// SPDX-License-Identifier: GPL-2.0 /* * Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org> */ #include <linux/efi.h> #include <linux/log2.h> #include <asm/efi.h> #include "efistub.h" /* * Return the number of slots covered by this entry, i.e., the number of * addresses it covers that are suitably aligned and supply enough room * for the allocation. */ static unsigned long get_entry_num_slots(efi_memory_desc_t *md, unsigned long size, unsigned long align_shift) { unsigned long align = 1UL << align_shift; u64 first_slot, last_slot, region_end; if (md->type != EFI_CONVENTIONAL_MEMORY) return 0; if (efi_soft_reserve_enabled() && (md->attribute & EFI_MEMORY_SP)) return 0; region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, (u64)ULONG_MAX); first_slot = round_up(md->phys_addr, align); last_slot = round_down(region_end - size + 1, align); if (first_slot > last_slot) return 0; return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1; } /* * The UEFI memory descriptors have a virtual address field that is only used * when installing the virtual mapping using SetVirtualAddressMap(). Since it * is unused here, we can reuse it to keep track of each descriptor's slot * count. */ #define MD_NUM_SLOTS(md) ((md)->virt_addr) efi_status_t efi_random_alloc(unsigned long size, unsigned long align, unsigned long *addr, unsigned long random_seed) { unsigned long map_size, desc_size, total_slots = 0, target_slot; unsigned long buff_size; efi_status_t status; efi_memory_desc_t *memory_map; int map_offset; struct efi_boot_memmap map; map.map = &memory_map; map.map_size = &map_size; map.desc_size = &desc_size; map.desc_ver = NULL; map.key_ptr = NULL; map.buff_size = &buff_size; status = efi_get_memory_map(&map); if (status != EFI_SUCCESS) return status; if (align < EFI_ALLOC_ALIGN) align = EFI_ALLOC_ALIGN; /* count the suitable slots in each memory map entry */ for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { efi_memory_desc_t *md = (void *)memory_map + map_offset; unsigned long slots; slots = get_entry_num_slots(md, size, ilog2(align)); MD_NUM_SLOTS(md) = slots; total_slots += slots; } /* find a random number between 0 and total_slots */ target_slot = (total_slots * (u16)random_seed) >> 16; /* * target_slot is now a value in the range [0, total_slots), and so * it corresponds with exactly one of the suitable slots we recorded * when iterating over the memory map the first time around. * * So iterate over the memory map again, subtracting the number of * slots of each entry at each iteration, until we have found the entry * that covers our chosen slot. Use the residual value of target_slot * to calculate the randomly chosen address, and allocate it directly * using EFI_ALLOCATE_ADDRESS. */ for (map_offset = 0; map_offset < map_size; map_offset += desc_size) { efi_memory_desc_t *md = (void *)memory_map + map_offset; efi_physical_addr_t target; unsigned long pages; if (target_slot >= MD_NUM_SLOTS(md)) { target_slot -= MD_NUM_SLOTS(md); continue; } target = round_up(md->phys_addr, align) + target_slot * align; pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE; status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA, pages, &target); if (status == EFI_SUCCESS) *addr = target; break; } efi_bs_call(free_pool, memory_map); return status; }