1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
/*
* Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/efi.h>
#include <linux/log2.h>
#include <asm/efi.h>
#include "efistub.h"
struct efi_rng_protocol {
efi_status_t (*get_info)(struct efi_rng_protocol *,
unsigned long *, efi_guid_t *);
efi_status_t (*get_rng)(struct efi_rng_protocol *,
efi_guid_t *, unsigned long, u8 *out);
};
efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg,
unsigned long size, u8 *out)
{
efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
efi_status_t status;
struct efi_rng_protocol *rng;
status = efi_call_early(locate_protocol, &rng_proto, NULL,
(void **)&rng);
if (status != EFI_SUCCESS)
return status;
return rng->get_rng(rng, NULL, size, out);
}
/*
* Return the number of slots covered by this entry, i.e., the number of
* addresses it covers that are suitably aligned and supply enough room
* for the allocation.
*/
static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
unsigned long size,
unsigned long align_shift)
{
unsigned long align = 1UL << align_shift;
u64 first_slot, last_slot, region_end;
if (md->type != EFI_CONVENTIONAL_MEMORY)
return 0;
region_end = min((u64)ULONG_MAX, md->phys_addr + md->num_pages*EFI_PAGE_SIZE - 1);
first_slot = round_up(md->phys_addr, align);
last_slot = round_down(region_end - size + 1, align);
if (first_slot > last_slot)
return 0;
return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
}
/*
* The UEFI memory descriptors have a virtual address field that is only used
* when installing the virtual mapping using SetVirtualAddressMap(). Since it
* is unused here, we can reuse it to keep track of each descriptor's slot
* count.
*/
#define MD_NUM_SLOTS(md) ((md)->virt_addr)
efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
unsigned long size,
unsigned long align,
unsigned long *addr,
unsigned long random_seed)
{
unsigned long map_size, desc_size, total_slots = 0, target_slot;
unsigned long buff_size;
efi_status_t status;
efi_memory_desc_t *memory_map;
int map_offset;
struct efi_boot_memmap map;
map.map = &memory_map;
map.map_size = &map_size;
map.desc_size = &desc_size;
map.desc_ver = NULL;
map.key_ptr = NULL;
map.buff_size = &buff_size;
status = efi_get_memory_map(sys_table_arg, &map);
if (status != EFI_SUCCESS)
return status;
if (align < EFI_ALLOC_ALIGN)
align = EFI_ALLOC_ALIGN;
/* count the suitable slots in each memory map entry */
for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
efi_memory_desc_t *md = (void *)memory_map + map_offset;
unsigned long slots;
slots = get_entry_num_slots(md, size, ilog2(align));
MD_NUM_SLOTS(md) = slots;
total_slots += slots;
}
/* find a random number between 0 and total_slots */
target_slot = (total_slots * (u16)random_seed) >> 16;
/*
* target_slot is now a value in the range [0, total_slots), and so
* it corresponds with exactly one of the suitable slots we recorded
* when iterating over the memory map the first time around.
*
* So iterate over the memory map again, subtracting the number of
* slots of each entry at each iteration, until we have found the entry
* that covers our chosen slot. Use the residual value of target_slot
* to calculate the randomly chosen address, and allocate it directly
* using EFI_ALLOCATE_ADDRESS.
*/
for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
efi_memory_desc_t *md = (void *)memory_map + map_offset;
efi_physical_addr_t target;
unsigned long pages;
if (target_slot >= MD_NUM_SLOTS(md)) {
target_slot -= MD_NUM_SLOTS(md);
continue;
}
target = round_up(md->phys_addr, align) + target_slot * align;
pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
EFI_LOADER_DATA, pages, &target);
if (status == EFI_SUCCESS)
*addr = target;
break;
}
efi_call_early(free_pool, memory_map);
return status;
}
#define RANDOM_SEED_SIZE 32
efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)
{
efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW;
efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID;
struct efi_rng_protocol *rng;
struct linux_efi_random_seed *seed;
efi_status_t status;
status = efi_call_early(locate_protocol, &rng_proto, NULL,
(void **)&rng);
if (status != EFI_SUCCESS)
return status;
status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
sizeof(*seed) + RANDOM_SEED_SIZE,
(void **)&seed);
if (status != EFI_SUCCESS)
return status;
status = rng->get_rng(rng, &rng_algo_raw, RANDOM_SEED_SIZE,
seed->bits);
if (status == EFI_UNSUPPORTED)
/*
* Use whatever algorithm we have available if the raw algorithm
* is not implemented.
*/
status = rng->get_rng(rng, NULL, RANDOM_SEED_SIZE,
seed->bits);
if (status != EFI_SUCCESS)
goto err_freepool;
seed->size = RANDOM_SEED_SIZE;
status = efi_call_early(install_configuration_table, &rng_table_guid,
seed);
if (status != EFI_SUCCESS)
goto err_freepool;
return EFI_SUCCESS;
err_freepool:
efi_call_early(free_pool, seed);
return status;
}
|
