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 #include <linux/kmemleak.h>
13 #include <linux/screen_info.h>
14 #include <linux/vmalloc.h>
15
16 #include <asm/efi.h>
17 #include <asm/stacktrace.h>
18
19 static bool region_is_misaligned(const efi_memory_desc_t *md)
20 {
21 if (PAGE_SIZE == EFI_PAGE_SIZE)
22 return false;
23 return !PAGE_ALIGNED(md->phys_addr) ||
24 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
25 }
26
27 /*
28 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
29 * executable, everything else can be mapped with the XN bits
30 * set. Also take the new (optional) RO/XP bits into account.
31 */
32 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
33 {
34 u64 attr = md->attribute;
35 u32 type = md->type;
36
37 if (type == EFI_MEMORY_MAPPED_IO)
38 return PROT_DEVICE_nGnRE;
39
40 if (region_is_misaligned(md)) {
41 static bool __initdata code_is_misaligned;
42
43 /*
44 * Regions that are not aligned to the OS page size cannot be
45 * mapped with strict permissions, as those might interfere
46 * with the permissions that are needed by the adjacent
47 * region's mapping. However, if we haven't encountered any
48 * misaligned runtime code regions so far, we can safely use
49 * non-executable permissions for non-code regions.
50 */
51 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
52
53 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
54 : pgprot_val(PAGE_KERNEL);
55 }
56
57 /* R-- */
58 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
59 (EFI_MEMORY_XP | EFI_MEMORY_RO))
60 return pgprot_val(PAGE_KERNEL_RO);
61
62 /* R-X */
63 if (attr & EFI_MEMORY_RO)
64 return pgprot_val(PAGE_KERNEL_ROX);
65
66 /* RW- */
67 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
68 EFI_MEMORY_XP) ||
69 type != EFI_RUNTIME_SERVICES_CODE)
70 return pgprot_val(PAGE_KERNEL);
71
72 /* RWX */
73 return pgprot_val(PAGE_KERNEL_EXEC);
74 }
75
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
99 struct set_perm_data {
100 const efi_memory_desc_t *md;
101 bool has_bti;
102 };
103
104 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
105 {
106 struct set_perm_data *spd = data;
107 const efi_memory_desc_t *md = spd->md;
108 pte_t pte = __ptep_get(ptep);
109
110 if (md->attribute & EFI_MEMORY_RO)
111 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
112 if (md->attribute & EFI_MEMORY_XP)
113 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
114 else if (system_supports_bti_kernel() && spd->has_bti)
115 pte = set_pte_bit(pte, __pgprot(PTE_GP));
116 __set_pte(ptep, pte);
117 return 0;
118 }
119
120 int __init efi_set_mapping_permissions(struct mm_struct *mm,
121 efi_memory_desc_t *md,
122 bool has_bti)
123 {
124 struct set_perm_data data = { md, has_bti };
125
126 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
127 md->type != EFI_RUNTIME_SERVICES_DATA);
128
129 if (region_is_misaligned(md))
130 return 0;
131
132 /*
133 * Calling apply_to_page_range() is only safe on regions that are
134 * guaranteed to be mapped down to pages. Since we are only called
135 * for regions that have been mapped using efi_create_mapping() above
136 * (and this is checked by the generic Memory Attributes table parsing
137 * routines), there is no need to check that again here.
138 */
139 return apply_to_page_range(mm, md->virt_addr,
140 md->num_pages << EFI_PAGE_SHIFT,
141 set_permissions, &data);
142 }
143
144 /*
145 * UpdateCapsule() depends on the system being shutdown via
146 * ResetSystem().
147 */
148 bool efi_poweroff_required(void)
149 {
150 return efi_enabled(EFI_RUNTIME_SERVICES);
151 }
152
153 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
154 {
155 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
156 return s;
157 }
158
159 static DEFINE_RAW_SPINLOCK(efi_rt_lock);
160
161 void arch_efi_call_virt_setup(void)
162 {
163 efi_virtmap_load();
164 __efi_fpsimd_begin();
165 raw_spin_lock(&efi_rt_lock);
166 }
167
168 void arch_efi_call_virt_teardown(void)
169 {
170 raw_spin_unlock(&efi_rt_lock);
171 __efi_fpsimd_end();
172 efi_virtmap_unload();
173 }
174
175 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
176
177 asmlinkage efi_status_t __efi_rt_asm_recover(void);
178
179 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
180 {
181 /* Check whether the exception occurred while running the firmware */
182 if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
183 return false;
184
185 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
186 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
187 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
188
189 regs->regs[0] = EFI_ABORTED;
190 regs->regs[30] = efi_rt_stack_top[-1];
191 regs->pc = (u64)__efi_rt_asm_recover;
192
193 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
194 regs->regs[18] = efi_rt_stack_top[-2];
195
196 return true;
197 }
198
199 /* EFI requires 8 KiB of stack space for runtime services */
200 static_assert(THREAD_SIZE >= SZ_8K);
201
202 static int __init arm64_efi_rt_init(void)
203 {
204 void *p;
205
206 if (!efi_enabled(EFI_RUNTIME_SERVICES))
207 return 0;
208
209 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
210 NUMA_NO_NODE, &&l);
211 l: if (!p) {
212 pr_warn("Failed to allocate EFI runtime stack\n");
213 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
214 return -ENOMEM;
215 }
216
217 kmemleak_not_leak(p);
218 efi_rt_stack_top = p + THREAD_SIZE;
219 return 0;
220 }
221 core_initcall(arm64_efi_rt_init);
222
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