Hi Albert,
If we use SPL, we do not have to relocate code, I think.
SPL doesn't have relocation that's why this code is not used there.
It is not what I meant.
If SPL can directly load the main u-boot image
to the DRAM address where it is linked,
we do not relocate the code in the main image.
Current behavior is that SPL is reading u-boot.img entry point which
can be in any location and jump to it and u-boot self relocate to the end of
memory.
If SPL adds u-boot directly to the location where it should run after relocation
then relocation is not needed.
To ensure this capability (based on my poor GOT/REL/RELA) experience it means
that SPL loads u-boot to that location and patch REL/RELA section based on this
location
and internal relocation should be skipped.
I've always thought the logical approach would be for SPL to calculate
where U-Boot would end up in RAM, copy it from wherever (NAND, NOR, MMC,
whatever) to the final location, perform the relocation fixups, then
jump straight into U-Boot. It's pretty much what the Dynamic Loader does
(particularly with address space layout randomization)
IOW, that SPL perform the work of relocate_code() in U-Boot -- at least,
on ARM, where REL/RELA is used.
This is definitely doable for REL/RELA case and it can also speedup boot process
Not sure about the speed-up, but never mind.
It will save a RAM to RAM copy of u-boot's text and data sections.
However, running the relocation code in SPL may be even slower
(depending on configuration of caches).
(I don't think there is easy way how to solve this with just GOT relocation
because
of that MANUAL_RELOC code which is patching arrays with function pointers).
Even without importing SPL in the equation, switching from GOT to
REL/RELA has enourmous advantages.
I must admit, I'm really rusty with GOT vs REL/RELA - anyone care to
give me a refresher?
But yes, only having to deal with REL/RELA sections will make the
relocation procedures much simpler
Regards,
Graeme
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