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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/drivers/char/ttyprintk.c
*
* Copyright (C) 2010 Samo Pogacnik
*/
/*
* This pseudo device allows user to make printk messages. It is possible
* to store "console" messages inline with kernel messages for better analyses
* of the boot process, for example.
*/
#include <linux/device.h>
#include <linux/serial.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/spinlock.h>
struct ttyprintk_port {
struct tty_port port;
spinlock_t spinlock;
};
static struct ttyprintk_port tpk_port;
/*
* Our simple preformatting supports transparent output of (time-stamped)
* printk messages (also suitable for logging service):
* - any cr is replaced by nl
* - adds a ttyprintk source tag in front of each line
* - too long message is fragmented, with '\'nl between fragments
* - TPK_STR_SIZE isn't really the write_room limiting factor, because
* it is emptied on the fly during preformatting.
*/
#define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
#define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
static int tpk_curr;
static char tpk_buffer[TPK_STR_SIZE + 4];
static void tpk_flush(void)
{
if (tpk_curr > 0) {
tpk_buffer[tpk_curr] = '\0';
printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
tpk_curr = 0;
}
}
static int tpk_printk(const unsigned char *buf, int count)
{
int i = tpk_curr;
if (buf == NULL) {
tpk_flush();
return i;
}
for (i = 0; i < count; i++) {
if (tpk_curr >= TPK_STR_SIZE) {
/* end of tmp buffer reached: cut the message in two */
tpk_buffer[tpk_curr++] = '\\';
tpk_flush();
}
switch (buf[i]) {
case '\r':
tpk_flush();
if ((i + 1) < count && buf[i + 1] == '\n')
i++;
break;
case '\n':
tpk_flush();
break;
default:
tpk_buffer[tpk_curr++] = buf[i];
break;
}
}
return count;
}
/*
* TTY operations open function.
*/
static int tpk_open(struct tty_struct *tty, struct file *filp)
{
tty->driver_data = &tpk_port;
return tty_port_open(&tpk_port.port, tty, filp);
}
/*
* TTY operations close function.
*/
static void tpk_close(struct tty_struct *tty, struct file *filp)
{
struct ttyprintk_port *tpkp = tty->driver_data;
unsigned long flags;
spin_lock_irqsave(&tpkp->spinlock, flags);
/* flush tpk_printk buffer */
tpk_printk(NULL, 0);
spin_unlock_irqrestore(&tpkp->spinlock, flags);
tty_port_close(&tpkp->port, tty, filp);
}
/*
* TTY operations write function.
*/
static int tpk_write(struct tty_struct *tty,
const unsigned char *buf, int count)
{
struct ttyprintk_port *tpkp = tty->driver_data;
unsigned long flags;
int ret;
/* exclusive use of tpk_printk within this tty */
spin_lock_irqsave(&tpkp->spinlock, flags);
ret = tpk_printk(buf, count);
spin_unlock_irqrestore(&tpkp->spinlock, flags);
return ret;
}
/*
* TTY operations write_room function.
*/
static unsigned int tpk_write_room(struct tty_struct *tty)
{
return TPK_MAX_ROOM;
}
/*
* TTY operations ioctl function.
*/
static int tpk_ioctl(struct tty_struct *tty,
unsigned int cmd, unsigned long arg)
{
struct ttyprintk_port *tpkp = tty->driver_data;
if (!tpkp)
return -EINVAL;
switch (cmd) {
/* Stop TIOCCONS */
case TIOCCONS:
return -EOPNOTSUPP;
default:
return -ENOIOCTLCMD;
}
return 0;
}
/*
* TTY operations hangup function.
*/
static void tpk_hangup(struct tty_struct *tty)
{
struct ttyprintk_port *tpkp = tty->driver_data;
tty_port_hangup(&tpkp->port);
}
static const struct tty_operations ttyprintk_ops = {
.open = tpk_open,
.close = tpk_close,
.write = tpk_write,
.write_room = tpk_write_room,
.ioctl = tpk_ioctl,
.hangup = tpk_hangup,
};
static const struct tty_port_operations null_ops = { };
static struct tty_driver *ttyprintk_driver;
static int __init ttyprintk_init(void)
{
int ret;
spin_lock_init(&tpk_port.spinlock);
ttyprintk_driver = tty_alloc_driver(1,
TTY_DRIVER_RESET_TERMIOS |
TTY_DRIVER_REAL_RAW |
TTY_DRIVER_UNNUMBERED_NODE);
if (IS_ERR(ttyprintk_driver))
return PTR_ERR(ttyprintk_driver);
tty_port_init(&tpk_port.port);
tpk_port.port.ops = &null_ops;
ttyprintk_driver->driver_name = "ttyprintk";
ttyprintk_driver->name = "ttyprintk";
ttyprintk_driver->major = TTYAUX_MAJOR;
ttyprintk_driver->minor_start = 3;
ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
ttyprintk_driver->init_termios = tty_std_termios;
ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
ret = tty_register_driver(ttyprintk_driver);
if (ret < 0) {
printk(KERN_ERR "Couldn't register ttyprintk driver\n");
goto error;
}
return 0;
error:
put_tty_driver(ttyprintk_driver);
tty_port_destroy(&tpk_port.port);
return ret;
}
static void __exit ttyprintk_exit(void)
{
tty_unregister_driver(ttyprintk_driver);
put_tty_driver(ttyprintk_driver);
tty_port_destroy(&tpk_port.port);
}
device_initcall(ttyprintk_init);
module_exit(ttyprintk_exit);
MODULE_LICENSE("GPL");
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