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Diffstat (limited to 'Documentation/binfmt_misc.txt')
| -rw-r--r-- | Documentation/binfmt_misc.txt | 131 |
1 files changed, 0 insertions, 131 deletions
diff --git a/Documentation/binfmt_misc.txt b/Documentation/binfmt_misc.txt deleted file mode 100644 index ec83bbce547a..000000000000 --- a/Documentation/binfmt_misc.txt +++ /dev/null @@ -1,131 +0,0 @@ - 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'. - -First you must mount binfmt_misc: - mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc - -To actually register a new binary type, you have to set up a string looking like -:name:type:offset:magic:mask:interpreter:flags (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; cannot contain slashes '/' for obvious - reasons. - - '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...'). Ignored - when using filename extension matching. - - 'magic' is the byte sequence binfmt_misc is matching for. The magic string - may contain hex-encoded characters like \x0a or \xA4. Note that you must - escape any NUL bytes; parsing halts at the first one. In a shell environment - you might 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, and slashes '/' are not allowed! - - '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. Note that you must - escape any NUL bytes; parsing halts at the first one. Ignored when using - filename extension matching. - - 'interpreter' is the program that should be invoked with the binary as first - argument (specify the full path) - - 'flags' is an optional field that controls several aspects of the invocation - of the interpreter. It is a string of capital letters, each controls a - certain aspect. The following flags are supported - - 'P' - preserve-argv[0]. Legacy behavior of binfmt_misc is to overwrite - the original argv[0] with the full path to the binary. When this - flag is included, binfmt_misc will add an argument to the argument - vector for this purpose, thus preserving the original argv[0]. - e.g. If your interp is set to /bin/foo and you run `blah` (which is - in /usr/local/bin), then the kernel will execute /bin/foo with - argv[] set to ["/bin/foo", "/usr/local/bin/blah", "blah"]. The - interp has to be aware of this so it can execute /usr/local/bin/blah - with argv[] set to ["blah"]. - 'O' - open-binary. Legacy behavior of binfmt_misc is to pass the full path - of the binary to the interpreter as an argument. When this flag is - included, binfmt_misc will open the file for reading and pass its - descriptor as an argument, instead of the full path, thus allowing - the interpreter to execute non-readable binaries. This feature - should be used with care - the interpreter has to be trusted not to - emit the contents of the non-readable binary. - 'C' - credentials. Currently, the behavior of binfmt_misc is to calculate - the credentials and security token of the new process according to - the interpreter. When this flag is included, these attributes are - calculated according to the binary. It also implies the 'O' flag. - This feature should be used with care as the interpreter - will run with root permissions when a setuid binary owned by root - is run with binfmt_misc. - 'F' - fix binary. The usual behaviour of binfmt_misc is to spawn the - binary lazily when the misc format file is invoked. However, - this doesn't work very well in the face of mount namespaces and - changeroots, so the F mode opens the binary as soon as the - emulation is installed and uses the opened image to spawn the - emulator, meaning it is always available once installed, - regardless of how the environment changes. - - -There are some restrictions: - - the whole register string may not exceed 1920 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 - -To use binfmt_misc you have to mount it first. You can mount it with -"mount -t binfmt_misc none /proc/sys/fs/binfmt_misc" command, or you can add -a line "none /proc/sys/fs/binfmt_misc binfmt_misc defaults 0 0" to your -/etc/fstab so it auto mounts on boot. - -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 (or the file descriptor) to use. Using $PATH can -cause unexpected behaviour and can be a security hazard. - - -Richard Günther <rguenth@tat.physik.uni-tuebingen.de> |