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  */
  25 static __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 */
  60 struct screen_info screen_info __section(.data);
  61
  62 int __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
  72 static 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 }
  84 core_initcall(arm64_dmi_init);
  85
  86 /*
  87  * UpdateCapsule() depends on the system being shutdown via
  88  * ResetSystem().
  89  */
  90 bool efi_poweroff_required(void)
  91 {
  92         return efi_enabled(EFI_RUNTIME_SERVICES);
  93 }