Runtime stuff

Architecture/aarch64/runtime/crt0.S

@@ -0,0 +1,17 @@
+// .section ".text.boot"
+// 
+// .global _start
+//     .org 0x80000
+// _start:
+//     ldr     x5, =_start
+//     mov     sp, x5
+//     ldr     x5, =_kernel_rodata_end
+//     ldr     w6, =_bss_size
+// 1:  cbz     w6, 2f
+//     str     xzr, [x5], #8
+//     sub     w6, w6, #1
+//     cbnz    w6, 1b
+// 2:  bl      arm64Entry
+// Halt:
+//     wfe
+//     b Halt