Re: Idea: Move kernel to upper memory

[Robert Millan]

On Wed, Sep 03, 2008 at 04:15:33PM +0530, BVK Chaitanya wrote:
> Hi,
> 
> 
> What is the conclusion of this thread?  is this idea still explored?
> 
> 
> Robert Millan wrote:
> >
> >The first concern that comes to mind is how would GRUB coexist with the
> >payload area which precisely starts at 0x100000.  But I expect we'd face
> >many unexpected issues.
> >
> 
> Does this mean, GRUB needs to fit within 1MB limit when all its modules 
> are loaded?  More clearly, are there any limits on where (and how many) 
> grub modules can be dynamically loaded currently?
> 
> Since payload(s) needs to be present at their precise positions only 
> after the boot command, we can always deterministically /schedule/ 
> memmove operation to be executed as part of boot command.
> 
> Since boot command is the last command executed by GRUB (correct me if 
> not), we can overwrite any GRUB code/data at that point.  This also 
> needs boot command to exist in low memory.

This is already done.  See grub_multiboot_{forward,backward}_relocator
variables and how they're used in the multiboot loader.

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."