linux/lib/dynamic_printk.c
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   1/*
   2 * lib/dynamic_printk.c
   3 *
   4 * make pr_debug()/dev_dbg() calls runtime configurable based upon their
   5 * their source module.
   6 *
   7 * Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com>
   8 */
   9
  10#include <linux/kernel.h>
  11#include <linux/module.h>
  12#include <linux/uaccess.h>
  13#include <linux/seq_file.h>
  14#include <linux/debugfs.h>
  15#include <linux/fs.h>
  16
  17extern struct mod_debug __start___verbose[];
  18extern struct mod_debug __stop___verbose[];
  19
  20struct debug_name {
  21        struct hlist_node hlist;
  22        struct hlist_node hlist2;
  23        int hash1;
  24        int hash2;
  25        char *name;
  26        int enable;
  27        int type;
  28};
  29
  30static int nr_entries;
  31static int num_enabled;
  32int dynamic_enabled = DYNAMIC_ENABLED_NONE;
  33static struct hlist_head module_table[DEBUG_HASH_TABLE_SIZE] =
  34        { [0 ... DEBUG_HASH_TABLE_SIZE-1] = HLIST_HEAD_INIT };
  35static struct hlist_head module_table2[DEBUG_HASH_TABLE_SIZE] =
  36        { [0 ... DEBUG_HASH_TABLE_SIZE-1] = HLIST_HEAD_INIT };
  37static DECLARE_MUTEX(debug_list_mutex);
  38
  39/* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which
  40 * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They
  41 * use independent hash functions, to reduce the chance of false positives.
  42 */
  43long long dynamic_printk_enabled;
  44EXPORT_SYMBOL_GPL(dynamic_printk_enabled);
  45long long dynamic_printk_enabled2;
  46EXPORT_SYMBOL_GPL(dynamic_printk_enabled2);
  47
  48/* returns the debug module pointer. */
  49static struct debug_name *find_debug_module(char *module_name)
  50{
  51        int i;
  52        struct hlist_head *head;
  53        struct hlist_node *node;
  54        struct debug_name *element;
  55
  56        element = NULL;
  57        for (i = 0; i < DEBUG_HASH_TABLE_SIZE; i++) {
  58                head = &module_table[i];
  59                hlist_for_each_entry_rcu(element, node, head, hlist)
  60                        if (!strcmp(element->name, module_name))
  61                                return element;
  62        }
  63        return NULL;
  64}
  65
  66/* returns the debug module pointer. */
  67static struct debug_name *find_debug_module_hash(char *module_name, int hash)
  68{
  69        struct hlist_head *head;
  70        struct hlist_node *node;
  71        struct debug_name *element;
  72
  73        element = NULL;
  74        head = &module_table[hash];
  75        hlist_for_each_entry_rcu(element, node, head, hlist)
  76                if (!strcmp(element->name, module_name))
  77                        return element;
  78        return NULL;
  79}
  80
  81/* caller must hold mutex*/
  82static int __add_debug_module(char *mod_name, int hash, int hash2)
  83{
  84        struct debug_name *new;
  85        char *module_name;
  86        int ret = 0;
  87
  88        if (find_debug_module(mod_name)) {
  89                ret = -EINVAL;
  90                goto out;
  91        }
  92        module_name = kmalloc(strlen(mod_name) + 1, GFP_KERNEL);
  93        if (!module_name) {
  94                ret = -ENOMEM;
  95                goto out;
  96        }
  97        module_name = strcpy(module_name, mod_name);
  98        module_name[strlen(mod_name)] = '\0';
  99        new = kzalloc(sizeof(struct debug_name), GFP_KERNEL);
 100        if (!new) {
 101                kfree(module_name);
 102                ret = -ENOMEM;
 103                goto out;
 104        }
 105        INIT_HLIST_NODE(&new->hlist);
 106        INIT_HLIST_NODE(&new->hlist2);
 107        new->name = module_name;
 108        new->hash1 = hash;
 109        new->hash2 = hash2;
 110        hlist_add_head_rcu(&new->hlist, &module_table[hash]);
 111        hlist_add_head_rcu(&new->hlist2, &module_table2[hash2]);
 112        nr_entries++;
 113out:
 114        return ret;
 115}
 116
 117int unregister_dynamic_debug_module(char *mod_name)
 118{
 119        struct debug_name *element;
 120        int ret = 0;
 121
 122        down(&debug_list_mutex);
 123        element = find_debug_module(mod_name);
 124        if (!element) {
 125                ret = -EINVAL;
 126                goto out;
 127        }
 128        hlist_del_rcu(&element->hlist);
 129        hlist_del_rcu(&element->hlist2);
 130        synchronize_rcu();
 131        kfree(element->name);
 132        if (element->enable)
 133                num_enabled--;
 134        kfree(element);
 135        nr_entries--;
 136out:
 137        up(&debug_list_mutex);
 138        return ret;
 139}
 140EXPORT_SYMBOL_GPL(unregister_dynamic_debug_module);
 141
 142int register_dynamic_debug_module(char *mod_name, int type, char *share_name,
 143                                        char *flags, int hash, int hash2)
 144{
 145        struct debug_name *elem;
 146        int ret = 0;
 147
 148        down(&debug_list_mutex);
