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
efi_create_mapping(struct mm_struct * mm,efi_memory_desc_t * md)75 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
76 {
77 pteval_t prot_val = create_mapping_protection(md);
78 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
79 md->type == EFI_RUNTIME_SERVICES_DATA);
80
81 /*
82 * If this region is not aligned to the page size used by the OS, the
83 * mapping will be rounded outwards, and may end up sharing a page
84 * frame with an adjacent runtime memory region. Given that the page
85 * table descriptor covering the shared page will be rewritten when the
86 * adjacent region gets mapped, we must avoid block mappings here so we
87 * don't have to worry about splitting them when that happens.
88 */
89 if (region_is_misaligned(md))
90 page_mappings_only = true;
91
92 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
93 md->num_pages << EFI_PAGE_SHIFT,
94 __pgprot(prot_val | PTE_NG), page_mappings_only);
95 return 0;
96 }
97
set_permissions(pte_t * ptep,unsigned long addr,void * data)98 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
99 {
100 efi_memory_desc_t *md = data;
101 pte_t pte = READ_ONCE(*ptep);
102
103 if (md->attribute & EFI_MEMORY_RO)
104 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
105 if (md->attribute & EFI_MEMORY_XP)
106 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
107 set_pte(ptep, pte);
108 return 0;
109 }
110
efi_set_mapping_permissions(struct mm_struct * mm,efi_memory_desc_t * md)111 int __init efi_set_mapping_permissions(struct mm_struct *mm,
112 efi_memory_desc_t *md)
113 {
114 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
115 md->type != EFI_RUNTIME_SERVICES_DATA);
116
117 if (region_is_misaligned(md))
118 return 0;
119
120 /*
121 * Calling apply_to_page_range() is only safe on regions that are
122 * guaranteed to be mapped down to pages. Since we are only called
123 * for regions that have been mapped using efi_create_mapping() above
124 * (and this is checked by the generic Memory Attributes table parsing
125 * routines), there is no need to check that again here.
126 */
127 return apply_to_page_range(mm, md->virt_addr,
128 md->num_pages << EFI_PAGE_SHIFT,
129 set_permissions, md);
130 }
131
132 /*
133 * UpdateCapsule() depends on the system being shutdown via
134 * ResetSystem().
135 */
efi_poweroff_required(void)136 bool efi_poweroff_required(void)
137 {
138 return efi_enabled(EFI_RUNTIME_SERVICES);
139 }
140
efi_handle_corrupted_x18(efi_status_t s,const char * f)141 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
142 {
143 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
144 return s;
145 }
146
147 DEFINE_RAW_SPINLOCK(efi_rt_lock);
148
149 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
150
151 /* EFI requires 8 KiB of stack space for runtime services */
152 static_assert(THREAD_SIZE >= SZ_8K);
153
arm64_efi_rt_init(void)154 static int __init arm64_efi_rt_init(void)
155 {
156 void *p;
157
158 if (!efi_enabled(EFI_RUNTIME_SERVICES))
159 return 0;
160
161 p = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, VMALLOC_START,
162 VMALLOC_END, GFP_KERNEL, PAGE_KERNEL, 0,
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