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/screen_info.h>
13
14 #include <asm/efi.h>
15 #include <asm/stacktrace.h>
16
region_is_misaligned(const efi_memory_desc_t * md)17 static bool region_is_misaligned(const efi_memory_desc_t *md)
18 {
19 if (PAGE_SIZE == EFI_PAGE_SIZE)
20 return false;
21 return !PAGE_ALIGNED(md->phys_addr) ||
22 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
23 }
24
25 /*
26 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
27 * executable, everything else can be mapped with the XN bits
28 * set. Also take the new (optional) RO/XP bits into account.
29 */
create_mapping_protection(efi_memory_desc_t * md)30 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
31 {
32 u64 attr = md->attribute;
33 u32 type = md->type;
34
35 if (type == EFI_MEMORY_MAPPED_IO)
36 return PROT_DEVICE_nGnRE;
37
38 if (region_is_misaligned(md)) {
39 static bool __initdata code_is_misaligned;
40
41 /*
42 * Regions that are not aligned to the OS page size cannot be
43 * mapped with strict permissions, as those might interfere
44 * with the permissions that are needed by the adjacent
45 * region's mapping. However, if we haven't encountered any
46 * misaligned runtime code regions so far, we can safely use
47 * non-executable permissions for non-code regions.
48 */
49 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
50
51 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
52 : pgprot_val(PAGE_KERNEL);
53 }
54
55 /* R-- */
56 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
57 (EFI_MEMORY_XP | EFI_MEMORY_RO))
58 return pgprot_val(PAGE_KERNEL_RO);
59
60 /* R-X */
61 if (attr & EFI_MEMORY_RO)
62 return pgprot_val(PAGE_KERNEL_ROX);
63
64 /* RW- */
65 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
66 EFI_MEMORY_XP) ||
67 type != EFI_RUNTIME_SERVICES_CODE)
68 return pgprot_val(PAGE_KERNEL);
69
70 /* RWX */
71 return pgprot_val(PAGE_KERNEL_EXEC);
72 }
73
74 /* we will fill this structure from the stub, so don't put it in .bss */
75 struct screen_info screen_info __section(".data");
76 EXPORT_SYMBOL(screen_info);
77
efi_create_mapping(struct mm_struct * mm,efi_memory_desc_t * md)78 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
79 {
80 pteval_t prot_val = create_mapping_protection(md);
81 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
82 md->type == EFI_RUNTIME_SERVICES_DATA);
83
84 /*
85 * If this region is not aligned to the page size used by the OS, the
86 * mapping will be rounded outwards, and may end up sharing a page
87 * frame with an adjacent runtime memory region. Given that the page
88 * table descriptor covering the shared page will be rewritten when the
89 * adjacent region gets mapped, we must avoid block mappings here so we
90 * don't have to worry about splitting them when that happens.
91 */
92 if (region_is_misaligned(md))
93 page_mappings_only = true;
94
95 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
96 md->num_pages << EFI_PAGE_SHIFT,
97 __pgprot(prot_val | PTE_NG), page_mappings_only);
98 return 0;
99 }
100
101 struct set_perm_data {
102 const efi_memory_desc_t *md;
103 bool has_bti;
104 };
105
set_permissions(pte_t * ptep,unsigned long addr,void * data)106 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
107 {
108 struct set_perm_data *spd = data;
109 const efi_memory_desc_t *md = spd->md;
110 pte_t pte = READ_ONCE(*ptep);
111
112 if (md->attribute & EFI_MEMORY_RO)
113 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
114 if (md->attribute & EFI_MEMORY_XP)
115 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
116 else if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) &&
117 system_supports_bti() && spd->has_bti)
118 pte = set_pte_bit(pte, __pgprot(PTE_GP));
119 set_pte(ptep, pte);
120 return 0;
121 }
122
efi_set_mapping_permissions(struct mm_struct * mm,efi_memory_desc_t * md,bool has_bti)123 int __init efi_set_mapping_permissions(struct mm_struct *mm,
124 efi_memory_desc_t *md,
125 bool has_bti)
126 {
127 struct set_perm_data data = { md, has_bti };
128
129 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
130 md->type != EFI_RUNTIME_SERVICES_DATA);
131
132 if (region_is_misaligned(md))
133 return 0;
134
135 /*
136 * Calling apply_to_page_range() is only safe on regions that are
137 * guaranteed to be mapped down to pages. Since we are only called
138 * for regions that have been mapped using efi_create_mapping() above
139 * (and this is checked by the generic Memory Attributes table parsing
140 * routines), there is no need to check that again here.
141 */
142 return apply_to_page_range(mm, md->virt_addr,
143 md->num_pages << EFI_PAGE_SHIFT,
144 set_permissions, &data);
145 }
146
147 /*
148 * UpdateCapsule() depends on the system being shutdown via
149 * ResetSystem().
150 */
efi_poweroff_required(void)151 bool efi_poweroff_required(void)
152 {
153 return efi_enabled(EFI_RUNTIME_SERVICES);
154 }
155
efi_handle_corrupted_x18(efi_status_t s,const char * f)156 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
157 {
158 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
159 return s;
160 }
161
162 static DEFINE_RAW_SPINLOCK(efi_rt_lock);
163
arch_efi_call_virt_setup(void)164 void arch_efi_call_virt_setup(void)
165 {
166 efi_virtmap_load();
167 __efi_fpsimd_begin();
168 raw_spin_lock(&efi_rt_lock);
169 }
170
arch_efi_call_virt_teardown(void)171 void arch_efi_call_virt_teardown(void)
172 {
173 raw_spin_unlock(&efi_rt_lock);
174 __efi_fpsimd_end();
175 efi_virtmap_unload();
176 }
177
178 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
179
180 asmlinkage efi_status_t __efi_rt_asm_recover(void);
181
efi_runtime_fixup_exception(struct pt_regs * regs,const char * msg)182 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
183 {
184 /* Check whether the exception occurred while running the firmware */
185 if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
186 return false;
187
188 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
189 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
190 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
191
192 regs->regs[0] = EFI_ABORTED;
193 regs->regs[30] = efi_rt_stack_top[-1];
194 regs->pc = (u64)__efi_rt_asm_recover;
195
196 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
197 regs->regs[18] = efi_rt_stack_top[-2];
198
199 return true;
200 }
201
202 /* EFI requires 8 KiB of stack space for runtime services */
203 static_assert(THREAD_SIZE >= SZ_8K);
204
arm64_efi_rt_init(void)205 static int __init arm64_efi_rt_init(void)
206 {
207 void *p;
208
209 if (!efi_enabled(EFI_RUNTIME_SERVICES))
210 return 0;
211
212 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
213 NUMA_NO_NODE, &&l);
214 l: if (!p) {
215 pr_warn("Failed to allocate EFI runtime stack\n");
216 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
217 return -ENOMEM;
218 }
219
220 efi_rt_stack_top = p + THREAD_SIZE;
221 return 0;
222 }
223 core_initcall(arm64_efi_rt_init);
224