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TTY终端的输入过程
=================
1) 当用户按压键盘时, 键盘中断处理程序将经过转换的键盘功能码用tty_insert_flip_char()放入到当前打开终端的翻转缓冲区之中, 然后将缓冲区输出任务函数(flush_to_ldisc)添加到控制台任务队列(con_task_queue)并激活控制台软中断执行该任务函数. flush_to_ldisc()翻转读写缓冲区, 将缓冲区接收数据传递给tty终端规程的n_tty_receive_buf()接收函数, n_tty_receive_buf()处理输入字符, 将输出字符缓冲在终端的循环缓冲区(read_buf)之中. 用户通过tty规程的read_chan()读取read_buf中的字符. 当多个进程同时读取同一终端时, 使用tty->atomic_read信号灯来竞争读取权.
2) 每一打开的终端接口中包含终端的参数结构(termios), 当终端打开时, 它将继承终端驱动设备参数表中参数结构, 系统缺省的终端参数为tty_std_termios, 驱动设备的初始终端参数为init_termios. 终端参数可由用户通过ioctl()调整, 用来控制终端接口的行为. c_iflag描述对输入字符的识别模式, c_oflag描述对输出字符的处理模式, c_cflag描述终端接口的控制模式, c_lflag描述字符处理过程中各种本地行为, 还有由19个字符组成的c_cc字符参数表, 描述各类控制字符以及辅助参数.
3) 当本地模式具有规范输入标志(ICANON)时, 输出数据按行拷贝给用户. 在接收到换行符(或者文件结束符c_cc[VEOF],行结束符c_cc[VEOL]和c_cc[VEOL2])之前, 可以使用编辑控制符完成简单的编辑. c_cc[VERASE]删除前一字符, c_cc[VKILL]删除整行, c_cc[VWERASE]删除前一单词.
4) 当本地模式具有回显标志(ECHO)时, 输入字符按一定的规则回显到输出设备上. 当本地模式具有信号标志(ISIG)时, 特定的输入字符可以在终端当前进程组中产生信号. c_cc[VINTR]产生中断信号, c_cc[VQUIT]产生退出信息, c_cc[VSUSP]产生暂停信号.c_cc[VTIME]定义了用户读取数据的等待超时, 单位为0.1秒, c_cc[VMIN]为所期望的字节数. 在非ICANON模式下, 如果在c_cc[VTIME]时间内接收到c_cc[VMIN]数量的字符, 读过程返回. c_cc[VSTOP]暂停驱动设备输出, c_cc[VSTART]启动驱动设备输出.
5) 内核初始化结束后, 打开控制台终端设备/dev/console作为输入输出去运行/sbin/init. /dev/console的设备号是0x0501, 在打开时被定向到命令行(console=)指定的终端设备, 缺省情况下为/dev/tty1, 其设备号为0x0401. init程序完成用户初始化完成后启动若干个终端守护程序(getty). getty在打开所守护的终端文件之前先使用setsid()创建会话组并成为会话组的首领进程(leader=1), 首领进程的会话号(session)和进程组号(pgrp)等于进程号(pid). 首领进程打开终端文件后成为终端的控制进程, 其tty指针指向该终端打开结构, 该终端也成为本次会话的控制终端, 其session号和pgrp号分别等于进程的session号和pgrp号. 当用户从终端登录后, 登录bash程序置换getty进程成为首领进程. 进程的会话号和组号随着进程的复制而传递, 子进程的首领标志复位. bash在用execve()执行用户程序之前将用setpgid()为每一程序建立属于它自已的进程组(使进程组号等于进程号), 再用对终端的(TIOCSPGRP)设备控制将终端进程组号设为将该进程号, 使终端切换到新的进程组. 终端进程组以外的进程组如果进行读操作将在其进程组中生成SIGTTIN信号, 缺省的信号处理器使进程进入暂停.
; drivers/char/keyboard.c:
void put_queue(int ch)
{
wake_up(&keypress_wait);
if (tty) {
tty_insert_flip_char(tty, ch, 0);
con_schedule_flip(tty);
}
}
static void puts_queue(char *cp)
{
wake_up(&keypress_wait);
if (!tty)
return;
while (*cp) {
tty_insert_flip_char(tty, *cp, 0);
cp++;
}
con_schedule_flip(tty);
}
_INLINE_ void tty_insert_flip_char(struct tty_struct *tty,
unsigned char ch, char flag)
{
if (tty->flip.count flip.count++;
*tty->flip.flag_buf_ptr++ = flag;
*tty->flip.char_buf_ptr++ = ch;
}
}
extern inline void con_schedule_flip(struct tty_struct *t)
{
queue_task(&t->flip.tqueue, &con_task_queue);
tasklet_schedule(&console_tasklet);
}
; drivers/char/tty_io.c:
/*
* When a break, frame error, or parity error happens, these codes are
* stuffed into the flags buffer.
