linux/drivers/firmware/efi/vars.c
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   1/*
   2 * Originally from efivars.c
   3 *
   4 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
   5 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
   6 *
   7 *  This program is free software; you can redistribute it and/or modify
   8 *  it under the terms of the GNU General Public License as published by
   9 *  the Free Software Foundation; either version 2 of the License, or
  10 *  (at your option) any later version.
  11 *
  12 *  This program is distributed in the hope that it will be useful,
  13 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 *  GNU General Public License for more details.
  16 *
  17 *  You should have received a copy of the GNU General Public License
  18 *  along with this program; if not, write to the Free Software
  19 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20 */
  21
  22#include <linux/capability.h>
  23#include <linux/types.h>
  24#include <linux/errno.h>
  25#include <linux/init.h>
  26#include <linux/mm.h>
  27#include <linux/module.h>
  28#include <linux/string.h>
  29#include <linux/smp.h>
  30#include <linux/efi.h>
  31#include <linux/sysfs.h>
  32#include <linux/device.h>
  33#include <linux/slab.h>
  34#include <linux/ctype.h>
  35#include <linux/ucs2_string.h>
  36
  37/* Private pointer to registered efivars */
  38static struct efivars *__efivars;
  39
  40static bool efivar_wq_enabled = true;
  41DECLARE_WORK(efivar_work, NULL);
  42EXPORT_SYMBOL_GPL(efivar_work);
  43
  44static bool
  45validate_device_path(struct efi_variable *var, int match, u8 *buffer,
  46                     unsigned long len)
  47{
  48        struct efi_generic_dev_path *node;
  49        int offset = 0;
  50
  51        node = (struct efi_generic_dev_path *)buffer;
  52
  53        if (len < sizeof(*node))
  54                return false;
  55
  56        while (offset <= len - sizeof(*node) &&
  57               node->length >= sizeof(*node) &&
  58                node->length <= len - offset) {
  59                offset += node->length;
  60
  61                if ((node->type == EFI_DEV_END_PATH ||
  62                     node->type == EFI_DEV_END_PATH2) &&
  63                    node->sub_type == EFI_DEV_END_ENTIRE)
  64                        return true;
  65
  66                node = (struct efi_generic_dev_path *)(buffer + offset);
  67        }
  68
  69        /*
  70         * If we're here then either node->length pointed past the end
  71         * of the buffer or we reached the end of the buffer without
  72         * finding a device path end node.
  73         */
  74        return false;
  75}
  76
  77static bool
  78validate_boot_order(struct efi_variable *var, int match, u8 *buffer,
  79                    unsigned long len)
  80{
  81        /* An array of 16-bit integers */
  82        if ((len % 2) != 0)
  83                return false;
  84
  85        return true;
  86}
  87
  88static bool
  89validate_load_option(struct efi_variable *var, int match, u8 *buffer,
  90                     unsigned long len)
  91{
  92        u16 filepathlength;
  93        int i, desclength = 0, namelen;
  94
  95        namelen = ucs2_strnlen(var->VariableName, sizeof(var->VariableName));
  96
  97        /* Either "Boot" or "Driver" followed by four digits of hex */
  98        for (i = match; i < match+4; i++) {
  99                if (var->VariableName[i] > 127 ||
 100                    hex_to_bin(var->VariableName[i] & 0xff) < 0)
 101                        return true;
 102        }
 103
 104        /* Reject it if there's 4 digits of hex and then further content */
 105        if (namelen > match + 4)
 106                return false;
 107
 108        /* A valid entry must be at least 8 bytes */
 109        if (len < 8)
 110                return false;
 111
 112        filepathlength = buffer[4] | buffer[5] << 8;
 113
 114        /*
 115         * There's no stored length for the description, so it has to be
 116         * found by hand
 117         */
 118        desclength = ucs2_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;
 119
 120        /* Each boot entry must have a descriptor */
 121        if (!desclength)
 122                return false;
 123
 124        /*
 125         * If the sum of the length of the description, the claimed filepath
 126         * length and the original header are greater than the length of the
 127         * variable, it's malformed
 128         */
 129        if ((desclength + filepathlength + 6) > len)
 130                return false;
 131
 132        /*
 133         * And, finally, check the filepath
 134         */
 135        return validate_device_path(var, match, buffer + desclength + 6,
 136                                    filepathlength);
 137}
 138
 139static bool
 140validate_uint16(struct efi_variable *var, int match, u8 *buffer,
 141                unsigned long len)
 142{
 143        /* A single 16-bit integer */
 144        if (len != 2)
 145                return false;
 146
 147        return true;
 148}
 149
 150static bool
