操作系统实验一到实验九合集(哈工大李治军)（一）

LDS AX,[100H]
! 结果：AX=4100H  DS=0302H

mov AX,[100H]
mov DS,[100H+2]

s:movsb
 loop s

push IP
jmp near ptr 标号

pop IP

entry _start
_start:
    mov ah,#0x03        ! 设置功能号
    xor bh,bh           ! 将bh置0
    int 0x10            ! 返回行号和列号，供显示串用
    mov cx,#52          ！要显示的字符串长度
    mov bx,#0x0007      ! bh=0,bl=07(正常的黑底白字)
    mov bp,#msg1        ! es:bp 要显示的字符串物理地址
    mov ax,#0x07c0      ! 将es段寄存器置为#0x07c0
    mov es,ax           
    mov ax,#0x1301      ! ah=13(设置功能号),al=01(目标字符串仅仅包含字符，属性在BL中包含，光标停在字符串结尾处)
    int 0x10            ! 显示字符串
! 设置一个无限循环(纯粹为了能一直看到字符串显示)
inf_loop:
    jmp inf_loop
! 字符串信息
msg1:
    .byte   13,10           ! 换行+回车
    .ascii  "Welcome to the world without assembly language"
    .byte   13,10,13,10     ! 换行+回车
! 将
.org 510
! 启动盘具有有效引导扇区的标志。仅供BIOS中的程序加载引导扇区时识别使用。它必须位于引导扇区的最后两个字节中
boot_flag:
    .word   0xAA55

$ as86 -0 -a -o bootsect.o bootsect.s
$ ld86 -0 -s -o bootsect bootsect.o

struct exec {
    unsigned char a_magic[2];  //执行文件魔数
    unsigned char a_flags;
    unsigned char a_cpu;       //CPU标识号
    unsigned char a_hdrlen;    //头部长度，32字节或48字节
    unsigned char a_unused;
    unsigned short a_version;
    long a_text; long a_data; long a_bss; //代码段长度、数据段长度、堆长度
    long a_entry;    //执行入口地址
    long a_total;    //分配的内存总量
    long a_syms;     //符号表大小
};

$ dd bs=1 if=bootsect of=Image skip=32

# 当前的工作路径为 /oslab/linux-0.11/boot/
# 将刚刚生成的 Image 复制到 linux-0.11 目录下
$ cp ./Image ../Image
# 执行 oslab 目录中的 run 脚本
$ ../../run

entry _start
_start:
  mov ah,#0x03
  xor bh,bh
  int 0x10
  mov cx,#25
  mov bx,#0x0007
  mov bp,#msg2
  mov ax,cs    ! 这里的cs其实就是这段代码的段地址
  mov es,ax
  mov ax,#0x1301
  int 0x10
inf_loop:
  jmp inf_loop
msg2:
  .byte 13,10
  .ascii  "Now we are in SETUP"
  .byte 13,10,13,10
.org 510
boot_flag:
  .word 0xAA55

