increased size of stage 2 bootloader by 1024 bytes

8 files changed, 36 insertions, 25 deletions

diff --git a/README b/README
index 38574df..c6263fe 100644
--- a/README
+++ b/README
@@ -14,7 +14,7 @@ ndisasm -b16 -o7c00h -a image.bin | less
 objdump -M intel -d kernel.o | less
 
 gcc -m32 -ffreestanding -c -o kernel.o kernel.c
-ld -o kernel.bin -Ttext 0x8400 kernel.o -m elf_i386 --oformat binary
+ld -o kernel.bin -Ttext 0x8800 kernel.o -m elf_i386 --oformat binary
 objdump -M intel -d kernel.bin | less
 
 # oformat: objdump -i lists tons of formats
@@ -38,10 +38,10 @@ Next at t=14040244
 (0) [0x000000007c00] 0000:7c00 (unk. ctxt): mov ax, 0x0000            ; b80000
 
 C entry:
-break 0x8400
+break 0x8800
 
 disassemble kernel in 32-bit mode
-ndisasm -b32 -o8400h -a kernel.bin | less
+ndisasm -b32 -o8800h -a kernel.bin | less
 
 With qemu remote (see http://wiki.osdev.org/Kernel_Debugging):
 
diff --git a/src/Makefile b/src/Makefile
index d32d3c1..6689169 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -10,12 +10,12 @@ MAGIC := $(shell printf '%x' `date +%s`)
 all: image.bin kernel.sym
 
 # truncate to correct number of sectors, we have
-# 512 (boot, stage 1) + N * 512 (N currenty is 3, stage 2) = 3072 for boot.bin
-# + M * 512 (M is currently 7) = 3144 for kernel.bin
+# 512 (boot, stage 1) + N * 512 (N currenty is 5, stage 2) = 3072 for boot.bin
+# + M * 512 (M is currently 39) = 19968 for kernel.bin
 # + 1 * 512 = 512 for magic.bin
 # (M + N + 1 is the number of sectors to be read in stage 2, as stage 1
-# loads only the first sector, and stage 1 loads 3 sectors of stage 2,
-# adapt NOF_LOAD_SECTORS to 44)
+# loads only the first sector, and stage 1 loads 5 sectors of stage 2,
+# adapt NOF_LOAD_SECTORS to 42)
 # then we make sure the image has the size of a 1.44 MB floppy
 # (emulators like qemu do some guess work for CHS resolution based
 # on the size of the image)
@@ -35,7 +35,7 @@ kernel.sym: kernel.elf
 	$(OBJCOPY) --only-keep-debug kernel.elf kernel.sym
 
 kernel.elf: kernel/kernel.o kernel/kernel_asm.o kernel/console.o kernel/vgatext.o kernel/serial.o hardware/port.o hardware/port_asm.o hardware/interrupts.o hardware/interrupts_asm.o hardware/pci.o drivers/driver.o drivers/hdi/ps2/keyboard.o drivers/hdi/ps2/mouse.o drivers/video/vga.o libc/string.o libc/stdlib.o libc/stdio.o libc/setjmp.o
-	$(LD) -o kernel.elf -N -n -Ttext 0x8400 --oformat elf32-i386 \
+	$(LD) -o kernel.elf -N -n -Ttext 0x8800 --oformat elf32-i386 \
 		kernel/kernel.o kernel/kernel_asm.o \
 		kernel/console.o kernel/vgatext.o kernel/serial.o \
 		hardware/port.o hardware/port_asm.o \
diff --git a/src/README b/src/README
index c1f1577..905399b 100644
--- a/src/README
+++ b/src/README
@@ -5,7 +5,7 @@ Simple bootloader, loading in two phases and loading the kernel itself
 
 * boot.bin - boot sector (stage 1 and 2, total 2k), offset 0x7c00
   * boot.asm - the main boot sector code using:
-* kernel.bin - linked kernel with fix start offset 0x8400
+* kernel.bin - linked kernel with fix start offset 0x8800
   * boot_gdt.asm - the early GDT, flat memory model, no protection
   * stage1_functions.asm - real mode functions of the bootloader
   * stage2_functions.asm - protected mode primitive VGA routines
diff --git a/src/boot/boot.asm b/src/boot/boot.asm
index c3cb57e..75ad05e 100644
--- a/src/boot/boot.asm
+++ b/src/boot/boot.asm
@@ -106,7 +106,7 @@ stage2:
 	call print_string
 
 
-; load kernel to 0x8400 (directly  after stage 2
+; load kernel to 0x8800 (directly  after stage 2
 ; of the boot loader)	
 	mov dl, [BOOT_DRIVE]
 	call read_from_disk
@@ -220,8 +220,11 @@ MESSAGE_HALTED:
 %include "boot/stage2_check_magic.asm"
 
 ; make sure we have full sectors, stage 1 is 512 bytes, so we
-; have to will up 3 sectors
-times 2048-($-$$) db 0
+; have to will up 5 sectors (gives 6 in total for stage 1 and 2)
+times 3070-($-$$) db 0
 
