1 /*
2  * Helper functions used by the EFI stub on multiple
3  * architectures. This should be #included by the EFI stub
4  * implementation files.
5  *
6  * Copyright 2011 Intel Corporation; author Matt Fleming
7  *
8  * This file is part of the Linux kernel, and is made available
9  * under the terms of the GNU General Public License version 2.
10  *
11  */
12 
13 #include <linux/efi.h>
14 #include <asm/efi.h>
15 
16 #include "efistub.h"
17 
18 /*
19  * Some firmware implementations have problems reading files in one go.
20  * A read chunk size of 1MB seems to work for most platforms.
21  *
22  * Unfortunately, reading files in chunks triggers *other* bugs on some
23  * platforms, so we provide a way to disable this workaround, which can
24  * be done by passing "efi=nochunk" on the EFI boot stub command line.
25  *
26  * If you experience issues with initrd images being corrupt it's worth
27  * trying efi=nochunk, but chunking is enabled by default because there
28  * are far more machines that require the workaround than those that
29  * break with it enabled.
30  */
31 #define EFI_READ_CHUNK_SIZE	(1024 * 1024)
32 
33 static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
34 
35 #define EFI_MMAP_NR_SLACK_SLOTS	8
36 
37 struct file_info {
38 	efi_file_handle_t *handle;
39 	u64 size;
40 };
41 
42 void efi_printk(efi_system_table_t *sys_table_arg, char *str)
43 {
44 	char *s8;
45 
46 	for (s8 = str; *s8; s8++) {
47 		efi_char16_t ch[2] = { 0 };
48 
49 		ch[0] = *s8;
50 		if (*s8 == '\n') {
51 			efi_char16_t nl[2] = { '\r', 0 };
52 			efi_char16_printk(sys_table_arg, nl);
53 		}
54 
55 		efi_char16_printk(sys_table_arg, ch);
56 	}
57 }
58 
59 static inline bool mmap_has_headroom(unsigned long buff_size,
60 				     unsigned long map_size,
61 				     unsigned long desc_size)
62 {
63 	unsigned long slack = buff_size - map_size;
64 
65 	return slack / desc_size >= EFI_MMAP_NR_SLACK_SLOTS;
66 }
67 
68 efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg,
69 				struct efi_boot_memmap *map)
70 {
71 	efi_memory_desc_t *m = NULL;
72 	efi_status_t status;
73 	unsigned long key;
74 	u32 desc_version;
75 
76 	*map->desc_size =	sizeof(*m);
77 	*map->map_size =	*map->desc_size * 32;
78 	*map->buff_size =	*map->map_size;
79 again:
80 	status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
81 				*map->map_size, (void **)&m);
82 	if (status != EFI_SUCCESS)
83 		goto fail;
84 
85 	*map->desc_size = 0;
86 	key = 0;
87 	status = efi_call_early(get_memory_map, map->map_size, m,
88 				&key, map->desc_size, &desc_version);
89 	if (status == EFI_BUFFER_TOO_SMALL ||
90 	    !mmap_has_headroom(*map->buff_size, *map->map_size,
91 			       *map->desc_size)) {
92 		efi_call_early(free_pool, m);
93 		/*
94 		 * Make sure there is some entries of headroom so that the
95 		 * buffer can be reused for a new map after allocations are
96 		 * no longer permitted.  Its unlikely that the map will grow to
97 		 * exceed this headroom once we are ready to trigger
98 		 * ExitBootServices()
99 		 */
100 		*map->map_size += *map->desc_size * EFI_MMAP_NR_SLACK_SLOTS;
101 		*map->buff_size = *map->map_size;
102 		goto again;
103 	}
104 
105 	if (status != EFI_SUCCESS)
