Prepare for higher half - map entire lower 4 GB

x86/kernel.ld

 ENTRY(kstart)
+OUTPUT_FORMAT(elf64-x86-64)
+
+KERNEL_OFFSET = 0;
 
 SECTIONS {
-    kernel_base = 0x101000;
-	. = kernel_base;
+    . = 0x100000;
+
+    . += SIZEOF_HEADERS;
+    . = ALIGN(4096);
+
+	. += KERNEL_OFFSET;
 
-    .text : AT(ADDR(.text) - kernel_base) {
+    .text : AT(ADDR(.text) - KERNEL_OFFSET) {
         __text_start = .;
         *(.text*)
 		. = ALIGN(4096);
         __text_end = .;
     }
 
-	.rodata : AT(ADDR(.rodata) - kernel_base) {
+	.rodata : AT(ADDR(.rodata) - KERNEL_OFFSET) {
         __rodata_start = .;
         *(.rodata*)
 		. = ALIGN(4096);
         __rodata_end = .;
     }
 
-    .data : AT(ADDR(.data) - kernel_base) {
+    .data : AT(ADDR(.data) - KERNEL_OFFSET) {
         __data_start = .;
         *(.data*)
 		. = ALIGN(4096);
         __data_end = .;
     }
 
-    .bss : AT(ADDR(.bss) - kernel_base) {
+    .bss : AT(ADDR(.bss) - KERNEL_OFFSET) {
         __bss_start = .;
         *(.bss*)
         . = ALIGN(4096);
@@ -33,8 +40,9 @@ SECTIONS {
     }
 
     /DISCARD/ : {
-        *(.comment)
-        *(.eh_frame)
-        *(.rel.eh_frame)
+        *(.comment*)
+        *(.eh_frame*)
+        *(.note*)
+        *(.rel.eh_frame*)
     }
 }

x86/startup-x86_64.asm

@@ -53,7 +53,7 @@ startup_arch:
 
     xor edi, edi
     xor eax, eax
-    mov ecx, 3 * 4096 / 4 ;PML4, PDP, PD / moves 4 Bytes at once
+    mov ecx, 6 * 4096 / 4 ;PML4, PDP, 4 PD / moves 4 Bytes at once
     cld
     rep stosd
 
@@ -63,12 +63,15 @@ startup_arch:
     add edi, 0x1000
     ;Link last PML4 to PML4
     mov DWORD [es:edi - 8], 0x70000 | 1 << 1 | 1
-    ;Link first PDP to PD
+    ;Link first four PDP to PD
     mov DWORD [es:edi], 0x72000 | 1 << 1 | 1
+    mov DWORD [es:edi + 8], 0x73000 | 1 << 1 | 1
+    mov DWORD [es:edi + 16], 0x74000 | 1 << 1 | 1
+    mov DWORD [es:edi + 24], 0x75000 | 1 << 1 | 1
     add edi, 0x1000
     ;Link all PD's (512 per PDP, 2MB each)y
     mov ebx, 1 << 7 | 1 << 1 | 1
-    mov ecx, 512
+    mov ecx, 4*512
 .setpd:
     mov [es:edi], ebx
     add ebx, 0x200000
@@ -100,6 +103,8 @@ startup_arch:
     or ebx, 1 << 31 | 1 << 16 | 1                ;Bit 31: Paging, Bit 16: write protect kernel, Bit 0: Protected Mode
     mov cr0, ebx
 
+    xchg bx, bx
+
     ; far jump to enable Long Mode and load CS with 64 bit segment
     jmp gdt.kernel_code:long_mode