[parisc-linux] hack to use HPUX boot loader

[John David Anglin]

> The hpux boot loader assumes the text relocation address should also be
> used as a physical load address.  In the case of Linux, relocated
> at 3Gb, this clearly makes no sense.  It works fine for HP-UX which
> is relocated to, and runs in, low physical memory.
> 
> = Does anyone know why this was changed?
> 
> I assume the earlier linking was purely experimental, since I've been
> told (and haven't confirmed myself) that Linux 2.2.x essentially needs
> to be relocated at 3Gb (or some other big value) because it assumes
> it's available from the page tables of every process.  If
> Linux was relocated at addresses near zero, this would result in
> user programs having to start at addresses larger than the amount
> of memory used by the kernel, which would be weird.

Can't user programs be mapped with sr7 to OS public code while the kernel
runs in non-virtual mode in low physical memory?  When the kernel is
in virtual mode most of it might run with low virtual addresses.  I am
not an expert in Linux, so it is unclear to me how much of the system
needs to be visible to user apps.  However, I think for som apps we
want to achieve an app environment essentially identical to hp-ux so
hp compiled apps will run under pa linux.

-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)