Kernel now is loaded from a partition, allowing a separate MBR bootloader if desired
This commit is contained in:
Lucia Ceionia
parent
e9c4e993f4
commit
1b2184fe52
24
Makefile
24
Makefile
@ -7,16 +7,29 @@ LFLAGS = -Wl,--gc-sections -Wl,--print-gc-sections -m32 -nostartfiles -nostdlib
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ifeq ($(OUTFILE),)
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OUTFILE = virtdisk.bin
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endif
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ifeq ($(PARTSTART),)
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PARTSTART = 2048
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endif
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PARTVBR=$(shell echo "$(PARTSTART) * (2^9)" | bc)
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PARTVBRBOOT=$(shell echo "$(PARTVBR) + 90" | bc)
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KERNSEC=$(shell echo "$(PARTSTART) + 4" | bc)
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.PHONY: $(OUTFILE)
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all: $(OUTFILE)
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$(OUTFILE): boot.bin kernel.bin
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# Copy to boot sector, don't overwrite MBR
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$(OUTFILE): boot.bin boot_partition.bin kernel.bin
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# Copy system bootloader to boot sector, don't overwrite MBR
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dd bs=400 count=1 conv=notrunc if=boot.bin of=$@
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# Write kernel beyond boot sector, maximum 128K (256 sectors)
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dd bs=512 count=256 seek=1 conv=notrunc if=kernel.bin of=$@
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# Ensure partition VBR contains EB 5A
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echo -n -e '\xeb\x5a' | dd bs=1 seek=$(PARTVBR) count=2 conv=notrunc of=$@
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# Copy kernel bootloader to partition VBR
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dd bs=1 count=420 seek=$(PARTVBRBOOT) conv=notrunc if=boot_partition.bin of=$@
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# TODO Check that disk has enough reserved sectors,
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# currently this will overwrite the disk if too few
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# Write kernel beyond boot sector, maximum 64K (128 sectors)
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dd bs=512 count=128 seek=$(KERNSEC) conv=notrunc if=kernel.bin of=$@
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kernel.bin: out.o link.ld usermode.o
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clang $(LFLAGS) -Wl,-M -Tlink.ld -ffreestanding -o $@ out.o usermode.o
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@ -37,8 +50,7 @@ out.o: $(objects)
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clang $(CFLAGS) -ffunction-sections -fdata-sections -Os -o $@ $<
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virtdisk:
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dd bs=1M count=32 if=/dev/zero of=virtdisk.bin
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echo -n -e '\x55\xaa' | dd bs=1 seek=510 conv=notrunc of=virtdisk.bin
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cp virtdisk.bin.ex virtdisk.bin
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clean:
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rm -f $(objects) out.o kernel.bin boot.bin usermode.bin
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219
boot.nasm
219
boot.nasm
@ -1,6 +1,8 @@
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secreadcnt equ 0x38
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kernelreads equ 0x10000/(512*secreadcnt) ; 64K / Sector Size FIXME This underestimates when kernel size is not divisible by bytes per read
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[ORG 0x7c00]
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; This boots the active partition.
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; Relocates self to 0x7E00, loads the
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; first sector of active partition
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; to 0x7C00 and jumps
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[ORG 0x7C00]
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[BITS 16]
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xor ax, ax
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mov ds, ax
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@ -8,68 +10,50 @@ mov es, ax
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mov ax, 0x8000
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mov ss, ax
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mov sp, 0xFF00
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; Relocate self
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mov di, 0x7E00
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mov si, 0x7C00
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mov cx, 512
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rep movsw
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jmp 0:relocated
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; TODO Make this calculated, somehow
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[SECTION RELOC vstart=0x7E20]
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relocated:
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mov ah, 0x41 ; int 13 extensions check
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mov bx, 0x55AA
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int 0x13
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jc no_exten
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mov cx, kernelreads
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read_loop:
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jc no_int13
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; Find active partition
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xor cx, cx
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mov si, 0x7E00+0x1BE
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.find_active:
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lodsb
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bt ax, 7
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jc read
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add si, 15
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inc cl
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cmp cl, 4
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jl .find_active
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jmp err
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read:
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; Put partition start LBA in disk address packet
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add si, 7
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mov di, addr_packet_start_block
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movsw
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movsw
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; Load the first sector of the partition
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xor ax, ax
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mov ah, 0x42
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mov si, addr_packet
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int 0x13
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jc err
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add word [addr_packet_transfer_buff_seg], (secreadcnt*512)/16
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add word [addr_packet_start_block], secreadcnt
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loop read_loop
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entry:
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;mov ax,0x2403 ; A20 BIOS Support
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;int 0x15
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;jb .no_a20
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;cmp ah,0
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;jnz .no_a20
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;mov ax,0x2401 ; A20 BIOS Activate
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;int 0x15
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;.no_a20:
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cli ; no interrupts
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xor ax,ax
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mov ds, ax
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lgdt [gdt_desc] ; load gdt register
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mov eax, cr0 ; set pmode bit
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or al, 1
