arch/arm/kernel/efi.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2015 Linaro Ltd <ard.biesheuvel@linaro.org>
   4  */
   5
   6 #include <linux/efi.h>
   7 #include <asm/efi.h>
   8 #include <asm/mach/map.h>
   9 #include <asm/mmu_context.h>
  10
  11 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
  12 {
  13         efi_memory_desc_t *md = data;
  14         pte_t pte = *ptep;
  15
  16         if (md->attribute & EFI_MEMORY_RO)
  17                 pte = set_pte_bit(pte, __pgprot(L_PTE_RDONLY));
  18         if (md->attribute & EFI_MEMORY_XP)
  19                 pte = set_pte_bit(pte, __pgprot(L_PTE_XN));
  20         set_pte_ext(ptep, pte, PTE_EXT_NG);
  21         return 0;
  22 }
  23
  24 int __init efi_set_mapping_permissions(struct mm_struct *mm,
  25                                        efi_memory_desc_t *md)
  26 {
  27         unsigned long base, size;
  28
  29         base = md->virt_addr;
  30         size = md->num_pages << EFI_PAGE_SHIFT;
  31
  32         /*
  33          * We can only use apply_to_page_range() if we can guarantee that the
  34          * entire region was mapped using pages. This should be the case if the
  35          * region does not cover any naturally aligned SECTION_SIZE sized
  36          * blocks.
  37          */
  38         if (round_down(base + size, SECTION_SIZE) <
  39             round_up(base, SECTION_SIZE) + SECTION_SIZE)
  40                 return apply_to_page_range(mm, base, size, set_permissions, md);
  41
  42         return 0;
  43 }
  44
  45 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
  46 {
  47         struct map_desc desc = {
  48                 .virtual        = md->virt_addr,
  49                 .pfn            = __phys_to_pfn(md->phys_addr),
  50                 .length         = md->num_pages * EFI_PAGE_SIZE,
  51         };
  52
  53         /*
  54          * Order is important here: memory regions may have all of the
  55          * bits below set (and usually do), so we check them in order of
  56          * preference.
  57          */
  58         if (md->attribute & EFI_MEMORY_WB)
  59                 desc.type = MT_MEMORY_RWX;
  60         else if (md->attribute & EFI_MEMORY_WT)
  61                 desc.type = MT_MEMORY_RWX_NONCACHED;
  62         else if (md->attribute & EFI_MEMORY_WC)
  63                 desc.type = MT_DEVICE_WC;
  64         else
  65                 desc.type = MT_DEVICE;
  66
  67         create_mapping_late(mm, &desc, true);
  68
  69         /*
  70          * If stricter permissions were specified, apply them now.
  71          */
  72         if (md->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))
  73                 return efi_set_mapping_permissions(mm, md);
  74         return 0;
  75 }