 151validate_ascii_string(struct efi_variable *var, int match, u8 *buffer,
 152                      unsigned long len)
 153{
 154        int i;
 155
 156        for (i = 0; i < len; i++) {
 157                if (buffer[i] > 127)
 158                        return false;
 159
 160                if (buffer[i] == 0)
 161                        return true;
 162        }
 163
 164        return false;
 165}
 166
 167struct variable_validate {
 168        char *name;
 169        bool (*validate)(struct efi_variable *var, int match, u8 *data,
 170                         unsigned long len);
 171};
 172
 173static const struct variable_validate variable_validate[] = {
 174        { "BootNext", validate_uint16 },
 175        { "BootOrder", validate_boot_order },
 176        { "DriverOrder", validate_boot_order },
 177        { "Boot*", validate_load_option },
 178        { "Driver*", validate_load_option },
 179        { "ConIn", validate_device_path },
 180        { "ConInDev", validate_device_path },
 181        { "ConOut", validate_device_path },
 182        { "ConOutDev", validate_device_path },
 183        { "ErrOut", validate_device_path },
 184        { "ErrOutDev", validate_device_path },
 185        { "Timeout", validate_uint16 },
 186        { "Lang", validate_ascii_string },
 187        { "PlatformLang", validate_ascii_string },
 188        { "", NULL },
 189};
 190
 191bool
 192efivar_validate(struct efi_variable *var, u8 *data, unsigned long len)
 193{
 194        int i;
 195        u16 *unicode_name = var->VariableName;
 196
 197        for (i = 0; variable_validate[i].validate != NULL; i++) {
 198                const char *name = variable_validate[i].name;
 199                int match;
 200
 201                for (match = 0; ; match++) {
 202                        char c = name[match];
 203                        u16 u = unicode_name[match];
 204
 205                        /* All special variables are plain ascii */
 206                        if (u > 127)
 207                                return true;
 208
 209                        /* Wildcard in the matching name means we've matched */
 210                        if (c == '*')
 211                                return variable_validate[i].validate(var,
 212                                                             match, data, len);
 213
 214                        /* Case sensitive match */
 215                        if (c != u)
 216                                break;
 217
 218                        /* Reached the end of the string while matching */
 219                        if (!c)
 220                                return variable_validate[i].validate(var,
 221                                                             match, data, len);
 222                }
 223        }
 224
 225        return true;
 226}
 227EXPORT_SYMBOL_GPL(efivar_validate);
 228
 229static efi_status_t
 230check_var_size(u32 attributes, unsigned long size)
 231{
 232        const struct efivar_operations *fops = __efivars->ops;
 233
 234        if (!fops->query_variable_store)
 235                return EFI_UNSUPPORTED;
 236
 237        return fops->query_variable_store(attributes, size);
 238}
 239
 240static int efi_status_to_err(efi_status_t status)
 241{
 242        int err;
 243
 244        switch (status) {
 245        case EFI_SUCCESS:
 246                err = 0;
 247                break;
 248        case EFI_INVALID_PARAMETER:
 249                err = -EINVAL;
 250                break;
 251        case EFI_OUT_OF_RESOURCES:
 252                err = -ENOSPC;
 253                break;
 254        case EFI_DEVICE_ERROR:
 255                err = -EIO;
 256                break;
 257        case EFI_WRITE_PROTECTED:
 258                err = -EROFS;
 259                break;
 260        case EFI_SECURITY_VIOLATION:
 261                err = -EACCES;
 262                break;
 263        case EFI_NOT_FOUND:
 264                err = -ENOENT;
 265                break;
 266        default:
 267                err = -EINVAL;
 268        }
 269
 270        return err;
 271}
 272
 273static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor,
 274                                struct list_head *head)
 275{
 276        struct efivar_entry *entry, *n;
 277        unsigned long strsize1, strsize2;
 278        bool found = false;
 279
 280        strsize1 = ucs2_strsize(variable_name, 1024);
 281        list_for_each_entry_safe(entry, n, head, list) {
 282                strsize2 = ucs2_strsize(entry->var.VariableName, 1024);
 283                if (strsize1 == strsize2 &&
 284                        !memcmp(variable_name, &(entry->var.VariableName),
 285                                strsize2) &&
 286                        !efi_guidcmp(entry->var.VendorGuid,
 287                                *vendor)) {
 288                        found = true;
 289                        break;
 290                }
 291        }
 292        return found;
 293}
 294
 295/*
 296 * Returns the size of variable_name, in bytes, including the
 297 * terminating NULL character, or variable_name_size if no NULL
 298 * character is found among the first variable_name_size bytes.
