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+Java(tm) Binary Kernel Support for Linux v1.03
+----------------------------------------------
+
+Linux beats them ALL! While all other OS's are TALKING about direct
+support of Java Binaries in the OS, Linux is doing it!
+
+You can execute Java applications and Java Applets just like any
+other program after you have done the following:
+
+1) You MUST FIRST install the Java Developers Kit for Linux.
+ The Java on Linux HOWTO gives the details on getting and
+ installing this. This HOWTO can be found at:
+
+ ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/Java-HOWTO
+
+ You should also set up a reasonable CLASSPATH environment
+ variable to use Java applications that make use of any
+ nonstandard classes (not included in the same directory
+ as the application itself).
+
+2) You have to compile BINFMT_MISC either as a module or into
+ the kernel (``CONFIG_BINFMT_MISC``) and set it up properly.
+ If you choose to compile it as a module, you will have
+ to insert it manually with modprobe/insmod, as kmod
+ cannot easily be supported with binfmt_misc.
+ Read the file 'binfmt_misc.txt' in this directory to know
+ more about the configuration process.
+
+3) Add the following configuration items to binfmt_misc
+ (you should really have read ``binfmt_misc.txt`` now):
+ support for Java applications::
+
+ ':Java:M::\xca\xfe\xba\xbe::/usr/local/bin/javawrapper:'
+
+ support for executable Jar files::
+
+ ':ExecutableJAR:E::jar::/usr/local/bin/jarwrapper:'
+
+ support for Java Applets::
+
+ ':Applet:E::html::/usr/bin/appletviewer:'
+
+ or the following, if you want to be more selective::
+
+ ':Applet:M::<!--applet::/usr/bin/appletviewer:'
+
+ Of course you have to fix the path names. The path/file names given in this
+ document match the Debian 2.1 system. (i.e. jdk installed in ``/usr``,
+ custom wrappers from this document in ``/usr/local``)
+
+ Note, that for the more selective applet support you have to modify
+ existing html-files to contain ``<!--applet-->`` in the first line
+ (``<`` has to be the first character!) to let this work!
+
+ For the compiled Java programs you need a wrapper script like the
+ following (this is because Java is broken in case of the filename
+ handling), again fix the path names, both in the script and in the
+ above given configuration string.
+
+ You, too, need the little program after the script. Compile like::
+
+ gcc -O2 -o javaclassname javaclassname.c
+
+ and stick it to ``/usr/local/bin``.
+
+ Both the javawrapper shellscript and the javaclassname program
+ were supplied by Colin J. Watson <cjw44@cam.ac.uk>.
+
+Javawrapper shell script:
+
+.. code-block:: sh
+
+ #!/bin/bash
+ # /usr/local/bin/javawrapper - the wrapper for binfmt_misc/java
+
+ if [ -z "$1" ]; then
+ exec 1>&2
+ echo Usage: $0 class-file
+ exit 1
+ fi
+
+ CLASS=$1
+ FQCLASS=`/usr/local/bin/javaclassname $1`
+ FQCLASSN=`echo $FQCLASS | sed -e 's/^.*\.\([^.]*\)$/\1/'`
+ FQCLASSP=`echo $FQCLASS | sed -e 's-\.-/-g' -e 's-^[^/]*$--' -e 's-/[^/]*$--'`
+
+ # for example:
+ # CLASS=Test.class
+ # FQCLASS=foo.bar.Test
+ # FQCLASSN=Test
+ # FQCLASSP=foo/bar
+
+ unset CLASSBASE
+
+ declare -i LINKLEVEL=0
+
+ while :; do
+ if [ "`basename $CLASS .class`" == "$FQCLASSN" ]; then
+ # See if this directory works straight off
+ cd -L `dirname $CLASS`
+ CLASSDIR=$PWD
+ cd $OLDPWD
+ if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
+ CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
+ break;
+ fi
+ # Try dereferencing the directory name
+ cd -P `dirname $CLASS`
+ CLASSDIR=$PWD
+ cd $OLDPWD
+ if echo $CLASSDIR | grep -q "$FQCLASSP$"; then
+ CLASSBASE=`echo $CLASSDIR | sed -e "s.$FQCLASSP$.."`
+ break;
