Kernel: x86_64 boot script now makes GDT with null, kernel code and data

kernel/arch/x86_64/boot.S

@@ -10,19 +10,6 @@
 .set PG_READ_WRITE,	1<<1
 .set PG_PAGE_SIZE,	1<<7
 
-# GDT access byte
-.set GDT_A_A,	1<<40
-.set GDT_A_RW,	1<<41
-.set GDT_A_DC,	1<<42
-.set GDT_A_E,	1<<43
-.set GDT_A_S,	1<<44
-.set GDT_A_DPL,	1<<45
-.set GDT_A_P,	1<<47
-# GDT flags
-.set GDT_F_L,	1<<53
-.set GDT_F_DB,	1<<54
-.set GDT_F_G,	1<<55
-
 .code32
 
 # Multiboot header
@@ -40,9 +27,11 @@
 
 .section .bss, "aw", @nobits
  	# Create stack
-	stack_bottom:
+	.global g_boot_stack_bottom
+	g_boot_stack_bottom:
 		.skip 16384
-	stack_top:
+	.global g_boot_stack_top
+	g_boot_stack_top:
 	
 	.global g_kernel_cmdline
 	g_kernel_cmdline:
@@ -73,8 +62,9 @@ g_multiboot_magic:
 	.skip 8
 
 boot_gdt:
-	.quad 0																											# null descriptor
+	.quad 0x0000000000000000 # null descriptor
-	.quad (GDT_F_G | GDT_F_L ) | (GDT_A_P | (0 * GDT_A_DPL) | GDT_A_S | GDT_A_E | GDT_A_RW) | (0xF << 48 | 0xFFFF)	# kernel code
+	.quad 0x00AF9A000000FFFF # kernel code
+	.quad 0x00AF92000000FFFF # kernel data
 boot_gdtr:
 	.short . - boot_gdt - 1
 	.quad boot_gdt
@@ -171,7 +161,7 @@ initialize_paging:
 .type _start, @function
 _start:
 	# Initialize stack and multiboot info
-	movl $stack_top, %esp
+	movl $g_boot_stack_top, %esp
 	movl %eax, g_multiboot_magic
 	movl %ebx, g_multiboot_info
 
@@ -187,9 +177,11 @@ _start:
 
 .code64
 long_mode:
-	# clear segment registers
+	movw $0x10, %ax
-	movw $0x00, %ax
 	movw %ax, %ss
+
+	# clear segment registers (unused in x86_64?)
+	movw $0x00, %ax
 	movw %ax, %ds
 	movw %ax, %es
 	movw %ax, %fs