切换虚拟终端0001

1、切换虚拟终端概述linux使用虚拟终端，这些虚拟终端对应/dev/tty1/dev/tty8,它们由系统初始化时打开。这个过程也在键盘的中断服务程序中完成。用户用ALT+1.8或ALT+箭头来切换终端。每个虚拟终端对应一个tty_struct和一个termios结构。Termios结构存储输入输出及控制模式，一些底层参数。Tty_struct和终端的关系如同task_struct和进程的关系。一个 tty被打开， 就对应一个tty_stract,对终端的一切处理都围绕tty_strct进行。Termios也被tty_struct的一个指针指向。当然，tty_struct和termios结构相对

2、独立，tty被完全关闭时，tty_struct也就不 在存在，而 termios 依然存在。另：1与虚拟终端相对的是实终端。它对应/dev/ttyO或/dev/c on sole二者设备号均为4,0(2. 0. 35)系统初始时tty的初始化分早期和晚期。早期初始化支持实终端，晚期初始化 支持虚拟终端。此时 /dev/tty0或/dev/console对应当前终端。2伪终端正如其名，与控制台终端除了最高层的输入输出功能类似外，底层的实现大相径庭。终端切换的流程:Keyboard, in terruptKey_ha ndler(do_c ons)Set_c on slewant_con sole

3、 = nr; mark_bh(CONSOLE_BH);static void keyboard_ in terrupt(i nt irq, void *dev_id, struct pt_regs *regs) han dle_sca ncode(sca ncode);(*key_handlertype)(keysym & Oxff, up_flag);k_hand key_handler|keyboard.c键盘特殊输入的特殊处理函数数组。static k_ha nd key_ha ndler16 = do_self, do_fn, do_spec, do_pad, do_dead, do_

4、c ons, do_cur, do_shift, do_meta, do_ascii, do_lock, do_lowercase, do_slock.do_ig nore, do_ig nore, do_ig nore ；do_cons ()改变终端的最上层函数keyboard.cstatic void do_c ons(un sig ned char value, char up_flag) if (up_flag)return;set_c on sole(value);set_console()设置wa nt_con sole为欲切换到的终端。 设置con sole的bottom hal

5、f标志。kbd_ker n.hextern in li ne void set_c on sole(i nt nr)want_con sole = nr;mark_bh(CONSOLE_BH);console_bh()con sole.cstatic void con sole_bh(void)是否要切换con soleif (want_console = 0) if (want_console != fg_console) change_console(want_console);/* we only cha nged whe n the con sole had already bee n

6、 allocated - a new con sole is not created in an in terrupt routi ne */want_con sole = -1;if (do_poke_bla nked_c on sole) /* do not un bla nk for a LED cha nge */ do_poke_bla nked_c on sole = 0; poke_bla nked_c on sole();change_console ()tty_io.c切换终端的实际动作。void cha nge_c on sole( un sig ned int n ew_

7、c on sole)if (n ew_c on sole = fg_con sole) | (vt_do nt_switch) return;if (!vc_c on s_allocated( new_c on sole)return;/*If this vt is in process mode, the n we n eed to han dshake with什么模式？在此模式下，不能直接切换，要等待!* that process before switch ing. Esse ntially, we store where that* vt wants to switch to and

8、 wait for it to tell us when its done* (via VT_RELDISP ioctl).* We also check to see if the con trolli ng process still exists.控制进程* If it does nt, we reset this vt to auto mode and continue.AAAAAAAAAA什么模式？* This is a cheap way to track process con trol. The worst thi ng* that can happe n is: we sen

9、d a sig nal to a process, it dies, and* the switch gets lost wait ing for a resp on se; hopefully, the* user will try aga in, well detect the process is gone (uni ess* the user waits just the right amount of time :-) and revert the* vt to auto con trol.*/VT_PROCESS模式的处理。在此模式下，不能直接切换，要等待！if (vt_co ns

10、fg_co nsole-vt_mode.mode = VT_PROCESS)/* Send the sig nal as privileged - kill_proc() will* tell us if the process has gone or someth ing else* is awry*/if (kill_proc(vt_c on sfg_c on sole-vt_pid,vt_con sfg_c on sole-vt_mode.relsig, 1) = 0)/* It worked. Mark the vt to switch to and* retur n. The pro

