本次实验内容:
本实验的基本内容是修改Linux 0.11的终端设备处理代码，对键盘输入和字符显示进行非常规的控制。
在初始状态，一切如常。用户按一次F12后，把应用程序向终端输出所有字母都替换为“*”。用户再按一次F12，又恢复正常。第三次按F12，再进行输出替换。依此类推。
以ls命令为例：
正常情况：
ls
hello.c hello.o hello
第一次按F12，然后输入ls：
**
*****.* *****.* *****
第二次按F12，然后输入ls：
ls
hello.c hello.o hello
第三次按F12，然后输入ls：
**
*****.* *****.* *****
(一)修改linux-0.11/kernel/chr_drv/keyboard.S的文件
首先我们得知道 在修改之前,按下F12什么功能;
键盘I/O是典型的中断驱动，在kernel/chr_drv/console.c文件中：
void con_init(void) //控制台的初始化
{
set_trap_gate(0x21,&keyboard_interrupt); //键盘中断响应函数设为keyboard_interrupt
}
所以每次按键有动作，keyboard_interrupt函数就会被调用，它在文件kernel/chr_drv/keyboard.S
func:
/*程序210行子函数处理功能键
将功能键转化成转义字符存取到读队列中*/
pushl %eax
pushl %ecx
pushl %edx
call show_stat
popl %edx
popl %ecx
popl %eax
调用 show_stat 函数,显示当前 进程状态
屏蔽了 call show_stat的功能再改成我们自己的的功能就好了
func:
/*程序210行子函数处理功能键
将功能键转化成转义字符存取到读队列中*/
pushl %eax
pushl %ecx
pushl %edx
//call show_stat
popl %edx
popl %ecx
popl %eax
(二)修改tty_io.c文件
linux-0.11/kernel/chr_drv/tty_io.c
键盘每次输入一个字符,操作系统都会将这个字符送到字符缓冲区进行处理.
f12是一个功能键,它的扫描码是 esc,[,[,L
分别对应ascii码的27,91,91,76
所以要连续判断四次 字符呀
你说 那我判断这几个字符的时候输出了一个其他的字符,它应该显示这个其他字符啊.
所以这段处理程序就应该写在 操作系统判断字符做出功能的代码之前.
判断字符的代码是copy_to_cooked函数
增加的全局变量
int judge=-1;
int f1=0,f2=0,f3=0;
long j=0;
void copy_to_cooked(struct tty_struct * tty)
{
signed char c;
//now用来判断当前时间戳
long now;
while (!EMPTY(tty->read_q) && !FULL(tty->secondary)) {
GETCH(tty->read_q,c);
//开始添加代码
if(c==27)
{
f1=1;
j=jiffies;
//获取当前 函数的CPU心跳数,用来计时
}
else if(f1==1&&f2==0&&c==91)
f2=1;
else if(f1==1&&f2==1&&c==91)
f3=1;
else if(f1==1&&f2==1&&f3==1&&c==76)
{
now=jiffies;
if((now-j)>10)
//比如人为的输入esc,[,[,J 也会认为是F12,所以要根据四个字符的到达的时间判断是一次输入还是多次输入的~
{
printk("%ld \t %ld \n",j,now);
break;
}
judge*=-1;
continue;
}
else
f1=f2=f3=0;
//添加代码结束
if (c==13)
if (I_CRNL(tty))
c=10;
else if (I_NOCR(tty))
continue;
else ;
else if (c==10 && I_NLCR(tty))
c=13;
if (I_UCLC(tty))
c=tolower(c);
if (L_CANON(tty)) {
if (c==KILL_CHAR(tty)) {
/* deal with killing the input line */
while(!(EMPTY(tty->secondary) ||
(c=LAST(tty->secondary))==10 ||
c==EOF_CHAR(tty))) {
if (L_ECHO(tty)) {
if (c<32)
PUTCH(127,tty->write_q);
PUTCH(127,tty->write_q);
tty->write(tty);
}
DEC(tty->secondary.head);
}
continue;
}
if (c==ERASE_CHAR(tty)) {
if (EMPTY(tty->secondary) ||
(c=LAST(tty->secondary))==10 ||
c==EOF_CHAR(tty))
continue;
if (L_ECHO(tty)) {
if (c<32)
PUTCH(127,tty->write_q);
PUTCH(127,tty->write_q);
tty->write(tty);
}
DEC(tty->secondary.head);
continue;
}
if (c==STOP_CHAR(tty)) {
tty->stopped=1;
continue;
}
if (c==START_CHAR(tty)) {
tty->stopped=0;
continue;
}
}
if (L_ISIG(tty)) {
if (c==INTR_CHAR(tty)) {
tty_intr(tty,INTMASK);
