816 lines
18 KiB
C
816 lines
18 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Provide access to virtual console memory.
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* /dev/vcs: the screen as it is being viewed right now (possibly scrolled)
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* /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
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* [minor: N]
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*
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* /dev/vcsaN: idem, but including attributes, and prefixed with
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* the 4 bytes lines,columns,x,y (as screendump used to give).
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* Attribute/character pair is in native endianity.
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* [minor: N+128]
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*
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* /dev/vcsuN: similar to /dev/vcsaN but using 4-byte unicode values
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* instead of 1-byte screen glyph values.
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* [minor: N+64]
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*
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* /dev/vcsuaN: same idea as /dev/vcsaN for unicode (not yet implemented).
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*
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* This replaces screendump and part of selection, so that the system
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* administrator can control access using file system permissions.
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*
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* aeb@cwi.nl - efter Friedas begravelse - 950211
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*
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* machek@k332.feld.cvut.cz - modified not to send characters to wrong console
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* - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
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* - making it shorter - scr_readw are macros which expand in PRETTY long code
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*/
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/errno.h>
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#include <linux/export.h>
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#include <linux/tty.h>
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#include <linux/interrupt.h>
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#include <linux/mm.h>
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#include <linux/init.h>
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#include <linux/vt_kern.h>
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#include <linux/selection.h>
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#include <linux/kbd_kern.h>
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#include <linux/console.h>
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#include <linux/device.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/poll.h>
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#include <linux/signal.h>
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#include <linux/slab.h>
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#include <linux/notifier.h>
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#include <linux/uaccess.h>
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#include <asm/byteorder.h>
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#include <asm/unaligned.h>
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#define HEADER_SIZE 4u
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#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
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/*
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* Our minor space:
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*
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* 0 ... 63 glyph mode without attributes
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* 64 ... 127 unicode mode without attributes
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* 128 ... 191 glyph mode with attributes
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* 192 ... 255 unused (reserved for unicode with attributes)
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*
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* This relies on MAX_NR_CONSOLES being <= 63, meaning 63 actual consoles
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* with minors 0, 64, 128 and 192 being proxies for the foreground console.
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*/
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#if MAX_NR_CONSOLES > 63
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#warning "/dev/vcs* devices may not accommodate more than 63 consoles"
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#endif
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#define console(inode) (iminor(inode) & 63)
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#define use_unicode(inode) (iminor(inode) & 64)
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#define use_attributes(inode) (iminor(inode) & 128)
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struct vcs_poll_data {
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struct notifier_block notifier;
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unsigned int cons_num;
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int event;
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wait_queue_head_t waitq;
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struct fasync_struct *fasync;
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};
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static int
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vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
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{
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struct vt_notifier_param *param = _param;
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struct vc_data *vc = param->vc;
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struct vcs_poll_data *poll =
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container_of(nb, struct vcs_poll_data, notifier);
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int currcons = poll->cons_num;
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int fa_band;
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switch (code) {
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case VT_UPDATE:
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fa_band = POLL_PRI;
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break;
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case VT_DEALLOCATE:
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fa_band = POLL_HUP;
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break;
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default:
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return NOTIFY_DONE;
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}
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if (currcons == 0)
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currcons = fg_console;
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else
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currcons--;
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if (currcons != vc->vc_num)
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return NOTIFY_DONE;
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poll->event = code;
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wake_up_interruptible(&poll->waitq);
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kill_fasync(&poll->fasync, SIGIO, fa_band);
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return NOTIFY_OK;
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}
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static void
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vcs_poll_data_free(struct vcs_poll_data *poll)
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{
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unregister_vt_notifier(&poll->notifier);
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kfree(poll);
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}
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static struct vcs_poll_data *
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vcs_poll_data_get(struct file *file)
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{
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struct vcs_poll_data *poll = file->private_data, *kill = NULL;
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if (poll)
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return poll;
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poll = kzalloc(sizeof(*poll), GFP_KERNEL);
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if (!poll)
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return NULL;
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poll->cons_num = console(file_inode(file));
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init_waitqueue_head(&poll->waitq);
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poll->notifier.notifier_call = vcs_notifier;
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/*
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* In order not to lose any update event, we must pretend one might
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* have occurred before we have a chance to register our notifier.
