cregit-Linux how code gets into the kernel

Release 4.11 drivers/tty/vt/vc_screen.c

Directory: drivers/tty/vt
/*
 * Provide access to virtual console memory.
 * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
 * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
 *            [minor: N]
 *
 * /dev/vcsaN: idem, but including attributes, and prefixed with
 *      the 4 bytes lines,columns,x,y (as screendump used to give).
 *      Attribute/character pair is in native endianity.
 *            [minor: N+128]
 *
 * This replaces screendump and part of selection, so that the system
 * administrator can control access using file system permissions.
 *
 * aeb@cwi.nl - efter Friedas begravelse - 950211
 *
 * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
 *       - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
 *       - making it shorter - scr_readw are macros which expand in PRETTY long code
 */

#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/tty.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>
#include <linux/kbd_kern.h>
#include <linux/console.h>
#include <linux/device.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/notifier.h>

#include <linux/uaccess.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>


#undef attr

#undef org

#undef addr

#define HEADER_SIZE	4


#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)


struct vcs_poll_data {
	
struct notifier_block notifier;
	
unsigned int cons_num;
	
bool seen_last_update;
	
wait_queue_head_t waitq;
	
struct fasync_struct *fasync;
};



static int

vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param)
{
	struct vt_notifier_param *param = _param;
	struct vc_data *vc = param->vc;
	struct vcs_poll_data *poll =
		container_of(nb, struct vcs_poll_data, notifier);
	int currcons = poll->cons_num;

	if (code != VT_UPDATE)
		return NOTIFY_DONE;

	if (currcons == 0)
		currcons = fg_console;
	else
		currcons--;
	if (currcons != vc->vc_num)
		return NOTIFY_DONE;

	poll->seen_last_update = false;
	wake_up_interruptible(&poll->waitq);
	kill_fasync(&poll->fasync, SIGIO, POLL_IN);
	return NOTIFY_OK;
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre120100.00%1100.00%


Total120100.00%1100.00%





static void

vcs_poll_data_free(struct vcs_poll_data *poll)
{
	unregister_vt_notifier(&poll->notifier);
	kfree(poll);
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre24100.00%1100.00%


Total24100.00%1100.00%





static struct vcs_poll_data *

vcs_poll_data_get(struct file *file)
{
	struct vcs_poll_data *poll = file->private_data, *kill = NULL;

	if (poll)
		return poll;

	poll = kzalloc(sizeof(*poll), GFP_KERNEL);
	if (!poll)
		return NULL;
	poll->cons_num = iminor(file_inode(file)) & 127;
	init_waitqueue_head(&poll->waitq);
	poll->notifier.notifier_call = vcs_notifier;
	if (register_vt_notifier(&poll->notifier) != 0) {
		kfree(poll);
		return NULL;
	}

	/*
         * This code may be called either through ->poll() or ->fasync().
         * If we have two threads using the same file descriptor, they could
         * both enter this function, both notice that the structure hasn't
         * been allocated yet and go ahead allocating it in parallel, but
         * only one of them must survive and be shared otherwise we'd leak
         * memory with a dangling notifier callback.
         */
	spin_lock(&file->f_lock);
	if (!file->private_data) {
		file->private_data = poll;
	} else {
		/* someone else raced ahead of us */
		kill = poll;
		poll = file->private_data;
	}
	spin_unlock(&file->f_lock);
	if (kill)
		vcs_poll_data_free(kill);

	return poll;
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre14688.48%133.33%


Al Viro1911.52%266.67%


Total165100.00%3100.00%



/*
 * Returns VC for inode.
 * Must be called with console_lock.
 */


static struct vc_data*

vcs_vc(struct inode *inode, int *viewed)
{
	unsigned int currcons = iminor(inode) & 127;

	WARN_CONSOLE_UNLOCKED();

	if (currcons == 0) {
		currcons = fg_console;
		if (viewed)
			*viewed = 1;
	} else {
		currcons--;
		if (viewed)
			*viewed = 0;
	}
	return vc_cons[currcons].d;
}


Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)3445.33%457.14%


Jiri Olsa3445.33%114.29%


Christoph Hellwig68.00%114.29%


Al Viro11.33%114.29%


Total75100.00%7100.00%



/*
 * Returns size for VC carried by inode.
 * Must be called with console_lock.
 */


static int

vcs_size(struct inode *inode)
{
	int size;
	int minor = iminor(inode);
	struct vc_data *vc;