+ fi
+ # If no other possible filename exists
+ if [ ! -L $CLASS ]; then
+ exec 1>&2
+ echo $0:
+ echo " $CLASS should be in a" \
+ "directory tree called $FQCLASSP"
+ exit 1
+ fi
+ fi
+ if [ ! -L $CLASS ]; then break; fi
+ # Go down one more level of symbolic links
+ let LINKLEVEL+=1
+ if [ $LINKLEVEL -gt 5 ]; then
+ exec 1>&2
+ echo $0:
+ echo " Too many symbolic links encountered"
+ exit 1
+ fi
+ CLASS=`ls --color=no -l $CLASS | sed -e 's/^.* \([^ ]*\)$/\1/'`
+ done
+
+ if [ -z "$CLASSBASE" ]; then
+ if [ -z "$FQCLASSP" ]; then
+ GOODNAME=$FQCLASSN.class
+ else
+ GOODNAME=$FQCLASSP/$FQCLASSN.class
+ fi
+ exec 1>&2
+ echo $0:
+ echo " $FQCLASS should be in a file called $GOODNAME"
+ exit 1
+ fi
+
+ if ! echo $CLASSPATH | grep -q "^\(.*:\)*$CLASSBASE\(:.*\)*"; then
+ # class is not in CLASSPATH, so prepend dir of class to CLASSPATH
+ if [ -z "${CLASSPATH}" ] ; then
+ export CLASSPATH=$CLASSBASE
+ else
+ export CLASSPATH=$CLASSBASE:$CLASSPATH
+ fi
+ fi
+
+ shift
+ /usr/bin/java $FQCLASS "$@"
+
+javaclassname.c:
+
+.. code-block:: c
+
+ /* javaclassname.c
+ *
+ * Extracts the class name from a Java class file; intended for use in a Java
+ * wrapper of the type supported by the binfmt_misc option in the Linux kernel.
+ *
+ * Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+ #include <stdlib.h>
+ #include <stdio.h>
+ #include <stdarg.h>
+ #include <sys/types.h>
+
+ /* From Sun's Java VM Specification, as tag entries in the constant pool. */
+
+ #define CP_UTF8 1
+ #define CP_INTEGER 3
+ #define CP_FLOAT 4
+ #define CP_LONG 5
+ #define CP_DOUBLE 6
+ #define CP_CLASS 7
+ #define CP_STRING 8
+ #define CP_FIELDREF 9
+ #define CP_METHODREF 10
+ #define CP_INTERFACEMETHODREF 11
+ #define CP_NAMEANDTYPE 12
+ #define CP_METHODHANDLE 15
+ #define CP_METHODTYPE 16
+ #define CP_INVOKEDYNAMIC 18
+
+ /* Define some commonly used error messages */
+
+ #define seek_error() error("%s: Cannot seek\n", program)
+ #define corrupt_error() error("%s: Class file corrupt\n", program)
+ #define eof_error() error("%s: Unexpected end of file\n", program)
+ #define utf8_error() error("%s: Only ASCII 1-255 supported\n", program);
+
+ char *program;
+
+ long *pool;
+
+ u_int8_t read_8(FILE *classfile);
+ u_int16_t read_16(FILE *classfile);
+ void skip_constant(FILE *classfile, u_int16_t *cur);
+ void error(const char *format, ...);
+ int main(int argc, char **argv);
+
+ /* Reads in an unsigned 8-bit integer. */
+ u_int8_t read_8(FILE *classfile)
+ {
+ int b = fgetc(classfile);
+ if(b == EOF)
+ eof_error();
+ return (u_int8_t)b;
+ }
+
+ /* Reads in an unsigned 16-bit integer. */
+ u_int16_t read_16(FILE *classfile)
+ {
+ int b1, b2;
+ b1 = fgetc(classfile);
+ if(b1 == EOF)
+ eof_error();
+ b2 = fgetc(classfile);
+ if(b2 == EOF)
+ eof_error();
+ return (u_int16_t)((b1 << 8) | b2);
+ }
+
+ /* Reads in a value from the constant pool. */
+ void skip_constant(FILE *classfile, u_int16_t *cur)
+ {
+ u_int16_t len;
+ int seekerr = 1;
+ pool[*cur] = ftell(classfile);
+ switch(read_8(classfile))
+ {
+ case CP_UTF8:
+ len = read_16(classfile);
+ seekerr = fseek(classfile, len, SEEK_CUR);
+ break;
+ case CP_CLASS:
+ case CP_STRING:
+ case CP_METHODTYPE:
+ seekerr = fseek(classfile, 2, SEEK_CUR);
+ break;
+ case CP_METHODHANDLE:
+ seekerr = fseek(classfile, 3, SEEK_CUR);
+ break;
+ case CP_INTEGER:
+ case CP_FLOAT:
+ case CP_FIELDREF:
+ case CP_METHODREF:
+ case CP_INTERFACEMETHODREF:
+ case CP_NAMEANDTYPE:
+ case CP_INVOKEDYNAMIC:
+ seekerr = fseek(classfile, 4, SEEK_CUR);
+ break;
+ case CP_LONG:
+ case CP_DOUBLE:
+ seekerr = fseek(classfile, 8, SEEK_CUR);
+ ++(*cur);
+ break;
+ default:
+ corrupt_error();
+ }
+ if(seekerr)
+ seek_error();
+ }
+
+ void error(const char *format, ...)
