xref: /linux/drivers/firmware/efi/vars.c (revision bbcd53c960713507ae764bf81970651b5577b95a)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Originally from efivars.c
4  *
5  * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
6  * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
7  */
8 
9 #include <linux/capability.h>
10 #include <linux/types.h>
11 #include <linux/errno.h>
12 #include <linux/init.h>
13 #include <linux/mm.h>
14 #include <linux/module.h>
15 #include <linux/string.h>
16 #include <linux/smp.h>
17 #include <linux/efi.h>
18 #include <linux/sysfs.h>
19 #include <linux/device.h>
20 #include <linux/slab.h>
21 #include <linux/ctype.h>
22 #include <linux/ucs2_string.h>
23 
24 /* Private pointer to registered efivars */
25 static struct efivars *__efivars;
26 
27 /*
28  * efivars_lock protects three things:
29  * 1) efivarfs_list and efivars_sysfs_list
30  * 2) ->ops calls
31  * 3) (un)registration of __efivars
32  */
33 static DEFINE_SEMAPHORE(efivars_lock);
34 
35 static bool
36 validate_device_path(efi_char16_t *var_name, int match, u8 *buffer,
37 		     unsigned long len)
38 {
39 	struct efi_generic_dev_path *node;
40 	int offset = 0;
41 
42 	node = (struct efi_generic_dev_path *)buffer;
43 
44 	if (len < sizeof(*node))
45 		return false;
46 
47 	while (offset <= len - sizeof(*node) &&
48 	       node->length >= sizeof(*node) &&
49 		node->length <= len - offset) {
50 		offset += node->length;
51 
52 		if ((node->type == EFI_DEV_END_PATH ||
53 		     node->type == EFI_DEV_END_PATH2) &&
54 		    node->sub_type == EFI_DEV_END_ENTIRE)
55 			return true;
56 
57 		node = (struct efi_generic_dev_path *)(buffer + offset);
58 	}
59 
60 	/*
61 	 * If we're here then either node->length pointed past the end
62 	 * of the buffer or we reached the end of the buffer without
63 	 * finding a device path end node.
64 	 */
65 	return false;
66 }
67 
68 static bool
69 validate_boot_order(efi_char16_t *var_name, int match, u8 *buffer,
70 		    unsigned long len)
71 {
72 	/* An array of 16-bit integers */
73 	if ((len % 2) != 0)
74 		return false;
75 
76 	return true;
77 }
78 
79 static bool
80 validate_load_option(efi_char16_t *var_name, int match, u8 *buffer,
81 		     unsigned long len)
82 {
83 	u16 filepathlength;
84 	int i, desclength = 0, namelen;
85 
86 	namelen = ucs2_strnlen(var_name, EFI_VAR_NAME_LEN);
87 
88 	/* Either "Boot" or "Driver" followed by four digits of hex */
89 	for (i = match; i < match+4; i++) {
90 		if (var_name[i] > 127 ||
91 		    hex_to_bin(var_name[i] & 0xff) < 0)
92 			return true;
93 	}
94 
95 	/* Reject it if there's 4 digits of hex and then further content */
96 	if (namelen > match + 4)
97 		return false;
98 
99 	/* A valid entry must be at least 8 bytes */
100 	if (len < 8)
101 		return false;
102 
103 	filepathlength = buffer[4] | buffer[5] << 8;
104 
105 	/*
106 	 * There's no stored length for the description, so it has to be
107 	 * found by hand
108 	 */
109 	desclength = ucs2_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;
110 
111 	/* Each boot entry must have a descriptor */
112 	if (!desclength)
113 		return false;
114 
115 	/*
116 	 * If the sum of the length of the description, the claimed filepath
117 	 * length and the original header are greater than the length of the
118 	 * variable, it's malformed
119 	 */
120 	if ((desclength + filepathlength + 6) > len)
121 		return false;
122 
123 	/*
124 	 * And, finally, check the filepath
125 	 */
126 	return validate_device_path(var_name, match, buffer + desclength + 6,
127 				    filepathlength);
128 }
129 
130 static bool
131 validate_uint16(efi_char16_t *var_name, int match, u8 *buffer,
132 		unsigned long len)
133 {
134 	/* A single 16-bit integer */
135 	if (len != 2)
136 		return false;
137 
138 	return true;
139 }
140 
141 static bool
142 validate_ascii_string(efi_char16_t *var_name, int match, u8 *buffer,
143 		      unsigned long len)
144 {
145 	int i;
146 
147 	for (i = 0; i < len; i++) {
148 		if (buffer[i] > 127)
149 			return false;
150 
151 		if (buffer[i] == 0)
152 			return true;
153 	}
154 
155 	return false;
156 }
157 
158 struct variable_validate {
159 	efi_guid_t vendor;
160 	char *name;
161 	bool (*validate)(efi_char16_t *var_name, int match, u8 *data,
162 			 unsigned long len);
163 };
164 
165 /*
166  * This is the list of variables we need to validate, as well as the
167  * whitelist for what we think is safe not to default to immutable.
