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     TODO:
  11         - intermediate representation
  12         - code optimization (symbolic reduction?)
  13         - linearization (jumps, etc)
  14         - bpf emitter
  15  */
  16
  17 %{
  18
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <stdbool.h>
  22 #include <stdint.h>
  23 #include <errno.h>
  24
  25 #include "bpf.h"
  26 #include "bpf_hla_parser.tab.h"
  27 #include "bpf_symtab.h"
  28 #include "xmalloc.h"
  29 #include "xutils.h"
  30 #include "built_in.h"
  31 #include "die.h"
  32
  33 #define YYERROR_VERBOSE         0
  34 #define YYDEBUG                 0
  35 #define YYENABLE_NLS            1
  36 #define YYLTYPE_IS_TRIVIAL      1
  37 #define ENABLE_NLS              1
  38
  39 extern FILE *zzin;
  40 extern int zzlex(void);
  41 extern void zzerror(const char *);
  42 extern int zzlineno;
  43 extern char *zztext;
  44
  45 int compile_hla_filter(char *file, int verbose, int debug);
  46
  47 static unsigned int num_vars = 0;
  48 static unsigned int num_ifs = 0;
  49
  50 %}
  51
  52 %union {
  53         int idx;
  54         long int number;
  55 }
  56
  57 %token K_NAME K_DEF K_PKT K_RET K_IF K_ELIF K_ELSE
  58 %token K_MACRO_IPV4 K_MACRO_IPV6 K_MACRO_IP K_MACRO_UDP K_MACRO_TCP
  59
  60 %token '(' ')' '{' '}' '=' ';' '+' '-' '&' '|' '^' '!' '<' '>' '*' '/' '%' ','
  61
  62 %token number_hex number_dec number_oct number_bin
  63
  64 %type <idx> K_NAME var
  65 %type <number> number_hex number_dec number_oct number_bin number
  66
  67 %%
  68
  69 program
  70         : declaration_list { printf("_entry:\n"); } statement_list
  71         | short_ret /* for short filter statements */
  72         ;
  73
  74 declaration_list
  75         : declaration { num_vars++; } declaration_list
  76         | /* empty */
  77         ;
  78
  79 statement_list
  80         : statement statement_list
  81         | statement
  82         ;
  83
  84 declaration
  85         : K_DEF K_NAME ';' {
  86                 if (bpf_symtab_declared($2)) {
  87                         panic("Variable \"%s\" already declared (l%d)\n",
  88                               bpf_symtab_name($2), zzlineno);
  89                 } else {
  90                         printf("; @var %s\n", bpf_symtab_name($2));
  91                         bpf_symtab_declare($2);
  92                 }}
  93         ;
  94
  95 block
  96         : condition
  97         ;
  98
  99 statement
 100         : assignment ';'
 101         | return ';'
 102         | block
 103         ;
 104
 105 short_ret
 106         : expression
 107         ;
 108
 109 return
 110         : K_RET { printf("  ret a\n"); }
 111         | K_RET number { printf("  ret #%ld\n", $2); }
 112         | K_RET var { printf("  ret a\n"); }
 113         | K_RET expression { printf("  ret macro\n"); }
 114         ;
 115
 116 macro
 117         : K_MACRO_IPV4 { printf("ipv4\n"); }
 118         | K_MACRO_IPV6 { printf("ipv6\n"); }
 119         | K_MACRO_IP { printf("ip\n"); }
 120         | K_MACRO_UDP { printf("udp\n"); }
 121         | K_MACRO_TCP { printf("tcp\n"); }
 122         ;
 123
 124 condition
 125         : { num_ifs++; } K_IF '(' expression ')' '{'
 126                 { printf("jpt_f%ld:\n", num_ifs); }
 127           statement_list '}' condition_contd
 128         ;
 129
 130 condition_contd
 131         : K_ELIF '(' expression ')' '{' statement_list '}' condition_contd
 132         | K_ELSE '{' { printf("jpt_e%ld:\n", num_ifs); } statement_list '}'
 133         | /* None */
 134         ;
 135
 136 assignment
 137         : var '=' expression { printf("; @asn %s\n", bpf_symtab_name($1)); }