 149        elem = find_debug_module(mod_name);
 150        if (!elem) {
 151                if (__add_debug_module(mod_name, hash, hash2))
 152                        goto out;
 153                elem = find_debug_module(mod_name);
 154                if (dynamic_enabled == DYNAMIC_ENABLED_ALL &&
 155                                !strcmp(mod_name, share_name)) {
 156                        elem->enable = true;
 157                        num_enabled++;
 158                }
 159        }
 160        elem->type |= type;
 161out:
 162        up(&debug_list_mutex);
 163        return ret;
 164}
 165EXPORT_SYMBOL_GPL(register_dynamic_debug_module);
 166
 167int __dynamic_dbg_enabled_helper(char *mod_name, int type, int value, int hash)
 168{
 169        struct debug_name *elem;
 170        int ret = 0;
 171
 172        if (dynamic_enabled == DYNAMIC_ENABLED_ALL)
 173                return 1;
 174        rcu_read_lock();
 175        elem = find_debug_module_hash(mod_name, hash);
 176        if (elem && elem->enable)
 177                ret = 1;
 178        rcu_read_unlock();
 179        return ret;
 180}
 181EXPORT_SYMBOL_GPL(__dynamic_dbg_enabled_helper);
 182
 183static void set_all(bool enable)
 184{
 185        struct debug_name *e;
 186        struct hlist_node *node;
 187        int i;
 188        long long enable_mask;
 189
 190        for (i = 0; i < DEBUG_HASH_TABLE_SIZE; i++) {
 191                if (module_table[i].first != NULL) {
 192                        hlist_for_each_entry(e, node, &module_table[i], hlist) {
 193                                e->enable = enable;
 194                        }
 195                }
 196        }
 197        if (enable)
 198                enable_mask = ULLONG_MAX;
 199        else
 200                enable_mask = 0;
 201        dynamic_printk_enabled = enable_mask;
 202        dynamic_printk_enabled2 = enable_mask;
 203}
 204
 205static int disabled_hash(int i, bool first_table)
 206{
 207        struct debug_name *e;
 208        struct hlist_node *node;
 209
 210        if (first_table) {
 211                hlist_for_each_entry(e, node, &module_table[i], hlist) {
 212                        if (e->enable)
 213                                return 0;
 214                }
 215        } else {
 216                hlist_for_each_entry(e, node, &module_table2[i], hlist2) {
 217                        if (e->enable)
 218                                return 0;
 219                }
 220        }
 221        return 1;
 222}
 223
 224static ssize_t pr_debug_write(struct file *file, const char __user *buf,
 225                                size_t length, loff_t *ppos)
 226{
 227        char *buffer, *s, *value_str, *setting_str;
 228        int err, value;
 229        struct debug_name *elem = NULL;
 230        int all = 0;
 231
 232        if (length > PAGE_SIZE || length < 0)
 233                return -EINVAL;
 234
 235        buffer = (char *)__get_free_page(GFP_KERNEL);
 236        if (!buffer)
 237                return -ENOMEM;
 238
 239        err = -EFAULT;
 240        if (copy_from_user(buffer, buf, length))
 241                goto out;
 242
 243        err = -EINVAL;
 244        if (length < PAGE_SIZE)
 245                buffer[length] = '\0';
 246        else if (buffer[PAGE_SIZE-1])
 247                goto out;
 248
 249        err = -EINVAL;
 250        down(&debug_list_mutex);
 251
 252        if (strncmp("set", buffer, 3))
 253                goto out_up;
 254        s = buffer + 3;
 255        setting_str = strsep(&s, "=");
 256        if (s == NULL)
 257                goto out_up;
 258        setting_str = strstrip(setting_str);
 259        value_str = strsep(&s, " ");
 260        if (s == NULL)
 261                goto out_up;
 262        s = strstrip(s);
 263        if (!strncmp(s, "all", 3))
 264                all = 1;
 265        else
 266                elem = find_debug_module(s);
 267        if (!strncmp(setting_str, "enable", 6)) {
 268                value = !!simple_strtol(value_str, NULL, 10);
 269                if (all) {
 270                        if (value) {
 271                                set_all(true);
 272                                num_enabled = nr_entries;
 273                                dynamic_enabled = DYNAMIC_ENABLED_ALL;
 274                        } else {
 275                                set_all(false);
 276                                num_enabled = 0;
 277                                dynamic_enabled = DYNAMIC_ENABLED_NONE;
 278                        }
 279                        err = 0;
 280                } else if (elem) {
 281                        if (value && (elem->enable == 0)) {
 282                                dynamic_printk_enabled |= (1LL << elem->hash1);
 283                                dynamic_printk_enabled2 |= (1LL << elem->hash2);
 284                                elem->enable = 1;
 285                                num_enabled++;
