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diff --git a/Documentation/admin-guide/java.rst b/Documentation/admin-guide/java.rst new file mode 100644 index 000000000..8744e272e --- /dev/null +++ b/Documentation/admin-guide/java.rst @@ -0,0 +1,423 @@ +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> |