Remove END

apm_shutdown.S

@@ -25,5 +25,3 @@ mov $0x5307, %ax
 mov $0x0001, %bx
 mov $0x0003, %cx
 int $0x15
-
-END

apm_shutdown2.S

@@ -66,5 +66,3 @@ jc APM_error            #if the carry flag is set there was an error
 
 APM_error:
 hlt
-
-END

bibliography.md

@@ -70,3 +70,7 @@ For when we decide to port this tutorial:
 ARM:
 
 - <https://github.com/bravegnu/gnu-eprog>
+
+Raspberry PI:
+
+- <https://github.com/dwelch67/raspberrypi>

bios_background.S

@@ -8,4 +8,3 @@ int $0x10
 PUTC($0x61)
 
 hlt
-END

bios_carriage_return.S

@@ -13,6 +13,5 @@ Carriage returns are needed just like in old days.
 BEGIN
     PRINT($msg)
     hlt
-END
 msg:
     .asciz "hello\n\rworld"

bios_clear_screen.S

@@ -33,4 +33,3 @@ CURSOR_POSITION(0, 0)
 PUTC($0x62)
 
 hlt
-END

bios_color.S

@@ -29,4 +29,3 @@ PUTC($0x62)
 PUTC($0x63)
 
 hlt
-END

bios_cursor_position.S

@@ -18,4 +18,3 @@ int $0x10
 PUTC($0x63)
 
 hlt
-END

bios_disk_load.S

@@ -15,15 +15,12 @@ Bibliography:
 
 - http://wiki.osdev.org/ATA_in_x86_RealMode_%28BIOS%29
 - https://en.wikipedia.org/wiki/INT_13H
+- https://thiscouldbebetter.wordpress.com/2011/03/15/creating-a-bootable-program-in-assembly-language/
 
 TODO answer:
 
-- https://thiscouldbebetter.wordpress.com/2011/03/15/creating-a-bootable-program-in-assembly-language/
-- http://stackoverflow.com/questions/7716427/loading-2nd-stage-of-bootloader-and-starting-it
-- http://stackoverflow.com/questions/2065370/how-to-load-second-stage-boot-loader-from-first-stage
 - http://stackoverflow.com/questions/19381434/cannot-read-disk-sectors-in-assembly-language
 - http://stackoverflow.com/questions/15497842/read-a-sector-from-hard-drive-with-int-13h
-- http://stackoverflow.com/questions/9899577/example-for-int-13-ah-03h-interupt-assembly
 */
 
 #include "common.h"
@@ -44,7 +41,13 @@ BEGIN
     mov $2, %ah
     /* Number of sectors to read. */
     mov $1, %al
-    /* Drive number. Starts at 0x80, second one is 0x81. TODO why not from 0? */
+    /*
+    Drive number. Starts at 0x80, second one is 0x81. TODO why not from 0?
+
+    The BIOS stores the right number on dl as an initial state,
+    but we may be destroying it before, and are lazy to properly store it somewhere.
+    http://stackoverflow.com/a/19387093/895245
+    */
     mov $0x80, %dl
     /* cylinder number */
     mov $0, %ch
@@ -73,5 +76,4 @@ stage2:
     but let's just put it here to keep our other images smaller.
     */
     .org 512
-END
 

bios_hello_world.S

@@ -12,4 +12,3 @@ halt:
     hlt
 msg:
     .asciz "hello world"
-END

bios_keyboard.S

@@ -8,4 +8,3 @@ mov $0x00, %ah
 int $0x16
 PUTC(%al)
 hlt
-END

bios_keyboard_loop.S

@@ -11,4 +11,3 @@ start:
     int $0x16
     PUTC(%al)
     jmp start
-END

bios_newline.S

@@ -13,6 +13,5 @@ Carriage returns are needed just like in old days.
 BEGIN
     PRINT($msg)
     hlt
-END
 msg:
     .asciz "hello\nworld"

bios_one_char.S

@@ -13,4 +13,3 @@ BEGIN
 mov $0x0E40, %ax
 int $0x10
 hlt
-END

bios_pixel.S

@@ -49,4 +49,3 @@ start:
     jmp start
 end:
     hlt
-END

bios_pixel_line.S

@@ -19,4 +19,3 @@ start:
     jmp start
 end:
     hlt
-END

bios_scroll.S

@@ -62,6 +62,5 @@ mov $0x0202, %dx
 int $0x10
 
 hlt
-END
 stair:
     .asciz "a\nb\nc\nd"

common.h

@@ -19,8 +19,6 @@ The big ones do bloat the executable.
     /* We should set SP because BIOS calls may depend on that. TODO confirm. */ \
     mov %bp, %sp
 