168  *
169  * If it has a validate() method that's not NULL, it'll go into the
170  * validation routine.  If not, it is assumed valid, but still used for
171  * whitelisting.
172  *
173  * Note that it's sorted by {vendor,name}, but globbed names must come after
174  * any other name with the same prefix.
175  */
176 static const struct variable_validate variable_validate[] = {
177 	{ EFI_GLOBAL_VARIABLE_GUID, "BootNext", validate_uint16 },
178 	{ EFI_GLOBAL_VARIABLE_GUID, "BootOrder", validate_boot_order },
179 	{ EFI_GLOBAL_VARIABLE_GUID, "Boot*", validate_load_option },
180 	{ EFI_GLOBAL_VARIABLE_GUID, "DriverOrder", validate_boot_order },
181 	{ EFI_GLOBAL_VARIABLE_GUID, "Driver*", validate_load_option },
182 	{ EFI_GLOBAL_VARIABLE_GUID, "ConIn", validate_device_path },
183 	{ EFI_GLOBAL_VARIABLE_GUID, "ConInDev", validate_device_path },
184 	{ EFI_GLOBAL_VARIABLE_GUID, "ConOut", validate_device_path },
185 	{ EFI_GLOBAL_VARIABLE_GUID, "ConOutDev", validate_device_path },
186 	{ EFI_GLOBAL_VARIABLE_GUID, "ErrOut", validate_device_path },
187 	{ EFI_GLOBAL_VARIABLE_GUID, "ErrOutDev", validate_device_path },
188 	{ EFI_GLOBAL_VARIABLE_GUID, "Lang", validate_ascii_string },
189 	{ EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
190 	{ EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
191 	{ EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
192 	{ LINUX_EFI_CRASH_GUID, "*", NULL },
193 	{ NULL_GUID, "", NULL },
194 };
195 
196 /*
197  * Check if @var_name matches the pattern given in @match_name.
198  *
199  * @var_name: an array of @len non-NUL characters.
200  * @match_name: a NUL-terminated pattern string, optionally ending in "*". A
201  *              final "*" character matches any trailing characters @var_name,
202  *              including the case when there are none left in @var_name.
203  * @match: on output, the number of non-wildcard characters in @match_name
204  *         that @var_name matches, regardless of the return value.
205  * @return: whether @var_name fully matches @match_name.
206  */
207 static bool
208 variable_matches(const char *var_name, size_t len, const char *match_name,
209 		 int *match)
210 {
211 	for (*match = 0; ; (*match)++) {
212 		char c = match_name[*match];
213 
214 		switch (c) {
215 		case '*':
216 			/* Wildcard in @match_name means we've matched. */
217 			return true;
218 
219 		case '\0':
220 			/* @match_name has ended. Has @var_name too? */
221 			return (*match == len);
222 
223 		default:
224 			/*
225 			 * We've reached a non-wildcard char in @match_name.
226 			 * Continue only if there's an identical character in
227 			 * @var_name.
228 			 */
229 			if (*match < len && c == var_name[*match])
230 				continue;
231 			return false;
232 		}
233 	}
234 }
235 
236 bool
237 efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
238 		unsigned long data_size)
239 {
240 	int i;
241 	unsigned long utf8_size;
242 	u8 *utf8_name;
243 
244 	utf8_size = ucs2_utf8size(var_name);
245 	utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
246 	if (!utf8_name)
247 		return false;
248 
249 	ucs2_as_utf8(utf8_name, var_name, utf8_size);
250 	utf8_name[utf8_size] = '\0';
251 
252 	for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
253 		const char *name = variable_validate[i].name;
254 		int match = 0;
255 
256 		if (efi_guidcmp(vendor, variable_validate[i].vendor))
257 			continue;
258 
259 		if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
260 			if (variable_validate[i].validate == NULL)
261 				break;
262 			kfree(utf8_name);
263 			return variable_validate[i].validate(var_name, match,
264 							     data, data_size);
265 		}
266 	}
267 	kfree(utf8_name);
268 	return true;
269 }
270 EXPORT_SYMBOL_GPL(efivar_validate);
271 
272 bool
273 efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
274 			     size_t len)
275 {
276 	int i;
277 	bool found = false;
278 	int match = 0;
279 
280 	/*
281 	 * Check if our variable is in the validated variables list
282 	 */
283 	for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
284 		if (efi_guidcmp(variable_validate[i].vendor, vendor))
285 			continue;
286 
287 		if (variable_matches(var_name, len,
288 				     variable_validate[i].name, &match)) {
289 			found = true;
290 			break;
291 		}
292 	}
293 
294 	/*
295 	 * If it's in our list, it is removable.
