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more of bootloader, tiny kernel stub

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This commit is contained in:
Benji Dial 2019-12-14 18:31:34 -05:00
parent aeff38fe15
commit cdc7b2ae53
7 changed files with 313 additions and 51 deletions
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2
.gitignore vendored Normal file
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@ -0,0 +1,2 @@
obj/
out/

4
doc/design/memory_map.txt
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@ -1,7 +1,9 @@
0x0000 - 0x03ff : interrupt vector table
0x0400 - 0x04ff : bios data area
0x0500 - 0x05ff : structure pointers
0x00 dword : fat pointer
0x00 : fat
0x04 : root directory
0x08 : kernel
0x0600 - 0x1fff : not assigned
0x2000 - 0x3fff : memory map
for each word : 1 page

17
makefile
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@ -1,10 +1,23 @@
floppy: out bootloader
mkfs.fat -C -f 1 -F 12 -n "PORTLAND OS" -R 2 -S 512 out/floppy.img 1440
floppy: out bootloader files
mkfs.fat -C -f 1 -F 12 -n "PORTLAND OS" -R 4 -S 512 out/floppy.img 1440
mkdir out/floppy_mount
mount out/floppy.img out/floppy_mount
cp out/fs/* out/floppy_mount/
umount out/floppy_mount
dd if=obj/bootloader.bin of=out/floppy.img bs=1 seek=62 conv=notrunc
bootloader: obj
nasm src/bootloader.bin -o obj/bootloader.bin
kernel: obj out
gcc -c src/kernel/main.c -o obj/kmain.o -ffreestanding
gcc -c src/kernel/vga.c -o obj/kvga.o -ffreestanding
ld obj/kmain.o obj/kvga.o -o out/kernel.out -nostdlib --oformat=i386-aout
files: kernel
mkdir out/fs
cp out/kernel.out out/fs/kernel.sys
obj:
mkdir -p obj

213
src/bootloader.asm
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@ -17,20 +17,22 @@
pointers:
.fat equ 0x0500
.root_dir equ 0x0504
.kernel equ 0x0508
fat_header:
.oem_name equ 0x7c03;mkfs.fat - ignored
.bytes_per_sector equ 0x7c0b;0x0200 - assumed
.sectors_per_cluster equ 0x7c0d;0x01 - assumed
.reserved_sectors equ 0x7c0e;0x0002 - other values handled
.reserved_sectors equ 0x7c0e;0x0004 - other values handled
.n_fats equ 0x7c10;0x01 - assumed
.directory_entries equ 0x7c11; -
.root_dir_entries equ 0x7c11; -
.n_sectors equ 0x7c13;0x0b40 -
.media_type equ 0x7c15; -
.sectors_per_fat equ 0x7c16; - handled
.sectors_per_track equ 0x7c18;0x0012 -
.sides equ 0x7c1a;0x0002 -
.hidden_sectors equ 0x7c1c;0x0000_0000 - assumed
.hidden_sectors equ 0x7c1c;0x0000_0000 - assumed, top half used as scratch for sector number of cluster 0
.long_sectors equ 0x7c20;0x0000_0000 - assumed
.drive_number equ 0x7c24; - ignored, used as scratch
.flags equ 0x7c25; - ignored
@ -148,13 +150,165 @@ memory:
jne halt
mov ax, word [fat_header.sectors_per_fat]
xor ecx, ecx
mov cx, word [fat_header.reserved_sectors]
call allocate_and_load
mov dword [pointers.fat], ebx
mov ax, word [fat_header.root_dir_entries]
dec ax
shr ax, 4
inc ax
xor ecx, ecx
mov cx, word [fat_header.reserved_sectors]
add cx, word [fat_header.sectors_per_fat]
jnc .no_carry
or ecx, 0x0001_0000
.no_carry:
call allocate_and_load
mov dword [pointers.root_dir], ebx
xor edx, edx
mov dx, word [fat_header.root_dir_entries]
shl edx, 5
add edx, ebx
find_kernel:
mov eax, 0x6e_72_65_6b;kern
mov ecx, 0x20_20_6c_65;el
mov ebx, dword [pointers.root_dir]
.loop:
test dword [ebx], eax
jne .next
test dword [ebx + 4], ecx
jne .next
test word [ebx + 8], 0x79_73;sy
jne .next
test byte [ebx + 10], 0x73;s
je .found
.next:
add ebx, 32
test ebx, edx
jne .loop
jmp halt
.found:
mov byte [allocate_and_load.load], 0xc3;ret
mov eax, dword [ebx + 0x1c]
dec eax
shr eax, 9
inc eax
test eax, 0xffff_0000
jnz halt
push word [ebx + 0x1a]
call allocate_and_load
mov dword [pointers.kernel], ebx
mov ax, word [fat_header.root_dir_entries]
dec ax
shr ax, 4
dec ax
add ax, word [fat_header.reserved_sectors]
jc halt
add ax, word [fat_header.sectors_per_fat]
jc halt
mov word [fat_header.hidden_sectors + 2], ax
load_kernel:
mov word [dap.length], 0x0001
mov word [dap.offset], bx
xor bx, bx
shr ebx, 4
test ebx, 0xffff_0000
jnz halt
mov word [dap.segment], bx
xor edx, edx
pop dx
mov word [dap.start + 2], 0x0000
mov ah, 0x42
mov si, dap
.loop:
mov cx, dx
add cx, word [fat_header.hidden_sectors + 2]
jc halt
mov word [dap.start], cx
int 0x13
mov ebx, dword [pointers.fat]
add ebx, edx
add ebx, edx
add ebx, edx
xor edx, edx
mov dx, word [ebx + 1]
shl edx, 8
mov dl, byte [ebx]
add word [dap.segment], 0x0020
jc halt
mov ecx, edx
and ecx, 0x0ff8
test ecx, 0x0ff8
jne .loop
mov ebx, dword [pointers.kernel]
;Parse kernel executable header,
;Go through relocation tables,
;Get kernel_start.
cli
lgdt [gdt]
mov eax, cr0
or al, 0x01
mov cr0, eax
jmp 0x08:kernel_start;get start from file header
gdt:
dw 0x28
dd gdt + 6
dq 0x0000_0000_0000_0000
dq 0x0040_9a00_0000_7fff;0x000000 - 0x007fff
dq 0x0040_9200_0000_7fff
dq 0x00c0_9a00_8000_0ff7;0x008000 - 0xffffff
dq 0x00c0_9200_8000_0ff7
dap:
dw 0x0010
.length dw 0x0003
.offset dw 0x7e00
.segment dw 0x0000
.start dd 0x0000_0001
.start_h dd 0x0000_0000
;ecx = sector
;ax = sector count
;bx out = address of start
allocate_and_load:
mov word [dap.length], ax
mov dword [dap.start], ecx
dec ax
shr ax, 3
inc ax
fat_allocate:
mov bx, 0x200e
xor cx, cx
mov dx, 0x2200
@ -189,50 +343,17 @@ fat_allocate:
and ebx, 0x0000_dfff
shl ebx, 12
mov dword [pointers.fat], ebx
mov dl, byte [fat_header.drive_number]
mov ax, word [fat_header.reserved_sectors]
mov word [dap.start], ax
mov word [dap.offset], bx
shr ebx, 16
and bx, 0xf000
mov word [dap.segment], bx
.load:
mov eax, ebx
mov word [dap.offset], ax
shr eax, 4
and ax, 0xf000
mov word [dap.segment], ax
mov ah, 0x42
mov si, dap
int 0x15
int 0x13
mov ebx, dword [pointers.fat]
;fat loaded - load kernel
cli
lgdt [gdt]
mov eax, cr0
or al, 0x01
mov cr0, eax
jmp 0x08:pmode
gdt:
dw 0x28
dd gdt + 6
dq 0x0000_0000_0000_0000
dq 0x0040_9a00_0000_7fff;0x000000 - 0x007fff
dq 0x0040_9200_0000_7fff
dq 0x00c0_9a00_8000_0ff7;0x008000 - 0xffffff
dq 0x00c0_9200_8000_0ff7
dap:
dw 0x0010
.length dw 0x0001
.offset dw 0x7e00
.segment dw 0x0000
.start dq 1
allocate:
;TODO
ret
halt:
@ -240,7 +361,3 @@ halt:
.hlt:
hlt
jmp .hlt
bits 32
pmode:

26
src/kernel/main.c Normal file
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@ -0,0 +1,26 @@
/*
Copyright 2019 Benji Dial
Permission to use, copy, modify, and/or distribute this
software for any purpose with or without fee is hereby
granted, provided that the above copyright notice and this
permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS
ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.
*/
#include "vga.h"
void main(void) {
put_sz("Welcome to Portland version 0.0.8!\n");
while (1)
put_sz("|\b/\b-\b\\\b");
}

71
src/kernel/vga.c Normal file
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@ -0,0 +1,71 @@
/*
Copyright 2019 Benji Dial
Permission to use, copy, modify, and/or distribute this
software for any purpose with or without fee is hereby
granted, provided that the above copyright notice and this
permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS
ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.
*/
#include "vga.h"
uint16_t cursor_pos = 0;
uint8_t color = 0xf0;
#define cols 80
#define rows 25
void scroll(void) {
cursor_pos -= cols * 2;
uint32_t *limit = (uint32_t *)(VGA_BUFFER + cols * (rows - 1));
for (uint32_t *i = (uint32_t *)VGA_BUFFER; i < limit; ++i)
*i = *(i + cols / 2);
limit += cols / 2;
uint32_t fill = (color * 0x0100 + (uint8_t)' ') * 0x00010001;
for (uint32_t *i = limit - cols / 2; i < limit; ++i)
*i = fill;
}
void put_char(uint8_t ch) {
switch (ch) {
case '\b':
if (cursor_pos)
VGA_BUFFER[cursor_pos -= 2] = (uint8_t)' ';
break;
case '\t':
while ((cursor_pos % (cols * 2)) % 20)
put_char(' ');
break;
case '\n':
if ((cursor_pos = (cursor_pos / (cols * 2) + 1) * (cols * 2)) >= cols * rows * 2)
scroll();
break;
default:
VGA_BUFFER[cursor_pos++] = ch;
VGA_BUFFER[cursor_pos++] = color;
if (cursor_pos == (cols * rows * 2))
scroll();
}
}
void put_sz(uint8_t *sz) {
while (*sz)
put_char(*(sz++));
}
void move_cursor(uint8_t col, uint8_t row) {
cursor_pos = (col + row * cols) * 2;
}
void set_color(uint8_t c) {
color = c;
}

31
src/kernel/vga.h Normal file
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@ -0,0 +1,31 @@
/*
Copyright 2019 Benji Dial
Permission to use, copy, modify, and/or distribute this
software for any purpose with or without fee is hereby
granted, provided that the above copyright notice and this
permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS
ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.
*/
#include <stdint.h>
#ifndef VGA_H
#define VGA_H
#define VGA_BUFFER ((uint8_t *)0x000b8000)
void put_char(uint8_t ch);
void put_sz(uint8_t *s);
void move_cursor(uint8_t col, uint8_t row);
void set_color(uint8_t c);
#endif