*/
#define TTY_NORMAL 0
#define TTY_BREAK 1
#define TTY_FRAME 2
#define TTY_PARITY 3
#define TTY_OVERRUN 4
#define INTR_CHAR(tty) ((tty)->termios->c_cc[VINTR])
#define QUIT_CHAR(tty) ((tty)->termios->c_cc[VQUIT])
#define ERASE_CHAR(tty) ((tty)->termios->c_cc[VERASE])
#define KILL_CHAR(tty) ((tty)->termios->c_cc[VKILL])
#define EOF_CHAR(tty) ((tty)->termios->c_cc[VEOF])
#define TIME_CHAR(tty) ((tty)->termios->c_cc[VTIME])
#define MIN_CHAR(tty) ((tty)->termios->c_cc[VMIN])
#define SWTC_CHAR(tty) ((tty)->termios->c_cc[VSWTC])
#define START_CHAR(tty) ((tty)->termios->c_cc[VSTART])
#define STOP_CHAR(tty) ((tty)->termios->c_cc[VSTOP])
#define SUSP_CHAR(tty) ((tty)->termios->c_cc[VSUSP])
#define EOL_CHAR(tty) ((tty)->termios->c_cc[VEOL])
#define REPRINT_CHAR(tty) ((tty)->termios->c_cc[VREPRINT])
#define DISCARD_CHAR(tty) ((tty)->termios->c_cc[VDISCARD])
#define WERASE_CHAR(tty) ((tty)->termios->c_cc[VWERASE])
#define LNEXT_CHAR(tty) ((tty)->termios->c_cc[VLNEXT])
#define EOL2_CHAR(tty) ((tty)->termios->c_cc[VEOL2])
#define _I_FLAG(tty,f) ((tty)->termios->c_iflag & (f))
#define _O_FLAG(tty,f) ((tty)->termios->c_oflag & (f))
#define _C_FLAG(tty,f) ((tty)->termios->c_cflag & (f))
#define _L_FLAG(tty,f) ((tty)->termios->c_lflag & (f))
#define I_IGNBRK(tty) _I_FLAG((tty),IGNBRK)
#define I_BRKINT(tty) _I_FLAG((tty),BRKINT)
#define I_IGNPAR(tty) _I_FLAG((tty),IGNPAR)
#define I_PARMRK(tty) _I_FLAG((tty),PARMRK)
#define I_INPCK(tty) _I_FLAG((tty),INPCK)
#define I_ISTRIP(tty) _I_FLAG((tty),ISTRIP)
#define I_INLCR(tty) _I_FLAG((tty),INLCR)
#define I_IGNCR(tty) _I_FLAG((tty),IGNCR)
#define I_ICRNL(tty) _I_FLAG((tty),ICRNL)
#define I_IUCLC(tty) _I_FLAG((tty),IUCLC)
#define I_IXON(tty) _I_FLAG((tty),IXON)
#define I_IXANY(tty) _I_FLAG((tty),IXANY)
#define I_IXOFF(tty) _I_FLAG((tty),IXOFF)
#define I_IMAXBEL(tty) _I_FLAG((tty),IMAXBEL)
#define O_OPOST(tty) _O_FLAG((tty),OPOST)
#define O_OLCUC(tty) _O_FLAG((tty),OLCUC)
#define O_ONLCR(tty) _O_FLAG((tty),ONLCR)
#define O_OCRNL(tty) _O_FLAG((tty),OCRNL)
#define O_ONOCR(tty) _O_FLAG((tty),ONOCR)
#define O_ONLRET(tty) _O_FLAG((tty),ONLRET)
#define O_OFILL(tty) _O_FLAG((tty),OFILL)
#define O_OFDEL(tty) _O_FLAG((tty),OFDEL)
#define O_NLDLY(tty) _O_FLAG((tty),NLDLY)
#define O_CRDLY(tty) _O_FLAG((tty),CRDLY)
#define O_TABDLY(tty) _O_FLAG((tty),TABDLY)
#define O_BSDLY(tty) _O_FLAG((tty),BSDLY)
#define O_VTDLY(tty) _O_FLAG((tty),VTDLY)
#define O_FFDLY(tty) _O_FLAG((tty),FFDLY)
#define C_BAUD(tty) _C_FLAG((tty),CBAUD)
#define C_CSIZE(tty) _C_FLAG((tty),CSIZE)
#define C_CSTOPB(tty) _C_FLAG((tty),CSTOPB)
#define C_CREAD(tty) _C_FLAG((tty),CREAD)
#define C_PARENB(tty) _C_FLAG((tty),PARENB)
#define C_PARODD(tty) _C_FLAG((tty),PARODD)
#define C_HUPCL(tty) _C_FLAG((tty),HUPCL)
#define C_CLOCAL(tty) _C_FLAG((tty),CLOCAL)
#define C_CIBAUD(tty) _C_FLAG((tty),CIBAUD)
#define C_CRTSCTS(tty) _C_FLAG((tty),CRTSCTS)
#define L_ISIG(tty) _L_FLAG((tty),ISIG)
#define L_ICANON(tty) _L_FLAG((tty),ICANON)
#define L_XCASE(tty) _L_FLAG((tty),XCASE)
#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_ECHONL(tty) _L_FLAG((tty),ECHONL)
#define L_NOFLSH(tty) _L_FLAG((tty),NOFLSH)
#define L_TOSTOP(tty) _L_FLAG((tty),TOSTOP)
#define L_ECHOCTL(tty) _L_FLAG((tty),ECHOCTL)
#define L_ECHOPRT(tty) _L_FLAG((tty),ECHOPRT)
#define L_ECHOKE(tty) _L_FLAG((tty),ECHOKE)
#define L_FLUSHO(tty) _L_FLAG((tty),FLUSHO)
#define L_PENDIN(tty) _L_FLAG((tty),PENDIN)
#define L_IEXTEN(tty) _L_FLAG((tty),IEXTEN)
/* number of characters left in xmit buffer before select has we have room */
#define WAKEUP_CHARS 256
typedef unsigned char cc_t;
typedef unsigned int speed_t;
typedef unsigned int tcflag_t;
#define NCCS 19
struct termios {
tcflag_t c_iflag; /* input mode flags */
tcflag_t c_oflag; /* output mode flags */
tcflag_t c_cflag; /* control mode flags */
tcflag_t c_lflag; /* local mode flags */
cc_t c_line; /* line discipline */
cc_t c_cc[NCCS]; /* control characters */
};
/* intr=^C quit=^\ erase=del kill=^U
eof=^D vtime=\0 vmin=\1 sxtc=\0
start=^Q stop=^S susp=^Z eol=\0
reprint=^R discard=^U werase=^W lnext=^V
eol2=\0
*/
#define INIT_C_CC "\003\034\177\025\004\0\1\0\021\023\032\0\022\017\027\026\0"
/* c_cc characters */
#define VINTR 0
#define VQUIT 1
#define VERASE 2
#define VKILL 3
#define VEOF 4
#define VTIME 5
#define VMIN 6
#define VSWTC 7
#define VSTART 8
#define VSTOP 9
#define VSUSP 10
#define VEOL 11
#define VREPRINT 12
#define VDISCARD 13
#define VWERASE 14
#define VLNEXT 15
#define VEOL2 16
/* c_iflag bits */
#define IGNBRK 0000001
#define BRKINT 0000002
#define IGNPAR 0000004
#define PARMRK 0000010
#define INPCK 0000020
#define ISTRIP 0000040
#define INLCR 0000100
#define IGNCR 0000200
#define ICRNL 0000400
#define IUCLC 0001000
#define IXON 0002000
