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MBR.asm
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; http://wiki.osdev.org/Entering_Long_Mode_Directly
; Entering Long Mode Directly
; From OSDev Wiki
; Jump to: navigation, search
; Demo Code
;
; The following NASM code demonstrates how to boot into 64 bit mode without entering protected mode:
; It works fine for BIOS forth debug engine prototype 64bits-MBR-1kf or UTS AH7139_01#04 hcchen5600 2011/06/13 20:55:00
; hcchen5600 2011/07/17 14:01:06 我終於想明白了，eforth64 should be org 0x100000
; but MBR should be org 0x7c00 , due to that I'll use NASM without LINKer so they
; must be separaged two .asm files.So now I have two source files,
; "c:\Users\8304018.WKSCN\Documents\My Dropbox\learnings\BIOS DEBUGGER FORTH ENGIN\eforth64\eforth64MBR.asm"
; "c:\Users\8304018.WKSCN\Documents\My Dropbox\learnings\BIOS DEBUGGER FORTH ENGIN\eforth64\eforth64.asm"
; hcchen5600 2011/08/10 08:30:19
; 之前的 64-bits MBR 只抓 2 tracks 2 * 9 = 18 k, 抓多一點吧！ eforth64_r5 $eval 寫好以後，帶
; forth source 空間需求不再微小。 ===> 多抓兩個 track 共 4 * 9 = 36K
TOTAL512K EQU 1 ; was 36k, final version 512K. Binary code + forth code total size read from floppy.
ORG 0x00007C00
BITS 16
FORTH_ENTRY equ 0x100000 ; eforth64 is at 2nd 1M memory
boot_loader:
;Parameter from BIOS: dl = boot drive
;Set default state
cli
xor bx,bx
mov es,bx
mov fs,bx
mov gs,bx
mov ds,bx
mov ss,bx
mov sp,0x7C00
sti
jmp 0:readsource
offsett dw 0
segmentt dw 0
cylinder db 0
head db 0
sector db 0
readsource:
%if TOTAL512K
; Load kernel from floppy disk
; eforth64 binary code and source code stored at cylinder 0 head 1 sector 1 total 512k
; buffer is at 1000:0~8000:0, will be moved to target position after switched to long mode.
mov cx,1024
.next call getdestination
call getcylinder
call getheadsector
call readsector
loop .next
jmp enablea20
getdestination:
mov ax,1024
sub ax,cx ; ax=block
mov bx,512
xor dx,dx
mul bx
mov [offsett],ax
shl dx,12 ; turn number of 64k into segment
add dx,1000h ; buffer base address
mov [segmentt],dx
ret
getcylinder:
mov ax,1024
sub ax,cx ; ax=block
add ax,18
mov bl,36
div bl
mov [cylinder],al
ret
getheadsector:
mov ax,1024
sub ax,cx ; ax=block
add ax,18 ; this is must, or head will be wrong
mov bl,18
div bl
and al,1
mov [head],al
add ah,1
mov [sector],ah
ret
readsector:
push cx
mov ax,[segmentt]
mov es,ax
mov bx,[offsett]
mov ax,0201h
mov ch,[cylinder]
mov cl,[sector]
mov dh,[head]
mov dl,0
int 13h
pop cx
ret
%elif
; Load kernel from floppy disk
; eforth64 binary code and source code stored at cylinder 1 head 0 sector 1 total 36k
; buffer is at 6000:0, will be moved to target position after switched to long mode.
