banan-os/bootloader/bios/boot.S

.code16

#########################################
#
# STAGE 1 BOOTLOADER
#
# its sole purpose is to load stage2 from
# bios boot partition
#
#########################################

.section .stage1

.global stage1_main
stage1_main:
	# setup segments and stack
	xorw %ax, %ax
	movw %ax, %ds
	movw %ax, %es
	movw %ax, %ss
	movl $0x7C00, %esp

	# save boot disk number
	call read_stage2_into_memory

	jmp stage2_main

.global print_and_halt
print_and_halt:
	call puts
halt:
	hlt
	jmp halt


#########################################
#
# STAGE 2 BOOTLOADER
#
#########################################

.section .stage2

stage2_main:
	# clear screen and enter 80x25 text mode
	movb $0x03, %al
	movb $0x00, %ah
	int $0x10

	# print hello message
	movw $hello_msg, %si
	call puts; call print_newline

	lgdt gdtr

	call enter_unreal_mode
	movw $unreal_enter_msg, %si
	call puts; call print_newline

	call enable_a20

	call get_memory_map

	call print_newline
	call read_user_command_line

	call print_newline

	movw $start_kernel_load_msg, %si
	call puts; call print_newline

	call print_memory_map

	call find_root_disk
	call find_root_partition

	call print_root_partition_info
	call print_newline

	call has_ext2_filesystem
	testb %al, %al
	jz print_and_halt

	call ext2_find_kernel
	movl $ext2_inode_read_bytes, %esi

	call elf_read_kernel_to_memory

	call vesa_set_video_mode

	cli

	# kernel entry point
	movl %eax, %ecx

	# setup kernel parameters
	movl $0xD3C60CFF, %eax
	movl $banan_boot_info, %ebx

	# setup protected mode
	movl %cr0, %edx
	orb $1, %dl
	movl %edx, %cr0

	# jump to protected mode
	ljmpl $0x18, $protected_mode

.code32
protected_mode:
	# setup protected mode segments
	movw $0x10, %dx
	movw %dx, %ds
	movw %dx, %es
	movw %dx, %fs
	movw %dx, %gs
	movw %dx, %ss

	# jump to kernel entry
	jmp *%ecx


.code16
enter_unreal_mode:
	cli
	pushw %ds

	movl %cr0, %eax
	orb $1, %al
	movl %eax, %cr0
	ljmpl $0x8, $.enter_unreal_mode_pmode

 .enter_unreal_mode_pmode:
	movw $0x10, %bx
	movw %bx, %ds

	andb $0xFE, %al
	movl %eax, %cr0
	ljmpl $0x0, $.enter_unreal_mode_unreal

 .enter_unreal_mode_unreal:
	popw %ds
	sti

	ret

hello_msg:
	.asciz "This is banan-os bootloader"

unreal_enter_msg:
	.asciz "Entered unreal mode"

start_kernel_load_msg:
	.asciz "Starting to load kernel"

gdt:
	.quad 0x0000000000000000
	.quad 0x008F9A000000FFFF # 16-bit code
	.quad 0x00CF92000000FFFF # 32-bit data
	.quad 0x00CF9A000000FFFF # 32-bit code
gdtr:
	.short . - gdt - 1
	.quad gdt

banan_boot_info:
	boot_command_line:
		.long command_line
	boot_framebuffer:
		.long framebuffer
	boot_memory_map:
		.long memory_map
Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00			`.code16`

			`#########################################`
			`#`
			`# STAGE 1 BOOTLOADER`
			`#`
			`# its sole purpose is to load stage2 from`
			`# bios boot partition`
			`#`
			`#########################################`

			`.section .stage1`

Bootloader: Split bootloader into multiple files This cleans up the code since bootloader is starting to near 1k lines 2023-11-14 03:26:03 +02:00			`.global stage1_main`
Bootloader: Continue work on bootloader Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D 2023-11-11 22:49:00 +02:00			`stage1_main:`
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`# setup segments and stack`
			`xorw %ax, %ax`
Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00			`movw %ax, %ds`
			`movw %ax, %es`
			`movw %ax, %ss`
Bootloader: Find root partition from GPT header 2023-11-13 18:55:48 +02:00			`movl $0x7C00, %esp`
Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00
			`# save boot disk number`
Bootloader: Split bootloader into multiple files This cleans up the code since bootloader is starting to near 1k lines 2023-11-14 03:26:03 +02:00			`call read_stage2_into_memory`
Bootloader: Find root partition from GPT header 2023-11-13 18:55:48 +02:00
Bootloader: Continue work on bootloader Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D 2023-11-11 22:49:00 +02:00			`jmp stage2_main`
Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00
Bootloader: Split bootloader into multiple files This cleans up the code since bootloader is starting to near 1k lines 2023-11-14 03:26:03 +02:00			`.global print_and_halt`
Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00			`print_and_halt:`
			`call puts`
			`halt:`
			`hlt`
			`jmp halt`


			`#########################################`
			`#`
			`# STAGE 2 BOOTLOADER`
			`#`
			`#########################################`

			`.section .stage2`
Bootloader: Continue work on bootloader Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D 2023-11-11 22:49:00 +02:00
Bootloader: Find root partition from GPT header 2023-11-13 18:55:48 +02:00			`stage2_main:`
			`# clear screen and enter 80x25 text mode`
			`movb $0x03, %al`
			`movb $0x00, %ah`
			`int $0x10`

			`# print hello message`
			`movw $hello_msg, %si`
			`call puts; call print_newline`

Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`lgdt gdtr`

Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00			`call enter_unreal_mode`
			`movw $unreal_enter_msg, %si`
			`call puts; call print_newline`