-#define END
-
 #define CURSOR_POSITION(x, y) \
     mov $0x02, %ah;\
     mov $0x00, %bh;\

in_beep.S

@@ -62,4 +62,3 @@ loop:
 	in $0x61, %al
     mov $0x00, %al
     out %al, $0x61
-END

in_beep_illinois.S

@@ -45,4 +45,3 @@ start:
     out %al, $0x61
 
     jmp start
-END

in_keyboard.S

@@ -33,4 +33,3 @@ loop:
     PRINT_HEX(%al)
     PRINT_NEWLINE
     jmp loop
-END

in_mouse.S

@@ -12,4 +12,3 @@ I am so going to make a pixel drawing program with this.
 #include "common.h"
 BEGIN
 hlt
-END

in_pit.S

@@ -115,4 +115,3 @@ handler:
     iret
 
     /* TODO turn off. */
-END

in_rtc.S

@@ -89,4 +89,3 @@ update_in_progress:
     PRINT_NEWLINE
 
     jmp update_in_progress
-END

infinite_loop.S

@@ -8,4 +8,3 @@ It likely wastes more energy? But is less prone to being interrupted than `hlt`.
 BEGIN
 loop:
 jmp loop
-END

initial_state.S

@@ -0,0 +1,40 @@
+/*
+Check the initial state the firmware leaves us in.
+
+Could be done with GDB on the emulator, but this will also work on real hardware.
+*/
+
+#include "common.h"
+
+#define INITIAL_STORE(x) mov % ## x, x
+
+#define INITIAL_DATA(x) \
+    x: .word 0;\
+    x ## s: .ascii #x " = \0"
+
+#define INITIAL_PRINT(x) \
+    PRINT($x ## s);\
+    PRINT_HEX(x);\
+    PRINT_NEWLINE
+
+BEGIN
+
+INITIAL_STORE(ax)
+INITIAL_STORE(bx)
+INITIAL_STORE(cx)
+INITIAL_STORE(dx)
+INITIAL_STORE(cs)
+
+INITIAL_PRINT(ax)
+INITIAL_PRINT(bx)
+INITIAL_PRINT(cx)
+INITIAL_PRINT(dx)
+INITIAL_PRINT(cs)
+
+hlt
+
+INITIAL_DATA(ax)
+INITIAL_DATA(bx)
+INITIAL_DATA(cx)
+INITIAL_DATA(dx)
+INITIAL_DATA(cs)

interrupt.S

@@ -39,4 +39,3 @@ handler:
     iret
 end:
     hlt
-END

interrupt_keyboard.S

@@ -18,4 +18,3 @@ handler:
     PUTC($0x61)
     iret
 jmp loop
-END

interrupt_loop.S

@@ -10,4 +10,3 @@ BEGIN
 handler:
     PUTC($0x61)
     int $0
-END

interrupt_zero_divide.S

@@ -14,4 +14,3 @@ handler:
     PUTC($0x61)
 fail:
     hlt
-END

min.S

@@ -21,4 +21,4 @@ xor %ax, %ax
 mov %ax, %ds
 
 /* Stop the processor. */
-hlt
+ret

nasm/Makefile

@@ -1,18 +1,29 @@
 .POSIX:
 
-BASENAME ?= bios_hello_world
+RUN ?= bios_hello_world
 IN_EXT ?= .asm
 OUT_EXT ?= .img
 
-OUT := $(BASENAME)$(OUT_EXT)
+OUTS := $(patsubst %$(IN_EXT),%$(OUT_EXT),$(wildcard *$(IN_EXT)))
+RUN_FILE := $(RUN)$(OUT_EXT)
 
