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1// SPDX-License-Identifier: GPL-2.02/*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 of14 * addresses it covers that are suitably aligned and supply enough room15 * for the allocation.16 */17static 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 used48 * when installing the virtual mapping using SetVirtualAddressMap(). Since it49 * is unused here, we can reuse it to keep track of each descriptor's slot50 * count.51 */52#define MD_NUM_SLOTS(md) ((md)->virt_addr)53 54efi_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 so99 * it corresponds with exactly one of the suitable slots we recorded100 * when iterating over the memory map the first time around.101 *102 * So iterate over the memory map again, subtracting the number of103 * slots of each entry at each iteration, until we have found the entry104 * that covers our chosen slot. Use the residual value of target_slot105 * to calculate the randomly chosen address, and allocate it directly106 * 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_t(u64, 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