#define IXANY 0004000
#define IXOFF 0010000
#define IMAXBEL 0020000
/* c_oflag bits */
#define OPOST 0000001
#define OLCUC 0000002
#define ONLCR 0000004
#define OCRNL 0000010
#define ONOCR 0000020
#define ONLRET 0000040
#define OFILL 0000100
#define OFDEL 0000200
#define NLDLY 0000400
#define NL0 0000000
#define NL1 0000400
#define CRDLY 0003000
#define CR0 0000000
#define CR1 0001000
#define CR2 0002000
#define CR3 0003000
#define TABDLY 0014000
#define TAB0 0000000
#define TAB1 0004000
#define TAB2 0010000
#define TAB3 0014000
#define XTABS 0014000
#define BSDLY 0020000
#define BS0 0000000
#define BS1 0020000
#define VTDLY 0040000
#define VT0 0000000
#define VT1 0040000
#define FFDLY 0100000
#define FF0 0000000
#define FF1 0100000
/* c_cflag bit meaning */
#define CBAUD 0010017
#define B0 0000000 /* hang up */
#define B50 0000001
#define B75 0000002
#define B110 0000003
#define B134 0000004
#define B150 0000005
#define B200 0000006
#define B300 0000007
#define B600 0000010
#define B1200 0000011
#define B1800 0000012
#define B2400 0000013
#define B4800 0000014
#define B9600 0000015
#define B19200 0000016
#define B38400 0000017
#define EXTA B19200
#define EXTB B38400
#define CSIZE 0000060
#define CS5 0000000
#define CS6 0000020
#define CS7 0000040
#define CS8 0000060
#define CSTOPB 0000100
#define CREAD 0000200
#define PARENB 0000400
#define PARODD 0001000
#define HUPCL 0002000
#define CLOCAL 0004000
#define CBAUDEX 0010000
#define B57600 0010001
#define B115200 0010002
#define B230400 0010003
#define B460800 0010004
#define B500000 0010005
#define B576000 0010006
#define B921600 0010007
#define B1000000 0010010
#define B1152000 0010011
#define B1500000 0010012
#define B2000000 0010013
#define B2500000 0010014
#define B3000000 0010015
#define B3500000 0010016
#define B4000000 0010017
#define CIBAUD 002003600000 /* input baud rate (not used) */
#define CMSPAR 010000000000 /* mark or space (stick) parity */
#define CRTSCTS 020000000000 /* flow control */
/* c_lflag bits */
#define ISIG 0000001
#define ICANON 0000002
#define XCASE 0000004
#define ECHO 0000010
#define ECHOE 0000020
#define ECHOK 0000040
#define ECHONL 0000100
#define NOFLSH 0000200
#define TOSTOP 0000400
#define ECHOCTL 0001000
#define ECHOPRT 0002000
#define ECHOKE 0004000
#define FLUSHO 0010000
#define PENDIN 0040000
#define IEXTEN 0100000
/*
* This defines the low- and high-watermarks for throttling and
* unthrottling the TTY driver. These watermarks are used for
* controlling the space in the read buffer.
*/
#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
#define TTY_THRESHOLD_UNTHROTTLE 128
static struct file_operations tty_fops = {
llseek: tty_lseek,
read: tty_read,
write: tty_write,
poll: tty_poll,
ioctl: tty_ioctl,
open: tty_open,
release: tty_release,
fasync: tty_fasync,
};
void __init console_init(void)
{
/* Setup the default TTY line discipline. */
memset(ldiscs, 0, sizeof(ldiscs));
(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
/*
* Set up the standard termios. Individual tty drivers may
* deviate from this; this is used as a template.
*/
memset(&tty_std_termios, 0, sizeof(struct termios));
memcpy(tty_std_termios.c_cc, INIT_C_CC, NCCS);
tty_std_termios.c_iflag = ICRNL | IXON;
tty_std_termios.c_oflag = OPOST | ONLCR;
tty_std_termios.c_cflag = B38400 | CS8 | CREAD | HUPCL;
tty_std_termios.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
ECHOCTL | ECHOKE | IEXTEN;
...
}
static ssize_t tty_read(struct file * file, char * buf, size_t count,
loff_t *ppos)
{
int i;
struct tty_struct * tty;
struct inode *inode;
/* Can't seek (pread) on ttys. */
if (ppos != &file->f_pos)
return -ESPIPE;
tty = (struct tty_struct *)file->private_data;
inode = file->f_dentry->d_inode;
if (tty_paranoia_check(tty, inode->i_rdev, "tty_read")) //校验tty 结构是否完整
return -EIO;
if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
return -EIO;
/* This check not only needs to be done before reading, but also
whenever read_chan() gets woken up after sleeping, so I've
moved it to there. This should only be done for the N_TTY
line discipline, anyway. Same goes for write_chan(). -- jlc. */
#if 0
if ((inode->i_rdev != CONSOLE_DEV) && /* don't stop on /dev/console */
(tty->pgrp > 0) &&
(current->tty == tty) &&
(tty->pgrp != current->pgrp))
if (is_ignored(SIGTTIN) || is_orphaned_pgrp(current->pgrp))
return -EIO;
else {
(void) kill_pg(current->pgrp, SIGTTIN, 1);
return -ERESTARTSYS;
}
#endif
lock_kernel();
if (tty->ldisc.read)
i = (tty->ldisc.read)(tty,file,buf,count);
else
i = -EIO;
unlock_kernel();
if (i > 0)
inode->i_atime = CURRENT_TIME;
return i;
}
/*
* This routine is called out of the software interrupt to flush data
* from the flip buffer to the line discipline.
