src/bpf_hla_parser.y

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2012 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 <stdint.h>
  15 #include <errno.h>
  16
  17 #include "bpf.h"
  18 #include "bpf_hla_parser.tab.h"
  19 #include "bpf_symtab.h"
  20 #include "xmalloc.h"
  21 #include "xutils.h"
  22 #include "built_in.h"
  23 #include "die.h"
  24
  25 #if 0
  26 example:
  27 {
  28   def x;
  29   def y;
  30   x = pkt(12, 2);
  31   ret x;
  32 }
  33 #endif
  34
  35 int compile_hla_filter(char *file, int verbose, int debug);
  36
  37 #define YYERROR_VERBOSE         0
  38 #define YYDEBUG                 0
  39 #define YYENABLE_NLS            1
  40 #define YYLTYPE_IS_TRIVIAL      1
  41 #define ENABLE_NLS              1
  42
  43 extern FILE *zzin;
  44 extern int zzlex(void);
  45 extern void zzerror(const char *);
  46 extern int zzlineno;
  47 extern char *zztext;
  48
  49 %}
  50
  51 %union {
  52         int idx;
  53         long int number;
  54 }
  55
  56 %token K_NAME K_DEF K_PKT K_RET K_IF K_ELIF K_ELSE
  57 %token '(' ')' '{' '}' '=' ';' '+' '-' '&' '|' '^' '!' '<' '>' '*' '/' '%' ','
  58
  59 %token number_hex number_dec number_oct number_bin
  60
  61 %type <idx> K_NAME var
  62 %type <number> number_hex number_dec number_oct number_bin number
  63
  64 %%
  65
  66 program
  67         : '{' declaration_list statement_list '}'
  68         ;
  69
  70 declaration_list
  71         : declaration ';' declaration_list
  72         | /* empty */
  73         ;
  74
  75 statement_list
  76         : statement ';' statement_list
  77         | /* empty */
  78         ;
  79
  80 declaration
  81         : K_DEF K_NAME {
  82                 if (bpf_symtab_declared($2)) {
  83                         panic("Variable \"%s\" already declared (l%d)\n",
  84                               bpf_symtab_name($2), zzlineno);
  85                 } else {
  86                         printf("; @var %s\n", bpf_symtab_name($2));
  87                         bpf_symtab_declare($2);
  88                 }}
  89         ;
  90
  91 statement
  92         : assignment
  93         | return
  94         ;
  95
  96 return
  97         : K_RET { printf("ret a\n"); }
  98         | K_RET number { printf("ret #%ld\n", $2); }
  99         | K_RET var { printf("ret a\n"); }
 100         ;
 101
 102 assignment
 103         : var '=' expression { printf("; @asn %s\n", bpf_symtab_name($1)); }
 104         | var '=' K_PKT '(' number ',' number ')' {
 105                         switch ($7) {
 106                         case 1:
 107                                 printf("ldb [%ld]\n", $5);
 108                                 break;
 109                         case 2:
 110                                 printf("ldh [%ld]\n", $5);
 111                                 break;
 112                         case 4:
 113                                 printf("ld [%ld]\n", $5);
 114                                 break;
 115                         default:
 116                                 panic("Invalid argument (l%d)\n", zzlineno);
 117                         }
 118                 }
 119         ;
 120
 121 expression
 122         : term
 123         | term '+' term { printf("; @+\n"); }
 124         | term '-' term { printf("; @-\n"); }
 125         ;
 126
 127 term
 128         : number { printf("; @num %ld\n", $1); }
 129         | var { printf("; @var %s\n", bpf_symtab_name($1)); }
 130         | '(' expression ')'
 131         ;
 132
 133 var
 134         : K_NAME {
 135                 if (!bpf_symtab_declared($1))
 136                         panic("Variable \"%s\" not declared (l%d)\n",
 137                               bpf_symtab_name($1), zzlineno);
 138                 $$ = $1; }
 139         ;
 140
 141 number
 142         : number_dec { $$ = $1; }
 143         | number_hex { $$ = $1; }
 144         | number_oct { $$ = $1; }
 145         | number_bin { $$ = $1; }
 146         ;
 147
 148 %%
 149
 150 static void stage_1_compile(void)
 151 {
 152         zzparse();
 153 }
 154
 155 int compile_hla_filter(char *file, int verbose, int debug)
 156 {
 157         int fd;
 158         fpos_t pos;
 159         char file_tmp[128];
 160
 161         if (!strncmp("-", file, strlen("-")))
 162                 zzin = stdin;
 163         else
 164                 zzin = fopen(file, "r");
 165         if (!zzin)
 166                 panic("Cannot open file!\n");
 167         if (!debug) {
 168                 fd = dup(fileno(stdout));
 169
 170                 slprintf(file_tmp, sizeof(file_tmp), ".%s", file);
 171                 if (freopen(file_tmp, "w", stdout) == NULL)
 172                         panic("Cannot reopen file!\n");
 173         }
 174
 175         stage_1_compile();
 176
 177         if (!debug) {
 178                 fflush(stdout);
 179                 dup2(fd, fileno(stdout));
 180
 181                 close(fd);
 182                 clearerr(stdout);
 183                 fsetpos(stdout, &pos);
 184         }
 185
 186         fclose(zzin);
 187
 188         bpf_symtab_cleanup();
 189         if (debug)
 190                 die();
 191
 192         return 0;
 193 }
 194
 195 void zzerror(const char *err)
 196 {
 197         panic("Syntax error at line %d: %s! %s!\n",
 198               zzlineno, zztext, err);
 199 }