; read 18 sectors, 9k , from cylinder 1 head 0 sector 1
mov ax,0x6000
mov es,ax
mov ax,0x0212 ;ah = Function 0x02 read, al = Number of sectors
xor bx,bx ;es:bx = Destination
mov cx,0x0101 ;cx = Cylinder and sector
xor dx,dx ;dx = Head and drive number
int 0x13 ;Int 0x13 Function 0x02 (Load sectors)
; read 18 sectors, 9k, from cylinder 1 head 1 sector 1
mov ax,0x0212 ;ah = Function 0x02 read, al = Number of sectors
mov bx,512*18*1 ;es:bx = Destination
mov cx,0x0101 ;cx = Cylinder and sector
mov dx,0x0100 ;dx = Head and drive number
int 0x13 ;Int 0x13 Function 0x02 (Load sectors)
; read 18 sectors, 9k, from cylinder 2 head 0 sector 1
mov ax,0x0212 ;ah = Function 0x02 read, al = Number of sectors
mov bx,512*18*2 ;es:bx = Destination
mov cx,0x0201 ;cx = Cylinder and sector
mov dx,0x0000 ;dx = Head and drive number
int 0x13 ;Int 0x13 Function 0x02 (Load sectors)
; read 18 sectors, 9k, from cylinder 2 head 1 sector 1
mov ax,0x0212 ;ah = Function 0x02 read, al = Number of sectors
mov bx,512*18*3 ;es:bx = Destination
mov cx,0x0201 ;cx = Cylinder and sector
mov dx,0x0100 ;dx = Head and drive number
int 0x13 ;Int 0x13 Function 0x02 (Load sectors)
%endif
enablea20:
;Enable A20 via port 92h
in al,92h
or al,02h
out 92h,al
;Build page tables
;The page tables will look like this:
;PML4:
;dq 0x000000000000b00f = 00000000 00000000 00000000 00000000 00000000 00000000 10110000 00001111
;times 511 dq 0x0000000000000000
;PDP:
;dq 0x000000000000c00f = 00000000 00000000 00000000 00000000 00000000 00000000 11000000 00001111
;times 511 dq 0x0000000000000000
;PD:
;dq 0x000000000000018f = 00000000 00000000 00000000 00000000 00000000 00000000 00000001 10001111
;times 511 dq 0x0000000000000000
;This defines one 2MB page at the start of memory, so we can access the first 2MBs as if paging was disabled
xor bx,bx
mov es,bx
cld
mov di,0xa000
mov ax,0xb00f
stosw
xor ax,ax
mov cx,0x07ff
rep stosw
mov ax,0xc00f
stosw
xor ax,ax
mov cx,0x07ff
rep stosw
mov ax,0x018f
stosw
xor ax,ax
mov cx,0x07ff
rep stosw
;Enter long mode
; 這段 CPU mode 的變化情形，進入本程式之前是 real mode
; <bochs:10> c
; (0) Caught mode switch breakpoint switching to 'real mode' Next at t=1851871
; (0) [0x00000000000fb67d] 0020:b67d (unk. ctxt): jmp far f000:b682 ; ea82b600f0
; <bochs:11> creg
; CR0=0x60000010: pg CD NW ac wp ne ET ts em mp pe
; CR2=page fault laddr=0x0000000000000000
; CR3=0x0000000000000000
; PCD=page-level cache disable=0
; PWT=page-level write-through=0
; CR4=0x00000000: osxsave pcid fsgsbase smx vmx osxmmexcpt osfxsr pce pge mce pae pse de tsd pvi vme
; EFER=0x00000000: ffxsr nxe lma lme sce
mov eax,10100000b ;Set PAE and PGE
mov cr4,eax
mov edx, 0x0000a000 ;Point CR3 at PML4
mov cr3,edx
mov ecx,0xC0000080 ;Specify EFER MSR
rdmsr ;Enable Long Mode
or eax,0x00000100
wrmsr
mov ebx,cr0 ;Activate long mode
or ebx,0x80000001 ;by enabling paging and protection simultaneously
mov cr0,ebx ;skipping protected mode entirely
; 切 CR0 後進入 compatibility mode，因為 EFER long mode 已經 enable 在先。
; <bochs:13> c
; (0) Caught mode switch breakpoint switching to 'compatibility mode'
; Next at t=14633426
; (0) [0x0000000000007c81] 0000:0000000000007c81 (unk. ctxt): lgdt ds:0x7ca3 ; 0f0116a37c
; <bochs:14> creg
; CR0=0xe0000011: PG CD NW ac wp ne ET ts em mp PE
; CR2=page fault laddr=0x0000000000000000
; CR3=0x000000000000a000
; PCD=page-level cache disable=0
; PWT=page-level write-through=0
; CR4=0x000000a0: osxsave pcid fsgsbase smx vmx osxmmexcpt osfxsr pce PGE mce PAE pse de tsd pvi vme
; EFER=0x00000500: ffxsr nxe LMA LME sce
lgdt [gdt.pointer] ; Bochs see actual instruction code is "LGDT ds:0x7ca3".