 286                                dynamic_enabled = DYNAMIC_ENABLED_SOME;
 287                                err = 0;
 288                                printk(KERN_DEBUG
 289                                        "debugging enabled for module %s\n",
 290                                        elem->name);
 291                        } else if (!value && (elem->enable == 1)) {
 292                                elem->enable = 0;
 293                                num_enabled--;
 294                                if (disabled_hash(elem->hash1, true))
 295                                        dynamic_printk_enabled &=
 296                                                        ~(1LL << elem->hash1);
 297                                if (disabled_hash(elem->hash2, false))
 298                                        dynamic_printk_enabled2 &=
 299                                                        ~(1LL << elem->hash2);
 300                                if (num_enabled)
 301                                        dynamic_enabled = DYNAMIC_ENABLED_SOME;
 302                                else
 303                                        dynamic_enabled = DYNAMIC_ENABLED_NONE;
 304                                err = 0;
 305                                printk(KERN_DEBUG
 306                                        "debugging disabled for module %s\n",
 307                                        elem->name);
 308                        }
 309                }
 310        }
 311        if (!err)
 312                err = length;
 313out_up:
 314        up(&debug_list_mutex);
 315out:
 316        free_page((unsigned long)buffer);
 317        return err;
 318}
 319
 320static void *pr_debug_seq_start(struct seq_file *f, loff_t *pos)
 321{
 322        return (*pos < DEBUG_HASH_TABLE_SIZE) ? pos : NULL;
 323}
 324
 325static void *pr_debug_seq_next(struct seq_file *s, void *v, loff_t *pos)
 326{
 327        (*pos)++;
 328        if (*pos >= DEBUG_HASH_TABLE_SIZE)
 329                return NULL;
 330        return pos;
 331}
 332
 333static void pr_debug_seq_stop(struct seq_file *s, void *v)
 334{
 335        /* Nothing to do */
 336}
 337
 338static int pr_debug_seq_show(struct seq_file *s, void *v)
 339{
 340        struct hlist_head *head;
 341        struct hlist_node *node;
 342        struct debug_name *elem;
 343        unsigned int i = *(loff_t *) v;
 344
 345        rcu_read_lock();
 346        head = &module_table[i];
 347        hlist_for_each_entry_rcu(elem, node, head, hlist) {
 348                seq_printf(s, "%s enabled=%d", elem->name, elem->enable);
 349                seq_printf(s, "\n");
 350        }
 351        rcu_read_unlock();
 352        return 0;
 353}
 354
 355static struct seq_operations pr_debug_seq_ops = {
 356        .start = pr_debug_seq_start,
 357        .next  = pr_debug_seq_next,
 358        .stop  = pr_debug_seq_stop,
 359        .show  = pr_debug_seq_show
 360};
 361
 362static int pr_debug_open(struct inode *inode, struct file *filp)
 363{
 364        return seq_open(filp, &pr_debug_seq_ops);
 365}
 366
 367static const struct file_operations pr_debug_operations = {
 368        .open           = pr_debug_open,
 369        .read           = seq_read,
 370        .write          = pr_debug_write,
 371        .llseek         = seq_lseek,
 372        .release        = seq_release,
 373};
 374
 375static int __init dynamic_printk_init(void)
 376{
 377        struct dentry *dir, *file;
 378        struct mod_debug *iter;
 379        unsigned long value;
 380
 381        dir = debugfs_create_dir("dynamic_printk", NULL);
 382        if (!dir)
 383                return -ENOMEM;
 384        file = debugfs_create_file("modules", 0644, dir, NULL,
 385                                        &pr_debug_operations);
 386        if (!file) {
 387                debugfs_remove(dir);
 388                return -ENOMEM;
 389        }
 390        for (value = (unsigned long)__start___verbose;
 391                value < (unsigned long)__stop___verbose;
 392                value += sizeof(struct mod_debug)) {
 393                        iter = (struct mod_debug *)value;
 394                        register_dynamic_debug_module(iter->modname,
 395                                iter->type,
 396                                iter->logical_modname,
 397                                iter->flag_names, iter->hash, iter->hash2);
 398        }
 399        if (dynamic_enabled == DYNAMIC_ENABLED_ALL)
 400                set_all(true);
 401        return 0;
 402}
 403module_init(dynamic_printk_init);
 404/* may want to move this earlier so we can get traces as early as possible */
 405
 406static int __init dynamic_printk_setup(char *str)
 407{
 408        if (str)
 409                return -ENOENT;
 410        dynamic_enabled = DYNAMIC_ENABLED_ALL;
 411        return 0;
 412}
 413/* Use early_param(), so we can get debug output as early as possible */
 414early_param("dynamic_printk", dynamic_printk_setup);
 415