7 files changed, 443 insertions, 0 deletions
diff --git a/arch/x86/boot/bootloader/Makefile b/arch/x86/boot/bootloader/Makefile
new file mode 100644
index 0000000..e026e24
--- /dev/null
+++ b/arch/x86/boot/bootloader/Makefile
@@ -0,0 +1,39 @@
+# If you want run this makefile immediately, then set environment
+# variables (CC, LD, AS, OBJDUMP) to path of your cross-compiler.
+#
+# The best way to compile $BOOTBIN is to run the corresponding
+# target in the main Makefile, which is in the root of the
+# project (.../path/to/os/Makefile)
+
+BOOTBIN = bootloader.bin
+
+.PHONY: all objdump clean
+
+all: $(BOOTBIN)
+
+$(BOOTBIN): bootsect.bin setup.bin
+	cat $^ > $@
+
+bootsect.bin: bootsect.o
+	$(CC) -Wl,--oformat binary -Ttext 0x7c00 -o $@ \
+		-ffreestanding -nostdlib \
+		$^ -lgcc
+
+setup.bin: setup.o
+	$(CC) -Wl,--oformat binary -Ttext 0x0200 -o $@ \
+		-ffreestanding -nostdlib \
+		$^ -lgcc
+
+%.o: %.s
+	$(AS) $< -o $@
+
+objdump-bootsect:
+	$(OBJDUMP) -D -m i386 -b binary \
+		--adjust-vma=0x7c00 -Maddr16,data16 bootsect.bin
+
+objdump-setup:
+	$(OBJDUMP) -D -m i386 -b binary \
+		--adjust-vma=0x2000 -Maddr16,data16 setup.bin
+
+clean:
+	rm -rf bootsect.o setup.o $(BOOTBIN)
diff --git a/arch/x86/boot/bootloader/bios.inc b/arch/x86/boot/bootloader/bios.inc
new file mode 100644
index 0000000..19cd9a0
--- /dev/null
+++ b/arch/x86/boot/bootloader/bios.inc
@@ -0,0 +1,20 @@
+# CONVENTION: macro only uses %AX, %SI registers
+.macro BIOS_PRINT string
+	mov $0x0e, %ah				# Set writing char in TTY mode routine
+	mov \string, %si			# Set in Source Index reg the beginning
+								# address of a string
+print_loop\@:
+	lodsb						# Increase SI by 1 byte => get next char
+	or %al, %al					# Check for a '\0'
+	jz print_done\@
+
+	int $0x10					# Print a char in al register
+	jmp print_loop\@
+print_done\@:
+.endm
+
+.macro PUTCHAR char
+	mov $0x0e, %ah				# Set writing char in TTY mode routine
+	mov \char, %al
+	int $0x10					# Print a char in al register
+.endm
diff --git a/arch/x86/boot/bootloader/bootsect.s b/arch/x86/boot/bootloader/bootsect.s
new file mode 100644
index 0000000..a6e274e
--- /dev/null
+++ b/arch/x86/boot/bootloader/bootsect.s
@@ -0,0 +1,57 @@
+/*
+	bootsect.s is loaded at 0x7c00 (BIOS likes always to load the boot
+	sector to this address). It is first stage bootloader, it has one
+	task - loads setup.s (second stage) to 0x90000 and jumps there.
+*/
+
+.code16							# Tell GAS to generate 16 bit code
+
+.include "bios.inc"
+.include "rm_seg.inc"
+
+.global _start					# Make the symbol visible to ld
+_start:
+	jmp $0x0, $_start2			# Normalize the start address
+								# CS = 0 and IP = _start2
+_start2:
+	mov $SDATASEG, %ax			# We will store the boot drive at
+	mov %ax, %ds				# $SDATASEG in the first byte
+	mov $SETUPSEG, %ax			# Do it for disk read routine (see below)
+	mov %ax, %es
+
+	cld							# Set direction flag for incrementing
+	mov %dl, (0)				# BIOS stores our boot drive in DL,
+								# so we remember it
+	mov %cs, %ax				# AX = CS = 0 (see above)
+	mov %ax, %ds				# Zero data segment register
+
+load_setup:
+	BIOS_PRINT $load_setup_msg	# The routine uses only AX register
+
+	mov $0x02, %ah				# Set BIOS read sector routine
+	mov $0x00, %ch				# Select cylinder 0
+	mov $0x00, %dh				# Select head 0 [has a base of 0]
+	mov $0x02, %cl				# Select sector 2 (next after the
+								# boot sector) [has a base of 1]
+	mov $SETUPLEN, %al			# Read $SETUPLEN sectors
+	mov $0x0, %bx				# Load sectors to ES:BX ($SETUPSEG:0)
+	int $0x13					# Start reading from drive
+	jc disk_error				# If carry flag set, bios failed to read
+
+	# Make a far jump to our setup code
+	jmp $SETUPSEG, $0x0
+
+disk_error:
+	BIOS_PRINT $disk_error_msg
+	jmp .
