x86_64 kernel relocation question

x86_64 kernel relocation question

[kevint]

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Hello,

I am relatively new to kexec, and am running into some problems with  
relocations when I try to use kexec to load several different X86_64  
kernels.  I think this is the correct list to post to, but please  
point me in the right direction if it isn't.

Here is some of the information on my test environment:

$ kexec --version
kexec-tools-testing 20071030 released 30th October 2007

$ uname -r
2.6.21.5

RHEL5 Kernel:
$ file /tmp/vmlinuz
/tmp/vmlinuz: ELF 64-bit LSB shared object, AMD x86-64, version 1,  
stripped

Buildroot generated kernel (bzImage) with initramfs:
# file /tmp/linux-kernel-2.6.21.5-x86_64
/tmp/linux-kernel-2.6.21.5-x86_64: Linux kernel x86 boot executable  
RO-rootFS, root_dev 0x801, swap_dev 0x5, Normal VGA

Here is the output I am getting:
(note:  I usually have more options, but i get same errors regardless)

$ kexec -l /tmp/vmlinuz
Unhandled rela relocation: 4258616

I noticed this line in the source file, kexec/arch/x86_64/kexec-elf- 
rel-x86_64.c:

die("Unhandled rela relocation: %lu\n", reloc_name(r_type));

I figured %lu should be %s, so I changed it, and got the following  
output:

$ kexec -l /tmp/vmlinuz
Unhandled rela relocation: R_X86_64_PLT32

I noticed that it is not handled by kexec/arch/x86_64/kexec-elf-rel- 
x86_64.c, so figured I either am trying to kexec an incompatible  
kernel image or this relocation needs to be handled.  I made it  
further by hacking in a (non-working) case for this relocation type,  
but then came across R_X86_64_GOTPCREL.  I don't think calculating  
the relocation address for a PLT or a GOT relocation is trivial, so I  
am hoping I am doing something else wrong.

I would appreciate any help you can provide.

Thank you!

********************************************
Kevin Tegtmeier
HPC-3 Scientific Computing Resources
Los Alamos National Laboratory
email:  kevint at lanl dot gov
********************************************




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Re: x86_64 kernel relocation question

[Bernhard Walle]

* kevint <kevint@lanl.gov> [2008-01-10 01:45]:
>
> I am relatively new to kexec, and am running into some problems with 
> relocations when I try to use kexec to load several different X86_64 
> kernels.  I think this is the correct list to post to, but please point me 
> in the right direction if it isn't.
>
> Here is some of the information on my test environment:
>
> $ kexec --version
> kexec-tools-testing 20071030 released 30th October 2007
>
> $ uname -r
> 2.6.21.5

Just to make sure, is CONFIG_RELOCATABLE set?

> $ kexec -l /tmp/vmlinuz
> Unhandled rela relocation: 4258616
>
> I noticed this line in the source file, 
> kexec/arch/x86_64/kexec-elf-rel-x86_64.c:
>
> die("Unhandled rela relocation: %lu\n", reloc_name(r_type));
>
> I figured %lu should be %s, so I changed it, and got the following output:

Can you make a patch and send it to this list so that it get fixed in
kexec-tools-testing? Cc Simon Horman <horms@verge.net.au>, the
maintainer.



        Bernhard

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