RE: Relocatable kernel for ppc44x

On Wed, 2011-06-15 at 10:30 +0100, David Laight wrote:

quoted

The PPC440X currently uses 256M TLB entries to pin the 
lowmem. When we go for a relocatable kernel we have to :

1) Restrict the kernel load address to be 256M aligned

OR

2) Use 16M TLB(the next possible TLB page size supported) 
entries till the first
256M and then use the 256M TLB entries for the rest of lowmem.

What is wrong with:

3) Use 256M TLB entries with the lowest one including
   addresses below the kernel base.

Clearly the kernel shouldn't be accessing the addresses
below its base address - but that is true of a lot of
address space mapped into the kernel.

In the case of a relocatable kernel it's perfectly kosher to access
addresses below the kernel itself... Typically this is used for kdump
where the kdump kernel excecutes in place in a reserved area but access
to the rest of memory is allowed to ... well, do the dump :-) There
could be other reasons to do that too.

Cheers,
Ben.