296 	 */
297 	return found;
298 }
299 EXPORT_SYMBOL_GPL(efivar_variable_is_removable);
300 
301 static efi_status_t
302 check_var_size(u32 attributes, unsigned long size)
303 {
304 	const struct efivar_operations *fops;
305 
306 	if (!__efivars)
307 		return EFI_UNSUPPORTED;
308 
309 	fops = __efivars->ops;
310 
311 	if (!fops->query_variable_store)
312 		return EFI_UNSUPPORTED;
313 
314 	return fops->query_variable_store(attributes, size, false);
315 }
316 
317 static efi_status_t
318 check_var_size_nonblocking(u32 attributes, unsigned long size)
319 {
320 	const struct efivar_operations *fops;
321 
322 	if (!__efivars)
323 		return EFI_UNSUPPORTED;
324 
325 	fops = __efivars->ops;
326 
327 	if (!fops->query_variable_store)
328 		return EFI_UNSUPPORTED;
329 
330 	return fops->query_variable_store(attributes, size, true);
331 }
332 
333 static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor,
334 				struct list_head *head)
335 {
336 	struct efivar_entry *entry, *n;
337 	unsigned long strsize1, strsize2;
338 	bool found = false;
339 
340 	strsize1 = ucs2_strsize(variable_name, 1024);
341 	list_for_each_entry_safe(entry, n, head, list) {
342 		strsize2 = ucs2_strsize(entry->var.VariableName, 1024);
343 		if (strsize1 == strsize2 &&
344 			!memcmp(variable_name, &(entry->var.VariableName),
345 				strsize2) &&
346 			!efi_guidcmp(entry->var.VendorGuid,
347 				*vendor)) {
348 			found = true;
349 			break;
350 		}
351 	}
352 	return found;
353 }
354 
355 /*
356  * Returns the size of variable_name, in bytes, including the
357  * terminating NULL character, or variable_name_size if no NULL
358  * character is found among the first variable_name_size bytes.
359  */
360 static unsigned long var_name_strnsize(efi_char16_t *variable_name,
361 				       unsigned long variable_name_size)
362 {
363 	unsigned long len;
364 	efi_char16_t c;
365 
366 	/*
367 	 * The variable name is, by definition, a NULL-terminated
368 	 * string, so make absolutely sure that variable_name_size is
369 	 * the value we expect it to be. If not, return the real size.
370 	 */
371 	for (len = 2; len <= variable_name_size; len += sizeof(c)) {
372 		c = variable_name[(len / sizeof(c)) - 1];
373 		if (!c)
374 			break;
375 	}
376 
377 	return min(len, variable_name_size);
378 }
379 
380 /*
381  * Print a warning when duplicate EFI variables are encountered and
382  * disable the sysfs workqueue since the firmware is buggy.
383  */
384 static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
385 			     unsigned long len16)
386 {
387 	size_t i, len8 = len16 / sizeof(efi_char16_t);
388 	char *str8;
389 
390 	str8 = kzalloc(len8, GFP_KERNEL);
391 	if (!str8)
392 		return;
393 
394 	for (i = 0; i < len8; i++)
395 		str8[i] = str16[i];
396 
397 	printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
398 	       str8, vendor_guid);
399 	kfree(str8);
400 }
401 
402 /**
403  * efivar_init - build the initial list of EFI variables
404  * @func: callback function to invoke for every variable
405  * @data: function-specific data to pass to @func
406  * @duplicates: error if we encounter duplicates on @head?
407  * @head: initialised head of variable list
408  *
409  * Get every EFI variable from the firmware and invoke @func. @func
410  * should call efivar_entry_add() to build the list of variables.
411  *
412  * Returns 0 on success, or a kernel error code on failure.
413  */
414 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
415 		void *data, bool duplicates, struct list_head *head)
416 {
417 	const struct efivar_operations *ops;
418 	unsigned long variable_name_size = 1024;
419 	efi_char16_t *variable_name;
420 	efi_status_t status;
421 	efi_guid_t vendor_guid;
422 	int err = 0;
423 
424 	if (!__efivars)
425 		return -EFAULT;
426 
427 	ops = __efivars->ops;
428 
429 	variable_name = kzalloc(variable_name_size, GFP_KERNEL);
430 	if (!variable_name) {
431 		printk(KERN_ERR "efivars: Memory allocation failed.\n");
432 		return -ENOMEM;
433 	}
434 
435 	if (down_interruptible(&efivars_lock)) {
436 		err = -EINTR;
437 		goto free;
438 	}
439 
440 	/*
441 	 * Per EFI spec, the maximum storage allocated for both
442 	 * the variable name and variable data is 1024 bytes.
443 	 */
444 
445 	do {
446 		variable_name_size = 1024;
447 
448 		status = ops->get_next_variable(&variable_name_size,
449 						variable_name,
450 						&vendor_guid);
451 		switch (status) {
452 		case EFI_SUCCESS:
453 			if (duplicates)
454 				up(&efivars_lock);
455 
456 			variable_name_size = var_name_strnsize(variable_name,
457 							       variable_name_size);
458 
459 			/*
460 			 * Some firmware implementations return the
461 			 * same variable name on multiple calls to
462 			 * get_next_variable(). Terminate the loop
463 			 * immediately as there is no guarantee that
464 			 * we'll ever see a different variable name,
465 			 * and may end up looping here forever.
