PROTECTED MODE BABY

bootloader.nasm

@@ -2,7 +2,14 @@ BITS 16
 %include "bootloader_macros.inc"
 %define STAGE1_BASE 0x7c00
 %define STAGE2_BASE (STAGE1_BASE + 0x200)
-%define GDT_BASE 0x0800
+%define PROTECED_MODE_BASE (STAGE2_BASE + 0x200)
+%define GDT 0x0800
+%define GDT_CodeSegIndex 1
+%define GDT_DataSegIndex 2
+%define GDT_CodeSegmentSelector GDT_Selector(GDT_CodeSegIndex, 0, 0)
+%define GDT_DataSegmentSelector GDT_Selector(GDT_DataSegIndex, 0, 0)
+%define VIDEO 0xB8000
+
 
 %define STACK_POINTER_MAX STAGE1_BASE-2	; Stack grows downwards from right under stage_1
 
@@ -114,9 +121,6 @@ NoChange:
 		jmp DiskReadError
 	.BreakTryReadLoop:
 
-	mov ax, 0x0013 ; AH=0 (Change video mode), AL=13h (Mode) = 320x200 - 256 colors
-	int 0x10 ; Video BIOS interrupt
-
 	jmp STAGE2_BASE
 
 DiskReadError:
@@ -172,28 +176,81 @@ Stage2:
 	mov si, A20Status
 	call PrintString
 
-	; Setup GDT
 
-	xor ax, ax
-	mov cx, 4
-	rep stosw
+	; mov ah, 0x05 ; switch display page
+	; mov al, 0x00 ; page 0
+	; int 0x10
+
+%if 0
+	mov ax, 0x4f02 ; VESA mode
+	mov bx, 0x0301 ; 132 cols by 60 rows
+	int 0x10 ; Video BIOS interrupt
+%elif 0
+	mov ax, 0x0013 ; AH=0 (Change video mode), AL=13h (Mode) = 320x200 - 256 colors
+	mov bx, 0
+	int 0x10 ; Video BIOS interrupt
+%else
+	mov ax, 0x0003
+	mov bx, 0
+	int 0x10
+%endif
+
+	; pusha
+	; mov ax, 0xA000
+	; mov es, ax
+	; mov ax, 7
+	; es mov [320*100 + 100], ax
+	; mov ax, 0xB800
+	; mov es, ax
+	; es mov WORD [0], 0x0748
+	; es mov WORD [2], 0x0769
+	; popa
+	; HALT
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;
+; Global Descriptor Table ;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;
+	%assign GDT_SIZE 0
+
+	GDT_NULL_ENTRY GDT
+	%assign GDT_SIZE (GDT_SIZE+8)
+
+	GDT_ENTRY (GDT + (GDT_CodeSegIndex*8)), 0x00000000, 0xffffffff, CodeRead, 0, 1
+	%assign GDT_SIZE (GDT_SIZE+8)
 
-	GDT_ENTRY 1, 0x0000, 0xffff, (SEG_CODE_EXRD|SEG_DESCTYPE(1)|SEG_PRES(1)|SEG_SAVL(0)|SEG_LONG(0)|SEG_SIZE(1)|SEG_GRAN(1)|SEG_PRIV(0))
-	GDT_ENTRY 2, 0x0000, 0xffff, (SEG_DATA_RDWR|SEG_DESCTYPE(1)|SEG_PRES(1)|SEG_SAVL(0)|SEG_LONG(0)|SEG_SIZE(1)|SEG_GRAN(1)|SEG_PRIV(0))
+	GDT_ENTRY (GDT + (GDT_DataSegIndex*8)), 0x00000000, 0xffffffff, DataMutable, 0, 1
+	%assign GDT_SIZE (GDT_SIZE+8)
+
+	; GDT_ENTRY 1, 0x0000, 0xffff, (SEG_CODE_EXRD|SEG_DESCTYPE(1)|SEG_PRES(1)|SEG_SAVL(0)|SEG_LONG(0)|SEG_32Bit(1)|SEG_GRAN(1)|SEG_PRIV(0)) ; 32 bit
+	; GDT_ENTRY 2, 0x0000, 0xffff, (SEG_DATA_RDWR|SEG_DESCTYPE(1)|SEG_PRES(1)|SEG_SAVL(0)|SEG_LONG(0)|SEG_32Bit(1)|SEG_GRAN(1)|SEG_PRIV(0)) ; 32 bit
 
 	cli
-	lgdt [GDTR]
+	lgdt [GDT_Record]
 
