Re: [uml-devel] kernel module support broken on x86-64?

[Boaz Harrosh <bharrosh@panasas.com>]

juergen.kadidlo@exasol.com wrote:
> Boaz Harrosh wrote:
>> juergen.kadidlo@exasol.com wrote:
>>   
>>> Boaz Harrosh wrote:
>>>     
>>>> juergen.kadidlo@exasol.com wrote:
>>>>   
>>>>       
>>>>> Hi!
>>>>>
>>>>>  I've compiled an UML kernel based on 2.6.25 but loading kernel modules 
>>>>> seems to be broken. No matter which module I try to load the output 
>>>>> looks similar to this:
>>>>>
>>>>>  overflow in relocation type 11 val 80836d41
>>>>> 'loop' likely not compiled with -mcmodel=kernel
>>>>>
>>>>> After searching for a while I found some threads from 2006 discussing 
>>>>> this issue, e.g.:
>>>>> http://www.mail-archive.com/user-mode-linux-devel@lists.sourceforge.net/msg03693.html
>>>>> and
>>>>> http://marc.info/?l=user-mode-linux-devel&m=115125101012707&w=2
>>>>>
>>>>> As Andi Kleen has mentioned in a mail from the first thread, simply 
>>>>> appending "-mcmodel=kernel" to the KBUILD_CFLAGS does not work (I tried 
>>>>> it anyway and can confirm his statement ;)
>>>>>
>>>>> Since I could not find any solution I've decided to write this mail and 
>>>>> ask about the current state of this issue and of course for a solution! 
>>>>> I simply don't want to believe that there is no loadable module support 
>>>>> for UML in 2008...
>>>>>
>>>>> Regards
>>>>> JK
>>>>>
>>>>>     
>>>>>         
>>>> Every thing is fine down here. What host Kernel-gcc-glibc / uml-gcc-glibc
>>>> are you using?
>>>>
>>>> I'm using out-of-tree modules with uml for every kernel since 2.6.19.
>>>> I have both Host and UML as x86_64 on FC7 with gcc 4.1.2
>>>>
>>>> Boaz
>>>>
>>>>   
>>>>       
>>> I'm glad to here that the bug has been fixed. Anyway, it does not work
>>> with my configuration:
>>>
>>>  - CentOS 5.1 as host system and UML root fs
>>>  - Kernel 2.6.25.4 (vanilla, but config taken from the CentOS kernel)
>>>  - GCC 4.1.2
>>>  - GLIBC 2.5
>>>
>>> Regards
>>> JK
>>>
>>>     
>>
>> I used to run with red-hat 4.5 so this should work.
>> 64 bit, right?
>>
>> From passed experience I've seen that UML will only
>> work if I first do "make ARCH=um defconfig"  and then
>> manually enable any needed options with make xconfig.
>> other wise it breaks in all kind of ways. Even doing
>> a make oldconfig on a good uml config file from older
>> kernel will not work. Try to do defconfig and see if
>> it loads at all.
>>
>> How do you compile and run the out-of-tree module
>> or is it one of the built in modules?
>>
>> Boaz
>>
>>   
> I tried what you've suggested and did the following:
> - make mrproper
> - make defconfig ARCH=um
> - make linux ARCH=um
> - make modules ARCH=um
> - make modules_install INSTALL_MOD_PATH=/path/to/mounted/uml_root_fs ARCH=um
> 
> It did not work (same result).
> 
> After that, I copied the kernel source to the uml-root-fs, started the
> UML and did a 'make clean' and 'make modules ARCH=um' inside the running
> UML, followed by a 'make modules_install'. Again, it did not work.
> 
> After that, I've extracted the kernel source again (completely vanilla)
> and restarted at 'make defconfig'. Same result.
> No module is loadable. They all have 'invalid fomrat' an the usage of
> the '-mcmodel=kernel' flag is suggested.
> 
> BTW : with the same sources (and the same commands as listed above) I've
> successfully built a fully working 32 bit UML kernel!
> 
> I've also tried kernel 2.6.24.7 with identical results.
> 
> Last but not least, I've tried the same with a fresh download of the
> 2.6.26 kernel. Unfortunately, this time there was another problem: the
> kernel exits with a panic on startup (tried to build it twice with the
> same result). According to the stack-trace, the panic happens somewhere
> inside "get_page_from_free_list()"...
> 
> I'm really running out of ideas right now, does anyone have some
> suggestions?
> 
> Regards
> JK
>  

It all works down here. Just a long shot you have installed uml_utilities
on the host ...

I run the uml from the root of the source tree like this:
./.build_um/vmlinux ubd0=/usr0/var/local/um/Fedora7-AMD64-root_fs eth0=tuntap,,,192.168.0.117 mem=256M
(The .build_um/ is because I use KBUILD_OUTPUT=.build_um so I can compile 
multiple targets from same source tree)

Maybe there is some package missing from the Linux image you are using.
You are using a 64bit Linux image with your 64bit kernel, yes?
Try to compare the 32 bit image with the 64bit one. See if they have
the same packages installed. I started with a ready made fedora7 uml
image and never really touched it much except the occasional yum install
of a library or two.

Boaz
  

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