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* This is also how user space has come to detect which kernels
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* support POLLPRI on /dev/vcs* devices i.e. using poll() with
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* POLLPRI and a zero timeout.
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*/
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poll->event = VT_UPDATE;
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if (register_vt_notifier(&poll->notifier) != 0) {
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kfree(poll);
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return NULL;
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}
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/*
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* This code may be called either through ->poll() or ->fasync().
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* If we have two threads using the same file descriptor, they could
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* both enter this function, both notice that the structure hasn't
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* been allocated yet and go ahead allocating it in parallel, but
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* only one of them must survive and be shared otherwise we'd leak
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* memory with a dangling notifier callback.
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*/
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spin_lock(&file->f_lock);
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if (!file->private_data) {
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file->private_data = poll;
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} else {
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/* someone else raced ahead of us */
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kill = poll;
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poll = file->private_data;
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}
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spin_unlock(&file->f_lock);
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if (kill)
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vcs_poll_data_free(kill);
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return poll;
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}
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/**
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* vcs_vc -- return VC for @inode
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* @inode: inode for which to return a VC
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* @viewed: returns whether this console is currently foreground (viewed)
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*
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* Must be called with console_lock.
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*/
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static struct vc_data *vcs_vc(struct inode *inode, bool *viewed)
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{
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unsigned int currcons = console(inode);
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WARN_CONSOLE_UNLOCKED();
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if (currcons == 0) {
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currcons = fg_console;
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if (viewed)
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*viewed = true;
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} else {
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currcons--;
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if (viewed)
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*viewed = false;
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}
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return vc_cons[currcons].d;
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}
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/**
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* vcs_size -- return size for a VC in @vc
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* @vc: which VC
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* @attr: does it use attributes?
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* @unicode: is it unicode?
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*
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* Must be called with console_lock.
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*/
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static int vcs_size(const struct vc_data *vc, bool attr, bool unicode)
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{
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int size;
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WARN_CONSOLE_UNLOCKED();
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size = vc->vc_rows * vc->vc_cols;
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if (attr) {
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if (unicode)
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return -EOPNOTSUPP;
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size = 2 * size + HEADER_SIZE;
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} else if (unicode)
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size *= 4;
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return size;
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}
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static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
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{
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struct inode *inode = file_inode(file);
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struct vc_data *vc;
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int size;
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console_lock();
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vc = vcs_vc(inode, NULL);
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if (!vc) {
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console_unlock();
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return -ENXIO;
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}
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size = vcs_size(vc, use_attributes(inode), use_unicode(inode));
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console_unlock();
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if (size < 0)
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return size;
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return fixed_size_llseek(file, offset, orig, size);
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}
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static int vcs_read_buf_uni(struct vc_data *vc, char *con_buf,
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unsigned int pos, unsigned int count, bool viewed)
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{
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unsigned int nr, row, col, maxcol = vc->vc_cols;
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int ret;
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ret = vc_uniscr_check(vc);
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if (ret)
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return ret;
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pos /= 4;
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row = pos / maxcol;
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col = pos % maxcol;
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nr = maxcol - col;
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do {
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if (nr > count / 4)
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nr = count / 4;
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vc_uniscr_copy_line(vc, con_buf, viewed, row, col, nr);
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con_buf += nr * 4;
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count -= nr * 4;
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row++;
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col = 0;
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nr = maxcol;
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} while (count);
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return 0;
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}
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static void vcs_read_buf_noattr(const struct vc_data *vc, char *con_buf,
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unsigned int pos, unsigned int count, bool viewed)
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{
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u16 *org;
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unsigned int col, maxcol = vc->vc_cols;
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org = screen_pos(vc, pos, viewed);
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col = pos % maxcol;
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pos += maxcol - col;
