[Qemu-devel] qemu + chroot with non native image

[James Boddington]

Have been having a bit of a play.

I used binfmt_misc to register qemu-ppc as the interpreter for ppc 
binaries. This allows me to run ppc binaries on my athlon with out having 
to specify qemu-ppc everytime.

This seems to be usefull when cross compiling a few packages that create an 
intermediate step that is built for the target instead of the build host. 
The binary fails to run and the build process stops. Using binfmt_misc + 
qemu-XXX allows this step to complete and the build can finish. 

For example texinfo-4.4 builds a binary part way though the build process 
and tries to use that binary to process a few files. This binary has been 
cross compiled and fails to run. Using the above idea I can cross compile 
this package. 

Python 2.2.x is another offender. A python binary is built that is then 
used to build python proper. The 1st python won't run because it is for 
the wrong arch. Using binfmt_misc + qemu-ppc the build was going fine 
until qemu-ppc seemed to go into a loop. Qemu-ppc sat just under 100% cpu 
doing nothing obvious until I killed the process.

Another use I have found for this is being able to chroot into a non native 
filesystem. I cross compile my sparc images (x86 -> sparc) because it is a 
lot quicker. So being able to chroot into the image is of interest to me.

For this exercise I built a toolchain for ppc-unknown-linux-gnu and cross 
compiled a small image. Placed a static qemu-ppc in opt/bin in the image. 
I have not tried to see if it can self host yet.

MAKEDEV bzip2 egg fileutils gcc gzip linux-headers ncurses sed tar wget 
bash diffutils file findutils glibc kbd make patch sh-utils texinfo zlib 
binutils ed filesystem gawk grep libtool mktemp procps shadow textutils

/var/tmp/ppc-image, Sat Feb 28 11:19:51
(address@hidden) uname -a
Linux fred.bedrock 2.4.24 #3 Fri Feb 27 21:41:37 EST 2004 i686 unknown 
unknown GNU/Linux

/var/tmp/ppc-image, Sat Feb 28 11:19:54
(address@hidden) chroot . /opt/bin/qemu-ppc /bin/bash

/, Sat Feb 28 01:20:03
(address@hidden) uname -a
Linux fred.bedrock 2.4.24 #3 Fri Feb 27 21:41:37 EST 2004 i686 unknown 
unknown GNU/Linux

/, Sat Feb 28 01:20:08
(address@hidden) file /bin/bash
/bin/bash: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 
(SYSV), for GNU/Linux 2.0.0, dynamically linked (uses shared libs), 
stripped

/, Sat Feb 28 01:20:15
(address@hidden) file /usr/bin/gcc
/usr/bin/gcc: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 
(SYSV), for GNU/Linux 2.0.0, dynamically linked (uses shared libs), 
stripped

/, Sat Feb 28 01:20:23
(address@hidden) /usr/bin/gcc -v
Reading specs from /usr/lib/gcc-lib/ppc-unknown-linux-gnu/3.3.3/specs
Configured with: ./configure --prefix=/usr --build=i686-pc-linux-gnu 
--host=ppc-unknown-linux-gnu --target=ppc-unknown-linux-gnu --disable-nls 
--enable-shared --enable-threads=posix --enable-languages=c,c++
Thread model: posix
gcc version 3.3.3

-- 

   James