 299 */
 300static unsigned long var_name_strnsize(efi_char16_t *variable_name,
 301                                       unsigned long variable_name_size)
 302{
 303        unsigned long len;
 304        efi_char16_t c;
 305
 306        /*
 307         * The variable name is, by definition, a NULL-terminated
 308         * string, so make absolutely sure that variable_name_size is
 309         * the value we expect it to be. If not, return the real size.
 310         */
 311        for (len = 2; len <= variable_name_size; len += sizeof(c)) {
 312                c = variable_name[(len / sizeof(c)) - 1];
 313                if (!c)
 314                        break;
 315        }
 316
 317        return min(len, variable_name_size);
 318}
 319
 320/*
 321 * Print a warning when duplicate EFI variables are encountered and
 322 * disable the sysfs workqueue since the firmware is buggy.
 323 */
 324static void dup_variable_bug(efi_char16_t *s16, efi_guid_t *vendor_guid,
 325                             unsigned long len16)
 326{
 327        size_t i, len8 = len16 / sizeof(efi_char16_t);
 328        char *s8;
 329
 330        /*
 331         * Disable the workqueue since the algorithm it uses for
 332         * detecting new variables won't work with this buggy
 333         * implementation of GetNextVariableName().
 334         */
 335        efivar_wq_enabled = false;
 336
 337        s8 = kzalloc(len8, GFP_KERNEL);
 338        if (!s8)
 339                return;
 340
 341        for (i = 0; i < len8; i++)
 342                s8[i] = s16[i];
 343
 344        printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
 345               s8, vendor_guid);
 346        kfree(s8);
 347}
 348
 349/**
 350 * efivar_init - build the initial list of EFI variables
 351 * @func: callback function to invoke for every variable
 352 * @data: function-specific data to pass to @func
 353 * @atomic: do we need to execute the @func-loop atomically?
 354 * @duplicates: error if we encounter duplicates on @head?
 355 * @head: initialised head of variable list
 356 *
 357 * Get every EFI variable from the firmware and invoke @func. @func
 358 * should call efivar_entry_add() to build the list of variables.
 359 *
 360 * Returns 0 on success, or a kernel error code on failure.
 361 */
 362int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 363                void *data, bool atomic, bool duplicates,
 364                struct list_head *head)
 365{
 366        const struct efivar_operations *ops = __efivars->ops;
 367        unsigned long variable_name_size = 1024;
 368        efi_char16_t *variable_name;
 369        efi_status_t status;
 370        efi_guid_t vendor_guid;
 371        int err = 0;
 372
 373        variable_name = kzalloc(variable_name_size, GFP_KERNEL);
 374        if (!variable_name) {
 375                printk(KERN_ERR "efivars: Memory allocation failed.\n");
 376                return -ENOMEM;
 377        }
 378
 379        spin_lock_irq(&__efivars->lock);
 380
 381        /*
 382         * Per EFI spec, the maximum storage allocated for both
 383         * the variable name and variable data is 1024 bytes.
 384         */
 385
 386        do {
 387                variable_name_size = 1024;
 388
 389                status = ops->get_next_variable(&variable_name_size,
 390                                                variable_name,
 391                                                &vendor_guid);
 392                switch (status) {
 393                case EFI_SUCCESS:
 394                        if (!atomic)
 395                                spin_unlock_irq(&__efivars->lock);
 396
 397                        variable_name_size = var_name_strnsize(variable_name,
 398                                                               variable_name_size);
 399
 400                        /*
 401                         * Some firmware implementations return the
 402                         * same variable name on multiple calls to
 403                         * get_next_variable(). Terminate the loop
 404                         * immediately as there is no guarantee that
 405                         * we'll ever see a different variable name,
 406                         * and may end up looping here forever.