466 			 */
467 			if (duplicates &&
468 			    variable_is_present(variable_name, &vendor_guid,
469 						head)) {
470 				dup_variable_bug(variable_name, &vendor_guid,
471 						 variable_name_size);
472 				status = EFI_NOT_FOUND;
473 			} else {
474 				err = func(variable_name, vendor_guid,
475 					   variable_name_size, data);
476 				if (err)
477 					status = EFI_NOT_FOUND;
478 			}
479 
480 			if (duplicates) {
481 				if (down_interruptible(&efivars_lock)) {
482 					err = -EINTR;
483 					goto free;
484 				}
485 			}
486 
487 			break;
488 		case EFI_UNSUPPORTED:
489 			err = -EOPNOTSUPP;
490 			status = EFI_NOT_FOUND;
491 			break;
492 		case EFI_NOT_FOUND:
493 			break;
494 		default:
495 			printk(KERN_WARNING "efivars: get_next_variable: status=%lx\n",
496 				status);
497 			status = EFI_NOT_FOUND;
498 			break;
499 		}
500 
501 	} while (status != EFI_NOT_FOUND);
502 
503 	up(&efivars_lock);
504 free:
505 	kfree(variable_name);
506 
507 	return err;
508 }
509 EXPORT_SYMBOL_GPL(efivar_init);
510 
511 /**
512  * efivar_entry_add - add entry to variable list
513  * @entry: entry to add to list
514  * @head: list head
515  *
516  * Returns 0 on success, or a kernel error code on failure.
517  */
518 int efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
519 {
520 	if (down_interruptible(&efivars_lock))
521 		return -EINTR;
522 	list_add(&entry->list, head);
523 	up(&efivars_lock);
524 
525 	return 0;
526 }
527 EXPORT_SYMBOL_GPL(efivar_entry_add);
528 
529 /**
530  * efivar_entry_remove - remove entry from variable list
531  * @entry: entry to remove from list
532  *
533  * Returns 0 on success, or a kernel error code on failure.
534  */
535 int efivar_entry_remove(struct efivar_entry *entry)
536 {
537 	if (down_interruptible(&efivars_lock))
538 		return -EINTR;
539 	list_del(&entry->list);
540 	up(&efivars_lock);
541 
542 	return 0;
543 }
544 EXPORT_SYMBOL_GPL(efivar_entry_remove);
545 
546 /*
547  * efivar_entry_list_del_unlock - remove entry from variable list
548  * @entry: entry to remove
549  *
550  * Remove @entry from the variable list and release the list lock.
551  *
552  * NOTE: slightly weird locking semantics here - we expect to be
553  * called with the efivars lock already held, and we release it before
554  * returning. This is because this function is usually called after
555  * set_variable() while the lock is still held.
556  */
557 static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
558 {
559 	list_del(&entry->list);
560 	up(&efivars_lock);
561 }
562 
563 /**
564  * __efivar_entry_delete - delete an EFI variable
565  * @entry: entry containing EFI variable to delete
566  *
567  * Delete the variable from the firmware but leave @entry on the
568  * variable list.
569  *
570  * This function differs from efivar_entry_delete() because it does
571  * not remove @entry from the variable list. Also, it is safe to be
572  * called from within a efivar_entry_iter_begin() and
573  * efivar_entry_iter_end() region, unlike efivar_entry_delete().
574  *
575  * Returns 0 on success, or a converted EFI status code if
576  * set_variable() fails.
577  */
578 int __efivar_entry_delete(struct efivar_entry *entry)
579 {
580 	efi_status_t status;
581 
582 	if (!__efivars)
583 		return -EINVAL;
584 
585 	status = __efivars->ops->set_variable(entry->var.VariableName,
586 					      &entry->var.VendorGuid,
587 					      0, 0, NULL);
588 
589 	return efi_status_to_err(status);
590 }
591 EXPORT_SYMBOL_GPL(__efivar_entry_delete);
592 
593 /**
594  * efivar_entry_delete - delete variable and remove entry from list
595  * @entry: entry containing variable to delete
596  *
597  * Delete the variable from the firmware and remove @entry from the
598  * variable list. It is the caller's responsibility to free @entry
599  * once we return.
600  *
601  * Returns 0 on success, -EINTR if we can't grab the semaphore,
602  * converted EFI status code if set_variable() fails.
