linux下bochs创建最简单的OS(一)

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我的系统为redhat9
首先去bochs的官网
http://bochs.sourceforge.net/
下载最新的程序，我直接下的是bochs-2.4.tar.gz
tar zxvf bochs-2.4.tar.gz
./configure
如果要调试功能的话，可查看configure文件做相应调整
 --enable-debugger                 compile in support for Bochs internal debugger
  --enable-disasm                   compile in support for disassembler
  --enable-debugger-gui             compile in support for Bochs internal debugger GUI
  --with-sdl                        use SDL libraries
网上说要加最后一个暂时没有明白其意。
make
./bochs  运行

BOCHS运行需要.bochsrc文件,在LINUX下以.开头的文件都是隐藏文件
l. 可查看这些文件。
vi .bochsrc
# how much memory the emulated machine will have
megs: 32

# filename of ROM images
romimage:file=$BXSHARE/BIOS-bochs-latest
#注意上面这一行，2.3.5以后的后面不能加,address=0xf0000  否则会出现
#Message: ROM: System BIOS must end at 0xfffff 错误的  这个后面会解释
#romimage: file=mybios.bin, address=0xfff80000 # 512k at memory top

vgaromimage: file=$BXSHARE/VGABIOS-lgpl-latest
                                                                               
# what disk images will be used
floppya: 1_44=hello.img, status=inserted

#ata0-master: type=disk, mode=flat, path="30M.sample"

# hard disk
#ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
#ata1: enabled=1, ioaddr1=0x170, ioaddr2=0x370, irq=15
#ata2: enabled=0, ioaddr1=0x1e8, ioaddr2=0x3e0, irq=11
#ata3: enabled=0, ioaddr1=0x168, ioaddr2=0x360, irq=9

boot: floppy
#boot: disk

megs: 32 是说内存是32M
floppya: 1_44=a.img, status=inserted 指定了软盘映像文件
boot: floppy 从软盘启动。

从http://bochs.sourceforge.net/下载nasm
我下的是nasm-2.05.01.tar.gz 
tar zxvf nasm-2.05.01.tar.gz
cd nasm-2.05.01
./configure
make
make install

mkdir helloworld
cd helloworld
vi hello.asm
;hello.asm
org 07c00h
                                                                               
LABEL_START:
        mov ax,cs
        mov ds,ax
        mov es,ax
        mov ax,0b800h
        mov gs,ax
        mov ah,0ch
        mov al,'H'
        mov [gs:0],ax
        jmp $

./nasm ./helloworld/hello.asm  -o ./helloworld/hello.bin

进入bochs目录
./bximage
========================================================================
                                bximage
                  Disk Image Creation Tool for Bochs
        $Id: bximage.c,v 1.34 2009/04/14 09:45:22 sshwarts Exp $
========================================================================
 
Do you want to create a floppy disk image or a hard disk image?
Please type hd or fd. [hd] fd
 
Choose the size of floppy disk image to create, in megabytes.
Please type 0.16, 0.18, 0.32, 0.36, 0.72, 1.2, 1.44, 1.68, 1.72, or 2.88.
 [1.44]
I will create a floppy image with
  cyl=80
  heads=2
  sectors per track=18
  total sectors=2880
  total bytes=1474560
 
What should I name the image?
[a.img] hello.img
 
Writing: [] Done.
 
I wrote 1474560 bytes to hello.img.
 
The following line should appear in your bochsrc:
  floppya: image="hello.img", status=inserted

把bin写入img中
dd if=/nasm-2.05.01/helloworld/hello.bin of=hello.img bs=512 count=1 conv=notrunc
读入了 0+1 个块
输出了 0+1 个块

bochs -q -f .bochsrc 运行我们的OS
出现如下错误
Bochs is exiting with the following message:
[BIOS ] No bootable device.

查看生成的hello.bin大小
ls -al hello.bin
-rw-r--r--    1 root     900            22  5月 20 11:45 hello.bin
大小为22byte
我们要把它们弄成512byte的
在hello.asm最后添加
times 510-($-$$) db 0 ; 填充剩下的空间，使生成的二进制代码恰好为512字节
dw        0xaa55      ;这个是结束标志符
再用nasm编译生成hello.bin
再写入到hello.img便可以了。
然后执行
bochs -q -f .bochsrc
便可以看到红色的H字样了

ps:
若出现Message: ROM: System BIOS must end at 0xfffff 错误的原因如下：
In previous versions of Bochs the BIOS size was 64k and you always had to
specify the start address at 0xf0000. Starting with release 2.2.5 Bochs
supports BIOS images up to 512k and it's no longer necessary to specify the
start address if the BIOS ends at memory top
就是不要再指定address了。

当然要显示Hello world可用以下这个
org 07c00h
mov        ax, cs;数据传送指令，将代码段寄存器cs的内容赋给通用寄存器ax
mov        ds, ax;使数据段与代码段在同一个段
mov        es, ax;使附加段与代码段在同一个段
call        DispStr
jmp        $ ;$表示当前地址,无限循环
DispStr:
mov        ax, BootMessage
mov        bp, ax ;es:bp=串地址
mov        cx, 15 ;串长度
mov        ax, 01301h  ;ah=13h, al=01h 视频中断13h号功能：写字符串；AL=01H，表示写完字符串后，更新光标位置
mov        bx, 000ch   ;页号为0(bh=0) 黑底红字(bl=0ch,高亮)
mov        dl, 0 ;DH、DL=写串的光标位置，DH=行号，DL=列号
int        10h
ret
BootMessage:        db "Hello,World OS!"
times 510-($-$$) db 0 ; 填充剩下的空间，使生成的二进制代码恰好为512字节
dw        0xaa55

times 510-($-$$) db 0
This reads: Times 510-(Start of this Instruction - Start of program) with 0's
$ stands for start of the instruction
$$ stands for start of the program
dw 0xAA55

For some reason the signature has to be written this way round!
This fills the last to bytes of the boot loader with 55AA (this is a hex number)
Without this signature the BIOS won't recognise this as a bootable disk!