[gentoo-soc] Re: cross_container_support - progress report #9

[Jing Huang <jing.huang.pku@gmail.com>]

On Wed, Aug 1, 2012 at 5:01 PM, Jing Huang <jing.huang.pku@gmail.com> wrote:
> On Tue, Jul 31, 2012 at 7:30 PM, Luca Barbato <lu_zero@gentoo.org> wrote:
>> On 07/31/2012 05:45 PM, Jing Huang wrote:
>>> Hi,
>>>
>>> == Progress of last Week ==
>>>
>>> In the last week,  my qemu-linux patches had been reviewed by the qemu
>>> community.
>>>
>>> I investigated how to config dynamic libraries in lxc container.:
>>>
>>> 1. mount host's /lib /usr/lib /usr/local/lib to lxc container
>>>
>>> 2. modify lxc container's ld.so.conf to link these libs.
>>>
>>> 3. ldconfig -Nf /etc/ld.so.conf to make settings available. (The
>>> ld.so.cache will include arm libraries by default. How to ignore
>>> them?)
>>>
>>> I am still debugging this method.
>>>
>>> Additionally, I found I must execute "qemu-static-i386  x86-program"
>>> in lxc container to make it run. Is it right?
>>
>> No it is wrong, you should call the runtime linker.
>
> When I execute x86-program(builded with dynamic libraries) in lxc
> container, it shows:
> "bash: x86-program: No such file or directory"
>
> Obviously,  the container has not called the right dynamic
> linker(ld-linux.so) to interpret the x86-program.
> Maybe I could register this linker or the linker wrap to
> /proc/sys/fs/binfmt_misc ?

Hmm..  The root cause of this fault is:

./x86-program(built with dynamic libraries)
      -->load_elf_binary()
           -->open_exec("/lib/ld-linux.so.2");

lxc chroot lacks of /lib/ld-linux.so.2. This problem is a difficult
one. In my opinion, the following two steps are essential to solve it.

1. alter linker script to build x86-program using custom ld-linux.so.2
path ( /target/lib/ld-linux.so.2 ).

2. switch dynamic libraries to custom paths.
This point is relatively easy. I could use either LD_LIBRARY_PATH or
ld.so.conf.

"ldconfig /etc/ld.so.conf" is odd. I had altered ld.so.conf and
env.d/00basic to exclude original library path(/lib, /usr/lib,
/usr/local/lib), but the new generated cache file still include these
paths.
Unfortunately, linker will link libraries accroding to the ld cache
file unless declare  the DT_RPATH and LD_LIBRARY_PATH.

>
>>
>>> == Plans for this week ==
>>>
>>> 1. Still investigate dynamic libraries configure.
>>
>> It will take probably more time.
>>
>>> 2. wait for vapier's help. If it is possible, would you offer me the
>>> rough tech roadmap of patching crossdev and/or the toolchain eclass
>>> you mentioned last letter?
>>
>> First let's try to wrap up what we have now available and get more
>> people trying it =) That means document all the steps in the wiki and
>> get voluteers to try them.
>
> OK. I am doing it.
>
>>
>> lu
>>
>> --
>>
>> Luca Barbato
>> Gentoo/linux
>> http://dev.gentoo.org/~lu_zero
>>