106 		efi_call_early(free_pool, m);
107 
108 	if (map->key_ptr && status == EFI_SUCCESS)
109 		*map->key_ptr = key;
110 	if (map->desc_ver && status == EFI_SUCCESS)
111 		*map->desc_ver = desc_version;
112 
113 fail:
114 	*map->map = m;
115 	return status;
116 }
117 
118 
119 unsigned long get_dram_base(efi_system_table_t *sys_table_arg)
120 {
121 	efi_status_t status;
122 	unsigned long map_size, buff_size;
123 	unsigned long membase  = EFI_ERROR;
124 	struct efi_memory_map map;
125 	efi_memory_desc_t *md;
126 	struct efi_boot_memmap boot_map;
127 
128 	boot_map.map =		(efi_memory_desc_t **)&map.map;
129 	boot_map.map_size =	&map_size;
130 	boot_map.desc_size =	&map.desc_size;
131 	boot_map.desc_ver =	NULL;
132 	boot_map.key_ptr =	NULL;
133 	boot_map.buff_size =	&buff_size;
134 
135 	status = efi_get_memory_map(sys_table_arg, &boot_map);
136 	if (status != EFI_SUCCESS)
137 		return membase;
138 
139 	map.map_end = map.map + map_size;
140 
141 	for_each_efi_memory_desc_in_map(&map, md) {
142 		if (md->attribute & EFI_MEMORY_WB) {
143 			if (membase > md->phys_addr)
144 				membase = md->phys_addr;
145 		}
146 	}
147 
148 	efi_call_early(free_pool, map.map);
149 
150 	return membase;
151 }
152 
153 /*
154  * Allocate at the highest possible address that is not above 'max'.
155  */
156 efi_status_t efi_high_alloc(efi_system_table_t *sys_table_arg,
157 			    unsigned long size, unsigned long align,
158 			    unsigned long *addr, unsigned long max)
159 {
160 	unsigned long map_size, desc_size, buff_size;
161 	efi_memory_desc_t *map;
162 	efi_status_t status;
163 	unsigned long nr_pages;
164 	u64 max_addr = 0;
165 	int i;
166 	struct efi_boot_memmap boot_map;
167 
168 	boot_map.map =		&map;
169 	boot_map.map_size =	&map_size;
170 	boot_map.desc_size =	&desc_size;
171 	boot_map.desc_ver =	NULL;
172 	boot_map.key_ptr =	NULL;
173 	boot_map.buff_size =	&buff_size;
174 
175 	status = efi_get_memory_map(sys_table_arg, &boot_map);
176 	if (status != EFI_SUCCESS)
177 		goto fail;
178 
179 	/*
180 	 * Enforce minimum alignment that EFI or Linux requires when
181 	 * requesting a specific address.  We are doing page-based (or
182 	 * larger) allocations, and both the address and size must meet
183 	 * alignment constraints.
184 	 */
185 	if (align < EFI_ALLOC_ALIGN)
186 		align = EFI_ALLOC_ALIGN;
187 
188 	size = round_up(size, EFI_ALLOC_ALIGN);
189 	nr_pages = size / EFI_PAGE_SIZE;
190 again:
191 	for (i = 0; i < map_size / desc_size; i++) {
192 		efi_memory_desc_t *desc;
193 		unsigned long m = (unsigned long)map;
194 		u64 start, end;
195 
196 		desc = (efi_memory_desc_t *)(m + (i * desc_size));
197 		if (desc->type != EFI_CONVENTIONAL_MEMORY)
198 			continue;
199 
200 		if (desc->num_pages < nr_pages)
201 			continue;
202 
203 		start = desc->phys_addr;
204 		end = start + desc->num_pages * EFI_PAGE_SIZE;
205 
206 		if (end > max)
207 			end = max;
208 
209 		if ((start + size) > end)
210 			continue;
211 
212 		if (round_down(end - size, align) < start)
213 			continue;
214 
215 		start = round_down(end - size, align);
216 
217 		/*
218 		 * Don't allocate at 0x0. It will confuse code that
219 		 * checks pointers against NULL.
