Refactor boot with polio.com first, then polmon
This commit is contained in:
6
Makefile
6
Makefile
@@ -34,6 +34,8 @@ fat12boot.bin: fat12boot.elf
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polmon.elf: LDFLAGS += -T flat1000.ld
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polmon.elf: polmon.o stdlib.o
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polio.elf: LDFLAGS += -T flat0600.ld
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polio.elf: polio.s fat12.o
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wozmon.o: polmon.cc
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wozmon.o: CPPFLAGS = -DWOZMON=1
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@@ -49,8 +51,8 @@ wozmon.bin: wozmon.elf
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polos.img: fat12boot.bin polmon.com polio.com
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dd if=/dev/zero of=$@ bs=512 count=720
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mformat -i $@ -t 40 -h 2 -s 9
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mcopy -i $@ polio.com ::/polio.com
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mcopy -i $@ polmon.com ::/polmon.com
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mcopy -i $@ polio.com ::/
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mcopy -i $@ polmon.com ::/
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dd if=fat12boot.bin of=$@ conv=notrunc
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.PHONY: clean
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20
flat1000.ld
Normal file
20
flat1000.ld
Normal file
@@ -0,0 +1,20 @@
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SECTIONS {
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. = 0x1000;
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.text : {
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KEEP(*(.init))
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*(.text*)
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}
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.rodata : {
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*(.rodata*)
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}
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.bss (NOLOAD) : {
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* (.bss)
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}
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.data : {
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*(.data)
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}
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}
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189
polio.s
Normal file
189
polio.s
Normal file
@@ -0,0 +1,189 @@
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.arch i8086,jumps
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.code16
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.intel_syntax noprefix
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.section .init
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.global _start
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_start:
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jmp main
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diskpointer = 0x1e*4
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dbtbase = 0x0500
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.section .text.dosdbt
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.local dosdbt
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dosdbt: # assumes es=0
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push si
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push di
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push ds
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mov si, diskpointer
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lds si, [si]
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mov di, dbtbase
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mov cx, 0x0a # size of the dbt
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cld
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rep movsb # move dbt to dbtbase
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pop ds
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mov al, 9 # sectors per track
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mov si, dbtbase
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mov [si+4], al # set number of sectors
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mov di, diskpointer
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mov [di], si # new int1eh offset
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mov [di+2], ds # and segment
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pop di
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pop si
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ret
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.section .text.int80stuff
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# near copy [param 2] bytes, es:[param 0] -> es:[param 1]
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copy:
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mov si, [bp+0] # source
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mov di, [bp+2] # destination
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mov cx, [bp+4] # length
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cld
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rep movsb
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ret
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## floppy stuff
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# same as read but with a different int13h:ah value
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writesector:
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mov ax, 0x0301 # write command, 1 sector
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jmp 0f
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# params: addr, c, h, s
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# return status in ah, sectors read (1 or 0) in al
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readsector:
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mov ax, 0x0201 # read command, 1 sector
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0:
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mov bx, [bp+0] # addr
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mov ch, [bp+2] # c
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mov dh, [bp+4] # h
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mov cl, [bp+6] # s
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int 0x13
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ret
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# params: c, h
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# returns: status in ah, 0 in al?
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buffer = 0xe000 # buffer needs to be big enough for a whole track
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# (for some reason), so 9 * 512 bytes = 0x1200 bytes
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sectors = 9
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formattrack:
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mov bx, buffer
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xor cx, cx
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0:
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cmp cl, sectors
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jnl 1f
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mov di, cx
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and di, 0x0f # max 15 sectors
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shl di, 1
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shl di, 1 # di = cl*4
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lea di, [bx+di]
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mov al, [bp+0] # track number
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mov [di+0], al
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mov al, [bp+2] # head number
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mov [di+1], al
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mov al, cl # sector number
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inc al
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mov [di+2], al
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movb [di+3], 0x02 # 512 bytes per sector
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inc cl
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jmp 0b
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1:
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mov ah, 0x05 # format track
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mov al, sectors
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mov dl, 0 # first drive
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mov ch, [bp+0] # track number
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mov dh, [bp+2] # head number
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mov cl, 1 # sector number (first sector?)
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int 0x13
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ret
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readfile:
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mov ax, [bp+0]
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mov dx, [bp+2]
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call fat12_readfile
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ret
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.section .rodata.polmon_str
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polmon_str: .ascii "POLMON COM"
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polmon_addr = 0x1000
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.section .text.main
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.global main
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main:
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cli
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mov ax, 0x2000 # stack address
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mov sp, ax # ss should already be 0
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sti
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call dosdbt
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mov ax, 0x1a00 # first sector of first fat
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mov dx, 0x1c00 # first sector of root dir
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call fat12_init
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mov si, 0x80*4
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movw [si], offset int80h
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movw [si+2], 0
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mov ax, offset polmon_str
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mov dx, polmon_addr
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call fat12_readfile
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test ax, ax
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jnz 0f
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jmp polmon_addr
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0:
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mov ax, 0x0e42
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mov bh, 0
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int 0x10
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cli
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hlt
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.section .text.int80h
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int80h:
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push bx
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push si
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push di
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push bp
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push ds
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push es
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xor cx, cx
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mov es, cx
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mov ds, cx
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shl ah
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cmp ah, offset int80h_entries
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jge 0f
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mov al, ah
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xor ah, ah
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mov si, ax
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mov bp, sp
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lea bp, [bp + 18] # 12 for us, 6 for the interrupt
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call [int80h_table+si]
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jmp 1f
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0:
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mov ax, -1
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1:
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pop es
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pop ds
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pop bp
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pop di
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pop si
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pop bx
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iret
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.section .rodata.int80h
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int80h_table:
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.word offset copy # 0x00
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.word offset readsector # 0x01
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.word offset writesector # 0x02
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.word offset formattrack # 0x03
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.word offset readfile # 0x04
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int80h_entries = . - int80h_table
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