// 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 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; 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 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 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_LICENSE("GPL");