; load 80-bit gdt.pointer which is defined right below.
; Bochs 模擬出來: gdtr:base=0x0000000000007c8b, limit=0x17 即
; 以下 gdt.pointer 所在的位置。
; LGDT instruction 參考 DS 而所有的 segment register 都是 0000
; 上面本 MBR 一上手即已備妥。 org 7c00h 也絕對重要。造就這裡 GDTR
; 正確地得值 7C8B 如上述。
CLI ;inhibit all interrupts. Should do this before entering long mode I think. hcchen5600 2011/07/17 12:06:40
jmp gdt.code:startLongMode ; Load CS with 64 bit segment and flush the instruction cache
; Bochs see: jmp far 0008:7e00
startLongMode:
BITS 64
; Move eforth code to forth space.
%if TOTAL512K ; 512k final version
mov rcx,0x80000/4 ; length, move 512K from 0x10000 to 2nd 1M. Simple way.
mov rsi,0x10000 ; from
mov rdi,0x100000 ; to
CLD ; SI gets incremented
repz movsd
%elif ; 36K old version
mov rcx,0x10000/4 ; length, move 64K from 0x60000 to 2nd 1M. Simple way.
mov rsi,0x60000 ; from
mov rdi,0x100000 ; to
CLD ; SI gets incremented
repz movsd
%endif
; Now jump into eforth
; CLI ; inhibit all interrupts. This should be done
; before entering long mode. This is a must. Or will be trap to reset f000:fff0 soon.
; MOV AX,CS
; MOV DS,AX ;all in one segment
; MOV SS,AX
JMP FORTH_ENTRY
; Jump 之後正式變成 long mode
; <bochs:15> c
; (0) Caught mode switch breakpoint switching to 'long mode'
; Next at t=14633428
; (0) [0x0000000000007e00] 0008:0000000000007e00 (unk. ctxt): cli ; fa
; <bochs:16> creg
; CR0=0xe0000011: PG CD NW ac wp ne ET ts em mp PE
; CR2=page fault laddr=0x0000000000000000
; CR3=0x000000000000a000
; PCD=page-level cache disable=0
; PWT=page-level write-through=0
; CR4=0x000000a0: osxsave pcid fsgsbase smx vmx osxmmexcpt osfxsr pce PGE mce PAE pse de tsd pvi vme
; EFER=0x00000500: ffxsr nxe LMA LME sce
; <bochs:17>
;Global Descriptor Table
gdt:
dq 0x0000000000000000 ;Null Descriptor 第一個 GDT descriptor, 總是 null
.code equ $ - gdt
dq 0x0020980000000000 ; 第二個 code segment
.data equ $ - gdt
dq 0x0000900000000000 ; 第三個 data segment
.pointer: ;這是 load GDTR 時要準備好的東西。
dw $-gdt-1 ;16-bit Size (Limit) 這是 GDT 的 limit(長度-1)。以上共三個
dq gdt ;64-bit Base Address 這是 GDT 的 base address, 64 bits
;Changed from "dd gdt"
;Ref: Intel System Programming Manual V1 - 2.1.1.1
times 510-($-$$) db 0 ;Fill boot sector
dw 0xAA55 ;Boot loader signature