k[i] != NULL)
 568                         xfree(labels_k[i]);
 569         }
 570
 571         fclose(yyin);
 572         return 0;
 573 }
 574
 575 void yyerror(const char *err)
 576 {
 577         panic("Syntax error at line %d: %s! %s!\n",
 578               yylineno, yytext, err);
 579 }