哈工大操作系统试验1 操作系统的引导
这次实验涉及一些汇编知识，不过指导书上写的还是比较清楚的，抄一抄上面的代码，基本就ok了。
实验主要需要改3个文件
build.c 只要吧文件末尾稍微改成这样
if ((id=open(argv[3],O_RDONLY,0)) >= 0) //就是打开文件的一个函数，失败的话会返回-1哦～
{for (i=0 ; (c=read(id,buf,sizeof buf))>0 ; i+=c )
if (write(1,buf,c)!=c)
die("Write call failed");
close(id);
fprintf(stderr,"System is %d bytes.\n",i);
if (i > SYS_SIZE*16)
die("System is too big");}
return(0);
build.c 原来是这样的
if ((id=open(argv[3],O_RDONLY,0))<0)
die("Unable to open 'system'");
// if (read(id,buf,GCC_HEADER) != GCC_HEADER)
// die("Unable to read header of 'system'");
// if (((long *) buf)[5] != 0)
// die("Non-GCC header of 'system'");
for (i=0 ; (c=read(id,buf,sizeof buf))>0 ; i+=c )
if (write(1,buf,c)!=c)
die("Write call failed");
close(id);
fprintf(stderr,"System is %d bytes.\n",i);
if (i > SYS_SIZE*16)
die("System is too big");
return(0);bootsect.s 基本不用过动，如果觉得无聊可以改一改输出的那个字符串。
msg1: .byte 13,10 ！这个好像是伪指令 byte和ascii是两种数据的表示方法 .ascii "fuck..." .byte 13,10,13,10
主要需要改动的是setup这个文件。
首先解释一下，输出一条字符串的代码。
!print the message
MOV AX,#SETUPSEG
MOV ES,AX ！赋值给ES不能直接赋值，需要用AX做中转
MOV AH,#0X03 ！下三行为读入光标位置
XOR BH,BH
INT 0X10
MOV CX,#25 ！字符串长度，设大一点没关系~
MOV BX,#0X0007
MOV BP,#MSG2
MOV AX,#0X1301
INT 0X10
ES 和 BP 分别是段寄存器和，偏移地址，把ES设#SETUPSEG是内存中存放setup.s开始的地方，BP表示存放#MSG2的偏移地
一般的ES BP 作为附加数据段寄存器，程序中有多个数据段时，经常用到，处理字符串时，也经常会用的哦～
INT 0x10 是BOIS 的视频中断，所有与显示有管的调用都需要通过该中断实现。
AL -- 需要显示的ASCII字符
BH -- 页号（本次实验中一直设为0x00就可以啦）
BL -- 文本属性（设成0x07就好啦）通修改它可以选择不同的字体颜色偶～
把它加在setup的开头，就好啦～就像这样。。。
! NOTE! These had better be the same as in bootsect.s!
！宏的设置
INITSEG = 0X9000 ! WE MOVE BOOT HERE - OUT OF THE WAY
SYSSEG = 0X1000 ! SYSTEM LOADED AT 0X10000 (65536).
SETUPSEG = 0X9020 ! THIS IS THE CURRENT SEGMENT
！伪指令globl的意思为后面的标识符都是全局的，即使不使用也会强制引入。
.globl begtext, begdata, begbss, endtext, enddata, endbss
.text ！文本段
begtext:
.DATA ！数据段
begdata:
.bss ！未初始化的数据段
begbss:
.text
entry start
start:
!print the message
MOV AX,#SETUPSEG
MOV ES,AX
MOV AH,#0X03
XOR BH,BH
INT 0X10
MOV CX,#25
MOV BX,#0X0007
MOV BP,#MSG_HELLOW
MOV AX,#0X1301
INT 0X10
当然不要忘了在最后加上叫做MSG2的数据段，关于为啥要这样写，我也不知道，反正课件就是这样写的，可以去问问老师。。。。。
MSG_HELLOW:
.byte 13,10
.ascii "Now we are in SETUP"
.byte 13,10,13,10获取系统数据的代码，老师已经写好了，突然觉得老师好牛逼啊～留下获取数据的代码，把下面没用的删掉就好啦～
具体怎么删，请自己斟酌哦～
不删的话系统可能会不断重启噢~
最后需要吧数据输出就好拉～
! print the cursor position
mov ah,#0x03 ! read cursor pos
xor bh,bh
int 0x10
MOV CX,#25
mov bx,#0x0007 ! page 0, attribute 7 (normal)
MOV BP,#MSG3
MOV AX,#0X1301 ! WRITE STRING, MOVE CURSOR
INT 0X10
MOV AX,#INITSEG
MOV DS,AX !SET THE DATA SEG ADDRESS, EVEN IT HAS BEEN SET.
! get data
MOV CX,#4
MOV DX,[0]
PRINT_DIGIT1: !print the data
ROL DX,#4
MOV AX,#0XE0F
AND AL,DL
ADD AL,#0X30
CMP AL,#0X3A
JL OUTP1
ADD AL, #0X07
OUTP1:
INT 0X10
LOOP PRINT_DIGIT1
! MOV AX,#SETUPSEG
! MOV DS,AX
! MOV ES,AX一开始是输出描述性的字符串，PRINT_DIGITL是输出内存中的数据
ROL是左位移，
ROL DX，#4 是把DX的低四位移到高四位上。
CMP 是比较指令 类似于if
jl是一个条件转移指令，jump less 小于转跳，用于有符号转跳
类似还有 jg ， jump large
ja jump above ， jb jump below 这两个是用于无符号数比较的。
其他指导书上有详细注释
不要忘记在末尾加上这个
MSG_CURSOR:
.byte 13,10
.ascii "the cursor position is:"
MSG_MEMORY:
.byte 13,10
.ascii "the size of the extended memory is:"
这样既本就完成啦～
setup的完整代码如下
!
