[coreboot] Relocable payloads

[Graeme Russ]

On Fri, Feb 26, 2010 at 12:26 PM, Stefan Reinauer <stepan at coresystems.de> wrote:
> On 2/26/10 2:23 AM, Stefan Reinauer wrote:
>
> On 2/25/10 11:44 PM, Myles Watson wrote:
>>
>> In case someone wants to look into this. The attached patch tries to do
>> relocable coreboot_ram. It does not work. It looks like dynamic linker
>> does not
>> fix call to hardware main in the c_start.o - reason is unknown.
>
> Relocating coreboot_ram seems like a great idea.  It seems like there was a
> lot of discussion on the mailing list with v3 about PIC and why it couldn't
> work for us.  My memory about it is fuzzy now, but a little searching might
> turn something up.

I have recently put a lot of effort into getting the x86 port of U-Boot to
fully relocatable. Have a look at the git tree of U-Boot. This is the one
that does all the work:

http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=commitdiff;h=1c409bc7101a24ecd47a13a4e851845d66dc23ce

>
> The idea sounds incredibly sweet.
>
> But lets make sure we gain from it in the end...
> Relocating coreboot_ram would safe us two 1MB sized memcpy on the resume
> path, so we would safe at least 200 microseconds of boot time in the case
> we're resuming. (assuming memory is 6.4G/s, DDR2-800 aka PC2-6400)  ....
> 0.2milliseconds of 400+... worth the complexity?
>
> minus the time added needed by the linker for the linking..
>
> How does linking go with lzma?
> - do the relocations require more RAM? How much?

Yes, but only a little. The binary size is larger as it needs the relocation
information table, but this does need need to be loaded into RAM.

> - can the sections and relocations be lzma'ed together? or are they separate
> files in CBFS?
>

Regards,

Graeme