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Date: Sat, 24 Nov 2012 13:30:41 -0800
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Subject: Re: [PATCH v3 11/12] x86, boot: add fields to support load bzImage
 and ramdisk high
From: Yinghai Lu <yinghai@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        linux-kernel@vger.kernel.org, Rob Landley <rob@landley.net>,
        Matt Fleming <matt.fleming@intel.com>
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On Sat, Nov 24, 2012 at 11:50 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 11/24/2012 09:32 AM, H. Peter Anvin wrote:
>>
>> On 11/24/2012 04:37 AM, Eric W. Biederman wrote:
>>>
>>>
>>> Certainly /sbin/kexec isn't bothering to calculate the end of the setup
>>> header and just being far more conservative and using all of the 16bit
>>> real mode code as it's initializer.
>>>
>>
>> That's not conservative... that's just plain wrong.  It means you're
>> initializing the fields in struct boot_params with garbage instead of a
>> predictable value (zero).
>>
>> We could work around it with a sentinel hack... except you *also*
>> probably modify *some* fields and now we have a horrid mix of
>> initialized and uninitialized fields to sort out... and there really
>> isn't any sane way for the kernel to sort that out.
>>
>> We have a huge problem on our hands now because of it.
>>
>
> So, given the mess we now have on our hands... any suggestions how to best
> solve it?  There is the option of simply declaring old kexec binaries
> broken; they will then not work reliably with newer kernels, if they even
> work reliably now -- it is hard to know for certain.

yes, if the user updates kernel to be kexeced, then would be
reasonable to ask them to
update kexec-tools.