1Java(tm) Binary Kernel Support for Linux v1.03 2---------------------------------------------- 3 4Linux beats them ALL! While all other OS's are TALKING about direct 5support of Java Binaries in the OS, Linux is doing it! 6 7You can execute Java applications and Java Applets just like any 8other program after you have done the following: 9 101) You MUST FIRST install the Java Developers Kit for Linux. 11 The Java on Linux HOWTO gives the details on getting and 12 installing this. This HOWTO can be found at: 13 14 ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO 15 16 You should also set up a reasonable CLASSPATH environment 17 variable to use Java applications that make use of any 18 nonstandard classes (not included in the same directory 19 as the application itself). 20 212) You have to compile BINFMT_MISC either as a module or into 22 the kernel (``CONFIG_BINFMT_MISC``) and set it up properly. 23 If you choose to compile it as a module, you will have 24 to insert it manually with modprobe/insmod, as kmod 25 cannot easily be supported with binfmt_misc. 26 Read the file 'binfmt_misc.txt' in this directory to know 27 more about the configuration process. 28 293) Add the following configuration items to binfmt_misc 30 (you should really have read ``binfmt_misc.txt`` now): 31 support for Java applications:: 32 33 ':Java:M::\xca\xfe\xba\xbe::/usr/local/bin/javawrapper:' 34 35 support for executable Jar files:: 36 37 ':ExecutableJAR:E::jar::/usr/local/bin/jarwrapper:' 38 39 support for Java Applets:: 40 41 ':Applet:E::html::/usr/bin/appletviewer:' 42 43 or the following, if you want to be more selective:: 44 45 ':Applet:M::<!--applet::/usr/bin/appletviewer:' 46 47 Of course you have to fix the path names. The path/file names given in this 48 document match the Debian 2.1 system. (i.e. jdk installed in ``/usr``, 49 custom wrappers from this document in ``/usr/local``) 50 51 Note, that for the more selective applet support you have to modify 52 existing html-files to contain ``<!--applet-->`` in the first line 53 (``<`` has to be the first character!) to let this work! 54 55 For the compiled Java programs you need a wrapper script like the 56 following (this is because Java is broken in case of the filename 57 handling), again fix the path names, both in the script and in the 58 above given configuration string. 59 60 You, too, need the little program after the script. Compile like:: 61 62 gcc -O2 -o javaclassname javaclassname.c 63 64 and stick it to ``/usr/local/bin``. 65 66 Both the javawrapper shellscript and the javaclassname program 67 were supplied by Colin J. Watson <cjw44@cam.ac.uk>. 68 69Javawrapper shell script: 70 71.. code-block:: sh 72 73 #!/bin/bash 74 # /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java 75 76 if [ -z "$1" ]; then 77 exec 1>&2 78 echo Usage: $0 class-file 79 exit 1 80 fi 81 82 CLASS=$1 83 FQCLASS=`/usr/local/bin/javaclassname $1` 84 FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'` 85 FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'` 86 87 # for example: 88 # CLASS=Test.class 89 # FQCLASS=foo.bar.Test 90 # FQCLASSN=Test 91 # FQCLASSP=foo/bar 92 93 unset CLASSBASE 94 95 declare -i LINKLEVEL=0 96 97 while :; do 98 if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then 99 # See if this directory works straight off 100 cd -L `dirname $CLASS` 101 CLASSDIR=$PWD 102 cd $OLDPWD 103 if echo $CLASSDIR | grep -q "$FQCLASSP$"; then 104 CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."` 105 break; 106 fi 107 # Try dereferencing the directory name 108 cd -P `dirname $CLASS` 109 CLASSDIR=$PWD 110 cd $OLDPWD 111 if echo $CLASSDIR | grep -q "$FQCLASSP$"; then 112 CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."