continue;
}
if (c==QUIT_CHAR(tty)) {
tty_intr(tty,QUITMASK);
continue;
}
}
if (c==10 || c==EOF_CHAR(tty))
tty->secondary.data++;
if (L_ECHO(tty)) {
if (c==10) {
PUTCH(10,tty->write_q);
PUTCH(13,tty->write_q);
} else if (c<32) {
if (L_ECHOCTL(tty)) {
PUTCH('^',tty->write_q);
PUTCH(c+64,tty->write_q);
}
} else
PUTCH(c,tty->write_q);
tty->write(tty);
}
PUTCH(c,tty->secondary);
}
wake_up(&tty->secondary.proc_list);
}
修改后的tty_io.c文件
/*
* linux/kernel/tty_io.c
*
* (C) 1991 Linus Torvalds
*/
/*
* 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
* or rs-channels. It also implements echoing, cooked mode etc.
*
* Kill-line thanks to John T Kohl.
*/
#include <ctype.h>
#include <errno.h>
#include <signal.h>
#define ALRMMASK (1<<(SIGALRM-1))
#define KILLMASK (1<<(SIGKILL-1))
#define INTMASK (1<<(SIGINT-1))
#define QUITMASK (1<<(SIGQUIT-1))
#define TSTPMASK (1<<(SIGTSTP-1))
#include <linux/sched.h>
#include <linux/tty.h>
#include <asm/segment.h>
#include <asm/system.h>
#define _L_FLAG(tty,f) ((tty)->termios.c_lflag & f)
#define _I_FLAG(tty,f) ((tty)->termios.c_iflag & f)
#define _O_FLAG(tty,f) ((tty)->termios.c_oflag & f)
#define L_CANON(tty) _L_FLAG((tty),ICANON)
#define L_ISIG(tty) _L_FLAG((tty),ISIG)
#define L_ECHO(tty) _L_FLAG((tty),ECHO)
#define L_ECHOE(tty) _L_FLAG((tty),ECHOE)
#define L_ECHOK(tty) _L_FLAG((tty),ECHOK)
#define L_ECHOCTL(tty) _L_FLAG((tty),ECHOCTL)
#define L_ECHOKE(tty) _L_FLAG((tty),ECHOKE)
#define I_UCLC(tty) _I_FLAG((tty),IUCLC)
#define I_NLCR(tty) _I_FLAG((tty),INLCR)
#define I_CRNL(tty) _I_FLAG((tty),ICRNL)
#define I_NOCR(tty) _I_FLAG((tty),IGNCR)
#define O_POST(tty) _O_FLAG((tty),OPOST)
#define O_NLCR(tty) _O_FLAG((tty),ONLCR)
#define O_CRNL(tty) _O_FLAG((tty),OCRNL)
#define O_NLRET(tty) _O_FLAG((tty),ONLRET)
#define O_LCUC(tty) _O_FLAG((tty),OLCUC)
long j;
struct tty_struct tty_table[] = {
{
{ICRNL, /* change incoming CR to NL */
OPOST|ONLCR, /* change outgoing NL to CRNL */
0,
ISIG | ICANON | ECHO | ECHOCTL | ECHOKE,
0, /* console termio */
INIT_C_CC},
0, /* initial pgrp */
0, /* initial stopped */
con_write,
{0,0,0,0,""}, /* console read-queue */
{0,0,0,0,""}, /* console write-queue */
{0,0,0,0,""} /* console secondary queue */
},{
{0, /* no translation */
0, /* no translation */
B2400 | CS8,
0,
0,
INIT_C_CC},
0,
0,
rs_write,
{0x3f8,0,0,0,""}, /* rs 1 */
{0x3f8,0,0,0,""},
{0,0,0,0,""}
},{
{0, /* no translation */
0, /* no translation */
B2400 | CS8,
0,
0,
INIT_C_CC},
0,
0,
rs_write,
{0x2f8,0,0,0,""}, /* rs 2 */
{0x2f8,0,0,0,""},
{0,0,0,0,""}
}
};
/*
* these are the tables used by the machine code handlers.