*/
static void flush_to_ldisc(void *private_)
{
struct tty_struct *tty = (struct tty_struct *) private_;
unsigned char *cp;
char *fp;
int count;
unsigned long flags;
if (test_bit(TTY_DONT_FLIP, &tty->flags)) { 如果不允许翻转读写缓冲区
queue_task(&tty->flip.tqueue, &tq_timer); 将任务延迟一个时钟中断
return;
}
if (tty->flip.buf_num) {
cp = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
fp = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
tty->flip.buf_num = 0;
save_flags(flags); cli();
tty->flip.char_buf_ptr = tty->flip.char_buf;
tty->flip.flag_buf_ptr = tty->flip.flag_buf;
} else {
cp = tty->flip.char_buf;
fp = tty->flip.flag_buf;
tty->flip.buf_num = 1;
save_flags(flags); cli();
tty->flip.char_buf_ptr = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
tty->flip.flag_buf_ptr = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
}
count = tty->flip.count;
tty->flip.count = 0;
restore_flags(flags);
tty->ldisc.receive_buf(tty, cp, fp, count);
}
void start_tty(struct tty_struct *tty)
{
if (!tty->stopped || tty->flow_stopped)
return;
tty->stopped = 0;
if (tty->link && tty->link->packet) {
tty->ctrl_status &= ~TIOCPKT_STOP;
tty->ctrl_status |= TIOCPKT_START;
wake_up_interruptible(&tty->link->read_wait);
}
if (tty->driver.start)
(tty->driver.start)(tty);
if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
tty->ldisc.write_wakeup)
(tty->ldisc.write_wakeup)(tty);
wake_up_interruptible(&tty->write_wait);
}
void stop_tty(struct tty_struct *tty)
{
if (tty->stopped)
return;
tty->stopped = 1;
if (tty->link && tty->link->packet) {
tty->ctrl_status &= ~TIOCPKT_START;
tty->ctrl_status |= TIOCPKT_STOP;
wake_up_interruptible(&tty->link->read_wait);
}
if (tty->driver.stop)
(tty->driver.stop)(tty);
}
; drivers/char/n_tty.c:
struct tty_ldisc tty_ldisc_N_TTY = {
TTY_LDISC_MAGIC, /* magic */
"n_tty", /* name */
0, /* num */
0, /* flags */
n_tty_open, /* open */
n_tty_close, /* close */
n_tty_flush_buffer, /* flush_buffer */
n_tty_chars_in_buffer, /* chars_in_buffer */
read_chan, /* read */
write_chan, /* write */
n_tty_ioctl, /* ioctl */
n_tty_set_termios, /* set_termios */
normal_poll, /* poll */
n_tty_receive_buf, /* receive_buf */
n_tty_receive_room, /* receive_room */
0 /* write_wakeup */
};
static ssize_t read_chan(struct tty_struct *tty, struct file *file,
unsigned char *buf, size_t nr)
{
unsigned char *b = buf;
DECLARE_WAITQUEUE(wait, current);
int c;
int minimum, time;
ssize_t retval = 0;
ssize_t size;
long timeout;
unsigned long flags;
do_it_again:
if (!tty->read_buf) {
printk("n_tty_read_chan: called with read_buf == NULL?!?\n");
return -EIO;
}
/* Job control check -- must be done at start and after
every sleep (POSIX.1 7.1.1.4). */
/* NOTE: not yet done after every sleep pending a thorough
check of the logic of this change. -- jlc */
/* don't stop on /dev/console */
if (file->f_dentry->d_inode->i_rdev != CONSOLE_DEV && 打开的不是/dev/tty设备
file->f_dentry->d_inode->i_rdev != SYSCONS_DEV && 打开的不是/dev/console设备
current->tty == tty) {
if (tty->pgrp pgrp pgrp != tty->pgrp) { 如果当前进程不属于终端的当前进程组
if (is_ignored(SIGTTIN) || 如果SIGTTIN信号被忽略
is_orphaned_pgrp(current->pgrp)) 如果当前进程组的父进程已退出
return -EIO;
kill_pg(current->pgrp, SIGTTIN, 1);
return -ERESTARTSYS;
}
}
minimum = time = 0;
timeout = MAX_SCHEDULE_TIMEOUT;
if (!tty->icanon) { 如果不是规范输入模式
time = (HZ / 10) * TIME_CHAR(tty); 计算超时时间, 时间字节的单位为0.1秒
minimum = MIN_CHAR(tty); 返回的最少字符数
if (minimum) {
if (time)
tty->minimum_to_wake = 1; 接收到1个字符后就唤醒
else if (!waitqueue_active(&tty->read_wait) ||
(tty->minimum_to_wake > minimum))
tty->minimum_to_wake = minimum;
} else { 如果最少返回字符为零
timeout = 0;
if (time) {
timeout = time;
time = 0;
}
tty->minimum_to_wake = minimum = 1;
}
}
if (file->f_flags & O_NONBLOCK) {
if (down_trylock(&tty->atomic_read))
return -EAGAIN;
}
else {
if (down_interruptible(&tty->atomic_read))
return -ERESTARTSYS;
}
add_wait_queue(&tty->read_wait, &wait);
set_bit(TTY_DONT_FLIP, &tty->flags); 禁止缓冲区翻转
while (nr) {
/* First test for status change. */
if (tty->packet && tty->link->ctrl_status) {
unsigned char cs;
if (b != buf)
break;
cs = tty->link->ctrl_status;
tty->link->ctrl_status = 0;
put_user(cs, b++);
nr--;
break;
}
/* This statement must be first before checking for input
so that any interrupt will set the state back to
