feat(arm64): higher-half kernel, early MMU in boot, and VMM

Kernel/linker.ld

@@ -1,3 +1,8 @@
+ENTRY(_start)
+
+KERNEL_PA = 0x40100000;
+KERNEL_VA = 0xFFFFFFFF80100000;
+
 PHDRS
 {
   text PT_LOAD FLAGS(5); /* Read | Execute */
@@ -6,22 +11,31 @@ PHDRS
 
 SECTIONS
 {
-    . = 0x40100000;
+    . = KERNEL_VA;
     _kernelStart = .;
 
-    .text : {
+    .text : AT(ADDR(.text) - KERNEL_VA + KERNEL_PA) {
         *(.text.boot)
         *(.text*)
     } :text
 
     . = ALIGN(8);
-    .rodata : { *(.rodata*) } :text
+    .rodata : AT(ADDR(.rodata) - KERNEL_VA + KERNEL_PA) {
+        *(.rodata*)
+    } :text
     
     . = ALIGN(4096);
-    .data : { *(.data*) } :data
+    .data : AT(ADDR(.data) - KERNEL_VA + KERNEL_PA) {
+        *(.data*)
+    } :data
     
     . = ALIGN(8);
-    .bss : { *(.bss*) *(COMMON) } :data
+    .bss : AT(ADDR(.bss) - KERNEL_VA + KERNEL_PA) {
+        __bss_start = .;
+        *(.bss*)
+        *(COMMON)
+        __bss_end = .;
+    } :data
 
     . = ALIGN(4096);
     _kernelEnd = .;