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 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 */ 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 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 } 147 148 #define RANDOM_SEED_SIZE 32 149 150 efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg) 151 { 152 efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; 153 efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW; 154 efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID; 155 struct efi_rng_protocol *rng; 156 struct linux_efi_random_seed *seed; 157 efi_status_t status; 158 159 status = efi_call_early(locate_protocol, &rng_proto, NULL, 160 (void **)&rng); 161 if (status != EFI_SUCCESS) 162 return status; 163 164 status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA, 165 sizeof(*seed) + RANDOM_SEED_SIZE, 166 (void **)&seed); 167 if (status != EFI_SUCCESS) 168 return status; 169 170 status = rng->get_rng(rng, &rng_algo_raw, RANDOM_SEED_SIZE, 171 seed->bits); 172 if (status == EFI_UNSUPPORTED) 173 /* 174 * Use whatever algorithm we have available if the raw algorithm 175 * is not implemented. 176 */ 177 status = rng->get_rng(rng, NULL, RANDOM_SEED_SIZE, 178 seed->bits); 179 180 if (status != EFI_SUCCESS) 181 goto err_freepool; 182 183 seed->size = RANDOM_SEED_SIZE; 184 status = efi_call_early(install_configuration_table, &rng_table_guid, 185 seed); 186 if (status != EFI_SUCCESS) 187 goto err_freepool; 188 189 return EFI_SUCCESS; 190 191 err_freepool: 192 efi_call_early(free_pool, seed); 193 return status; 194 } 195