* you can implement pseudo-tty's or something by changing
* them. Currently not done.
*/
struct tty_queue * table_list[]={
&tty_table[0].read_q, &tty_table[0].write_q,
&tty_table[1].read_q, &tty_table[1].write_q,
&tty_table[2].read_q, &tty_table[2].write_q
};
void tty_init(void)
{
rs_init();
con_init();
}
void tty_intr(struct tty_struct * tty, int mask)
{
int i;
if (tty->pgrp <= 0)
return;
for (i=0;i<NR_TASKS;i++)
if (task[i] && task[i]->pgrp==tty->pgrp)
task[i]->signal |= mask;
}
static void sleep_if_empty(struct tty_queue * queue)
{
cli();
while (!current->signal && EMPTY(*queue))
interruptible_sleep_on(&queue->proc_list);
sti();
}
static void sleep_if_full(struct tty_queue * queue)
{
if (!FULL(*queue))
return;
cli();
while (!current->signal && LEFT(*queue)<128)
interruptible_sleep_on(&queue->proc_list);
sti();
}
void wait_for_keypress(void)
{
sleep_if_empty(&tty_table[0].secondary);
}
int judge=-1;
int f1=0,f2=0,f3=0;
void copy_to_cooked(struct tty_struct * tty)
{
signed char c;
long now;
while (!EMPTY(tty->read_q) && !FULL(tty->secondary)) {
GETCH(tty->read_q,c);
if(c==27)
{
f1=1;
j=jiffies;
}
else if(f1==1&&f2==0&&c==91)
f2=1;
else if(f1==1&&f2==1&&c==91)
f3=1;
else if(f1==1&&f2==1&&f3==1&&c==76)
{
now=jiffies;
if((now-j)>10)
{
printk("%ld \t %ld \n",j,now);
break;
}
judge*=-1;
continue;
}
else
f1=f2=f3=0;
if (c==13)
if (I_CRNL(tty))
c=10;
else if (I_NOCR(tty))
continue;
else ;
else if (c==10 && I_NLCR(tty))
c=13;
if (I_UCLC(tty))
c=tolower(c);
if (L_CANON(tty)) {
if (c==KILL_CHAR(tty)) {
/* deal with killing the input line */
while(!(EMPTY(tty->secondary) ||
(c=LAST(tty->secondary))==10 ||
c==EOF_CHAR(tty))) {
if (L_ECHO(tty)) {
if (c<32)
PUTCH(127,tty->write_q);
PUTCH(127,tty->write_q);
tty->write(tty);
}
DEC(tty->secondary.head);
}
continue;
}
if (c==ERASE_CHAR(tty)) {
if (EMPTY(tty->secondary) ||
(c=LAST(tty->secondary))==10 ||
c==EOF_CHAR(tty))
continue;
if (L_ECHO(tty)) {
if (c<32)
PUTCH(127,tty->write_q);
PUTCH(127,tty->write_q);
tty->write(tty);
}
DEC(tty->secondary.head);
continue;
}
if (c==STOP_CHAR(tty)) {
tty->stopped=1;
continue;
}
if (c==START_CHAR(tty)) {
tty->stopped=0;
continue;
}
}
if (L_ISIG(tty)) {
if (c==INTR_CHAR(tty)) {
tty_intr(tty,INTMASK);
continue;
}
if (c==QUIT_CHAR(tty)) {
tty_intr(tty,QUITMASK);
continue;
}
}
if (c==10 || c==EOF_CHAR(tty))
tty->secondary.data++;
if (L_ECHO(tty)) {
if (c==10) {
PUTCH(10,tty->write_q);
PUTCH(13,tty->write_q);
} else if (c<32) {
if (L_ECHOCTL(tty)) {
PUTCH('^',tty->write_q);
PUTCH(c+64,tty->write_q);
