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+ Anything extern is right out as LLVM doesn't produce correct code for
them. Maybe if I added some extra attributes but I'm skeptical.
Replaced with static variables and getters/setters.
+ Inline ASM is apparently a bit buggy, so use an assembly stub when jumping to init.
+ Minimize work done in main() to minimize chance of LLVM doing something silly.
Still not 100% certain that I shouldn't just write the main() as an assembly stub
in arch/riscv64 to be absolutely sure everything works as intended.
+ Make .kernel.start section SHF_ALLOC, otherwise lld complains about
pc-relative addressing
Probably some other stuff as well that I'm forgetting right now. But at least with
LLVM14 LTO seems to work, which is pretty cool?
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+ Had some minor issues with a wraparound of size_t that effectively
meant that some regions were allocated twice. Also, booting should be
a bit more reliable now, turned out that the previous iteration of the
booting was just accidentally working due to the kernel being placed
'close enough' in RAM to where it was linked to. Fixed by allocating a
vmem of O1 that maps the kernel to a 2MiB boundary at boot, pretty
nifty.
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+ Apparently dbg_fdt() itself wasn't buggy, but for whatever reason GCC
produced an absolute load to the prefix string in __print_prefix()
which caused all the issues. Unclear why, seems like a compiler bug.
This commit is more of a workaround, I'd still like to investigate
this further.
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+ Took some fairly significant changes, for one the kernel is no longer
relocated at the start of a boot, instead it sits wherever the user
decides the kernel should sit. Similarly, the initial kernel stack and
page table are stored within the binary, slightly bloating the size
but making it much safer to boot since there's really no chance of us
overwriting the fdt or initrd in memory.
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+ May warn about PHDR not being in LOAD, there is a flag to silence it
(--no-warn-rwx-segment) but it doesn't seem to exist in
riscv64-unknown-elf for some reason.
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+ Release mode is sort of broken, as lto doesn't work with linker
relaxation and turning the relaxation off causes issues with the jump
from init to kernel (as I've currently implemented it, could probably
be fixed with a manual jump from assembly, I'll add it to my TODO
list)
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