LXR linux/arch/arm64/kernel/efi.c

   1/*
   2 * Extensible Firmware Interface
   3 *
   4 * Based on Extensible Firmware Interface Specification version 2.4
   5 *
   6 * Copyright (C) 2013, 2014 Linaro Ltd.
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License version 2 as
  10 * published by the Free Software Foundation.
  11 *
  12 */
  13
  14#include <linux/dmi.h>
  15#include <linux/efi.h>
  16#include <linux/init.h>
  17
  18#include <asm/efi.h>
  19
  20/*
  21 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
  22 * executable, everything else can be mapped with the XN bits
  23 * set. Also take the new (optional) RO/XP bits into account.
  24 */
  25static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
  26{
  27        u64 attr = md->attribute;
  28        u32 type = md->type;
  29
  30        if (type == EFI_MEMORY_MAPPED_IO)
  31                return PROT_DEVICE_nGnRE;
  32
  33        if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
  34                      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
  35                /*
  36                 * If the region is not aligned to the page size of the OS, we
  37                 * can not use strict permissions, since that would also affect
  38                 * the mapping attributes of the adjacent regions.
  39                 */
  40                return pgprot_val(PAGE_KERNEL_EXEC);
  41
  42        /* R-- */
  43        if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
  44            (EFI_MEMORY_XP | EFI_MEMORY_RO))
  45                return pgprot_val(PAGE_KERNEL_RO);
  46
  47        /* R-X */
  48        if (attr & EFI_MEMORY_RO)
  49                return pgprot_val(PAGE_KERNEL_ROX);
  50
  51        /* RW- */
  52        if (attr & EFI_MEMORY_XP || type != EFI_RUNTIME_SERVICES_CODE)
  53                return pgprot_val(PAGE_KERNEL);
  54
  55        /* RWX */
  56        return pgprot_val(PAGE_KERNEL_EXEC);
  57}
  58
  59/* we will fill this structure from the stub, so don't put it in .bss */
  60struct screen_info screen_info __section(.data);
  61
  62int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
  63{
  64        pteval_t prot_val = create_mapping_protection(md);
  65
  66        create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
  67                           md->num_pages << EFI_PAGE_SHIFT,
  68                           __pgprot(prot_val | PTE_NG));
  69        return 0;
  70}
  71
  72static int __init arm64_dmi_init(void)
  73{
  74        /*
  75         * On arm64, DMI depends on UEFI, and dmi_scan_machine() needs to
  76         * be called early because dmi_id_init(), which is an arch_initcall
  77         * itself, depends on dmi_scan_machine() having been called already.
  78         */
  79        dmi_scan_machine();
  80        if (dmi_available)
  81                dmi_set_dump_stack_arch_desc();
  82        return 0;
  83}
  84core_initcall(arm64_dmi_init);
  85
  86/*
  87 * UpdateCapsule() depends on the system being shutdown via
  88 * ResetSystem().
  89 */
  90bool efi_poweroff_required(void)
  91{
  92        return efi_enabled(EFI_RUNTIME_SERVICES);
  93}
  94