+ {
+ va_list ap;
+ va_start(ap, format);
+ vfprintf(stderr, format, ap);
+ va_end(ap);
+ exit(1);
+ }
+
+ int main(int argc, char **argv)
+ {
+ FILE *classfile;
+ u_int16_t cp_count, i, this_class, classinfo_ptr;
+ u_int8_t length;
+
+ program = argv[0];
+
+ if(!argv[1])
+ error("%s: Missing input file\n", program);
+ classfile = fopen(argv[1], "rb");
+ if(!classfile)
+ error("%s: Error opening %s\n", program, argv[1]);
+
+ if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */
+ seek_error();
+ cp_count = read_16(classfile);
+ pool = calloc(cp_count, sizeof(long));
+ if(!pool)
+ error("%s: Out of memory for constant pool\n", program);
+
+ for(i = 1; i < cp_count; ++i)
+ skip_constant(classfile, &i);
+ if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */
+ seek_error();
+
+ this_class = read_16(classfile);
+ if(this_class < 1 || this_class >= cp_count)
+ corrupt_error();
+ if(!pool[this_class] || pool[this_class] == -1)
+ corrupt_error();
+ if(fseek(classfile, pool[this_class] + 1, SEEK_SET))
+ seek_error();
+
+ classinfo_ptr = read_16(classfile);
+ if(classinfo_ptr < 1 || classinfo_ptr >= cp_count)
+ corrupt_error();
+ if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1)
+ corrupt_error();
+ if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET))
+ seek_error();
+
+ length = read_16(classfile);
+ for(i = 0; i < length; ++i)
+ {
+ u_int8_t x = read_8(classfile);
+ if((x & 0x80) || !x)
+ {
+ if((x & 0xE0) == 0xC0)
+ {
+ u_int8_t y = read_8(classfile);
+ if((y & 0xC0) == 0x80)
+ {
+ int c = ((x & 0x1f) << 6) + (y & 0x3f);
+ if(c) putchar(c);
+ else utf8_error();
+ }
+ else utf8_error();
+ }
+ else utf8_error();
+ }
+ else if(x == '/') putchar('.');
+ else putchar(x);
+ }
+ putchar('\n');
+ free(pool);
+ fclose(classfile);
+ return 0;
+ }
+
+jarwrapper::
+
+ #!/bin/bash
+ # /usr/local/java/bin/jarwrapper - the wrapper for binfmt_misc/jar
+
+ java -jar $1
+
+
+Now simply ``chmod +x`` the ``.class``, ``.jar`` and/or ``.html`` files you
+want to execute.
+
+To add a Java program to your path best put a symbolic link to the main
+.class file into /usr/bin (or another place you like) omitting the .class
+extension. The directory containing the original .class file will be
+added to your CLASSPATH during execution.
+
+
+To test your new setup, enter in the following simple Java app, and name
+it "HelloWorld.java":
+
+.. code-block:: java
+
+ class HelloWorld {
+ public static void main(String args[]) {
+ System.out.println("Hello World!");
+ }
+ }
+
+Now compile the application with::
+
+ javac HelloWorld.java
+
+Set the executable permissions of the binary file, with::
+
+ chmod 755 HelloWorld.class
+
+And then execute it::
+
+ ./HelloWorld.class
+
+
+To execute Java Jar files, simple chmod the ``*.jar`` files to include
+the execution bit, then just do::
+
+ ./Application.jar
+
+
+To execute Java Applets, simple chmod the ``*.html`` files to include
+the execution bit, then just do::
+
+ ./Applet.html
+
+
+originally by Brian A. Lantz, brian@lantz.com
+heavily edited for binfmt_misc by Richard Günther
+new scripts by Colin J. Watson <cjw44@cam.ac.uk>
+added executable Jar file support by Kurt Huwig <kurt@iku-netz.de>