220 		 */
221 		if (start == 0x0)
222 			continue;
223 
224 		if (start > max_addr)
225 			max_addr = start;
226 	}
227 
228 	if (!max_addr)
229 		status = EFI_NOT_FOUND;
230 	else {
231 		status = efi_call_early(allocate_pages,
232 					EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
233 					nr_pages, &max_addr);
234 		if (status != EFI_SUCCESS) {
235 			max = max_addr;
236 			max_addr = 0;
237 			goto again;
238 		}
239 
240 		*addr = max_addr;
241 	}
242 
243 	efi_call_early(free_pool, map);
244 fail:
245 	return status;
246 }
247 
248 /*
249  * Allocate at the lowest possible address.
250  */
251 efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg,
252 			   unsigned long size, unsigned long align,
253 			   unsigned long *addr)
254 {
255 	unsigned long map_size, desc_size, buff_size;
256 	efi_memory_desc_t *map;
257 	efi_status_t status;
258 	unsigned long nr_pages;
259 	int i;
260 	struct efi_boot_memmap boot_map;
261 
262 	boot_map.map =		&map;
263 	boot_map.map_size =	&map_size;
264 	boot_map.desc_size =	&desc_size;
265 	boot_map.desc_ver =	NULL;
266 	boot_map.key_ptr =	NULL;
267 	boot_map.buff_size =	&buff_size;
268 
269 	status = efi_get_memory_map(sys_table_arg, &boot_map);
270 	if (status != EFI_SUCCESS)
271 		goto fail;
272 
273 	/*
274 	 * Enforce minimum alignment that EFI or Linux requires when
275 	 * requesting a specific address.  We are doing page-based (or
276 	 * larger) allocations, and both the address and size must meet
277 	 * alignment constraints.
278 	 */
279 	if (align < EFI_ALLOC_ALIGN)
280 		align = EFI_ALLOC_ALIGN;
281 
282 	size = round_up(size, EFI_ALLOC_ALIGN);
283 	nr_pages = size / EFI_PAGE_SIZE;
284 	for (i = 0; i < map_size / desc_size; i++) {
285 		efi_memory_desc_t *desc;
286 		unsigned long m = (unsigned long)map;
287 		u64 start, end;
288 
289 		desc = (efi_memory_desc_t *)(m + (i * desc_size));
290 
291 		if (desc->type != EFI_CONVENTIONAL_MEMORY)
292 			continue;
293 
294 		if (desc->num_pages < nr_pages)
295 			continue;
296 
297 		start = desc->phys_addr;
298 		end = start + desc->num_pages * EFI_PAGE_SIZE;
299 
300 		/*
301 		 * Don't allocate at 0x0. It will confuse code that
302 		 * checks pointers against NULL. Skip the first 8
303 		 * bytes so we start at a nice even number.
304 		 */
305 		if (start == 0x0)
306 			start += 8;
307 
308 		start = round_up(start, align);
309 		if ((start + size) > end)
310 			continue;
311 
312 		status = efi_call_early(allocate_pages,
313 					EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
314 					nr_pages, &start);
315 		if (status == EFI_SUCCESS) {
316 			*addr = start;
317 			break;
318 		}
319 	}
320 
321 	if (i == map_size / desc_size)
322 		status = EFI_NOT_FOUND;
323 
324 	efi_call_early(free_pool, map);
325 fail:
326 	return status;
327 }
328 
329 void efi_free(efi_system_table_t *sys_table_arg, unsigned long size,
330 	      unsigned long addr)
331 {
332 	unsigned long nr_pages;
333 
334 	if (!size)
335 		return;
336 
337 	nr_pages = round_up(size, EFI_ALLOC_ALIGN) / EFI_PAGE_SIZE;
338 	efi_call_early(free_pages, addr, nr_pages);
339 }
340 
341 /*
342  * Parse the ASCII string 'cmdline' for EFI options, denoted by the efi=
343  * option, e.g. efi=nochunk.
