Le 30/10/2010 21:21, Wolfgang Denk a écrit :
Dear Albert ARIBAUD,
In message4CCC69E4.8090103@free.fr you wrote:
ldr r0, _TEXT_BASE /* r0<- Text base */ %%% why are we using _TEXT_BASE here and not _start?
Because we're accessing the relocation tables in the FLASH (or freshly NAND-loaded) "source" copy of u-boot, not in the RAM "target" copy (in which the relocation tables won't exist).
Sorry, but I don't understand this explanation.
With the linker script we make sure that the symbol _start gets linked to the absolute address CONFIG_SYS_TEXT_BASE, right? And _TEXT_BASE is a storage that holds exactly the value CONFIG_SYS_TEXT_BASE, which should be identical to the address of _start ?
Somehow I thought the question was "why use the source location rather than the target".
Yes, if we're still running from the "source" address at that point, the value of _start and the content of _TEXT_BASE should be the same -- that does change once we start the fixup loop, though; after the loop is done, I think "adr r0, _start" will still give us the source start address but _TEXT_BASE will contain the target start address -- though at this time of the evening I'd want to be careful about that.
Tomorrow morning I'll run a step-by-step case on my ED Mini V2 and on my OpenRD and see if / where we can use "adr rX, _start".
Best regards,
Wolfgang Denk
Amicalement,