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while (count-- > 0) {
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*con_buf++ = (vcs_scr_readw(vc, org++) & 0xff);
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if (++col == maxcol) {
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org = screen_pos(vc, pos, viewed);
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col = 0;
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pos += maxcol;
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}
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}
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}
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static unsigned int vcs_read_buf(const struct vc_data *vc, char *con_buf,
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unsigned int pos, unsigned int count, bool viewed,
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unsigned int *skip)
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{
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u16 *org, *con_buf16;
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unsigned int col, maxcol = vc->vc_cols;
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unsigned int filled = count;
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if (pos < HEADER_SIZE) {
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/* clamp header values if they don't fit */
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con_buf[0] = min(vc->vc_rows, 0xFFu);
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con_buf[1] = min(vc->vc_cols, 0xFFu);
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getconsxy(vc, con_buf + 2);
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*skip += pos;
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count += pos;
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if (count > CON_BUF_SIZE) {
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count = CON_BUF_SIZE;
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filled = count - pos;
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}
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/* Advance state pointers and move on. */
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count -= min(HEADER_SIZE, count);
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pos = HEADER_SIZE;
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con_buf += HEADER_SIZE;
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/* If count >= 0, then pos is even... */
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} else if (pos & 1) {
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/*
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* Skip first byte for output if start address is odd. Update
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* region sizes up/down depending on free space in buffer.
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*/
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(*skip)++;
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if (count < CON_BUF_SIZE)
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count++;
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else
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filled--;
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}
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if (!count)
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return filled;
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pos -= HEADER_SIZE;
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pos /= 2;
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col = pos % maxcol;
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org = screen_pos(vc, pos, viewed);
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pos += maxcol - col;
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/*
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* Buffer has even length, so we can always copy character + attribute.
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* We do not copy last byte to userspace if count is odd.
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*/
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count = (count + 1) / 2;
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con_buf16 = (u16 *)con_buf;
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while (count) {
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*con_buf16++ = vcs_scr_readw(vc, org++);
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count--;
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if (++col == maxcol) {
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org = screen_pos(vc, pos, viewed);
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col = 0;
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pos += maxcol;
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}
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}
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return filled;
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}
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static ssize_t
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vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
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struct inode *inode = file_inode(file);
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struct vc_data *vc;
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struct vcs_poll_data *poll;
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unsigned int read;
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ssize_t ret;
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char *con_buf;
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loff_t pos;
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bool viewed, attr, uni_mode;
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con_buf = (char *) __get_free_page(GFP_KERNEL);
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if (!con_buf)
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return -ENOMEM;
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pos = *ppos;
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/* Select the proper current console and verify
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* sanity of the situation under the console lock.
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*/
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console_lock();
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uni_mode = use_unicode(inode);
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attr = use_attributes(inode);
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ret = -ENXIO;
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vc = vcs_vc(inode, &viewed);
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if (!vc)
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goto unlock_out;
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ret = -EINVAL;
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if (pos < 0)
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goto unlock_out;
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/* we enforce 32-bit alignment for pos and count in unicode mode */
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if (uni_mode && (pos | count) & 3)
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goto unlock_out;
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poll = file->private_data;
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if (count && poll)
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poll->event = 0;
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read = 0;
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ret = 0;
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while (count) {
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unsigned int this_round, skip = 0;
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int size;
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/* Check whether we are above size each round,
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* as copy_to_user at the end of this loop
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* could sleep.
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*/
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size = vcs_size(vc, attr, uni_mode);
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if (size < 0) {
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if (read)
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break;
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ret = size;
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goto unlock_out;
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}
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if (pos >= size)
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break;
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if (count > size - pos)
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count = size - pos;
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this_round = count;
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if (this_round > CON_BUF_SIZE)
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this_round = CON_BUF_SIZE;
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/* Perform the whole read into the local con_buf.