}
} else
PUTCH(c,tty->write_q);
tty->write(tty);
}
PUTCH(c,tty->secondary);
}
wake_up(&tty->secondary.proc_list);
}
int tty_read(unsigned channel, char * buf, int nr)
{
struct tty_struct * tty;
char c, * b=buf;
int minimum,time,flag=0;
long oldalarm;
if (channel>2 || nr<0) return -1;
tty = &tty_table[channel];
oldalarm = current->alarm;
time = 10L*tty->termios.c_cc[VTIME];
minimum = tty->termios.c_cc[VMIN];
if (time && !minimum) {
minimum=1;
if ((flag=(!oldalarm || time+jiffies<oldalarm)))
current->alarm = time+jiffies;
}
if (minimum>nr)
minimum=nr;
while (nr>0) {
if (flag && (current->signal & ALRMMASK)) {
current->signal &= ~ALRMMASK;
break;
}
if (current->signal)
break;
if (EMPTY(tty->secondary) || (L_CANON(tty) &&
!tty->secondary.data && LEFT(tty->secondary)>20)) {
sleep_if_empty(&tty->secondary);
continue;
}
do {
GETCH(tty->secondary,c);
if (c==EOF_CHAR(tty) || c==10)
tty->secondary.data--;
if (c==EOF_CHAR(tty) && L_CANON(tty))
return (b-buf);
else {
put_fs_byte(c,b++);
if (!--nr)
break;
}
} while (nr>0 && !EMPTY(tty->secondary));
if (time && !L_CANON(tty)) {
if ((flag=(!oldalarm || time+jiffies<oldalarm)))
current->alarm = time+jiffies;
else
current->alarm = oldalarm;
}
if (L_CANON(tty)) {
if (b-buf)
break;
} else if (b-buf >= minimum)
break;
}
current->alarm = oldalarm;
if (current->signal && !(b-buf))
return -EINTR;
return (b-buf);
}
int tty_write(unsigned channel, char * buf, int nr)
{
static int cr_flag=0;
struct tty_struct * tty;
char c, *b=buf;
if (channel>2 || nr<0) return -1;
tty = channel + tty_table;
while (nr>0) {
sleep_if_full(&tty->write_q);
if (current->signal)
break;
while (nr>0 && !FULL(tty->write_q)) {
c=get_fs_byte(b);
if (O_POST(tty)) {
if (c=='\r' && O_CRNL(tty))
c='\n';
else if (c=='\n' && O_NLRET(tty))
c='\r';
if (c=='\n' && !cr_flag && O_NLCR(tty)) {
cr_flag = 1;
PUTCH(13,tty->write_q);
continue;
}
if (O_LCUC(tty))
c=toupper(c);
}
b++; nr--;
cr_flag = 0;
PUTCH(c,tty->write_q);
}
tty->write(tty);
if (nr>0)
schedule();
}
return (b-buf);
}
/*
* Jeh, sometimes I really like the 386.
* This routine is called from an interrupt,
* and there should be absolutely no problem
* with sleeping even in an interrupt (I hope).
* Of course, if somebody proves me wrong, I'll
* hate intel for all time :-). We'll have to
* be careful and see to reinstating the interrupt
* chips before calling this, though.
*
* I don't think we sleep here under normal circumstances
* anyway, which is good, as the task sleeping might be
* totally innocent.
