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 */
get_entry_num_slots(efi_memory_desc_t * md,unsigned long size,unsigned long align_shift,u64 alloc_limit)17 static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
18 unsigned long size,
19 unsigned long align_shift,
20 u64 alloc_limit)
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_limit);
34 if (region_end < size)
35 return 0;
36
37 first_slot = round_up(md->phys_addr, 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
efi_random_alloc(unsigned long size,unsigned long align,unsigned long * addr,unsigned long random_seed,int memory_type,unsigned long alloc_limit)54 efi_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_limit)
60 {
61 unsigned long total_slots = 0, target_slot;
62 unsigned long total_mirrored_slots = 0;
63 struct efi_boot_memmap *map;
64 efi_status_t status;
65 int map_offset;
66
67 status = efi_get_memory_map(&map, false);
68 if (status != EFI_SUCCESS)
69 return status;
70
71 if (align < EFI_ALLOC_ALIGN)
72 align = EFI_ALLOC_ALIGN;
73
74 size = round_up(size, EFI_ALLOC_ALIGN);
75
76 /* count the suitable slots in each memory map entry */
77 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
78 efi_memory_desc_t *md = (void *)map->map + map_offset;
79 unsigned long slots;
80
81 slots = get_entry_num_slots(md, size, ilog2(align), alloc_limit);
82 MD_NUM_SLOTS(md) = slots;
83 total_slots += slots;
84 if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
85 total_mirrored_slots += slots;
86 }
87
88 /* consider only mirrored slots for randomization if any exist */
89 if (total_mirrored_slots > 0)
90 total_slots = total_mirrored_slots;
91
92 /* find a random number between 0 and total_slots */
93 target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
94
95 /*
96 * target_slot is now a value in the range [0, total_slots), and so
97 * it corresponds with exactly one of the suitable slots we recorded
98 * when iterating over the memory map the first time around.
99 *
100 * So iterate over the memory map again, subtracting the number of
101 * slots of each entry at each iteration, until we have found the entry
102 * that covers our chosen slot. Use the residual value of target_slot
103 * to calculate the randomly chosen address, and allocate it directly
104 * using EFI_ALLOCATE_ADDRESS.
105 */
106 status = EFI_OUT_OF_RESOURCES;
107 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
108 efi_memory_desc_t *md = (void *)map->map + map_offset;
109 efi_physical_addr_t target;
110 unsigned long pages;
111
112 if (total_mirrored_slots > 0 &&
113 !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
114 continue;
115
116 if (target_slot >= MD_NUM_SLOTS(md)) {
117 target_slot -= MD_NUM_SLOTS(md);
118 continue;
119 }
120
121 target = round_up(md->phys_addr, align) + target_slot * align;
122 pages = size / EFI_PAGE_SIZE;
123
124 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
125 memory_type, pages, &target);
126 if (status == EFI_SUCCESS)
127 *addr = target;
128 break;
129 }
130
131 efi_bs_call(free_pool, map);
132
133 return status;
134 }
135