alistair23-linux/drivers/tty/vt/vc_screen.c
Nicolas Pitre 47c344d0bd vcs: make proper usage of the poll flags
Kay Sievers pointed out that usage of POLLIN is well defined by POSIX,
and the current usage here doesn't follow that definition.  So let's
duplicate the same semantics as implemented by sysfs_poll() instead.

Signed-off-by: Nicolas Pitre <nicolas.pitre@canonical.com>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-11-11 10:51:35 -08:00

645 lines
14 KiB
C

/*
* 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 - 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().
*/
release_console_sem();
ret = copy_to_user(buf, con_buf_start, orig_count);
acquire_console_sem();
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:
release_console_sem();
mutex_unlock(&con_buf_mtx);
return ret;
}
static ssize_t
vcs_write(struct file *file, const 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;
long pos;
long viewed, attr, size, written;
char *con_buf0;
int col, maxcol;
u16 *org0 = NULL, *org = NULL;
size_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;
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.
*/
release_console_sem();
ret = copy_from_user(con_buf, buf, this_round);
acquire_console_sem();
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 (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:
release_console_sem();
mutex_unlock(&con_buf_mtx);
return ret;
}
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;
}
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 = iminor(inode) & 127;
int ret = 0;
tty_lock();
if(currcons && !vc_cons_allocated(currcons-1))
ret = -ENXIO;
tty_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 + 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 + 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, 128), NULL, "vcsa");
for (i = 0; i < MIN_NR_CONSOLES; i++)
vcs_make_sysfs(i);
return 0;
}