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mov cr0, eax
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jmp 08h:Pmode
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no_exten:
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; read with CHS
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; FIXME This only reads up to sector count
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mov ah,8
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int 0x13 ; geometry
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and cx, 0x3f
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push cx
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push 0x0080 ; DH=head,DL=disk
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push 0x2000 ; buffer seg
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push 2 ; sector
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.loop:
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mov ax, [esp]
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push 0xb800
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pop es
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xor di,di
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call hexprint
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mov ax, [esp+2]
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mov es, ax
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mov ax, 0x0201
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mov cx, [esp]
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xor bx,bx
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mov dx, [esp+4]
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int 0x13
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jc err
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add word [esp+2], 0x20
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mov cx, [esp]
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inc cl
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mov [esp], cx
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cmp cl, [esp+6]
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jg entry
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jmp .loop
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; Jump to partition boot
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jmp 0:0x7C00
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no_int13:
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mov si, no_exten_str
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mov cx, no_exten_str_end - no_exten_str
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jmp print
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err:
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mov bx, ax
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mov si, string
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@ -83,126 +67,17 @@ err_print:
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lodsb
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stosw
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loop err_print
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;add di, 2
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;mov ax, bx
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;call hexprint
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hlt_loop:
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hlt
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jmp hlt_loop
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hexprint:
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xor cx, cx
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mov bl, al
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shr al, 4
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jmp .donibble
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.nibble2:
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mov al, bl
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inc cx
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.donibble:
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and al, 0x0F
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cmp al, 0x0A
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jl .noadjust
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add al, 'A' - '0' - 10
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.noadjust:
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add al, '0'
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mov ah, 0x7
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stosw
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test cx, cx
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jz .nibble2
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ret
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[BITS 32]
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Pmode:
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mov eax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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; check A20
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.a20:
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mov edi, 0x107C00
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mov esi, 0x007C00
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mov [esi], esi
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mov [edi], edi
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cmpsd
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jne .kernel
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call enable_A20
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;in al, 0x92 ; fast A20
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;test al, 2
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;jnz .fa20_end
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;or al, 2
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;and al, 0xFE
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;out 0x92, al
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;.fa20_end:
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jmp .a20
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.kernel:
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;mov dword [0xb8000], 0x07000700 | 'P' | 'M' << 16
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;mov dword [0xb8004], 0x07000700 | 'O' | 'D' << 16
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;mov dword [0xb8008], 0x07000700 | 'E' | ' ' << 16
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mov esi, 0x20000
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mov edi, 0x100000
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mov ecx, 0x10000
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rep movsb
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jmp 08h:0x100000
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enable_A20:
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cli
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call a20wait
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mov al,0xAD
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out 0x64,al
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call a20wait
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mov al,0xD0
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out 0x64,al
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call a20wait2
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in al,0x60
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push eax
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call a20wait
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mov al,0xD1
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out 0x64,al
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call a20wait
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pop eax
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or al,2
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out 0x60,al
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call a20wait
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mov al,0xAE
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out 0x64,al
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call a20wait
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ret
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a20wait:
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in al,0x64
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test al,2
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jnz a20wait
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ret
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a20wait2:
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in al,0x64
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test al,1
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jz a20wait2
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ret
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gdt_desc:
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dw gdt_end - gdt
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dd gdt
