Kexec for ARM: Is it expected to load old kernels?

Kexec for ARM: Is it expected to load old kernels?

[Brian Smucker]

Hi,

I use kexec to load a new 2.6.32 kernel and things work fine.  However 
when I try to use kexec to load a 2.6.21 kernel (ARM architecture) , it 
hangs after the "Bye!" message.

Is this to be expected?

If not, how can I debug things further?

Thanks,

Brian

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Re: Kexec for ARM: Is it expected to load old kernels?

[Andrea Adami]

Brian,

I suppose you need the ATAG changes introduced in 2.6.24 in order to
boot an arm kernel from kexec.
There are around patches for 2.6.22 and 2.6.23
(http://docs.openmoko.org/trac/ticket/930).

See amongst others:

[ARM] 4599/1: Preserve ATAG list for use with kexec (2.6.23)
[ARM] 4836/1: Make ATAGS_PROC depend on KEXEC


Regards

Andrea

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Re: Kexec for ARM: Is it expected to load old kernels?

[Brian Smucker]

Hi

So it appears I cannot load pre-2.6.24 kernels ARM kernels.  I have some 
further questions.

Is this an ARM-only thing?

If I want to load an arbitrary kernel, am I out of luck?

I thought theoretically kexec was able to execute arbitrary elf 
binaries, non-kernals, etc.  Is this true, or only my own misconception?

Or is it true in general, but not for ARM?

If it is not true for ARM, can I fix it?

I would like kexec to be able to boot old,old kernels, of the 2.4.16 
vintage.

Can you help answer these questions?

Thanks,

Brian



Andrea Adami wrote:
> Brian,
>
> I suppose you need the ATAG changes introduced in 2.6.24 in order to
> boot an arm kernel from kexec.
> There are around patches for 2.6.22 and 2.6.23
> (http://docs.openmoko.org/trac/ticket/930).
>
> See amongst others:
>
> [ARM] 4599/1: Preserve ATAG list for use with kexec (2.6.23)
> [ARM] 4836/1: Make ATAGS_PROC depend on KEXEC
>
>
> Regards
>
> Andrea
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>   


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Re: Kexec for ARM: Is it expected to load old kernels?

[Brian Smucker]

Hello,

Is there someone who can answer these questions out there?

Perhaps you could give a name of someone who could help.

Thanks,

Brian

Brian Smucker wrote:
> Hi
>
> So it appears I cannot load pre-2.6.24 kernels ARM kernels.  I have 
> some further questions.
>
> Is this an ARM-only thing?
>
> If I want to load an arbitrary kernel, am I out of luck?
>
> I thought theoretically kexec was able to execute arbitrary elf 
> binaries, non-kernals, etc.  Is this true, or only my own misconception?
>
> Or is it true in general, but not for ARM?
>
> If it is not true for ARM, can I fix it?
>
> I would like kexec to be able to boot old,old kernels, of the 2.4.16 
> vintage.
>
> Can you help answer these questions?
>
> Thanks,
>
> Brian


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Re: Kexec for ARM: Is it expected to load old kernels?

[Eric W. Biederman]

Brian Smucker <bsmucker@anabaptists.org> writes:

> Hello,
>
> Is there someone who can answer these questions out there?
>
> Perhaps you could give a name of someone who could help.

kexec is designed to boot arbitrary kernels.  How well you can do that
depends on how close the system can be returned to a state similar to
reset, and how robust the kernel you are booting is.

If you can get /sbin/kexec to reproduce your normal boot protocol it
is likely you can get an newer kernel to boot an older one.

Eric

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Re: Kexec for ARM: Is it expected to load old kernels?

[Eric W. Biederman]

Brian Smucker <bsmucker@anabaptists.org> writes:

> Hello,
>
> Is there someone who can answer these questions out there?
>
> Perhaps you could give a name of someone who could help.

kexec is designed to boot arbitrary kernels.  How well you can do that
depends on how close the system can be returned to a state similar to
reset, and how robust the kernel you are booting is.

If you can get /sbin/kexec to reproduce your normal boot protocol it
is likely you can get an newer kernel to boot an older one.

Eric

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