drivers/firmware/dmi-sysfs.c

   1 /*
   2  * dmi-sysfs.c
   3  *
   4  * This module exports the DMI tables read-only to userspace through the
   5  * sysfs file system.
   6  *
   7  * Data is currently found below
   8  *    /sys/firmware/dmi/...
   9  *
  10  * DMI attributes are presented in attribute files with names
  11  * formatted using %d-%d, so that the first integer indicates the
  12  * structure type (0-255), and the second field is the instance of that
  13  * entry.
  14  *
  15  * Copyright 2011 Google, Inc.
  16  */
  17
  18 #include <linux/kernel.h>
  19 #include <linux/init.h>
  20 #include <linux/module.h>
  21 #include <linux/types.h>
  22 #include <linux/kobject.h>
  23 #include <linux/dmi.h>
  24 #include <linux/capability.h>
  25 #include <linux/slab.h>
  26 #include <linux/list.h>
  27 #include <linux/io.h>
  28
  29 #define MAX_ENTRY_TYPE 255 /* Most of these aren't used, but we consider
  30                               the top entry type is only 8 bits */
  31
  32 struct dmi_sysfs_entry {
  33         struct dmi_header dh;
  34         struct kobject kobj;
  35         int instance;
  36         int position;
  37         struct list_head list;
  38         struct kobject *child;
  39 };
  40
  41 /*
  42  * Global list of dmi_sysfs_entry.  Even though this should only be
  43  * manipulated at setup and teardown, the lazy nature of the kobject
  44  * system means we get lazy removes.
  45  */
  46 static LIST_HEAD(entry_list);
  47 static DEFINE_SPINLOCK(entry_list_lock);
  48
  49 /* dmi_sysfs_attribute - Top level attribute. used by all entries. */
  50 struct dmi_sysfs_attribute {
  51         struct attribute attr;
  52         ssize_t (*show)(struct dmi_sysfs_entry *entry, char *buf);
  53 };
  54
  55 #define DMI_SYSFS_ATTR(_entry, _name) \
  56 struct dmi_sysfs_attribute dmi_sysfs_attr_##_entry##_##_name = { \
  57         .attr = {.name = __stringify(_name), .mode = 0400}, \
  58         .show = dmi_sysfs_##_entry##_##_name, \
  59 }
  60
  61 /*
  62  * dmi_sysfs_mapped_attribute - Attribute where we require the entry be
  63  * mapped in.  Use in conjunction with dmi_sysfs_specialize_attr_ops.
  64  */
  65 struct dmi_sysfs_mapped_attribute {
  66         struct attribute attr;
  67         ssize_t (*show)(struct dmi_sysfs_entry *entry,
  68                         const struct dmi_header *dh,
  69                         char *buf);
  70 };
  71
  72 #define DMI_SYSFS_MAPPED_ATTR(_entry, _name) \
  73 struct dmi_sysfs_mapped_attribute dmi_sysfs_attr_##_entry##_##_name = { \
  74         .attr = {.name = __stringify(_name), .mode = 0400}, \
  75         .show = dmi_sysfs_##_entry##_##_name, \
  76 }
  77
  78 /*************************************************
  79  * Generic DMI entry support.
