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Loading from disk works, but jumping to the kernel does not

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This commit is contained in:
Andrew Kesterson
2015-01-24 18:06:35 -08:00
parent 20ee203ace
commit 5e4513dd22
6 changed files with 112 additions and 121 deletions
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19
Makefile
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@@ -1,16 +1,21 @@
all: boot.img kernel.bin
boot.bin: asm/bootloader.S asm/bootloader.S
nasm asm/bootloader.S -f bin -o $@
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 $@ $^
ld86 -T0x1000 -M -o $@ $^
asm/kernel_syms.S: kernel.bin
objdump86 kernel.bin | \
grep -E "^[0-9]+ T _.*" | \
python -c "import sys; print '\n'.join([\"_extern_c%s:\n jmp 0x1000:0x%04x\" % (x.split(' ')[2].strip('\n'), int(x.split(' ')[0].lstrip('0'), 16)-0x1000) for x in sys.stdin.readlines()])" > asm/kernel_syms.S
boot.bin: asm/kernel_syms.S asm/bootloader.S asm/bootloader.S
cd asm && nasm bootloader.S -f bin -o ../$@
asm/%.o: asm/%.S
nasm $< -f as86 -o $@
boot.img: boot.bin kernel.bin
cat $^ > $@

74
asm/bootloader.S
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@@ -13,44 +13,44 @@ start:
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 al, 0x1 ; read the remaining 16 tracks
mov ch, 0x0 ; .... on track 0 ....
mov cl, 0x2 ; .... starting at sector 2
mov bx, 0x1000 ; 0x1000 is a standard kernel start location
mov es, bx
xor bx, bx ; bx = 0, es:bs = 0x1000:0
mov bx, 0x0 ; bx = 0, es:bx = 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
;; 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
;; 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
@@ -58,13 +58,15 @@ _end_floppy_read:
call setCursorPosition
mov si, _str_floppydone
call printString
jmp 0x1000
jmp _extern_c_main
%include "libinterrupt.S"
%include "kernel_syms.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

4
asm/kernel_syms.S Normal file
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@@ -0,0 +1,4 @@
_extern_c_main:
jmp 0x1000:0x0049
_extern_c_printCh:
jmp 0x1000:0x0000

75
asm/libinterrupt.S
View File

@@ -1,26 +1,59 @@
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
mov ah, 0 ; reset floppy disk
mov dl, 0 ; use drive 0 (first floppy)
int 0x13
jc resetFloppy
ret
loadDiskSector:
;; set al = how many sectors to read
;; set ch = what track to read from
;; set cl = what sector on the track to start reading
;; set es:bx = where to store the disk data
loadFloppyDiskSectors:
mov ah, 0x02 ; int 0x13 function 2 (read sectors from disk)
mov dh, 0 ; head 0 (assume simple small floppy)
mov dl, 0 ; drive 0 = floppy drive
int 0x13
jc loadFloppyDiskSectors ; retry on errors (not much else we can do)
blankScreen:
push cx
mov cx, 0x0
_blankScreen_next:
mov al, 0x20 ; blank space
call printCharacter
inc cx
cmp cx, 0x7d0 ; 80 * 25 screen = 0x7d0
jne _blankScreen_next
_blankScreen_exit:
pop cx
ret
;; set dh = row
;; set dl = column
setCursorPosition:
mov ah, 0x02
mov bh, 0
int 0x10
ret
;; set al = character to display
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
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
;; set si = string to display
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
_printString_next:
mov al, [si] ; [x] == *x, dereferencing source index
cmp al, 0x0 ; found the trailing NULL?
je _printString_exit
call printCharacter
inc si
jmp _printString_next
_printString_exit:
ret

52
bootloader.S
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@@ -1,52 +0,0 @@
[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
mov al, 0x97
call printCharacter
; 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
; 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

9
src/kernel.c
View File

@@ -19,9 +19,9 @@ void printChar(char c)
void printString(char *ptr)
{
while (*ptr != '\0') {
printChar(*ptr);
*ptr++;
while ((char)*ptr != '\0') {
printChar((char)*ptr);
ptr++;
}
return;
@@ -29,7 +29,6 @@ void printString(char *ptr)
void main(void)
{
char *kernelHello = "Welcome to Piquant, please wait while Kernel boots...\n";
printString(kernelHello);
//printString("Piquant Kernel v0.1\n");
while(1);
}