` 113 break; 114 fi 115 # If no other possible filename exists 116 if [ ! -L $CLASS ]; then 117 exec 1>&2 118 echo $0: 119 echo " $CLASS should be in a" \ 120 "directory tree called $FQCLASSP" 121 exit 1 122 fi 123 fi 124 if [ ! -L $CLASS ]; then break; fi 125 # Go down one more level of symbolic links 126 let LINKLEVEL+=1 127 if [ $LINKLEVEL -gt 5 ]; then 128 exec 1>&2 129 echo $0: 130 echo " Too many symbolic links encountered" 131 exit 1 132 fi 133 CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'` 134 done 135 136 if [ -z "$CLASSBASE" ]; then 137 if [ -z "$FQCLASSP" ]; then 138 GOODNAME=$FQCLASSN.class 139 else 140 GOODNAME=$FQCLASSP/$FQCLASSN.class 141 fi 142 exec 1>&2 143 echo $0: 144 echo " $FQCLASS should be in a file called $GOODNAME" 145 exit 1 146 fi 147 148 if ! echo $CLASSPATH | grep -q "^\(.*:\)*$CLASSBASE\(:.*\)*"; then 149 # class is not in CLASSPATH, so prepend dir of class to CLASSPATH 150 if [ -z "${CLASSPATH}" ] ; then 151 export CLASSPATH=$CLASSBASE 152 else 153 export CLASSPATH=$CLASSBASE:$CLASSPATH 154 fi 155 fi 156 157 shift 158 /usr/bin/java $FQCLASS "$@" 159 160javaclassname.c: 161 162.. code-block:: c 163 164 /* javaclassname.c 165 * 166 * Extracts the class name from a Java class file; intended for use in a Java 167 * wrapper of the type supported by the binfmt_misc option in the Linux kernel. 168 * 169 * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>. 170 * 171 * This program is free software; you can redistribute it and/or modify 172 * it under the terms of the GNU General Public License as published by 173 * the Free Software Foundation; either version 2 of the License, or 174 * (at your option) any later version. 175 * 176 * This program is distributed in the hope that it will be useful, 177 * but WITHOUT ANY WARRANTY; without even the implied warranty of 178 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 179 * GNU General Public License for more details. 180 * 181 * You should have received a copy of the GNU General Public License 182 * along with this program; if not, write to the Free Software 183 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 184 */ 185 186 #include <stdlib.h> 187 #include <stdio.h> 188 #include <stdarg.h> 189 #include <sys/types.h> 190 191 /* From Sun's Java VM Specification, as tag entries in the constant pool. */ 192 193 #define CP_UTF8 1 194 #define CP_INTEGER 3 195 #define CP_FLOAT 4 196 #define CP_LONG 5 197 #define CP_DOUBLE 6 198 #define CP_CLASS 7 199 #define CP_STRING 8 200 #define CP_FIELDREF 9 201 #define CP_METHODREF 10 202 #define CP_INTERFACEMETHODREF 11 203 #define CP_NAMEANDTYPE 12 204 #define CP_METHODHANDLE 15 205 #define CP_METHODTYPE 16 206 #define CP_INVOKEDYNAMIC 18 207 208 /* Define some commonly used error messages */ 209 210 #define seek_error() error("%s: Cannot seek\n", program) 211 #define corrupt_error() error("%s: Class file corrupt\n", program) 212 #define eof_error() error("%s: Unexpected end of file\n", program) 213 #define utf8_error() error("%s: Only ASCII 1-255 supported\n", program); 214 215 char *program; 216 217 long *pool; 218 219 u_int8_t read_8(FILE *classfile); 220 u_int16_t read_16(FILE *classfile); 221 void skip_constant(FILE *classfile, u_int16_t *cur); 222 void error(const char *format, ...); 223 int main(int argc, char **argv); 224 225 /* Reads in an unsigned 8-bit integer. */ 226 u_int8_t read_8(FILE *classfile) 227 { 228 int b = fgetc(classfile); 229 if(b == EOF) 230 eof_error(); 231 return (u_int8_t)b; 232 } 233 234 /* Reads in an unsigned 16-bit integer. */ 235 u_int16_t read_16(FILE *classfile) 236 { 237 int b1, b2; 238 b1 = fgetc(classfile); 239 if(b1 == EOF) 240 eof_error(); 241 b2 = fgetc(classfile); 242 if(b2 == EOF) 243 eof_error(); 244 return (u_int16_t)((b1 << 8) | b2); 245 } 246 247 /* Reads in a value from the constant pool. */ 248 void skip_constant(FILE *classfile, u_int16_t *cur) 249 { 250 u_int16_t len; 251 int seekerr = 1; 252 pool[*cur] = ftell(classfile); 253 switch(read_8(classfile)) 254 { 255 case CP_UTF8: 256 len = read_16(classfile); 257 seekerr = fseek(classfile, len, SEEK_CUR); 258 break; 259 case CP_CLASS: 260 case CP_STRING: 261 case CP_METHODTYPE: 262 seekerr = fseek(classfile, 2, SEEK_CUR); 263 break; 264 case CP_METHODHANDLE: 265 seekerr = fseek(classfile, 3, SEEK_CUR); 266 break; 267 case CP_INTEGER: 268 case CP_FLOAT: 269 case CP_FIELDREF: 270 case CP_METHODREF: 271 case CP_INTERFACEMETHODREF: 272 case CP_NAMEANDTYPE: 273 case CP_INVOKEDYNAMIC: 274 seekerr = fseek(classfile, 4, SEEK_CUR); 275 break; 276 case CP_LONG: 277 case CP_DOUBLE: 278 seekerr = fseek(classfile, 8, SEEK_CUR); 279 ++(*cur); 280 break; 281 default: 282 corrupt_error(); 283 } 284 if(seekerr) 285 seek_error(); 286 } 287 288 void error(const char *format, ...) 