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
17static 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 */
30static __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
74int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
75{
76 pteval_t prot_val = create_mapping_protection(md);
77 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
78 md->type == EFI_RUNTIME_SERVICES_DATA);
79
80 /*
81 * If this region is not aligned to the page size used by the OS, the
82 * mapping will be rounded outwards, and may end up sharing a page
83 * frame with an adjacent runtime memory region. Given that the page
84 * table descriptor covering the shared page will be rewritten when the
85 * adjacent region gets mapped, we must avoid block mappings here so we
86 * don't have to worry about splitting them when that happens.
87 */
88 if (region_is_misaligned(md))
89 page_mappings_only = true;
90
91 create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
92 md->num_pages << EFI_PAGE_SHIFT,
93 __pgprot(prot_val | PTE_NG), page_mappings_only);
94 return 0;
95}
96
97struct set_perm_data {
98 const efi_memory_desc_t *md;
99 bool has_bti;
100};
101
102static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
103{
104 struct set_perm_data *spd = data;
105 const efi_memory_desc_t *md = spd->md;
106 pte_t pte = __ptep_get(ptep);
107
108 if (md->attribute & EFI_MEMORY_RO)
109 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
110 if (md->attribute & EFI_MEMORY_XP)
111 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
112 else if (system_supports_bti_kernel() && spd->has_bti)
113 pte = set_pte_bit(pte, __pgprot(PTE_GP));
114 __set_pte(ptep, pte);
115 return 0;
116}
117
118int __init efi_set_mapping_permissions(struct mm_struct *mm,
119 efi_memory_desc_t *md,
120 bool has_bti)
121{
122 struct set_perm_data data = { md, has_bti };
123
124 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
125 md->type != EFI_RUNTIME_SERVICES_DATA);
126
127 if (region_is_misaligned(md))
128 return 0;
129
130 /*
131 * Calling apply_to_page_range() is only safe on regions that are
132 * guaranteed to be mapped down to pages. Since we are only called
133 * for regions that have been mapped using efi_create_mapping() above
134 * (and this is checked by the generic Memory Attributes table parsing
135 * routines), there is no need to check that again here.
136 */
137 return apply_to_page_range(mm, address: md->virt_addr,
138 size: md->num_pages << EFI_PAGE_SHIFT,
139 fn: set_permissions, data: &data);
140}
141
142/*
143 * UpdateCapsule() depends on the system being shutdown via
144 * ResetSystem().
145 */
146bool efi_poweroff_required(void)
147{
148 return efi_enabled(EFI_RUNTIME_SERVICES);
149}
150
151asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
152{
153 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
154 return s;
155}
156
157static DEFINE_RAW_SPINLOCK(efi_rt_lock);
158
159void arch_efi_call_virt_setup(void)
160{
161 efi_virtmap_load();
162 __efi_fpsimd_begin();
163 raw_spin_lock(&efi_rt_lock);
164}
165
166void arch_efi_call_virt_teardown(void)
167{
168 raw_spin_unlock(&efi_rt_lock);
169 __efi_fpsimd_end();
170 efi_virtmap_unload();
171}
172
173asmlinkage u64 *efi_rt_stack_top __ro_after_init;
174
175asmlinkage efi_status_t __efi_rt_asm_recover(void);
176
177bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
178{
179 /* Check whether the exception occurred while running the firmware */
180 if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
181 return false;
182
183 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
184 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
185 clear_bit(EFI_RUNTIME_SERVICES, addr: &efi.flags);
186
187 regs->regs[0] = EFI_ABORTED;
188 regs->regs[30] = efi_rt_stack_top[-1];
189 regs->pc = (u64)__efi_rt_asm_recover;
190
191 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
192 regs->regs[18] = efi_rt_stack_top[-2];
193
194 return true;
195}
196
197/* EFI requires 8 KiB of stack space for runtime services */
198static_assert(THREAD_SIZE >= SZ_8K);
199
200static int __init arm64_efi_rt_init(void)
201{
202 void *p;
203
204 if (!efi_enabled(EFI_RUNTIME_SERVICES))
205 return 0;
206
207 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
208 NUMA_NO_NODE, &&l);
209l: if (!p) {
210 pr_warn("Failed to allocate EFI runtime stack\n");
211 clear_bit(EFI_RUNTIME_SERVICES, addr: &efi.flags);
212 return -ENOMEM;
213 }
214
215 efi_rt_stack_top = p + THREAD_SIZE;
216 return 0;
217}
218core_initcall(arm64_efi_rt_init);
219

source code of linux/arch/arm64/kernel/efi.c