! setup.s (C) 1991 Linus Torvalds
!
! setup.s is responsible for getting the system data from the BIOS,
! AND PUTTING THEM INTO THE APPROPRIATE PLACES IN SYSTEM MEMORY.
! both setup.s and system has been loaded by the bootblock.
!
! This code asks the bios for memory/disk/other parameters, and
! puts them in a "safe" place: 0x90000-0x901FF, ie where the
! boot-block used to be. It is then up to the protected mode
! system to read them from there before the area is overwritten
! FOR BUFFER-BLOCKS.
!
! NOTE! These had better be the same as in bootsect.s!
INITSEG = 0X9000 ! WE MOVE BOOT HERE - OUT OF THE WAY
SYSSEG = 0X1000 ! SYSTEM LOADED AT 0X10000 (65536).
SETUPSEG = 0X9020 ! THIS IS THE CURRENT SEGMENT
.globl begtext, begdata, begbss, endtext, enddata, endbss
.text
begtext:
.DATA
begdata:
.bss
begbss:
.text
entry start
start:
!print the message which wing edit
MOV AX,#SETUPSEG
MOV ES,AX
MOV AH,#0X03
XOR BH,BH
INT 0X10
MOV CX,#25
MOV BX,#0X0007
MOV BP,#MSG_HELLOW
MOV AX,#0X1301
INT 0X10
! ok, the read went well so we get current cursor position and save it for
! posterity.
MOV AX,#INITSEG ! THIS IS DONE IN BOOTSECT ALREADY, BUT...
MOV DS,AX
MOV AH,#0X03 ! READ CURSOR POS
XOR BH,BH
INT 0X10 ! SAVE IT IN KNOWN PLACE, CON_INIT FETCHES
MOV [0],DX ! IT FROM 0X90000.
! Get memory size (extended mem, kB)
MOV AH,#0X88
INT 0X15
MOV [2],AX
! Get video-card data:
MOV AH,#0X0F
INT 0X10
MOV [4],BX ! BH = DISPLAY PAGE
MOV [6],AX ! AL = VIDEO MODE, AH = WINDOW WIDTH
! check for EGA/VGA and some config parameters
MOV AH,#0X12
MOV BL,#0X10
INT 0X10
MOV [8],AX
MOV [10],BX
MOV [12],CX
! Get hd0 data
MOV AX,#0X0000
MOV DS,AX
LDS SI,[4*0X41]
MOV AX,#INITSEG
MOV ES,AX
MOV DI,#0X0080
MOV CX,#0X10
REP
MOVSB
! Get hd1 data
MOV AX,#0X0000
MOV DS,AX
LDS SI,[4*0X46]
MOV AX,#INITSEG
MOV ES,AX
MOV DI,#0X0090
MOV CX,#0X10
REP
MOVSB
MOV AX,#SETUPSEG
MOV DS,AX
MOV ES,AX
! print some datas about the hardware:
! print the cursor position
mov ah,#0x03 ! read cursor pos
xor bh,bh
int 0x10
MOV CX,#25
mov bx,#0x0007 ! page 0, attribute 7 (normal)
MOV BP,#MSG_CURSOR
MOV AX,#0X1301 ! WRITE STRING, MOVE CURSOR
INT 0X10
MOV AX,#INITSEG
MOV DS,AX !SET THE DATA SEG ADDRESS, EVEN IT HAS BEEN SET.
MOV CX,#4
MOV DX,[0]
PRINT_DIGIT1: !print the data
ROL DX,#4
MOV AX,#0XE0F
AND AL,DL
ADD AL,#0X30
CMP AL,#0X3A
JL OUTP1
ADD AL, #0X07
OUTP1:
INT 0X10
LOOP PRINT_DIGIT1
! MOV AX,#SETUPSEG
! MOV DS,AX
! MOV ES,AX
!print size of the extended memory:
mov ah,#0x03 ! read cursor pos
xor bh,bh
int 0x10
MOV CX,#37
mov bx,#0x0007 ! page 0, attribute 7 (normal)
MOV BP,#MSG_MEMORY
MOV AX,#0X1301 ! WRITE STRING, MOVE CURSOR
INT 0X10
MOV AX,#INITSEG
MOV DS,AX !SET THE DATA SEG ADDRESS, EVEN IT HAS BEEN SET.
MOV CX,#4
MOV DX,[2]
PRINT_DIGIT2:
ROL DX,#4
MOV AX,#0XE0F
AND AL,DL
ADD AL,#0X30
CMP AL,#0X3A
JL OUTP2
ADD AL, #0X07
OUTP2:
INT 0X10
LOOP PRINT_DIGIT2
! change the line:
print_nl:
mov ax,#0xe0d
int 0x10
mov al,#0xa
int 0x10
MSG_HELLOW:
.byte 13,10
.ascii "We are in setup ou Qin~"
.byte 13,10,13,10
MSG_CURSOR:
.byte 13,10
.ascii "the cursor position is:"
MSG_MEMORY:
.byte 13,10
.ascii "the size of the extended memory is:"
.text
endtext:
.DATA
enddata:
.bss
endbss: