1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org> 4 */ 5 6 #include <linux/efi.h> 7 #include <linux/log2.h> 8 #include <asm/efi.h> 9 10 #include "efistub.h" 11 12 /* 13 * Return the number of slots covered by this entry, i.e., the number of 14 * addresses it covers that are suitably aligned and supply enough room 15 * for the allocation. 16 */ 17 static unsigned long get_entry_num_slots(efi_memory_desc_t *md, 18 unsigned long size, 19 unsigned long align_shift) 20 { 21 unsigned long align = 1UL << align_shift; 22 u64 first_slot, last_slot, region_end; 23 24 if (md->type != EFI_CONVENTIONAL_MEMORY) 25 return 0; 26 27 if (efi_soft_reserve_enabled() && 28 (md->attribute & EFI_MEMORY_SP)) 29 return 0; 30 31 region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, 32 (u64)EFI_ALLOC_LIMIT); 33 if (region_end < size) 34 return 0; 35 36 first_slot = round_up(md->phys_addr, align); 37 last_slot = round_down(region_end - size + 1, align); 38 39 if (first_slot > last_slot) 40 return 0; 41 42 return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1; 43 } 44 45 /* 46 * The UEFI memory descriptors have a virtual address field that is only used 47 * when installing the virtual mapping using SetVirtualAddressMap(). Since it 48 * is unused here, we can reuse it to keep track of each descriptor's slot 49 * count. 50 */ 51 #define MD_NUM_SLOTS(md) ((md)->virt_addr) 52 53 efi_status_t efi_random_alloc(unsigned long size, 54 unsigned long align, 55 unsigned long *addr, 56 unsigned long random_seed, 57 int memory_type) 58 { 59 unsigned long total_slots = 0, target_slot; 60 unsigned long total_mirrored_slots = 0; 61 struct efi_boot_memmap *map; 62 efi_status_t status; 63 int map_offset; 64 65 status = efi_get_memory_map(&map, false); 66 if (status != EFI_SUCCESS) 67 return status; 68 69 if (align < EFI_ALLOC_ALIGN) 70 align = EFI_ALLOC_ALIGN; 71 72 size = round_up(size, EFI_ALLOC_ALIGN); 73 74 /* count the suitable slots in each memory map entry */ 75 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 76 efi_memory_desc_t *md = (void *)map->map + map_offset; 77 unsigned long slots; 78 79 slots = get_entry_num_slots(md, size, ilog2(align)); 80 MD_NUM_SLOTS(md) = slots; 81 total_slots += slots; 82 if (md->attribute & EFI_MEMORY_MORE_RELIABLE) 83 total_mirrored_slots += slots; 84 } 85 86 /* consider only mirrored slots for randomization if any exist */ 87 if (total_mirrored_slots > 0) 88 total_slots = total_mirrored_slots; 89 90 /* find a random number between 0 and total_slots */ 91 target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32; 92 93 /* 94 * target_slot is now a value in the range [0, total_slots), and so 95 * it corresponds with exactly one of the suitable slots we recorded 96 * when iterating over the memory map the first time around. 97 * 98 * So iterate over the memory map again, subtracting the number of 99 * slots of each entry at each iteration, until we have found the entry 100 * that covers our chosen slot. Use the residual value of target_slot 101 * to calculate the randomly chosen address, and allocate it directly 102 * using EFI_ALLOCATE_ADDRESS. 103 */ 104 status = EFI_OUT_OF_RESOURCES; 105 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 106 efi_memory_desc_t *md = (void *)map->map + map_offset; 107 efi_physical_addr_t target; 108 unsigned long pages; 109 110 if (total_mirrored_slots > 0 && 111 !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) 112 continue; 113 114 if (target_slot >= MD_NUM_SLOTS(md)) { 115 target_slot -= MD_NUM_SLOTS(md); 116 continue; 117 } 118 119 target = round_up(md->phys_addr, align) + target_slot * align; 120 pages = size / EFI_PAGE_SIZE; 121 122 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, 123 memory_type, pages, &target); 124 if (status == EFI_SUCCESS) 125 *addr = target; 126 break; 127 } 128 129 efi_bs_call(free_pool, map); 130 131 return status; 132 } 133