 407                         */
 408                        if (duplicates &&
 409                            variable_is_present(variable_name, &vendor_guid, head)) {
 410                                dup_variable_bug(variable_name, &vendor_guid,
 411                                                 variable_name_size);
 412                                if (!atomic)
 413                                        spin_lock_irq(&__efivars->lock);
 414
 415                                status = EFI_NOT_FOUND;
 416                                break;
 417                        }
 418
 419                        err = func(variable_name, vendor_guid, variable_name_size, data);
 420                        if (err)
 421                                status = EFI_NOT_FOUND;
 422
 423                        if (!atomic)
 424                                spin_lock_irq(&__efivars->lock);
 425
 426                        break;
 427                case EFI_NOT_FOUND:
 428                        break;
 429                default:
 430                        printk(KERN_WARNING "efivars: get_next_variable: status=%lx\n",
 431                                status);
 432                        status = EFI_NOT_FOUND;
 433                        break;
 434                }
 435
 436        } while (status != EFI_NOT_FOUND);
 437
 438        spin_unlock_irq(&__efivars->lock);
 439
 440        kfree(variable_name);
 441
 442        return err;
 443}
 444EXPORT_SYMBOL_GPL(efivar_init);
 445
 446/**
 447 * efivar_entry_add - add entry to variable list
 448 * @entry: entry to add to list
 449 * @head: list head
 450 */
 451void efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
 452{
 453        spin_lock_irq(&__efivars->lock);
 454        list_add(&entry->list, head);
 455        spin_unlock_irq(&__efivars->lock);
 456}
 457EXPORT_SYMBOL_GPL(efivar_entry_add);
 458
 459/**
 460 * efivar_entry_remove - remove entry from variable list
 461 * @entry: entry to remove from list
 462 */
 463void efivar_entry_remove(struct efivar_entry *entry)
 464{
 465        spin_lock_irq(&__efivars->lock);
 466        list_del(&entry->list);
 467        spin_unlock_irq(&__efivars->lock);
 468}
 469EXPORT_SYMBOL_GPL(efivar_entry_remove);
 470
 471/*
 472 * efivar_entry_list_del_unlock - remove entry from variable list
 473 * @entry: entry to remove
 474 *
 475 * Remove @entry from the variable list and release the list lock.
 476 *
 477 * NOTE: slightly weird locking semantics here - we expect to be
 478 * called with the efivars lock already held, and we release it before
 479 * returning. This is because this function is usually called after
 480 * set_variable() while the lock is still held.
 481 */
 482static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
 483{
 484        WARN_ON(!spin_is_locked(&__efivars->lock));
 485
 486        list_del(&entry->list);
 487        spin_unlock_irq(&__efivars->lock);
 488}
 489
 490/**
 491 * __efivar_entry_delete - delete an EFI variable
 492 * @entry: entry containing EFI variable to delete
 493 *
 494 * Delete the variable from the firmware but leave @entry on the
 495 * variable list.
 496 *
 497 * This function differs from efivar_entry_delete() because it does
 498 * not remove @entry from the variable list. Also, it is safe to be
 499 * called from within a efivar_entry_iter_begin() and
 500 * efivar_entry_iter_end() region, unlike efivar_entry_delete().
 501 *
 502 * Returns 0 on success, or a converted EFI status code if
 503 * set_variable() fails.
 504 */
 505int __efivar_entry_delete(struct efivar_entry *entry)
 506{
 507        const struct efivar_operations *ops = __efivars->ops;
 508        efi_status_t status;
 509
 510        WARN_ON(!spin_is_locked(&__efivars->lock));
 511
 512        status = ops->set_variable(entry->var.VariableName,
 513                                   &entry->var.VendorGuid,
 514                                   0, 0, NULL);
 515
 516        return efi_status_to_err(status);
 517}
 518EXPORT_SYMBOL_GPL(__efivar_entry_delete);
 519
 520/**
 521 * efivar_entry_delete - delete variable and remove entry from list
 522 * @entry: entry containing variable to delete
 523 *
 524 * Delete the variable from the firmware and remove @entry from the
 525 * variable list. It is the caller's responsibility to free @entry
 526 * once we return.
 527 *
 528 * Returns 0 on success, or a converted EFI status code if
 529 * set_variable() fails.
