On Sat, Oct 9, 2010 at 2:27 PM, Graeme Russ graeme.russ@gmail.com wrote:
On 09/10/10 16:50, Lei Wen wrote:
Hi,
I recently try to port our board code to new uboot, which has been changed to use new relocation scheme. But I found a very strange thing, that is if the uboot is loaded to the TEXT_BASE address, it could run without problem. But if it is loaded to a different place, it fail to boot up...
I check the code, and found that in the board_init_f, it calls the init_sequence which is stored as a data sector in the u-boot.bin file. While the new scheme use the fPIC, the code could locate the GOT table correctly, and it seem to forgot what the GOT table stores is context that is meaningful in TEXT_BASE, not the loaded base. That is to say, if the TEXT_BASE is 0xf00000, and loaded base is 0x500000, I found the GOT table also filled with 0xf0****, not the 0x50****. This leads the cpu loading wrong function address in the init_sequence table, and cause pc become invalid...
Am I missing something to switch to the new relocation scheme?
The ARM relocation schemes (there are two being evaluated - one which uses .got and another .rel.dyn) are both designed to relocate from TEXT_BASE to an upper memory location determined during DRAM init
x86 is the only arch that I know implements what you are describing (in a patch series in u-boot-x86/master but not yet in mainline)
Glad to know this info here. :-) But it let the uboot lose a good feature that let it boot itself to debug a new feature. In original scheme, the relocate operation is done before calling the init_sequence, so the problem here was gone.
So for the new relocation scheme currently on mainline code, we only could load the u-boot.bin to the TEXT_BASE in ram and transfer the control to it? And if do this, the relocate seems has no meaning here, since in the past experience we need the relocation for we need copy the rest of uboot code to the TEXT_BASE when start up at a different place at the very beginning.
Thanks, Lei