UMbinfmt

The umbinfmt module can be loaded in the usual way:

$ um_add_service umbinfmt

Using Qemu to run foreign code

Mount umbinfmt on a directory, mounting it on the directory used by the kernel binfmt support makes all the existing binfmt scripts compatible with umbinfmt.

$ mount -t umbinfmt none /proc/sys/fs/binfmt_misc

The following commands:

$ echo ':ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x
00\x14:\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\x
ff\xff:/usr/bin/qemu-ppc:' > /proc/sys/fs/binfmt_misc/register
$ echo ':arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x
28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\x
ff\xff:/usr/bin/qemu-arm:' > /proc/sys/fs/binfmt_misc/register

define the emulators to be invoked when an exec system call tries to load ppc or arm executables. (each echo command must be typed on a single line. The commands have been split on several lines just to fit in the example box). It is also possible to use the script provided with Qemu sources qemu-binfmt-conf.sh commenting out the kernel module loading command: /sbin/modprobe binfmt_misc.

It is possible in this way to run foreign executables

$ uname -a
Linux [...] i686 GNU/Linux
$ file ./ls
./ls: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV), for GN
U/Linux 2.2.0, dynamically linked (uses shared libs), stripped
$ ./ls /
bin         etc         lost+found  proc        tmp
boot        lib         mnt         sbin        usr
$