linu0.12--1.实验环境的搭建

1. linux0.12的代码
基于hufeng的可在Ubuntu12.4,gcc4.6.3下编译运行的linux-0.12代码
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二. bochs的安装及使用
1. ubuntu14.04 64位下安装bochs

cong@msi:/tmp$ sudo apt-get install bochs          --> 这样安装完成后会运行会出现下面的错误

Message: dlopen failed for module 'x': file not found
cong@msi:/tmp$ sudo apt-get install bochs-x       --> 安装完bochs-x后，再运行还会出现下面的错误

bochs-bin: symbol lookup error: /usr/lib/bochs/plugins/libbx_x.so: undefined symbol: XpmCreatePixmapFromData
cong@msi:/tmp$ sudo apt-get install bochs-sdl    --> 缺少显示sdl库，仅安装不行，
                                                 --> 还需要在bochrc中加上display_library: sdl

2. 一个基本的bochrc
cong@msi:/work/oldlinux/linux12$ cat bochrc

megs: 32
romimage: file=$BXSHARE/BIOS-bochs-latest
vgaromimage: file=$BXSHARE/VGABIOS-lgpl-latest
floppya: 1_44="Image", status=inserted
ata0-master: type=disk, path="rootimage-0.12-hd", mode=flat, cylinders=487, heads=16, spt=63
boot: floppy
mouse: enabled=0
log: ../bochsout.txt
panic: action=ask
error: action=report
info: action=report
debug: action=ignore
#debug: action=ignore
vga_update_interval: 300000
display_library: sdl

a. 去http://oldlinux.org/Linux.old/bochs-images/ 下载linux-0.12-080324.zip，
解压出里面的rootimage-0.12-hd，作为硬盘文件系统
b. 上面的$BXSHARE默认设为/usr/share/bochs
所以romimage与vgaromimage的路径都得在/usr/share/bochs/下找到才行

3. bochs下的gdb调试
a. 源码编译出带gdb调试的bochs

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

b. bochs的配置文件bochsrc_gdb

cong@msi:/work/os/linux12$ diff ./bochrc_fd  bochrc_gdb
1135a1136
> gdbstub: enabled=1, port=1234, text_base=0, data_base=0, bss_base=0    -->默认这个enable=0

c. 运行bochs

/work/os/bochs-2.6.8_gdb/install/bin/bochs -q -f ./bochrc_gdb
========================================================================
                       Bochs x86 Emulator 2.6.8
                Built from SVN snapshot on May 3, 2015
                  Compiled on Sep  2 2016 at 11:06:47
========================================================================
00000000000i[ ] BXSHARE not set. using compile time default '/work/os/bochs-2.6.8_gdb/install/share/bochs'
00000000000i[ ] reading configuration from ./bochrc_gdb
00000000000e[ ] ./bochrc_gdb:715: ataX-master/slave CHS set to 0/0/0 - autodetection enabled
00000000000i[ ] Enabled gdbstub                         -->enable=1之后会打印Enable
00000000000i[ ] installing x module as the Bochs GUI
00000000000i[ ] using log file /tmp/bochsout.txt
Waiting for gdb connection on port 1234                  -->会停在这儿

d. 启动另一个terminal

cong@msi:/work/os/linux12$ gdb tools/system
Reading symbols from tools/system...done.
(gdb) target remote localhost:1234       -->这时bochs端会打印 Connected to 127.0.0.1
Remote debugging using localhost:1234
0x0000fff0 in sys_mount (dev_name=0x0 <startup_32>, dir_name=0x0 <startup_32>, rw_flag=0) at super.c:231
231            iput(dir_i);
(gdb) b main
Breakpoint 1 at 0x67d8: file init/main.c, line 130.
(gdb) c
Continuing.

Breakpoint 1, main () at init/main.c:130
130    {            /* The startup routine assumes (well, ...) this */
(gdb) n
135         ROOT_DEV = ORIG_ROOT_DEV;
(gdb)
136         SWAP_DEV = ORIG_SWAP_DEV;
(gdb) p /x ROOT_DEV
$1 = 0x21d

e. 为了避免每次都要敲一堆命令，建立一个.gdbinit脚本

cong@msi:/work/os/linux12$ cat .gdbinit
break main
target remote localhost:1234

e.1 发现一个问题，这个.gdbinit脚本不起作用

cong@msi:/work/os/linux12$ gdb -q tools/system
Reading symbols from tools/system...done.
warning: File "/work/os/linux12/.gdbinit" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
    add-auto-load-safe-path /work/os/linux12/.gdbinit
line to your configuration file "/home/cong/.gdbinit".
To completely disable this security protection add
    set auto-load safe-path /
line to your configuration file "/home/cong/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
    info "(gdb)Auto-loading safe path"
(gdb)

解决方法上面都说了在/home/cong/.gdbinit下加上一行就可以了

cong@msi:~$ cat .gdbinit
add-auto-load-safe-path /work/os/linux12/.gdbinit

注意: 是在~目录下新建一个.gdbinit，不是在linux0.12的目录下