	WARN_CONSOLE_UNLOCKED();

	vc = vcs_vc(inode, NULL);
	if (!vc)
		return -ENXIO;

	size = vc->vc_rows * vc->vc_cols;

	if (minor & 128)
		size = 2*size + HEADER_SIZE;
	return size;
}


Contributors
PersonTokensPropCommitsCommitProp
Jiri Olsa4661.33%116.67%


Linus Torvalds (pre-git)1925.33%233.33%


Roman Zippel56.67%116.67%


Christoph Hellwig45.33%116.67%


Linus Torvalds11.33%116.67%


Total75100.00%6100.00%






static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
{
	int size;

	console_lock();
	size = vcs_size(file_inode(file));
	console_unlock();
	if (size < 0)
		return size;
	return fixed_size_llseek(file, offset, orig, size);
}



Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)2849.12%450.00%


Jiri Olsa1526.32%112.50%


Al Viro1017.54%225.00%


Robert Love47.02%112.50%


Total57100.00%8100.00%





static ssize_t

vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct inode *inode = file_inode(file);
	unsigned int currcons = iminor(inode);
	struct vc_data *vc;
	struct vcs_poll_data *poll;
	long pos;
	long attr, read;
	int col, maxcol, viewed;
	unsigned short *org = NULL;
	ssize_t ret;
	char *con_buf;

	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 = (currcons & 128);
	ret = -ENXIO;
	vc = vcs_vc(inode, &viewed);
	if (!vc)
		goto unlock_out;

	ret = -EINVAL;
	if (pos < 0)
		goto unlock_out;
	poll = file->private_data;
	if (count && poll)
		poll->seen_last_update = true;
	read = 0;
	ret = 0;
	while (count) {
		char *con_buf0, *con_buf_start;
		long this_round, size;
		ssize_t orig_count;
		long p = pos;

		/* Check whether we are above size each round,
                 * as copy_to_user at the end of this loop
                 * could sleep.
                 */
		size = vcs_size(inode);
		if (size < 0) {
			if (read)
				break;
			ret = size;
			goto unlock_out;
		}
		if (pos >= size)
			break;
		if (count > size - pos)
			count = size - pos;

		this_round = count;
		if (this_round > CON_BUF_SIZE)
			this_round = CON_BUF_SIZE;

		/* Perform the whole read into the local con_buf.
                 * Then we can drop the console spinlock and safely
                 * attempt to move it to userspace.
                 */

		con_buf_start = con_buf0 = con_buf;
		orig_count = this_round;
		maxcol = vc->vc_cols;
		if (!attr) {
			org = screen_pos(vc, p, viewed);
			col = p % maxcol;
			p += maxcol - col;
			while (this_round-- > 0) {
				*con_buf0++ = (vcs_scr_readw(vc, org++) & 0xff);
				if (++col == maxcol) {
					org = screen_pos(vc, p, viewed);
					col = 0;
					p += maxcol;
				}
			}
		} else {
			if (p < HEADER_SIZE) {
				size_t tmp_count;

				con_buf0[0] = (char)vc->vc_rows;
				con_buf0[1] = (char)vc->vc_cols;
				getconsxy(vc, con_buf0 + 2);

				con_buf_start += p;
				this_round += p;
				if (this_round > CON_BUF_SIZE) {
					this_round = CON_BUF_SIZE;
					orig_count = this_round - p;
				}

				tmp_count = HEADER_SIZE;
				if (tmp_count > this_round)
					tmp_count = this_round;

				/* Advance state pointers and move on. */
				this_round -= tmp_count;
				p = HEADER_SIZE;
				con_buf0 = con_buf + HEADER_SIZE;
				/* If this_round >= 0, then p is even... */
			} else if (p & 1) {
				/* Skip first byte for output if start address is odd
                                 * Update region sizes up/down depending on free
                                 * space in buffer.
                                 */
				con_buf_start++;
				if (this_round < CON_BUF_SIZE)
					this_round++;
				else
					orig_count--;
			}
			if (this_round > 0) {
				unsigned short *tmp_buf = (unsigned short *)con_buf0;

				p -= HEADER_SIZE;
				p /= 2;
				col = p % maxcol;

				org = screen_pos(vc, p, viewed);
				p += maxcol - col;