344  *
345  * It should be noted that efi= is parsed in two very different
346  * environments, first in the early boot environment of the EFI boot
347  * stub, and subsequently during the kernel boot.
348  */
349 efi_status_t efi_parse_options(char *cmdline)
350 {
351 	char *str;
352 
353 	/*
354 	 * If no EFI parameters were specified on the cmdline we've got
355 	 * nothing to do.
356 	 */
357 	str = strstr(cmdline, "efi=");
358 	if (!str)
359 		return EFI_SUCCESS;
360 
361 	/* Skip ahead to first argument */
362 	str += strlen("efi=");
363 
364 	/*
365 	 * Remember, because efi= is also used by the kernel we need to
366 	 * skip over arguments we don't understand.
367 	 */
368 	while (*str) {
369 		if (!strncmp(str, "nochunk", 7)) {
370 			str += strlen("nochunk");
371 			__chunk_size = -1UL;
372 		}
373 
374 		/* Group words together, delimited by "," */
375 		while (*str && *str != ',')
376 			str++;
377 
378 		if (*str == ',')
379 			str++;
380 	}
381 
382 	return EFI_SUCCESS;
383 }
384 
385 /*
386  * Check the cmdline for a LILO-style file= arguments.
387  *
388  * We only support loading a file from the same filesystem as
389  * the kernel image.
390  */
391 efi_status_t handle_cmdline_files(efi_system_table_t *sys_table_arg,
392 				  efi_loaded_image_t *image,
393 				  char *cmd_line, char *option_string,
394 				  unsigned long max_addr,
395 				  unsigned long *load_addr,
396 				  unsigned long *load_size)
397 {
398 	struct file_info *files;
399 	unsigned long file_addr;
400 	u64 file_size_total;
401 	efi_file_handle_t *fh = NULL;
402 	efi_status_t status;
403 	int nr_files;
404 	char *str;
405 	int i, j, k;
406 
407 	file_addr = 0;
408 	file_size_total = 0;
409 
410 	str = cmd_line;
411 
412 	j = 0;			/* See close_handles */
413 
414 	if (!load_addr || !load_size)
415 		return EFI_INVALID_PARAMETER;
416 
417 	*load_addr = 0;
418 	*load_size = 0;
419 
420 	if (!str || !*str)
421 		return EFI_SUCCESS;
422 
423 	for (nr_files = 0; *str; nr_files++) {
424 		str = strstr(str, option_string);
425 		if (!str)
426 			break;
427 
428 		str += strlen(option_string);
429 
430 		/* Skip any leading slashes */
431 		while (*str == '/' || *str == '\\')
432 			str++;
433 
434 		while (*str && *str != ' ' && *str != '\n')
435 			str++;
436 	}
437 
438 	if (!nr_files)
439 		return EFI_SUCCESS;
440 
441 	status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
442 				nr_files * sizeof(*files), (void **)&files);
443 	if (status != EFI_SUCCESS) {
444 		pr_efi_err(sys_table_arg, "Failed to alloc mem for file handle list\n");
445 		goto fail;
446 	}
447 
448 	str = cmd_line;
449 	for (i = 0; i < nr_files; i++) {
450 		struct file_info *file;
451 		efi_char16_t filename_16[256];
452 		efi_char16_t *p;
453 
454 		str = strstr(str, option_string);
455 		if (!str)
456 			break;
457 
458 		str += strlen(option_string);
459 
460 		file = &files[i];
461 		p = filename_16;
462 
463 		/* Skip any leading slashes */
464 		while (*str == '/' || *str == '\\')
465 			str++;
466 
467 		while (*str && *str != ' ' && *str != '\n') {
468 			if ((u8 *)p >= (u8 *)filename_16 + sizeof(filename_16))
469 				break;
470 
471 			if (*str == '/') {
472 				*p++ = '\\';
473 				str++;
474 			} else {
475 				*p++ = *str++;
476 			}
477 		}
478 
479 		*p = '\0';
480 
481 		/* Only open the volume once. */
482 		if (!i) {
483 			status = efi_open_volume(sys_table_arg, image,
484 						 (void **)&fh);
485 			if (status != EFI_SUCCESS)
486 				goto free_files;
487 		}
488 
489 		status = efi_file_size(sys_table_arg, fh, filename_16,
490 				       (void **)&file->handle, &file->size);
491 		if (status != EFI_SUCCESS)
492 			goto close_handles;
493 
494 		file_size_total += file->size;
495 	}
496 
497 	if (file_size_total) {
498 		unsigned long addr;
499 
500 		/*
501 		 * Multiple files need to be at consecutive addresses in memory,
502 		 * so allocate enough memory for all the files.  This is used
503 		 * for loading multiple files.
