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e4fbf476 AB |
1 | /* |
2 | * Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | * | |
8 | */ | |
9 | ||
10 | #include <linux/efi.h> | |
11 | #include <asm/efi.h> | |
12 | ||
13 | #include "efistub.h" | |
14 | ||
15 | struct efi_rng_protocol { | |
16 | efi_status_t (*get_info)(struct efi_rng_protocol *, | |
17 | unsigned long *, efi_guid_t *); | |
18 | efi_status_t (*get_rng)(struct efi_rng_protocol *, | |
19 | efi_guid_t *, unsigned long, u8 *out); | |
20 | }; | |
21 | ||
22 | efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg, | |
23 | unsigned long size, u8 *out) | |
24 | { | |
25 | efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; | |
26 | efi_status_t status; | |
27 | struct efi_rng_protocol *rng; | |
28 | ||
29 | status = efi_call_early(locate_protocol, &rng_proto, NULL, | |
30 | (void **)&rng); | |
31 | if (status != EFI_SUCCESS) | |
32 | return status; | |
33 | ||
34 | return rng->get_rng(rng, NULL, size, out); | |
35 | } | |
2ddbfc81 AB |
36 | |
37 | /* | |
38 | * Return the number of slots covered by this entry, i.e., the number of | |
39 | * addresses it covers that are suitably aligned and supply enough room | |
40 | * for the allocation. | |
41 | */ | |
42 | static unsigned long get_entry_num_slots(efi_memory_desc_t *md, | |
43 | unsigned long size, | |
44 | unsigned long align) | |
45 | { | |
46 | u64 start, end; | |
47 | ||
48 | if (md->type != EFI_CONVENTIONAL_MEMORY) | |
49 | return 0; | |
50 | ||
51 | start = round_up(md->phys_addr, align); | |
52 | end = round_down(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - size, | |
53 | align); | |
54 | ||
55 | if (start > end) | |
56 | return 0; | |
57 | ||
58 | return (end - start + 1) / align; | |
59 | } | |
60 | ||
61 | /* | |
62 | * The UEFI memory descriptors have a virtual address field that is only used | |
63 | * when installing the virtual mapping using SetVirtualAddressMap(). Since it | |
64 | * is unused here, we can reuse it to keep track of each descriptor's slot | |
65 | * count. | |
66 | */ | |
67 | #define MD_NUM_SLOTS(md) ((md)->virt_addr) | |
68 | ||
69 | efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg, | |
70 | unsigned long size, | |
71 | unsigned long align, | |
72 | unsigned long *addr, | |
73 | unsigned long random_seed) | |
74 | { | |
75 | unsigned long map_size, desc_size, total_slots = 0, target_slot; | |
dadb57ab | 76 | unsigned long buff_size; |
2ddbfc81 AB |
77 | efi_status_t status; |
78 | efi_memory_desc_t *memory_map; | |
79 | int map_offset; | |
dadb57ab | 80 | struct efi_boot_memmap map; |
2ddbfc81 | 81 | |
dadb57ab JH |
82 | map.map = &memory_map; |
83 | map.map_size = &map_size; | |
84 | map.desc_size = &desc_size; | |
85 | map.desc_ver = NULL; | |
86 | map.key_ptr = NULL; | |
87 | map.buff_size = &buff_size; | |
88 | ||
89 | status = efi_get_memory_map(sys_table_arg, &map); | |
2ddbfc81 AB |
90 | if (status != EFI_SUCCESS) |
91 | return status; | |
92 | ||
93 | if (align < EFI_ALLOC_ALIGN) | |
94 | align = EFI_ALLOC_ALIGN; | |
95 | ||
96 | /* count the suitable slots in each memory map entry */ | |
97 | for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { | |
98 | efi_memory_desc_t *md = (void *)memory_map + map_offset; | |
99 | unsigned long slots; | |
100 | ||
101 | slots = get_entry_num_slots(md, size, align); | |
102 | MD_NUM_SLOTS(md) = slots; | |
103 | total_slots += slots; | |
104 | } | |
105 | ||
106 | /* find a random number between 0 and total_slots */ | |
107 | target_slot = (total_slots * (u16)random_seed) >> 16; | |
108 | ||
109 | /* | |
110 | * target_slot is now a value in the range [0, total_slots), and so | |
111 | * it corresponds with exactly one of the suitable slots we recorded | |
112 | * when iterating over the memory map the first time around. | |
113 | * | |
114 | * So iterate over the memory map again, subtracting the number of | |
115 | * slots of each entry at each iteration, until we have found the entry | |
116 | * that covers our chosen slot. Use the residual value of target_slot | |
117 | * to calculate the randomly chosen address, and allocate it directly | |
118 | * using EFI_ALLOCATE_ADDRESS. | |
119 | */ | |
120 | for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { | |
121 | efi_memory_desc_t *md = (void *)memory_map + map_offset; | |
122 | efi_physical_addr_t target; | |
123 | unsigned long pages; | |
124 | ||
125 | if (target_slot >= MD_NUM_SLOTS(md)) { | |
126 | target_slot -= MD_NUM_SLOTS(md); | |
127 | continue; | |
128 | } | |
129 | ||
130 | target = round_up(md->phys_addr, align) + target_slot * align; | |
131 | pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE; | |
132 | ||
133 | status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS, | |
134 | EFI_LOADER_DATA, pages, &target); | |
135 | if (status == EFI_SUCCESS) | |
136 | *addr = target; | |
137 | break; | |
138 | } | |
139 | ||
140 | efi_call_early(free_pool, memory_map); | |
141 | ||
142 | return status; | |
143 | } |