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gdt:
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gdt_null: dq 0
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gdt_code: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
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db 0 ; bits 16-23 base address
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db 10011010b ; access byte
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db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
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db 0 ; bits 24-31 base address
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gdt_data: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
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db 0 ; bits 16-23 base address
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db 10010010b ; access byte
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db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
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db 0 ; bits 24-31 base address
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gdt_end:
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string: db 'DISK ERROR'
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string_end:
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;no_exten_str: db 'NO INT13 EXTEN'
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;no_exten_str_end:
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no_exten_str: db 'NO INT13 EXTEN'
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no_exten_str_end:
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addr_packet:
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db 0x10, 0x00 ; size, reserved
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dw secreadcnt ; blocks
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addr_packet_transfer_buff_off: dw 0x0000 ; transfer buffer offset
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addr_packet_transfer_buff_seg: dw 0x2000 ; transfer buffer segment
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addr_packet_start_block: dq 1 ; start block
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dw 1 ; blocks
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addr_packet_transfer_buff_off: dw 0x7C00 ; transfer buffer offset
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addr_packet_transfer_buff_seg: dw 0x0000 ; transfer buffer segment
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addr_packet_start_block: dq 0 ; start block
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136
boot_partition.nasm
Normal file
136
boot_partition.nasm
Normal file
@ -0,0 +1,136 @@
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; This boots *from a FAT partition*
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; So it starts at 0x7C00+90, the offset of
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; the boot code in a FAT VBR
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secreadcnt equ 0x38
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kernelreads equ 0x10000/(512*secreadcnt) ; 64K / Sector Size FIXME This underestimates when kernel size is not divisible by bytes per read
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[ORG 0x7c00+90]
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[BITS 16]
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xor ax, ax
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mov ds, ax
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mov es, ax
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mov ax, 0x8000
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mov ss, ax
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mov sp, 0xFF00
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; FIXME Assumes INT 13 Extension support
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mov ah, 0x42
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mov si, addr_packet
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int 0x13
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jc err
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xor cx, cx
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mov si, 0x7E00+0x1BE
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.find_active:
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lodsb
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bt ax, 7
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jc read
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add si, 15
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inc cl
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cmp cl, 4
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jl .find_active
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jmp err
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read:
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mov dh, cl ; Store active partition
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add si, 7
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mov di, addr_packet_start_block
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lodsw
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; Offset of kernel in partition
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add ax, 4
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stosw
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lodsw
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adc ax, 0
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stosw
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mov cx, kernelreads
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read_loop:
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xor ax, ax
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mov ah, 0x42
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mov si, addr_packet
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int 0x13
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jc err
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add word [addr_packet_transfer_buff_seg], (secreadcnt*512)/16
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add word [addr_packet_start_block], secreadcnt
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loop read_loop
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entry:
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cli ; no interrupts
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xor ax,ax
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mov ds, ax
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lgdt [gdt_desc] ; load gdt register
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mov eax, cr0 ; set pmode bit
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or al, 1
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mov cr0, eax
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jmp 08h:Pmode
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err:
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mov si, string
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mov cx, string_end - string
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print:
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push 0xb800
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pop es
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xor di, di
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mov ah, 0x7
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err_print:
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lodsb
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stosw
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loop err_print
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hlt_loop:
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hlt
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jmp hlt_loop
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[BITS 32]
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Pmode:
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mov eax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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; check A20
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.a20:
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mov edi, 0x107C00
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mov esi, 0x007C00
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mov [esi], esi
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mov [edi], edi
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cmpsd
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jne .kernel
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; FIXME It's annoying that fast A20
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; will crash old systems, but it's
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; just so small...
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in al, 0x92 ; fast A20
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test al, 2
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jnz .fa20_end
