1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Extensible Firmware Interface
4 *
5 * Based on Extensible Firmware Interface Specification version 2.4
6 *
7 * Copyright (C) 2013, 2014 Linaro Ltd.
8 */
9
10 #include <linux/efi.h>
11 #include <linux/init.h>
12
13 #include <asm/efi.h>
14
15 /*
16 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
17 * executable, everything else can be mapped with the XN bits
18 * set. Also take the new (optional) RO/XP bits into account.
19 */
20 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
21 {
22 u64 attr = md->attribute;
23 u32 type = md->type;
24
25 if (type == EFI_MEMORY_MAPPED_IO)
26 return PROT_DEVICE_nGnRE;
27
28 if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
29 "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
30 /*
31 * If the region is not aligned to the page size of the OS, we
32 * can not use strict permissions, since that would also affect
33 * the mapping attributes of the adjacent regions.
34 */
35 return pgprot_val(PAGE_KERNEL_EXEC);
36
37 /* R-- */
38 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
39 (EFI_MEMORY_XP | EFI_MEMORY_RO))
40 return pgprot_val(PAGE_KERNEL_RO);
41
42 /* R-X */
43 if (attr & EFI_MEMORY_RO)
44 return pgprot_val(PAGE_KERNEL_ROX);
45
46 /* RW- */
47 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
48 EFI_MEMORY_XP) ||
49 type != EFI_RUNTIME_SERVICES_CODE)
50 return pgprot_val(PAGE_KERNEL);
51
52 /* RWX */
53 return pgprot_val(PAGE_KERNEL_EXEC);
54 }
55
56 /* we will fill this structure from the stub, so don't put it in .bss */
57 struct screen_info screen_info __section(".data");
58
59 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
60 {
61 pteval_t prot_val = create_mapping_protection(md);
62 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
63 md->type == EFI_RUNTIME_SERVICES_DATA);
64
65 if (!PAGE_ALIGNED(md->phys_addr) ||
66 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
67 /*
68 * If the end address of this region is not aligned to page
69 * size, the mapping is rounded up, and may end up sharing a
70 * page frame with the next UEFI memory region. If we create
71 * a block entry now, we may need to split it again when mapping
72 * the next region, and support for that is going to be removed
73 * from the MMU routines. So avoid block mappings altogether in
74 * that case.
75 */
76 page_mappings_only = true;
77 }
78
79 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
80 md->num_pages << EFI_PAGE_SHIFT,
81 __pgprot(prot_val | PTE_NG), page_mappings_only);
82 return 0;
83 }
84
85 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
86 {
87 efi_memory_desc_t *md = data;
88 pte_t pte = READ_ONCE(*ptep);
89
90 if (md->attribute & EFI_MEMORY_RO)
91 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
92 if (md->attribute & EFI_MEMORY_XP)
93 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
94 set_pte(ptep, pte);
95 return 0;
96 }
97
98 int __init efi_set_mapping_permissions(struct mm_struct *mm,
99 efi_memory_desc_t *md)
100 {
101 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
102 md->type != EFI_RUNTIME_SERVICES_DATA);
103
104 /*
105 * Calling apply_to_page_range() is only safe on regions that are
106 * guaranteed to be mapped down to pages. Since we are only called
107 * for regions that have been mapped using efi_create_mapping() above
108 * (and this is checked by the generic Memory Attributes table parsing
109 * routines), there is no need to check that again here.
110 */
111 return apply_to_page_range(mm, md->virt_addr,
112 md->num_pages << EFI_PAGE_SHIFT,
113 set_permissions, md);
114 }
115
116 /*
117 * UpdateCapsule() depends on the system being shutdown via
118 * ResetSystem().
119 */
120 bool efi_poweroff_required(void)
121 {
122 return efi_enabled(EFI_RUNTIME_SERVICES);
123 }
124
125 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
126 {
127 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
128 return s;
129 }
130
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