drivers/tty/serial/kgdboc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Based on the same principle as kgdboe using the NETPOLL api, this
   4  * driver uses a console polling api to implement a gdb serial inteface
   5  * 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 #include <linux/kernel.h>
  12 #include <linux/ctype.h>
  13 #include <linux/kgdb.h>
  14 #include <linux/kdb.h>
  15 #include <linux/tty.h>
  16 #include <linux/console.h>
  17 #include <linux/vt_kern.h>
  18 #include <linux/input.h>
  19 #include <linux/module.h>
  20
  21 #define MAX_CONFIG_LEN          40
  22
  23 static struct kgdb_io           kgdboc_io_ops;
  24
  25 /* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
  26 static int configured           = -1;
  27
  28 static char config[MAX_CONFIG_LEN];
  29 static struct kparam_string kps = {
  30         .string                 = config,
  31         .maxlen                 = MAX_CONFIG_LEN,
  32 };
  33
  34 static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
  35 static struct tty_driver        *kgdb_tty_driver;
  36 static int                      kgdb_tty_line;
  37
  38 #ifdef CONFIG_KDB_KEYBOARD
  39 static int kgdboc_reset_connect(struct input_handler *handler,
  40                                 struct input_dev *dev,
  41                                 const struct input_device_id *id)
  42 {
  43         input_reset_device(dev);
  44
  45         /* Return an error - we do not want to bind, just to reset */
  46         return -ENODEV;
  47 }
  48
  49 static void kgdboc_reset_disconnect(struct input_handle *handle)
  50 {
  51         /* We do not expect anyone to actually bind to us */
  52         BUG();
  53 }
  54
  55 static const struct input_device_id kgdboc_reset_ids[] = {
  56         {
  57                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
  58                 .evbit = { BIT_MASK(EV_KEY) },
  59         },
  60         { }
  61 };
  62
  63 static struct input_handler kgdboc_reset_handler = {
  64         .connect        = kgdboc_reset_connect,
  65         .disconnect     = kgdboc_reset_disconnect,
  66         .name           = "kgdboc_reset",
  67         .id_table       = kgdboc_reset_ids,
  68 };
  69
  70 static DEFINE_MUTEX(kgdboc_reset_mutex);
  71
  72 static void kgdboc_restore_input_helper(struct work_struct *dummy)
  73 {
  74         /*
  75          * We need to take a mutex to prevent several instances of
  76          * this work running on different CPUs so they don't try
  77          * to register again already registered handler.
  78          */
  79         mutex_lock(&kgdboc_reset_mutex);
  80
  81         if (input_register_handler(&kgdboc_reset_handler) == 0)
  82                 input_unregister_handler(&kgdboc_reset_handler);
  83
  84         mutex_unlock(&kgdboc_reset_mutex);
  85 }
  86
  87 static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
  88
  89 static void kgdboc_restore_input(void)
  90 {
  91         if (likely(system_state == SYSTEM_RUNNING))
  92                 schedule_work(&kgdboc_restore_input_work);
  93 }
  94
  95 static int kgdboc_register_kbd(char **cptr)
  96 {
  97         if (strncmp(*cptr, "kbd", 3) == 0 ||
  98                 strncmp(*cptr, "kdb", 3) == 0) {
  99                 if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
 100                         kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
 101                         kdb_poll_idx++;
 102                         if (cptr[0][3] == ',')
 103                                 *cptr += 4;
 104                         else
 105                                 return 1;
 106                 }
 107         }
 108         return 0;
 109 }
 110
 111 static void kgdboc_unregister_kbd(void)
 112 {
 113         int i;
 114
 115         for (i = 0; i < kdb_poll_idx; i++) {
 116                 if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
 117                         kdb_poll_idx--;
 118                         kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
 119                         kdb_poll_funcs[kdb_poll_idx] = NULL;
 120                         i--;
 121                 }
 122         }
 123         flush_work(&kgdboc_restore_input_work);
 124 }
 125 #else /* ! CONFIG_KDB_KEYBOARD */
 126 #define kgdboc_register_kbd(x) 0
 127 #define kgdboc_unregister_kbd()
 128 #define kgdboc_restore_input()
 129 #endif /* ! CONFIG_KDB_KEYBOARD */
 130
 131 static int kgdboc_option_setup(char *opt)
 132 {
 133         if (strlen(opt) >= MAX_CONFIG_LEN) {
 134                 printk(KERN_ERR "kgdboc: config string too long\n");
 135                 return -ENOSPC;
 136         }
 137         strcpy(config, opt);
 138
 139         return 0;
 140 }
 141
 142 __setup("kgdboc=", kgdboc_option_setup);
 143
 144 static void cleanup_kgdboc(void)
 145 {
 146         if (kgdb_unregister_nmi_console())
 147                 return;
 148         kgdboc_unregister_kbd();
 149         if (configured == 1)
 150                 kgdb_unregister_io_module(&kgdboc_io_ops);
 151 }
 152
 153 static int configure_kgdboc(void)
 154 {
 155         struct tty_driver *p;
 156         int tty_line = 0;
 157         int err;
 158         char *cptr = config;
 159         struct console *cons;
 160
 161         err = kgdboc_option_setup(config);
 162         if (err || !strlen(config) || isspace(config[0]))
 163                 goto noconfig;
 164
 165         err = -ENODEV;
