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 #include <asm/stacktrace.h>
15
region_is_misaligned(const efi_memory_desc_t * md)16 static bool region_is_misaligned(const efi_memory_desc_t *md)
17 {
18 if (PAGE_SIZE == EFI_PAGE_SIZE)
19 return false;
20 return !PAGE_ALIGNED(md->phys_addr) ||
21 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
22 }
23
24 /*
25 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
26 * executable, everything else can be mapped with the XN bits
27 * set. Also take the new (optional) RO/XP bits into account.
28 */
create_mapping_protection(efi_memory_desc_t * md)29 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
30 {
31 u64 attr = md->attribute;
32 u32 type = md->type;
33
34 if (type == EFI_MEMORY_MAPPED_IO)
35 return PROT_DEVICE_nGnRE;
36
37 if (region_is_misaligned(md)) {
38 static bool __initdata code_is_misaligned;
39
40 /*
41 * Regions that are not aligned to the OS page size cannot be
42 * mapped with strict permissions, as those might interfere
43 * with the permissions that are needed by the adjacent
44 * region's mapping. However, if we haven't encountered any
45 * misaligned runtime code regions so far, we can safely use
46 * non-executable permissions for non-code regions.
47 */
48 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
49
50 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
51 : pgprot_val(PAGE_KERNEL);
52 }
53
54 /* R-- */
55 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
56 (EFI_MEMORY_XP | EFI_MEMORY_RO))
57 return pgprot_val(PAGE_KERNEL_RO);
58
59 /* R-X */
60 if (attr & EFI_MEMORY_RO)
61 return pgprot_val(PAGE_KERNEL_ROX);
62
63 /* RW- */
64 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
65 EFI_MEMORY_XP) ||
66 type != EFI_RUNTIME_SERVICES_CODE)
67 return pgprot_val(PAGE_KERNEL);
68
69 /* RWX */
70 return pgprot_val(PAGE_KERNEL_EXEC);
71 }
72
73 /* we will fill this structure from the stub, so don't put it in .bss */
74 struct screen_info screen_info __section(".data");
75 EXPORT_SYMBOL(screen_info);
76
efi_create_mapping(struct mm_struct * mm,efi_memory_desc_t * md)77 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
78 {
79 pteval_t prot_val = create_mapping_protection(md);
80 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
81 md->type == EFI_RUNTIME_SERVICES_DATA);
82
83 /*
84 * If this region is not aligned to the page size used by the OS, the
85 * mapping will be rounded outwards, and may end up sharing a page
86 * frame with an adjacent runtime memory region. Given that the page
87 * table descriptor covering the shared page will be rewritten when the
88 * adjacent region gets mapped, we must avoid block mappings here so we
89 * don't have to worry about splitting them when that happens.
90 */
91 if (region_is_misaligned(md))
92 page_mappings_only = true;
93
94 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
95 md->num_pages << EFI_PAGE_SHIFT,
96 __pgprot(prot_val | PTE_NG), page_mappings_only);
97 return 0;
98 }
99
100 struct set_perm_data {
101 const efi_memory_desc_t *md;
102 bool has_bti;
103 };
104
set_permissions(pte_t * ptep,unsigned long addr,void * data)105 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
106 {
107 struct set_perm_data *spd = data;
108 const efi_memory_desc_t *md = spd->md;
109 pte_t pte = READ_ONCE(*ptep);
110
111 if (md->attribute & EFI_MEMORY_RO)
112 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
113 if (md->attribute & EFI_MEMORY_XP)
114 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
115 else if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) &&
116 system_supports_bti() && spd->has_bti)
117 pte = set_pte_bit(pte, __pgprot(PTE_GP));
118 set_pte(ptep, pte);
119 return 0;
120 }
121
efi_set_mapping_permissions(struct mm_struct * mm,efi_memory_desc_t * md,bool has_bti)122 int __init efi_set_mapping_permissions(struct mm_struct *mm,
123 efi_memory_desc_t *md,
124 bool has_bti)
125 {
126 struct set_perm_data data = { md, has_bti };
127
128 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
129 md->type != EFI_RUNTIME_SERVICES_DATA);
130
131 if (region_is_misaligned(md))
132 return 0;
133
134 /*
135 * Calling apply_to_page_range() is only safe on regions that are
136 * guaranteed to be mapped down to pages. Since we are only called
137 * for regions that have been mapped using efi_create_mapping() above
138 * (and this is checked by the generic Memory Attributes table parsing
139 * routines), there is no need to check that again here.
140 */
141 return apply_to_page_range(mm, md->virt_addr,
142 md->num_pages << EFI_PAGE_SHIFT,
143 set_permissions, &data);
144 }
145
146 /*
147 * UpdateCapsule() depends on the system being shutdown via
148 * ResetSystem().
149 */
efi_poweroff_required(void)150 bool efi_poweroff_required(void)
151 {
152 return efi_enabled(EFI_RUNTIME_SERVICES);
153 }
154
efi_handle_corrupted_x18(efi_status_t s,const char * f)155 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
156 {
157 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
158 return s;
159 }
160
161 DEFINE_RAW_SPINLOCK(efi_rt_lock);
162
163 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
164
165 asmlinkage efi_status_t __efi_rt_asm_recover(void);
166
efi_runtime_fixup_exception(struct pt_regs * regs,const char * msg)167 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
168 {
169 /* Check whether the exception occurred while running the firmware */
170 if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
171 return false;
172
173 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
174 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
175 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
176
177 regs->regs[0] = EFI_ABORTED;
178 regs->regs[30] = efi_rt_stack_top[-1];
179 regs->pc = (u64)__efi_rt_asm_recover;
180
181 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
182 regs->regs[18] = efi_rt_stack_top[-2];
183
184 return true;
185 }
186
187 /* EFI requires 8 KiB of stack space for runtime services */
188 static_assert(THREAD_SIZE >= SZ_8K);
189
arm64_efi_rt_init(void)190 static int __init arm64_efi_rt_init(void)
191 {
192 void *p;
193
194 if (!efi_enabled(EFI_RUNTIME_SERVICES))
195 return 0;
196
197 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
198 NUMA_NO_NODE, &&l);
199 l: if (!p) {
200 pr_warn("Failed to allocate EFI runtime stack\n");
201 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
202 return -ENOMEM;
203 }
204
205 efi_rt_stack_top = p + THREAD_SIZE;
206 return 0;
207 }
208 core_initcall(arm64_efi_rt_init);
209