289 { 290 va_list ap; 291 va_start(ap, format); 292 vfprintf(stderr, format, ap); 293 va_end(ap); 294 exit(1); 295 } 296 297 int main(int argc, char **argv) 298 { 299 FILE *classfile; 300 u_int16_t cp_count, i, this_class, classinfo_ptr; 301 u_int8_t length; 302 303 program = argv[0]; 304 305 if(!argv[1]) 306 error("%s: Missing input file\n", program); 307 classfile = fopen(argv[1], "rb"); 308 if(!classfile) 309 error("%s: Error opening %s\n", program, argv[1]); 310 311 if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */ 312 seek_error(); 313 cp_count = read_16(classfile); 314 pool = calloc(cp_count, sizeof(long)); 315 if(!pool) 316 error("%s: Out of memory for constant pool\n", program); 317 318 for(i = 1; i < cp_count; ++i) 319 skip_constant(classfile, &i); 320 if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */ 321 seek_error(); 322 323 this_class = read_16(classfile); 324 if(this_class < 1 || this_class >= cp_count) 325 corrupt_error(); 326 if(!pool[this_class] || pool[this_class] == -1) 327 corrupt_error(); 328 if(fseek(classfile, pool[this_class] + 1, SEEK_SET)) 329 seek_error(); 330 331 classinfo_ptr = read_16(classfile); 332 if(classinfo_ptr < 1 || classinfo_ptr >= cp_count) 333 corrupt_error(); 334 if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1) 335 corrupt_error(); 336 if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET)) 337 seek_error(); 338 339 length = read_16(classfile); 340 for(i = 0; i < length; ++i) 341 { 342 u_int8_t x = read_8(classfile); 343 if((x & 0x80) || !x) 344 { 345 if((x & 0xE0) == 0xC0) 346 { 347 u_int8_t y = read_8(classfile); 348 if((y & 0xC0) == 0x80) 349 { 350 int c = ((x & 0x1f) << 6) + (y & 0x3f); 351 if(c) putchar(c); 352 else utf8_error(); 353 } 354 else utf8_error(); 355 } 356 else utf8_error(); 357 } 358 else if(x == '/') putchar('.'); 359 else putchar(x); 360 } 361 putchar('\n'); 362 free(pool); 363 fclose(classfile); 364 return 0; 365 } 366 367jarwrapper:: 368 369 #!/bin/bash 370 # /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar 371 372 java -jar $1 373 374 375Now simply ``chmod +x`` the ``.class``, ``.jar`` and/or ``.html`` files you 376want to execute. 377 378To add a Java program to your path best put a symbolic link to the main 379.class file into /usr/bin (or another place you like) omitting the .class 380extension. The directory containing the original .class file will be 381added to your CLASSPATH during execution. 382 383 384To test your new setup, enter in the following simple Java app, and name 385it "HelloWorld.java": 386 387.. code-block:: java 388 389 class HelloWorld { 390 public static void main(String args[]) { 391 System.out.println("Hello World!"); 392 } 393 } 394 395Now compile the application with:: 396 397 javac HelloWorld.java 398 399Set the executable permissions of the binary file, with:: 400 401 chmod 755 HelloWorld.class 402 403And then execute it:: 404 405 ./HelloWorld.class 406 407 408To execute Java Jar files, simple chmod the ``*.jar`` files to include 409the execution bit, then just do:: 410 411 ./Application.jar 412 413 414To execute Java Applets, simple chmod the ``*.html`` files to include 415the execution bit, then just do:: 416 417 ./Applet.html 418 419 420originally by Brian A. Lantz, brian@lantz.com 421heavily edited for binfmt_misc by Richard Günther 422new scripts by Colin J. Watson <cjw44@cam.ac.uk> 423added executable Jar file support by Kurt Huwig <kurt@iku-netz.de> 424