-; position is 0x8400 now for the C entry
+; magic number of stage 2
+dw 0xAABB
+
+; position is 0x8800 now for the C entry
 kernel_main:
diff --git a/src/boot/stage1_functions.asm b/src/boot/stage1_functions.asm
index bdb2aac..f1d229b 100644
--- a/src/boot/stage1_functions.asm
+++ b/src/boot/stage1_functions.asm
@@ -1,3 +1,6 @@
+; NOF_SECTORS_STAGE2
+NOF_SECTORS_STAGE2 equ 5
+
 ; IN dx: hex value to print	
 print_hex:
 	push bx
@@ -88,7 +91,7 @@ current_row:
 read_stage2_from_disk:
 	mov ah, 0x02			; read sectors from drive
 	
-	mov al, 3			; read 3 sectors of stage 2
+	mov al, NOF_SECTORS_STAGE2	; read sectors of stage 2
 	mov ch, 0			; select first cylinder
 	mov dh, 0			; first head
 	mov cl, 2			; second sector after boot sector
@@ -101,7 +104,7 @@ read_stage2_from_disk:
 	
 	jc .read_error
 	
-	cmp al, 3			; 3 sectors read?
+	cmp al, NOF_SECTORS_STAGE2	; correct number of sectors read?
 	jne .short_read			; if not, short read
 	
 	ret
diff --git a/src/boot/stage2_check_magic.asm b/src/boot/stage2_check_magic.asm
index 1deaf05..7339a89 100644
--- a/src/boot/stage2_check_magic.asm
+++ b/src/boot/stage2_check_magic.asm
@@ -8,7 +8,7 @@ check_magic:
 	push edi
 	mov eax, NOF_LOAD_SECTORS	; number of 512-byte sectors
 	shl eax, 9			; 512 bytes per sector
-	mov edx, 0x8400			; offset of kernel
+	mov edx, 0x8800			; offset of kernel
 	add edx, eax
 	sub edx, MAGICLEN		; subtract the length of the magic string
 	mov esi, edx			; now use edx as first string address to compare to
@@ -20,12 +20,16 @@ check_magic:
 .ok:
 	mov si, MAGIC_OK_MSG
 	call pm_print_string
+	mov edx, esi
+	call pm_print_hex
 	call pm_print_newline
 	xor eax, eax
 	jmp .end
 .mismatch:
 	mov si, MAGIC_NOT_OK_MSG
 	call pm_print_string
+	mov edx, esi
+	call pm_print_hex
 	call pm_print_newline
 	xor eax, eax
 	mov eax, 1
@@ -42,7 +46,7 @@ db "ABAOS", %[MAGIC], 0
 MAGICLEN equ $ - COMPARE_MAGIC
 
 MAGIC_NOT_OK_MSG:
-db "Magic signature found", 0
+db "Magic signature found at ", 0
 
 MAGIC_OK_MSG:
-db "Magic signature not found!", 0
+db "Magic signature not found at ", 0
diff --git a/src/boot/stage2_real_functions.asm b/src/boot/stage2_real_functions.asm
index 87642c2..84713d5 100644
--- a/src/boot/stage2_real_functions.asm
+++ b/src/boot/stage2_real_functions.asm
@@ -1,8 +1,8 @@
 ; number of sectors to be read for the kernel itself
 ; (note: the first sector gets loaded by the BIOS, the
-; next 3 sectors are read by the simple stage 1 loader,
-; so subtract 3 here!)
-NOF_LOAD_SECTORS equ 44
+; next 5 sectors are read by the simple stage 1 loader,
+; so subtract 5 here!)
+NOF_LOAD_SECTORS equ 42
 
 ; data sections used for reading the kernel from disk
 SECTORS_PER_CYLINDER:
@@ -13,7 +13,7 @@ NOF_HEADS:
 SECTORS_TO_LOAD:
 	db NOF_LOAD_SECTORS		; load NOF_LOAD_SECTORS sectors in total
 CURRENT_SECTOR:
-	db 5				; first sector after stage 2
+	db 7				; first sector after stage 2
 CURRENT_CYLINDER:
 	db 0
 CURRENT_HEAD:
@@ -90,7 +90,7 @@ read_from_disk:
 
 	mov bx, 0			; where to store the data
 	mov es, bx
-	mov bx, 0x8400			; 2'048 bytes after first sector
+	mov bx, 0x8800			; 3072 bytes after first sector
 
 .read_next_sector:
 
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index d74e031..9557745 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -31,7 +31,7 @@ static bool terminate = false;
 // also elimiate all the object allocated on the stack in kernel_main
 static driver_manager_t *global_driver_manager;
 
-// must be first entry in kernel.bin (0x8400) as stage 2 of
+// must be first entry in kernel.bin (0x8800) as stage 2 of
 // the boot loader expects the entry point to be here!
 void kernel_main( void )
 {	
@@ -51,7 +51,8 @@ void kernel_main( void )
 	// initialize the early console of the kernel
 	stdio_set_console( &console );
 	puts( "Started early kernel console" );
-	printf( "Kernel code and data is at 0x%X, kernel stack at 0x%X\n", 0x8400, 0x90000 );
+	// TODO: get those values somehow from the boot loader
+	printf( "Kernel code and data is at 0x%X, kernel stack at 0x%X\n", 0x8800, 0x90000 );
 
 	// exit point in case of kernel panic, do this as soon as
 	// possible, as soon we have an early console we can croak on