写操作系统----1.bochs调试的环境搭建

1. ubuntu下bochs源码编译安装
用apt-get install 安装的bochs是不带调试功能的，所以需要源码重新编译安装bochs
1.1 源码编译

cong@msi:/work/os/bochs-2.6.8$ mkdir install           -->将install后的bochs放在这个目录下
cong@msi:/work/os/bochs-2.6.8$ ./configure --prefix=`pwd`/install --enable-debugger --enable-disasm   -->配置成可调试
cong@msi:/work/os/bochs-2.6.8$ make -j16 && make install
cong@msi:/work/os/bochs-2.6.8$ ls install
bin  share

cong@msi:/work/os/bochs-2.6.8$ cd install/bin/
cong@msi:/work/os/bochs-2.6.8/install/bin$ ls          -->编译安装完成后会在install目录下生成bochs及bximage这两个文件
bochs   bximage

1.2 配置bochsrc文件

cong@msi:/work/os/bochs-2.6.8/install/bin$ cp -arf ../share/doc/bochs/bochsrc-sample.txt .
cong@msi:/work/os/bochs-2.6.8/install/bin$ diff ./bochsrc bochsrc-sample.txt
186,187c186
< #cpu: model=core2_penryn_t9600, count=1, ips=50000000, reset_on_triple_fault=1, ignore_bad_msrs=1, msrs="msrs.def"
< cpu: model=pentium, count=1, ips=50000000, reset_on_triple_fault=1, ignore_bad_msrs=1, msrs="msrs.def"
---
> cpu: model=core2_penryn_t9600, count=1, ips=50000000, reset_on_triple_fault=1, ignore_bad_msrs=1, msrs="msrs.def"
715,716c714
< #ata0-master: type=disk, mode=flat, path="30M.sample"
< ata0-master: type=disk, mode=flat, path="/work/os/code/disk.img"
---
> ata0-master: type=disk, mode=flat, path="30M.sample"
909c907
< #sound: driver=default, waveout=/dev/dsp. wavein=, midiout=
---
> sound: driver=default, waveout=/dev/dsp. wavein=, midiout=
920c918
< #speaker: enabled=1, mode=sound
---
> speaker: enabled=1, mode=sound

注意: 上面硬盘的路径固定放在/work/os/code/disk.img下
1.3 配置脚本运行bochs

cong@msi:/work/os/bochs-2.6.8/install/bin$ cd /usr/local/bin/
cong@msi:/usr/local/bin$
cong@msi:/usr/local/bin$ cat bochs
#!/bin/sh
/work/os/bochs-2.6.8/install/bin/bochs -f /work/os/bochs-2.6.8/install/bin/bochsrc

注意: 上面bochs的启动脚本也是固定路径，所以这些东东配置完成后就不能够再改路径了

---

2. 测试
2.1 测试程序

cong@msi:/work/os/code/1mbr$ cat mbr.S     --> 只有4行
org 0x7C00
    jmp $
times 510-($-$$) db 0
dw 0xaa55
; dw 0x55aa

2.2 Makefile

cong@msi:/work/os/code/1mbr$ cat Makefile
mbr:
    nasm mbr.S -o mbr.bin
flash:
    -rm ../disk.img                        -->前面加-的作用是如果disk.img不存在,rm执行出错也不会影响下面的操作
    dd if=/dev/zero of=../disk.img bs=1M count=30
    dd if=./mbr.bin of=../disk.img bs=512 count=1 conv=notrunc

2.3 编译及烧写

cong@msi:/work/os/code/1mbr$ make
nasm mbr.S -o mbr.bin
cong@msi:/work/os/code/1mbr$ file ./mbr.bin
./mbr.bin: x86 boot sector                        -->file能正确的识别出这是一个boot sector就说明成功了

cong@msi:/work/os/code/1mbr$ make flash
rm ../disk.img
rm: cannot remove ‘../disk.img’: No such file or directory    -->这个rm删除错误不影响下面的指令
make: [flash] Error 1 (ignored)
dd if=/dev/zero of=../disk.img bs=1M count=30
30+0 records in
30+0 records out
31457280 bytes (31 MB) copied, 0.0154234 s, 2.0 GB/s
dd if=./mbr.bin of=../disk.img bs=512 count=1 conv=notrunc
1+0 records in
1+0 records out
512 bytes (512 B) copied, 7.6391e-05 s, 6.7 MB/s

