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 u64 alloc_min, u64 alloc_max) 21 { 22 unsigned long align = 1UL << align_shift; 23 u64 first_slot, last_slot, region_end; 24 25 if (md->type != EFI_CONVENTIONAL_MEMORY) 26 return 0; 27 28 if (efi_soft_reserve_enabled() && 29 (md->attribute & EFI_MEMORY_SP)) 30 return 0; 31 32 region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, 33 alloc_max); 34 if (region_end < size) 35 return 0; 36 37 first_slot = round_up(max(md->phys_addr, alloc_min), align); 38 last_slot = round_down(region_end - size + 1, align); 39 40 if (first_slot > last_slot) 41 return 0; 42 43 return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1; 44 } 45 46 /* 47 * The UEFI memory descriptors have a virtual address field that is only used 48 * when installing the virtual mapping using SetVirtualAddressMap(). Since it 49 * is unused here, we can reuse it to keep track of each descriptor's slot 50 * count. 51 */ 52 #define MD_NUM_SLOTS(md) ((md)->virt_addr) 53 54 efi_status_t efi_random_alloc(unsigned long size, 55 unsigned long align, 56 unsigned long *addr, 57 unsigned long random_seed, 58 int memory_type, 59 unsigned long alloc_min, 60 unsigned long alloc_max) 61 { 62 unsigned long total_slots = 0, target_slot; 63 unsigned long total_mirrored_slots = 0; 64 struct efi_boot_memmap *map; 65 efi_status_t status; 66 int map_offset; 67 68 status = efi_get_memory_map(&map, false); 69 if (status != EFI_SUCCESS) 70 return status; 71 72 if (align < EFI_ALLOC_ALIGN) 73 align = EFI_ALLOC_ALIGN; 74 75 size = round_up(size, EFI_ALLOC_ALIGN); 76 77 /* count the suitable slots in each memory map entry */ 78 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 79 efi_memory_desc_t *md = (void *)map->map + map_offset; 80 unsigned long slots; 81 82 slots = get_entry_num_slots(md, size, ilog2(align), alloc_min, 83 alloc_max); 84 MD_NUM_SLOTS(md) = slots; 85 total_slots += slots; 86 if (md->attribute & EFI_MEMORY_MORE_RELIABLE) 87 total_mirrored_slots += slots; 88 } 89 90 /* consider only mirrored slots for randomization if any exist */ 91 if (total_mirrored_slots > 0) 92 total_slots = total_mirrored_slots; 93 94 /* find a random number between 0 and total_slots */ 95 target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32; 96 97 /* 98 * target_slot is now a value in the range [0, total_slots), and so 99 * it corresponds with exactly one of the suitable slots we recorded 100 * when iterating over the memory map the first time around. 101 * 102 * So iterate over the memory map again, subtracting the number of 103 * slots of each entry at each iteration, until we have found the entry 104 * that covers our chosen slot. Use the residual value of target_slot 105 * to calculate the randomly chosen address, and allocate it directly 106 * using EFI_ALLOCATE_ADDRESS. 107 */ 108 status = EFI_OUT_OF_RESOURCES; 109 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 110 efi_memory_desc_t *md = (void *)map->map + map_offset; 111 efi_physical_addr_t target; 112 unsigned long pages; 113 114 if (total_mirrored_slots > 0 && 115 !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) 116 continue; 117 118 if (target_slot >= MD_NUM_SLOTS(md)) { 119 target_slot -= MD_NUM_SLOTS(md); 120 continue; 121 } 122 123 target = round_up(max(md->phys_addr, alloc_min), align) + target_slot * align; 124 pages = size / EFI_PAGE_SIZE; 125 126 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, 127 memory_type, pages, &target); 128 if (status == EFI_SUCCESS) 129 *addr = target; 130 break; 131 } 132 133 efi_bs_call(free_pool, map); 134 135 return status; 136 } 137