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* Then we can drop the console spinlock and safely
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* attempt to move it to userspace.
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*/
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if (uni_mode) {
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ret = vcs_read_buf_uni(vc, con_buf, pos, this_round,
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viewed);
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if (ret)
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break;
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} else if (!attr) {
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vcs_read_buf_noattr(vc, con_buf, pos, this_round,
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viewed);
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} else {
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this_round = vcs_read_buf(vc, con_buf, pos, this_round,
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viewed, &skip);
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}
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/* Finally, release the console semaphore while we push
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* all the data to userspace from our temporary buffer.
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*
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* AKPM: Even though it's a semaphore, we should drop it because
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* the pagefault handling code may want to call printk().
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*/
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console_unlock();
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ret = copy_to_user(buf, con_buf + skip, this_round);
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console_lock();
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if (ret) {
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read += this_round - ret;
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ret = -EFAULT;
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break;
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}
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buf += this_round;
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pos += this_round;
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read += this_round;
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count -= this_round;
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}
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*ppos += read;
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if (read)
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ret = read;
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unlock_out:
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console_unlock();
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free_page((unsigned long) con_buf);
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return ret;
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}
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static u16 *vcs_write_buf_noattr(struct vc_data *vc, const char *con_buf,
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unsigned int pos, unsigned int count, bool viewed, u16 **org0)
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{
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u16 *org;
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unsigned int col, maxcol = vc->vc_cols;
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*org0 = org = screen_pos(vc, pos, viewed);
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col = pos % maxcol;
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pos += maxcol - col;
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while (count > 0) {
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unsigned char c = *con_buf++;
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count--;
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vcs_scr_writew(vc,
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(vcs_scr_readw(vc, org) & 0xff00) | c, org);
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org++;
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if (++col == maxcol) {
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org = screen_pos(vc, pos, viewed);
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col = 0;
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pos += maxcol;
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}
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}
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return org;
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}
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/*
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* Compilers (gcc 10) are unable to optimize the swap in cpu_to_le16. So do it
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* the poor man way.
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*/
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static inline u16 vc_compile_le16(u8 hi, u8 lo)
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{
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#ifdef __BIG_ENDIAN
