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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