| Kernel Support for miscellaneous (your favourite) Binary Formats v1.1 |
| ===================================================================== |
| |
| This Kernel feature allows you to invoke almost (for restrictions see below) |
| every program by simply typing its 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' or '.exe'. |
| |
| 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 |
| name below /proc/sys/fs/binfmt_misc |
| - 'type' is the type of recognition. Give 'M' for magic and 'E' for 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 (without the '.', 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 reside 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. |
| |
| Think about the order of adding entries! Later added entries are matched first! |
| |
| |
| A few examples (assumed you are in /proc/sys/fs/binfmt_misc): |
| |
| - 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 Windows executables using wine: |
| echo ':DOSWin:M::MZ::/usr/local/bin/wine:' > register |
| |
| For java support see Documentation/java.txt |
| |
| |
| 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 you want to pass special arguments to your interpreter, you can |
| write a wrapper script for it. See Documentation/java.txt for an |
| example. |
| |
| Your interpreter should NOT look in the PATH for the filename; the |
| kernel passes it the full filename to use. Using the PATH can cause |
| unexpected behaviour and be a security hazard. |
| |
| |
| There is a web page about binfmt_misc at |
| http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html |
| |
| Richard Günther <rguenth@tat.physik.uni-tuebingen.de> |