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[solved] Need help for cross-building ARM
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musv
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PostPosted: Sat Aug 13, 2016 9:13 pm    Post subject: [solved] Need help for cross-building ARM Reply with quote

Hi there,

I'm really struggling to install my NAS (ARMv7-a Marvell Armada 380), but I'm failing already in the first steps. OK, let's start:

As base I took Compiling with qemu_user_chroot

My steps:
  1. Create the crosscompiler with
    Code:
    crossdev -t armv7a-hardfloat-linux-gnueabi
    - works
  2. Unpack ARM-Stage 3 to /usr/armv7a-hardfloat-linux-gnueabi - works
  3. Start compiling the system according to the Gentoo-Wiki with
    Code:
    armv7a-hardfloat-linux-gnueabi-emerge -uva --keep-going @system
    - works as described for about 60 of 90 packages (unfortunately no gcc).
  4. Installing qemu user - got working after discovering a nasty missing USE-Flag and opening a bug report.
  5. modprobe and mount binfmt_misc and registering the handler in the proc system - works
  6. starting the binfmt-service - works
  7. Mounting the directories (dev, proc, portage) - works
  8. Code:
    chroot . /bin/bash --login
    - fails


I don't understand the logic of the last point. If we do a chroot we use the bash from the arm-system. This should fail due to the different architecture. And if I do so I get the expected:
Code:
chroot . /bin/bash --login
chroot: failed to run command '/bin/bash': No such file or directory


If I insert the previously compiled qemu-wrapper script (qemu-arm -cpu cortex-a9) I get:
Code:
chroot . /usr/local/bin/qemu-wrapper /bin/bash --login
bash: /usr/bin/dircolors: No such file or directory
bash: /bin/grep: No such file or directory
bash: /usr/bin/cut: No such file or directory

That's at least partly working. Some tests:
Code:
 ls
bash: /bin/ls: No such file or directory
 echo $PATH
 /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/bin:/usr/armv7a-hardfloat-linux-gnueabi/gcc-bin/4.9.3
 root /> /usr/local/bin/qemu-wrapper ls
 Error while loading ls: No such file or directory
 root /> /usr/local/bin/qemu-wrapper /bin/ls
 bin  boot  dev etc  home  lib  lost+found  media  mnt  opt  packages  proc  root  run  sbin  sys  tmp  usr  var
 root /> /usr/local/bin/qemu-wrapper /usr/bin/emerge
 emerge           emerge-webrsync 
 root /> /usr/local/bin/qemu-wrapper /usr/bin/emerge
 emerge           emerge-webrsync 
 root /> /usr/local/bin/qemu-wrapper /usr/bin/emerge -puND world
 Error while loading /usr/bin/emerge: Exec format error
 root /> /usr/bin/emerge -puNd world
 bash: /usr/bin/emerge: /usr/lib/python-exec/python-exec2-c: bad interpreter: No such file or directory


Questions:
  1. The chroot command: Am I doing something wrong or is the handbook wrong at this point?
  2. Do I have to call qemu-wrapper before every command? Or how do I proceed to compile the rest of the system within the qemu-target chroot?


Last edited by musv on Sun Aug 21, 2016 9:15 am; edited 1 time in total
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NeddySeagoon
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PostPosted: Sat Aug 13, 2016 9:27 pm    Post subject: Reply with quote

musv,

The chroot should work.

When the system tries to run the arm format binary, it will call the binfmt_misc handler for that format which in turn will start qemu to deal with the arm format.

You don't mention the
Code:
Install the static qemu into the chroot:
step.
That's the result of
Code:
quickpkg app-emulation/qemu

Code:
ROOT=$PWD/ emerge --usepkgonly --oneshot --nodeps qemu
so that the hosts statically built qemu is installed inside the chroot.
Its installed outside the chroot too but its the copy inside the chroot that will be used to run your arm code.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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musv
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PostPosted: Sun Aug 14, 2016 8:13 am    Post subject: Reply with quote

Thanks for your explanation. I guess my problem is located in the binfmt section. Something is there still wrong in my config.

If I try to install qemu I get a lot of warnings. But I think, that's still ok:
Code:
ROOT=$PWD/ emerge --usepkgonly -1 --nodeps qemu

 * IMPORTANT: 10 news items need reading for repository 'gentoo'.
 * Use eselect news read to view new items.

>>> Running pre-merge checks for app-emulation/qemu-2.6.0
 * qemu-2.6.0.tbz2 MD5 SHA1 size ;-) ...                                 [ ok ]
 * Determining the location of the kernel source code
 * Found kernel source directory:
 *     /usr/src/linux
 * Found kernel object directory:
 *     /lib/modules/4.5.0-gentoo/build
 * Found sources for kernel version:
 *     4.5.0-gentoo
 * Checking for suitable kernel configuration options...
 *   If you have an AMD CPU, you must enable KVM_AMD in your kernel configuration.
 * Please check to make sure these options are set correctly.
 * Failure to do so may cause unexpected problems.