 530 */
 531int efivar_entry_delete(struct efivar_entry *entry)
 532{
 533        const struct efivar_operations *ops = __efivars->ops;
 534        efi_status_t status;
 535
 536        spin_lock_irq(&__efivars->lock);
 537        status = ops->set_variable(entry->var.VariableName,
 538                                   &entry->var.VendorGuid,
 539                                   0, 0, NULL);
 540        if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
 541                spin_unlock_irq(&__efivars->lock);
 542                return efi_status_to_err(status);
 543        }
 544
 545        efivar_entry_list_del_unlock(entry);
 546        return 0;
 547}
 548EXPORT_SYMBOL_GPL(efivar_entry_delete);
 549
 550/**
 551 * efivar_entry_set - call set_variable()
 552 * @entry: entry containing the EFI variable to write
 553 * @attributes: variable attributes
 554 * @size: size of @data buffer
 555 * @data: buffer containing variable data
 556 * @head: head of variable list
 557 *
 558 * Calls set_variable() for an EFI variable. If creating a new EFI
 559 * variable, this function is usually followed by efivar_entry_add().
 560 *
 561 * Before writing the variable, the remaining EFI variable storage
 562 * space is checked to ensure there is enough room available.
 563 *
 564 * If @head is not NULL a lookup is performed to determine whether
 565 * the entry is already on the list.
 566 *
 567 * Returns 0 on success, -EEXIST if a lookup is performed and the entry
 568 * already exists on the list, or a converted EFI status code if
 569 * set_variable() fails.
 570 */
 571int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
 572                     unsigned long size, void *data, struct list_head *head)
 573{
 574        const struct efivar_operations *ops = __efivars->ops;
 575        efi_status_t status;
 576        efi_char16_t *name = entry->var.VariableName;
 577        efi_guid_t vendor = entry->var.VendorGuid;
 578
 579        spin_lock_irq(&__efivars->lock);
 580
 581        if (head && efivar_entry_find(name, vendor, head, false)) {
 582                spin_unlock_irq(&__efivars->lock);
 583                return -EEXIST;
 584        }
 585
 586        status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
 587        if (status == EFI_SUCCESS || status == EFI_UNSUPPORTED)
 588                status = ops->set_variable(name, &vendor,
 589                                           attributes, size, data);
 590
 591        spin_unlock_irq(&__efivars->lock);
 592
 593        return efi_status_to_err(status);
 594
 595}
 596EXPORT_SYMBOL_GPL(efivar_entry_set);
 597
 598/**
 599 * efivar_entry_set_safe - call set_variable() if enough space in firmware
 600 * @name: buffer containing the variable name
 601 * @vendor: variable vendor guid
 602 * @attributes: variable attributes
 603 * @block: can we block in this context?
 604 * @size: size of @data buffer
 605 * @data: buffer containing variable data
 606 *
 607 * Ensures there is enough free storage in the firmware for this variable, and
 608 * if so, calls set_variable(). If creating a new EFI variable, this function
 609 * is usually followed by efivar_entry_add().
 610 *
 611 * Returns 0 on success, -ENOSPC if the firmware does not have enough
 612 * space for set_variable() to succeed, or a converted EFI status code
 613 * if set_variable() fails.
 614 */
 615int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
 616                          bool block, unsigned long size, void *data)
 617{
 618        const struct efivar_operations *ops = __efivars->ops;
 619        unsigned long flags;
 620        efi_status_t status;
 621
 622        if (!ops->query_variable_store)
 623                return -ENOSYS;
 624
 625        if (!block) {
 626                if (!spin_trylock_irqsave(&__efivars->lock, flags))
 627                        return -EBUSY;
 628        } else {
 629                spin_lock_irqsave(&__efivars->lock, flags);
 630        }
 631
 632        status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
 633        if (status != EFI_SUCCESS) {
 634                spin_unlock_irqrestore(&__efivars->lock, flags);
 635                return -ENOSPC;
 636        }
 637
 638        status = ops->set_variable(name, &vendor, attributes, size, data);
 639
 640        spin_unlock_irqrestore(&__efivars->lock, flags);
 641
 642        return efi_status_to_err(status);
 643}
 644EXPORT_SYMBOL_GPL(efivar_entry_set_safe);
 645
 646/**
 647 * efivar_entry_find - search for an entry
 648 * @name: the EFI variable name
 649 * @guid: the EFI variable vendor's guid
 650 * @head: head of the variable list
 651 * @remove: should we remove the entry from the list?
 652 *
 653 * Search for an entry on the variable list that has the EFI variable
 654 * name @name and vendor guid @guid. If an entry is found on the list
 655 * and @remove is true, the entry is removed from the list.