11、cess n eeds to send us a* VT_RELDISP ioctl to complete the switch. */vt_con sfg_c on sole-vt_ newvt = n ew_c on sole; return; /* The con trolli ng process has died, so we revert back to* no rmal operati on. In this case, well also cha nge back* to KD_TEXT mode. Im not sure if this is strictly correc

12、t* but it saves the ago ny whe n the X server dies and the scree n* remai ns bla nked due to KD_GRAPHICS! It would be nice to do* this outside of VT_PROCESS but there is no si ngle process* to acco unt for and track ing tty count may be un desirable.*/reset_vc(fg_c on sole);/* Fall through to normal

13、 (VT_AUTO) handling of the switch.*/在KD_GRAPHICS+VT_AUTO模式下忽略所有终端切换。if (vt_con sfg_co nsole-vc_mode = KD_GRAPHICS)return;complete_cha nge_c on sole( new_c on sole);相关函数与变量判断新的虚拟终端是否存在。int vc_c on s_allocated( un sig ned in t i)/c on sole.creturn (i vc_mode = KD_TEXT; kbd_table new_co nsole.kbdmode =

14、 VC_XLATE;vt_c onsn ew_c on sole-vt_mode.mode = VT_AUTO;vt_c onsn ew_c on sole-vt_mode.waitv = 0;vt_c onsn ew_c on sole-vt_mode.relsig = 0;vt_c onsn ew_c on sole-vt_mode.acqsig = 0;vt_c onsn ew_c on sole-vt_mode.frsig = 0;vt_c onsn ew_c on sole-vt_pid = -1;vt_c onsn ew_c on sole-vt_ newvt = -1; rese

15、t_palette (n ew_c on sole);complete_change_console()切换终端的实际动作。tty_io.cvoid complete_cha nge_c on sole( un sig ned int n ew_c on sole)un sig ned char old_vc_mode;if (n ew_c on sole = fg_con sole) | (vt_do nt_switch)return;if (!vc_c on s_allocated( new_c on sole)return;l ast_c on sole = fg_con sole;/*

16、 If were switchi ng, we could be goi ng from KD_GRAPHICS to* KD_TEXT mode or vice versa, which means we n eed to bla nk or* un bla nk the scree n later.*/old_vc_mode = vt_con sfg_c on sole-vc_mode; 根据new_console重设显示器。update_scree n(n ew_c on sole);/* If this new con sole is un der process con trol,

17、send it a sig nal* telling it that it has acquired. Also check if it has died and* clea n up (similar to logic employed in cha nge_c on sole()*/if (V_con s new_co nsole-V_mode.mode = VT_PROCESS)/* Send the signal as privileged - kill_proc() will* tell us if the process has gone or someth ing else* i

18、s awry*/if (kill_proc(vt_c onsn ew_c on sole-vt_pid,V_consn ew_c on sole-V_mode.acqsig,1) != 0)/* The con trolli ng process has died, so we revert back to* no rmal operati on. In this case, well also cha nge back* to KD_TEXT mode. Im not sure if this is strictly correct* but it saves the ago ny whe

19、n the X server dies and the scree n* remai ns bla nked due to KD_GRAPHICS! It would be nice to do* this outside of VT_PROCESS but there is no si ngle process* to acco unt for and track ing tty count may be un desirable.*/reset_vc( new_c on sole);/* We do this here because the con troll ing process a

20、bove may have* gone, and so there is now a new vc_mode*/if (old_vc_mode != vt_consn ew_c on sole-vc_mode)if (vt_c onsn ew_c on sole-vc_mode = KD_TEXT)文本模式do_un bla nk_scree n();else图形模式do_bla nk_scree n(1);/* Set the colour palette for this VT */if (vt_c onsn ew_c on sole-vc_mode = KD_TEXT)set_palet

21、te();/* Wake anyone wait ing for their VT to activate*/vt_wake_waitactive();return;相关函数与变量#defi ne vt_wake_waitactive() wake_up(&vt_activate_queue)update_screen ()con sole.c重设屏幕。void update_scree n(i nt n ew_c on sole)static int lock = 0;lock保证该函数不会被重入。if (n ew_c on sole = fg_con sole | lock)return;if (!vc_c on s_allocated( new_c on sole) /* stra nge . */prin tk(update_scree n: tty %d not allocated ?n, n ew_c on sole+1);return;l