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1// SPDX-License-Identifier: GPL-2.02/*3 * Based on the same principle as kgdboe using the NETPOLL api, this4 * driver uses a console polling api to implement a gdb serial inteface5 * which is multiplexed on a console port.6 *7 * Maintainer: Jason Wessel <jason.wessel@windriver.com>8 *9 * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.10 */11 12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt13 14#include <linux/kernel.h>15#include <linux/ctype.h>16#include <linux/kgdb.h>17#include <linux/kdb.h>18#include <linux/tty.h>19#include <linux/console.h>20#include <linux/vt_kern.h>21#include <linux/input.h>22#include <linux/irq_work.h>23#include <linux/module.h>24#include <linux/platform_device.h>25#include <linux/serial_core.h>26 27#define MAX_CONFIG_LEN 4028 29static struct kgdb_io kgdboc_io_ops;30 31/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */32static int configured = -1;33static DEFINE_MUTEX(config_mutex);34 35static char config[MAX_CONFIG_LEN];36static struct kparam_string kps = {37 .string = config,38 .maxlen = MAX_CONFIG_LEN,39};40 41static int kgdboc_use_kms; /* 1 if we use kernel mode switching */42static struct tty_driver *kgdb_tty_driver;43static int kgdb_tty_line;44 45static struct platform_device *kgdboc_pdev;46 47#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)48static struct kgdb_io kgdboc_earlycon_io_ops;49static int (*earlycon_orig_exit)(struct console *con);50#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */51 52/*53 * When we leave the debug trap handler we need to reset the keyboard status54 * (since the original keyboard state gets partially clobbered by kdb use of55 * the keyboard).56 *57 * The path to deliver the reset is somewhat circuitous.58 *59 * To deliver the reset we register an input handler, reset the keyboard and60 * then deregister the input handler. However, to get this done right, we do61 * have to carefully manage the calling context because we can only register62 * input handlers from task context.63 *64 * In particular we need to trigger the action from the debug trap handler with65 * all its NMI and/or NMI-like oddities. To solve this the kgdboc trap exit code66 * (the "post_exception" callback) uses irq_work_queue(), which is NMI-safe, to67 * schedule a callback from a hardirq context. From there we have to defer the68 * work again, this time using schedule_work(), to get a callback using the69 * system workqueue, which runs in task context.70 */71#ifdef CONFIG_KDB_KEYBOARD72static int kgdboc_reset_connect(struct input_handler *handler,73 struct input_dev *dev,74 const struct input_device_id *id)75{76 input_reset_device(dev);77 78 /* Return an error - we do not want to bind, just to reset */79 return -ENODEV;80}81 82static void kgdboc_reset_disconnect(struct input_handle *handle)83{84 /* We do not expect anyone to actually bind to us */85 BUG();86}87 88static const struct input_device_id kgdboc_reset_ids[] = {89 {90 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,91 .evbit = { BIT_MASK(EV_KEY) },92 },93 { }94};95 96static struct input_handler kgdboc_reset_handler = {97 .connect = kgdboc_reset_connect,98 .disconnect = kgdboc_reset_disconnect,99 .name = "kgdboc_reset",100 .id_table = kgdboc_reset_ids,101};102 103static DEFINE_MUTEX(kgdboc_reset_mutex);104 105static void kgdboc_restore_input_helper(struct work_struct *dummy)106{107 /*108 * We need to take a mutex to prevent several instances of109 * this work running on different CPUs so they don't try110 * to register again already registered handler.111 */112 mutex_lock(&kgdboc_reset_mutex);113 114 if (input_register_handler(&kgdboc_reset_handler) == 0)115 input_unregister_handler(&kgdboc_reset_handler);116 117 mutex_unlock(&kgdboc_reset_mutex);118}119 120static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);121 122static void kgdboc_queue_restore_input_helper(struct irq_work *unused)123{124 schedule_work(&kgdboc_restore_input_work);125}126 127static DEFINE_IRQ_WORK(kgdboc_restore_input_irq_work, kgdboc_queue_restore_input_helper);128 129static void kgdboc_restore_input(void)130{131 if (likely(system_state == SYSTEM_RUNNING))132 irq_work_queue(&kgdboc_restore_input_irq_work);133}134 135static int kgdboc_register_kbd(char **cptr)136{137 if (strncmp(*cptr, "kbd", 3) == 0 ||138 strncmp(*cptr, "kdb", 3) == 0) {139 if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {140 kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;141 kdb_poll_idx++;142 if (cptr[0][3] == ',')143 *cptr += 4;144 else145 return 1;146 }147 }148 return 0;149}150 151static void kgdboc_unregister_kbd(void)152{153 int i;154 155 for (i = 0; i < kdb_poll_idx; i++) {156 if (kdb_poll_funcs[i] == kdb_get_kbd_char) {157 kdb_poll_idx--;158 kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];159 kdb_poll_funcs[kdb_poll_idx] = NULL;160 i--;161 }162 }163 irq_work_sync(&kgdboc_restore_input_irq_work);164 flush_work(&kgdboc_restore_input_work);165}166#else /* ! CONFIG_KDB_KEYBOARD */167#define kgdboc_register_kbd(x) 0168#define kgdboc_unregister_kbd()169#define kgdboc_restore_input()170#endif /* ! CONFIG_KDB_KEYBOARD */171 172#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)173static void cleanup_earlycon(void)174{175 if (kgdboc_earlycon_io_ops.cons)176 kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);177}178#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */179static inline void cleanup_earlycon(void) { }180#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */181 182static void cleanup_kgdboc(void)183{184 cleanup_earlycon();185 186 if (configured != 1)187 return;188 189 if (kgdb_unregister_nmi_console())190 return;191 kgdboc_unregister_kbd();192 kgdb_unregister_io_module(&kgdboc_io_ops);193}194 195static int configure_kgdboc(void)196{197 struct tty_driver *p;198 int tty_line = 0;199 int err = -ENODEV;200 char *cptr = config;201 struct console *cons;202 int cookie;203 204 if (!strlen(config) || isspace(config[0])) {205 err = 0;206 goto noconfig;207 }208 209 kgdboc_io_ops.cons = NULL;210 kgdb_tty_driver = NULL;211 212 kgdboc_use_kms = 0;213 if (strncmp(cptr, "kms,", 4) == 0) {214 cptr += 4;215 kgdboc_use_kms = 1;216 }217 218 if (kgdboc_register_kbd(&cptr))219 goto do_register;220 221 p = tty_find_polling_driver(cptr, &tty_line);222 if (!p)223 goto noconfig;224 225 /*226 * Take console_lock to serialize device() callback with227 * other console operations. For example, fg_console is228 * modified under console_lock when switching vt.229 */230 console_lock();231 232 cookie = console_srcu_read_lock();233 for_each_console_srcu(cons) {234 int idx;235 if (cons->device && cons->device(cons, &idx) == p &&236 idx == tty_line) {237 kgdboc_io_ops.cons = cons;238 break;239 }240 }241 console_srcu_read_unlock(cookie);242 243 console_unlock();244 245 kgdb_tty_driver = p;246 kgdb_tty_line = tty_line;247 248do_register:249 err = kgdb_register_io_module(&kgdboc_io_ops);250 if (err)251 goto noconfig;252 253 err = kgdb_register_nmi_console();254 if (err)255 goto nmi_con_failed;256 257 configured = 1;258 259 return 0;260 261nmi_con_failed:262 kgdb_unregister_io_module(&kgdboc_io_ops);263noconfig:264 kgdboc_unregister_kbd();265 configured = 0;266 267 return err;268}269 270static int kgdboc_probe(struct platform_device *pdev)271{272 int ret = 0;273 274 mutex_lock(&config_mutex);275 if (configured != 1) {276 ret = configure_kgdboc();277 278 /* Convert "no device" to "defer" so we'll keep trying */279 if (ret == -ENODEV)280 ret = -EPROBE_DEFER;281 }282 mutex_unlock(&config_mutex);283 284 return ret;285}286 287static struct platform_driver kgdboc_platform_driver = {288 .probe = kgdboc_probe,289 .driver = {290 .name = "kgdboc",291 .suppress_bind_attrs = true,292 },293};294 295static int __init init_kgdboc(void)296{297 int ret;298 299 /*300 * kgdboc is a little bit of an odd "platform_driver". It can be301 * up and running long before the platform_driver object is302 * created and thus doesn't actually store anything in it. There's303 * only one instance of kgdb so anything is stored as global state.304 * The platform_driver is only created so that we can leverage the305 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our306 * underlying tty is ready. Here we init our platform driver and307 * then create the single kgdboc instance.308 */309 ret = platform_driver_register(&kgdboc_platform_driver);310 if (ret)311 return ret;312 313 kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);314 if (!kgdboc_pdev) {315 ret = -ENOMEM;316 goto err_did_register;317 }318 319 ret = platform_device_add(kgdboc_pdev);320 if (!ret)321 return 0;322 323 platform_device_put(kgdboc_pdev);324 325err_did_register:326 platform_driver_unregister(&kgdboc_platform_driver);327 return ret;328}329 330static void exit_kgdboc(void)331{332 mutex_lock(&config_mutex);333 cleanup_kgdboc();334 mutex_unlock(&config_mutex);335 336 platform_device_unregister(kgdboc_pdev);337 platform_driver_unregister(&kgdboc_platform_driver);338}339 340static int kgdboc_get_char(void)341{342 if (!kgdb_tty_driver)343 return -1;344 return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,345 kgdb_tty_line);346}347 348static void kgdboc_put_char(u8 chr)349{350 if (!kgdb_tty_driver)351 return;352 kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,353 kgdb_tty_line, chr);354}355 356static int param_set_kgdboc_var(const char *kmessage,357 const struct kernel_param *kp)358{359 size_t len = strlen(kmessage);360 int ret = 0;361 362 if (len >= MAX_CONFIG_LEN) {363 pr_err("config string too long\n");364 return -ENOSPC;365 }366 367 if (kgdb_connected) {368 pr_err("Cannot reconfigure while KGDB is connected.