1e4fbf476SArd Biesheuvel /* 2e4fbf476SArd Biesheuvel * Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org> 3e4fbf476SArd Biesheuvel * 4e4fbf476SArd Biesheuvel * This program is free software; you can redistribute it and/or modify 5e4fbf476SArd Biesheuvel * it under the terms of the GNU General Public License version 2 as 6e4fbf476SArd Biesheuvel * published by the Free Software Foundation. 7e4fbf476SArd Biesheuvel * 8e4fbf476SArd Biesheuvel */ 9e4fbf476SArd Biesheuvel 10e4fbf476SArd Biesheuvel #include <linux/efi.h> 11e4fbf476SArd Biesheuvel #include <asm/efi.h> 12e4fbf476SArd Biesheuvel 13e4fbf476SArd Biesheuvel #include "efistub.h" 14e4fbf476SArd Biesheuvel 15e4fbf476SArd Biesheuvel struct efi_rng_protocol { 16e4fbf476SArd Biesheuvel efi_status_t (*get_info)(struct efi_rng_protocol *, 17e4fbf476SArd Biesheuvel unsigned long *, efi_guid_t *); 18e4fbf476SArd Biesheuvel efi_status_t (*get_rng)(struct efi_rng_protocol *, 19e4fbf476SArd Biesheuvel efi_guid_t *, unsigned long, u8 *out); 20e4fbf476SArd Biesheuvel }; 21e4fbf476SArd Biesheuvel 22e4fbf476SArd Biesheuvel efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg, 23e4fbf476SArd Biesheuvel unsigned long size, u8 *out) 24e4fbf476SArd Biesheuvel { 25e4fbf476SArd Biesheuvel efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; 26e4fbf476SArd Biesheuvel efi_status_t status; 27e4fbf476SArd Biesheuvel struct efi_rng_protocol *rng; 28e4fbf476SArd Biesheuvel 29e4fbf476SArd Biesheuvel status = efi_call_early(locate_protocol, &rng_proto, NULL, 30e4fbf476SArd Biesheuvel (void **)&rng); 31e4fbf476SArd Biesheuvel if (status != EFI_SUCCESS) 32e4fbf476SArd Biesheuvel return status; 33e4fbf476SArd Biesheuvel 34e4fbf476SArd Biesheuvel return rng->get_rng(rng, NULL, size, out); 35e4fbf476SArd Biesheuvel } 362ddbfc81SArd Biesheuvel 372ddbfc81SArd Biesheuvel /* 382ddbfc81SArd Biesheuvel * Return the number of slots covered by this entry, i.e., the number of 392ddbfc81SArd Biesheuvel * addresses it covers that are suitably aligned and supply enough room 402ddbfc81SArd Biesheuvel * for the allocation. 412ddbfc81SArd Biesheuvel */ 422ddbfc81SArd Biesheuvel static unsigned long get_entry_num_slots(efi_memory_desc_t *md, 432ddbfc81SArd Biesheuvel unsigned long size, 442ddbfc81SArd Biesheuvel unsigned long align) 452ddbfc81SArd Biesheuvel { 462ddbfc81SArd Biesheuvel u64 start, end; 472ddbfc81SArd Biesheuvel 482ddbfc81SArd Biesheuvel if (md->type != EFI_CONVENTIONAL_MEMORY) 492ddbfc81SArd Biesheuvel return 0; 502ddbfc81SArd Biesheuvel 512ddbfc81SArd Biesheuvel start = round_up(md->phys_addr, align); 522ddbfc81SArd Biesheuvel end = round_down(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - size, 532ddbfc81SArd Biesheuvel align); 542ddbfc81SArd Biesheuvel 552ddbfc81SArd Biesheuvel if (start > end) 562ddbfc81SArd Biesheuvel return 0; 572ddbfc81SArd Biesheuvel 582ddbfc81SArd Biesheuvel return (end - start + 1) / align; 592ddbfc81SArd Biesheuvel } 602ddbfc81SArd Biesheuvel 612ddbfc81SArd Biesheuvel /* 622ddbfc81SArd Biesheuvel * The UEFI memory descriptors have a virtual address field that is only used 632ddbfc81SArd Biesheuvel * when installing the virtual mapping using SetVirtualAddressMap(). Since it 642ddbfc81SArd Biesheuvel * is unused here, we can reuse it to keep track of each descriptor's slot 652ddbfc81SArd Biesheuvel * count. 