一，MIT6.828课程实验环境搭建

1.步骤

1. 安装VMware15并安装虚拟机 Ubuntu18.04.3
2. 安装git 和python
3. 按照tools安装编译器工具链
4. 编译jos系统并加载

输入命令： % objdump -i
第二行结果为elf32-i386
输入: % gcc -m32 -print-libgcc-file-name
结果为Command 'gcc' not found, but can be installed with:
安装gcc % sudo apt-get install -y build-essential gdb

输入
 @ubuntu:~$ gcc -m32 -print-libgcc-file-name
结果成功
/usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a 

下载qemu
git clone https://github.com/mit-pdos/6.828-qemu.git qemu
还可需要安装libsdl1.2-dev、libtool-bin、libglib2.0-dev、libz-dev 和 libpixman-1-dev。
再输入：

1 % cd qemu/
2 % ./configure
3.%  make
报错
  CC    qga/commands-posix.o
qga/commands-posix.c: In function ‘dev_major_minor’:
qga/commands-posix.c:633:13: error: In the GNU C Library, "major" is defined
 by <sys/sysmacros.h>. For historical compatibility, it is
 currently defined by <sys/types.h> as well, but we plan to
 remove this soon. To use "major", include <sys/sysmacros.h>
 directly. If you did not intend to use a system-defined macro
 "major", you should undefine it after including <sys/types.h>. [-Werror]
         *devmajor = major(st.st_rdev);
             ^~~~~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                                                                                                                                                                                                              
qga/commands-posix.c:634:13: error: In the GNU C Library, "minor" is defined
 by <sys/sysmacros.h>. For historical compatibility, it is
 currently defined by <sys/types.h> as well, but we plan to
 remove this soon. To use "minor", include <sys/sysmacros.h>
 directly. If you did not intend to use a system-defined macro
 "minor", you should undefine it after including <sys/types.h>. [-Werror]
         *devminor = minor(st.st_rdev);
             ^~~~~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                                                                                                                                                                                                              
cc1: all warnings being treated as errors


解决方法：
在 qga/commands-posix.c文件中加 #include <sys/sysmacros.h>


再报错：
block/blkdebug.c: In function ‘blkdebug_refresh_filename’:
block/blkdebug.c:749:31: error: ‘%s’ directive output may be truncated writing up to 4095 bytes into a region of size 4086 [-Werror=format-truncation=]
                  "blkdebug:%s:%s",
                               ^~
In file included from /usr/include/stdio.h:862:0,
                 from /home/wzd/qemu/include/qemu-common.h:27,
                 from block/blkdebug.c:25:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’ output 11 or more bytes (assuming 4106) into a destination of size 4096
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
/home/wzd/qemu/rules.mak:57: recipe for target 'block/blkdebug.o' failed

解决方法：config-host.mak文件中的-Werror去掉 
4. % sudo make install

下载jos源码
git clone https://pdos.csail.mit.edu/6.828/2018/jos.git lab

% cd lab 
% sudo make
报错：
ld: warning: section `.bss' type changed to PROGBITS
obj/kern/printfmt.o: In function `printnum':
lib/printfmt.c:41: undefined reference to `__udivdi3'
lib/printfmt.c:49: undefined reference to `__umoddi3'
kern/Makefrag:70: recipe for target 'obj/kern/kernel' failed
make: *** [obj/kern/kernel] Error 1
解决方法：
% sudo apt-get install gcc-4.8-multilib
再编译：
% sudo make
% sudo make qemu

终于成功

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