SETUOLEN=2              ! 读入的扇区数
SETUPSEG=0x07e0         ! setup代码的段地址
entry _start
_start:
    mov ah,#0x03        ! 设置功能号
    xor bh,bh           ! 将bh置0
    int 0x10            ! 返回行号和列号，供显示串用
    mov cx,#52          ！要显示的字符串长度
    mov bx,#0x0007      ! bh=0,bl=07(正常的黑底白字)
    mov bp,#msg1        ! es:bp 要显示的字符串物理地址
    mov ax,#0x07c0      ! 将es段寄存器置为#0x07c0
    mov es,ax           
    mov ax,#0x1301      ! ah=13(设置功能号),al=01(目标字符串仅仅包含字符，属性在BL中包含，光标停在字符串结尾处)
    int 0x10            ! 显示字符串
! 将setup模块从磁盘的第二个扇区开始读到0x7e00
load_setup:
    mov dx,#0x0000                  ! 磁头=0；驱动器号=0
    mov cx,#0x0002                  ! 磁道=0；扇区=2
    mov bx,#0x0200                  ! 偏移地址
    mov ax,#0x0200+SETUPLEN         ! 设置功能号；需要读出的扇区数量
    int 0x13                        ! 读磁盘扇区到内存
    jnc ok_load_setup               ! CF=0(读入成功)跳转到ok_load_setup  
    mov dx,#0x0000                  ! 如果读入失败，使用功能号ah=0x00————磁盘系统复位
    mov ax,#0x0000
    int 0x13
    jmp load_setup                  ! 尝试重新读入
ok_load_setup:
    jmpi    0,SETUPSEG              ! 段间跳转指令，跳转到setup模块处(0x07e0:0000)
! 字符串信息
msg1:
    .byte   13,10           ! 换行+回车
    .ascii  "Welcome to the world without assembly language"
    .byte   13,10,13,10     ! 换行+回车
! 将
.org 510
! 启动盘具有有效引导扇区的标志。仅供BIOS中的程序加载引导扇区时识别使用。它必须位于引导扇区的最后两个字节中
boot_flag:
    .word   0xAA55

$ make BootImage

$ cd ~/oslab/linux-0.11
$ make BootImage
$ ../run

lds    si,[4*0x41]

INITSEG  = 0x9000                   ! 参数存放位置的段地址
entry _start
_start:
! 打印 "NOW we are in SETUP"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#25
    mov bx,#0x0007
    mov bp,#msg2
    mov ax,cs
    mov es,ax
    mov ax,#0x1301
    int 0x10
! 获取光标位置
    mov ax,#INITSEG
    mov ds,ax
    mov ah,#0x03
    xor bh,bh
    int 0x10                        ! 返回：dh = 行号；dl = 列号
    mov [0],dx                      ! 存储到内存0x9000:0处
! 获取内存大小
    mov ah,#0x88
    int 0x15                        ! 返回：ax = 从0x100000(1M)处开始的扩展内存大小(KB)
    mov [2],ax                      ! 将扩展内存数值存放在0x90002处（1个字）
! 读第一个磁盘参数表复制到0x90004处
    mov ax,#0x0000
    mov ds,ax
    lds si,[4*0x41]                 ! 把低字(2B)置为偏移地址，高字(2B)置为段地址
    mov ax,#INITSEG
    mov es,ax
    mov di,#0x0004
    mov cx,#0x10                    ! 重复16次，即传送16B
    rep
    movsb                           ! 按字节传送
! 打印前的准备
    mov ax,cs
    mov es,ax
    mov ax,#INITSEG
    mov ds,ax
! 打印"Cursor position:"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#18
    mov bx,#0x0007
    mov bp,#msg_cursor
    mov ax,#0x1301
    int 0x10
! 打印光标位置
    mov dx,[0]
    call    print_hex
! 打印"Memory Size:"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#14
    mov bx,#0x0007
    mov bp,#msg_memory
    mov ax,#0x1301
    int 0x10
! 打印内存大小
    mov dx,[2]
    call    print_hex
! 打印"KB"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#2
    mov bx,#0x0007
    mov bp,#msg_kb
    mov ax,#0x1301
    int 0x10
! 打印"Cyls:" 
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#7
    mov bx,#0x0007
    mov bp,#msg_cyles
    mov ax,#0x1301
    int 0x10
! 打印柱面数   
    mov dx,[4]
    call    print_hex
! 打印"Heads:"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#8
    mov bx,#0x0007
    mov bp,#msg_heads
    mov ax,#0x1301
    int 0x10
! 打印磁头数
    mov dx,[6]
    call    print_hex
! 打印"Sectors:"
    mov ah,#0x03
    xor bh,bh
    int 0x10
    mov cx,#10
    mov bx,#0x0007
    mov bp,#msg_sectors
    mov ax,#0x1301
    int 0x10
    mov dx,[18]
    call    print_hex
inf_loop:
    jmp inf_loop
! 上面的call都转到这里
print_hex:
    mov    cx,#4                    ! dx(16位)可以显示4个十六进制数字
print_digit:
    rol    dx,#4                    ! 取 dx 的高4比特移到低4比特处
    mov    ax,#0xe0f                ! ah = 请求的功能值(显示单个字符)，al = 半字节(4个比特)掩码
    and    al,dl                    ! 前4位会被置为0
    add    al,#0x30                 ! 给 al 数字加上十六进制 0x30
    cmp    al,#0x3a                 ! 比较看是否大于数字十
    jl     outp                     ! 是一个不大于十的数字则跳转
    add    al,#0x07                 ! 否则就是a~f，要多加7
outp:
    int    0x10                     ! 显示单个字符
    loop   print_digit              ! 重复4次
    ret                             
! 打印换行回车
print_nl:
    mov    ax,#0xe0d     ! CR
    int    0x10
    mov    al,#0xa     ! LF
    int    0x10
    ret
msg2:
    .byte 13,10
    .ascii "NOW we are in SETUP"
    .byte 13,10,13,10
msg_cursor:
    .byte 13,10
    .ascii "Cursor position:"
msg_memory:
    .byte 13,10
    .ascii "Memory Size:"
msg_cyles:
    .byte 13,10
    .ascii "Cyls:"
msg_heads:
    .byte 13,10
    .ascii "Heads:"
msg_sectors:
    .byte 13,10
    .ascii "Sectors:"
msg_kb:
    .ascii "KB"
.org 510
boot_flag:
    .word 0xAA55