\n");369 return -EBUSY;370 }371 372 mutex_lock(&config_mutex);373 374 strcpy(config, kmessage);375 /* Chop out \n char as a result of echo */376 if (len && config[len - 1] == '\n')377 config[len - 1] = '\0';378 379 if (configured == 1)380 cleanup_kgdboc();381 382 /*383 * Configure with the new params as long as init already ran.384 * Note that we can get called before init if someone loads us385 * with "modprobe kgdboc kgdboc=..." or if they happen to use386 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.387 */388 if (configured >= 0)389 ret = configure_kgdboc();390 391 /*392 * If we couldn't configure then clear out the config. Note that393 * specifying an invalid config on the kernel command line vs.394 * through sysfs have slightly different behaviors. If we fail395 * to configure what was specified on the kernel command line396 * we'll leave it in the 'config' and return -EPROBE_DEFER from397 * our probe. When specified through sysfs userspace is398 * responsible for loading the tty driver before setting up.399 */400 if (ret)401 config[0] = '\0';402 403 mutex_unlock(&config_mutex);404 405 return ret;406}407 408static int dbg_restore_graphics;409 410static void kgdboc_pre_exp_handler(void)411{412 if (!dbg_restore_graphics && kgdboc_use_kms) {413 dbg_restore_graphics = 1;414 con_debug_enter(vc_cons[fg_console].d);415 }416 /* Increment the module count when the debugger is active */417 if (!kgdb_connected)418 try_module_get(THIS_MODULE);419}420 421static void kgdboc_post_exp_handler(void)422{423 /* decrement the module count when the debugger detaches */424 if (!kgdb_connected)425 module_put(THIS_MODULE);426 if (kgdboc_use_kms && dbg_restore_graphics) {427 dbg_restore_graphics = 0;428 con_debug_leave();429 }430 kgdboc_restore_input();431}432 433static struct kgdb_io kgdboc_io_ops = {434 .name = "kgdboc",435 .read_char = kgdboc_get_char,436 .write_char = kgdboc_put_char,437 .pre_exception = kgdboc_pre_exp_handler,438 .post_exception = kgdboc_post_exp_handler,439};440 441#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)442static int kgdboc_option_setup(char *opt)443{444 if (!opt) {445 pr_err("config string not provided\n");446 return 1;447 }448 449 if (strlen(opt) >= MAX_CONFIG_LEN) {450 pr_err("config string too long\n");451 return 1;452 }453 strcpy(config, opt);454 455 return 1;456}457 458__setup("kgdboc=", kgdboc_option_setup);459 460 461/* This is only available if kgdboc is a built in for early debugging */462static int __init kgdboc_early_init(char *opt)463{464 kgdboc_option_setup(opt);465 configure_kgdboc();466 return 0;467}468 469early_param("ekgdboc", kgdboc_early_init);470 471static int kgdboc_earlycon_get_char(void)472{473 char c;474 475 if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,476 &c, 1))477 return NO_POLL_CHAR;478 479 return c;480}481 482static void kgdboc_earlycon_put_char(u8 chr)483{484 kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,485 1);486}487 488static void kgdboc_earlycon_pre_exp_handler(void)489{490 struct console *con;491 static bool already_warned;492 int cookie;493 494 if (already_warned)495 return;496 497 /*498 * When the first normal console comes up the kernel will take all499 * the boot consoles out of the list. Really, we should stop using500 * the boot console when it does that but until a TTY is registered501 * we have no other choice so we keep using it. Since not all502 * serial drivers might be OK with this, print a warning once per503 * boot if we detect this case.504 */505 cookie = console_srcu_read_lock();506 for_each_console_srcu(con) {507 if (con == kgdboc_earlycon_io_ops.cons)508 break;509 }510 console_srcu_read_unlock(cookie);511 if (con)512 return;513 514 already_warned = true;515 pr_warn("kgdboc_earlycon is still using bootconsole\n");516}517 518static int kgdboc_earlycon_deferred_exit(struct console *con)519{520 /*521 * If we get here it means the boot console is going away but we522 * don't yet have a suitable replacement. Don't pass through to523 * the original exit routine. We'll call it later in our deinit()524 * function. For now, restore the original exit() function pointer525 * as a sentinal that we've hit this point.526 */527 con->exit = earlycon_orig_exit;528 529 return 0;530}531 532static void kgdboc_earlycon_deinit(void)533{534 if (!kgdboc_earlycon_io_ops.cons)535 return;536 537 if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)538 /*539 * kgdboc_earlycon is exiting but original boot console exit540 * was never called (AKA kgdboc_earlycon_deferred_exit()541 * didn't ever run). Undo our trap.542 */543 kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;544 else if (kgdboc_earlycon_io_ops.cons->exit)545 /*546 * We skipped calling the exit() routine so we could try to547 * keep using the boot console even after it went away. We're548 * finally done so call the function now.549 */550 kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);551 552 kgdboc_earlycon_io_ops.cons = NULL;553}554 555static struct kgdb_io kgdboc_earlycon_io_ops = {556 .name = "kgdboc_earlycon",557 .read_char = kgdboc_earlycon_get_char,558 .write_char = kgdboc_earlycon_put_char,559 .pre_exception = kgdboc_earlycon_pre_exp_handler,560 .deinit = kgdboc_earlycon_deinit,561};562 563#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)564static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;565static bool kgdboc_earlycon_late_enable __initdata;566 567static int __init kgdboc_earlycon_init(char *opt)568{569 struct console *con;570 571 kdb_init(KDB_INIT_EARLY);572 573 /*574 * Look for a matching console, or if the name was left blank just575 * pick the first one we find.576 */577 578 /*579 * Hold the console_list_lock to guarantee that no consoles are580 * unregistered until the kgdboc_earlycon setup is complete.581 * Trapping the exit() callback relies on exit() not being582 * called until the trap is setup. This also allows safe583 * traversal of the console list and race-free reading of @flags.584 */585 console_list_lock();586 for_each_console(con) {587 if (con->write && con->read &&588 (con->flags & (CON_BOOT | CON_ENABLED)) &&589 (!opt || !opt[0] || strcmp(con->name, opt) == 0))590 break;591 }592 593 if (!con) {594 /*595 * Both earlycon and kgdboc_earlycon are initialized during596 * early parameter parsing. We cannot guarantee earlycon gets597 * in first and, in any case, on ACPI systems earlycon may598 * defer its own initialization (usually to somewhere within599 * setup_arch() ). To cope with either of these situations600 * we can defer our own initialization to a little later in601 * the boot.602 */603 if (!kgdboc_earlycon_late_enable) {604 pr_info("No suitable earlycon yet, will try later\n");605 if (opt)606 strscpy(kgdboc_earlycon_param, opt,607 sizeof(kgdboc_earlycon_param));608 kgdboc_earlycon_late_enable = true;609 } else {610 pr_info("Couldn't find kgdb earlycon\n");611 }612 goto unlock;613 }614 615 kgdboc_earlycon_io_ops.cons = con;616 pr_info("Going to register kgdb with earlycon '%s'\n", con->name);617 if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {618 kgdboc_earlycon_io_ops.cons = NULL;619 pr_info("Failed to register kgdb with earlycon\n");620 } else {621 /* Trap exit so we can keep earlycon longer if needed. */622 earlycon_orig_exit = con->exit;623 con->exit = kgdboc_earlycon_deferred_exit;624 }625 626unlock:627 console_list_unlock();628 629 /* Non-zero means malformed option so we always return zero */630 return 0;631}632 633early_param("kgdboc_earlycon", kgdboc_earlycon_init);634 635/*636 * This is only intended for the late adoption of an early console.637 *638 * It is not a reliable way to adopt regular consoles because we can not639 * control what order console initcalls are made and, in any case, many640 * regular consoles are registered much later in the boot process than641 * the console initcalls!642 */643static int __init kgdboc_earlycon_late_init(void)644{645 if (kgdboc_earlycon_late_enable)646 kgdboc_earlycon_init(kgdboc_earlycon_param);647 return 0;648}649console_initcall(kgdboc_earlycon_late_init);650 651#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */652 653module_init(init_kgdboc);654module_exit(exit_kgdboc);655module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);656MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");657MODULE_DESCRIPTION("KGDB Console TTY Driver");658MODULE_LICENSE("GPL");659