1 Java(tm) Binary Kernel Support for Linux v1.03
2 ----------------------------------------------
4 Linux beats them ALL! While all other OS's are TALKING about direct
5 support of Java Binaries in the OS, Linux is doing it!
7 You can execute Java applications and Java Applets just like any
8 other program after you have done the following:
10 1) 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:
14 ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO
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).
21 2) 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.
29 3) 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:'
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)
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!
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.
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.
57 Both the javawrapper shellscript and the javaclassname program
58 were supplied by Colin J. Watson <cjw44@cam.ac.uk>.
60 ====================== Cut here ===================
62 # /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java
66 echo Usage: $0 class-file
71 FQCLASS=`/usr/local/bin/javaclassname $1`
72 FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'`
73 FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'`
77 # FQCLASS=foo.bar.Test
83 declare -i LINKLEVEL=0
86 if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then
87 # See if this directory works straight off
88 cd -L `dirname $CLASS`
91 if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
92 CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
95 # Try dereferencing the directory name
96 cd -P `dirname $CLASS`
99 if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
100 CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
103 # If no other possible filename exists
104 if [ ! -L $CLASS ]; then
107 echo " $CLASS should be in a" \
108 "directory tree called $FQCLASSP"
112 if [ ! -L $CLASS ]; then break; fi
113 # Go down one more level of symbolic links
115 if [ $LINKLEVEL -gt 5 ]; then
118 echo " Too many symbolic links encountered"
121 CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'`
124 if [ -z "$CLASSBASE" ]; then
125 if [ -z "$FQCLASSP" ]; then
126 GOODNAME=$FQCLASSN.class
128 GOODNAME=$FQCLASSP/$FQCLASSN.class
132 echo " $FQCLASS should be in a file called $GOODNAME"
136 if ! 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
141 export CLASSPATH=$CLASSBASE:$CLASSPATH
146 /usr/bin/java $FQCLASS "$@"
147 ====================== Cut here ===================
150 ====================== Cut here ===================
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.
156 * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>.
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.
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.
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
176 #include <sys/types.h>
178 /* From Sun's Java VM Specification, as tag entries in the constant pool. */
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
195 /* Define some commonly used error messages */
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);
206 u_int8_t read_8(FILE *classfile);
207 u_int16_t read_16(FILE *classfile);
208 void skip_constant(FILE *classfile, u_int16_t *cur);
209 void error(const char *format, ...);
210 int main(int argc, char **argv);
212 /* Reads in an unsigned 8-bit integer. */
213 u_int8_t read_8(FILE *classfile)
215 int b = fgetc(classfile);
221 /* Reads in an unsigned 16-bit integer. */
222 u_int16_t read_16(FILE *classfile)
225 b1 = fgetc(classfile);
228 b2 = fgetc(classfile);
231 return (u_int16_t)((b1 << 8) | b2);
234 /* Reads in a value from the constant pool. */
235 void skip_constant(FILE *classfile, u_int16_t *cur)
239 pool[*cur] = ftell(classfile);
240 switch(read_8(classfile))
243 len = read_16(classfile);
244 seekerr = fseek(classfile, len, SEEK_CUR);
249 seekerr = fseek(classfile, 2, SEEK_CUR);
251 case CP_METHODHANDLE:
252 seekerr = fseek(classfile, 3, SEEK_CUR);
258 case CP_INTERFACEMETHODREF:
260 case CP_INVOKEDYNAMIC:
261 seekerr = fseek(classfile, 4, SEEK_CUR);
265 seekerr = fseek(classfile, 8, SEEK_CUR);
275 void error(const char *format, ...)
278 va_start(ap, format);
279 vfprintf(stderr, format, ap);
284 int main(int argc, char **argv)
287 u_int16_t cp_count, i, this_class, classinfo_ptr;
293 error("%s: Missing input file\n", program);
294 classfile = fopen(argv[1], "rb");
296 error("%s: Error opening %s\n", program, argv[1]);
298 if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */
300 cp_count = read_16(classfile);
301 pool = calloc(cp_count, sizeof(long));
303 error("%s: Out of memory for constant pool\n", program);
305 for(i = 1; i < cp_count; ++i)
306 skip_constant(classfile, &i);
307 if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */
310 this_class = read_16(classfile);
311 if(this_class < 1 || this_class >= cp_count)
313 if(!pool[this_class] || pool[this_class] == -1)
315 if(fseek(classfile, pool[this_class] + 1, SEEK_SET))
318 classinfo_ptr = read_16(classfile);
319 if(classinfo_ptr < 1 || classinfo_ptr >= cp_count)
321 if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1)
323 if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET))
326 length = read_16(classfile);
327 for(i = 0; i < length; ++i)
329 u_int8_t x = read_8(classfile);
332 if((x & 0xE0) == 0xC0)
334 u_int8_t y = read_8(classfile);
335 if((y & 0xC0) == 0x80)
337 int c = ((x & 0x1f) << 6) + (y & 0x3f);
345 else if(x == '/') putchar('.');
353 ====================== Cut here ===================
356 ====================== Cut here ===================
358 # /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar
361 ====================== Cut here ===================
364 Now simply chmod +x the .class, .jar and/or .html files you want to execute.
365 To 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
367 extension. The directory containing the original .class file will be
368 added to your CLASSPATH during execution.
371 To test your new setup, enter in the following simple Java app, and name
372 it "HelloWorld.java":
375 public static void main(String args[]) {
376 System.out.println("Hello World!");
380 Now compile the application with:
381 javac HelloWorld.java
383 Set the executable permissions of the binary file, with:
384 chmod 755 HelloWorld.class
390 To execute Java Jar files, simple chmod the *.jar files to include
391 the execution bit, then just do
395 To execute Java Applets, simple chmod the *.html files to include
396 the execution bit, then just do
400 originally by Brian A. Lantz, brian@lantz.com
401 heavily edited for binfmt_misc by Richard Günther
402 new scripts by Colin J. Watson <cjw44@cam.ac.uk>
403 added executable Jar file support by Kurt Huwig <kurt@iku-netz.de>