603  */
604 int efivar_entry_delete(struct efivar_entry *entry)
605 {
606 	const struct efivar_operations *ops;
607 	efi_status_t status;
608 
609 	if (down_interruptible(&efivars_lock))
610 		return -EINTR;
611 
612 	if (!__efivars) {
613 		up(&efivars_lock);
614 		return -EINVAL;
615 	}
616 	ops = __efivars->ops;
617 	status = ops->set_variable(entry->var.VariableName,
618 				   &entry->var.VendorGuid,
619 				   0, 0, NULL);
620 	if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
621 		up(&efivars_lock);
622 		return efi_status_to_err(status);
623 	}
624 
625 	efivar_entry_list_del_unlock(entry);
626 	return 0;
627 }
628 EXPORT_SYMBOL_GPL(efivar_entry_delete);
629 
630 /**
631  * efivar_entry_set - call set_variable()
632  * @entry: entry containing the EFI variable to write
633  * @attributes: variable attributes
634  * @size: size of @data buffer
635  * @data: buffer containing variable data
636  * @head: head of variable list
637  *
638  * Calls set_variable() for an EFI variable. If creating a new EFI
639  * variable, this function is usually followed by efivar_entry_add().
640  *
641  * Before writing the variable, the remaining EFI variable storage
642  * space is checked to ensure there is enough room available.
643  *
644  * If @head is not NULL a lookup is performed to determine whether
645  * the entry is already on the list.
646  *
647  * Returns 0 on success, -EINTR if we can't grab the semaphore,
648  * -EEXIST if a lookup is performed and the entry already exists on
649  * the list, or a converted EFI status code if set_variable() fails.
650  */
651 int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
652 		     unsigned long size, void *data, struct list_head *head)
653 {
654 	const struct efivar_operations *ops;
655 	efi_status_t status;
656 	efi_char16_t *name = entry->var.VariableName;
657 	efi_guid_t vendor = entry->var.VendorGuid;
658 
659 	if (down_interruptible(&efivars_lock))
660 		return -EINTR;
661 
662 	if (!__efivars) {
663 		up(&efivars_lock);
664 		return -EINVAL;
665 	}
666 	ops = __efivars->ops;
667 	if (head && efivar_entry_find(name, vendor, head, false)) {
668 		up(&efivars_lock);
669 		return -EEXIST;
670 	}
671 
672 	status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
673 	if (status == EFI_SUCCESS || status == EFI_UNSUPPORTED)
674 		status = ops->set_variable(name, &vendor,
675 					   attributes, size, data);
676 
677 	up(&efivars_lock);
678 
679 	return efi_status_to_err(status);
680 
681 }
682 EXPORT_SYMBOL_GPL(efivar_entry_set);
683 
684 /*
685  * efivar_entry_set_nonblocking - call set_variable_nonblocking()
686  *
687  * This function is guaranteed to not block and is suitable for calling
688  * from crash/panic handlers.
689  *
690  * Crucially, this function will not block if it cannot acquire
691  * efivars_lock. Instead, it returns -EBUSY.
692  */
693 static int
694 efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
695 			     u32 attributes, unsigned long size, void *data)
696 {
697 	const struct efivar_operations *ops;
698 	efi_status_t status;
699 
700 	if (down_trylock(&efivars_lock))
701 		return -EBUSY;
702 
703 	if (!__efivars) {
704 		up(&efivars_lock);
705 		return -EINVAL;
706 	}
707 
708 	status = check_var_size_nonblocking(attributes,
709 					    size + ucs2_strsize(name, 1024));
710 	if (status != EFI_SUCCESS) {
711 		up(&efivars_lock);
712 		return -ENOSPC;
713 	}
714 
715 	ops = __efivars->ops;
716 	status = ops->set_variable_nonblocking(name, &vendor, attributes,
717 					       size, data);
718 
719 	up(&efivars_lock);
720 	return efi_status_to_err(status);
721 }
722 
723 /**
724  * efivar_entry_set_safe - call set_variable() if enough space in firmware
725  * @name: buffer containing the variable name
726  * @vendor: variable vendor guid
727  * @attributes: variable attributes
728  * @block: can we block in this context?
729  * @size: size of @data buffer
730  * @data: buffer containing variable data
731  *
732  * Ensures there is enough free storage in the firmware for this variable, and
733  * if so, calls set_variable(). If creating a new EFI variable, this function
734  * is usually followed by efivar_entry_add().
735  *
736  * Returns 0 on success, -ENOSPC if the firmware does not have enough
737  * space for set_variable() to succeed, or a converted EFI status code
738  * if set_variable() fails.
739  */
740 int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
741 			  bool block, unsigned long size, void *data)
742 {
743 	const struct efivar_operations *ops;
744 	efi_status_t status;
745 
746 	if (!__efivars)
747 		return -EINVAL;
748 
749 	ops = __efivars->ops;
750 	if (!ops->query_variable_store)
751 		return -ENOSYS;
752 
753 	/*
754 	 * If the EFI variable backend provides a non-blocking
755 	 * ->set_variable() operation and we're in a context where we
756 	 * cannot block, then we need to use it to avoid live-locks,
757 	 * since the implication is that the regular ->set_variable()
758 	 * will block.
759 	 *
760 	 * If no ->set_variable_nonblocking() is provided then
761 	 * ->set_variable() is assumed to be non-blocking.
