drivers/serial/kgdboc.c

   1 /*
   2  * Based on the same principle as kgdboe using the NETPOLL api, this
   3  * driver uses a console polling api to implement a gdb serial inteface
   4  * which is multiplexed on a console port.
   5  *
   6  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
   7  *
   8  * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
   9  *
  10  * This file is licensed under the terms of the GNU General Public
  11  * License version 2. This program is licensed "as is" without any
  12  * warranty of any kind, whether express or implied.
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/ctype.h>
  16 #include <linux/kgdb.h>
  17 #include <linux/tty.h>
  18
  19 #define MAX_CONFIG_LEN          40
  20
  21 static struct kgdb_io           kgdboc_io_ops;
  22
  23 /* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
  24 static int configured           = -1;
  25
  26 static char config[MAX_CONFIG_LEN];
  27 static struct kparam_string kps = {
  28         .string                 = config,
  29         .maxlen                 = MAX_CONFIG_LEN,
  30 };
  31
  32 static struct tty_driver        *kgdb_tty_driver;
  33 static int                      kgdb_tty_line;
  34
  35 static int kgdboc_option_setup(char *opt)
  36 {
  37         if (strlen(opt) > MAX_CONFIG_LEN) {
  38                 printk(KERN_ERR "kgdboc: config string too long\n");
  39                 return -ENOSPC;
  40         }
  41         strcpy(config, opt);
  42
  43         return 0;
  44 }
  45
  46 __setup("kgdboc=", kgdboc_option_setup);
  47
  48 static int configure_kgdboc(void)
  49 {
  50         struct tty_driver *p;
  51         int tty_line = 0;
  52         int err;
  53
  54         err = kgdboc_option_setup(config);
  55         if (err || !strlen(config) || isspace(config[0]))
  56                 goto noconfig;
  57
  58         err = -ENODEV;
  59
  60         p = tty_find_polling_driver(config, &tty_line);
  61         if (!p)
  62                 goto noconfig;
  63
  64         kgdb_tty_driver = p;
  65         kgdb_tty_line = tty_line;
  66
  67         err = kgdb_register_io_module(&kgdboc_io_ops);
  68         if (err)
  69                 goto noconfig;
  70
  71         configured = 1;
  72
  73         return 0;
  74
  75 noconfig:
  76         config[0] = 0;
  77         configured = 0;
  78
  79         return err;
  80 }
  81
  82 static int __init init_kgdboc(void)
  83 {
  84         /* Already configured? */
  85         if (configured == 1)
  86                 return 0;
  87
  88         return configure_kgdboc();
  89 }
  90
  91 static void cleanup_kgdboc(void)
  92 {
  93         if (configured == 1)
  94                 kgdb_unregister_io_module(&kgdboc_io_ops);
  95 }
  96
  97 static int kgdboc_get_char(void)
  98 {
  99         return kgdb_tty_driver->poll_get_char(kgdb_tty_driver, kgdb_tty_line);
 100 }
 101
 102 static void kgdboc_put_char(u8 chr)
 103 {
 104         kgdb_tty_driver->poll_put_char(kgdb_tty_driver, kgdb_tty_line, chr);
 105 }
 106
 107 static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
 108 {
 109         int len = strlen(kmessage);
 110
 111         if (len >= MAX_CONFIG_LEN) {
 112                 printk(KERN_ERR "kgdboc: config string too long\n");
 113                 return -ENOSPC;
 114         }
 115
 116         /* Only copy in the string if the init function has not run yet */
 117         if (configured < 0) {
 118                 strcpy(config, kmessage);
 119                 return 0;
 120         }
 121
 122         if (kgdb_connected) {
 123                 printk(KERN_ERR
 124                        "kgdboc: Cannot reconfigure while KGDB is connected.\n");
 125
 126                 return -EBUSY;
 127         }
 128
 129         strcpy(config, kmessage);
 130         /* Chop out \n char as a result of echo */
 131         if (config[len - 1] == '\n')
 132                 config[len - 1] = '\0';
 133
 134         if (configured == 1)
 135                 cleanup_kgdboc();
 136
 137         /* Go and configure with the new params. */
 138         return configure_kgdboc();
 139 }
 140
 141 static void kgdboc_pre_exp_handler(void)
 142 {
 143         /* Increment the module count when the debugger is active */
 144         if (!kgdb_connected)
 145                 try_module_get(THIS_MODULE);
 146 }
 147
 148 static void kgdboc_post_exp_handler(void)
 149 {
 150         /* decrement the module count when the debugger detaches */
 151         if (!kgdb_connected)
 152                 module_put(THIS_MODULE);
 153 }
 154
 155 static struct kgdb_io kgdboc_io_ops = {
 156         .name                   = "kgdboc",
 157         .read_char              = kgdboc_get_char,
 158         .write_char             = kgdboc_put_char,
 159         .pre_exception          = kgdboc_pre_exp_handler,
 160         .post_exception         = kgdboc_post_exp_handler,
 161 };
 162
 163 module_init(init_kgdboc);
 164 module_exit(cleanup_kgdboc);
 165 module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
 166 MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
 167 MODULE_DESCRIPTION("KGDB Console TTY Driver");
 168 MODULE_LICENSE("GPL");