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214 lines
5.0 KiB
214 lines
5.0 KiB
;
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; setup.s (C) 1991 Linus Torvalds
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;
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; setup.s is responsible for getting the system data from the BIOS,
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; and putting them into the appropriate places in system memory.
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; both setup.s and system has been loaded by the bootblock.
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;
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; This code asks the bios for memory/disk/other parameters, and
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; puts them in a "safe" place: 0x90000-0x901FF, ie where the
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; boot-block used to be. It is then up to the protected mode
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; system to read them from there before the area is overwritten
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; for buffer-blocks.
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;
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; NOTE; These had better be the same as in bootsect.s;
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INITSEG equ 0x9000 ; we move boot here - out of the way
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SYSSEG equ 0x1000 ; system loaded at 0x10000 (65536).
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SETUPSEG equ 0x9020 ; this is the current segment
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start:
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; ok, the read went well so we get current cursor position and save it for
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; posterity.
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mov ax,INITSEG ; this is done in bootsect already, but...
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mov ds,ax
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mov ah,0x03 ; read cursor pos
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xor bh,bh
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int 0x10 ; save it in known place, con_init fetches
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mov [0],dx ; it from 0x90000.
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; Get memory size (extended mem, kB)
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mov ah,0x88
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int 0x15
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mov [2],ax
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; Get video-card data:
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mov ah,0x0f
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int 0x10
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mov [4],bx ; bh = display page
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mov [6],ax ; al = video mode, ah = window width
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; check for EGA/VGA and some config parameters
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mov ah,0x12
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mov bl,0x10
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int 0x10
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mov [8],ax
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mov [10],bx
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mov [12],cx
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; Get hd0 data
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mov ax,0x0000
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mov ds,ax
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lds si,[4*0x41]
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mov ax,INITSEG
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mov es,ax
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mov di,0x0080
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mov cx,0x10
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rep
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movsb
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; Get hd1 data
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mov ax,0x0000
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mov ds,ax
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lds si,[4*0x46]
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mov ax,INITSEG
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mov es,ax
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mov di,0x0090
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mov cx,0x10
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rep
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movsb
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; Check that there IS a hd1 :-)
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mov ax,0x01500
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mov dl,0x81
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int 0x13
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jc no_disk1
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cmp ah,3
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je is_disk1
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no_disk1:
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mov ax,INITSEG
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mov es,ax
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mov di,0x0090
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mov cx,0x10
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mov ax,0x00
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rep
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stosb
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is_disk1:
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; now we want to move to protected mode ...
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cli ; no interrupts allowed ;
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; first we move the system to it's rightful place
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mov ax,0x0000
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cld ; 'direction'=0, movs moves forward
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do_move:
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mov es,ax ; destination segment
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add ax,0x1000
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cmp ax,0x9000
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jz end_move
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mov ds,ax ; source segment
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sub di,di
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sub si,si
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mov cx,0x8000
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rep
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movsw
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jmp do_move
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; then we load the segment descriptors
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end_move:
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mov ax,SETUPSEG ; right, forgot this at first. didn't work :-)
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mov ds,ax
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lidt [idt_48] ; load idt with 0,0
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lgdt [gdt_48] ; load gdt with whatever appropriate
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; that was painless, now we enable A20
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call empty_8042
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mov al,0xD1 ; command write
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out 0x64,al
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call empty_8042
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mov al,0xDF ; A20 on
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out 0x60,al
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call empty_8042
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; well, that went ok, I hope. Now we have to reprogram the interrupts :-(
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; we put them right after the intel-reserved hardware interrupts, at
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; int 0x20-0x2F. There they won't mess up anything. Sadly IBM really
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; messed this up with the original PC, and they haven't been able to
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; rectify it afterwards. Thus the bios puts interrupts at 0x08-0x0f,
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; which is used for the internal hardware interrupts as well. We just
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; have to reprogram the 8259's, and it isn't fun.
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mov al,0x11 ; initialization sequence
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out 0x20,al ; send it to 8259A-1
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dw 0x00eb,0x00eb ; jmp $+2, jmp $+2
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out 0xA0,al ; and to 8259A-2
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dw 0x00eb,0x00eb
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mov al,0x20 ; start of hardware int's (0x20)
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out 0x21,al
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dw 0x00eb,0x00eb
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mov al,0x28 ; start of hardware int's 2 (0x28)
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out 0xA1,al
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dw 0x00eb,0x00eb
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mov al,0x04 ; 8259-1 is master
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out 0x21,al
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dw 0x00eb,0x00eb
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mov al,0x02 ; 8259-2 is slave
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out 0xA1,al
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dw 0x00eb,0x00eb
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mov al,0x01 ; 8086 mode for both
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out 0x21,al
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dw 0x00eb,0x00eb
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out 0xA1,al
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dw 0x00eb,0x00eb
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mov al,0xFF ; mask off all interrupts for now
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out 0x21,al
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dw 0x00eb,0x00eb
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out 0xA1,al
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; well, that certainly wasn't fun :-(. Hopefully it works, and we don't
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; need no steenking BIOS anyway (except for the initial loading :-).
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; The BIOS-routine wants lots of unnecessary data, and it's less
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; "interesting" anyway. This is how REAL programmers do it.
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;
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; Well, now's the time to actually move into protected mode. To make
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; things as simple as possible, we do no register set-up or anything,
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; we let the gnu-compiled 32-bit programs do that. We just jump to
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; absolute address 0x00000, in 32-bit protected mode.
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mov ax,0x0001 ; protected mode (PE) bit
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lmsw ax ; This is it;
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jmp 8:0 ; jmp offset 0 of segment 8 (cs)
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; This routine checks that the keyboard command queue is empty
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; No timeout is used - if this hangs there is something wrong with
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; the machine, and we probably couldn't proceed anyway.
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empty_8042:
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dw 0x00eb,0x00eb
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in al,0x64 ; 8042 status port
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test al,2 ; is input buffer full?
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jnz empty_8042 ; yes - loop
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ret
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gdt:
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dw 0,0,0,0 ; dummy
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dw 0x07FF ; 8Mb - limit=2047 (2048*4096=8Mb)
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dw 0x0000 ; base address=0
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dw 0x9A00 ; code read/exec
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dw 0x00C0 ; granularity=4096, 386
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DATA_DESCRIPTOR:
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dw 0x07FF ; 8Mb - limit=2047 (2048*4096=8Mb)
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dw 0x0000 ; base address=0
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dw 0x9200 ; data read/write
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dw 0x00C0 ; granularity=4096, 386
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idt_48:
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dw 0 ; idt limit=0
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dw 0,0 ; idt base=0L
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gdt_48:
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dw 0x800 ; gdt limit=2048, 256 GDT entries
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dw 512+gdt,0x9 ; gdt base = 0X9xxxx
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