arch/arm/kernel/efi.c

   1 /*
   2  * Copyright (C) 2015 Linaro Ltd <ard.biesheuvel@linaro.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/efi.h>
  10 #include <asm/efi.h>
  11 #include <asm/mach/map.h>
  12 #include <asm/mmu_context.h>
  13
  14 static int __init set_permissions(pte_t *ptep, pgtable_t token,
  15                                   unsigned long addr, void *data)
  16 {
  17         efi_memory_desc_t *md = data;
  18         pte_t pte = *ptep;
  19
  20         if (md->attribute & EFI_MEMORY_RO)
  21                 pte = set_pte_bit(pte, __pgprot(L_PTE_RDONLY));
  22         if (md->attribute & EFI_MEMORY_XP)
  23                 pte = set_pte_bit(pte, __pgprot(L_PTE_XN));
  24         set_pte_ext(ptep, pte, PTE_EXT_NG);
  25         return 0;
  26 }
  27
  28 int __init efi_set_mapping_permissions(struct mm_struct *mm,
  29                                        efi_memory_desc_t *md)
  30 {
  31         unsigned long base, size;
  32
  33         base = md->virt_addr;
  34         size = md->num_pages << EFI_PAGE_SHIFT;
  35
  36         /*
  37          * We can only use apply_to_page_range() if we can guarantee that the
  38          * entire region was mapped using pages. This should be the case if the
  39          * region does not cover any naturally aligned SECTION_SIZE sized
  40          * blocks.
  41          */
  42         if (round_down(base + size, SECTION_SIZE) <
  43             round_up(base, SECTION_SIZE) + SECTION_SIZE)
  44                 return apply_to_page_range(mm, base, size, set_permissions, md);
  45
  46         return 0;
  47 }
  48
  49 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
  50 {
  51         struct map_desc desc = {
  52                 .virtual        = md->virt_addr,
  53                 .pfn            = __phys_to_pfn(md->phys_addr),
  54                 .length         = md->num_pages * EFI_PAGE_SIZE,
  55         };
  56
  57         /*
  58          * Order is important here: memory regions may have all of the
  59          * bits below set (and usually do), so we check them in order of
  60          * preference.
  61          */
  62         if (md->attribute & EFI_MEMORY_WB)
  63                 desc.type = MT_MEMORY_RWX;
  64         else if (md->attribute & EFI_MEMORY_WT)
  65                 desc.type = MT_MEMORY_RWX_NONCACHED;
  66         else if (md->attribute & EFI_MEMORY_WC)
  67                 desc.type = MT_DEVICE_WC;
  68         else
  69                 desc.type = MT_DEVICE;
  70
  71         create_mapping_late(mm, &desc, true);
  72
  73         /*
  74          * If stricter permissions were specified, apply them now.
  75          */
  76         if (md->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))
  77                 return efi_set_mapping_permissions(mm, md);
  78         return 0;
  79 }