TASK_RUNNING. */
set_current_state(TASK_INTERRUPTIBLE);
if (((minimum - (b - buf)) minimum_to_wake) &&
((minimum - (b - buf)) >= 1))
tty->minimum_to_wake = (minimum - (b - buf));
if (!input_available_p(tty, 0)) {
if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
retval = -EIO;
break;
}
if (tty_hung_up_p(file))
break;
if (!timeout)
break;
if (file->f_flags & O_NONBLOCK) {
retval = -EAGAIN;
break;
}
if (signal_pending(current)) {
retval = -ERESTARTSYS;
break;
}
clear_bit(TTY_DONT_FLIP, &tty->flags);
timeout = schedule_timeout(timeout);
set_bit(TTY_DONT_FLIP, &tty->flags);
continue;
}
current->state = TASK_RUNNING;
/* Deal with packet mode. */
if (tty->packet && b == buf) {
put_user(TIOCPKT_DATA, b++);
nr--;
}
if (tty->icanon) {
/* N.B. avoid overrun if nr == 0 */
while (nr && tty->read_cnt) {
int eol;
eol = test_and_clear_bit(tty->read_tail,
&tty->read_flags);
c = tty->read_buf[tty->read_tail];
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_tail = ((tty->read_tail+1) &
(N_TTY_BUF_SIZE-1));
tty->read_cnt--;
if (eol) {
/* this test should be redundant:
* we shouldn't be reading data if
* canon_data is 0
*/
if (--tty->canon_data canon_data = 0;
}
spin_unlock_irqrestore(&tty->read_lock, flags);
if (!eol || (c != __DISABLED_CHAR)) {
put_user(c, b++);
nr--;
}
if (eol)
break;
}
} else {
int uncopied;
uncopied = copy_from_read_buf(tty, &b, &nr);
uncopied += copy_from_read_buf(tty, &b, &nr);
if (uncopied) {
retval = -EFAULT;
break;
}
}
/* If there is enough space in the read buffer now, let the
* low-level driver know. We use n_tty_chars_in_buffer() to
* check the buffer, as it now knows about canonical mode.
* Otherwise, if the driver is throttled and the line is
* longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
* we won't get any more characters.
*/
if (n_tty_chars_in_buffer(tty) = minimum)
break;
if (time)
timeout = time;
}
clear_bit(TTY_DONT_FLIP, &tty->flags);
up(&tty->atomic_read);
remove_wait_queue(&tty->read_wait, &wait);
if (!waitqueue_active(&tty->read_wait))
tty->minimum_to_wake = minimum;
current->state = TASK_RUNNING;
size = b - buf;
if (size) {
retval = size;
if (nr)
clear_bit(TTY_PUSH, &tty->flags);
} else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
goto do_it_again;
return retval;
}
int is_ignored(int sig)
{
return (sigismember(¤t->blocked, sig) ||
current->sig->action[sig-1].sa.sa_handler == SIG_IGN);
}
static inline int input_available_p(struct tty_struct *tty, int amt)
{
if (tty->icanon) {
if (tty->canon_data)
return 1;
} else if (tty->read_cnt >= (amt ? amt : 1))
return 1;
return 0;
}
int tty_hung_up_p(struct file * filp)
{
return (filp->f_op == &hung_up_tty_fops);
}
/*
* Helper function to speed up read_chan. It is only called when
* ICANON is off; it copies characters straight from the tty queue to
* user space directly. It can be profitably called twice; once to
* drain the space from the tail pointer to the (physical) end of the
* buffer, and once to drain the space from the (physical) beginning of
* the buffer to head pointer.
*/
static inline int copy_from_read_buf(struct tty_struct *tty,
unsigned char **b,
size_t *nr)
{
int retval;
ssize_t n;
unsigned long flags;
retval = 0;
spin_lock_irqsave(&tty->read_lock, flags);
n = MIN(*nr, MIN(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail));
spin_unlock_irqrestore(&tty->read_lock, flags);
if (n) {
mb();
retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
n -= retval;
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
tty->read_cnt -= n;
spin_unlock_irqrestore(&tty->read_lock, flags);
*b += n;
*nr -= n;
}
return retval;
}
/*
* Return number of characters buffered to be delivered to user
*/
ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
{
unsigned long flags;
ssize_t n = 0;
spin_lock_irqsave(&tty->read_lock, flags);
if (!tty->icanon) {
n = tty->read_cnt;
} else if (tty->canon_data) {
n = (tty->canon_head > tty->read_tail) ?
tty->canon_head - tty->read_tail :
tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
}
spin_unlock_irqrestore(&tty->read_lock, flags);
return n;
}
/*
* Check whether to call the driver.unthrottle function.
* We test the TTY_THROTTLED bit first so that it always
* indicates the current state.