-	xchg bx, bx
 	mov eax, cr0
 	or al, 1       ; set PE (Protection Enable) bit in CR0 (Control Register 0)
 	mov cr0, eax
-	xchg bx, bx
 
-	jmp 8:ProtectedModeBaby ; 8: is for the first descriptor in the GDT that is not the null-descriptor
+	jmp ClearPrefetchQueue
+	nop
+	nop
+ClearPrefetchQueue:
+
+	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+	;; Manually assembled long jump
+	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+	db 0x66 ; 32bit override
+	db 0xea ; Long jump
+	dd PROTECED_MODE_BASE ; Absolute address
+	dw GDT_CodeSegmentSelector ; Descriptor Selector
 
+	; jmp GDT_CodeSegmentSelector:ProtectedModeBaby ; 8: is for the first descriptor in the GDT that is not the null-descriptor
 	HALT
 
+GDT_Record:
+	dw GDT_SIZE - 1 ; Size of GDT in bytes minus 1
+	dd GDT ; Linear address of GDT
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 %include "bootloader_A20.nasm"
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -201,25 +258,55 @@ SecondStageString: db "This is the second stage!", 13, 10, 0
 EnablingA20Str: db "Enabling A20...", 13, 10, 0
 A20Status: db "A20_Enabled="
 	.Bit: db '0', 13, 10, 0
-GDTR:
-	dw  24    ; Size of GDT in bytes minus 1
-	dd  GDT_BASE ; Linear address of GDT
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 	times 512-($-$$) db 0
+
 BITS 32
-segment ProtectedModeBaby vstart=0x8000
+segment ProtectedModeBaby vstart=PROTECED_MODE_BASE
 ProtectedModeBaby:
-	xchg bx, bx
-	mov eax, (1<<20)-1
-	add eax, 7
+	; Code segment updated by the long jump here
 
-	mov dl, 7 ; Grey color.
-	mov byte [0xA0000+edi], dl ; And we put the pixel
-	
-	; mov si, ProtectedWelcomeStr
-	; call PrintString ; Yes, we cannot use BIOS from proteced mode
+	; Update Other Segments
+	mov ax, GDT_DataSegmentSelector
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+
+	; Setup stack
+	mov esp, 0xffffffff
+
+	mov ecx, 2000
+	lea edi, [VIDEO]
+	xor ax, ax
+L1:
+	mov ah, cl
+	mov WORD [edi], ax
+	inc edi
+	inc edi
+	loop L1
+
+WriteProtectedModeString:
+	cld
+	lea esi, [ProtectedWelcomeStr]
+	lea edi, [VIDEO]
+.print_loop:
+	mov al, BYTE [esi]
+	test al, al
+	jz .break_print_loop
+	mov BYTE [edi], al
+	mov BYTE [edi+1], 0xf9
+	inc esi
+	inc edi
+	inc edi
+	jmp .print_loop
+.break_print_loop:
 
 	HALT
 
-	; ProtectedWelcomeStr: db "Protected Mode Baby!", 13, 10, 0
+;;;;;;;;;;;;;;;;;;;;;;;;
+;; Strings
+;;;;;;;;;;;;;;;;;;;;;;;;
+	ProtectedWelcomeStr: db "Protected Mode Baby! WHOOOOO YEAH!", 13, 10, 0

bootloader_macros.inc

@@ -16,37 +16,59 @@
 
 
 ; GDT Stuff
+%define Data 0000b
+%define DataMutable 0010b
+%define DataShrink 0100b
+%define DataShrinkMutable 0110b
+%define Code 1000b
+%define CodeRead 1010b
+%define CodeOnlyOwnPriv 1100b
+%define CodeOnlyOwnPrivRead 1110b
 
