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Boot loader appears to work somewhat, kernel is questionable

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This commit is contained in:
Andrew Kesterson
2015-01-23 23:02:25 -08:00
parent 6034fe2573
commit 20ee203ace
5 changed files with 188 additions and 24 deletions
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21
Makefile
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@@ -1,14 +1,23 @@
all: boot.img
all: boot.img kernel.bin
boot.bin: bootloader.S
nasm $< -f bin -o $@
boot.bin: asm/bootloader.S asm/bootloader.S
nasm asm/bootloader.S -f bin -o $@
boot.img: boot.bin
dd if=$< bs=512 of=$@
asm/%.o: asm/%.S
nasm $< -f as86 -o $@
src/%.o: src/%.c
bcc -ansi -3 -c -o $@ $<
kernel.bin: src/kernel.o
ld86 -T0x1000 -o $@ $^
boot.img: boot.bin kernel.bin
cat $^ > $@
test: boot.img
bochs -f bochsrc -q
.PHONY: clean
clean:
rm -f boot.bin
rm -f boot.bin asm/*o src/*o

70
asm/bootloader.S Normal file
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@@ -0,0 +1,70 @@
[bits 16] ; 16 bit real mode code
[org 0x7C00] ; Origin at 0x7C00 (upper end of memory)
start:
call blankScreen
mov dx, 0x0
call setCursorPosition
mov si, _str_hello ; si = source index
call printString
mov dh, 0x1
mov dl, 0x0
call setCursorPosition
mov al, 0x17 ; read the remaining 16 tracks
mov ch, 0x1 ; .... on track 1 ....
mov cl, 0x1 ; .... starting at sector 1
mov bx, 0x1000 ; 0x1000 is a standard kernel start location
mov es, bx
xor bx, bx ; bx = 0, es:bs = 0x1000:0
call loadFloppyDiskSectors
push ax
mov ax, bx
add ax, 0x2200 ; we just read 0x2200 bytes, move pointer in memory
mov bx, ax
pop ax
mov al, 0x17 ; read 18 sectors per track for all future tracks
mov cl, 0x1 ; start at sector 1 for all future tracks
mov di, 0x2FF ; abuse di as a counter, while (di < 80)
; di is technically a destination index for stream
; ops, but nothing is using it ATM, so gimme.
_next_floppy_track:
push ax
mov ax, 0x2e
call printCharacter
mov ax, cx
mov cx, di
mov cl, al
pop ax
call loadFloppyDiskSectors
push ax
mov ax, bx
add ax, 0x2400 ; each floppy track is (512b*18s)=0x2400 bytes long
mov bx, ax
pop ax
inc di
push cx
mov cx, 0x50
cmp di, cx ; di < 80 ?
jg _end_floppy_read
pop cx
_end_floppy_read:
mov dh, 0x1
mov dl, 0x0
call setCursorPosition
mov si, _str_floppydone
call printString
jmp 0x1000
%include "libinterrupt.S"
_str_hello db 'Piquant v0.1 Bootloader', 0xA, 0
_str_loading db 'Loading', 0
_str_floppydone db 'Kernel loaded', 0xA, 0
times 510 - ($ - $$) db 0 ; fill up to 510 bytes with 0
dw 0xAA55 ; magic bootloader signature

26
asm/libinterrupt.S Normal file
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@@ -0,0 +1,26 @@
resetFloppy:
mov ax, 0 ; reset floppy disk (only need ah, reset
; al while we're here though)
mov dl, 0 ; use drive 0 (first floppy)
int 0x13
jc resetFloppy
ret
loadDiskSector:
printCharacter: ; print a single character to the display
mov ah, 0x0e ; int 0x10 is the entire display control,
; 0x0e means teletype output
mov bh, 0x00 ; Print on the zero (primary) page
mov bl, 0x07 ; Color. 0x07 is grey on black.
int 0x10
ret
printString: ; print the entire string pointed to by si
mov al, [si] ; [x] == *x, dereferencing source index
call printCharacter
inc si
cmp al, 0x0 ; found the trailing NULL?
jne printString
ret

58
bootloader.S
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@@ -1,28 +1,52 @@
[bits 16] ; 16 bit real mode code
[org 0x7C00] ; Origin at 0x7C00 (upper end of memory)
start:
mov si, _str_hello ; si = source index
call printString
jmp $ ; hang forever
printCharacter: ; print a single character to the display
mov ah, 0x0e ; int 0x10 is the entire display control,
; 0x0e means teletype output
mov bh, 0x00 ; Print on the zero (primary) page
mov bl, 0x07 ; Color. 0x07 is grey on black.
int 0x10
ret
printString: ; print the entire string pointed to by si
mov al, [si] ; [x] == *x, dereferencing source index
mov al, 0x97
call printCharacter
inc si
cmp al, 0x0 ; found the trailing NULL?
jne printString
ret
; mov al, 0x17 ; read the remaining 16 tracks
; mov ch, 0x1 ; .... on track 1 ....
; mov cl, 0x2 ; .... starting at sector 2
; mov bx, 0x1000 ; 0x1000 is a standard kernel start location
; mov es, bx
; xor bx ; bx = 0, es:bs = 0x1000:0
; call loadFloppyDiskSectors
; push ax
; mov ax, bx
; add ax, 0x2200 ; we just read 0x2200 bytes, move pointer in memory
; mov bx, ax
; pop ax
; mov al, 0x17 ; read 18 sectors per track for all future tracks
; mov cl, 0x1 ; start at sector 1 for all future tracks
_str_hello db 'Piquant v0.1 Bootloader', 0 ; String + trailing NULL
; mov di, 0x2 ; abuse di as a counter, while (di < 80)
; ; di is technically a destination index for stream
; ; ops, but nothing is using it ATM, so gimme.
; _next_floppy_track:
; mov ch, di
; call loadFloppyDiskSectors
; push ax
; mov ax, bx
; add ax, 0x2400 ; each floppy track is (512b*18s)=0x2400 bytes long
; mov bx, ax
; pop ax
; inc di
; push cx
; mov cx, 0x50
; cmp di, cx ; di < 80 ?
; jlt _next_floppy_track
mov si, _str_floppydone
call printString
jmp $
%include "libinterrupt.S"
_str_hello db 'Piquant v0.1 Bootloader', 0xA, 0
_str_floppydone db 'Kernel loaded', 0xA, 0
times 510 - ($ - $$) db 0 ; fill up to 510 bytes with 0
dw 0xAA55 ; magic bootloader signature

35
src/kernel.c Normal file
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void printChar(char c)
{
#asm
#if !__FIRST_ARG_IN_AX__
mov bx, sp
#endif
#if __FIRST_ARG_IN_AX__
mov si, ax
#else
mov si, [bx+2]
#endif
mov ah, 0x0e
mov bh, 0x00
mov bl, 0x07
int 0x10
#endasm
return;
}
void printString(char *ptr)
{
while (*ptr != '\0') {
printChar(*ptr);
*ptr++;
}
return;
}
void main(void)
{
char *kernelHello = "Welcome to Piquant, please wait while Kernel boots...\n";
printString(kernelHello);
while(1);
}