+
+load_setup_msg:
+	.asciz "Loading setup sectors\r\n"
+
+disk_error_msg:
+	.asciz "Disk read error!"
+
+# Bootsector padding
+.space 512 - 2 - (. - _start), 0
+boot_flag:
+	.word 0xAA55
diff --git a/arch/x86/boot/bootloader/head.s b/arch/x86/boot/bootloader/head.s
new file mode 100644
index 0000000..d24e36c
--- /dev/null
+++ b/arch/x86/boot/bootloader/head.s
@@ -0,0 +1,35 @@
+/*
+	head.s is loaded at 0x1000 (by second stage), its main goal
+	is run 32-bit startup code.
+
+	After that manipulations it jumps to kernel written by C
+*/
+
+.code32							# Tell GAS to generate 32 bit code
+.extern kernel_main
+
+.set CODESEG, 0x08
+.set DATASEG, 0x10
+
+.global _start
+_start:
+	mov $DATASEG, %ax			# Point segment registers to the
+	mov %ax, %ds				# data selector we defined in our GDT
+	mov %ax, %es
+	mov %ax, %ss
+	mov %ax, %fs
+	mov %ax, %gs
+
+	mov $0x90000, %ebp			# Update stack position so it is right
+	mov %ebp, %esp				# at the top of the free space.
+
+check_a20:
+	mov $0x112345, %edi			# Odd megabyte address
+	mov $0x012345, %esi			# Even megabyte address
+	mov %esi, (%esi)			# If A20 line is disabled two pointers
+	mov %edi, (%edi)			# would point to the address 0x012345
+	cmpsd						# Compare values at addresses
+	je .						# If equivalent, loop forever
+
+	call kernel_main
+	jmp . 						# infinite loop
diff --git a/arch/x86/boot/bootloader/linker.ld b/arch/x86/boot/bootloader/linker.ld
new file mode 100644
index 0000000..5e8dfd6
--- /dev/null
+++ b/arch/x86/boot/bootloader/linker.ld
@@ -0,0 +1,10 @@
+OUTPUT_FORMAT("binary")
+OUTPUT_ARCH(i386)
+ENTRY(_start)
+
+SECTIONS
+{
+	/* BIOS likes always to load the boot sector to the address 0x7c00,
+	where it is sure will not be occupied by important routines. */
+	. = 0x7c00;
+}
diff --git a/arch/x86/boot/bootloader/rm_seg.inc b/arch/x86/boot/bootloader/rm_seg.inc
new file mode 100644
index 0000000..f6d4750
--- /dev/null
+++ b/arch/x86/boot/bootloader/rm_seg.inc
@@ -0,0 +1,14 @@
+/*
+	Real mode segment constants.
+
+	NOTE: Header file only for assembler
+*/
+
+# Addresses of RAM:
+.set BOOTSEG, 0x07c0			# Address of boot sector
+.set SDATASEG, 0x9000			# System data 
+.set SETUPLEN, 2				# Number of setup sectors
+.set SETUPSEG, 0x9020			# Setup address
+.set KERNSEG, 0x0100			# Historical load address
+.set KERNSIZE, 0x1000			# Kernel size, interpret as a segment
+.set KERNADDR, KERNSEG * 0x10
diff --git a/arch/x86/boot/bootloader/setup.s b/arch/x86/boot/bootloader/setup.s
new file mode 100644
index 0000000..2afc974
--- /dev/null
+++ b/arch/x86/boot/bootloader/setup.s
@@ -0,0 +1,268 @@
+/*
+	setup.s is second stage bootloader loaded at 0x90200 (by 
+	first stage), is responsible for getting the system data
+	from the BIOS.
+
+	System data puts at special place: 0x90000-0x901FF.