  80  *************************************************/
  81 static void dmi_entry_free(struct kobject *kobj)
  82 {
  83         kfree(kobj);
  84 }
  85
  86 static struct dmi_sysfs_entry *to_entry(struct kobject *kobj)
  87 {
  88         return container_of(kobj, struct dmi_sysfs_entry, kobj);
  89 }
  90
  91 static struct dmi_sysfs_attribute *to_attr(struct attribute *attr)
  92 {
  93         return container_of(attr, struct dmi_sysfs_attribute, attr);
  94 }
  95
  96 static ssize_t dmi_sysfs_attr_show(struct kobject *kobj,
  97                                    struct attribute *_attr, char *buf)
  98 {
  99         struct dmi_sysfs_entry *entry = to_entry(kobj);
 100         struct dmi_sysfs_attribute *attr = to_attr(_attr);
 101
 102         /* DMI stuff is only ever admin visible */
 103         if (!capable(CAP_SYS_ADMIN))
 104                 return -EACCES;
 105
 106         return attr->show(entry, buf);
 107 }
 108
 109 static const struct sysfs_ops dmi_sysfs_attr_ops = {
 110         .show = dmi_sysfs_attr_show,
 111 };
 112
 113 typedef ssize_t (*dmi_callback)(struct dmi_sysfs_entry *,
 114                                 const struct dmi_header *dh, void *);
 115
 116 struct find_dmi_data {
 117         struct dmi_sysfs_entry  *entry;
 118         dmi_callback            callback;
 119         void                    *private;
 120         int                     instance_countdown;
 121         ssize_t                 ret;
 122 };
 123
 124 static void find_dmi_entry_helper(const struct dmi_header *dh,
 125                                   void *_data)
 126 {
 127         struct find_dmi_data *data = _data;
 128         struct dmi_sysfs_entry *entry = data->entry;
 129
 130         /* Is this the entry we want? */
 131         if (dh->type != entry->dh.type)
 132                 return;
 133
 134         if (data->instance_countdown != 0) {
 135                 /* try the next instance? */
 136                 data->instance_countdown--;
 137                 return;
 138         }
 139
 140         /*
 141          * Don't ever revisit the instance.  Short circuit later
 142          * instances by letting the instance_countdown run negative
 143          */
 144         data->instance_countdown--;
 145
 146         /* Found the entry */
 147         data->ret = data->callback(entry, dh, data->private);
 148 }
 149
 150 /* State for passing the read parameters through dmi_find_entry() */
 151 struct dmi_read_state {
 152         char *buf;
 153         loff_t pos;
 154         size_t count;
 155 };
 156
 157 static ssize_t find_dmi_entry(struct dmi_sysfs_entry *entry,
 158                               dmi_callback callback, void *private)
 159 {
 160         struct find_dmi_data data = {
 161                 .entry = entry,
 162                 .callback = callback,
 163                 .private = private,
 164                 .instance_countdown = entry->instance,
 165                 .ret = -EIO,  /* To signal the entry disappeared */
 166         };
 167         int ret;
 168
 169         ret = dmi_walk(find_dmi_entry_helper, &data);
 170         /* This shouldn't happen, but just in case. */
 171         if (ret)
 172                 return -EINVAL;
 173         return data.ret;
 174 }
 175
 176 /*
 177  * Calculate and return the byte length of the dmi entry identified by
 178  * dh.  This includes both the formatted portion as well as the
 179  * unformatted string space, including the two trailing nul characters.
 180  */
 181 static size_t dmi_entry_length(const struct dmi_header *dh)
 182 {
 183         const char *p = (const char *)dh;
 184
 185         p += dh->length;
 186
 187         while (p[0] || p[1])
 188                 p++;
 189
 190         return 2 + p - (const char *)dh;
 191 }
 192
 193 /*************************************************
 194  * Support bits for specialized DMI entry support
 195  *************************************************/
 196 struct dmi_entry_attr_show_data {
 197         struct attribute *attr;
 198         char *buf;
 199 };
 200
 201 static ssize_t dmi_entry_attr_show_helper(struct dmi_sysfs_entry *entry,
 202                                           const struct dmi_header *dh,
 203                                           void *_data)
 204 {
 205         struct dmi_entry_attr_show_data *data = _data;
 206         struct dmi_sysfs_mapped_attribute *attr;
 207
 208         attr = container_of(data->attr,
 209                             struct dmi_sysfs_mapped_attribute, attr);
 210         return attr->show(entry, dh, data->buf);
 211 }
 212
 213 static ssize_t dmi_entry_attr_show(struct kobject *kobj,
 214                                    struct attribute *attr,
 215                                    char *buf)
 216 {
 217         struct dmi_entry_attr_show_data data = {
 218                 .attr = attr,
 219                 .buf  = buf,
 220         };
 221         /* Find the entry according to our parent and call the
 222          * normalized show method hanging off of the attribute */
 223         return find_dmi_entry(to_entry(kobj->parent),
 224                               dmi_entry_attr_show_helper, &data);
 225 }
 226
 227 static const struct sysfs_ops dmi_sysfs_specialize_attr_ops = {
 228         .show = dmi_entry_attr_show,
 229 };
 230
 231 /*************************************************
 232  * Specialized DMI entry support.