Bootloader: Try to enable A20 line if it is disabled VirtualBox seems to have A20 disabled by default 2024-01-11 22:03:52 +02:00			`call enable_a20`

Bootloader: Find root partition from GPT header 2023-11-13 18:55:48 +02:00			`call get_memory_map`
Bootloader: Try to enable A20 line if it is disabled VirtualBox seems to have A20 disabled by default 2024-01-11 22:03:52 +02:00
			`call print_newline`
Bootloader: Split bootloader into multiple files This cleans up the code since bootloader is starting to near 1k lines 2023-11-14 03:26:03 +02:00			`call read_user_command_line`
Bootloader: Find root partition from GPT header 2023-11-13 18:55:48 +02:00
			`call print_newline`

			`movw $start_kernel_load_msg, %si`
			`call puts; call print_newline`

			`call print_memory_map`

			`call find_root_disk`
			`call find_root_partition`

Bootloader: Split bootloader into multiple files This cleans up the code since bootloader is starting to near 1k lines 2023-11-14 03:26:03 +02:00			`call print_root_partition_info`
Bootloader: Implement basic ext2 filesystem This can search for files in an ext2 filesystem. Only 12 blocks are currently supported. Now only ELF loading is missing for loading the actual kernel! 2023-11-15 16:36:53 +02:00			`call print_newline`

			`call has_ext2_filesystem`
			`testb %al, %al`
			`jz print_and_halt`

			`call ext2_find_kernel`
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00			`movl $ext2_inode_read_bytes, %esi`

			`call elf_read_kernel_to_memory`

Bootloader: Search framebuffer information from kernel memory Framebuffer information is no longer hard coded into bootloader. Kernel can define framebuffer info structure in its memory which is used for finding proper video mode. 2023-12-09 17:32:10 +02:00			`call vesa_set_video_mode`
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00
Bootloader: Clear screen, better memcpy Clear screen before jumping to kernel. Memcpy now uses ebx as offset register, so only one register has to updated every loop 2023-11-17 20:31:42 +02:00			`cli`
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`# kernel entry point`
			`movl %eax, %ecx`

			`# setup kernel parameters`
			`movl $0xD3C60CFF, %eax`
			`movl $banan_boot_info, %ebx`

Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00			`# setup protected mode`
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`movl %cr0, %edx`
			`orb $1, %dl`
			`movl %edx, %cr0`
Bootloader: Continue work on bootloader Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D 2023-11-11 22:49:00 +02:00
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`# jump to protected mode`
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00			`ljmpl $0x18, $protected_mode`
Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00			`.code32`
			`protected_mode:`
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`# setup protected mode segments`
			`movw $0x10, %dx`
			`movw %dx, %ds`
			`movw %dx, %es`
			`movw %dx, %fs`
			`movw %dx, %gs`
			`movw %dx, %ss`

			`# jump to kernel entry`
Kernel/Bootloader: banan-os can now be booted with my bootloader :D 2023-11-17 20:33:02 +02:00			`jmp *%ecx`
Bootloader: Load kernel to memory and jump to it! 2023-11-17 16:36:29 +02:00

			`.code16`
Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00			`enter_unreal_mode:`
			`cli`
			`pushw %ds`

			`movl %cr0, %eax`
			`orb $1, %al`
			`movl %eax, %cr0`
			`ljmpl $0x8, $.enter_unreal_mode_pmode`

			`.enter_unreal_mode_pmode:`
			`movw $0x10, %bx`
			`movw %bx, %ds`

Bootloader: Try to enable A20 line if it is disabled VirtualBox seems to have A20 disabled by default 2024-01-11 22:03:52 +02:00			`andb $0xFE, %al`
Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00			`movl %eax, %cr0`
			`ljmpl $0x0, $.enter_unreal_mode_unreal`

			`.enter_unreal_mode_unreal:`
			`popw %ds`
			`sti`

			`ret`

Bootloader: Start work on bootloader I wrote a fast first stage bootloader and a installer to put it into a disk image. 2023-11-09 22:42:47 +02:00			`hello_msg:`
			`.asciz "This is banan-os bootloader"`

Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00			`unreal_enter_msg:`
			`.asciz "Entered unreal mode"`

Bootloader: Continue work on bootloader Bootloader can now get the memory map and read cmdline from user. Now 'just' video mode query, ext2 and ELF parsing are needed :D 2023-11-11 22:49:00 +02:00			`start_kernel_load_msg:`
			`.asciz "Starting to load kernel"`
Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00
			`gdt:`
			`.quad 0x0000000000000000`
Bootloader: cleanup code 2024-01-07 17:24:33 +02:00			`.quad 0x008F9A000000FFFF # 16-bit code`
			`.quad 0x00CF92000000FFFF # 32-bit data`
			`.quad 0x00CF9A000000FFFF # 32-bit code`
Bootloader enter unreal mode at the start of stage2 2023-11-17 14:22:21 +02:00			`gdtr:`
			`.short . - gdt - 1`
			`.quad gdt`
Kernel/Bootloader: banan-os can now be booted with my bootloader :D 2023-11-17 20:33:02 +02:00
			`banan_boot_info:`
			`boot_command_line:`
			`.long command_line`
Bootloader: Implement VESA video mode query and pass it to kernel Kernel now gets framebuffer from bootloader. Framebuffer dimensions and bpp are hardcoded in bootloader, but will probably be read from config file at some point. 2023-11-17 22:45:35 +02:00			`boot_framebuffer:`
			`.long framebuffer`
Kernel/Bootloader: banan-os can now be booted with my bootloader :D 2023-11-17 20:33:02 +02:00			`boot_memory_map:`
			`.long memory_map`