[coreboot-gerrit] [XS] Change in coreboot[main]: include/memlayout.h: Add OPENSBI linker macro

[Maximilian Brune (Code Review)]

Attention is currently required from: Julius Werner, Patrick Rudolph, Philipp Hug, ron minnich.

Maximilian Brune has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/77974?usp=email )

Change subject: include/memlayout.h: Add OPENSBI linker macro
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Patch Set 5:

(1 comment)

File src/arch/riscv/include/arch/memlayout.h:

https://review.coreboot.org/c/coreboot/+/77974/comment/d682dce2_ad328cef :
PS5, Line 27: opensbi
> why not `REGION(opensbi, CONFIG_OPENSBI_TEXT_START, size, 4K)` ?

I am actually a little uncertain about that. If I choose to use:
`REGION(opensbi, CONFIG_OPENSBI_TEXT_START, size, 4K)`
then it would look like this in a memlayout file:
```
SECTIONS
{
    DRAM_START(FU540_DRAM)
    OPENSBI(128K)
    RAMSTAGE(FU540_DRAM + 128K, 2M)
    MEM_STACK(FU540_DRAM + 128K + 2M, 20K)
    POSTRAM_CBFS_CACHE(FU540_DRAM + 3M, 29M)
}
```
And that is very inconsistent, because all macros usually get an address and a size. As a reader I would look at this file and think that the OPENSBI macro is placed exactly at the location `FU540_DRAM`. But this may not be the case since I define it to be always at `CONFIG_OPENSBI_TEXT_START`. Without looking inside the macro itself it is very confusing on where it is placed.
Bottom line: I chose not to use `REGION(opensbi, CONFIG_OPENSBI_TEXT_START, size, 4K)` for readability reasons.