int iam(const char * name);

int whoami(char* name, unsigned int size);

#define __LIBRARY__
#include <unistd.h>
_syscall1(int, close, int, fd)

#define _syscall1(type,name,atype,a) \
type name(atype a) \
{ \
long __res; \
__asm__ volatile ("int $0x80" \
    : "=a" (__res) \
    : "0" (__NR_##name),"b" ((long)(a))); \
if (__res >= 0) \
    return (type) __res; \
errno = -__res; \
return -1; \
}

int close(int fd)
{
    long __res;
    __asm__ volatile ("int $0x80"
        : "=a" (__res)
        : "0" (__NR_close),"b" ((long)(fd)));
    if (__res >= 0)
        return (int) __res;
    errno = -__res;
    return -1;
}

#define __NR_close    6
/*
所以添加系统调用时需要修改include/unistd.h文件，
使其包含__NR_whoami和__NR_iam。
*/

而在应用程序中，要有：
*/
/* 有它，_syscall1 等才有效。详见unistd.h */
#define __LIBRARY__
/* 有它，编译器才能获知自定义的系统调用的编号 */
#include "unistd.h"
/* iam()在用户空间的接口函数 */
_syscall1(int, iam, const char*, name);
/* whoami()在用户空间的接口函数 */
_syscall2(int, whoami,char*,name,unsigned int,size);

void main(void)
{
//    ……
    time_init();
    sched_init();
    buffer_init(buffer_memory_end);
//    ……
}

void sched_init(void)
{
//    ……
    set_system_gate(0x80,&system_call);
}

#define set_system_gate(n,addr) \
    _set_gate(&idt[n],15,3,addr)

#define _set_gate(gate_addr,type,dpl,addr) \
__asm__ ("movw %%dx,%%ax\n\t" \
    "movw %0,%%dx\n\t" \
    "movl %%eax,%1\n\t" \
    "movl %%edx,%2" \
    : \
    : "i" ((short) (0x8000+(dpl<<13)+(type<<8))), \
    "o" (*((char *) (gate_addr))), \
    "o" (*(4+(char *) (gate_addr))), \
    "d" ((char *) (addr)),"a" (0x00080000))

