136 строки
3.8 KiB
C
136 строки
3.8 KiB
C
/*
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* Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/efi.h>
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#include <asm/efi.h>
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#include "efistub.h"
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struct efi_rng_protocol {
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efi_status_t (*get_info)(struct efi_rng_protocol *,
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unsigned long *, efi_guid_t *);
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efi_status_t (*get_rng)(struct efi_rng_protocol *,
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efi_guid_t *, unsigned long, u8 *out);
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};
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efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg,
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unsigned long size, u8 *out)
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{
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efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
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efi_status_t status;
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struct efi_rng_protocol *rng;
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status = efi_call_early(locate_protocol, &rng_proto, NULL,
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(void **)&rng);
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if (status != EFI_SUCCESS)
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return status;
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return rng->get_rng(rng, NULL, size, out);
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}
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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)
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{
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u64 start, end;
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if (md->type != EFI_CONVENTIONAL_MEMORY)
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return 0;
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start = round_up(md->phys_addr, align);
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end = round_down(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - size,
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align);
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if (start > end)
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return 0;
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return (end - start + 1) / align;
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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(efi_system_table_t *sys_table_arg,
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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 map_size, desc_size, total_slots = 0, target_slot;
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efi_status_t status;
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efi_memory_desc_t *memory_map;
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int map_offset;
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status = efi_get_memory_map(sys_table_arg, &memory_map, &map_size,
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&desc_size, NULL, NULL);
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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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/* count the suitable slots in each memory map entry */
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for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
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efi_memory_desc_t *md = (void *)memory_map + map_offset;
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unsigned long slots;
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slots = get_entry_num_slots(md, size, align);
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MD_NUM_SLOTS(md) = slots;
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total_slots += slots;
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}
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/* find a random number between 0 and total_slots */
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target_slot = (total_slots * (u16)random_seed) >> 16;
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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_size; map_offset += desc_size) {
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efi_memory_desc_t *md = (void *)memory_map + map_offset;
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efi_physical_addr_t target;
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unsigned long pages;
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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 = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
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status = efi_call_early(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_call_early(free_pool, memory_map);
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return status;
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}
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