 233  *************************************************/
 234
 235 /*** Type 15 - System Event Table ***/
 236
 237 #define DMI_SEL_ACCESS_METHOD_IO8       0x00
 238 #define DMI_SEL_ACCESS_METHOD_IO2x8     0x01
 239 #define DMI_SEL_ACCESS_METHOD_IO16      0x02
 240 #define DMI_SEL_ACCESS_METHOD_PHYS32    0x03
 241 #define DMI_SEL_ACCESS_METHOD_GPNV      0x04
 242
 243 struct dmi_system_event_log {
 244         struct dmi_header header;
 245         u16     area_length;
 246         u16     header_start_offset;
 247         u16     data_start_offset;
 248         u8      access_method;
 249         u8      status;
 250         u32     change_token;
 251         union {
 252                 struct {
 253                         u16 index_addr;
 254                         u16 data_addr;
 255                 } io;
 256                 u32     phys_addr32;
 257                 u16     gpnv_handle;
 258                 u32     access_method_address;
 259         };
 260         u8      header_format;
 261         u8      type_descriptors_supported_count;
 262         u8      per_log_type_descriptor_length;
 263         u8      supported_log_type_descriptos[0];
 264 } __packed;
 265
 266 static const struct dmi_system_event_log *to_sel(const struct dmi_header *dh)
 267 {
 268         return (const struct dmi_system_event_log *)dh;
 269 }
 270
 271 #define DMI_SYSFS_SEL_FIELD(_field) \
 272 static ssize_t dmi_sysfs_sel_##_field(struct dmi_sysfs_entry *entry, \
 273                                       const struct dmi_header *dh, \
 274                                       char *buf) \
 275 { \
 276         const struct dmi_system_event_log *sel = to_sel(dh); \
 277         if (sizeof(*sel) > dmi_entry_length(dh)) \
 278                 return -EIO; \
 279         return sprintf(buf, "%u\n", sel->_field); \
 280 } \
 281 static DMI_SYSFS_MAPPED_ATTR(sel, _field)
 282
 283 DMI_SYSFS_SEL_FIELD(area_length);
 284 DMI_SYSFS_SEL_FIELD(header_start_offset);
 285 DMI_SYSFS_SEL_FIELD(data_start_offset);
 286 DMI_SYSFS_SEL_FIELD(access_method);
 287 DMI_SYSFS_SEL_FIELD(status);
 288 DMI_SYSFS_SEL_FIELD(change_token);
 289 DMI_SYSFS_SEL_FIELD(access_method_address);
 290 DMI_SYSFS_SEL_FIELD(header_format);
 291 DMI_SYSFS_SEL_FIELD(type_descriptors_supported_count);
 292 DMI_SYSFS_SEL_FIELD(per_log_type_descriptor_length);
 293
 294 static struct attribute *dmi_sysfs_sel_attrs[] = {
 295         &dmi_sysfs_attr_sel_area_length.attr,
 296         &dmi_sysfs_attr_sel_header_start_offset.attr,
 297         &dmi_sysfs_attr_sel_data_start_offset.attr,
 298         &dmi_sysfs_attr_sel_access_method.attr,
 299         &dmi_sysfs_attr_sel_status.attr,
 300         &dmi_sysfs_attr_sel_change_token.attr,
 301         &dmi_sysfs_attr_sel_access_method_address.attr,
 302         &dmi_sysfs_attr_sel_header_format.attr,
 303         &dmi_sysfs_attr_sel_type_descriptors_supported_count.attr,
 304         &dmi_sysfs_attr_sel_per_log_type_descriptor_length.attr,
 305         NULL,
 306 };
 307
 308
 309 static struct kobj_type dmi_system_event_log_ktype = {
 310         .release = dmi_entry_free,
 311         .sysfs_ops = &dmi_sysfs_specialize_attr_ops,
 312         .default_attrs = dmi_sysfs_sel_attrs,
 313 };
 314
 315 static int dmi_system_event_log(struct dmi_sysfs_entry *entry)
 316 {
 317         int ret;
 318
 319         entry->child = kzalloc(sizeof(*entry->child), GFP_KERNEL);
 320         if (!entry->child)
 321                 return -ENOMEM;
 322         ret = kobject_init_and_add(entry->child,
 323                                    &dmi_system_event_log_ktype,
 324                                    &entry->kobj,
 325                                    "system_event_log");
 326         if (ret)
 327                 goto out_free;
 328 out_free:
 329         kfree(entry->child);
 330         return ret;
 331 }
 332
 333 /*************************************************
 334  * Generic DMI entry support.
