Hello Wolfgang,
On ma, 2014-05-19 at 20:30 +0200, Wolfgang Denk wrote:
Dear Jeroen Hofstee,
In message 1400523005.1985.33.camel@yellow you wrote:
mm, forget about U-Boot for a second and please consider the following, complicated, program:
I think we should NOT forget U-Boot, which comes with it's own, specifically tuned set of compiler options and linker scripts.
well it mentioned for a second...
compiled with `aarch64-linux-gnu-gcc -g -Wall hello.c` results in:
I have no idea how the tool chain was configured here, and what the linker script might look like.
for what it is worth: aarch64-linux-gnu-gcc (Ubuntu/Linaro 4.8.1-10ubuntu7) 4.8.1 with its default linker script.
Maybe. This is with some (unknown here) specific set of compiler options and linker statements. This does not mean that the same or silimar code will be generated for U-Boot,
Could be, but the vexpress_aemv8a shows the same pattern. It has around 1688 of adrp instructions.
or - if it really is - that this has to be like that. Eventually the tool chain needs some tweaking flags to tell it that we intend to relocate the image later?
I wondered about that. I could not find such a flag, nor did David think it exists.. [1]
The question is - where does such code get emitted? Is it generated from C code, or manually created assembly?
It is generated, there are no literal adrp instructions in U-boot. As far as I understand it, it is a compiler feature..
That depends on specific compiler options / linker settings, eventually?
Perhaps eventually. But for now it seems that also U-boot is forced to keep the relocation offset a multiple of 4k.
Regards, Jeroen
[1] http://lists.denx.de/pipermail/u-boot/2014-May/179741.html