[U-Boot] [PATCH 6/6] powerpc: Add LINK_OFF calls in early C-code.

[Scott Wood]

On Tue, 23 Nov 2010 22:03:36 +0100
Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:

> Scott Wood <scottwood at freescale.com> wrote on 2010/11/23 21:46:51:
> > "Only these" that you've found so far, for the board you've tried --
> 
> Yes, that is what I wrote.

Yes, I was just emphasizing that. :-)

> > is it worth adding another pre-relocation landmine to shrink the image
> > by 5%?  I don't miss the manual fixups we had to do under the old
> > relocation scheme.
> 
> -msingle-pic-base does not require LINK_OFF per se. It will shrink the image
> significantly for free. It enables impl. of true PIC and if you want to have
> that too you need LINK_OFF.

What is "true PIC" versus the rest of what -msingle-pic-base does, and
what are the advantages?

> > Is a missing LINK_OFF likely to result in a crash, or silent bad
> > behavior?  Will LINK_OFF be a no-op after relocation?
> 
> Either crash or garbage printed on the port.

Garbage possibly being empty strings that aren't noticed?

Or possibly bad values changing program flow in nonobvious ways?

> LINK_OFF is a NOP after relocation. It will be a NOP
> if link address == load address too.

"load address" being pre-relocation?  Currently these must be equal
(which doesn't seem particularly burdensome).

Seems like there would be a high risk for a developer of board A to add
new code that affects board B, and needs a manual relocation, but board
A doesn't use this or loads at the link address, so it doesn't show up.
Seems like a maintenance headache.

-Scott