 335  *************************************************/
 336
 337 static ssize_t dmi_sysfs_entry_length(struct dmi_sysfs_entry *entry, char *buf)
 338 {
 339         return sprintf(buf, "%d\n", entry->dh.length);
 340 }
 341
 342 static ssize_t dmi_sysfs_entry_handle(struct dmi_sysfs_entry *entry, char *buf)
 343 {
 344         return sprintf(buf, "%d\n", entry->dh.handle);
 345 }
 346
 347 static ssize_t dmi_sysfs_entry_type(struct dmi_sysfs_entry *entry, char *buf)
 348 {
 349         return sprintf(buf, "%d\n", entry->dh.type);
 350 }
 351
 352 static ssize_t dmi_sysfs_entry_instance(struct dmi_sysfs_entry *entry,
 353                                         char *buf)
 354 {
 355         return sprintf(buf, "%d\n", entry->instance);
 356 }
 357
 358 static ssize_t dmi_sysfs_entry_position(struct dmi_sysfs_entry *entry,
 359                                         char *buf)
 360 {
 361         return sprintf(buf, "%d\n", entry->position);
 362 }
 363
 364 static DMI_SYSFS_ATTR(entry, length);
 365 static DMI_SYSFS_ATTR(entry, handle);
 366 static DMI_SYSFS_ATTR(entry, type);
 367 static DMI_SYSFS_ATTR(entry, instance);
 368 static DMI_SYSFS_ATTR(entry, position);
 369
 370 static struct attribute *dmi_sysfs_entry_attrs[] = {
 371         &dmi_sysfs_attr_entry_length.attr,
 372         &dmi_sysfs_attr_entry_handle.attr,
 373         &dmi_sysfs_attr_entry_type.attr,
 374         &dmi_sysfs_attr_entry_instance.attr,
 375         &dmi_sysfs_attr_entry_position.attr,
 376         NULL,
 377 };
 378
 379 static ssize_t dmi_entry_raw_read_helper(struct dmi_sysfs_entry *entry,
 380                                          const struct dmi_header *dh,
 381                                          void *_state)
 382 {
 383         struct dmi_read_state *state = _state;
 384         size_t entry_length;
 385
 386         entry_length = dmi_entry_length(dh);
 387
 388         return memory_read_from_buffer(state->buf, state->count,
 389                                        &state->pos, dh, entry_length);
 390 }
 391
 392 static ssize_t dmi_entry_raw_read(struct file *filp,
 393                                   struct kobject *kobj,
 394                                   struct bin_attribute *bin_attr,
 395                                   char *buf, loff_t pos, size_t count)
 396 {
 397         struct dmi_sysfs_entry *entry = to_entry(kobj);
 398         struct dmi_read_state state = {
 399                 .buf = buf,
 400                 .pos = pos,
 401                 .count = count,
 402         };
 403
 404         return find_dmi_entry(entry, dmi_entry_raw_read_helper, &state);
 405 }
 406
 407 static const struct bin_attribute dmi_entry_raw_attr = {
 408         .attr = {.name = "raw", .mode = 0400},
 409         .read = dmi_entry_raw_read,
 410 };
 411
 412 static void dmi_sysfs_entry_release(struct kobject *kobj)
 413 {
 414         struct dmi_sysfs_entry *entry = to_entry(kobj);
 415         sysfs_remove_bin_file(&entry->kobj, &dmi_entry_raw_attr);
 416         spin_lock(&entry_list_lock);
 417         list_del(&entry->list);
 418         spin_unlock(&entry_list_lock);
 419         kfree(entry);
 420 }
 421
 422 static struct kobj_type dmi_sysfs_entry_ktype = {
 423         .release = dmi_sysfs_entry_release,
 424         .sysfs_ops = &dmi_sysfs_attr_ops,
 425         .default_attrs = dmi_sysfs_entry_attrs,
 426 };
 427
 428 static struct kobject *dmi_kobj;
 429 static struct kset *dmi_kset;
 430
 431 /* Global count of all instances seen.  Only for setup */
 432 static int __initdata instance_counts[MAX_ENTRY_TYPE + 1];
 433
 434 /* Global positional count of all entries seen.  Only for setup */
 435 static int __initdata position_count;
 436
