still need to read, parse root directory to find kernel and need to put boot signature at 0x7dfe to jump around
This commit is contained in:
commit
aeff38fe15
4 changed files with 278 additions and 0 deletions
4
doc/design/kernel_functions.txt
Normal file
4
doc/design/kernel_functions.txt
Normal file
|
|
@ -0,0 +1,4 @@
|
|||
allocate:
|
||||
ax in: number of pages
|
||||
dx in: process id
|
||||
ebx out: address, or 0x0000_0000 on failure
|
||||
16
doc/design/memory_map.txt
Normal file
16
doc/design/memory_map.txt
Normal file
|
|
@ -0,0 +1,16 @@
|
|||
0x0000 - 0x03ff : interrupt vector table
|
||||
0x0400 - 0x04ff : bios data area
|
||||
0x0500 - 0x05ff : structure pointers
|
||||
0x00 dword : fat pointer
|
||||
0x0600 - 0x1fff : not assigned
|
||||
0x2000 - 0x3fff : memory map
|
||||
for each word : 1 page
|
||||
0x0000 = free
|
||||
0x0001 = unavailable
|
||||
0x0002 = kernel
|
||||
other = process number
|
||||
|
||||
0x4000 - 0x6fff : not assigned
|
||||
0x7000 - 0x7bff : bootloader scratch
|
||||
0x7000 : memory map bios buffer
|
||||
0x7c00 - 0x7fff : bootloader
|
||||
12
makefile
Normal file
12
makefile
Normal file
|
|
@ -0,0 +1,12 @@
|
|||
floppy: out bootloader
|
||||
mkfs.fat -C -f 1 -F 12 -n "PORTLAND OS" -R 2 -S 512 out/floppy.img 1440
|
||||
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
|
||||
|
||||
obj:
|
||||
mkdir -p obj
|
||||
|
||||
out:
|
||||
mkdir -p out
|
||||
246
src/bootloader.asm
Normal file
246
src/bootloader.asm
Normal file
|
|
@ -0,0 +1,246 @@
|
|||
;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.
|
||||
|
||||
pointers:
|
||||
.fat equ 0x0500
|
||||
|
||||
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
|
||||
.n_fats equ 0x7c10;0x01 - assumed
|
||||
.directory_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
|
||||
.long_sectors equ 0x7c20;0x0000_0000 - assumed
|
||||
.drive_number equ 0x7c24; - ignored, used as scratch
|
||||
.flags equ 0x7c25; - ignored
|
||||
.signature equ 0x7c26;0x29 - halts on other values
|
||||
.id equ 0x7c27; - ignored
|
||||
.label equ 0x7c2b;PORTLAND OS - assumed
|
||||
.fs_type equ 0x7c36;FAT12 - assumed
|
||||
|
||||
org 0x7c3e
|
||||
bits 16
|
||||
|
||||
in al, 0x92
|
||||
or al, 0x02
|
||||
out 0x92, al
|
||||
|
||||
mov ah, 0x42
|
||||
mov si, dap
|
||||
int 0x13
|
||||
|
||||
mov byte [fat_header.drive_number], dl
|
||||
|
||||
memory:
|
||||
mov bx, 0x2010
|
||||
mov eax, 0x0001_0001
|
||||
.clear:
|
||||
mov dword [bx], eax
|
||||
add bx, 4
|
||||
test bx, 0x4000
|
||||
jne .clear
|
||||
|
||||
xor ax, ax
|
||||
mov es, ax
|
||||
mov si, 0x7000
|
||||
xor ebx, ebx
|
||||
|
||||
.loop:
|
||||
mov eax, 0x0000_e820
|
||||
mov ecx, 24
|
||||
mov edx, 0x534d_4150
|
||||
int 0x15
|
||||
jc .done
|
||||
|
||||
test cl, 24
|
||||
jne .not_24
|
||||
|
||||
test byte [0x7014], 0x01
|
||||
jz .loop
|
||||
|
||||
.not_24:
|
||||
test dword [0x7010], 1
|
||||
jne .loop
|
||||
|
||||
test byte [0x7003], 0
|
||||
jne .loop
|
||||
|
||||
test dword [0x7004], 0
|
||||
jne .loop
|
||||
|
||||
test dword [0x700c], 0
|
||||
je .check_lower
|
||||
|
||||
mov dword [0x7008], 0xffff_ffff
|
||||
|
||||
.check_lower:
|
||||
test dword [0x7008], 0
|
||||
je .loop
|
||||
|
||||
mov edx, ebx
|
||||
mov ebx, dword [0x7000]
|
||||
mov eax, ebx
|
||||
add eax, dword [0x7008]
|
||||
jnc .pagify
|
||||
mov eax, 0xffff_ffff
|
||||
|
||||
.pagify:
|
||||
dec ebx
|
||||
shr ebx, 12
|
||||
inc ebx
|
||||
shr eax, 12
|
||||
dec eax
|
||||
|
||||
test eax, 0xffff_f000
|
||||
jz .maxed
|
||||
mov eax, 0x0000_0fff
|
||||
|
||||
.maxed:
|
||||
inc eax
|
||||
test eax, ebx
|
||||
je .next
|
||||
|
||||
shl ebx, 1
|
||||
or ebx, 0x2000
|
||||
shl eax, 1
|
||||
add eax, 0x2000
|
||||
mov ecx, eax
|
||||
|
||||
xor ax, ax
|
||||
.free_loop:
|
||||
mov word [ebx], ax
|
||||
add ebx, 2
|
||||
test ebx, ecx
|
||||
jne .free_loop
|
||||
|
||||
.next:
|
||||
mov ebx, edx
|
||||
jmp .loop
|
||||
|
||||
.done:
|
||||
mov dword [0x2000], 0x0002_0002
|
||||
mov dword [0x2004], 0x0002_0002
|
||||
mov dword [0x2008], 0x0002_0002
|
||||
mov dword [0x200c], 0x0002_0002
|
||||
|
||||
test byte [fat_header.signature], 0x29
|
||||
jne halt
|
||||
|
||||
mov ax, word [fat_header.sectors_per_fat]
|
||||
mov word [dap.length], ax
|
||||
|
||||
dec ax
|
||||
shr ax, 3
|
||||
inc ax
|
||||
|
||||
fat_allocate:
|
||||
mov bx, 0x200e
|
||||
xor cx, cx
|
||||
mov dx, 0x2200
|
||||
|
||||
.loop:
|
||||
add bx, 2
|
||||
test bx, dx
|
||||
je halt
|
||||
|
||||
test word [bx], 0x0000
|
||||
je .eq
|
||||
|
||||
xor cx, cx
|
||||
jmp .loop
|
||||
|
||||
.eq:
|
||||
inc cx
|
||||
test cx, ax
|
||||
jne .loop
|
||||
|
||||
dec ax
|
||||
shl ax, 1
|
||||
sub bx, ax
|
||||
mov dx, bx
|
||||
|
||||
mov ax, 0x0002
|
||||
.mark_loop:
|
||||
mov word [bx], ax
|
||||
loop .mark_loop
|
||||
|
||||
mov bx, dx
|
||||
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
|
||||
|
||||
mov ah, 0x42
|
||||
mov si, dap
|
||||
int 0x15
|
||||
|
||||
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:
|
||||
cli
|
||||
.hlt:
|
||||
hlt
|
||||
jmp .hlt
|
||||
|
||||
bits 32
|
||||
pmode:
|
||||
|
||||
Reference in a new issue