fix LLVM

+ 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?

1 files changed, 8 insertions, 11 deletions

diff --git a/arch/riscv64/conf/kernel-link.S b/arch/riscv64/conf/kernel-link.S
index 88f2e75..e395e4a 100644
--- a/arch/riscv64/conf/kernel-link.S
+++ b/arch/riscv64/conf/kernel-link.S
@@ -5,12 +5,6 @@ OUTPUT_ARCH(riscv)
 ENTRY(main)
 
 SECTIONS {
-	/* This is apparently necessary. I *think* it is to tell the linker that
-	 * the kernel should be able to run in the bottom half of the address
-	 * space, but I don't know for sure and this feels like a fairly major
-	 * hack.
-	 * @todo look into this further.
-	 */
 	. = ABSOLUTE(VM_KERNEL);
 	__kernel_start = .;
 	.text ALIGN(4K) : AT(0) {
@@ -18,6 +12,14 @@ SECTIONS {
 		*(.text*);
 	}
 
+	/* place bss in between different load sections to force objcopy to
+	 * output zeroes for it */
+	.bss : {
+		*(.sbss*)
+		*(.bss*)
+		*(COMMON)
+	}
+
 	.rodata : {
 		*(.rodata*)
 	}
@@ -27,12 +29,7 @@ SECTIONS {
 		*(.sdata*)
 	}
 
-	.bss : {
-		*(.sbss*) *(.bss*) *(COMMON)
-	}
-
 	__kernel_end = .;
-	__kernel_size = __kernel_end - __kernel_start;
 
 	.garbage : {
 		*(.note*)