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diff --git a/Documentation/binfmt_misc.txt b/Documentation/binfmt_misc.txt new file mode 100644 index 000000000..81d49b2bc --- /dev/null +++ b/Documentation/binfmt_misc.txt @@ -0,0 +1,83 @@ + Kernel Support for miscellaneous (your favourite) Binary Formats v1.1 + ==================================================================== + +This Kernel feature allows to invoke almost (for restrictions see below) every +program by simply typing it's name in the shell. +This includes for example compiled Java(TM), Python or Emacs programs. + +To achieve this you must tell binfmt_misc which interpreter has to be invoked with +which binary. Binfmt_misc recognises the binary-type by matching some bytes at the +beginning of the file with a magic byte sequence (masking out specified bits) you +have supplied. Binfmt_misc can also recognise a filename extension (aka .com) and +optionally strip it off. + +To actually register a new binary type, you have to set up a string looking like +:name:type:offset:magic:mask:interpreter: (where you can choose the ':' upon your +needs) and echo it to /proc/sys/fs/binfmt_misc/register. +Here is what the fields mean: + - 'name' is an identifier string. A new /proc file will be created with this + this name below /proc/sys/fs/binfmt_misc + - 'type' is the type of recognition. Give 'M' for magic and 'E' for extension. + Give the corresponding lowercase letter to let binfmt_misc strip of the + filename extension. + - 'offset' is the offset of the magic/mask in the file counted in bytes. This + defaults to 0 if you omit it (i.e. you write ':name:type::magic...') + - 'magic' is the byte sequence binfmt_misc is matching for. The magic string + may contain hex-encoded characters like \x0a or \xA4. In a shell environment + you will have to write \\x0a to prevent the shell from eating your \. + If you chose filename extension matching, this is the extension to be + recognised (the \x0a specials are not allowed). Extension matching is case + sensitive! + - 'mask' is an (optional, defaults to all 0xff) mask. You can mask out some bits + from matching by supplying a string like magic and as long as magic. The + mask is anded with the byte sequence of the file. + - 'interpreter' is the program that should be invoked with the binary as first + argument (specify the full path) +There are some restrictions: + - the whole register string may not exceed 255 characters + - the magic must resist in the first 128 bytes of the file, i.e. offset+size(magic) + has to be less than 128 + - the interpreter string may not exceed 127 characters +You may want to add the binary formats in one of your /etc/rc scripts during boot-up. +Read the manual of your init program to figure out how to do this right. + + +A few examples (assumed you are in /proc/sys/fs/binfmt_misc): + +- enable Java(TM)-support (like binfmt_java): + echo ":Java:M::\xca\xfe\xba\xbe::/usr/local/bin/java:" > register + echo :Applet:M::\<\!--applet::/usr/local/bin/appletviewer: > register +- enable support for em86 (like binfmt_em86, for Alpha AXP only): + echo ":i386:M::\x7fELF\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03:\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfb\xff\xff:/bin/em86:" > register + echo ":i486:M::\x7fELF\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x06:\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfb\xff\xff:/bin/em86:" > register +- enable support for packed DOS applications (pre-configured dosemu hdimages): + echo ":DEXE:M::\x0eDEX::/usr/bin/dosexec:" > register +- enable support for DOS/Windows executables (using mzloader and dosemu/wine): + echo ":DOSWin:M::MZ::/usr/sbin/mzloader:" > register + echo ":DOS:E::com::/usr/sbin/mzloader:" > register + + +You can enable/disable binfmt_misc or one binary type by echoing 0 (to disable) +or 1 (to enable) to /proc/sys/fs/binfmt_misc/status or /proc/.../the_name. +Catting the file tells you the current status of binfmt_misc/the entry. + +You can remove one entry or all entries by echoing -1 to /proc/.../the_name +or /proc/sys/fs/binfmt_misc/status. + + +HINTS: +====== + +If your interpreter does not look at the PATH to determine the full name of the +program, you need to invoke a wrapper-script (like the following for java) first: + +#!/bin/sh +FOO=`which $1` || exit 1 +shift +/usr/local/bin/java $FOO ${1+$@} + + +There is a web page about binfmt_misc at +http://www.anatom.uni-tuebingen.de/~richi/linux/binfmt_misc.html + +Richard Günther, richard.guenther@student.uni-tuebingen.de |