-; Each define here is for a specific flag in the descriptor.
-; Refer to the intel documentation for a description of what each one does.
-%define SEG_DESCTYPE(x)  ((x) << 4) ; Descriptor type (0 for system, 1 for code/data)
-%define SEG_PRES(x)      ((x) << 7) ; Present
-%define SEG_SAVL(x)      ((x) << 12) ; Available for system use
-%define SEG_LONG(x)      ((x) << 13) ; Long mode
-%define SEG_SIZE(x)      ((x) << 14) ; Size (0 for 16-bit, 1 for 32)
-%define SEG_GRAN(x)      ((x) << 15) ; Granularity (0 for 1B - 1MB, 1 for 4KB - 4GB)
-%define SEG_PRIV(x)     (((x) &  3) << 5)   ; Set privilege level (0 - 3)
-
-%define SEG_DATA_RD        0000b ; Read-Only
-%define SEG_DATA_RDA       0001b ; Read-Only, accessed
-%define SEG_DATA_RDWR      0010b ; Read/Write
-%define SEG_DATA_RDWRA     0011b ; Read/Write, accessed
-%define SEG_DATA_RDEXPD    0100b ; Read-Only, expand-down
-%define SEG_DATA_RDEXPDA   0101b ; Read-Only, expand-down, accessed
-%define SEG_DATA_RDWREXPD  0110b ; Read/Write, expand-down
-%define SEG_DATA_RDWREXPDA 0111b ; Read/Write, expand-down, accessed
-%define SEG_CODE_EX        1000b ; Execute-Only
-%define SEG_CODE_EXA       1001b ; Execute-Only, accessed
-%define SEG_CODE_EXRD      1010b ; Execute/Read
-%define SEG_CODE_EXRDA     1011b ; Execute/Read, accessed
-%define SEG_CODE_EXC       1100b ; Execute-Only, conforming
-%define SEG_CODE_EXCA      1101b ; Execute-Only, conforming, accessed
-%define SEG_CODE_EXRDC     1110b ; Execute/Read, conforming
-%define SEG_CODE_EXRDCA    1111b ; Execute/Read, conforming, accessed
-
-%macro GDT_ENTRY 4 ; GDTIndex Base Limit Attributes
-	mov word [es:GDT_BASE+(%1*8)+0], %3 & 0xffff     ; limit 0:15
-	mov word [es:GDT_BASE+(%1*8)+2], %2 & 0xffff     ; base 0:15
-	mov word [es:GDT_BASE+(%1*8)+4], ((%4 <<  8) & 0xff00) | ((%2 >> 16) & 0x00ff) ; access | base 16:23 
-	mov word [es:GDT_BASE+(%1*8)+6], ((%2 >> 16) & 0xff00) | ((%4 >> 16) & 0x00f0) | ((%3 >> 16) & 0x000f) ; base 24:31 | flags | limit 16:19
-%endmacro
+; %define DataAcc 0001b
+; %define DataMutableAcc 0011b
+; %define DataShrinkAcc 0101b
+; %define DataShrinkMutableAcc 0111b
+; %define CodeAcc 1001b
+; %define CodeReadAcc 1011b
+; %define CodeOnlyOwnPrivAcc 1101b
+; %define CodeOnlyOwnPrivReadAcc 1111b
+
+
+%macro GDT_NULL_ENTRY 1 ; address
+	%assign address %1
+	lea di, [address]
+	xor ax, ax
+	mov cx, 4
+	rep stosw
+%endmacro
+
+%macro GDT_ENTRY 6 ; address base limit type privilege bits32
+	%assign address %1
+
+	%assign base %2
+	%assign limit %3
+
+	%assign type (%4 & 0xf)
+	%assign reserved (1<<4)
+	%assign privilege ((%5 & 0x3) << 5)
+	%assign present (1<<7)
+	%assign access (present | privilege | reserved | type)
+	
+	%assign bits32 ((%6 & 1) << 2)
+	%assign granularity (1<<3)
+	%assign flags (granularity | bits32)
+
+	%assign limit_0_15 (limit & 0xffff)
+	%assign limit_16_19 ((limit >> 16) & 0xf)
+	%assign base_0_15 (base & 0xffff)
+	%assign base_16_23 ((base >> 16) & 0xff)
+	%assign base_24_31 ((base >> 24) & 0xff)
+
+	mov WORD [address + 0], limit_0_15
+	mov WORD [address + 2], base_0_15
+	mov WORD [address + 4], base_16_23 | (access << 8)
+	mov WORD [address + 6], limit_16_19 | (flags << 4) | (base_24_31 << 8)
+%endmacro
+
+%define GDT_Selector(DescriptorIndex, TableIndicator, RequestorPrivLevel) ((DescriptorIndex << 3) | ((TableIndicator & 1) << 2) | (RequestorPrivLevel & 0x3))

build

@@ -9,7 +9,7 @@ BuildSteps=(
 	"dd conv=notrunc if=./boot.bin of=./Floppy.img"
 	# "gcc -O0 -o ./VGA/grdemo.o ./VGA/grdemo.c"
 	# "objcopy -O binary ./VGA/grdemo.o ./grdemo.bin"
-	"qemu-system-x86_64 -drive format=raw,file=Floppy.img"
+	"qemu-system-x86_64 -vga cirrus -drive format=raw,file=Floppy.img"
 	# "bochs"
 )