+*/
+
+.code16							# Tell GAS to generate 16 bit code
+
+.include "bios.inc"
+.include "rm_seg.inc"
+
+.set ENDSEG, KERNSEG + KERNSIZE	# Where to stop loading kernel
+
+# Define some constants for the GDT segment descriptor offsets
+.set CODESEG, gdt_code - gdt_start
+.set DATASEG, gdt_data - gdt_start
+
+# Keyboard Controller commands: 
+.set READ_OUTP, 0xD0			# Read Output Port
+.set WRITE_OUTP, 0xD1			# Write Output Port
+
+.global _start					# Make the symbol visible to ld
+_start:
+	mov $SDATASEG, %ax
+	mov %ax, %ds
+	mov %ax, %ss
+	mov $KERNSEG, %ax
+	mov %ax, %es
+
+	mov $0xFF00, %bp			# Set up the stack at 0x9ff00
+	mov %bp, %sp
+
+	BIOS_PRINT $get_data_msg
+
+	# Get current cursor position
+	mov $0x3, %ah
+	xor	%bh, %bh				# Page Number = 0
+	int $0x10
+	add $3, %dh					# Add number of next BIOS_PRINTs
+	mov %dx, (2)				# Save it
+
+	# Get disk drive parameters
+	xor %ax, %ax
+	mov %ax, %es				# ES:DI = 0x0000:0x0000 to guard
+	mov %ax, %di				# against BIOS bugs
+	mov (0), %dl				# Set drive boot
+	mov $0x8, %ah
+	int $0x13
+	jc disk_error
+
+	# Interrupt return:
+	# - CH = low eight bits of maximum cylinder number
+	# - CL = maximum sector number (bits 5-0)
+	#        high two bits of maximum cylinder number (bits 7-6)
+	# - DH = maximum head number
+	xor %ch, %ch
+	and $0b00111111, %cl
+	xor %dl, %dl
+	mov %dx, heads
+	mov %cx, sectors
+
+	# TODO: get memory size
+	# TODO: get video infos
+
+load_kernel:					# Load our kernel
+	BIOS_PRINT $boot_load_kern_msg
+
+	# Load the system at $KERNSEG address:
+	mov $KERNSEG, %ax
+	mov %ax, %es				# ES - starting address segment
+	xor %bx, %bx				# BX is offset within segment
+
+	# A few words about the algorithm:
+	# We read 0x10000 bytes (64 kB) and overflow BX (16 bytes register),
+	# then add 0x1000 to ES reg, after that compare with $ENDSEG
+	#
+	# If KERNSIZE != 0x10000 * N we read some unnecessary data, but
+	# i think it's not a problem
+repeat_read:
+	mov %es, %ax
+	cmp $ENDSEG, %ax
+	jae enable_a20				# Jump if AX >= $ENDSEG
+get_sects_for_read:
+	mov sectors, %ax			# AX = amount of sectors - current sector
+	sub csect, %ax				# AX has 6 significant bytes
+	mov %ax, %cx				# Calculate how many bytes we get by
+								# reading AX sectors
+	shl $9, %cx					# One sector = 2^9 = 512
+	add %bx, %cx				# CX = 0@@@.@@@0.0000.0000 + BX
+	jnc read_sects				# if not overflow, then jump
+	jz read_sects				# if CX = 0, then jump
+	xor %ax, %ax				# AX = 0
+	sub %bx, %ax				# AX = amount of sectors that we must
+	shr $9, %ax					# read for overflow BX
+read_sects:
+	call read_track				# INPUT: AX
+	mov %ax, %cx				# CX = amount of sectors that we read
+	add csect, %ax
+	cmp sectors, %ax			# Current sector = amount of sectors?
+	jne check_read				# If not equal, jump
+	mov chead, %ax
+	cmp heads, %ax				# Current head = amount of heads?
