bootloader/arch/x86_64/boot.S

@@ -1,10 +1,9 @@
 # FIXME: don't assume 512 byte sectors
-.set SECTOR_SIZE,		512
+.set SECTOR_SIZE_SHIFT,	9
-
+.set SECTOR_SIZE,		1 << SECTOR_SIZE_SHIFT
-.set GPT_HEADER_ADDR,	free_memory_start
-.set GPT_ENTRY_ADDR,	free_memory_start + SECTOR_SIZE
-
 
+.set SCREEN_WIDTH,	80
+.set SCREEN_HEIGHT,	25
 
 .code16
 
@@ -20,42 +19,49 @@
 .section .stage1
 
 stage1_start:
-	jmp main
+	jmp stage1_main
 
-# al:		character to print
+# prints character to screen
+# al:		ascii character to print
 putc:
-	mov $0x0E, %ah
+	pusha
+	movb $0x0E, %ah
+	movb $0x00, %bh
 	int $0x10
+	popa
 	ret
 
-# ds:si:	null terminated string to print
+# prints null terminated string to screen
+# ds:si:	string address
 puts:
-	push %si
+	pushw %si
-	push %ax
+	pushw %bx
+	pushw %ax
 
-1:
+	movb $0x0E, %ah
+	movb $0x00, %bh
+
+.puts_loop:
 	lodsb
 
 	test %al, %al
-	jz 2f
+	jz .puts_done
 
-	call putc
+	int $0x10
-	jmp 1b
+	jmp .puts_loop
 
-2:
+.puts_done:
-	mov $'\r', %al
+	popw %ax
-	call putc
+	popw %bx
-	mov $'\n', %al
+	popw %si
-	call putc
-
-	pop %ax
-	pop %si
 	ret
 
+# compares memory between addresses
 # si:		ptr1
 # di:		ptr2
-# cx:		count
+# cx:		bytes count
-# return:	1 if equal, 0 otherwise
+# return:
+#	al: 1 if equal, 0 otherwise
 memcmp:
 	pushw %si
 	pushw %di
@@ -70,12 +76,10 @@ memcmp:
 
 
 # read sectors from disk
-#
 # bx:eax:	lba start
 # cx:		lba count (has to less than 0x80)
 # dl:		drive number
 # ds:di:	physical address
-#
 # returns only on success
 read_from_disk:
 	push %ax
@@ -103,7 +107,78 @@ read_from_disk:
 	ret
 
 
-main:
+# Validates that GPT header is valid and usable
+# doesn't return on invalid header
+validate_gpt_header:
+	# confirm header (starts with 'EFI PART')
+	cmpl $0x20494645, (gpt_header + 0)
+	jne .not_gpt_partition
+	cmpl $0x54524150, (gpt_header + 4)
+	jne .not_gpt_partition
+	ret
+
+
+# Find partition entry with type guid
+# si:	address of type guid
+# dl:	drive number
+# returns:
+#   al: non-zero if found
+#	di: address of partition entry
+find_gpt_partition_entry:
+	# eax := entry_count
+	movl (gpt_header + 80), %eax
+	test %eax, %eax
+	jz .no_gpt_partition_found
+
+	# edx:eax := eax * entry_size
+	pushw %dx
+	mull (gpt_header + 84)
+	test %edx, %edx
+	jnz .too_gpt_big_entries
+	popw %dx
+
+	# FIXME: read one entry array section at a time
+
+	# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
+	movl %eax, %ecx
+	shrl $SECTOR_SIZE_SHIFT, %ecx
+
+	# start lba
+	movl (gpt_header + 72), %eax
+	movw (gpt_header + 76), %bx
+
+	movw $gpt_entry_data, %di
+
+	call read_from_disk
+
+	# NOTE: 'only' 0xFFFF partitions supported,
+	#       although read will fail with more than 0x80
+	movw (gpt_header + 80), %cx
+
+.loop_gpt_entries:
+	pushw %cx
+	movw $16, %cx
+	call memcmp
+	popw %cx
+
+	testb %al, %al
+	jnz .gpt_partition_found
+
+	# add entry size to entry pointer
+	addw (gpt_header + 84), %di
+
+	loop .loop_gpt_entries
+
+.no_gpt_partition_found:
+	movb $0, %al
+	ret
+
+.gpt_partition_found:
+	movb $1, %al
+	ret
+
+
+stage1_main:
 	# setup segments
 	movw $0, %ax
 	movw %ax, %ds
@@ -129,61 +204,19 @@ main:
 	movw $0, %bx
 	movw $1, %cx
 	movb (boot_disk_number), %dl
-	movw $GPT_HEADER_ADDR, %di
+	movw $gpt_header, %di
 	call read_from_disk
 
