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fixing bootloader again but should work using nasm now

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This commit is contained in:
Gregory Kenneth Bowne
2025-08-06 01:42:17 -07:00
parent 16309bc306
commit dd68fd805f
2 changed files with 41 additions and 15 deletions
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23
bootloader/boot.asm
View File

@@ -119,20 +119,27 @@ verify_checksum:
lba_to_chs: lba_to_chs:
pusha pusha
xor dx, dx xor dx, dx
mov bx, [sectors_per_track] mov bx, [sectors_per_track]
div bx ; AX = LBA / sectors_per_track, DX = LBA % spt div bx ; AX = LBA / sectors_per_track, DX = remainder (sector number)
mov si, ax ; temp quotient mov si, ax ; SI = temp quotient (track index)
mov cx, [heads_per_cylinder] mov cx, [heads_per_cylinder]
xor dx, dx xor dx, dx
div cx ; AX = cylinder, DX = head div cx ; AX = cylinder, DX = head
mov ch, al ; CH = cylinder low mov ch, al ; CH = cylinder low byte
mov dh, dl ; DH = head mov dh, dl ; DH = head
mov cl, sil ; CL = sector number (0-based)
inc cl ; Sector is 1-based ; Now take sector number from earlier remainder
mov ah, al mov cx, si ; Copy track index to CX to access CL
and ah, 0xC0 ; upper 2 bits of cylinder and cl, 0x3F ; Mask to 6 bits (sector number)
or cl, ah ; insert upper cylinder bits into CL inc cl ; Sector numbers are 1-based
; Insert upper 2 bits of cylinder into CL
mov ah, al ; AH = cylinder again
and ah, 0xC0 ; Get top 2 bits of cylinder
or cl, ah ; OR them into sector byte
popa popa
ret ret

33
bootloader/boot1.asm
View File

@@ -88,7 +88,7 @@ real_mode_entry:
inc dword [MemoryMapEntries] inc dword [MemoryMapEntries]
test ebx, ebx test ebx, ebx
jnz .e820_loop jnz .e820_loop
jmp .e820_done jmp e820_done
e820_error: e820_error:
mov si, e820_error_msg mov si, e820_error_msg
@@ -112,9 +112,9 @@ vesa_error:
mov dx, 0x184F ; Lower-right corner mov dx, 0x184F ; Lower-right corner
int 0x10 int 0x10
jmp .e820_done ; Continue booting without VESA graphics jmp e820_done ; Continue booting without VESA graphics
.e820_done: e820_done:
; Back to protected mode ; Back to protected mode
cli cli
mov eax, cr0 mov eax, cr0
@@ -123,6 +123,7 @@ vesa_error:
jmp 0x08:protected_entry jmp 0x08:protected_entry
; ---------------------------------------------------------------- ; ----------------------------------------------------------------
[BITS 16]
print_string_16: print_string_16:
.loop: .loop:
lodsb lodsb
@@ -149,8 +150,9 @@ protected_entry:
rep stosd rep stosd
mov edi, page_table mov edi, page_table
rep stosd rep stosd
mov eax, page_table
mov dword [page_directory], page_table | 0x3 or eax, 0x3
mov [page_directory], eax
mov ecx, 1024 mov ecx, 1024
mov edi, page_table mov edi, page_table
mov eax, 0x00000003 mov eax, 0x00000003
@@ -168,6 +170,13 @@ protected_entry:
jmp kmain jmp kmain
halt:
cli
.hang:
hlt
jmp .hang
; ---------------------------------------------------------------- ; ----------------------------------------------------------------
; Data buffers and variables must be appropriately defined in your data section ; Data buffers and variables must be appropriately defined in your data section
MemoryMapBuffer times 128 db 0 ; 128*24 bytes reserved for E820 memory map (adjust size as needed) MemoryMapBuffer times 128 db 0 ; 128*24 bytes reserved for E820 memory map (adjust size as needed)
@@ -180,5 +189,15 @@ page_directory times 1024 dd 0
align 4096 align 4096
page_table times 1024 dd 0 page_table times 1024 dd 0
times 2047 - ($ - $$) db 0 ; Pad to the second-to-last byte of the 4th sector %assign pad_size 4096
checksum_byte db 0 ; This byte will be calculated and patched later %ifdef __SIZE__
%define size_current __SIZE__
%else
%define size_current ($ - $$)
%endif
%if size_current < pad_size
times pad_size - size_current db 0
%endif
checksum_byte db 0