 656 *
 657 * The caller MUST call efivar_entry_iter_begin() and
 658 * efivar_entry_iter_end() before and after the invocation of this
 659 * function, respectively.
 660 *
 661 * Returns the entry if found on the list, %NULL otherwise.
 662 */
 663struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
 664                                       struct list_head *head, bool remove)
 665{
 666        struct efivar_entry *entry, *n;
 667        int strsize1, strsize2;
 668        bool found = false;
 669
 670        WARN_ON(!spin_is_locked(&__efivars->lock));
 671
 672        list_for_each_entry_safe(entry, n, head, list) {
 673                strsize1 = ucs2_strsize(name, 1024);
 674                strsize2 = ucs2_strsize(entry->var.VariableName, 1024);
 675                if (strsize1 == strsize2 &&
 676                    !memcmp(name, &(entry->var.VariableName), strsize1) &&
 677                    !efi_guidcmp(guid, entry->var.VendorGuid)) {
 678                        found = true;
 679                        break;
 680                }
 681        }
 682
 683        if (!found)
 684                return NULL;
 685
 686        if (remove) {
 687                if (entry->scanning) {
 688                        /*
 689                         * The entry will be deleted
 690                         * after scanning is completed.
 691                         */
 692                        entry->deleting = true;
 693                } else
 694                        list_del(&entry->list);
 695        }
 696
 697        return entry;
 698}
 699EXPORT_SYMBOL_GPL(efivar_entry_find);
 700
 701/**
 702 * efivar_entry_size - obtain the size of a variable
 703 * @entry: entry for this variable
 704 * @size: location to store the variable's size
 705 */
 706int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
 707{
 708        const struct efivar_operations *ops = __efivars->ops;
 709        efi_status_t status;
 710
 711        *size = 0;
 712
 713        spin_lock_irq(&__efivars->lock);
 714        status = ops->get_variable(entry->var.VariableName,
 715                                   &entry->var.VendorGuid, NULL, size, NULL);
 716        spin_unlock_irq(&__efivars->lock);
 717
 718        if (status != EFI_BUFFER_TOO_SMALL)
 719                return efi_status_to_err(status);
 720
 721        return 0;
 722}
 723EXPORT_SYMBOL_GPL(efivar_entry_size);
 724
 725/**
 726 * __efivar_entry_get - call get_variable()
 727 * @entry: read data for this variable
 728 * @attributes: variable attributes
 729 * @size: size of @data buffer
 730 * @data: buffer to store variable data
 731 *
 732 * The caller MUST call efivar_entry_iter_begin() and
 733 * efivar_entry_iter_end() before and after the invocation of this
 734 * function, respectively.
 735 */
 736int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 737                       unsigned long *size, void *data)
 738{
 739        const struct efivar_operations *ops = __efivars->ops;
 740        efi_status_t status;
 741
 742        WARN_ON(!spin_is_locked(&__efivars->lock));
 743
 744        status = ops->get_variable(entry->var.VariableName,
 745                                   &entry->var.VendorGuid,
 746                                   attributes, size, data);
 747
 748        return efi_status_to_err(status);
 749}
 750EXPORT_SYMBOL_GPL(__efivar_entry_get);
 751
 752/**
 753 * efivar_entry_get - call get_variable()
 754 * @entry: read data for this variable
 755 * @attributes: variable attributes
 756 * @size: size of @data buffer
 757 * @data: buffer to store variable data
 758 */
 759int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 760                     unsigned long *size, void *data)
 761{
 762        const struct efivar_operations *ops = __efivars->ops;
 763        efi_status_t status;
 764
 765        spin_lock_irq(&__efivars->lock);
 766        status = ops->get_variable(entry->var.VariableName,
 767                                   &entry->var.VendorGuid,
 768                                   attributes, size, data);
 769        spin_unlock_irq(&__efivars->lock);
 770
 771        return efi_status_to_err(status);
 772}
 773EXPORT_SYMBOL_GPL(efivar_entry_get);
 774
 775/**
 776 * efivar_entry_set_get_size - call set_variable() and get new size (atomic)
 777 * @entry: entry containing variable to set and get
 778 * @attributes: attributes of variable to be written
 779 * @size: size of data buffer
 780 * @data: buffer containing data to write
 781 * @set: did the set_variable() call succeed?