*/
static void check_unthrottle(struct tty_struct * tty)
{
if (tty->count &&
test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
tty->driver.unthrottle)
tty->driver.unthrottle(tty);
}
static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
char *fp, int count)
{
const unsigned char *p;
char *f, flags = TTY_NORMAL;
int i;
char buf[64];
unsigned long cpuflags;
if (!tty->read_buf)
return;
if (tty->real_raw) { 如果终端处于原始接收模式, 直接输出翻转缓冲区字符
spin_lock_irqsave(&tty->read_lock, cpuflags);
i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
N_TTY_BUF_SIZE - tty->read_head));
memcpy(tty->read_buf + tty->read_head, cp, i);
tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
tty->read_cnt += i;
cp += i;
count -= i;
i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
N_TTY_BUF_SIZE - tty->read_head));
memcpy(tty->read_buf + tty->read_head, cp, i);
tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
tty->read_cnt += i;
spin_unlock_irqrestore(&tty->read_lock, cpuflags);
} else {
for (i=count, p = cp, f = fp; i; i--, p++) {
if (f)
flags = *f++;
switch (flags) {
case TTY_NORMAL:
n_tty_receive_char(tty, *p);
break;
case TTY_BREAK:
n_tty_receive_break(tty);
break;
case TTY_PARITY:
case TTY_FRAME:
n_tty_receive_parity_error(tty, *p);
break;
case TTY_OVERRUN:
n_tty_receive_overrun(tty);
break;
default:
printk("%s: unknown flag %d\n",
tty_name(tty, buf), flags);
break;
}
}
if (tty->driver.flush_chars)
tty->driver.flush_chars(tty);
}
if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
kill_fasync(&tty->fasync, SIGIO, POLL_IN); 异步信号读写通知
if (waitqueue_active(&tty->read_wait))
wake_up_interruptible(&tty->read_wait);
}
/*
* Check the remaining room for the input canonicalization
* mode. We don't want to throttle the driver if we're in
* canonical mode and don't have a newline yet!
*/
if (n_tty_receive_room(tty) flags) &&
tty->driver.throttle)
tty->driver.throttle(tty); 进行节流处理
}
}
static inline void n_tty_receive_break(struct tty_struct *tty)
{
if (I_IGNBRK(tty)) 如果忽略中断字符
return;
if (I_BRKINT(tty)) { 如果中断字符产生中信号
isig(SIGINT, tty, 1); 给终端所在的进程组发送INT信号
return;
}
if (I_PARMRK(tty)) { 断点标记
put_tty_queue('\377', tty);
put_tty_queue('\0', tty);
}
put_tty_queue('\0', tty);
wake_up_interruptible(&tty->read_wait);
}
static inline void n_tty_receive_overrun(struct tty_struct *tty)
{
char buf[64];
tty->num_overrun++;
if (time_before(tty->overrun_time, jiffies - HZ)) {
printk("%s: %d input overrun(s)\n", tty_name(tty, buf),
tty->num_overrun);
tty->overrun_time = jiffies;
tty->num_overrun = 0;
}
}
static inline void n_tty_receive_parity_error(struct tty_struct *tty,
unsigned char c)
{
if (I_IGNPAR(tty)) {
return;
}
if (I_PARMRK(tty)) {
put_tty_queue('\377', tty);
put_tty_queue('\0', tty);
put_tty_queue(c, tty);
} else if (I_INPCK(tty)) 允许奇偶校验
put_tty_queue('\0', tty);
else
put_tty_queue(c, tty);
wake_up_interruptible(&tty->read_wait);
}
static int n_tty_receive_room(struct tty_struct *tty)
{
int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
/*
* If we are doing input canonicalization, and there are no
* pending newlines, let characters through without limit, so
* that erase characters will be handled. Other excess
* characters will be beeped.
*/
if (tty->icanon && !tty->canon_data)
return N_TTY_BUF_SIZE;
if (left > 0)
return left;
return 0;
}
static inline void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
{
if (tty->read_cnt read_buf[tty->read_head] = c;
tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
tty->read_cnt++;
}
}
static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
{
unsigned long flags;
if (tty->raw) {
put_tty_queue(c, tty);
return;
}
if (tty->stopped && !tty->flow_stopped &&
I_IXON(tty) && I_IXANY(tty)) { 如果软件流控制
start_tty(tty);
return;
}
if (I_ISTRIP(tty)) 如果去除字符最高位
c &= 0x7f;
if (I_IUCLC(tty) && L_IEXTEN(tty)) 如果允许小写转换扩展模式
c=tolower(c);
if (tty->closing) { 如果正在关闭终端
if (I_IXON(tty)) {
if (c == START_CHAR(tty))
start_tty(tty);
else if (c == STOP_CHAR(tty))
stop_tty(tty);
}
return;
}
/*
* If the previous character was LNEXT, or we know that this
* character is not one of the characters that we'll have to
* handle specially, do shortcut processing to speed things
* up.
*/
if (!test_bit(c, &tty->process_char_map) || tty->lnext) {
finish_erasing(tty);
tty->lnext = 0;
if (L_ECHO(tty)) { 如果输入字符回显
if (tty->read_cnt >= N_TTY_BUF_SIZE-1) { 如果输入缓冲区满
put_char('\a', tty); /* beep if no space */ 向显示终端发送响铃字符
return;
}
/* Record the column of first canon char. */
if (tty->canon_head == tty->read_head)
tty->canon_column = tty->column;
echo_char(c, tty);
}
if (I_PARMRK(tty) && c == (unsigned char) '\377')
put_tty_queue(c, tty);
put_tty_queue(c, tty);
return;
}
if (c == '\r') {
if (I_IGNCR(tty)) 忽略回车符
return;
if (I_ICRNL(tty)) 回车转换为换行符
c = '\n';
} else if (c == '\n' && I_INLCR(tty)) 换行符转换成回车符
c = '\r';
if (I_IXON(tty)) { 如果为软件流控
if (c == START_CHAR(tty)) { 如果为启动字符
start_tty(tty); 打开终端
return;
}
if (c == STOP_CHAR(tty)) { 如果为停止字符
stop_tty(tty); 暂停终端
return;
}
}
if (L_ISIG(tty)) { 如果允许触发信号
int signal;
signal = SIGINT;
if (c == INTR_CHAR(tty)) 如果为中断字符
goto send_signal;
signal = SIGQUIT;
if (c == QUIT_CHAR(tty)) 如果为退出字符
goto send_signal;
signal = SIGTSTP;
if (c == SUSP_CHAR(tty)) { 如果为暂停字符
send_signal:
isig(signal, tty, 0); 向终端所在的进程组发送相应的信号
return;
}
}
if (tty->icanon) {
if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
(c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
eraser(c, tty);
return;
}
if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
tty->lnext = 1;
if (L_ECHO(tty)) {
finish_erasing(tty);
if (L_ECHOCTL(tty)) {
put_char('^', tty);
put_char('\b', tty);
}
}
return;
}
if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
L_IEXTEN(tty)) {
unsigned long tail = tty->canon_head;
finish_erasing(tty);
echo_char(c, tty);
opost('\n', tty);
while (tail != tty->read_head) {
echo_char(tty->read_buf[tail], tty);
tail = (tail+1) & (N_TTY_BUF_SIZE-1);
}
return;
}
if (c == '\n') {
if (L_ECHO(tty) || L_ECHONL(tty)) {
if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
put_char('\a', tty);
return;
}
opost('\n', tty);
}
goto handle_newline;
}
if (c == EOF_CHAR(tty)) {
if (tty->canon_head != tty->read_head)
set_bit(TTY_PUSH, &tty->flags);
c = __DISABLED_CHAR;
goto handle_newline;
}
if ((c == EOL_CHAR(tty)) ||
(c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
/*
* XXX are EOL_CHAR and EOL2_CHAR echoed?!?