2.4 运行

cong@msi:/work/os/code/1mbr$ bochs
========================================================================
                       Bochs x86 Emulator 2.6.8                    -->注意apt-get install 安装的是2.4.*,源码安装的是2.6.8
                Built from SVN snapshot on May 3, 2015
                  Compiled on Aug 15 2016 at 15:49:17
========================================================================
00000000000i[ ] BXSHARE not set. using compile time default '/work/os/bochs-2.6.8/install/share/bochs'
00000000000i[ ] reading configuration from /work/os/bochs-2.6.8/install/bin/bochsrc                    -->这个是配置的bochsrc路径
00000000000e[ ] /work/os/bochs-2.6.8/install/bin/bochsrc:716: ataX-master/slave CHS set to 0/0/0 - autodetection enabled
------------------------------
Bochs Configuration: Main Menu
------------------------------

This is the Bochs Configuration Interface, where you can describe the
machine that you want to simulate. Bochs has already searched for a
configuration file (typically called bochsrc.txt) and loaded it if it
could be found. When you are satisfied with the configuration, go
ahead and start the simulation.

You can also start bochs with the -q option to skip these menus.

1. Restore factory default configuration
2. Read options from...
3. Edit options
4. Save options to...
5. Restore the Bochs state from...
6. Begin simulation
7. Quit now

Please choose one: [6]
00000000000i[ ] installing x module as the Bochs GUI
00000000000i[ ] using log file bochsout.txt
Next at t=0
(0) [0x0000fffffff0] f000:fff0 (unk. ctxt): jmpf 0xf000:e05b ; ea5be000f0
<bochs:1> b 0x7C00                           -->在0x7C00处设断点
<bochs:2> c
(0) Breakpoint 1, 0x00007c00 in ?? ()
Next at t=156815929
(0) [0x000000007c00] 0000:7c00 (unk. ctxt): jmp .-2 (0x00007c00) ; ebfe
<bochs:3>

此时bochs的gui界面卡住了。

注: 如果mbr.S中没有写对，例如把0xaa55写成了0x55aa，make flash之后会出现: No bootable device.
2.5 代码下载
1mbr.rar(下载后改名为1mbr.tar.gz)
bochsrc.rar  (下载后改名为bochsrc.tar.gz)

---

3. 加几个字符
3.1 打印几个字符

cong@msi:/work/os/code/1mbr$ cat mbr.S
org 0x7C00
    mov ax, cs
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov ax, 0xb800
    mov gs, ax


    mov byte [gs:0x00], '1'
    mov byte [gs:0x01], 0xA4

    mov byte [gs:0x02], ' '
    mov byte [gs:0x03], 0xA4

    mov byte [gs:0x04], 'M'
    mov byte [gs:0x05], 0xA4

    mov byte [gs:0x06], 'B'
    mov byte [gs:0x07], 0xA4

    mov byte [gs:0x08], 'R'
    mov byte [gs:0x09], 0xA4

    jmp $
times 510-($-$$) db 0
dw 0xaa55

3.2 配置好后，编译及运行就相当简单了

cong@msi:/work/os/code/1mbr$ make            -->编译
nasm mbr.S -o mbr.bin
cong@msi:/work/os/code/1mbr$ make flash      -->刷到disk.img中
rm ../disk.img
dd if=/dev/zero of=../disk.img bs=1M count=30
30+0 records in
30+0 records out
31457280 bytes (31 MB) copied, 0.0179666 s, 1.8 GB/s
dd if=./mbr.bin of=../disk.img bs=512 count=1 conv=notrunc
1+0 records in
1+0 records out
512 bytes (512 B) copied, 8.0688e-05 s, 6.3 MB/s
cong@msi:/work/os/code/1mbr$ bochs            -->这儿运行的是从源码编出来的bochs

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附录:
1. 每次运行bochs时都会在当前目录下生成bochsout.txt
改bochsrc的L761:  将bochsout.txt --> log: /tmp/bochsout.txt
这样每次运行bochs时会bochsout.txt就放在了/tmp目录下