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 <linux/log2.h>
12 #include <asm/efi.h>
13
14 #include "efistub.h"
15
16 struct efi_rng_protocol {
17 efi_status_t (*get_info)(struct efi_rng_protocol *,
18 unsigned long *, efi_guid_t *);
19 efi_status_t (*get_rng)(struct efi_rng_protocol *,
20 efi_guid_t *, unsigned long, u8 *out);
21 };
22
efi_get_random_bytes(efi_system_table_t * sys_table_arg,unsigned long size,u8 * out)23 efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg,
24 unsigned long size, u8 *out)
25 {
26 efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
27 efi_status_t status;
28 struct efi_rng_protocol *rng;
29
30 status = efi_call_early(locate_protocol, &rng_proto, NULL,
31 (void **)&rng);
32 if (status != EFI_SUCCESS)
33 return status;
34
35 return rng->get_rng(rng, NULL, size, out);
36 }
37
38 /*
39 * Return the number of slots covered by this entry, i.e., the number of
40 * addresses it covers that are suitably aligned and supply enough room
41 * for the allocation.
42 */
get_entry_num_slots(efi_memory_desc_t * md,unsigned long size,unsigned long align_shift)43 static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
44 unsigned long size,
45 unsigned long align_shift)
46 {
47 unsigned long align = 1UL << align_shift;
48 u64 first_slot, last_slot, region_end;
49
50 if (md->type != EFI_CONVENTIONAL_MEMORY)
51 return 0;
52
53 region_end = min((u64)ULONG_MAX, md->phys_addr + md->num_pages*EFI_PAGE_SIZE - 1);
54
55 first_slot = round_up(md->phys_addr, align);
56 last_slot = round_down(region_end - size + 1, align);
57
58 if (first_slot > last_slot)
59 return 0;
60
61 return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
62 }
63
64 /*
65 * The UEFI memory descriptors have a virtual address field that is only used
66 * when installing the virtual mapping using SetVirtualAddressMap(). Since it
67 * is unused here, we can reuse it to keep track of each descriptor's slot
68 * count.
69 */
70 #define MD_NUM_SLOTS(md) ((md)->virt_addr)
71
efi_random_alloc(efi_system_table_t * sys_table_arg,unsigned long size,unsigned long align,unsigned long * addr,unsigned long random_seed)72 efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
73 unsigned long size,
74 unsigned long align,
75 unsigned long *addr,
76 unsigned long random_seed)
77 {
78 unsigned long map_size, desc_size, total_slots = 0, target_slot;
79 unsigned long buff_size;
80 efi_status_t status;
81 efi_memory_desc_t *memory_map;
82 int map_offset;
83 struct efi_boot_memmap map;
84
85 map.map = &memory_map;
86 map.map_size = &map_size;
87 map.desc_size = &desc_size;
88 map.desc_ver = NULL;
89 map.key_ptr = NULL;
90 map.buff_size = &buff_size;
91
92 status = efi_get_memory_map(sys_table_arg, &map);
93 if (status != EFI_SUCCESS)
94 return status;
95
96 if (align < EFI_ALLOC_ALIGN)
97 align = EFI_ALLOC_ALIGN;
98
99 /* count the suitable slots in each memory map entry */
100 for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
101 efi_memory_desc_t *md = (void *)memory_map + map_offset;
102 unsigned long slots;
103
104 slots = get_entry_num_slots(md, size, ilog2(align));
105 MD_NUM_SLOTS(md) = slots;
106 total_slots += slots;
107 }
108
109 /* find a random number between 0 and total_slots */
110 target_slot = (total_slots * (u16)random_seed) >> 16;
111
112 /*
113 * target_slot is now a value in the range [0, total_slots), and so
114 * it corresponds with exactly one of the suitable slots we recorded
115 * when iterating over the memory map the first time around.
116 *
117 * So iterate over the memory map again, subtracting the number of
118 * slots of each entry at each iteration, until we have found the entry
119 * that covers our chosen slot. Use the residual value of target_slot
120 * to calculate the randomly chosen address, and allocate it directly
121 * using EFI_ALLOCATE_ADDRESS.
122 */
123 for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
124 efi_memory_desc_t *md = (void *)memory_map + map_offset;
125 efi_physical_addr_t target;
126 unsigned long pages;
127
128 if (target_slot >= MD_NUM_SLOTS(md)) {
129 target_slot -= MD_NUM_SLOTS(md);
130 continue;
131 }
132
133 target = round_up(md->phys_addr, align) + target_slot * align;
134 pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
135
136 status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
137 EFI_LOADER_DATA, pages, &target);
138 if (status == EFI_SUCCESS)
139 *addr = target;
140 break;
141 }
142
143 efi_call_early(free_pool, memory_map);
144
145 return status;
146 }
147
efi_random_get_seed(efi_system_table_t * sys_table_arg)148 efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)
149 {
150 efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
151 efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW;
152 efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID;
153 struct efi_rng_protocol *rng;
154 struct linux_efi_random_seed *seed;
155 efi_status_t status;
156
157 status = efi_call_early(locate_protocol, &rng_proto, NULL,
158 (void **)&rng);
159 if (status != EFI_SUCCESS)
160 return status;
161
162 status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
163 sizeof(*seed) + EFI_RANDOM_SEED_SIZE,
164 (void **)&seed);
165 if (status != EFI_SUCCESS)
166 return status;
167
168 status = rng->get_rng(rng, &rng_algo_raw, EFI_RANDOM_SEED_SIZE,
169 seed->bits);
170 if (status == EFI_UNSUPPORTED)
171 /*
172 * Use whatever algorithm we have available if the raw algorithm
173 * is not implemented.
174 */
175 status = rng->get_rng(rng, NULL, EFI_RANDOM_SEED_SIZE,
176 seed->bits);
177
178 if (status != EFI_SUCCESS)
179 goto err_freepool;
180
181 seed->size = EFI_RANDOM_SEED_SIZE;
182 status = efi_call_early(install_configuration_table, &rng_table_guid,
183 seed);
184 if (status != EFI_SUCCESS)
185 goto err_freepool;
186
187 return EFI_SUCCESS;
188
189 err_freepool:
190 efi_call_early(free_pool, seed);
191 return status;
192 }
193