762 	 */
763 	if (!block && ops->set_variable_nonblocking)
764 		return efivar_entry_set_nonblocking(name, vendor, attributes,
765 						    size, data);
766 
767 	if (!block) {
768 		if (down_trylock(&efivars_lock))
769 			return -EBUSY;
770 	} else {
771 		if (down_interruptible(&efivars_lock))
772 			return -EINTR;
773 	}
774 
775 	status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
776 	if (status != EFI_SUCCESS) {
777 		up(&efivars_lock);
778 		return -ENOSPC;
779 	}
780 
781 	status = ops->set_variable(name, &vendor, attributes, size, data);
782 
783 	up(&efivars_lock);
784 
785 	return efi_status_to_err(status);
786 }
787 EXPORT_SYMBOL_GPL(efivar_entry_set_safe);
788 
789 /**
790  * efivar_entry_find - search for an entry
791  * @name: the EFI variable name
792  * @guid: the EFI variable vendor's guid
793  * @head: head of the variable list
794  * @remove: should we remove the entry from the list?
795  *
796  * Search for an entry on the variable list that has the EFI variable
797  * name @name and vendor guid @guid. If an entry is found on the list
798  * and @remove is true, the entry is removed from the list.
799  *
800  * The caller MUST call efivar_entry_iter_begin() and
801  * efivar_entry_iter_end() before and after the invocation of this
802  * function, respectively.
803  *
804  * Returns the entry if found on the list, %NULL otherwise.
805  */
806 struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
807 				       struct list_head *head, bool remove)
808 {
809 	struct efivar_entry *entry, *n;
810 	int strsize1, strsize2;
811 	bool found = false;
812 
813 	list_for_each_entry_safe(entry, n, head, list) {
814 		strsize1 = ucs2_strsize(name, 1024);
815 		strsize2 = ucs2_strsize(entry->var.VariableName, 1024);
816 		if (strsize1 == strsize2 &&
817 		    !memcmp(name, &(entry->var.VariableName), strsize1) &&
818 		    !efi_guidcmp(guid, entry->var.VendorGuid)) {
819 			found = true;
820 			break;
821 		}
822 	}
823 
824 	if (!found)
825 		return NULL;
826 
827 	if (remove) {
828 		if (entry->scanning) {
829 			/*
830 			 * The entry will be deleted
831 			 * after scanning is completed.
832 			 */
833 			entry->deleting = true;
834 		} else
835 			list_del(&entry->list);
836 	}
837 
838 	return entry;
839 }
840 EXPORT_SYMBOL_GPL(efivar_entry_find);
841 
842 /**
843  * efivar_entry_size - obtain the size of a variable
844  * @entry: entry for this variable
845  * @size: location to store the variable's size
846  */
847 int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
848 {
849 	const struct efivar_operations *ops;
850 	efi_status_t status;
851 
852 	*size = 0;
853 
854 	if (down_interruptible(&efivars_lock))
855 		return -EINTR;
856 	if (!__efivars) {
857 		up(&efivars_lock);
858 		return -EINVAL;
859 	}
860 	ops = __efivars->ops;
861 	status = ops->get_variable(entry->var.VariableName,
862 				   &entry->var.VendorGuid, NULL, size, NULL);
863 	up(&efivars_lock);
864 
865 	if (status != EFI_BUFFER_TOO_SMALL)
866 		return efi_status_to_err(status);
867 
868 	return 0;
869 }
870 EXPORT_SYMBOL_GPL(efivar_entry_size);
871 
872 /**
873  * __efivar_entry_get - call get_variable()
874  * @entry: read data for this variable
875  * @attributes: variable attributes
876  * @size: size of @data buffer
877  * @data: buffer to store variable data
878  *
879  * The caller MUST call efivar_entry_iter_begin() and
880  * efivar_entry_iter_end() before and after the invocation of this
881  * function, respectively.
882  */
883 int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
884 		       unsigned long *size, void *data)
885 {
886 	efi_status_t status;
887 
888 	if (!__efivars)
889 		return -EINVAL;
890 
891 	status = __efivars->ops->get_variable(entry->var.VariableName,
892 					      &entry->var.VendorGuid,
893 					      attributes, size, data);
894 
895 	return efi_status_to_err(status);
896 }
897 EXPORT_SYMBOL_GPL(__efivar_entry_get);
898 
899 /**
900  * efivar_entry_get - call get_variable()
901  * @entry: read data for this variable
902  * @attributes: variable attributes
903  * @size: size of @data buffer
904  * @data: buffer to store variable data
905  */
906 int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
907 		     unsigned long *size, void *data)
908 {
909 	efi_status_t status;
910 
911 	if (down_interruptible(&efivars_lock))
912 		return -EINTR;
913 
914 	if (!__efivars) {
915 		up(&efivars_lock);
916 		return -EINVAL;
917 	}
918 
919 	status = __efivars->ops->get_variable(entry->var.VariableName,
920 					      &entry->var.VendorGuid,
921 					      attributes, size, data);
922 	up(&efivars_lock);
923 
924 	return efi_status_to_err(status);
925 }
926 EXPORT_SYMBOL_GPL(efivar_entry_get);
927 
928 /**
929  * efivar_entry_set_get_size - call set_variable() and get new size (atomic)
930  * @entry: entry containing variable to set and get
931  * @attributes: attributes of variable to be written
932  * @size: size of data buffer
933  * @data: buffer containing data to write
934  * @set: did the set_variable() call succeed?
