diff options
| author | Carlos Maiolino <[email protected]> | 2025-07-17 19:20:26 +0200 |
|---|---|---|
| committer | Carlos Maiolino <[email protected]> | 2025-07-17 19:20:26 +0200 |
| commit | a485d59fdaf7b768f95539991d72421fb0ec85de (patch) | |
| tree | c7967769cace309a526af901ba4657ba0d4bdf28 /bootloader.asm | |
| parent | c91590e59f6f41b7316edd8587542ed24d0fdb22 (diff) | |
Restructure project folder
Signed-off-by: Carlos Maiolino <[email protected]>
Diffstat (limited to 'bootloader.asm')
| -rw-r--r-- | bootloader.asm | 94 |
1 files changed, 0 insertions, 94 deletions
diff --git a/bootloader.asm b/bootloader.asm deleted file mode 100644 index f42e702..0000000 --- a/bootloader.asm +++ /dev/null @@ -1,94 +0,0 @@ -ORG 0x7c00 -BITS 16 - -CODE_SEG equ gdt_code - gdt_start ; 0x8 -DATA_SEG equ gdt_data - gdt_start ; 0x10 -_start: - jmp short start - nop - -; Setup dummy BIOS Parameter block so a dumb BIOS does not corrupt us -; if it starts messing up with the parameter block - times 33 db 0 - -start: - ; Set CS to 0 with label step2 as its beginning offset - jmp 0:step2 - -step2: - ; Setup segments - - cli ; Disable interrupts - mov ax, 0 - mov ds, ax - mov es, ax - mov ss, ax - mov sp, 0x7c00 ; Stack segment starts right before ds - ; and grows down to 0x0. This works because - ; Intel implements a full descending stack - sti ; Enable interrupts - -.load_protected: - cli - lgdt[gdt_table] - mov eax, cr0 - or eax, 0x1 - mov cr0, eax - jmp CODE_SEG:start_32 - -; GDT table description -gdt_start: -gdt_null: ; First segment Descriptor is always 0 - dd 0x0 - dd 0x0 - -;Second segment descriptor... Code segment - 0x8 -gdt_code: - dw 0xffff ; Segment limit 0-15 - dw 0 ; Base address 0-15 - db 0 ; Base 16-23 - db 0x9a ; Access byte field 0b10011010 - - ; We don't have a 4 bits type, so use a byte type - ; to set both Segment limit high bits and flags - - db 11001111b ; Segment limit 16-19 - ; Flags 0-3 - db 0 ; Base address high bits 24-31 - -;Second segment descriptor... Data segment - 0x10 -gdt_data: - dw 0xffff ; Segment limit 0-15 - dw 0 ; Base address 0-15 - db 0 ; Base 16-23 - db 0x92 ; Access byte field 0b10010010 - db 11001111b ; Segment limit 16-19 - ; Flags 0-3 - db 0 ; Base address high bits 24-31 -gdt_end: - -gdt_table: - dw gdt_end - gdt_start - 1 - dd gdt_start - - -[BITS 32] - -; No access to BIOS from now on.... -start_32: - ; Set all segments to the same as the DATA_SEG - mov ax, DATA_SEG - mov ds, ax - mov es, ax - mov fs, ax - mov gs, ax - mov ss, ax - - ; Set the stack pointer and base pointer further in mem - mov ebp, 0x00200000 - mov esp, ebp - jmp $ - -; Fill in to the end and add bootloader signature - times 510 - ($ - $$) db 0 - dw 0xAA55 |