Kernel: Start using multiboot2 instead of multiboot

This allows better compatibility with (U)EFI and gives RSDP location
instead of me having to scan ram to find it.

kernel/arch/x86_64/PageTable.cpp

@@ -4,6 +4,7 @@
 #include <kernel/LockGuard.h>
 #include <kernel/Memory/kmalloc.h>
 #include <kernel/Memory/PageTable.h>
+#include <kernel/multiboot2.h>
 
 extern uint8_t g_kernel_start[];
 extern uint8_t g_kernel_end[];
@@ -138,6 +139,16 @@ namespace Kernel
 		// Map (0 -> phys_kernel_end) to (KERNEL_OFFSET -> virt_kernel_end)
 		map_range_at(0, KERNEL_OFFSET, (uintptr_t)g_kernel_end - KERNEL_OFFSET, Flags::ReadWrite | Flags::Present);
 		
+		// Map multiboot info
+		vaddr_t multiboot_data_start = (vaddr_t)g_multiboot2_info & PAGE_ADDR_MASK;
+		vaddr_t multiboot_data_end = (vaddr_t)g_multiboot2_info + g_multiboot2_info->total_size;
+		map_range_at(
+			V2P(multiboot_data_start),
+			multiboot_data_start,
+			multiboot_data_end - multiboot_data_start,
+			Flags::ReadWrite | Flags::Present
+		);
+
 		// Map executable kernel memory as executable
 		map_range_at(
 			V2P(g_kernel_execute_start),

kernel/arch/x86_64/boot.S

@@ -1,11 +1,3 @@
-# Declare constants for the multiboot header
-.set ALIGN,			1<<0						# align loaded modules on page boundaries
-.set MEMINFO,		1<<1						# provide memory map
-.set VIDEOINFO,		1<<2						# provide video info
-.set MB_FLAGS,		ALIGN | MEMINFO | VIDEOINFO # this is the Multiboot 'flag' field
-.set MB_MAGIC,		0x1BADB002					# 'magic number' lets bootloader find the header
-.set MB_CHECKSUM,	-(MB_MAGIC + MB_FLAGS)		#checksum of above, to prove we are multiboot
-
 .set PG_PRESENT,	1<<0
 .set PG_READ_WRITE,	1<<1
 .set PG_PAGE_SIZE,	1<<7
@@ -15,19 +7,37 @@
 
 .code32
 
-# Multiboot header
+# multiboot2 header
 .section .multiboot, "aw"
-	.align 4
-	.long MB_MAGIC
-	.long MB_FLAGS
-	.long MB_CHECKSUM
-	.skip 20
-
+multiboot2_start:
+	.align 8
+	.long 0xE85250D6
 	.long 0
-	.long 800
-	.long 600
+	.long multiboot2_end - multiboot2_start
+	.long -(0xE85250D6 + (multiboot2_end - multiboot2_start))
+
+	# framebuffer tag
+	.align 8
+	.short 5
+	.short 0
+	.long 20
+	.long 1920
+	.long 1080
 	.long 32
 
+	# legacy start
+	.align 8
+	.short 3
+	.short 0
+	.long 12
+	.long V2P(_start)
+
+	.align 8
+	.short 0
+	.short 0
+	.long 8
+multiboot2_end:
+
 .section .bss, "aw", @nobits
  	# Create stack
 	.global g_boot_stack_bottom
@@ -40,11 +50,11 @@
 	g_kernel_cmdline:
 		.skip 4096
 
-	.global g_multiboot_info
-	g_multiboot_info:
+	.global g_multiboot2_info
+	g_multiboot2_info:
 		.skip 8
-	.global g_multiboot_magic
-	g_multiboot_magic:
+	.global g_multiboot2_magic
+	g_multiboot2_magic:
 		.skip 8
 
 .section .data
@@ -119,19 +129,6 @@ check_requirements:
 .exit:
 	jmp system_halt
 
-copy_kernel_commandline:
-	pushl %esi
-	pushl %edi
-	movl V2P(g_multiboot_info), %esi
-	addl $16, %esi
-	movl (%esi), %esi
-	movl $1024, %ecx
-	movl $V2P(g_kernel_cmdline), %edi
-	rep movsl
-	popl %edi
-	popl %esi
-	ret
-
 enable_sse:
 	movl %cr0, %eax
 	andw $0xFFFB, %ax
@@ -170,10 +167,9 @@ initialize_paging:
 _start:
 	# Initialize stack and multiboot info
 	movl $V2P(g_boot_stack_top), %esp
-	movl %eax, V2P(g_multiboot_magic)
-	movl %ebx, V2P(g_multiboot_info)
+	movl %eax, V2P(g_multiboot2_magic)
+	movl %ebx, V2P(g_multiboot2_info)
 
-	call copy_kernel_commandline
 	call check_requirements
 	call enable_sse
 
@@ -201,7 +197,7 @@ long_mode:
 	jmp *%rcx
 
 higher_half:
-	addq $KERNEL_OFFSET, g_multiboot_info
+	addq $KERNEL_OFFSET, g_multiboot2_info
 
 	# call global constuctors
 	call _init