>>> Emerging binary (1 of 1) app-emulation/qemu-2.6.0::gentoo for /usr/armv7a-hardfloat-linux-gnueabi/
 * qemu-2.6.0.tbz2 MD5 SHA1 size ;-) ...                                 [ ok ]
>>> Extracting info
>>> Extracting app-emulation/qemu-2.6.0

>>> Installing (1 of 1) app-emulation/qemu-2.6.0::gentoo to /usr/armv7a-hardfloat-linux-gnueabi/
 * QA Notice: Symbolic link /usr/share/qemu/vgabios.bin points to /usr/share/vgabios/vgabios.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/vgabios-vmware.bin points to /usr/share/vgabios/vgabios-vmware.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/vgabios-stdvga.bin points to /usr/share/vgabios/vgabios-stdvga.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/vgabios-qxl.bin points to /usr/share/vgabios/vgabios-qxl.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/vgabios-cirrus.bin points to /usr/share/vgabios/vgabios-cirrus.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/sgabios.bin points to /usr/share/sgabios/sgabios.bin which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-virtio.rom points to /usr/share/ipxe/1af41000.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-rtl8139.rom points to /usr/share/ipxe/10ec8139.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-pcnet.rom points to /usr/share/ipxe/10222000.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-ne2k_pci.rom points to /usr/share/ipxe/10500940.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-eepro100.rom points to /usr/share/ipxe/80861209.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/pxe-e1000.rom points to /usr/share/ipxe/8086100e.rom which does not exist.
 * QA Notice: Symbolic link /usr/share/qemu/bios.bin points to /usr/share/seabios/bios.bin which does not exist.
/sbin/ldconfig: /lib/libprocps.so.4.0.0 is for unknown machine 40.

/sbin/ldconfig: /lib/libc-2.22.so is for unknown machine 40.

/sbin/ldconfig: /lib/libkmod.so.2.3.0 is for unknown machine 40.

/sbin/ldconfig: /lib/libcrack.so.2 is for unknown machine 40.

/sbin/ldconfig: /lib/libip4tc.so.0.1.0 is for unknown machine 40.

/sbin/ldconfig: /lib/libpthread-2.22.so is for unknown machine 40.

/sbin/ldconfig: /lib/librt-2.22.so is for unknown machine 40.

 * app-emulation/qemu is using the deprecated readme.gentoo.eclass.
 * Please use readme.gentoo-r1 instead.

 * Messages for package app-emulation/qemu-2.6.0 merged to /usr/armv7a-hardfloat-linux-gnueabi/:

 *   If you have an AMD CPU, you must enable KVM_AMD in your kernel configuration.
 * Please check to make sure these options are set correctly.
 * Failure to do so may cause unexpected problems.
>>> Auto-cleaning packages...

>>> Using system located in ROOT tree /usr/armv7a-hardfloat-linux-gnueabi/

>>> No outdated packages were found on your system.

My host cpu is a Intel Xeon. So I didn't enable the KVM_AMD, which isn't used anyway for ARM emulation.

The binfmt stuff - Kernel:
Code:
 zgrep -i binfmt /proc/config.gz
CONFIG_BINFMT_ELF=y
CONFIG_COMPAT_BINFMT_ELF=y
CONFIG_BINFMT_SCRIPT=y
CONFIG_BINFMT_MISC=y

Should be ok. Or is it necessary to build as a module?

Registering the the handler:
Investigating the init-script, it doesn't to anything else than
Code:
   if [ $cpu != "arm" -a -x "/usr/bin/qemu-arm" ] ; then
      echo   ':arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff:/usr/bin/qemu-arm:'"${QEMU_BINFMT_FLAGS}" > /proc/sys/fs/binfmt_misc/register
   fi

As a difference to the handbook it calls qemu-arm and not the qemu-wrapper. About the QEMU_BINFMT_FLAGS I'm not sure.

Code:
la /proc/sys/fs/binfmt_misc/
-rw-r--r-- 1 root root 0 14. Aug 09:20 arm
--w------- 1 root root 0 14. Aug 09:20 register
-rw-r--r-- 1 root root 0 14. Aug 09:19 status

cat /proc/sys/fs/binfmt_misc/status
enabled

cat /proc/sys/fs/binfmt_misc/arm
enabled
interpreter /qemu-wrapper
flags:
offset 0
magic 7f454c4601010100000000000000000002002800
mask ffffffffffffff00fffffffffffffffffeffffff


Found the error:
/qemu-wrapper could not be found. It was located in /usr/local/bin. So I changed the path and it seems to work. Thanks a lot.
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musv
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PostPosted: Sun Aug 21, 2016 9:19 am    Post subject: Reply with quote

Just for information, if someone wants to use it:

I'm using systemd. There's a way not to be forced to build a static qemu-arm.

http://blog.oddbit.com/2016/02/07/systemd-nspawn-for-fun-and-well-mostly-f/

Instead of chroot, you can also use systemd-nspawn and mount the required libdir and the qemu-arm inside the chroot-environment. Nevertheless it's the same principle.
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