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: (where you can choose the ':' upon
+: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
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)
+ - '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].
+ '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.
+
There are some restrictions:
- the whole register string may not exceed 255 characters
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.
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.
+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.
There is a web page about binfmt_misc at
-http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html
+http://www.tat.physik.uni-tuebingen.de
-Richard Günther <rguenth@tat.physik.uni-tuebingen.de>
+Richard Günther <rguenth@tat.physik.uni-tuebingen.de>
projects / linux-flexiantxendom0-3.2.10.git / blobdiff