504 		 */
505 		status = efi_high_alloc(sys_table_arg, file_size_total, 0x1000,
506 				    &file_addr, max_addr);
507 		if (status != EFI_SUCCESS) {
508 			pr_efi_err(sys_table_arg, "Failed to alloc highmem for files\n");
509 			goto close_handles;
510 		}
511 
512 		/* We've run out of free low memory. */
513 		if (file_addr > max_addr) {
514 			pr_efi_err(sys_table_arg, "We've run out of free low memory\n");
515 			status = EFI_INVALID_PARAMETER;
516 			goto free_file_total;
517 		}
518 
519 		addr = file_addr;
520 		for (j = 0; j < nr_files; j++) {
521 			unsigned long size;
522 
523 			size = files[j].size;
524 			while (size) {
525 				unsigned long chunksize;
526 				if (size > __chunk_size)
527 					chunksize = __chunk_size;
528 				else
529 					chunksize = size;
530 
531 				status = efi_file_read(files[j].handle,
532 						       &chunksize,
533 						       (void *)addr);
534 				if (status != EFI_SUCCESS) {
535 					pr_efi_err(sys_table_arg, "Failed to read file\n");
536 					goto free_file_total;
537 				}
538 				addr += chunksize;
539 				size -= chunksize;
540 			}
541 
542 			efi_file_close(files[j].handle);
543 		}
544 
545 	}
546 
547 	efi_call_early(free_pool, files);
548 
549 	*load_addr = file_addr;
550 	*load_size = file_size_total;
551 
552 	return status;
553 
554 free_file_total:
555 	efi_free(sys_table_arg, file_size_total, file_addr);
556 
557 close_handles:
558 	for (k = j; k < i; k++)
559 		efi_file_close(files[k].handle);
560 free_files:
561 	efi_call_early(free_pool, files);
562 fail:
563 	*load_addr = 0;
564 	*load_size = 0;
565 
566 	return status;
567 }
568 /*
569  * Relocate a kernel image, either compressed or uncompressed.
570  * In the ARM64 case, all kernel images are currently
571  * uncompressed, and as such when we relocate it we need to
572  * allocate additional space for the BSS segment. Any low
573  * memory that this function should avoid needs to be
574  * unavailable in the EFI memory map, as if the preferred
575  * address is not available the lowest available address will
576  * be used.
577  */
578 efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg,
579 				 unsigned long *image_addr,
580 				 unsigned long image_size,
581 				 unsigned long alloc_size,
582 				 unsigned long preferred_addr,
583 				 unsigned long alignment)
584 {
585 	unsigned long cur_image_addr;
586 	unsigned long new_addr = 0;
587 	efi_status_t status;
588 	unsigned long nr_pages;
589 	efi_physical_addr_t efi_addr = preferred_addr;
590 
591 	if (!image_addr || !image_size || !alloc_size)
592 		return EFI_INVALID_PARAMETER;
593 	if (alloc_size < image_size)
594 		return EFI_INVALID_PARAMETER;
595 
596 	cur_image_addr = *image_addr;
597 
598 	/*
599 	 * The EFI firmware loader could have placed the kernel image
600 	 * anywhere in memory, but the kernel has restrictions on the
601 	 * max physical address it can run at.  Some architectures
602 	 * also have a prefered address, so first try to relocate
603 	 * to the preferred address.  If that fails, allocate as low
604 	 * as possible while respecting the required alignment.
