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