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 12 191 192/* Define some commonly used error messages */ 193 194#define seek_error() error("%s: Cannot seek\n", program) 195#define corrupt_error() error("%s: Class file corrupt\n", program) 196#define eof_error() error("%s: Unexpected end of file\n", program) 197#define utf8_error() error("%s: Only ASCII 1-255 supported\n", program); 198 199char *program; 200 201long *pool; 202 203u_int8_t read_8(FILE *classfile); 204u_int16_t read_16(FILE *classfile); 205void skip_constant(FILE *classfile, u_int16_t *cur); 206void error(const char *format, ...); 207int main(int argc, char **argv); 208 209/* Reads in an unsigned 8-bit integer. */ 210u_int8_t read_8(FILE *classfile) 211{ 212 int b = fgetc(classfile); 213 if(b == EOF) 214 eof_error(); 215 return (u_int8_t)b; 216} 217 218/* Reads in an unsigned 16-bit integer. */ 219u_int16_t read_16(FILE *classfile) 220{ 221 int b1, b2; 222 b1 = fgetc(classfile); 223 if(b1 == EOF) 224 eof_error(); 225 b2 = fgetc(classfile); 226 if(b2 == EOF) 227 eof_error(); 228 return (u_int16_t)((b1 << 8) | b2); 229} 230 231/* Reads in a value from the constant pool. */ 232void skip_constant(FILE *classfile, u_int16_t *cur) 233{ 234 u_int16_t len; 235 int seekerr = 1; 236 pool[*cur] = ftell(classfile); 237 switch(read_8(classfile)) 238 { 239 case CP_UTF8: 240 len = read_16(classfile); 241 seekerr = fseek(classfile, len, SEEK_CUR); 242 break; 243 case CP_CLASS: 244 case CP_STRING: 245 seekerr = fseek(classfile, 2, SEEK_CUR); 246 break; 247 case CP_INTEGER: 248 case CP_FLOAT: 249 case CP_FIELDREF: 250 case CP_METHODREF: 251 case CP_INTERFACEMETHODREF: 252 case CP_NAMEANDTYPE: 253 seekerr = fseek(classfile, 4, SEEK_CUR); 254 break; 255 case CP_LONG: 256 case CP_DOUBLE: 257 seekerr = fseek(classfile, 8, SEEK_CUR); 258 ++(*cur); 259 break; 260 default: 261 corrupt_error(); 262 } 263 if(seekerr) 264 seek_error(); 265} 266 267void error(const char *format, ...) 268{ 269 va_list ap; 270 va_start(ap, format); 271 vfprintf(stderr, format, ap); 272 va_end(ap); 273 exit(1); 274} 275 276int main(int argc, char **argv) 277{ 278 FILE *classfile; 279 u_int16_t cp_count, i, this_class, classinfo_ptr; 280 u_int8_t length; 281 282 program = argv[0]; 283 284 if(!argv[1]) 285 error("%s: Missing input file\n", program); 286 classfile = fopen(argv[1], "rb"); 287 if(!classfile) 288 error("%s: Error opening %s\n", program, argv[1]); 289 290 if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */ 291 seek_error(); 292 cp_count = read_16(classfile); 293 pool = calloc(cp_count, sizeof(long)); 294 if(!pool) 295 error("%s: Out of memory for constant pool\n", program); 296 297 for(i = 1; i < cp_count; ++i) 298 skip_constant(classfile, &i); 299 if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */ 300 seek_error(); 301 302 this_class = read_16(classfile); 303 if(this_class < 1 || this_class >= cp_count) 304 corrupt_error(); 305 if(!pool[this_class] || pool[this_class] == -1) 306 corrupt_error(); 307 if(fseek(classfile, pool[this_class] + 1, SEEK_SET)) 308 seek_error(); 309 310 classinfo_ptr = read_16(classfile); 311 if(classinfo_ptr < 1 || classinfo_ptr >= cp_count) 312 corrupt_error(); 313 if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1) 314 corrupt_error(); 315 if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET)) 316 seek_error(); 317 318 length = read_16(classfile); 319 for(i = 0; i < length; ++i) 320 { 321 u_int8_t x = read_8(classfile); 322 if((x & 0x80) || !x) 323 { 324 if((x & 0xE0) == 0xC0) 325 { 326 u_int8_t y = read_8(classfile); 327 if((y & 0xC0) == 0x80) 328 { 329 int c = ((x & 0x1f) << 6) + (y & 0x3f); 330 if(c) putchar(c); 331 else utf8_error(); 332 } 333 else utf8_error(); 334 } 335 else utf8_error(); 336 } 337 else if(x == '/') putchar('.'); 338 else putchar(x); 339 } 340 putchar('\n'); 341 free(pool); 342 fclose(classfile); 343 return 0; 344} 345====================== Cut here =================== 346 347 348====================== Cut here =================== 349#!/bin/bash 350# /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar 351 352java -jar $1 353====================== Cut here =================== 354 355 356Now simply chmod +x the .class, .jar and/or .html files you want to execute. 357To add a Java program to your path best put a symbolic link to the main 358.class file into /usr/bin (or another place you like) omitting the .class 359extension. The directory containing the original .class file will be 360added to your CLASSPATH during execution. 361 362 363To test your new setup, enter in the following simple Java app, and name 364it "HelloWorld.java": 365 366 class HelloWorld { 367 public static void main(String args[]) { 368 System.out.println("Hello World!"); 369 } 370 } 371 372Now compile the application with: 373 javac HelloWorld.java 374 375Set the executable permissions of the binary file, with: 376 chmod 755 HelloWorld.class 377 378And then execute it: 379 ./HelloWorld.class 380 381 382To execute Java Jar files, simple chmod the *.jar files to include 383the execution bit, then just do 384 ./Application.jar 385 386 387To execute Java Applets, simple chmod the *.html files to include 388the execution bit, then just do 389 ./Applet.html 390 391 392originally by Brian A. Lantz, brian@lantz.com 393heavily edited for binfmt_misc by Richard Günther 394new scripts by Colin J. Watson <cjw44@cam.ac.uk> 395added executable Jar file support by Kurt Huwig <kurt@iku-netz.de> 396 397