On Monday, October 4, 2010, Wolfgang Denk wd@denx.de wrote:
Dear Albert ARIBAUD,
In message 4CA999EE.5030309@free.fr you wrote:
Note however that linking for base address 0 is not mandatory for achieving true position independence. What is required is that the code which runs from power-up until relocation be able to run anywhere, i.e., this code should not require any relocation fixup. That can be achieved on ARM by using only relative branches and accessing data only relative to pc (e.g. literals) or truly absolute (e.g. HW registers etc).
That means you need to build all of U-Boot that way, because significant parts of the code already run before relocation (including all clocks and timers setup, console setup, printf and all routines these pull in).
Have a look at x86 - Relocation is performed at the first possible moment
This made full relocation for x86 was relatively trivial :)
Regards,
Graeme