-	# confirm header (starts with 'EFI PART')
+	call validate_gpt_header
-	cmpl $0x20494645, (GPT_HEADER_ADDR + 0)
-	jne .not_gpt_partition
-	cmpl $0x54524150, (GPT_HEADER_ADDR + 4)
-	jne .not_gpt_partition
 
-	# eax := entry_count
+	movw $bios_boot_guid, %si
-	movl (GPT_HEADER_ADDR + 80), %eax
+	movb boot_disk_number, %dl
-	test %eax, %eax
+	call find_gpt_partition_entry
+	testb %al, %al
 	jz .no_bios_boot_partition
 
-	# edx:eax := eax * entry_size
+	# BIOS boot partiton found!
-	mull (GPT_HEADER_ADDR + 84)
-	test %edx, %edx
-	jnz .too_gpt_big_entries
 
-	# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
-	pushl %eax
-	addl $(SECTOR_SIZE - 1), %eax
-	movl $SECTOR_SIZE, %ecx
-	divl %ecx
-	movl %eax, %ecx
-	popl %eax
-
-	# start lba
-	movl (GPT_HEADER_ADDR + 72), %eax
-	movw (GPT_HEADER_ADDR + 76), %bx
-
-	movb (boot_disk_number), %dl
-	movw $GPT_ENTRY_ADDR, %di
-	call read_from_disk
-
-	# NOTE: 'only' 0xFFFF partitions supported
-	movw (GPT_HEADER_ADDR + 80), %cx
-
-.loop_entries:
-	push %cx
-	movw $16, %cx
-	movw $bios_boot_guid, %si
-	call memcmp
-	pop %cx
-
-	testb %al, %al
-	jnz .bios_boot_found
-
-	# add entry size to entry pointer
-	addw (GPT_HEADER_ADDR + 84), %di
-
-	loop .loop_entries
-	jmp .no_bios_boot_partition
-
-.bios_boot_found:
 	# first lba
 	movl 32(%di), %eax
 	movw $0, %bx
@@ -200,7 +233,7 @@ main:
 	movw $stage2_start, %di
 
 	call read_from_disk
-	jmp stage2_start
+	jmp stage2_main
 
 print_and_halt:
 	call puts
@@ -229,7 +262,6 @@ halt:
 	jmp print_and_halt
 
 
-
 # 21686148-6449-6E6F-744E-656564454649
 bios_boot_guid:
 	.long 0x21686148		# little endian
@@ -245,7 +277,7 @@ read_failed_msg:
 	.asciz "read error"
 
 not_gpt_partition_msg:
-	.asciz "not gpt"
+	.asciz "not GPT"
 
 no_bios_boot_partition_msg:
 	.asciz "no bios boot partition"
@@ -256,10 +288,6 @@ too_gpt_big_entries_msg:
 boot_disk_number:
 	.skip 1
 
-disk_address_packet:
-	.skip 16
-
-
 
 #########################################
 #
@@ -268,7 +296,247 @@ disk_address_packet:
 #########################################
 