605 	 */
606 	nr_pages = round_up(alloc_size, EFI_ALLOC_ALIGN) / EFI_PAGE_SIZE;
607 	status = efi_call_early(allocate_pages,
608 				EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
609 				nr_pages, &efi_addr);
610 	new_addr = efi_addr;
611 	/*
612 	 * If preferred address allocation failed allocate as low as
613 	 * possible.
614 	 */
615 	if (status != EFI_SUCCESS) {
616 		status = efi_low_alloc(sys_table_arg, alloc_size, alignment,
617 				       &new_addr);
618 	}
619 	if (status != EFI_SUCCESS) {
620 		pr_efi_err(sys_table_arg, "Failed to allocate usable memory for kernel.\n");
621 		return status;
622 	}
623 
624 	/*
625 	 * We know source/dest won't overlap since both memory ranges
626 	 * have been allocated by UEFI, so we can safely use memcpy.
627 	 */
628 	memcpy((void *)new_addr, (void *)cur_image_addr, image_size);
629 
630 	/* Return the new address of the relocated image. */
631 	*image_addr = new_addr;
632 
633 	return status;
634 }
635 
636 /*
637  * Get the number of UTF-8 bytes corresponding to an UTF-16 character.
638  * This overestimates for surrogates, but that is okay.
639  */
640 static int efi_utf8_bytes(u16 c)
641 {
642 	return 1 + (c >= 0x80) + (c >= 0x800);
643 }
644 
645 /*
646  * Convert an UTF-16 string, not necessarily null terminated, to UTF-8.
647  */
648 static u8 *efi_utf16_to_utf8(u8 *dst, const u16 *src, int n)
649 {
650 	unsigned int c;
651 
652 	while (n--) {
653 		c = *src++;
654 		if (n && c >= 0xd800 && c <= 0xdbff &&
655 		    *src >= 0xdc00 && *src <= 0xdfff) {
656 			c = 0x10000 + ((c & 0x3ff) << 10) + (*src & 0x3ff);
657 			src++;
658 			n--;
659 		}
660 		if (c >= 0xd800 && c <= 0xdfff)
661 			c = 0xfffd; /* Unmatched surrogate */
662 		if (c < 0x80) {
663 			*dst++ = c;
664 			continue;
665 		}
666 		if (c < 0x800) {
667 			*dst++ = 0xc0 + (c >> 6);
668 			goto t1;
669 		}
670 		if (c < 0x10000) {
671 			*dst++ = 0xe0 + (c >> 12);
672 			goto t2;
673 		}
674 		*dst++ = 0xf0 + (c >> 18);
675 		*dst++ = 0x80 + ((c >> 12) & 0x3f);
676 	t2:
677 		*dst++ = 0x80 + ((c >> 6) & 0x3f);
678 	t1:
679 		*dst++ = 0x80 + (c & 0x3f);
680 	}
681 
682 	return dst;
683 }
684 
685 #ifndef MAX_CMDLINE_ADDRESS
686 #define MAX_CMDLINE_ADDRESS	ULONG_MAX
687 #endif
688 
689 /*
690  * Convert the unicode UEFI command line to ASCII to pass to kernel.
691  * Size of memory allocated return in *cmd_line_len.
692  * Returns NULL on error.