935  *
936  * This is a pretty special (complex) function. See efivarfs_file_write().
937  *
938  * Atomically call set_variable() for @entry and if the call is
939  * successful, return the new size of the variable from get_variable()
940  * in @size. The success of set_variable() is indicated by @set.
941  *
942  * Returns 0 on success, -EINVAL if the variable data is invalid,
943  * -ENOSPC if the firmware does not have enough available space, or a
944  * converted EFI status code if either of set_variable() or
945  * get_variable() fail.
946  *
947  * If the EFI variable does not exist when calling set_variable()
948  * (EFI_NOT_FOUND), @entry is removed from the variable list.
949  */
950 int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
951 			      unsigned long *size, void *data, bool *set)
952 {
953 	const struct efivar_operations *ops;
954 	efi_char16_t *name = entry->var.VariableName;
955 	efi_guid_t *vendor = &entry->var.VendorGuid;
956 	efi_status_t status;
957 	int err;
958 
959 	*set = false;
960 
961 	if (efivar_validate(*vendor, name, data, *size) == false)
962 		return -EINVAL;
963 
964 	/*
965 	 * The lock here protects the get_variable call, the conditional
966 	 * set_variable call, and removal of the variable from the efivars
967 	 * list (in the case of an authenticated delete).
968 	 */
969 	if (down_interruptible(&efivars_lock))
970 		return -EINTR;
971 
972 	if (!__efivars) {
973 		err = -EINVAL;
974 		goto out;
975 	}
976 
977 	/*
978 	 * Ensure that the available space hasn't shrunk below the safe level
979 	 */
980 	status = check_var_size(attributes, *size + ucs2_strsize(name, 1024));
981 	if (status != EFI_SUCCESS) {
982 		if (status != EFI_UNSUPPORTED) {
983 			err = efi_status_to_err(status);
984 			goto out;
985 		}
986 
987 		if (*size > 65536) {
988 			err = -ENOSPC;
989 			goto out;
990 		}
991 	}
992 
993 	ops = __efivars->ops;
994 
995 	status = ops->set_variable(name, vendor, attributes, *size, data);
996 	if (status != EFI_SUCCESS) {
997 		err = efi_status_to_err(status);
998 		goto out;
999 	}
1000 
1001 	*set = true;
1002 
1003 	/*
1004 	 * Writing to the variable may have caused a change in size (which
1005 	 * could either be an append or an overwrite), or the variable to be
1006 	 * deleted. Perform a GetVariable() so we can tell what actually
1007 	 * happened.
1008 	 */
1009 	*size = 0;
1010 	status = ops->get_variable(entry->var.VariableName,
1011 				   &entry->var.VendorGuid,
1012 				   NULL, size, NULL);
1013 
1014 	if (status == EFI_NOT_FOUND)
1015 		efivar_entry_list_del_unlock(entry);
1016 	else
1017 		up(&efivars_lock);
1018 
1019 	if (status && status != EFI_BUFFER_TOO_SMALL)
1020 		return efi_status_to_err(status);
1021 
1022 	return 0;
1023 
1024 out:
1025 	up(&efivars_lock);
1026 	return err;
1027 
1028 }
1029 EXPORT_SYMBOL_GPL(efivar_entry_set_get_size);
1030 
1031 /**
1032  * efivar_entry_iter_begin - begin iterating the variable list
1033  *
1034  * Lock the variable list to prevent entry insertion and removal until
1035  * efivar_entry_iter_end() is called. This function is usually used in
1036  * conjunction with __efivar_entry_iter() or efivar_entry_iter().
1037  */
1038 int efivar_entry_iter_begin(void)
1039 {
1040 	return down_interruptible(&efivars_lock);
1041 }
1042 EXPORT_SYMBOL_GPL(efivar_entry_iter_begin);
1043 
1044 /**
1045  * efivar_entry_iter_end - finish iterating the variable list
1046  *
1047  * Unlock the variable list and allow modifications to the list again.
1048  */
1049 void efivar_entry_iter_end(void)
1050 {
1051 	up(&efivars_lock);
1052 }
1053 EXPORT_SYMBOL_GPL(efivar_entry_iter_end);
1054 
1055 /**
1056  * __efivar_entry_iter - iterate over variable list
1057  * @func: callback function
1058  * @head: head of the variable list
1059  * @data: function-specific data to pass to callback
1060  * @prev: entry to begin iterating from
1061  *
1062  * Iterate over the list of EFI variables and call @func with every
1063  * entry on the list. It is safe for @func to remove entries in the
1064  * list via efivar_entry_delete().