 782 *
 783 * This is a pretty special (complex) function. See efivarfs_file_write().
 784 *
 785 * Atomically call set_variable() for @entry and if the call is
 786 * successful, return the new size of the variable from get_variable()
 787 * in @size. The success of set_variable() is indicated by @set.
 788 *
 789 * Returns 0 on success, -EINVAL if the variable data is invalid,
 790 * -ENOSPC if the firmware does not have enough available space, or a
 791 * converted EFI status code if either of set_variable() or
 792 * get_variable() fail.
 793 *
 794 * If the EFI variable does not exist when calling set_variable()
 795 * (EFI_NOT_FOUND), @entry is removed from the variable list.
 796 */
 797int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 798                              unsigned long *size, void *data, bool *set)
 799{
 800        const struct efivar_operations *ops = __efivars->ops;
 801        efi_char16_t *name = entry->var.VariableName;
 802        efi_guid_t *vendor = &entry->var.VendorGuid;
 803        efi_status_t status;
 804        int err;
 805
 806        *set = false;
 807
 808        if (efivar_validate(&entry->var, data, *size) == false)
 809                return -EINVAL;
 810
 811        /*
 812         * The lock here protects the get_variable call, the conditional
 813         * set_variable call, and removal of the variable from the efivars
 814         * list (in the case of an authenticated delete).
 815         */
 816        spin_lock_irq(&__efivars->lock);
 817
 818        /*
 819         * Ensure that the available space hasn't shrunk below the safe level
 820         */
 821        status = check_var_size(attributes, *size + ucs2_strsize(name, 1024));
 822        if (status != EFI_SUCCESS) {
 823                if (status != EFI_UNSUPPORTED) {
 824                        err = efi_status_to_err(status);
 825                        goto out;
 826                }
 827
 828                if (*size > 65536) {
 829                        err = -ENOSPC;
 830                        goto out;
 831                }
 832        }
 833
 834        status = ops->set_variable(name, vendor, attributes, *size, data);
 835        if (status != EFI_SUCCESS) {
 836                err = efi_status_to_err(status);
 837                goto out;
 838        }
 839
 840        *set = true;
 841
 842        /*
 843         * Writing to the variable may have caused a change in size (which
 844         * could either be an append or an overwrite), or the variable to be
 845         * deleted. Perform a GetVariable() so we can tell what actually
 846         * happened.
 847         */
 848        *size = 0;
 849        status = ops->get_variable(entry->var.VariableName,
 850                                   &entry->var.VendorGuid,
 851                                   NULL, size, NULL);
 852
 853        if (status == EFI_NOT_FOUND)
 854                efivar_entry_list_del_unlock(entry);
 855        else
 856                spin_unlock_irq(&__efivars->lock);
 857
 858        if (status && status != EFI_BUFFER_TOO_SMALL)
 859                return efi_status_to_err(status);
 860
 861        return 0;
 862
 863out:
 864        spin_unlock_irq(&__efivars->lock);
 865        return err;
 866
 867}
 868EXPORT_SYMBOL_GPL(efivar_entry_set_get_size);
 869
 870/**
 871 * efivar_entry_iter_begin - begin iterating the variable list
 872 *
 873 * Lock the variable list to prevent entry insertion and removal until
 874 * efivar_entry_iter_end() is called. This function is usually used in
 875 * conjunction with __efivar_entry_iter() or efivar_entry_iter().
 876 */
 877void efivar_entry_iter_begin(void)
 878{
 879        spin_lock_irq(&__efivars->lock);
 880}
 881EXPORT_SYMBOL_GPL(efivar_entry_iter_begin);
 882
 883/**
 884 * efivar_entry_iter_end - finish iterating the variable list
 885 *
 886 * Unlock the variable list and allow modifications to the list again.
 887 */
 888void efivar_entry_iter_end(void)
 889{
 890        spin_unlock_irq(&__efivars->lock);
 891}
 892EXPORT_SYMBOL_GPL(efivar_entry_iter_end);
 893
 894/**
 895 * __efivar_entry_iter - iterate over variable list
 896 * @func: callback function
 897 * @head: head of the variable list
 898 * @data: function-specific data to pass to callback
 899 * @prev: entry to begin iterating from
 900 *
 901 * Iterate over the list of EFI variables and call @func with every
 902 * entry on the list. It is safe for @func to remove entries in the
 903 * list via efivar_entry_delete().