 437 static void __init dmi_sysfs_register_handle(const struct dmi_header *dh,
 438                                              void *_ret)
 439 {
 440         struct dmi_sysfs_entry *entry;
 441         int *ret = _ret;
 442
 443         /* If a previous entry saw an error, short circuit */
 444         if (*ret)
 445                 return;
 446
 447         /* Allocate and register a new entry into the entries set */
 448         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 449         if (!entry) {
 450                 *ret = -ENOMEM;
 451                 return;
 452         }
 453
 454         /* Set the key */
 455         entry->dh = *dh;
 456         entry->instance = instance_counts[dh->type]++;
 457         entry->position = position_count++;
 458
 459         entry->kobj.kset = dmi_kset;
 460         *ret = kobject_init_and_add(&entry->kobj, &dmi_sysfs_entry_ktype, NULL,
 461                                     "%d-%d", dh->type, entry->instance);
 462
 463         if (*ret) {
 464                 kfree(entry);
 465                 return;
 466         }
 467
 468         /* Thread on the global list for cleanup */
 469         spin_lock(&entry_list_lock);
 470         list_add_tail(&entry->list, &entry_list);
 471         spin_unlock(&entry_list_lock);
 472
 473         /* Handle specializations by type */
 474         switch (dh->type) {
 475         case DMI_ENTRY_SYSTEM_EVENT_LOG:
 476                 *ret = dmi_system_event_log(entry);
 477                 break;
 478         default:
 479                 /* No specialization */
 480                 break;
 481         }
 482         if (*ret)
 483                 goto out_err;
 484
 485         /* Create the raw binary file to access the entry */
 486         *ret = sysfs_create_bin_file(&entry->kobj, &dmi_entry_raw_attr);
 487         if (*ret)
 488                 goto out_err;
 489
 490         return;
 491 out_err:
 492         kobject_put(entry->child);
 493         kobject_put(&entry->kobj);
 494         return;
 495 }
 496
 497 static void cleanup_entry_list(void)
 498 {
 499         struct dmi_sysfs_entry *entry, *next;
 500
 501         /* No locks, we are on our way out */
 502         list_for_each_entry_safe(entry, next, &entry_list, list) {
 503                 kobject_put(entry->child);
 504                 kobject_put(&entry->kobj);
 505         }
 506 }
 507
 508 static int __init dmi_sysfs_init(void)
 509 {
 510         int error = -ENOMEM;
 511         int val;
 512
 513         /* Set up our directory */
 514         dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
 515         if (!dmi_kobj)
 516                 goto err;
 517
 518         dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
 519         if (!dmi_kset)
 520                 goto err;
 521
 522         val = 0;
 523         error = dmi_walk(dmi_sysfs_register_handle, &val);
 524         if (error)
 525                 goto err;
 526         if (val) {
 527                 error = val;
 528                 goto err;
 529         }
 530
 531         pr_debug("dmi-sysfs: loaded.\n");
 532
 533         return 0;
 534 err:
 535         cleanup_entry_list();
 536         kset_unregister(dmi_kset);
 537         kobject_put(dmi_kobj);
 538         return error;
 539 }
 540
 541 /* clean up everything. */
 542 static void __exit dmi_sysfs_exit(void)
 543 {
 544         pr_debug("dmi-sysfs: unloading.\n");
 545         cleanup_entry_list();
 546         kset_unregister(dmi_kset);
 547         kobject_put(dmi_kobj);
 548 }
 549
 550 module_init(dmi_sysfs_init);
 551 module_exit(dmi_sysfs_exit);
 552
 553 MODULE_AUTHOR("Mike Waychison <mikew@google.com>");
 554 MODULE_DESCRIPTION("DMI sysfs support");
 555 MODULE_LICENSE("GPL");