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141 lines · 4.0 KiB

1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2016 Linaro Ltd; <[email protected]>
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 (md->attribute & EFI_MEMORY_HOT_PLUGGABLE)
29 return 0;
30
31 if (efi_soft_reserve_enabled() &&
32 (md->attribute & EFI_MEMORY_SP))
33 return 0;
34
35 region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
36 alloc_max);
37 if (region_end < size)
38 return 0;
39
40 first_slot = round_up(max(md->phys_addr, alloc_min), align);
41 last_slot = round_down(region_end - size + 1, align);
42
43 if (first_slot > last_slot)
44 return 0;
45
46 return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
47}
48
49/*
50 * The UEFI memory descriptors have a virtual address field that is only used
51 * when installing the virtual mapping using SetVirtualAddressMap(). Since it
52 * is unused here, we can reuse it to keep track of each descriptor's slot
53 * count.
54 */
55#define MD_NUM_SLOTS(md) ((md)->virt_addr)
56
57efi_status_t efi_random_alloc(unsigned long size,
58 unsigned long align,
59 unsigned long *addr,
60 unsigned long random_seed,
61 int memory_type,
62 unsigned long alloc_min,
63 unsigned long alloc_max)
64{
65 struct efi_boot_memmap *map __free(efi_pool) = NULL;
66 unsigned long total_slots = 0, target_slot;
67 unsigned long total_mirrored_slots = 0;
68 efi_status_t status;
69 int map_offset;
70
71 status = efi_get_memory_map(&map, false);
72 if (status != EFI_SUCCESS)
73 return status;
74
75 if (align < EFI_ALLOC_ALIGN)
76 align = EFI_ALLOC_ALIGN;
77
78 /* Avoid address 0x0, as it can be mistaken for NULL */
79 if (alloc_min == 0)
80 alloc_min = align;
81
82 size = round_up(size, EFI_ALLOC_ALIGN);
83
84 /* count the suitable slots in each memory map entry */
85 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
86 efi_memory_desc_t *md = (void *)map->map + map_offset;
87 unsigned long slots;
88
89 slots = get_entry_num_slots(md, size, ilog2(align), alloc_min,
90 alloc_max);
91 MD_NUM_SLOTS(md) = slots;
92 total_slots += slots;
93 if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
94 total_mirrored_slots += slots;
95 }
96
97 /* consider only mirrored slots for randomization if any exist */
98 if (total_mirrored_slots > 0)
99 total_slots = total_mirrored_slots;
100
101 /* find a random number between 0 and total_slots */
102 target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
103
104 /*
105 * target_slot is now a value in the range [0, total_slots), and so
106 * it corresponds with exactly one of the suitable slots we recorded
107 * when iterating over the memory map the first time around.
108 *
109 * So iterate over the memory map again, subtracting the number of
110 * slots of each entry at each iteration, until we have found the entry
111 * that covers our chosen slot. Use the residual value of target_slot
112 * to calculate the randomly chosen address, and allocate it directly
113 * using EFI_ALLOCATE_ADDRESS.
114 */
115 status = EFI_OUT_OF_RESOURCES;
116 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
117 efi_memory_desc_t *md = (void *)map->map + map_offset;
118 efi_physical_addr_t target;
119 unsigned long pages;
120
121 if (total_mirrored_slots > 0 &&
122 !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
123 continue;
124
125 if (target_slot >= MD_NUM_SLOTS(md)) {
126 target_slot -= MD_NUM_SLOTS(md);
127 continue;
128 }
129
130 target = round_up(max_t(u64, md->phys_addr, alloc_min), align) + target_slot * align;
131 pages = size / EFI_PAGE_SIZE;
132
133 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
134 memory_type, pages, &target);
135 if (status == EFI_SUCCESS)
136 *addr = target;
137 break;
138 }
139
140 return status;
141}