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
region_is_misaligned(const efi_memory_desc_t * md)15 static bool region_is_misaligned(const efi_memory_desc_t *md)
16 {
17 if (PAGE_SIZE == EFI_PAGE_SIZE)
18 return false;
19 return !PAGE_ALIGNED(md->phys_addr) ||
20 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
21 }
22
23 /*
24 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
25 * executable, everything else can be mapped with the XN bits
26 * set. Also take the new (optional) RO/XP bits into account.
27 */
create_mapping_protection(efi_memory_desc_t * md)28 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
29 {
30 u64 attr = md->attribute;
31 u32 type = md->type;
32
33 if (type == EFI_MEMORY_MAPPED_IO)
34 return PROT_DEVICE_nGnRE;
35
36 if (region_is_misaligned(md)) {
37 static bool __initdata code_is_misaligned;
38
39 /*
40 * Regions that are not aligned to the OS page size cannot be
41 * mapped with strict permissions, as those might interfere
42 * with the permissions that are needed by the adjacent
43 * region's mapping. However, if we haven't encountered any
44 * misaligned runtime code regions so far, we can safely use
45 * non-executable permissions for non-code regions.
46 */
47 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
48
49 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
50 : pgprot_val(PAGE_KERNEL);
51 }
52
53 /* R-- */
54 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
55 (EFI_MEMORY_XP | EFI_MEMORY_RO))
56 return pgprot_val(PAGE_KERNEL_RO);
57
58 /* R-X */
59 if (attr & EFI_MEMORY_RO)
60 return pgprot_val(PAGE_KERNEL_ROX);
61
62 /* RW- */
63 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
64 EFI_MEMORY_XP) ||
65 type != EFI_RUNTIME_SERVICES_CODE)
66 return pgprot_val(PAGE_KERNEL);
67
68 /* RWX */
69 return pgprot_val(PAGE_KERNEL_EXEC);
70 }
71
72 /* we will fill this structure from the stub, so don't put it in .bss */
73 struct screen_info screen_info __section(".data");
74 EXPORT_SYMBOL(screen_info);
75
efi_create_mapping(struct mm_struct * mm,efi_memory_desc_t * md)76 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
77 {
78 pteval_t prot_val = create_mapping_protection(md);
79 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
80 md->type == EFI_RUNTIME_SERVICES_DATA);
81
82 /*
83 * If this region is not aligned to the page size used by the OS, the
84 * mapping will be rounded outwards, and may end up sharing a page
85 * frame with an adjacent runtime memory region. Given that the page
86 * table descriptor covering the shared page will be rewritten when the
87 * adjacent region gets mapped, we must avoid block mappings here so we
88 * don't have to worry about splitting them when that happens.
89 */
90 if (region_is_misaligned(md))
91 page_mappings_only = true;
92
93 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
94 md->num_pages << EFI_PAGE_SHIFT,
95 __pgprot(prot_val | PTE_NG), page_mappings_only);
96 return 0;
97 }
98
set_permissions(pte_t * ptep,unsigned long addr,void * data)99 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
100 {
101 efi_memory_desc_t *md = data;
102 pte_t pte = READ_ONCE(*ptep);
103
104 if (md->attribute & EFI_MEMORY_RO)
105 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
106 if (md->attribute & EFI_MEMORY_XP)
107 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
108 set_pte(ptep, pte);
109 return 0;
110 }
111
efi_set_mapping_permissions(struct mm_struct * mm,efi_memory_desc_t * md)112 int __init efi_set_mapping_permissions(struct mm_struct *mm,
113 efi_memory_desc_t *md)
114 {
115 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
116 md->type != EFI_RUNTIME_SERVICES_DATA);
117
118 if (region_is_misaligned(md))
119 return 0;
120
121 /*
122 * Calling apply_to_page_range() is only safe on regions that are
123 * guaranteed to be mapped down to pages. Since we are only called
124 * for regions that have been mapped using efi_create_mapping() above
125 * (and this is checked by the generic Memory Attributes table parsing
126 * routines), there is no need to check that again here.
127 */
128 return apply_to_page_range(mm, md->virt_addr,
129 md->num_pages << EFI_PAGE_SHIFT,
130 set_permissions, md);
131 }
132
133 /*
134 * UpdateCapsule() depends on the system being shutdown via
135 * ResetSystem().
136 */
efi_poweroff_required(void)137 bool efi_poweroff_required(void)
138 {
139 return efi_enabled(EFI_RUNTIME_SERVICES);
140 }
141
efi_handle_corrupted_x18(efi_status_t s,const char * f)142 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
143 {
144 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
145 return s;
146 }
147
148 DEFINE_RAW_SPINLOCK(efi_rt_lock);
149
150 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
151
152 /* EFI requires 8 KiB of stack space for runtime services */
153 static_assert(THREAD_SIZE >= SZ_8K);
154
arm64_efi_rt_init(void)155 static int __init arm64_efi_rt_init(void)
156 {
157 void *p;
158
159 if (!efi_enabled(EFI_RUNTIME_SERVICES))
160 return 0;
161
162 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
163 NUMA_NO_NODE, &&l);
164 l: if (!p) {
165 pr_warn("Failed to allocate EFI runtime stack\n");
166 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
167 return -ENOMEM;
168 }
169
170 efi_rt_stack_top = p + THREAD_SIZE;
171 return 0;
172 }
173 core_initcall(arm64_efi_rt_init);
174