-----Original Message----- From: u-boot-users-bounces@lists.sourceforge.net [mailto:u-boot-users-bounces@lists.sourceforge.net] On Behalf Of Haavard Skinnemoen Sent: den 25 juli 2008 14:19 To: kenneth johansson Cc: vb; u-boot-users@lists.sourceforge.net; Wolfgang Denk Subject: Re: [U-Boot-Users] Changing u-boot relocation scheme
On Fri, 25 Jul 2008 13:55:58 +0200 kenneth johansson kenneth@southpole.se wrote:
An ELF shared library has the dynamic relocations we need. So if we build u-boot as an .so file, it should work in theory on most architectures.
well the elf binary of u-boot obviously has everything we need regardless of what options it was compiled with. If we had a full linker at runtime we could just do a relink to whatever address we wanted.
No we couldn't if we don't have any relocation information. Just as you can't relink just any ELF binary to run at a different location after it's been through a final link, no matter how "full" the linker is.
And if the ELF file wasn't compiled as position-independent code to begin with, there's just no way it will ever work if it's loaded at a different address than it was linked at. You can't go through and fix up all the compiler-generated address calculations when you don't even have a clue where they are!
So whether or not the u-boot ELF file has everything we need depends a _lot_ on what options were used when building it.
Exactly.
It sounds a bit easier to just loop over a list of pointers and change the values than to implement a complete linker but maybe that is just me.
The question remains how should that list of pointers be generated? One possible answer is to let the linker do it (as dynamic relocations).
I think the best bet is to make -mrelocatable work for PPC. Question is how does the other arches do it? Do they include fixup ptrs by default or do they lack this functionality?
Jocke
Haavard