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 (md->attribute & EFI_MEMORY_HOT_PLUGGABLE) 29 return 0; 30 31 if (efi_soft_reserve_enabled() && 32 (md->attribute & EFI_MEMORY_SP)) 33 return 0; 34 35 region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, 36 alloc_max); 37 if (region_end < size) 38 return 0; 39 40 first_slot = round_up(max(md->phys_addr, alloc_min), align); 41 last_slot = round_down(region_end - size + 1, align); 42 43 if (first_slot > last_slot) 44 return 0; 45 46 return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1; 47 } 48 49 /* 50 * The UEFI memory descriptors have a virtual address field that is only used 51 * when installing the virtual mapping using SetVirtualAddressMap(). Since it 52 * is unused here, we can reuse it to keep track of each descriptor's slot 53 * count. 54 */ 55 #define MD_NUM_SLOTS(md) ((md)->virt_addr) 56 57 efi_status_t efi_random_alloc(unsigned long size, 58 unsigned long align, 59 unsigned long *addr, 60 unsigned long random_seed, 61 int memory_type, 62 unsigned long alloc_min, 63 unsigned long alloc_max) 64 { 65 unsigned long total_slots = 0, target_slot; 66 unsigned long total_mirrored_slots = 0; 67 struct efi_boot_memmap *map; 68 efi_status_t status; 69 int map_offset; 70 71 status = efi_get_memory_map(&map, false); 72 if (status != EFI_SUCCESS) 73 return status; 74 75 if (align < EFI_ALLOC_ALIGN) 76 align = EFI_ALLOC_ALIGN; 77 78 /* Avoid address 0x0, as it can be mistaken for NULL */ 79 if (alloc_min == 0) 80 alloc_min = align; 81 82 size = round_up(size, EFI_ALLOC_ALIGN); 83 84 /* count the suitable slots in each memory map entry */ 85 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 86 efi_memory_desc_t *md = (void *)map->map + map_offset; 87 unsigned long slots; 88 89 slots = get_entry_num_slots(md, size, ilog2(align), alloc_min, 90 alloc_max); 91 MD_NUM_SLOTS(md) = slots; 92 total_slots += slots; 93 if (md->attribute & EFI_MEMORY_MORE_RELIABLE) 94 total_mirrored_slots += slots; 95 } 96 97 /* consider only mirrored slots for randomization if any exist */ 98 if (total_mirrored_slots > 0) 99 total_slots = total_mirrored_slots; 100 101 /* find a random number between 0 and total_slots */ 102 target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32; 103 104 /* 105 * target_slot is now a value in the range [0, total_slots), and so 106 * it corresponds with exactly one of the suitable slots we recorded 107 * when iterating over the memory map the first time around. 108 * 109 * So iterate over the memory map again, subtracting the number of 110 * slots of each entry at each iteration, until we have found the entry 111 * that covers our chosen slot. Use the residual value of target_slot 112 * to calculate the randomly chosen address, and allocate it directly 113 * using EFI_ALLOCATE_ADDRESS. 114 */ 115 status = EFI_OUT_OF_RESOURCES; 116 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 117 efi_memory_desc_t *md = (void *)map->map + map_offset; 118 efi_physical_addr_t target; 119 unsigned long pages; 120 121 if (total_mirrored_slots > 0 && 122 !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) 123 continue; 124 125 if (target_slot >= MD_NUM_SLOTS(md)) { 126 target_slot -= MD_NUM_SLOTS(md); 127 continue; 128 } 129 130 target = round_up(max_t(u64, md->phys_addr, alloc_min), align) + target_slot * align; 131 pages = size / EFI_PAGE_SIZE; 132 133 status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, 134 memory_type, pages, &target); 135 if (status == EFI_SUCCESS) 136 *addr = target; 137 break; 138 } 139 140 efi_bs_call(free_pool, map); 141 142 return status; 143 } 144