1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2016 Linaro Ltd;  <ard.biesheuvel@linaro.org>
4 */
5
6#include <linux/efi.h>
7#include <linux/log2.h>
8#include <asm/efi.h>
9
10#include "efistub.h"
11
12/*
13 * Return the number of slots covered by this entry, i.e., the number of
14 * addresses it covers that are suitably aligned and supply enough room
15 * for the allocation.
16 */
17static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
18					 unsigned long size,
19					 unsigned long align_shift,
20					 u64 alloc_min, u64 alloc_max)
21{
22	unsigned long align = 1UL << align_shift;
23	u64 first_slot, last_slot, region_end;
24
25	if (md->type != EFI_CONVENTIONAL_MEMORY)
26		return 0;
27
28	if (efi_soft_reserve_enabled() &&
29	    (md->attribute & EFI_MEMORY_SP))
30		return 0;
31
32	region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
33			 alloc_max);
34	if (region_end < size)
35		return 0;
36
37	first_slot = round_up(max(md->phys_addr, alloc_min), align);
38	last_slot = round_down(region_end - size + 1, align);
39
40	if (first_slot > last_slot)
41		return 0;
42
43	return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
44}
45
46/*
47 * The UEFI memory descriptors have a virtual address field that is only used
48 * when installing the virtual mapping using SetVirtualAddressMap(). Since it
49 * is unused here, we can reuse it to keep track of each descriptor's slot
50 * count.
51 */
52#define MD_NUM_SLOTS(md)	((md)->virt_addr)
53
54efi_status_t efi_random_alloc(unsigned long size,
55			      unsigned long align,
56			      unsigned long *addr,
57			      unsigned long random_seed,
58			      int memory_type,
59			      unsigned long alloc_min,
60			      unsigned long alloc_max)
61{
62	unsigned long total_slots = 0, target_slot;
63	unsigned long total_mirrored_slots = 0;
64	struct efi_boot_memmap *map;
65	efi_status_t status;
66	int map_offset;
67
68	status = efi_get_memory_map(&map, false);
69	if (status != EFI_SUCCESS)
70		return status;
71
72	if (align < EFI_ALLOC_ALIGN)
73		align = EFI_ALLOC_ALIGN;
74
75	size = round_up(size, EFI_ALLOC_ALIGN);
76
77	/* count the suitable slots in each memory map entry */
78	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
79		efi_memory_desc_t *md = (void *)map->map + map_offset;
80		unsigned long slots;
81
82		slots = get_entry_num_slots(md, size, ilog2(align), alloc_min,
83					    alloc_max);
84		MD_NUM_SLOTS(md) = slots;
85		total_slots += slots;
86		if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
87			total_mirrored_slots += slots;
88	}
89
90	/* consider only mirrored slots for randomization if any exist */
91	if (total_mirrored_slots > 0)
92		total_slots = total_mirrored_slots;
93
94	/* find a random number between 0 and total_slots */
95	target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
96
97	/*
98	 * target_slot is now a value in the range [0, total_slots), and so
99	 * it corresponds with exactly one of the suitable slots we recorded
100	 * when iterating over the memory map the first time around.
101	 *
102	 * So iterate over the memory map again, subtracting the number of
103	 * slots of each entry at each iteration, until we have found the entry
104	 * that covers our chosen slot. Use the residual value of target_slot
105	 * to calculate the randomly chosen address, and allocate it directly
106	 * using EFI_ALLOCATE_ADDRESS.
107	 */
108	status = EFI_OUT_OF_RESOURCES;
109	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
110		efi_memory_desc_t *md = (void *)map->map + map_offset;
111		efi_physical_addr_t target;
112		unsigned long pages;
113
114		if (total_mirrored_slots > 0 &&
115		    !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
116			continue;
117
118		if (target_slot >= MD_NUM_SLOTS(md)) {
119			target_slot -= MD_NUM_SLOTS(md);
120			continue;
121		}
122
123		target = round_up(md->phys_addr, align) + target_slot * align;
124		pages = size / EFI_PAGE_SIZE;
125
126		status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
127				     memory_type, pages, &target);
128		if (status == EFI_SUCCESS)
129			*addr = target;
130		break;
131	}
132
133	efi_bs_call(free_pool, map);
134
135	return status;
136}
137