 138         | var '=' K_PKT '(' number ',' number ')' {
 139                         switch ($7) {
 140                         case 1:
 141                                 printf("  ldb [%ld]\n", $5);
 142                                 break;
 143                         case 2:
 144                                 printf("  ldh [%ld]\n", $5);
 145                                 break;
 146                         case 4:
 147                                 printf("  ld [%ld]\n", $5);
 148                                 break;
 149                         default:
 150                                 panic("Invalid argument (l%d)\n", zzlineno);
 151                         }
 152                 }
 153         ;
 154
 155 expression
 156         : term
 157         | '!' term { printf("; @!\n"); }
 158         | term '+' term { printf("; @+\n"); }
 159         | term '-' term { printf("; @-\n"); }
 160         | term '/' term { printf("; @/\n"); }
 161         | term '*' term { printf("; @*\n"); }
 162         | term '%' term { printf("; @\n"); }
 163         | term '&' term { printf("; @&\n"); }
 164         | term '|' term { printf("; @|\n"); }
 165         | term '^' term { printf("; @^\n"); }
 166         | term '<' term { printf("; @<\n"); }
 167         | term '>' term { printf("; @>\n"); }
 168         | term '=' '=' term { printf("; @==\n"); }
 169         | term '&' '&' term { printf("; @&&\n"); }
 170         | term '|' '|' term { printf("; @||\n"); }
 171         | term '<' '<' term { printf("; @<<\n"); }
 172         | term '>' '>' term { printf("; @>>\n"); }
 173         ;
 174
 175 term
 176         : number { printf("; @num %ld\n", $1); }
 177         | var { printf("; @var %s\n", bpf_symtab_name($1)); }
 178         | macro
 179         | '(' expression ')'
 180         ;
 181
 182 var
 183         : K_NAME {
 184                 if (!bpf_symtab_declared($1))
 185                         panic("Variable \"%s\" not declared (l%d)\n",
 186                               bpf_symtab_name($1), zzlineno);
 187                 $$ = $1; }
 188         ;
 189
 190 number
 191         : number_dec { $$ = $1; }
 192         | number_hex { $$ = $1; }
 193         | number_oct { $$ = $1; }
 194         | number_bin { $$ = $1; }
 195         ;
 196
 197 %%
 198
 199 static void stage_1_compile(void)
 200 {
 201         zzparse();
 202 }
 203
 204 int compile_hla_filter(char *file, int verbose, int debug)
 205 {
 206         int fd;
 207         fpos_t pos;
 208         char file_tmp[128];
 209
 210         if (!strncmp("-", file, strlen("-")))
 211                 zzin = stdin;
 212         else
 213                 zzin = fopen(file, "r");
 214         if (!zzin)
 215                 panic("Cannot open file!\n");
 216         if (!debug) {
 217                 fd = dup(fileno(stdout));
 218
 219                 slprintf(file_tmp, sizeof(file_tmp), ".%s", file);
 220                 if (freopen(file_tmp, "w", stdout) == NULL)
 221                         panic("Cannot reopen file!\n");
 222         }
 223
 224         stage_1_compile();
 225
 226         if (!debug) {
 227                 fflush(stdout);
 228                 dup2(fd, fileno(stdout));
 229
 230                 close(fd);
 231                 clearerr(stdout);
 232                 fsetpos(stdout, &pos);
 233         }
 234
 235         fclose(zzin);
 236
 237         bpf_symtab_cleanup();
 238         if (debug)
 239                 die();
 240
 241         return 0;
 242 }
 243
 244 void zzerror(const char *err)
 245 {
 246         panic("Syntax error at line %d: %s! %s!\n",
 247               zzlineno, zztext, err);
 248 }