[U-Boot] Question about relocation

Albert ARIBAUD
2011-04-17T17:04:18Z

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.