1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/drivers/char/ttyprintk.c 4 * 5 * Copyright (C) 2010 Samo Pogacnik 6 */ 7 8 /* 9 * This pseudo device allows user to make printk messages. It is possible 10 * to store "console" messages inline with kernel messages for better analyses 11 * of the boot process, for example. 12 */ 13 14 #include <linux/device.h> 15 #include <linux/serial.h> 16 #include <linux/tty.h> 17 #include <linux/module.h> 18 #include <linux/spinlock.h> 19 20 struct ttyprintk_port { 21 struct tty_port port; 22 spinlock_t spinlock; 23 }; 24 25 static struct ttyprintk_port tpk_port; 26 27 /* 28 * Our simple preformatting supports transparent output of (time-stamped) 29 * printk messages (also suitable for logging service): 30 * - any cr is replaced by nl 31 * - adds a ttyprintk source tag in front of each line 32 * - too long message is fragmented, with '\'nl between fragments 33 * - TPK_STR_SIZE isn't really the write_room limiting factor, because 34 * it is emptied on the fly during preformatting. 35 */ 36 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */ 37 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */ 38 #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL) 39 40 static int tpk_curr; 41 42 static char tpk_buffer[TPK_STR_SIZE + 4]; 43 44 static void tpk_flush(void) 45 { 46 if (tpk_curr > 0) { 47 tpk_buffer[tpk_curr] = '\0'; 48 printk(TPK_PREFIX "[U] %s\n", tpk_buffer); 49 tpk_curr = 0; 50 } 51 } 52 53 static int tpk_printk(const unsigned char *buf, int count) 54 { 55 int i = tpk_curr; 56 57 if (buf == NULL) { 58 tpk_flush(); 59 return i; 60 } 61 62 for (i = 0; i < count; i++) { 63 if (tpk_curr >= TPK_STR_SIZE) { 64 /* end of tmp buffer reached: cut the message in two */ 65 tpk_buffer[tpk_curr++] = '\\'; 66 tpk_flush(); 67 } 68 69 switch (buf[i]) { 70 case '\r': 71 tpk_flush(); 72 if ((i + 1) < count && buf[i + 1] == '\n') 73 i++; 74 break; 75 case '\n': 76 tpk_flush(); 77 break; 78 default: 79 tpk_buffer[tpk_curr++] = buf[i]; 80 break; 81 } 82 } 83 84 return count; 85 } 86 87 /* 88 * TTY operations open function. 89 */ 90 static int tpk_open(struct tty_struct *tty, struct file *filp) 91 { 92 tty->driver_data = &tpk_port; 93 94 return tty_port_open(&tpk_port.port, tty, filp); 95 } 96 97 /* 98 * TTY operations close function. 99 */ 100 static void tpk_close(struct tty_struct *tty, struct file *filp) 101 { 102 struct ttyprintk_port *tpkp = tty->driver_data; 103 unsigned long flags; 104 105 spin_lock_irqsave(&tpkp->spinlock, flags); 106 /* flush tpk_printk buffer */ 107 tpk_printk(NULL, 0); 108 spin_unlock_irqrestore(&tpkp->spinlock, flags); 109 110 tty_port_close(&tpkp->port, tty, filp); 111 } 112 113 /* 114 * TTY operations write function. 115 */ 116 static int tpk_write(struct tty_struct *tty, 117 const unsigned char *buf, int count) 118 { 119 struct ttyprintk_port *tpkp = tty->driver_data; 120 unsigned long flags; 121 int ret; 122 123 124 /* exclusive use of tpk_printk within this tty */ 125 spin_lock_irqsave(&tpkp->spinlock, flags); 126 ret = tpk_printk(buf, count); 127 spin_unlock_irqrestore(&tpkp->spinlock, flags); 128 129 return ret; 130 } 131 132 /* 133 * TTY operations write_room function. 134 */ 135 static int tpk_write_room(struct tty_struct *tty) 136 { 137 return TPK_MAX_ROOM; 138 } 139 140 /* 141 * TTY operations ioctl function. 142 */ 143 static int tpk_ioctl(struct tty_struct *tty, 144 unsigned int cmd, unsigned long arg) 145 { 146 struct ttyprintk_port *tpkp = tty->driver_data; 147 148 if (!tpkp) 149 return -EINVAL; 150 151 switch (cmd) { 152 /* Stop TIOCCONS */ 153 case TIOCCONS: 154 return -EOPNOTSUPP; 155 default: 156 return -ENOIOCTLCMD; 157 } 158 return 0; 159 } 160 161 static const struct tty_operations ttyprintk_ops = { 162 .open = tpk_open, 163 .close = tpk_close, 164 .write = tpk_write, 165 .write_room = tpk_write_room, 166 .ioctl = tpk_ioctl, 167 }; 168 169 static const struct tty_port_operations null_ops = { }; 170 171 static struct tty_driver *ttyprintk_driver; 172 173 static int __init ttyprintk_init(void) 174 { 175 int ret; 176 177 spin_lock_init(&tpk_port.spinlock); 178 179 ttyprintk_driver = tty_alloc_driver(1, 180 TTY_DRIVER_RESET_TERMIOS | 181 TTY_DRIVER_REAL_RAW | 182 TTY_DRIVER_UNNUMBERED_NODE); 183 if (IS_ERR(ttyprintk_driver)) 184 return PTR_ERR(ttyprintk_driver); 185 186 tty_port_init(&tpk_port.port); 187 tpk_port.port.ops = &null_ops; 188 189 ttyprintk_driver->driver_name = "ttyprintk"; 190 ttyprintk_driver->name = "ttyprintk"; 191 ttyprintk_driver->major = TTYAUX_MAJOR; 192 ttyprintk_driver->minor_start = 3; 193 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE; 194 ttyprintk_driver->init_termios = tty_std_termios; 195 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET; 196 tty_set_operations(ttyprintk_driver, &ttyprintk_ops); 197 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0); 198 199 ret = tty_register_driver(ttyprintk_driver); 200 if (ret < 0) { 201 printk(KERN_ERR "Couldn't register ttyprintk driver\n"); 202 goto error; 203 } 204 205 return 0; 206 207 error: 208 put_tty_driver(ttyprintk_driver); 209 tty_port_destroy(&tpk_port.port); 210 return ret; 211 } 212 213 static void __exit ttyprintk_exit(void) 214 { 215 tty_unregister_driver(ttyprintk_driver); 216 put_tty_driver(ttyprintk_driver); 217 tty_port_destroy(&tpk_port.port); 218 } 219 220 device_initcall(ttyprintk_init); 221 module_exit(ttyprintk_exit); 222 223 MODULE_LICENSE("GPL"); 224