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return (lo << 8u) | hi;
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#else
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return (hi << 8u) | lo;
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#endif
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}
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static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf,
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unsigned int pos, unsigned int count, bool viewed, u16 **org0)
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{
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u16 *org;
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unsigned int col, maxcol = vc->vc_cols;
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unsigned char c;
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/* header */
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if (pos < HEADER_SIZE) {
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char header[HEADER_SIZE];
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getconsxy(vc, header + 2);
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while (pos < HEADER_SIZE && count > 0) {
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count--;
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header[pos++] = *con_buf++;
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}
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if (!viewed)
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putconsxy(vc, header + 2);
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}
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if (!count)
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return NULL;
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pos -= HEADER_SIZE;
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col = (pos/2) % maxcol;
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*org0 = org = screen_pos(vc, pos/2, viewed);
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/* odd pos -- the first single character */
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if (pos & 1) {
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count--;
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c = *con_buf++;
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vcs_scr_writew(vc, vc_compile_le16(c, vcs_scr_readw(vc, org)),
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org);
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org++;
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pos++;
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if (++col == maxcol) {
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|
org = screen_pos(vc, pos/2, viewed);
|
|
col = 0;
|
|
}
|
|
}
|
|
|
|
pos /= 2;
|
|
pos += maxcol - col;
|
|
|
|
/* even pos -- handle attr+character pairs */
|
|
while (count > 1) {
|
|
unsigned short w;
|
|
|
|
w = get_unaligned(((unsigned short *)con_buf));
|
|
vcs_scr_writew(vc, w, org++);
|
|
con_buf += 2;
|
|
count -= 2;
|
|
if (++col == maxcol) {
|
|
org = screen_pos(vc, pos, viewed);
|
|
col = 0;
|
|
pos += maxcol;
|
|
}
|
|
}
|
|
|
|
if (!count)
|
|
return org;
|
|
|
|
/* odd pos -- the remaining character */
|
|
c = *con_buf++;
|
|
vcs_scr_writew(vc, vc_compile_le16(vcs_scr_readw(vc, org) >> 8, c),
|
|
org);
|
|
|
|
return org;
|
|
}
|
|
|
|
static ssize_t
|
|
vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
|
|
{
|
|
struct inode *inode = file_inode(file);
|
|
struct vc_data *vc;
|
|
char *con_buf;
|
|
u16 *org0, *org;
|
|
unsigned int written;
|
|
int size;
|
|
ssize_t ret;
|
|
loff_t pos;
|
|
bool viewed, attr;
|
|
|
|
if (use_unicode(inode))
|
|
return -EOPNOTSUPP;
|
|
|
|
con_buf = (char *) __get_free_page(GFP_KERNEL);
|
|
if (!con_buf)
|
|
return -ENOMEM;
|
|
|
|
pos = *ppos;
|
|
|
|
/* Select the proper current console and verify
|
|
* sanity of the situation under the console lock.
|
|
*/
|
|
console_lock();
|
|
|
|
attr = use_attributes(inode);
|
|
ret = -ENXIO;
|
|
vc = vcs_vc(inode, &viewed);
|
|
if (!vc)
|
|
goto unlock_out;
|
|
|
|
size = vcs_size(vc, attr, false);
|
|
if (size < 0) {
|
|
ret = size;
|
|
goto unlock_out;
|
|
}
|
|
ret = -EINVAL;
|
|
if (pos < 0 || pos > size)
|
|
goto unlock_out;
|
|
if (count > size - pos)
|
|
count = size - pos;
|
|
written = 0;
|
|
while (count) {
|
|
unsigned int this_round = count;
|
|
|
|
if (this_round > CON_BUF_SIZE)
|
|
this_round = CON_BUF_SIZE;
|
|
|
|
/* Temporarily drop the console lock so that we can read
|
|
* in the write data from userspace safely.
|
|
*/
|
|
console_unlock();
|
|
ret = copy_from_user(con_buf, buf, this_round);
|
|
console_lock();
|
|
|
|
if (ret) {
|
|
this_round -= ret;
|
|
if (!this_round) {
|
|
/* Abort loop if no data were copied. Otherwise
|
|
* fail with -EFAULT.
|
|
*/
|
|
if (written)
|
|
break;
|
|
ret = -EFAULT;
|
|
goto unlock_out;
|
|
}
|
|
}
|
|
|
|
/* The vcs_size might have changed while we slept to grab
|
|
* the user buffer, so recheck.
|
|
* Return data written up to now on failure.
|
|
*/
|
|
size = vcs_size(vc, attr, false);
|
|
if (size < 0) {
|
|
if (written)
|
|
break;
|
|
ret = size;
|
|
goto unlock_out;
|
|
}
|
|
if (pos >= size)
|
|
break;
|
|
if (this_round > size - pos)
|
|
this_round = size - pos;
|
|
|
|
/* OK, now actually push the write to the console
|
|
* under the lock using the local kernel buffer.