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or al, 2
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and al, 0xFE
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out 0x92, al
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.fa20_end:
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jmp .a20
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.kernel:
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mov esi, 0x7E00
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mov edi, 0x100000
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mov ecx, 0x10000
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rep movsb
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xchg bx,bx
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jmp 08h:0x100000
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gdt_desc:
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dw gdt_end - gdt
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dd gdt
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gdt:
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gdt_null: dq 0
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gdt_code: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
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db 0 ; bits 16-23 base address
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db 10011010b ; access byte
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db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
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db 0 ; bits 24-31 base address
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gdt_data: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
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db 0 ; bits 16-23 base address
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db 10010010b ; access byte
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db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
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db 0 ; bits 24-31 base address
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gdt_end:
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string: db 'DISK ERROR'
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string_end:
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addr_packet:
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db 0x10, 0x00 ; size, reserved
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dw secreadcnt ; blocks
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addr_packet_transfer_buff_off: dw 0x7E00 ; transfer buffer offset
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addr_packet_transfer_buff_seg: dw 0x0000 ; transfer buffer segment
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addr_packet_start_block: dq 0 ; start block
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4
helper.c
4
helper.c
@ -48,11 +48,13 @@ void SetCursorDisabled() {
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V8086Int(0x10, ®s);
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}
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// This should DEFINITELY be an argument
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uint8_t SystemPartition = 0;
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uint32_t OpenVol(VOLINFO *vi) {
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uint8_t *diskReadBuf = (uint8_t *)0x20000;
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uint8_t pactive, ptype;
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uint32_t pstart, psize;
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pstart = DFS_GetPtnStart(0, diskReadBuf, 0, &pactive, &ptype, &psize);
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pstart = DFS_GetPtnStart(0, diskReadBuf, SystemPartition, &pactive, &ptype, &psize);
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if (pstart == -1) return -1;
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return DFS_GetVolInfo(0, diskReadBuf, pstart, vi);
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}
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27
kernel.c
27
kernel.c
@ -101,6 +101,14 @@ void ensure_v86env() {
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*d++ = *s++;
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}
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uint32_t _ERRORCODE = 0;
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__attribute__((__no_caller_saved_registers__))
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uint32_t check_error_code() {
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uint32_t v = _ERRORCODE;
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_ERRORCODE = 0;
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return v;
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}
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__attribute__((__no_caller_saved_registers__))
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__attribute__((__noreturn__))
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extern void return_prev_task();
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@ -145,6 +153,7 @@ void error_environment(uint32_t stack0, uint32_t stack1, uint32_t stack2, uint32
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// reset error screen
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for (int i = 0; i < (80*50)/2; i++)
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((uint32_t*)error_screen)[i] = 0x0f000f00;
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_ERRORCODE = -1;
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return_prev_task();
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}
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@ -181,6 +190,10 @@ Protected Only (1MB+)
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400000 - 700000 Usermode Code (3mB)
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700000 - 800000 Usermode Stack (1mB)
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*/
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// FIXME Truly awful
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extern uint8_t SystemPartition;
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void DrawScreen(uint16_t *vga) {
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uint16_t *vga_text = vga;
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// clear screen
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@ -214,6 +227,7 @@ void DrawScreen(uint16_t *vga) {
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vga_text[80+42] = 0x1f00 | 'S';
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vga_text[80+43] = 0x1f00 | ' ';
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vga_text[80+44] = 0x1f00 | '-';
|
||||
printByte(SystemPartition, &vga_text[80+50]);
|
||||
}
|
||||
|
||||
void SetPalette() {
|
||||
@ -418,7 +432,9 @@ void SystemRun() {
|
||||
{
|
||||
VOLINFO vi;
|
||||
// TODO Check partitions beyond 0
|
||||
while (OpenVol(&vi)) {
|
||||
while (1) {
|
||||
create_child(GetFreeStack(), (uintptr_t)OpenVol, 1, &vi);
|
||||
if (!check_error_code()) break;
|
||||
vga_text = &((word*)0xb8000)[80*4 + 2];
|
||||
vga_text += printStr("Error loading file select. Ensure the disk has a valid MBR and FAT partition.", vga_text);
|
||||
vga_text = &((word*)0xb8000)[80*5 + 2];
|
||||
@ -457,8 +473,8 @@ void start() {
|
||||
vga_text = &vga_text[80];
|
||||
|
||||
// DL *should* be preserved
|
||||
uint8_t dl;
|
||||
asm volatile("nop":"=d"(dl));
|
||||
uint16_t boot_dx;
|
||||
asm volatile("nop":"=d"(boot_dx));
|
||||
|
||||
if (!check_cmov()) {
|
||||
char cmov_err[] = "NO CMOV";
|
||||
@ -467,7 +483,7 @@ void start() {
|
||||
for (;;) asm volatile("hlt");
|
||||
}
|
||||
|
||||
vga_text += printByte(dl, vga_text);
|
||||
vga_text += printWord(boot_dx, vga_text);
|
||||
vga_text++;
|
||||
|
||||
uint32_t o;
|
||||
@ -509,6 +525,9 @@ void start() {
|
||||
backup_ivtbios();
|
||||
InitDisk();
|
||||
|
||||
// DL contained disk number, DH contained active partition
|
||||
SystemPartition = boot_dx >> 8;
|
||||
|
||||
create_child(GetFreeStack(), (uintptr_t)SystemRun, 0);
|
||||
// If this returns, something is *very* wrong, reboot the system
|
||||
// TODO Maybe try to recover?
|
||||
|
||||
6
tests.c
6
tests.c
@ -122,6 +122,10 @@ void TestCHS() {
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// FIXME Just horrible
|
||||
extern uint8_t SystemPartition;
|
||||
|
||||
void TestFAT() {
|
||||
uint16_t *vga_text = (uint16_t *)0xb8000;
|
||||
uint8_t *diskReadBuf = (uint8_t *)0x22400;
|
||||
@ -131,7 +135,7 @@ void TestFAT() {
|
||||
|
||||
uint8_t pactive, ptype;
|
||||
uint32_t pstart, psize;
|
||||
pstart = DFS_GetPtnStart(0, diskReadBuf, 0, &pactive, &ptype, &psize);
|
||||
pstart = DFS_GetPtnStart(0, diskReadBuf, SystemPartition, &pactive, &ptype, &psize);
|
||||
vga_text = (uint16_t *)0xb8000;
|
||||
vga_text += printStr("PartStart: ", vga_text);
|
||||
vga_text += printDword(pstart, vga_text);
|
||||
|
||||
BIN
virtdisk.bin.ex
BIN
virtdisk.bin.ex
Binary file not shown.
Loading…
Reference in New Issue
Block a user