 166         kgdboc_io_ops.is_console = 0;
 167         kgdb_tty_driver = NULL;
 168
 169         kgdboc_use_kms = 0;
 170         if (strncmp(cptr, "kms,", 4) == 0) {
 171                 cptr += 4;
 172                 kgdboc_use_kms = 1;
 173         }
 174
 175         if (kgdboc_register_kbd(&cptr))
 176                 goto do_register;
 177
 178         p = tty_find_polling_driver(cptr, &tty_line);
 179         if (!p)
 180                 goto noconfig;
 181
 182         cons = console_drivers;
 183         while (cons) {
 184                 int idx;
 185                 if (cons->device && cons->device(cons, &idx) == p &&
 186                     idx == tty_line) {
 187                         kgdboc_io_ops.is_console = 1;
 188                         break;
 189                 }
 190                 cons = cons->next;
 191         }
 192
 193         kgdb_tty_driver = p;
 194         kgdb_tty_line = tty_line;
 195
 196 do_register:
 197         err = kgdb_register_io_module(&kgdboc_io_ops);
 198         if (err)
 199                 goto noconfig;
 200
 201         err = kgdb_register_nmi_console();
 202         if (err)
 203                 goto nmi_con_failed;
 204
 205         configured = 1;
 206
 207         return 0;
 208
 209 nmi_con_failed:
 210         kgdb_unregister_io_module(&kgdboc_io_ops);
 211 noconfig:
 212         kgdboc_unregister_kbd();
 213         config[0] = 0;
 214         configured = 0;
 215         cleanup_kgdboc();
 216
 217         return err;
 218 }
 219
 220 static int __init init_kgdboc(void)
 221 {
 222         /* Already configured? */
 223         if (configured == 1)
 224                 return 0;
 225
 226         return configure_kgdboc();
 227 }
 228
 229 static int kgdboc_get_char(void)
 230 {
 231         if (!kgdb_tty_driver)
 232                 return -1;
 233         return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
 234                                                 kgdb_tty_line);
 235 }
 236
 237 static void kgdboc_put_char(u8 chr)
 238 {
 239         if (!kgdb_tty_driver)
 240                 return;
 241         kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
 242                                         kgdb_tty_line, chr);
 243 }
 244
 245 static int param_set_kgdboc_var(const char *kmessage,
 246                                 const struct kernel_param *kp)
 247 {
 248         int len = strlen(kmessage);
 249
 250         if (len >= MAX_CONFIG_LEN) {
 251                 printk(KERN_ERR "kgdboc: config string too long\n");
 252                 return -ENOSPC;
 253         }
 254
 255         /* Only copy in the string if the init function has not run yet */
 256         if (configured < 0) {
 257                 strcpy(config, kmessage);
 258                 return 0;
 259         }
 260
 261         if (kgdb_connected) {
 262                 printk(KERN_ERR
 263                        "kgdboc: Cannot reconfigure while KGDB is connected.\n");
 264
 265                 return -EBUSY;
 266         }
 267
 268         strcpy(config, kmessage);
 269         /* Chop out \n char as a result of echo */
 270         if (config[len - 1] == '\n')
 271                 config[len - 1] = '\0';
 272
 273         if (configured == 1)
 274                 cleanup_kgdboc();
 275
 276         /* Go and configure with the new params. */
 277         return configure_kgdboc();
 278 }
 279
 280 static int dbg_restore_graphics;
 281
 282 static void kgdboc_pre_exp_handler(void)
 283 {
 284         if (!dbg_restore_graphics && kgdboc_use_kms) {
 285                 dbg_restore_graphics = 1;
 286                 con_debug_enter(vc_cons[fg_console].d);
 287         }
 288         /* Increment the module count when the debugger is active */
 289         if (!kgdb_connected)
 290                 try_module_get(THIS_MODULE);
 291 }
 292
 293 static void kgdboc_post_exp_handler(void)
 294 {
 295         /* decrement the module count when the debugger detaches */
 296         if (!kgdb_connected)
 297                 module_put(THIS_MODULE);
 298         if (kgdboc_use_kms && dbg_restore_graphics) {
 299                 dbg_restore_graphics = 0;
 300                 con_debug_leave();
 301         }
 302         kgdboc_restore_input();
 303 }
 304
 305 static struct kgdb_io kgdboc_io_ops = {
 306         .name                   = "kgdboc",
 307         .read_char              = kgdboc_get_char,
 308         .write_char             = kgdboc_put_char,
 309         .pre_exception          = kgdboc_pre_exp_handler,
 310         .post_exception         = kgdboc_post_exp_handler,
 311 };
 312
 313 #ifdef CONFIG_KGDB_SERIAL_CONSOLE
 314 /* This is only available if kgdboc is a built in for early debugging */
 315 static int __init kgdboc_early_init(char *opt)
 316 {
 317         /* save the first character of the config string because the
 318          * init routine can destroy it.
 319          */
 320         char save_ch;
 321
 322         kgdboc_option_setup(opt);
 323         save_ch = config[0];
 324         init_kgdboc();
 325         config[0] = save_ch;
 326         return 0;
 327 }
 328
 329 early_param("ekgdboc", kgdboc_early_init);
 330 #endif /* CONFIG_KGDB_SERIAL_CONSOLE */
 331
 332 module_init(init_kgdboc);
 333 module_exit(cleanup_kgdboc);
 334 module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
 335 MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
 336 MODULE_DESCRIPTION("KGDB Console TTY Driver");
 337 MODULE_LICENSE("GPL");