1065  *
1066  * You MUST call efivar_entry_iter_begin() before this function, and
1067  * efivar_entry_iter_end() afterwards.
1068  *
1069  * It is possible to begin iteration from an arbitrary entry within
1070  * the list by passing @prev. @prev is updated on return to point to
1071  * the last entry passed to @func. To begin iterating from the
1072  * beginning of the list @prev must be %NULL.
1073  *
1074  * The restrictions for @func are the same as documented for
1075  * efivar_entry_iter().
1076  */
1077 int __efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
1078 			struct list_head *head, void *data,
1079 			struct efivar_entry **prev)
1080 {
1081 	struct efivar_entry *entry, *n;
1082 	int err = 0;
1083 
1084 	if (!prev || !*prev) {
1085 		list_for_each_entry_safe(entry, n, head, list) {
1086 			err = func(entry, data);
1087 			if (err)
1088 				break;
1089 		}
1090 
1091 		if (prev)
1092 			*prev = entry;
1093 
1094 		return err;
1095 	}
1096 
1097 
1098 	list_for_each_entry_safe_continue((*prev), n, head, list) {
1099 		err = func(*prev, data);
1100 		if (err)
1101 			break;
1102 	}
1103 
1104 	return err;
1105 }
1106 EXPORT_SYMBOL_GPL(__efivar_entry_iter);
1107 
1108 /**
1109  * efivar_entry_iter - iterate over variable list
1110  * @func: callback function
1111  * @head: head of variable list
1112  * @data: function-specific data to pass to callback
1113  *
1114  * Iterate over the list of EFI variables and call @func with every
1115  * entry on the list. It is safe for @func to remove entries in the
1116  * list via efivar_entry_delete() while iterating.
1117  *
1118  * Some notes for the callback function:
1119  *  - a non-zero return value indicates an error and terminates the loop
1120  *  - @func is called from atomic context
1121  */
1122 int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
1123 		      struct list_head *head, void *data)
1124 {
1125 	int err = 0;
1126 
1127 	err = efivar_entry_iter_begin();
1128 	if (err)
1129 		return err;
1130 	err = __efivar_entry_iter(func, head, data, NULL);
1131 	efivar_entry_iter_end();
1132 
1133 	return err;
1134 }
1135 EXPORT_SYMBOL_GPL(efivar_entry_iter);
1136 
1137 /**
1138  * efivars_kobject - get the kobject for the registered efivars
1139  *
1140  * If efivars_register() has not been called we return NULL,
1141  * otherwise return the kobject used at registration time.
1142  */
1143 struct kobject *efivars_kobject(void)
1144 {
1145 	if (!__efivars)
1146 		return NULL;
1147 
1148 	return __efivars->kobject;
1149 }
1150 EXPORT_SYMBOL_GPL(efivars_kobject);
1151 
1152 /**
1153  * efivars_register - register an efivars
1154  * @efivars: efivars to register
1155  * @ops: efivars operations
1156  * @kobject: @efivars-specific kobject
1157  *
1158  * Only a single efivars can be registered at any time.
1159  */
1160 int efivars_register(struct efivars *efivars,
1161 		     const struct efivar_operations *ops,
1162 		     struct kobject *kobject)
1163 {
1164 	if (down_interruptible(&efivars_lock))
1165 		return -EINTR;
1166 
1167 	efivars->ops = ops;
1168 	efivars->kobject = kobject;
1169 
1170 	__efivars = efivars;
1171 
1172 	pr_info("Registered efivars operations\n");
1173 
1174 	up(&efivars_lock);
1175 
1176 	return 0;
1177 }
1178 EXPORT_SYMBOL_GPL(efivars_register);
1179 
1180 /**
1181  * efivars_unregister - unregister an efivars
1182  * @efivars: efivars to unregister
1183  *
1184  * The caller must have already removed every entry from the list,
1185  * failure to do so is an error.
1186  */
1187 int efivars_unregister(struct efivars *efivars)
1188 {
1189 	int rv;
1190 
1191 	if (down_interruptible(&efivars_lock))
1192 		return -EINTR;
1193 
1194 	if (!__efivars) {
1195 		printk(KERN_ERR "efivars not registered\n");
1196 		rv = -EINVAL;
1197 		goto out;
1198 	}
1199 
1200 	if (__efivars != efivars) {
1201 		rv = -EINVAL;
1202 		goto out;
1203 	}
1204 
1205 	pr_info("Unregistered efivars operations\n");
1206 	__efivars = NULL;
1207 
1208 	rv = 0;
1209 out:
1210 	up(&efivars_lock);
1211 	return rv;
1212 }
1213 EXPORT_SYMBOL_GPL(efivars_unregister);
1214 
1215 int efivar_supports_writes(void)
1216 {
1217 	return __efivars && __efivars->ops->set_variable;
1218 }
1219 EXPORT_SYMBOL_GPL(efivar_supports_writes);
1220