[U-Boot] armv8 relocation questions

[Jeroen Hofstee <dasuboot@myspectrum.nl>]

Hello Tom,

On vr, 2014-05-16 at 17:15 -0400, Tom Rini wrote:
> On Fri, May 16, 2014 at 10:28:25PM +0200, Wolfgang Denk wrote:
> > Dear Darwin,
> > 
> > In message <53763B78.6030801@broadcom.com> you wrote:
> > >
> > > 3. Fixed offset case:
> > > CONFIG_SYS_TEXT_BASE = 0x88000020
> > 
> > You completely fail to respond to my repeated statement that a
> > CONFIG_SYS_TEXT_BASE like this is bogus.
> 
> This.  What the heck is going on?  CONFIG_SYS_TEXT_BASE is where the
> text section ends up, and the rest of the binary that follows, until we
> relocate.  If we're being loaded by something else, it needs to be
> placing us at the right spot.  If there's some header on top of the
> image to be considered by the loader, adjust where THAT loads us.  If we
> cannot, then you must change CONFIG_SYS_TEXT_BASE around.  Pad things
> up a bit for proper alignment.  It seems where somewhere around "Doctor,
> it hurts when I hit myself with a hammer!" and can't stop hammering our
> poor finger.


Not really I guess, I read it as "Doctor, it hurts when I hit myself
with a hammer!" But morphine prevents it to hurt, so everybody should
use morphine.

But a bit more serious, as far as understood it u-boot is loaded to the
CONFIG_SYS_TEXT_BASE being set, but not aligned to the requirements of
adrp (which assumes 4k). Did someone find a decent description of adrp
and how it should be relocated? Is adrp always required or an
optimization?

And yes, obviously obeying alignment requirements before and after
relocating obviously helps, but I am also curious how Darwin gets away
with this by adding an offset (in the wrong direction) and if this would
always work (given the former is fixed).

And yes, I don't know a single thing about arm64 so perhaps above sounds
completely stupid...

Regards,
Jeroen