				/* Buffer has even length, so we can always copy
                                 * character + attribute. We do not copy last byte
                                 * to userspace if this_round is odd.
                                 */
				this_round = (this_round + 1) >> 1;

				while (this_round) {
					*tmp_buf++ = vcs_scr_readw(vc, org++);
					this_round --;
					if (++col == maxcol) {
						org = screen_pos(vc, p, viewed);
						col = 0;
						p += maxcol;
					}
				}
			}
		}

		/* Finally, release the console semaphore while we push
                 * all the data to userspace from our temporary buffer.
                 *
                 * AKPM: Even though it's a semaphore, we should drop it because
                 * the pagefault handling code may want to call printk().
                 */

		console_unlock();
		ret = copy_to_user(buf, con_buf_start, orig_count);
		console_lock();

		if (ret) {
			read += (orig_count - ret);
			ret = -EFAULT;
			break;
		}
		buf += orig_count;
		pos += orig_count;
		read += orig_count;
		count -= orig_count;
	}
	*ppos += read;
	if (read)
		ret = read;
unlock_out:
	console_unlock();
	free_page((unsigned long) con_buf);
	return ret;
}


Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)57182.28%1050.00%


Jiri Olsa608.65%210.00%


Nico Pitre233.31%15.00%


Christoph Hellwig213.03%15.00%


Alan Cox50.72%15.00%


Al Viro50.72%315.00%


Linus Torvalds50.72%15.00%


Torben Hohn40.58%15.00%


Total694100.00%20100.00%





static ssize_t

vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	struct inode *inode = file_inode(file);
	unsigned int currcons = iminor(inode);
	struct vc_data *vc;
	long pos;
	long attr, size, written;
	char *con_buf0;
	int col, maxcol, viewed;
	u16 *org0 = NULL, *org = NULL;
	size_t ret;
	char *con_buf;

	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 = (currcons & 128);
	ret = -ENXIO;
	vc = vcs_vc(inode, &viewed);
	if (!vc)
		goto unlock_out;

	size = vcs_size(inode);
	ret = -EINVAL;
	if (pos < 0 || pos > size)
		goto unlock_out;
	if (count > size - pos)
		count = size - pos;
	written = 0;
	while (count) {
		long this_round = count;
		size_t orig_count;
		long p;

		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(inode);
		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.
                 */

		con_buf0 = con_buf;
		orig_count = this_round;
		maxcol = vc->vc_cols;
		p = pos;
		if (!attr) {
			org0 = org = screen_pos(vc, p, viewed);
			col = p % maxcol;
			p += maxcol - col;

			while (this_round > 0) {
				unsigned char c = *con_buf0++;

				this_round--;
				vcs_scr_writew(vc,
					       (vcs_scr_readw(vc, org) & 0xff00) | c, org);
				org++;
				if (++col == maxcol) {
					org = screen_pos(vc, p, viewed);
					col = 0;
					p += maxcol;
				}
			}
		} else {
			if (p < HEADER_SIZE) {
				char header[HEADER_SIZE];

				getconsxy(vc, header + 2);
				while (p < HEADER_SIZE && this_round > 0) {
					this_round--;
					header[p++] = *con_buf0++;
				}
				if (!viewed)
					putconsxy(vc, header + 2);
			}
			p -= HEADER_SIZE;
			col = (p/2) % maxcol;
			if (this_round > 0) {
				org0 = org = screen_pos(vc, p/2, viewed);
				if ((p & 1) && this_round > 0) {
					char c;

					this_round--;
					c = *con_buf0++;
#ifdef __BIG_ENDIAN
					vcs_scr_writew(vc, c |
					     (vcs_scr_readw(vc, org) & 0xff00), org);
#else
					vcs_scr_writew(vc, (c << 8) |
					     (vcs_scr_readw(vc, org) & 0xff), org);
#endif
					org++;
					p++;
					if (++col == maxcol) {
						org = screen_pos(vc, p/2, viewed);
						col = 0;
					}
				}
				p /= 2;
				p += maxcol - col;
			}
			while (this_round > 1) {
				unsigned short w;

				w = get_unaligned(((unsigned short *)con_buf0));
				vcs_scr_writew(vc, w, org++);
				con_buf0 += 2;
				this_round -= 2;
				if (++col == maxcol) {
					org = screen_pos(vc, p, viewed);
					col = 0;
					p += maxcol;
				}
			}
			if (this_round > 0) {
				unsigned char c;

				c = *con_buf0++;
#ifdef __BIG_ENDIAN
				vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff) | (c << 8), org);
#else
				vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org);
#endif
			}
		}
		count -= orig_count;
		written += orig_count;
		buf += orig_count;
		pos += orig_count;
		if (org0)
			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;
}


Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)75686.90%1659.26%


Jiri Olsa606.90%27.41%


Christoph Hellwig262.99%13.70%


Nico Pitre91.03%13.70%


Alan Cox50.57%13.70%


Al Viro50.57%311.11%


Torben Hohn40.46%13.70%


Linus Torvalds40.46%13.70%


Roman Zippel10.11%13.70%


Total870100.00%27100.00%





static unsigned int

vcs_poll(struct file *file, poll_table *wait)
{
	struct vcs_poll_data *poll = vcs_poll_data_get(file);
	int ret = DEFAULT_POLLMASK|POLLERR|POLLPRI;

	if (poll) {
		poll_wait(file, &poll->waitq, wait);
		if (poll->seen_last_update)
			ret = DEFAULT_POLLMASK;
	}
	return ret;
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre6598.48%266.67%


Linus Torvalds (pre-git)11.52%133.33%


Total66100.00%3100.00%





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);
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre73100.00%1100.00%


Total73100.00%1100.00%





static int

vcs_open(struct inode *inode, struct file *filp)
{
	unsigned int currcons = iminor(inode) & 127;
	int ret = 0;
	
	console_lock();
	if(currcons && !vc_cons_allocated(currcons-1))
		ret = -ENXIO;
	console_unlock();
	return ret;
}


Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)4170.69%233.33%


Jonathan Corbet1322.41%116.67%


Alan Cox23.45%116.67%


Al Viro11.72%116.67%


Nico Pitre11.72%116.67%


Total58100.00%6100.00%






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;
}


Contributors
PersonTokensPropCommitsCommitProp
Nico Pitre37100.00%1100.00%


Total37100.00%1100.00%




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 + 129), NULL,
		      "vcsa%u", index + 1);
}


Contributors
PersonTokensPropCommitsCommitProp
Greg Kroah-Hartman4885.71%450.00%


Linus Torvalds (pre-git)47.14%112.50%


Kay Sievers23.57%112.50%


Andrew Morton11.79%112.50%


Alan Cox11.79%112.50%


Total56100.00%8100.00%






void vcs_remove_sysfs(int index)
{
	device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 1));
	device_destroy(vc_class, MKDEV(VCS_MAJOR, index + 129));
}


Contributors
PersonTokensPropCommitsCommitProp
Greg Kroah-Hartman2877.78%342.86%


Andrew Morton411.11%114.29%


Kay Sievers25.56%114.29%


Alan Cox12.78%114.29%


Linus Torvalds (pre-git)12.78%114.29%


Total36100.00%7100.00%






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, 128), NULL, "vcsa");
	for (i = 0; i < MIN_NR_CONSOLES; i++)
		vcs_make_sysfs(i);
	return 0;
}

Contributors
PersonTokensPropCommitsCommitProp
Greg Kroah-Hartman4647.42%660.00%


Linus Torvalds (pre-git)2525.77%220.00%


Kay Sievers2222.68%110.00%


Andrew Morton44.12%110.00%


Total97100.00%10100.00%




Overall Contributors
PersonTokensPropCommitsCommitProp
Linus Torvalds (pre-git)155358.34%2541.67%


Nico Pitre55520.85%35.00%


Jiri Olsa2218.30%23.33%


Greg Kroah-Hartman1314.92%711.67%


Christoph Hellwig572.14%11.67%


Al Viro411.54%58.33%


Kay Sievers260.98%23.33%


Alan Cox140.53%35.00%


Jonathan Corbet130.49%11.67%


Linus Torvalds110.41%35.00%


Andrew Morton90.34%11.67%


Torben Hohn80.30%11.67%


Art Haas80.30%11.67%


Roman Zippel60.23%11.67%


Robert Love40.15%11.67%


Paul Gortmaker30.11%11.67%


Arjan van de Ven10.04%11.67%


Jovi Zhang10.04%11.67%


Total2662100.00%60100.00%


Directory: drivers/tty/vt



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