 .section .stage2
+
 stage2_start:
+
+# read a character from keyboard
+# return:
+#	al: ascii
+#	ah: bios scan code
+getc:
+	movb $0x00, %ah
+	int $0x16
+	ret
+
+
+# prints newline to screen
+print_newline:
+	pushw %ax
+	movb $'\r', %al
+	call putc
+	movb $'\n', %al
+	call putc
+	pop %ax
+	ret
+
+
+# prints backspace to screen, can go back a line
+print_backspace:
+	pusha
+
+	# get cursor position
+	movb $0x03, %ah
+	movb $0x00, %bh
+	int $0x10
+
+	# don't do anyting if on first row
+	testb %dh, %dh
+	jz .print_backspace_done
+
+	# go one line up if on first column
+	test %dl, %dl
+	jz .print_backspace_go_line_up
+
+	# otherwise decrease column
+	decb %dl
+	jmp .print_backspace_do_print
+
+.print_backspace_go_line_up:
+	# decrease row and set column to the last one
+	decb %dh
+	movb $(SCREEN_WIDTH - 1), %dl
+
+.print_backspace_do_print:
+	# set cursor position
+	movb $0x02, %ah
+	int $0x10
+
+	# print 'empty' character (space)
+	mov $' ', %al
+	call putc
+
+	# set cursor position
+	movb $0x02, %ah
+	int $0x10
+
+.print_backspace_done:
+	popa
+	ret
+
+
+# print number to screen
+# ax:	number to print
+# bx:	number base
+# cx:	min width (zero pads if shorter)
+printnum:
+	pusha
+	pushw %cx
+
+	movw $printnum_buffer, %si
+	xorw %cx, %cx
+
+.printnum_fill_loop:
+	# fill buffer with all remainders ax % bx
+	xorw %dx, %dx
+	divw %bx
+	movb %dl, (%si)
+	incw %si
+	incw %cx
+	testw %ax, %ax
+	jnz .printnum_fill_loop
+
+	# check if zero pad is required
+	popw %dx
+	cmpw %cx, %dx
+	jbe .printnum_print_loop
+
+	xchgw %dx, %cx
+	subw %dx, %cx
+	movb $'0', %al
+.printnum_pad_zeroes:
+	call putc
+	loop .printnum_pad_zeroes
+
+	movw %dx, %cx
+
+.printnum_print_loop:
+	decw %si
+	movb (%si), %al
+	cmpb $10, %al
+	jae 1f
+	addb $'0', %al
+	jmp 2f
+1:	addb $('a' - 10), %al
+2:	call putc
+	loop .printnum_print_loop
+
+	popa
+	ret
+
+
+# test if character is printable ascii
+# al:	character to test
+# sets ZF if is printable
+isprint:
+	cmpb $0x20, %al
+	jb .isprint_done
+	cmpb $0x7E, %al
+	ja .isprint_done
+	cmpb %al, %al
+.isprint_done:
+	ret
+
+
+# fills memory map data structure
+# doesn't return on error
+get_memory_map:
+	pusha
+
+	movl $0, (memory_map_entry_count)
+
+	movl $0x0000E820, %eax
+	movl $0x534D4150, %edx
+	xorl %ebx, %ebx
+	movl $20, %ecx
+	movw $memory_map_entries, %di
+
+	clc
+	int $0x15
+	# If first call returs with CF set, the call failed
+	jc .get_memory_map_error
+
+.get_memory_map_rest:
+	cmpl $0x534D4150, %eax
+	jne .get_memory_map_error
+
+	# FIXME: don't assume BIOS to always return 20 bytes
+	cmpl $20, %ecx
+	jne .get_memory_map_error
+
+	# increment entry count
+	incl (memory_map_entry_count)
+
+	# increment entry pointer
+	addw %cx, %di
+
+	# BIOS can indicate end of list by 0 in ebx
+	testl %ebx, %ebx
+	jz .get_memory_map_done
+
+	movl $0x0000E820, %eax
+	movl $0x534D4150, %edx
+
+	clc
+	int $0x15
+	# BIOS can indicate end of list by setting CF
+	jnc .get_memory_map_rest
+
+.get_memory_map_done:
+	popa
+	ret
+
+.get_memory_map_error:
+	movw $memory_map_error_msg, %si
+	jmp print_and_halt
+
+
+# fills command line buffer
+get_command_line:
+	pusha
+
+	movw $command_line_enter_msg, %si
+	call puts
+
+	movw $command_line_buffer, %di
+
+.get_command_line_loop:
+	call getc
+
+	cmpb $'\b', %al
+	je .get_command_line_backspace
+
+	# Not sure if some BIOSes return '\n' as enter, but check it just in case
+	cmpb $'\r', %al
+	je .get_command_line_done
+	cmpb $'\n', %al
+	je .get_command_line_done
+
+	call isprint
+	jnz .get_command_line_loop
+
+	# put byte to buffer
+	movb %al, (%di)
+	incw %di
+
+	# print byte
+	call putc
+
+	jmp .get_command_line_loop
+
+.get_command_line_backspace:
+	# don't do anything if at the beginning
+	cmpw $command_line_buffer, %di
+	je .get_command_line_loop
+
+	# decrement buffer pointer
+	decw %di
+
+	# erase byte in display
+	call print_backspace
+
+	jmp .get_command_line_loop
+
+.get_command_line_done:
+	# null terminate command line
+	movb $0, (%di)
+
+	call print_newline
+
+	popa
+	ret
+
+
+stage2_main:
 	# clear screen and enter 80x25 text mode
 	movb $0x03, %al
 	movb $0x00, %ah
@@ -277,11 +545,123 @@ stage2_start:
 	# print hello message
 	movw $hello_msg, %si
 	call puts
+	call print_newline
+
+	call get_memory_map
+	call get_command_line
+
+	call print_newline
+
+	movw $start_kernel_load_msg, %si
+	call puts
+	call print_newline
+
+	movw $command_line_msg, %si
+	call puts
+	movw $command_line_buffer, %si
+	call puts
+	call print_newline
+
+	movw $memory_map_msg, %si
+	call puts
+	call print_newline
+
+	movl (memory_map_entry_count), %edx
+	movw $memory_map_entries, %si
+
+	movw $16, %bx
+	movw $4, %cx
+
+.loop_memory_map:
+	movb $' ', %al
+	call putc
+	call putc
+	call putc
+	call putc
+
+	movw 0x06(%si), %ax
+	call printnum
+	movw 0x04(%si), %ax
+	call printnum
+	movw 0x02(%si), %ax
+	call printnum
+	movw 0x00(%si), %ax
+	call printnum
+
+	movb $',', %al
+	call putc
+	movb $' ', %al
+	call putc
+
+	movw 0x0E(%si), %ax
+	call printnum
+	movw 0x0C(%si), %ax
+	call printnum
+	movw 0x0A(%si), %ax
+	call printnum
+	movw 0x08(%si), %ax
+	call printnum
+
+	movb $',', %al
+	call putc
+	movb $' ', %al
+	call putc
+
+	movw 0x12(%si), %ax
+	call printnum
+	movw 0x10(%si), %ax
+	call printnum
+
+	call print_newline
+
+	addw $20, %si
+
+	decl %edx
+	jnz .loop_memory_map
+
+
+	jmp halt
 