662ddbfc81SArd Biesheuvel */ 672ddbfc81SArd Biesheuvel #define MD_NUM_SLOTS(md) ((md)->virt_addr) 682ddbfc81SArd Biesheuvel 692ddbfc81SArd Biesheuvel efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg, 702ddbfc81SArd Biesheuvel unsigned long size, 712ddbfc81SArd Biesheuvel unsigned long align, 722ddbfc81SArd Biesheuvel unsigned long *addr, 732ddbfc81SArd Biesheuvel unsigned long random_seed) 742ddbfc81SArd Biesheuvel { 752ddbfc81SArd Biesheuvel unsigned long map_size, desc_size, total_slots = 0, target_slot; 762ddbfc81SArd Biesheuvel efi_status_t status; 772ddbfc81SArd Biesheuvel efi_memory_desc_t *memory_map; 782ddbfc81SArd Biesheuvel int map_offset; 792ddbfc81SArd Biesheuvel 802ddbfc81SArd Biesheuvel status = efi_get_memory_map(sys_table_arg, &memory_map, &map_size, 812ddbfc81SArd Biesheuvel &desc_size, NULL, NULL); 822ddbfc81SArd Biesheuvel if (status != EFI_SUCCESS) 832ddbfc81SArd Biesheuvel return status; 842ddbfc81SArd Biesheuvel 852ddbfc81SArd Biesheuvel if (align < EFI_ALLOC_ALIGN) 862ddbfc81SArd Biesheuvel align = EFI_ALLOC_ALIGN; 872ddbfc81SArd Biesheuvel 882ddbfc81SArd Biesheuvel /* count the suitable slots in each memory map entry */ 892ddbfc81SArd Biesheuvel for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { 902ddbfc81SArd Biesheuvel efi_memory_desc_t *md = (void *)memory_map + map_offset; 912ddbfc81SArd Biesheuvel unsigned long slots; 922ddbfc81SArd Biesheuvel 932ddbfc81SArd Biesheuvel slots = get_entry_num_slots(md, size, align); 942ddbfc81SArd Biesheuvel MD_NUM_SLOTS(md) = slots; 952ddbfc81SArd Biesheuvel total_slots += slots; 962ddbfc81SArd Biesheuvel } 972ddbfc81SArd Biesheuvel 982ddbfc81SArd Biesheuvel /* find a random number between 0 and total_slots */ 992ddbfc81SArd Biesheuvel target_slot = (total_slots * (u16)random_seed) >> 16; 1002ddbfc81SArd Biesheuvel 1012ddbfc81SArd Biesheuvel /* 1022ddbfc81SArd Biesheuvel * target_slot is now a value in the range [0, total_slots), and so 1032ddbfc81SArd Biesheuvel * it corresponds with exactly one of the suitable slots we recorded 1042ddbfc81SArd Biesheuvel * when iterating over the memory map the first time around. 1052ddbfc81SArd Biesheuvel * 1062ddbfc81SArd Biesheuvel * So iterate over the memory map again, subtracting the number of 1072ddbfc81SArd Biesheuvel * slots of each entry at each iteration, until we have found the entry 1082ddbfc81SArd Biesheuvel * that covers our chosen slot. Use the residual value of target_slot 1092ddbfc81SArd Biesheuvel * to calculate the randomly chosen address, and allocate it directly 1102ddbfc81SArd Biesheuvel * using EFI_ALLOCATE_ADDRESS. 1112ddbfc81SArd Biesheuvel */ 1122ddbfc81SArd Biesheuvel for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { 1132ddbfc81SArd Biesheuvel efi_memory_desc_t *md = (void *)memory_map + map_offset; 1142ddbfc81SArd Biesheuvel efi_physical_addr_t target; 1152ddbfc81SArd Biesheuvel unsigned long pages; 1162ddbfc81SArd Biesheuvel 1172ddbfc81SArd Biesheuvel if (target_slot >= MD_NUM_SLOTS(md)) { 1182ddbfc81SArd Biesheuvel target_slot -= MD_NUM_SLOTS(md); 1192ddbfc81SArd Biesheuvel continue; 1202ddbfc81SArd Biesheuvel } 1212ddbfc81SArd Biesheuvel 1222ddbfc81SArd Biesheuvel target = round_up(md->phys_addr, align) + target_slot * align; 1232ddbfc81SArd Biesheuvel pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE; 1242ddbfc81SArd Biesheuvel 1252ddbfc81SArd Biesheuvel status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS, 1262ddbfc81SArd Biesheuvel EFI_LOADER_DATA, pages, &target); 1272ddbfc81SArd Biesheuvel if (status == EFI_SUCCESS) 1282ddbfc81SArd Biesheuvel *addr = target; 1292ddbfc81SArd Biesheuvel break; 1302ddbfc81SArd Biesheuvel } 1312ddbfc81SArd Biesheuvel 1322ddbfc81SArd Biesheuvel efi_call_early(free_pool, memory_map); 1332ddbfc81SArd Biesheuvel 1342ddbfc81SArd Biesheuvel return status; 1352ddbfc81SArd Biesheuvel } 136