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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * linux/drivers/char/ttyprintk.c4 *5 * Copyright (C) 2010 Samo Pogacnik6 */7 8/*9 * This pseudo device allows user to make printk messages. It is possible10 * to store "console" messages inline with kernel messages for better analyses11 * of the boot process, for example.12 */13 14#include <linux/console.h>15#include <linux/device.h>16#include <linux/serial.h>17#include <linux/tty.h>18#include <linux/module.h>19#include <linux/spinlock.h>20 21struct ttyprintk_port {22 struct tty_port port;23 spinlock_t spinlock;24};25 26static struct ttyprintk_port tpk_port;27 28/*29 * Our simple preformatting supports transparent output of (time-stamped)30 * printk messages (also suitable for logging service):31 * - any cr is replaced by nl32 * - adds a ttyprintk source tag in front of each line33 * - too long message is fragmented, with '\'nl between fragments34 * - TPK_STR_SIZE isn't really the write_room limiting factor, because35 * it is emptied on the fly during preformatting.36 */37#define TPK_STR_SIZE 508 /* should be bigger then max expected line length */38#define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */39#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)40 41static int tpk_curr;42 43static u8 tpk_buffer[TPK_STR_SIZE + 4];44 45static void tpk_flush(void)46{47 if (tpk_curr > 0) {48 tpk_buffer[tpk_curr] = '\0';49 printk(TPK_PREFIX "[U] %s\n", tpk_buffer);50 tpk_curr = 0;51 }52}53 54static int tpk_printk(const u8 *buf, size_t count)55{56 size_t i;57 58 for (i = 0; i < count; i++) {59 if (tpk_curr >= TPK_STR_SIZE) {60 /* end of tmp buffer reached: cut the message in two */61 tpk_buffer[tpk_curr++] = '\\';62 tpk_flush();63 }64 65 switch (buf[i]) {66 case '\r':67 tpk_flush();68 if ((i + 1) < count && buf[i + 1] == '\n')69 i++;70 break;71 case '\n':72 tpk_flush();73 break;74 default:75 tpk_buffer[tpk_curr++] = buf[i];76 break;77 }78 }79 80 return count;81}82 83/*84 * TTY operations open function.85 */86static int tpk_open(struct tty_struct *tty, struct file *filp)87{88 tty->driver_data = &tpk_port;89 90 return tty_port_open(&tpk_port.port, tty, filp);91}92 93/*94 * TTY operations close function.95 */96static void tpk_close(struct tty_struct *tty, struct file *filp)97{98 struct ttyprintk_port *tpkp = tty->driver_data;99 100 tty_port_close(&tpkp->port, tty, filp);101}102 103/*104 * TTY operations write function.105 */106static ssize_t tpk_write(struct tty_struct *tty, const u8 *buf, size_t count)107{108 struct ttyprintk_port *tpkp = tty->driver_data;109 unsigned long flags;110 int ret;111 112 /* exclusive use of tpk_printk within this tty */113 spin_lock_irqsave(&tpkp->spinlock, flags);114 ret = tpk_printk(buf, count);115 spin_unlock_irqrestore(&tpkp->spinlock, flags);116 117 return ret;118}119 120/*121 * TTY operations write_room function.122 */123static unsigned int tpk_write_room(struct tty_struct *tty)124{125 return TPK_MAX_ROOM;126}127 128/*129 * TTY operations hangup function.130 */131static void tpk_hangup(struct tty_struct *tty)132{133 struct ttyprintk_port *tpkp = tty->driver_data;134 135 tty_port_hangup(&tpkp->port);136}137 138/*139 * TTY port operations shutdown function.140 */141static void tpk_port_shutdown(struct tty_port *tport)142{143 struct ttyprintk_port *tpkp =144 container_of(tport, struct ttyprintk_port, port);145 unsigned long flags;146 147 spin_lock_irqsave(&tpkp->spinlock, flags);148 tpk_flush();149 spin_unlock_irqrestore(&tpkp->spinlock, flags);150}151 152static const struct tty_operations ttyprintk_ops = {153 .open = tpk_open,154 .close = tpk_close,155 .write = tpk_write,156 .write_room = tpk_write_room,157 .hangup = tpk_hangup,158};159 160static const struct tty_port_operations tpk_port_ops = {161 .shutdown = tpk_port_shutdown,162};163 164static struct tty_driver *ttyprintk_driver;165 166static struct tty_driver *ttyprintk_console_device(struct console *c,167 int *index)168{169 *index = 0;170 return ttyprintk_driver;171}172 173static struct console ttyprintk_console = {174 .name = "ttyprintk",175 .device = ttyprintk_console_device,176};177 178static int __init ttyprintk_init(void)179{180 int ret;181 182 spin_lock_init(&tpk_port.spinlock);183 184 ttyprintk_driver = tty_alloc_driver(1,185 TTY_DRIVER_RESET_TERMIOS |186 TTY_DRIVER_REAL_RAW |187 TTY_DRIVER_UNNUMBERED_NODE);188 if (IS_ERR(ttyprintk_driver))189 return PTR_ERR(ttyprintk_driver);190 191 tty_port_init(&tpk_port.port);192 tpk_port.port.ops = &tpk_port_ops;193 194 ttyprintk_driver->driver_name = "ttyprintk";195 ttyprintk_driver->name = "ttyprintk";196 ttyprintk_driver->major = TTYAUX_MAJOR;197 ttyprintk_driver->minor_start = 3;198 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;199 ttyprintk_driver->init_termios = tty_std_termios;200 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;201 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);202 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);203 204 ret = tty_register_driver(ttyprintk_driver);205 if (ret < 0) {206 printk(KERN_ERR "Couldn't register ttyprintk driver\n");207 goto error;208 }209 210 register_console(&ttyprintk_console);211 212 return 0;213 214error:215 tty_driver_kref_put(ttyprintk_driver);216 tty_port_destroy(&tpk_port.port);217 return ret;218}219 220static void __exit ttyprintk_exit(void)221{222 unregister_console(&ttyprintk_console);223 tty_unregister_driver(ttyprintk_driver);224 tty_driver_kref_put(ttyprintk_driver);225 tty_port_destroy(&tpk_port.port);226}227 228device_initcall(ttyprintk_init);229module_exit(ttyprintk_exit);230 231MODULE_DESCRIPTION("TTY driver to output user messages via printk");232MODULE_LICENSE("GPL");233