!……
! # 这是系统调用总数。如果增删了系统调用，必须做相应修改
nr_system_calls = 72
!……
.globl system_call
.align 2
system_call:
! # 检查系统调用编号是否在合法范围内
    cmpl \$nr_system_calls-1,%eax
    ja bad_sys_call
    push %ds
    push %es
    push %fs
    pushl %edx
    pushl %ecx
! # push %ebx,%ecx,%edx，是传递给系统调用的参数
    pushl %ebx
! # 让ds, es指向GDT，内核地址空间
    movl $0x10,%edx
    mov %dx,%ds
    mov %dx,%es
    movl $0x17,%edx
! # 让fs指向LDT，用户地址空间
    mov %dx,%fs
    call sys_call_table(,%eax,4)
    pushl %eax
    movl current,%eax
    cmpl $0,state(%eax)
    jne reschedule
    cmpl $0,counter(%eax)
    je reschedule

fn_ptr sys_call_table[] = { sys_setup, sys_exit, sys_fork, sys_read,...

extern int sys_whoami();
extern int sys_iam();

int sys_close(unsigned int fd)
{
//    ……
    return (0);
}

#include <asm/segment.h>
#include <errno.h>
#include <string.h>
char _myname[24];
int sys_iam(const char *name)
{
    char str[25];
    int i = 0;
    do
    {
        // get char from user input
        str[i] = get_fs_byte(name + i);
    } while (i <= 25 && str[i++] != '\0');
    if (i > 24)
    {
        errno = EINVAL;
        i = -1;
    }
    else
    {
        // copy from user mode to kernel mode
        strcpy(_myname, str);
    }
    return i;
}
int sys_whoami(char *name, unsigned int size)
{
    int length = strlen(_myname);
    printk("%s\n", _myname);
    if (size < length)
    {
        errno = EINVAL;
        length = -1;
    }
    else
    {
        int i = 0;
        for (i = 0; i < length; i++)
        {
            // copy from kernel mode to user mode
            put_fs_byte(_myname[i], name + i);
        }
    }
    return length;
}

OBJS  = sched.o system_call.o traps.o asm.o fork.o \
        panic.o printk.o vsprintf.o sys.o exit.o \
        signal.o mktime.o

OBJS  = sched.o system_call.o traps.o asm.o fork.o \
        panic.o printk.o vsprintf.o sys.o exit.o \
        signal.o mktime.o who.o

### Dependencies:
exit.s exit.o: exit.c ../include/errno.h ../include/signal.h \
  ../include/sys/types.h ../include/sys/wait.h ../include/linux/sched.h \
  ../include/linux/head.h ../include/linux/fs.h ../include/linux/mm.h \
  ../include/linux/kernel.h ../include/linux/tty.h ../include/termios.h \
  ../include/asm/segment.h

### Dependencies:
who.s who.o: who.c ../include/linux/kernel.h ../include/unistd.h
exit.s exit.o: exit.c ../include/errno.h ../include/signal.h \
  ../include/sys/types.h ../include/sys/wait.h ../include/linux/sched.h \
  ../include/linux/head.h ../include/linux/fs.h ../include/linux/mm.h \
  ../include/linux/kernel.h ../include/linux/tty.h ../include/termios.h \
  ../include/asm/segment.h

/* iam.c */
#define __LIBRARY__
#include <unistd.h> 
#include <errno.h>
#include <asm/segment.h> 
#include <linux/kernel.h>
_syscall1(int, iam, const char*, name);
int main(int argc, char *argv[])
{
    /*调用系统调用iam()*/
    iam(argv[1]);
    return 0;
}

/* whoami.c */
#define __LIBRARY__
#include <unistd.h> 
#include <errno.h>
#include <asm/segment.h> 
#include <linux/kernel.h>
#include <stdio.h>
_syscall2(int, whoami,char *,name,unsigned int,size);
int main(int argc, char *argv[])
{
    char username[64] = {0};
    /*调用系统调用whoami()*/
    whoami(username, 24);
    printf("%s\n", username);
    return 0;
}

sudo ./mount-hdc 

cp iam.c whoami.c hdc/usr/root

[/usr/root]# gcc -o iam iam.c
[/usr/root]# gcc -o whoami whoami.c

[/usr/root]# ./iam wcf
[/usr/root]# ./whoami

#define __NR_whoami     72
#define __NR_iam      73