|
|
*/
|
|
|
|
if (attr)
|
|
org = vcs_write_buf(vc, con_buf, pos, this_round,
|
|
viewed, &org0);
|
|
else
|
|
org = vcs_write_buf_noattr(vc, con_buf, pos, this_round,
|
|
viewed, &org0);
|
|
|
|
count -= this_round;
|
|
written += this_round;
|
|
buf += this_round;
|
|
pos += this_round;
|
|
if (org)
|
|
update_region(vc, (unsigned long)(org0), org - org0);
|
|
}
|
|
*ppos += written;
|
|
ret = written;
|
|
if (written)
|
|
vcs_scr_updated(vc);
|
|
|
|
unlock_out:
|
|
console_unlock();
|
|
free_page((unsigned long) con_buf);
|
|
return ret;
|
|
}
|
|
|
|
static __poll_t
|
|
vcs_poll(struct file *file, poll_table *wait)
|
|
{
|
|
struct vcs_poll_data *poll = vcs_poll_data_get(file);
|
|
__poll_t ret = DEFAULT_POLLMASK|EPOLLERR;
|
|
|
|
if (poll) {
|
|
poll_wait(file, &poll->waitq, wait);
|
|
switch (poll->event) {
|
|
case VT_UPDATE:
|
|
ret = DEFAULT_POLLMASK|EPOLLPRI;
|
|
break;
|
|
case VT_DEALLOCATE:
|
|
ret = DEFAULT_POLLMASK|EPOLLHUP|EPOLLERR;
|
|
break;
|
|
case 0:
|
|
ret = DEFAULT_POLLMASK;
|
|
break;
|
|
}
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
static int
|
|
vcs_fasync(int fd, struct file *file, int on)
|
|
{
|
|
struct vcs_poll_data *poll = file->private_data;
|
|
|
|
if (!poll) {
|
|
/* don't allocate anything if all we want is disable fasync */
|
|
if (!on)
|
|
return 0;
|
|
poll = vcs_poll_data_get(file);
|
|
if (!poll)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
return fasync_helper(fd, file, on, &poll->fasync);
|
|
}
|
|
|
|
static int
|
|
vcs_open(struct inode *inode, struct file *filp)
|
|
{
|
|
unsigned int currcons = console(inode);
|
|
bool attr = use_attributes(inode);
|
|
bool uni_mode = use_unicode(inode);
|
|
int ret = 0;
|
|
|
|
/* we currently don't support attributes in unicode mode */
|
|
if (attr && uni_mode)
|
|
return -EOPNOTSUPP;
|
|
|
|
console_lock();
|
|
if(currcons && !vc_cons_allocated(currcons-1))
|
|
ret = -ENXIO;
|
|
console_unlock();
|
|
return ret;
|
|
}
|
|
|
|
static int vcs_release(struct inode *inode, struct file *file)
|
|
{
|
|
struct vcs_poll_data *poll = file->private_data;
|
|
|
|
if (poll)
|
|
vcs_poll_data_free(poll);
|
|
return 0;
|
|
}
|
|
|
|
static const struct file_operations vcs_fops = {
|
|
.llseek = vcs_lseek,
|
|
.read = vcs_read,
|
|
.write = vcs_write,
|
|
.poll = vcs_poll,
|
|
.fasync = vcs_fasync,
|
|
.open = vcs_open,
|
|
.release = vcs_release,
|
|
};
|
|
|
|
static struct class *vc_class;
|
|
|
|
void vcs_make_sysfs(int index)
|
|
{
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL,
|
|
"vcs%u", index + 1);
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 65), NULL,
|
|
"vcsu%u", index + 1);
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL,
|
|
"vcsa%u", index + 1);
|
|
}
|
|
|
|
void vcs_remove_sysfs(int index)
|
|
{
|
|
device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
|
|
device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 65));
|
|
device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
|
|
}
|
|
|
|
int __init vcs_init(void)
|
|
{
|
|
unsigned int i;
|
|
|
|
if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops))
|
|
panic("unable to get major %d for vcs device", VCS_MAJOR);
|
|
vc_class = class_create(THIS_MODULE, "vc");
|
|
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs");
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 64), NULL, "vcsu");
|
|
device_create(vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa");
|
|
for (i = 0; i < MIN_NR_CONSOLES; i++)
|
|
vcs_make_sysfs(i);
|
|
return 0;
|
|
}
|