Re: should kernel image destination address be picked up by kernel itself?

[ebiederm@xmission.com (Eric W. Biederman)]

"Ming Lei" <mlei@Brocade.COM> writes:

> Hi Eric,
>
> I tried run latest kexec-tools v2.0 on ppc freescale 85xx platforms.
>
>>- All of the policy decisions are made in user space (such as where to
>>  execute from)
> Is where to execute from the physical address or the virtual address?
> How do we know it is available to kexec, it may be taken.

It should be physical and there should be an API in linux like
/proc/iomem which will report which addresses are memory.  ppc
is a little different than x86 so I'm not up to speed on how it
reports things.  I think it is with the device tree.

>>- standalone executables are loaded into an address space where
>>  physical address and virtual address are the same.
> There may be case that physical address and virtual address not the same
> on linux, such as vmalloc.

In the environment that kexec exports there should not be any.

>>What problem do you see in that model?
>>Why is it a problem for you?
>
> Can we put something like -1 to indicate to kernel that user space wants
> kernel to choose the virtual address to load the standalone executable,
> then linux kernel can kmalloc this area and then load the standalone
> executable.

You can do something like create a proper static ET_DYN executable and then 
/sbin/kexec will look for an address and load it there.

Eric

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