diff options
Diffstat (limited to 'drivers/firmware/efi/libstub/random.c')
| -rw-r--r-- | drivers/firmware/efi/libstub/random.c | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c new file mode 100644 index 000000000..e0e603a89 --- /dev/null +++ b/drivers/firmware/efi/libstub/random.c @@ -0,0 +1,192 @@ +/* + * 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; +} + +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) + EFI_RANDOM_SEED_SIZE, + (void **)&seed); + if (status != EFI_SUCCESS) + return status; + + status = rng->get_rng(rng, &rng_algo_raw, EFI_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, EFI_RANDOM_SEED_SIZE, + seed->bits); + + if (status != EFI_SUCCESS) + goto err_freepool; + + seed->size = EFI_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; +} |