Force the zero page of the kernel to be part of a segment

This will be necessary for limine and likely multiboot support. See the
comment in the linker scripts.

linkers/aarch64.ld

@@ -7,6 +7,19 @@ SECTIONS {
     . = KERNEL_OFFSET;
 
     . += SIZEOF_HEADERS;
+
+    /* Force the zero page to be part of a segment by creating a
+     * dummy section in the zero page.
+     * Limine will map the segment with the lowest vaddr value at
+     * 0xFFFFFFFF80000000 even if the segment has a higher vaddr.
+     * As such without the zero page being part of a segment, the
+     * kernel would be loaded at an offset from the expected
+     * location. As the redox kernel is not currently relocatable,
+     * this would result in a crash. A similar issue likely exists
+     * with multiboot/multiboot2 and the paddr of the segment.
+     */
+    .dummy ALIGN(8) : AT(ADDR(.dummy) - KERNEL_OFFSET) {}
+
     . = ALIGN(4096);
 
     .text : AT(ADDR(.text) - KERNEL_OFFSET) {
@@ -21,7 +34,7 @@ SECTIONS {
         __text_end = .;
     }
 
-	.rodata : AT(ADDR(.rodata) - KERNEL_OFFSET) {
+    .rodata : AT(ADDR(.rodata) - KERNEL_OFFSET) {
         __rodata_start = .;
         *(.rodata*)
 	. = ALIGN(4096);

linkers/i686.ld

@@ -8,6 +8,18 @@ SECTIONS {
 
     . += SIZEOF_HEADERS;
 
+    /* Force the zero page to be part of a segment by creating a
+     * dummy section in the zero page.
+     * Limine will map the segment with the lowest vaddr value at
+     * 0xFFFFFFFF80000000 even if the segment has a higher vaddr.
+     * As such without the zero page being part of a segment, the
+     * kernel would be loaded at an offset from the expected
+     * location. As the redox kernel is not currently relocatable,
+     * this would result in a crash. A similar issue likely exists
+     * with multiboot/multiboot2 and the paddr of the segment.
+     */
+    .dummy : AT(ADDR(.dummy) - KERNEL_OFFSET) {}
+
     .text ALIGN(4K) : AT(ADDR(.text) - KERNEL_OFFSET) {
         __text_start = .;
         *(.text*)

linkers/x86_64.ld

@@ -8,6 +8,18 @@ SECTIONS {
 
     . += SIZEOF_HEADERS;
 
+    /* Force the zero page to be part of a segment by creating a
+     * dummy section in the zero page.
+     * Limine will map the segment with the lowest vaddr value at
+     * 0xFFFFFFFF80000000 even if the segment has a higher vaddr.
+     * As such without the zero page being part of a segment, the
+     * kernel would be loaded at an offset from the expected
+     * location. As the redox kernel is not currently relocatable,
+     * this would result in a crash. A similar issue likely exists
+     * with multiboot/multiboot2 and the paddr of the segment.
+     */
+    .dummy : AT(ADDR(.dummy) - KERNEL_OFFSET) {}
+
     .text ALIGN(4K) : AT(ADDR(.text) - KERNEL_OFFSET) {
         __text_start = .;
         *(.text*)