 904 *
 905 * You MUST call efivar_enter_iter_begin() before this function, and
 906 * efivar_entry_iter_end() afterwards.
 907 *
 908 * It is possible to begin iteration from an arbitrary entry within
 909 * the list by passing @prev. @prev is updated on return to point to
 910 * the last entry passed to @func. To begin iterating from the
 911 * beginning of the list @prev must be %NULL.
 912 *
 913 * The restrictions for @func are the same as documented for
 914 * efivar_entry_iter().
 915 */
 916int __efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
 917                        struct list_head *head, void *data,
 918                        struct efivar_entry **prev)
 919{
 920        struct efivar_entry *entry, *n;
 921        int err = 0;
 922
 923        if (!prev || !*prev) {
 924                list_for_each_entry_safe(entry, n, head, list) {
 925                        err = func(entry, data);
 926                        if (err)
 927                                break;
 928                }
 929
 930                if (prev)
 931                        *prev = entry;
 932
 933                return err;
 934        }
 935
 936
 937        list_for_each_entry_safe_continue((*prev), n, head, list) {
 938                err = func(*prev, data);
 939                if (err)
 940                        break;
 941        }
 942
 943        return err;
 944}
 945EXPORT_SYMBOL_GPL(__efivar_entry_iter);
 946
 947/**
 948 * efivar_entry_iter - iterate over variable list
 949 * @func: callback function
 950 * @head: head of variable list
 951 * @data: function-specific data to pass to callback
 952 *
 953 * Iterate over the list of EFI variables and call @func with every
 954 * entry on the list. It is safe for @func to remove entries in the
 955 * list via efivar_entry_delete() while iterating.
 956 *
 957 * Some notes for the callback function:
 958 *  - a non-zero return value indicates an error and terminates the loop
 959 *  - @func is called from atomic context
 960 */
 961int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
 962                      struct list_head *head, void *data)
 963{
 964        int err = 0;
 965
 966        efivar_entry_iter_begin();
 967        err = __efivar_entry_iter(func, head, data, NULL);
 968        efivar_entry_iter_end();
 969
 970        return err;
 971}
 972EXPORT_SYMBOL_GPL(efivar_entry_iter);
 973
 974/**
 975 * efivars_kobject - get the kobject for the registered efivars
 976 *
 977 * If efivars_register() has not been called we return NULL,
 978 * otherwise return the kobject used at registration time.
 979 */
 980struct kobject *efivars_kobject(void)
 981{
 982        if (!__efivars)
 983                return NULL;
 984
 985        return __efivars->kobject;
 986}
 987EXPORT_SYMBOL_GPL(efivars_kobject);
 988
 989/**
 990 * efivar_run_worker - schedule the efivar worker thread
 991 */
 992void efivar_run_worker(void)
 993{
 994        if (efivar_wq_enabled)
 995                schedule_work(&efivar_work);
 996}
 997EXPORT_SYMBOL_GPL(efivar_run_worker);
 998
 999/**
1000 * efivars_register - register an efivars
1001 * @efivars: efivars to register
1002 * @ops: efivars operations
1003 * @kobject: @efivars-specific kobject
1004 *
1005 * Only a single efivars can be registered at any time.
1006 */
1007int efivars_register(struct efivars *efivars,
1008                     const struct efivar_operations *ops,
1009                     struct kobject *kobject)
1010{
1011        spin_lock_init(&efivars->lock);
1012        efivars->ops = ops;
1013        efivars->kobject = kobject;
1014
1015        __efivars = efivars;
1016
1017        return 0;
1018}
1019EXPORT_SYMBOL_GPL(efivars_register);
1020
1021/**
1022 * efivars_unregister - unregister an efivars
1023 * @efivars: efivars to unregister
1024 *
1025 * The caller must have already removed every entry from the list,
1026 * failure to do so is an error.
1027 */
1028int efivars_unregister(struct efivars *efivars)
1029{
1030        int rv;
1031
1032        if (!__efivars) {
1033                printk(KERN_ERR "efivars not registered\n");
1034                rv = -EINVAL;
1035                goto out;
1036        }
1037
1038        if (__efivars != efivars) {
1039                rv = -EINVAL;
1040                goto out;
1041        }
1042
1043        __efivars = NULL;
1044
1045        rv = 0;
1046out:
1047        return rv;
1048}
1049EXPORT_SYMBOL_GPL(efivars_unregister);
1050