693  */
694 char *efi_convert_cmdline(efi_system_table_t *sys_table_arg,
695 			  efi_loaded_image_t *image,
696 			  int *cmd_line_len)
697 {
698 	const u16 *s2;
699 	u8 *s1 = NULL;
700 	unsigned long cmdline_addr = 0;
701 	int load_options_chars = image->load_options_size / 2; /* UTF-16 */
702 	const u16 *options = image->load_options;
703 	int options_bytes = 0;  /* UTF-8 bytes */
704 	int options_chars = 0;  /* UTF-16 chars */
705 	efi_status_t status;
706 	u16 zero = 0;
707 
708 	if (options) {
709 		s2 = options;
710 		while (*s2 && *s2 != '\n'
711 		       && options_chars < load_options_chars) {
712 			options_bytes += efi_utf8_bytes(*s2++);
713 			options_chars++;
714 		}
715 	}
716 
717 	if (!options_chars) {
718 		/* No command line options, so return empty string*/
719 		options = &zero;
720 	}
721 
722 	options_bytes++;	/* NUL termination */
723 
724 	status = efi_high_alloc(sys_table_arg, options_bytes, 0,
725 				&cmdline_addr, MAX_CMDLINE_ADDRESS);
726 	if (status != EFI_SUCCESS)
727 		return NULL;
728 
729 	s1 = (u8 *)cmdline_addr;
730 	s2 = (const u16 *)options;
731 
732 	s1 = efi_utf16_to_utf8(s1, s2, options_chars);
733 	*s1 = '\0';
734 
735 	*cmd_line_len = options_bytes;
736 	return (char *)cmdline_addr;
737 }
738 
739 /*
740  * Handle calling ExitBootServices according to the requirements set out by the
741  * spec.  Obtains the current memory map, and returns that info after calling
742  * ExitBootServices.  The client must specify a function to perform any
743  * processing of the memory map data prior to ExitBootServices.  A client
744  * specific structure may be passed to the function via priv.  The client
745  * function may be called multiple times.
746  */
747 efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table_arg,
748 				    void *handle,
749 				    struct efi_boot_memmap *map,
750 				    void *priv,
751 				    efi_exit_boot_map_processing priv_func)
752 {
753 	efi_status_t status;
754 
755 	status = efi_get_memory_map(sys_table_arg, map);
756 
757 	if (status != EFI_SUCCESS)
758 		goto fail;
759 
760 	status = priv_func(sys_table_arg, map, priv);
761 	if (status != EFI_SUCCESS)
762 		goto free_map;
763 
764 	status = efi_call_early(exit_boot_services, handle, *map->key_ptr);
765 
766 	if (status == EFI_INVALID_PARAMETER) {
767 		/*
768 		 * The memory map changed between efi_get_memory_map() and
769 		 * exit_boot_services().  Per the UEFI Spec v2.6, Section 6.4:
770 		 * EFI_BOOT_SERVICES.ExitBootServices we need to get the
771 		 * updated map, and try again.  The spec implies one retry
772 		 * should be sufficent, which is confirmed against the EDK2
773 		 * implementation.  Per the spec, we can only invoke
774 		 * get_memory_map() and exit_boot_services() - we cannot alloc
775 		 * so efi_get_memory_map() cannot be used, and we must reuse
776 		 * the buffer.  For all practical purposes, the headroom in the
777 		 * buffer should account for any changes in the map so the call
778 		 * to get_memory_map() is expected to succeed here.
779 		 */
780 		*map->map_size = *map->buff_size;
781 		status = efi_call_early(get_memory_map,
782 					map->map_size,
783 					*map->map,
784 					map->key_ptr,
785 					map->desc_size,
786 					map->desc_ver);
787 
788 		/* exit_boot_services() was called, thus cannot free */
789 		if (status != EFI_SUCCESS)
790 			goto fail;
791 
792 		status = priv_func(sys_table_arg, map, priv);
793 		/* exit_boot_services() was called, thus cannot free */
794 		if (status != EFI_SUCCESS)
795 			goto fail;
796 
797 		status = efi_call_early(exit_boot_services, handle, *map->key_ptr);
798 	}
799 
800 	/* exit_boot_services() was called, thus cannot free */
801 	if (status != EFI_SUCCESS)
802 		goto fail;
803 
804 	return EFI_SUCCESS;
805 
806 free_map:
807 	efi_call_early(free_pool, *map->map);
808 fail:
809 	return status;
810 }
811