// 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/console.h>#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 u8 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 u8 *buf, size_t count){	size_t 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; 	tty_port_close(&tpkp->port, tty, filp);} /* * TTY operations write function. */static ssize_t tpk_write(struct tty_struct *tty, const u8 *buf, size_t 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 hangup function. */static void tpk_hangup(struct tty_struct *tty){	struct ttyprintk_port *tpkp = tty->driver_data; 	tty_port_hangup(&tpkp->port);} /* * TTY port operations shutdown function. */static void tpk_port_shutdown(struct tty_port *tport){	struct ttyprintk_port *tpkp =		container_of(tport, struct ttyprintk_port, port);	unsigned long flags; 	spin_lock_irqsave(&tpkp->spinlock, flags);	tpk_flush();	spin_unlock_irqrestore(&tpkp->spinlock, flags);} static const struct tty_operations ttyprintk_ops = {	.open = tpk_open,	.close = tpk_close,	.write = tpk_write,	.write_room = tpk_write_room,	.hangup = tpk_hangup,}; static const struct tty_port_operations tpk_port_ops = {	.shutdown = tpk_port_shutdown,}; static struct tty_driver *ttyprintk_driver; static struct tty_driver *ttyprintk_console_device(struct console *c,						   int *index){	*index = 0;	return ttyprintk_driver;} static struct console ttyprintk_console = {	.name = "ttyprintk",	.device = ttyprintk_console_device,}; 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 = &tpk_port_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;	} 	register_console(&ttyprintk_console); 	return 0; error:	tty_driver_kref_put(ttyprintk_driver);	tty_port_destroy(&tpk_port.port);	return ret;} static void __exit ttyprintk_exit(void){	unregister_console(&ttyprintk_console);	tty_unregister_driver(ttyprintk_driver);	tty_driver_kref_put(ttyprintk_driver);	tty_port_destroy(&tpk_port.port);} device_initcall(ttyprintk_init);module_exit(ttyprintk_exit); MODULE_DESCRIPTION("TTY driver to output user messages via printk");MODULE_LICENSE("GPL");