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| 2 | |
| 3 | * Copyright (C) 2020 Western Digital Corporation or its affiliates.
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| 4 | * Adapted from arch/arm64/kernel/efi.c
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| 5 |
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| 6 |
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| 7 | #include <linux/efi.h>
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| 8 | #include <linux/init.h>
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| 9 |
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| 10 | #include <asm/efi.h>
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| 11 | #include <asm/pgtable.h>
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| 12 | #include <asm/pgtable-bits.h>
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| 13 |
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| 14 | |
| 15 | * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
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| 16 | * executable, everything else can be mapped with the XN bits
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| 17 | * set. Also take the new (optional) RO/XP bits into account.
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| 18 |
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| 19 | static __init pgprot_t efimem_to_pgprot_map(efi_memory_desc_t *md)
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| 20 | {
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| 21 | u64 attr = md->attribute;
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| 22 | u32 type = md->type;
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| 23 |
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| 24 | if (type == EFI_MEMORY_MAPPED_IO)
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| 25 | return PAGE_KERNEL;
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| 26 |
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| 27 |
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| 28 | if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
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| 29 | (EFI_MEMORY_XP | EFI_MEMORY_RO))
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| 30 | return PAGE_KERNEL_READ;
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| 31 |
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| 32 |
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| 33 | if (attr & EFI_MEMORY_RO)
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| 34 | return PAGE_KERNEL_READ_EXEC;
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| 35 |
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| 36 |
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| 37 | if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
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| 38 | EFI_MEMORY_XP) ||
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| 39 | type != EFI_RUNTIME_SERVICES_CODE)
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| 40 | return PAGE_KERNEL;
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| 41 |
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| 42 |
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| 43 | return PAGE_KERNEL_EXEC;
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| 44 | }
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| 45 |
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| 46 | int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
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| 47 | {
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| 48 | pgprot_t prot = __pgprot(pgprot_val(efimem_to_pgprot_map(md)) &
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| 49 | ~(_PAGE_GLOBAL));
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| 50 | int i;
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| 51 |
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| 52 |
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| 53 | for (i = 0; i < md->num_pages; i++)
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| 54 | create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE,
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| 55 | md->phys_addr + i * PAGE_SIZE,
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| 56 | PAGE_SIZE, prot);
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| 57 | return 0;
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| 58 | }
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| 59 |
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| 60 | static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
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| 61 | {
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| 62 | efi_memory_desc_t *md = data;
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| 63 | pte_t pte = ptep_get(ptep);
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| 64 | unsigned long val;
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| 65 |
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| 66 | if (md->attribute & EFI_MEMORY_RO) {
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| 67 | val = pte_val(pte) & ~_PAGE_WRITE;
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| 68 | val |= _PAGE_READ;
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| 69 | pte = __pte(val);
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| 70 | }
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| 71 | if (md->attribute & EFI_MEMORY_XP) {
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| 72 | val = pte_val(pte) & ~_PAGE_EXEC;
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| 73 | pte = __pte(val);
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| 74 | }
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| 75 | set_pte(ptep, pte);
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| 76 |
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| 77 | return 0;
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| 78 | }
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| 79 |
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| 80 | int __init efi_set_mapping_permissions(struct mm_struct *mm,
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| 81 | efi_memory_desc_t *md,
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| 82 | bool ignored)
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| 83 | {
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| 84 | BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
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| 85 | md->type != EFI_RUNTIME_SERVICES_DATA);
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| 86 |
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| 87 | |
| 88 | * Calling apply_to_page_range() is only safe on regions that are
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| 89 | * guaranteed to be mapped down to pages. Since we are only called
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| 90 | * for regions that have been mapped using efi_create_mapping() above
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| 91 | * (and this is checked by the generic Memory Attributes table parsing
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| 92 | * routines), there is no need to check that again here.
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| 93 |
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| 94 | return apply_to_page_range(mm, md->virt_addr,
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| 95 | md->num_pages << EFI_PAGE_SHIFT,
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| 96 | set_permissions, md);
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| 97 | }
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| 98 |
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| 99 | bool efi_poweroff_required(void)
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| 100 | {
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| 101 | return efi_enabled(EFI_RUNTIME_SERVICES);
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| 102 | }
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