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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 | // SPDX-License-Identifier: GPL-2.0 /* * KGDB NMI serial console * * Copyright 2010 Google, Inc. * Arve Hjønnevåg <arve@android.com> * Colin Cross <ccross@android.com> * Copyright 2012 Linaro Ltd. * Anton Vorontsov <anton.vorontsov@linaro.org> */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/compiler.h> #include <linux/slab.h> #include <linux/errno.h> #include <linux/atomic.h> #include <linux/console.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/tty_flip.h> #include <linux/serial_core.h> #include <linux/interrupt.h> #include <linux/hrtimer.h> #include <linux/tick.h> #include <linux/kfifo.h> #include <linux/kgdb.h> #include <linux/kdb.h> static int kgdb_nmi_knock = 1; module_param_named(knock, kgdb_nmi_knock, int, 0600); MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \ "must be used to enter the debugger; when set to 0, " \ "hitting return key is enough to enter the debugger; " \ "when set to -1, the debugger is entered immediately " \ "upon NMI"); static char *kgdb_nmi_magic = "$3#33"; module_param_named(magic, kgdb_nmi_magic, charp, 0600); MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)"); static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0); static int kgdb_nmi_console_setup(struct console *co, char *options) { arch_kgdb_ops.enable_nmi(1); /* The NMI console uses the dbg_io_ops to issue console messages. To * avoid duplicate messages during kdb sessions we must inform kdb's * I/O utilities that messages sent to the console will automatically * be displayed on the dbg_io. */ dbg_io_ops->cons = co; return 0; } static void kgdb_nmi_console_write(struct console *co, const char *s, uint c) { int i; for (i = 0; i < c; i++) dbg_io_ops->write_char(s[i]); } static struct tty_driver *kgdb_nmi_tty_driver; static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx) { *idx = co->index; return kgdb_nmi_tty_driver; } static struct console kgdb_nmi_console = { .name = "ttyNMI", .setup = kgdb_nmi_console_setup, .write = kgdb_nmi_console_write, .device = kgdb_nmi_console_device, .flags = CON_PRINTBUFFER | CON_ANYTIME, .index = -1, }; /* * This is usually the maximum rate on debug ports. We make fifo large enough * to make copy-pasting to the terminal usable. */ #define KGDB_NMI_BAUD 115200 #define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ) struct kgdb_nmi_tty_priv { struct tty_port port; struct timer_list timer; STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo; }; static struct tty_port *kgdb_nmi_port; static void kgdb_tty_recv(int ch) { struct kgdb_nmi_tty_priv *priv; char c = ch; if (!kgdb_nmi_port || ch < 0) return; /* * Can't use port->tty->driver_data as tty might be not there. Timer * will check for tty and will get the ref, but here we don't have to * do that, and actually, we can't: we're in NMI context, no locks are * possible. */ priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port); kfifo_in(&priv->fifo, &c, 1); } static int kgdb_nmi_poll_one_knock(void) { static int n; int c; const char *magic = kgdb_nmi_magic; size_t m = strlen(magic); bool printch = false; c = dbg_io_ops->read_char(); if (c == NO_POLL_CHAR) return c; if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) { return 1; } else if (c == magic[n]) { n = (n + 1) % m; if (!n) return 1; printch = true; } else { n = 0; } if (atomic_read(&kgdb_nmi_num_readers)) { kgdb_tty_recv(c); return 0; } if (printch) { kdb_printf("%c", c); return 0; } kdb_printf("\r%s %s to enter the debugger> %*s", kgdb_nmi_knock ? "Type" : "Hit", kgdb_nmi_knock ? magic : "<return>", (int)m, ""); while (m--) kdb_printf("\b"); return 0; } /** * kgdb_nmi_poll_knock - Check if it is time to enter the debugger * * "Serial ports are often noisy, especially when muxed over another port (we * often use serial over the headset connector). Noise on the async command * line just causes characters that are ignored, on a command line that blocked * execution noise would be catastrophic." -- Colin Cross * * So, this function implements KGDB/KDB knocking on the serial line: we won't * enter the debugger until we receive a known magic phrase (which is actually * "$3#33", known as "escape to KDB" command. There is also a relaxed variant * of knocking, i.e. just pressing the return key is enough to enter the * debugger. And if knocking is disabled, the function always returns 1. */ bool kgdb_nmi_poll_knock(void) { if (kgdb_nmi_knock < 0) return true; while (1) { int ret; ret = kgdb_nmi_poll_one_knock(); if (ret == NO_POLL_CHAR) return false; else if (ret == 1) break; } return true; } /* * The tasklet is cheap, it does not cause wakeups when reschedules itself, * instead it waits for the next tick. */ static void kgdb_nmi_tty_receiver(struct timer_list *t) { struct kgdb_nmi_tty_priv *priv = from_timer(priv, t, timer); char ch; priv->timer.expires = jiffies + (HZ/100); add_timer(&priv->timer); if (likely(!atomic_read(&kgdb_nmi_num_readers) || !kfifo_len(&priv->fifo))) return; while (kfifo_out(&priv->fifo, &ch, 1)) tty_insert_flip_char(&priv->port, ch, TTY_NORMAL); tty_flip_buffer_push(&priv->port); } static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) { struct kgdb_nmi_tty_priv *priv = container_of(port, struct kgdb_nmi_tty_priv, port); kgdb_nmi_port = port; priv->timer.expires = jiffies + (HZ/100); add_timer(&priv->timer); return 0; } static void kgdb_nmi_tty_shutdown(struct tty_port *port) { struct kgdb_nmi_tty_priv *priv = container_of(port, struct kgdb_nmi_tty_priv, port); del_timer(&priv->timer); kgdb_nmi_port = NULL; } static const struct tty_port_operations kgdb_nmi_tty_port_ops = { .activate = kgdb_nmi_tty_activate, .shutdown = kgdb_nmi_tty_shutdown, }; static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty) { struct kgdb_nmi_tty_priv *priv; int ret; priv = kzalloc(sizeof(*priv), GFP_KERNEL); if (!priv) return -ENOMEM; INIT_KFIFO(priv->fifo); timer_setup(&priv->timer, kgdb_nmi_tty_receiver, 0); tty_port_init(&priv->port); priv->port.ops = &kgdb_nmi_tty_port_ops; tty->driver_data = priv; ret = tty_port_install(&priv->port, drv, tty); if (ret) { pr_err("%s: can't install tty port: %d\n", __func__, ret); goto err; } return 0; err: tty_port_destroy(&priv->port); kfree(priv); return ret; } static void kgdb_nmi_tty_cleanup(struct tty_struct *tty) { struct kgdb_nmi_tty_priv *priv = tty->driver_data; tty->driver_data = NULL; tty_port_destroy(&priv->port); kfree(priv); } static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file) { struct kgdb_nmi_tty_priv *priv = tty->driver_data; unsigned int mode = file->f_flags & O_ACCMODE; int ret; ret = tty_port_open(&priv->port, tty, file); if (!ret && (mode == O_RDONLY || mode == O_RDWR)) atomic_inc(&kgdb_nmi_num_readers); return ret; } static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file) { struct kgdb_nmi_tty_priv *priv = tty->driver_data; unsigned int mode = file->f_flags & O_ACCMODE; if (mode == O_RDONLY || mode == O_RDWR) atomic_dec(&kgdb_nmi_num_readers); tty_port_close(&priv->port, tty, file); } static void kgdb_nmi_tty_hangup(struct tty_struct *tty) { struct kgdb_nmi_tty_priv *priv = tty->driver_data; tty_port_hangup(&priv->port); } static unsigned int kgdb_nmi_tty_write_room(struct tty_struct *tty) { /* Actually, we can handle any amount as we use polled writes. */ return 2048; } static ssize_t kgdb_nmi_tty_write(struct tty_struct *tty, const u8 *buf, size_t c) { int i; for (i = 0; i < c; i++) dbg_io_ops->write_char(buf[i]); return c; } static const struct tty_operations kgdb_nmi_tty_ops = { .open = kgdb_nmi_tty_open, .close = kgdb_nmi_tty_close, .install = kgdb_nmi_tty_install, .cleanup = kgdb_nmi_tty_cleanup, .hangup = kgdb_nmi_tty_hangup, .write_room = kgdb_nmi_tty_write_room, .write = kgdb_nmi_tty_write, }; int kgdb_register_nmi_console(void) { int ret; if (!arch_kgdb_ops.enable_nmi) return 0; kgdb_nmi_tty_driver = tty_alloc_driver(1, TTY_DRIVER_REAL_RAW); if (IS_ERR(kgdb_nmi_tty_driver)) { pr_err("%s: cannot allocate tty\n", __func__); return PTR_ERR(kgdb_nmi_tty_driver); } kgdb_nmi_tty_driver->driver_name = "ttyNMI"; kgdb_nmi_tty_driver->name = "ttyNMI"; kgdb_nmi_tty_driver->num = 1; kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL; kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL; kgdb_nmi_tty_driver->init_termios = tty_std_termios; tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios, KGDB_NMI_BAUD, KGDB_NMI_BAUD); tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops); ret = tty_register_driver(kgdb_nmi_tty_driver); if (ret) { pr_err("%s: can't register tty driver: %d\n", __func__, ret); goto err_drv_reg; } register_console(&kgdb_nmi_console); return 0; err_drv_reg: tty_driver_kref_put(kgdb_nmi_tty_driver); return ret; } EXPORT_SYMBOL_GPL(kgdb_register_nmi_console); int kgdb_unregister_nmi_console(void) { int ret; if (!arch_kgdb_ops.enable_nmi) return 0; arch_kgdb_ops.enable_nmi(0); ret = unregister_console(&kgdb_nmi_console); if (ret) return ret; tty_unregister_driver(kgdb_nmi_tty_driver); tty_driver_kref_put(kgdb_nmi_tty_driver); return 0; } EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console); |