+	jne inc_chead				# If not equal, jump
+	movw $0xffff, chead			# Current head will overflow and equal 0
+								# after INC instuction in inc_chead
+	incw ctrack					# Go to next cylinder
+								# We don't check cylinder overflow
+								# because it makes no sense
+inc_chead:
+	incw chead
+	xor %ax, %ax
+check_read:
+	mov %ax, csect				# Calculate how many bytes we get by
+	shl $9, %cx					# reading AX sectors
+	add %cx, %bx				# Add it to BX
+	jnc repeat_read				# If BX not overflow, jjmp
+	mov %es, %ax
+	add $0x1000, %ax			# We read 0x10000 = 65536 bytes
+	mov %ax, %es
+	xor %bx, %bx
+	jmp repeat_read
+
+# INPUT:
+# AX - amount of sectors that we want to read
+read_track:
+	push %ax
+	push %bx
+	push %cx
+	push %dx
+	mov ctrack, %dx
+	mov csect, %cx				# Set sector
+	inc %cx						# Add +1 because sector has a base of 1
+	mov %dl, %ch				# Set cylinder
+	mov chead, %dh				# Set head
+	mov %dl, %dh
+	mov (0), %dl				# Set boot
+	mov $0x02, %ah				# Set BIOS read sector routine
+	int $0x13
+	jc .						# Error :(
+	pop %dx
+	pop %cx
+	pop %bx
+	pop %ax
+	ret
+
+enable_a20:
+	BIOS_PRINT $enable_a20_msg
+
+	cli							# Switch of interrupt until we have set
+								# up the protected mode interrupt vector
+
+	call wait_input
+	mov $READ_OUTP, %al
+	out %al, $0x64 
+	call wait_output
+
+	in $0x60, %al				# Read input buffer and store on stack
+	push %ax
+	call wait_input
+
+	mov $WRITE_OUTP, %al
+	out %al, $0x64
+	call wait_input
+
+	pop %ax						# Pop the output port data from stack
+	or $2, %al					# Set bit 1 (A20) to enable
+	out %al, $0x60				# Write the data to the output port
+	call wait_input
+
+switch_to_pm:
+	BIOS_PRINT $boot_prot_mode_msg
+	lgdt gdt_descriptor			# Load our global descriptor table
+
+	mov %cr0, %eax				# Set the first bit of CR0
+	or $0x01, %eax				# to make the switch to protected mode
+	mov %eax, %cr0
+
+	# Make a far jump to our 32-bit code.
+	# This also forces the CPU to flush its cache of pre-fetched
+	# and real-mode decoded instructions, which can cause problems
+	jmp $CODESEG, $KERNADDR
+
+disk_error:
+	BIOS_PRINT $disk_error_msg
+	jmp .
+
+wait_input:
+	in $0x64, %al				# Read status
+	test $2, %al				# Is input buffer full?
+	jnz wait_input				# yes - continue waiting
+	ret
+
+wait_output:
+	in $0x64, %al
+	test $1, %al				# Is output buffer full?
+	jz wait_output				# no - continue waiting
+	ret
+
+# Global Descriptor Table (contains 8-byte entries)
+gdt_start:
+gdt_null:						# The mandatory null descriptor
+	.quad 0x0
+
+gdt_code:						# The code segment descriptor
+	# Base = 0x0, limit = 0xfffff
+	# 1st flags: (present)1 (privilege)00 (descriptor type)1 -> b1001
+	# Type flags: (code)1 (conforming)0 (readable)1 (accessed)0 -> b1010
+	# 2nd flags: (granularity)1 (size)1 (64-bit seg)0 (AVL)0 -> b1100
+	.word 0xffff				# Limit (bits 0-15)
+	.word 0x0					# Base (bits 0-15)
+	.byte 0x0					# Base (bits 16-23)
+	.byte 0b10011010			# 1st flags, type flags
+	.byte 0b11001111			# 2nd flags, limit (bits 16-19)
+	.byte 0x0					# Base (bits 24-31)
+
+gdt_data: 						# the data segment descriptor
+	# Same as code segment except for the type flags:
+	# Type flags: (code)0 (direction)0 (writable)1, (accessed)0 -> b0010
+	# P.S: direction bit: 0 the segment grows up
+	.word 0xffff				# Limit (bits 0-15)
+	.word 0x0					# Base (bits 0-15)
+	.byte 0x0					# Base (bits 16-23)
+	.byte 0b10010010			# 1st flags, type flags
+	.byte 0b11001111			# 2nd flags, limit (bits 16-19)
+	.byte 0x0					# Base (bits 24-31)
+gdt_end:
+
+# Global variables
+
+# Total amount of HDD components:
+heads:							# 8 significant bytes
+	.word 0x0
+sectors:						# 6 significant bytes
+	.word 0x0
+
+# The number of the current component with which we interact:
+ctrack:							# track/cylinder
+	.word 0x0
+chead:
+	.word 0x0
+csect:
+	.word 1 + SETUPLEN
+
+gdt_descriptor:
+	# The 6-byte GDT structure containing:
+	# - GDT size, 2 bytes (size always less one of the real size):
+	.word gdt_end - gdt_start - 1
+	# - GDT address, 4 bytes:
+	.word gdt_start, 0x9
+
+get_data_msg:
+	.asciz "Getting the system data from the BIOS\r\n"
+
+boot_prot_mode_msg:
+	.asciz "Entering 32-bit protected mode\r\n"
+
+boot_load_kern_msg:
+	.asciz "Loading kernel into memory\r\n"
+
+enable_a20_msg:
+	.asciz "Enabling A20 line\r\n"
+
+disk_error_msg:
+	.asciz "Disk read error!"
+
+.space (512 * SETUPLEN) - (. - _start), 0