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eab3126571
Currently, struct efi_boot_memmap is a struct that is passed around between callers of efi_get_memory_map() and the users of the resulting data, and which carries pointers to various variables whose values are provided by the EFI GetMemoryMap() boot service. This is overly complex, and it is much easier to carry these values in the struct itself. So turn the struct into one that carries these data items directly, including a flex array for the variable number of EFI memory descriptors that the boot service may return. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
131 lines
3.7 KiB
C
131 lines
3.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org>
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*/
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#include <linux/efi.h>
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#include <linux/log2.h>
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#include <asm/efi.h>
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#include "efistub.h"
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/*
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* Return the number of slots covered by this entry, i.e., the number of
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* addresses it covers that are suitably aligned and supply enough room
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* for the allocation.
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*/
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static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
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unsigned long size,
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unsigned long align_shift)
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{
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unsigned long align = 1UL << align_shift;
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u64 first_slot, last_slot, region_end;
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if (md->type != EFI_CONVENTIONAL_MEMORY)
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return 0;
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if (efi_soft_reserve_enabled() &&
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(md->attribute & EFI_MEMORY_SP))
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return 0;
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region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
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(u64)ULONG_MAX);
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if (region_end < size)
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return 0;
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first_slot = round_up(md->phys_addr, align);
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last_slot = round_down(region_end - size + 1, align);
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if (first_slot > last_slot)
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return 0;
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return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
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}
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/*
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* The UEFI memory descriptors have a virtual address field that is only used
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* when installing the virtual mapping using SetVirtualAddressMap(). Since it
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* is unused here, we can reuse it to keep track of each descriptor's slot
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* count.
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*/
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#define MD_NUM_SLOTS(md) ((md)->virt_addr)
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efi_status_t efi_random_alloc(unsigned long size,
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unsigned long align,
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unsigned long *addr,
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unsigned long random_seed)
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{
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unsigned long total_slots = 0, target_slot;
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unsigned long total_mirrored_slots = 0;
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struct efi_boot_memmap *map;
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efi_status_t status;
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int map_offset;
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status = efi_get_memory_map(&map);
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if (status != EFI_SUCCESS)
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return status;
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if (align < EFI_ALLOC_ALIGN)
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align = EFI_ALLOC_ALIGN;
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size = round_up(size, EFI_ALLOC_ALIGN);
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/* count the suitable slots in each memory map entry */
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for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
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efi_memory_desc_t *md = (void *)map->map + map_offset;
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unsigned long slots;
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slots = get_entry_num_slots(md, size, ilog2(align));
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MD_NUM_SLOTS(md) = slots;
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total_slots += slots;
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if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
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total_mirrored_slots += slots;
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}
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/* consider only mirrored slots for randomization if any exist */
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if (total_mirrored_slots > 0)
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total_slots = total_mirrored_slots;
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/* find a random number between 0 and total_slots */
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target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
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/*
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* target_slot is now a value in the range [0, total_slots), and so
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* it corresponds with exactly one of the suitable slots we recorded
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* when iterating over the memory map the first time around.
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*
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* So iterate over the memory map again, subtracting the number of
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* slots of each entry at each iteration, until we have found the entry
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* that covers our chosen slot. Use the residual value of target_slot
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* to calculate the randomly chosen address, and allocate it directly
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* using EFI_ALLOCATE_ADDRESS.
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*/
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for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
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efi_memory_desc_t *md = (void *)map->map + map_offset;
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efi_physical_addr_t target;
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unsigned long pages;
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if (total_mirrored_slots > 0 &&
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!(md->attribute & EFI_MEMORY_MORE_RELIABLE))
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continue;
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if (target_slot >= MD_NUM_SLOTS(md)) {
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target_slot -= MD_NUM_SLOTS(md);
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continue;
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}
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target = round_up(md->phys_addr, align) + target_slot * align;
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pages = size / EFI_PAGE_SIZE;
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status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
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EFI_LOADER_DATA, pages, &target);
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if (status == EFI_SUCCESS)
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*addr = target;
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break;
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}
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efi_bs_call(free_pool, map);
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return status;
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}
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