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|
/*
* linux/drivers/char/vc_screen.c
*
* 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/tty.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/mutex.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/smp_lock.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 <asm/uaccess.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>
#undef attr
#undef org
#undef addr
#define HEADER_SIZE 4
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;
}
static void
vcs_poll_data_free(struct vcs_poll_data *poll)
{
unregister_vt_notifier(&poll->notifier);
kfree(poll);
}
static struct vcs_poll_data *
vcs_poll_data_get(struct file *file)
{
struct vcs_poll_data *poll = file->private_data;
if (poll)
return poll;
poll = kzalloc(sizeof(*poll), GFP_KERNEL);
if (!poll)
return NULL;
poll->cons_num = iminor(file->f_path.dentry->d_inode) & 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 */
vcs_poll_data_free(poll);
poll = file->private_data;
}
spin_unlock(&file->f_lock);
return poll;
}
static int
vcs_size(struct inode *inode)
{
int size;
int minor = iminor(inode);
int currcons = minor & 127;
struct vc_data *vc;
if (currcons == 0)
currcons = fg_console;
else
currcons--;
if (!vc_cons_allocated(currcons))
return -ENXIO;
vc = vc_cons[currcons].d;
size = vc->vc_rows * vc->vc_cols;
if (minor & 128)
size = 2*size + HEADER_SIZE;
return size;
}
static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
{
int size;
mutex_lock(&con_buf_mtx);
size = vcs_size(file->f_path.dentry->d_inode);
switch (orig) {
default:
mutex_unlock(&con_buf_mtx);
return -EINVAL;
case 2:
offset += size;
break;
case 1:
offset += file->f_pos;
case 0:
break;
}
if (offset < 0 || offset > size) {
mutex_unlock(&con_buf_mtx);
return -EINVAL;
}
file->f_pos = offset;
mutex_unlock(&con_buf_mtx);
return file->f_pos;
}
static ssize_t
vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct inode *inode = file->f_path.dentry->d_inode;
unsigned int currcons = iminor(inode);
struct vc_data *vc;
struct vcs_poll_data *poll;
long pos;
long viewed, attr, read;
int col, maxcol;
unsigned short *org = NULL;
ssize_t ret;
mutex_lock(&con_buf_mtx);
pos = *ppos;
/* Select the proper current console and verify
* sanity of the situation under the console lock.
*/
acquire_console_sem();
attr = (currcons & 128);
currcons = (currcons & 127);
if (currcons == 0) {
currcons = fg_console;
viewed = 1;
} else {
currcons--;
viewed = 0;
}
ret = -ENXIO;
if (!vc_cons_allocated(currcons))
goto unlock_out;
vc = vc_cons[currcons].d;
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 (pos >= size)
break;
if (count > size
|