 .PHONY: clean run
 
-$(OUT): $(BASENAME)$(IN_EXT)
+all: $(OUTS)
+
+%$(OUT_EXT): %$(IN_EXT)
 	nasm -f bin -o '$@' '$<'
 
 clean:
-	rm -f '$(OUT)'
+	rm -f *'$(OUT_EXT)'
 
-run: $(OUT)
-	qemu-system-i386 '$(OUT)'
+run: all
+	qemu-system-i386 '$(RUN_FILE)'
+
+bochs: all
+	CYLINDERS="$$(($$(stat -c '%s' '$(RUN_FILE)') / 512))" && \
+	bochs -qf /dev/null \
+		'ata0-master: type=disk, path="$(RUN_FILE)", mode=flat, cylinders='"$$CYLINDERS"', heads=1, spt=1' \
+		'boot: disk' \
+		'display_library: sdl' \
+		'megs: 128'

nasm/bios_disk_load.asm

@@ -0,0 +1,36 @@
+use16
+org 0x7C00
+
+    ; Load stage 2 to memory.
+    mov ah, 0x02
+    mov al, 1
+    mov dl, 0x80
+    mov ch, 0
+    mov dh, 0
+    mov cl, 2
+    mov bx, stage2
+    int 0x13
+
+    jmp stage2
+
+    times ((0x200 - 2) - ($ - $$)) db 0x00
+    dw 0xAA55
+
+stage2:
+
+    mov si, msg
+    mov ah, 0x0E
+for_each_char:
+    lodsb
+    cmp al, 0x00
+    je end_for_each_char
+    int 0x10
+    jmp for_each_char
+end_for_each_char:
+
+    cli
+    hlt
+
+    msg: db 'second stage', 0
+
+    times ((0x400) - ($ - $$)) db 0x00

nasm/bios_hello_world.asm

@@ -1,6 +1,8 @@
 ; Adapted from: http://blog.ackx.net/asm-hello-world-bootloader.html
     org 0x7c00
     bits 16
+    xor ax, ax
+    mov ds, ax
 start:
     cli
     mov si, msg