*/
if (L_ECHO(tty)) {
if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
put_char('\a', tty);
return;
}
/* Record the column of first canon char. */
if (tty->canon_head == tty->read_head)
tty->canon_column = tty->column;
echo_char(c, tty);
}
/*
* XXX does PARMRK doubling happen for
* EOL_CHAR and EOL2_CHAR?
*/
if (I_PARMRK(tty) && c == (unsigned char) '\377')
put_tty_queue(c, tty);
handle_newline:
spin_lock_irqsave(&tty->read_lock, flags);
set_bit(tty->read_head, &tty->read_flags);
put_tty_queue_nolock(c, tty);
tty->canon_head = tty->read_head;
tty->canon_data++;
spin_unlock_irqrestore(&tty->read_lock, flags);
kill_fasync(&tty->fasync, SIGIO, POLL_IN);
if (waitqueue_active(&tty->read_wait))
wake_up_interruptible(&tty->read_wait);
return;
}
}
finish_erasing(tty);
if (L_ECHO(tty)) {
if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
put_char('\a', tty); /* beep if no space */
return;
}
if (c == '\n')
opost('\n', tty);
else {
/* Record the column of first canon char. */
if (tty->canon_head == tty->read_head)
tty->canon_column = tty->column;
echo_char(c, tty);
}
}
if (I_PARMRK(tty) && c == (unsigned char) '\377')
put_tty_queue(c, tty);
put_tty_queue(c, tty);
}
static inline void put_char(unsigned char c, struct tty_struct *tty)
{
tty->driver.put_char(tty, c);
}
/* Must be called only when L_ECHO(tty) is true. */
static void echo_char(unsigned char c, struct tty_struct *tty)
{
if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
put_char('^', tty); 回显控制字符
put_char(c ^ 0100, tty);
tty->column += 2;
} else
opost(c, tty); 回显字符
}
static inline void finish_erasing(struct tty_struct *tty)
{
if (tty->erasing) {
put_char('/', tty);
tty->column += 2;
tty->erasing = 0;
}
}
static inline void isig(int sig, struct tty_struct *tty, int flush)
{
if (tty->pgrp > 0)
kill_pg(tty->pgrp, sig, 1);
if (flush || !L_NOFLSH(tty)) {
n_tty_flush_buffer(tty);
if (tty->driver.flush_buffer)
tty->driver.flush_buffer(tty);
}
}
static void eraser(unsigned char c, struct tty_struct *tty)
{
enum { ERASE, WERASE, KILL } kill_type;
int head, seen_alnums;
unsigned long flags;
if (tty->read_head == tty->canon_head) { 如果输入为空
/* opost('\a', tty); */ /* what do you think? */
return;
}
if (c == ERASE_CHAR(tty))
kill_type = ERASE;
else if (c == WERASE_CHAR(tty))
kill_type = WERASE;
else {
if (!L_ECHO(tty)) { 如果禁止回显
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_cnt -= ((tty->read_head - tty->canon_head) &
(N_TTY_BUF_SIZE - 1));
tty->read_head = tty->canon_head;
spin_unlock_irqrestore(&tty->read_lock, flags);
return;
}
if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_cnt -= ((tty->read_head - tty->canon_head) &
(N_TTY_BUF_SIZE - 1));
tty->read_head = tty->canon_head;
spin_unlock_irqrestore(&tty->read_lock, flags);
finish_erasing(tty);
echo_char(KILL_CHAR(tty), tty);
/* Add a newline if ECHOK is on and ECHOKE is off. */
if (L_ECHOK(tty))
opost('\n', tty);
return;
}
kill_type = KILL;
}
seen_alnums = 0;
while (tty->read_head != tty->canon_head) {
head = (tty->read_head - 1) & (N_TTY_BUF_SIZE-1);
c = tty->read_buf[head];
if (kill_type == WERASE) {
/* Equivalent to BSD's ALTWERASE. */
if (isalnum(c) || c == '_')
seen_alnums++;
else if (seen_alnums)
break;
}
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_head = head;
tty->read_cnt--;
spin_unlock_irqrestore(&tty->read_lock, flags);
if (L_ECHO(tty)) {
if (L_ECHOPRT(tty)) {
if (!tty->erasing) {
put_char('\\', tty);
tty->column++;
tty->erasing = 1;
}
echo_char(c, tty);
} else if (kill_type == ERASE && !L_ECHOE(tty)) {
echo_char(ERASE_CHAR(tty), tty);
} else if (c == '\t') {
unsigned int col = tty->canon_column;
unsigned long tail = tty->canon_head;
/* Find the column of the last char. */
while (tail != tty->read_head) {
c = tty->read_buf[tail];
if (c == '\t')
col = (col | 7) + 1;
else if (iscntrl(c)) {
if (L_ECHOCTL(tty))
col += 2;
} else
col++;
tail = (tail+1) & (N_TTY_BUF_SIZE-1);
}
/* should never happen */
if (tty->column > 0x80000000)
tty->column = 0;
/* Now backup to that column. */
while (tty->column > col) {
/* Can't use opost here. */
put_char('\b', tty);
if (tty->column > 0)
tty->column--;
}
} else {
if (iscntrl(c) && L_ECHOCTL(tty)) {
put_char('\b', tty);
put_char(' ', tty);
put_char('\b', tty);
if (tty->column > 0)
tty->column--;
}
if (!iscntrl(c) || L_ECHOCTL(tty)) {
put_char('\b', tty);
put_char(' ', tty);
put_char('\b', tty);
if (tty->column > 0)
tty->column--;
}
}
}
if (kill_type == ERASE)
break;
}
if (tty->read_head == tty->canon_head)
finish_erasing(tty);
}
/*
* Perform OPOST processing. Returns -1 when the output device is
* full and the character must be retried.