*/
void do_tty_interrupt(int tty)
{
copy_to_cooked(tty_table+tty);
}
void chr_dev_init(void)
{
}
(三)修改linux-0.11/kernel/chr_drv/console.c
tty_io.c文件只是捕捉到了按下f12的状态
我们需要在控制程序中添加 改变输出的代码,最简单的方法是只要按下F12就把所有的字符都变成"*"号输出就行了
我们只要在con_write()函数中添加一行代码:
extern int judge;//引用代码tty_io.c中的judge变量
if(judge==1)
c='*';
con_write函数:
extern int judge;
void con_write(struct tty_struct * tty)
{
int nr;
char c;
nr = CHARS(tty->write_q);
while (nr--) {
GETCH(tty->write_q,c);
switch(state) {
case 0:
if (c>31 && c<127) {
if (x>=video_num_columns) {
x -= video_num_columns;
pos -= video_size_row;
lf();
}
if(judge==1)
c='*';
__asm__("movb attr,%%ah\n\t"
"movw %%ax,%1\n\t"
::"a" (c),"m" (*(short *)pos)
);
pos += 2;
x++;
} else if (c==27)
state=1;
else if (c==10 || c==11 || c==12)
lf();
else if (c==13)
cr();
else if (c==ERASE_CHAR(tty))
del();
else if (c==8) {
if (x) {
x--;
pos -= 2;
}
} else if (c==9) {
c=8-(x&7);
x += c;
pos += c<<1;
if (x>video_num_columns) {
x -= video_num_columns;
pos -= video_size_row;
lf();
}
c=9;
} else if (c==7)
sysbeep();
break;
case 1:
state=0;
if (c=='[')
state=2;
else if (c=='E')
gotoxy(0,y+1);
else if (c=='M')
ri();
else if (c=='D')
lf();
else if (c=='Z')
respond(tty);
else if (x=='7')
save_cur();
else if (x=='8')
restore_cur();
break;
case 2:
for(npar=0;npar<NPAR;npar++)
par[npar]=0;
npar=0;
state=3;
if ((ques=(c=='?')))
break;
case 3:
if (c==';' && npar<NPAR-1) {
npar++;
break;
} else if (c>='0' && c<='9') {
par[npar]=10*par[npar]+c-'0';
break;
} else state=4;
case 4:
state=0;
switch(c) {
case 'G': case '`':
if (par[0]) par[0]--;
gotoxy(par[0],y);
break;
case 'A':
if (!par[0]) par[0]++;
gotoxy(x,y-par[0]);
break;
case 'B': case 'e':
if (!par[0]) par[0]++;
gotoxy(x,y+par[0]);
break;
case 'C': case 'a':
if (!par[0]) par[0]++;
gotoxy(x+par[0],y);
break;
case 'D':
if (!par[0]) par[0]++;
gotoxy(x-par[0],y);
break;
case 'E':
if (!par[0]) par[0]++;
gotoxy(0,y+par[0]);
break;
case 'F':
if (!par[0]) par[0]++;
gotoxy(0,y-par[0]);
break;
case 'd':
if (par[0]) par[0]--;
gotoxy(x,par[0]);
break;
case 'H': case 'f':
if (par[0]) par[0]--;
if (par[1]) par[1]--;
gotoxy(par[1],par[0]);
break;
case 'J':
csi_J(par[0]);
break;
case 'K':
csi_K(par[0]);
break;
case 'L':
csi_L(par[0]);
break;
case 'M':
csi_M(par[0]);
break;
case 'P':
csi_P(par[0]);
break;
case '@':
csi_at(par[0]);
break;
case 'm':
csi_m();
break;
case 'r':
if (par[0]) par[0]--;
if (!par[1]) par[1] = video_num_lines;
if (par[0] < par[1] &&
par[1] <= video_num_lines) {
top=par[0];
bottom=par[1];
}
break;
case 's':
save_cur();
break;
case 'u':
restore_cur();
break;
}
}
}
set_cursor();
}
(四)大功告成,编译运行把~
报告:
（1）在原始代码中，按下F12，中断响应后，中断服务程序会调用func？它实现的是什么功能？
将F12转义成转义字符序列 [ [ L , 对F1-F12处理类似 [ [ A -> [ [ L
（2） 在你的实现中，是否把向文件输出的字符也过滤了？如果是，那么怎么能只过滤向终端输出的字符？如果不是，那么怎么能把向文件输出的字符也一并进行过滤？
实现中并没有把向文件输出的字符也过滤，在copy_to_cooked函数处理中并不是将字符放到write_q，然后调用con_write来显示到控制台。
而是shell通过上层的sys_write系统调用将tty->secondary队列中的字符显示出来的。而在sys_write的实现过程中调用了tty_write函数。
所以只修改tty_write后，按键回显当然也变成’*’,第二次按的时候回复原来的样子;
因此要想将向文件输出的字符一并进行过滤，需要修改file_write函数。设置Flag，如果为F12按下状态，将从内核态读出的数据转为‘*’赋给用户空间即可