-1:
-	jmp 1b
 
 hello_msg:
 	.asciz "This is banan-os bootloader"
 
+command_line_msg:
+command_line_enter_msg:
+	.asciz "cmdline: "
+
+memory_map_msg:
+	.asciz "memmap:"
+
+memory_map_error_msg:
+	.asciz "Failed to get memory map"
+
+start_kernel_load_msg:
+	.asciz "Starting to load kernel"
+
 stage2_end:
+
+
+.section .bss
+
+.align SECTOR_SIZE
+gpt_header:
+	.skip SECTOR_SIZE
+gpt_entry_data:
+	.skip SECTOR_SIZE
+
+disk_address_packet:
+	.skip 16
+
+printnum_buffer:
+	.skip 10
+
+memory_map_entry_count:
+	.skip 4
+# 100 entries should be enough...
+memory_map_entries:
+	.skip 20 * 100
+
+# 100 character command line
+command_line_buffer:
+	.skip 100

bootloader/arch/x86_64/linker.ld

@@ -1,11 +1,11 @@
 SECTIONS
 {
 	. = 0x7C00;
-	.stage1 : { *(.stage1*) }
+	.stage1 : { *(.stage1) }
 
 	. = ALIGN(512);
 	.stage2 : { *(.stage2) }
 
 	. = ALIGN(512);
-	free_memory_start = .;
+	.bss : { *(.bss) }
 }

bootloader/build-and-run.sh

@@ -42,4 +42,4 @@ if [ "$1" == "debug" ] ; then
 fi
 
 echo running qemu
-qemu-system-x86_64 $QEMU_FLAGS --drive format=raw,file=test.img
+env BANAN_DISK_IMAGE_PATH=${DISK_IMAGE_PATH} BANAN_ARCH=x86_64 ../script/qemu.sh $QEMU_FLAGS