[U-Boot] Question about relocation

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Alessandro,

Le 17/04/2011 03:19, Alessandro Rubini a ?crit :
> Hello.
> I'm trying to make at91sam9261ek working again, but relocation
> overlaps the destinatin address.
>
> In this board, u-boot runs already in RAM. This is exactly like the
> nhk8815 that I ported a few hours ago, but while there the IPL
> loaded our code at the beginning of RAM, in this case the IPL
> loaded us already at end of RAM.
>
> Now, this is the printout of the situation:
>
>      U-Boot code: 23F00000 ->  23F36EFC  BSS: ->  23F78570
>      monitor len: 00078570
>      ramsize: 04000000
>      TLB table at: 23ff0000
>      Top of RAM usable for U-Boot at: 23ff0000
>      Reserving 481k for U-Boot at: 23f64000
>      Reserving 180k for malloc() at: 23f37000
>      Reserving 24 Bytes for Board Info at: 23f36fe8
>      Reserving 144 Bytes for Global Data at: 23f36f58
>      New Stack Pointer is: 23f36f50
>      RAM Configuration:
>      Bank #0: 20000000 64 MiB
>      relocation Offset is: 00064000
>
> Since "tor len: 00078570" and "relocation Offset is: 00064000" the
> system data-aborts during relocation, as code overwrites relocation
> tables.
>
> What is the suggested solution? Changing the IPL is not acceptable for
> me, because it is an external tool used by everyone: everybody knows
> it loads and runs code at 23f0.0000.
>
> Thanks
> /alessandro

IIUC, the issue is with the moving of the image. One solution I see, and 
which is not 100% perfect, would be that the copy code perform either a 
beginning-to-end copy or an end-to-beginning copy depending on the 
source and destination addresses and size.

So, when copying say 256K from 0x01000000 to 0x03FC0000, the code could 
do the copy either way, beginning-to end (0x01000000 to 0x0103FFFF) or 
end-to-beginning (0x0103FFFF to 0x01000000); but when copying from 
0x03FB0000 to 0x03FC0000, only the end-to-beginning copy would be possible.

This still leaves holes in that copying U-Boot from RAM to RAM where the 
source is *really* near the end might actually trash the copy code 
itself. Maybe the instruction cache will help, but I won't bet on this 
without heavy testing.

Amicalement,
-- 
Albert.