nasm/protected_mode.asm

@@ -0,0 +1,138 @@
+; 2-stage protected mode entry.
+;
+; Initially taken from:
+; https://thiscouldbebetter.wordpress.com/2011/03/17/entering-protected-mode-from-assembly/
+
+use16
+org 0x7C00 ; boot sector address
+
+Boot:
+	;
+	mov ah,0x00	; reset disk
+	mov dl,0	; drive number
+	int 0x13
+	;
+	mov ah,0x02	; read sectors into memory
+	mov al,0x10	; number of sectors to read (16)
+	mov dl,0x80	; drive number
+	mov ch,0	; cylinder number
+	mov dh,0	; head number
+	mov cl,2	; starting sector number
+	mov bx,Main	; address to load to
+	int 0x13	; call the interrupt routine
+	;
+	jmp Main
+	;
+
+PreviousLabel:
+
+PadOutWithZeroesSectorOne:
+	times ((0x200 - 2) - ($ - $$)) db 0x00
+
+BootSectorSignature:
+	dw 0xAA55
+
+;===========================================
+
+Main:
+	;
+	; set the display to VGA text mode now
+	; because interrupts must be disabled
+	;
+	mov ax,3
+	int 0x10    ; set VGA text mode 3
+	;
+	; set up data for entering protected mode
+	;
+        xor edx,edx ; edx = 0
+        mov dx,ds   ; get the data segment
+        shl edx,4   ; shift it left a nibble
+        add [GlobalDescriptorTable+2],edx ; GDT's base addr = edx
+	;
+        lgdt [GlobalDescriptorTable] ; load the GDT  
+        mov eax,cr0 ; eax = machine status word (MSW)
+        or al,1     ; set the protection enable bit of the MSW to 1
+	;
+        cli         ; disable interrupts
+        mov cr0,eax ; start protected mode
+	;
+        mov bx,0x08 ; the size of a GDT descriptor is 8 bytes
+        mov fs,bx   ; fs = the 2nd GDT descriptor, a 4 GB data seg
+	;
+	; write a status message
+	;
+	mov ebx,0xB8000 ; address of first char for VGA mode 3
+	;
+	mov si,TextProtectedMode ; si = message text
+	;
+	ForEachChar:
+		;
+		lodsb		; get next char	
+		cmp al,0x00	; if it's null, break 	
+		je EndForEachChar
+		;
+		mov [fs:ebx],al	; write char to display memory
+		;
+		inc ebx		; 2 bytes per char
+		inc ebx		; so increment twice
+		;
+	jmp ForEachChar
+	EndForEachChar:
+	;
+	LoopForever: jmp LoopForever
+	;
+	ret
+	;
+	TextProtectedMode: db 'The processor is in protected mode.',0
+
+GlobalDescriptorTable:   
+
+	; the global descriptor table is the heart of protected mode
+	; entries are used to map virtual to physical memory
+	; among other things
+	;
+	; each descriptor contains 8 bytes, "organized" as follows:
+	;
+	; |----------------------2 bytes--------------------|
+	;
+	; +-------------------------------------------------+
+	; | segment address 24-31  | flags #2  | len 16-19  | +6
+	; +-------------------------------------------------+
+	; | flags #1               | segment address 16-23  | +4
+	; +-------------------------------------------------+
+	; | segment address bits 0-15                       | +2
+	; +-------------------------------------------------+
+	; | segment length bits 0-15                        | +0
+	; +-------------------------------------------------+
+
+	; the high-order bit of flags #2 controls "granularity"
+	; setting it to 1 multiplies the segment length by 4096
+
+	;======================================================
+
+	; create two descriptors:
+	; one for the GDT itself, plus a 4 gibabyte data segment
+
+	dw GlobalDescriptorTableEnd - GlobalDescriptorTable - 1 
+	; segment address bits 0-15, 16-23
+	dw GlobalDescriptorTable 
+	db 0	
+	; flags 1, segment length 16-19 + flags 2
+	db 0, 0
+	; segment address bits 24-31
+	db 0 
+
+	; a data segment based at address 0, 4 gibabytes long
+	; 
+        dw 0xFFFF 	; segment length 0-15
+	db 0, 0, 0 	; segment address 0-15, 16-23
+	db 0x91 	; flags 1
+	db 0xCF 	; flags 2, segment length 16-19
+	db 0		; segment address 24-31
+	;
+GlobalDescriptorTableEnd:
+
+;===========================================
+
+PadOutWithZeroesSectorsAll:
+	times (0x2000 - ($ - $$)) db 0x00

protected_mode.S

@@ -5,9 +5,9 @@ TODO get working.
 
 - http://wiki.osdev.org/Journey_To_The_Protected_Land
 - http://wiki.osdev.org/Protected_Mode
-- http://stackoverflow.com/questions/28645439/how-do-i-enter-32-bit-protected-mode-in-nasm-assembly
 - https://github.com/chrisdew/xv6/blob/master/bootasm.S
 - https://thiscouldbebetter.wordpress.com/2011/03/17/entering-protected-mode-from-assembly/ FASM based. Did not word on first try, but looks real clean.
+- http://stackoverflow.com/questions/28645439/how-do-i-enter-32-bit-protected-mode-in-nasm-assembly
 
 ## GDT
 
@@ -61,4 +61,3 @@ cli
     gdt:
     .word 0x1234
     .long 0x12345678
-END

reboot.S

@@ -9,4 +9,3 @@ TODO why does it work?
 #include "common.h"
 BEGIN
 ljmpw $0xF000, $0XFFF0
-END

segment_registers_real_mode.S

@@ -110,4 +110,3 @@ msg:
     /* We push the correct A forward 16 bytes in memory to compensate for the segments. */
     .fill 0x10
     .byte 'A'
-END

ss.S

@@ -8,4 +8,3 @@ SS register. I think the major effect of it is that anything that uses
 #include "common.h"
 BEGIN
 hlt
-END

template.S

@@ -5,4 +5,3 @@
 #include "common.h"
 BEGIN
 hlt
-END