diff options
Diffstat (limited to 'drivers/char/ttyprintk.c')
| -rw-r--r-- | drivers/char/ttyprintk.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c new file mode 100644 index 000000000..ed45d0490 --- /dev/null +++ b/drivers/char/ttyprintk.c @@ -0,0 +1,232 @@ +// 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"); |