*/
static int opost(unsigned char c, struct tty_struct *tty) 输出预处理
{
int space, spaces;
space = tty->driver.write_room(tty); 取输出设备剩余缓冲区空间
if (!space)
return -1;
if (O_OPOST(tty)) { 如果允许输出预处理
switch (c) {
case '\n':
if (O_ONLRET(tty)) 换行时是否回车
tty->column = 0;
if (O_ONLCR(tty)) {
if (space driver.put_char(tty, '\r');
tty->column = 0;
}
tty->canon_column = tty->column;
break;
case '\r':
if (O_ONOCR(tty) && tty->column == 0) 禁止重复输出回车符
return 0;
if (O_OCRNL(tty)) { 回车符转换为换行符
c = '\n';
if (O_ONLRET(tty))
tty->canon_column = tty->column = 0;
break;
}
tty->canon_column = tty->column = 0;
break;
case '\t':
spaces = 8 - (tty->column & 7);
if (O_TABDLY(tty) == XTABS) {
if (space column += spaces;
tty->driver.write(tty, 0, " ", spaces);
return 0;
}
tty->column += spaces;
break;
case '\b':
if (tty->column > 0)
tty->column--; 退格
break;
default:
if (O_OLCUC(tty)) 小写转换成大写
c = toupper(c);
if (!iscntrl(c)) 如果不是控制符
tty->column++;
break;
}
}
tty->driver.put_char(tty, c);
return 0;
}
/*
* Reset the read buffer counters, clear the flags,
* and make sure the driver is unthrottled. Called
* from n_tty_open() and n_tty_flush_buffer().
*/
static void reset_buffer_flags(struct tty_struct *tty)
{
unsigned long flags;
spin_lock_irqsave(&tty->read_lock, flags);
tty->read_head = tty->read_tail = tty->read_cnt = 0;
spin_unlock_irqrestore(&tty->read_lock, flags);
tty->canon_head = tty->canon_data = tty->erasing = 0;
memset(&tty->read_flags, 0, sizeof tty->read_flags);
check_unthrottle(tty);
}
static int n_tty_open(struct tty_struct *tty)
{
if (!tty)
return -EINVAL;
if (!tty->read_buf) {
tty->read_buf = alloc_buf();
if (!tty->read_buf)
return -ENOMEM;
}
memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
reset_buffer_flags(tty);
tty->column = 0;
n_tty_set_termios(tty, 0);
tty->minimum_to_wake = 1;
tty->closing = 0;
return 0;
}
/*
* This character is the same as _POSIX_VDISABLE: it cannot be used as
* a c_cc[] character, but indicates that a particular special character
* isn't in use (eg VINTR has no character etc)
*/
#define __DISABLED_CHAR '\0'
static void n_tty_set_termios(struct tty_struct *tty, struct termios * old)
{
if (!tty)
return;
tty->icanon = (L_ICANON(tty) != 0);
if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
tty->raw = 1;
tty->real_raw = 1;
return;
}
if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
I_PARMRK(tty)) {
cli();
memset(tty->process_char_map, 0, 256/8);
if (I_IGNCR(tty) || I_ICRNL(tty))
set_bit('\r', &tty->process_char_map);
if (I_INLCR(tty))
set_bit('\n', &tty->process_char_map);
if (L_ICANON(tty)) {
set_bit(ERASE_CHAR(tty), &tty->process_char_map);
set_bit(KILL_CHAR(tty), &tty->process_char_map);
set_bit(EOF_CHAR(tty), &tty->process_char_map);
set_bit('\n', &tty->process_char_map);
set_bit(EOL_CHAR(tty), &tty->process_char_map);
if (L_IEXTEN(tty)) {
set_bit(WERASE_CHAR(tty),
&tty->process_char_map);
set_bit(LNEXT_CHAR(tty),
&tty->process_char_map);
set_bit(EOL2_CHAR(tty),
&tty->process_char_map);
if (L_ECHO(tty))
set_bit(REPRINT_CHAR(tty),
&tty->process_char_map);
}
}
if (I_IXON(tty)) {
set_bit(START_CHAR(tty), &tty->process_char_map);
set_bit(STOP_CHAR(tty), &tty->process_char_map);
}
if (L_ISIG(tty)) {
set_bit(INTR_CHAR(tty), &tty->process_char_map);
set_bit(QUIT_CHAR(tty), &tty->process_char_map);
set_bit(SUSP_CHAR(tty), &tty->process_char_map);
}
clear_bit(__DISABLED_CHAR, &tty->process_char_map);
sti();
tty->raw = 0;
tty->real_raw = 0;
} else {
tty->raw = 1;
if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
(I_IGNPAR(tty) || !I_INPCK(tty)) &&
(tty->driver.flags & TTY_DRIVER_REAL_RAW))
tty->real_raw = 1;
else
tty->real_raw = 0;
}
}
本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u3/104386/showart_2165045.html |
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发表于 2010-01-30 17:54