1 // SPDX-License-Identifier: GPL-2.0-only
3 * Extensible Firmware Interface
5 * Based on Extensible Firmware Interface Specification version 2.4
7 * Copyright (C) 2013, 2014 Linaro Ltd.
10 #include <linux/efi.h>
11 #include <linux/init.h>
15 static bool region_is_misaligned(const efi_memory_desc_t *md)
17 if (PAGE_SIZE == EFI_PAGE_SIZE)
19 return !PAGE_ALIGNED(md->phys_addr) ||
20 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
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.
28 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
30 u64 attr = md->attribute;
33 if (type == EFI_MEMORY_MAPPED_IO)
34 return PROT_DEVICE_nGnRE;
36 if (region_is_misaligned(md)) {
37 static bool __initdata code_is_misaligned;
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.
47 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
49 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
50 : pgprot_val(PAGE_KERNEL);
54 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
55 (EFI_MEMORY_XP | EFI_MEMORY_RO))
56 return pgprot_val(PAGE_KERNEL_RO);
59 if (attr & EFI_MEMORY_RO)
60 return pgprot_val(PAGE_KERNEL_ROX);
63 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
65 type != EFI_RUNTIME_SERVICES_CODE)
66 return pgprot_val(PAGE_KERNEL);
69 return pgprot_val(PAGE_KERNEL_EXEC);
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 EXPORT_SYMBOL(screen_info);
76 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
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);
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.
90 if (region_is_misaligned(md))
91 page_mappings_only = true;
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);
99 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
101 efi_memory_desc_t *md = data;
102 pte_t pte = READ_ONCE(*ptep);
104 if (md->attribute & EFI_MEMORY_RO)
105 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
106 if (md->attribute & EFI_MEMORY_XP)
107 pte = set_pte_bit(pte, __pgprot(PTE_PXN));
112 int __init efi_set_mapping_permissions(struct mm_struct *mm,
113 efi_memory_desc_t *md)
115 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
116 md->type != EFI_RUNTIME_SERVICES_DATA);
118 if (region_is_misaligned(md))
122 * Calling apply_to_page_range() is only safe on regions that are
123 * guaranteed to be mapped down to pages. Since we are only called
124 * for regions that have been mapped using efi_create_mapping() above
125 * (and this is checked by the generic Memory Attributes table parsing
126 * routines), there is no need to check that again here.
128 return apply_to_page_range(mm, md->virt_addr,
129 md->num_pages << EFI_PAGE_SHIFT,
130 set_permissions, md);
134 * UpdateCapsule() depends on the system being shutdown via
137 bool efi_poweroff_required(void)
139 return efi_enabled(EFI_RUNTIME_SERVICES);
142 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
144 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
148 DEFINE_SPINLOCK(efi_rt_lock);
150 asmlinkage u64 *efi_rt_stack_top __ro_after_init;
152 asmlinkage efi_status_t __efi_rt_asm_recover(void);
154 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
156 /* Check whether the exception occurred while running the firmware */
157 if (current_work() != &efi_rts_work.work || regs->pc >= TASK_SIZE_64)
160 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
161 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
162 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
164 regs->regs[0] = EFI_ABORTED;
165 regs->regs[30] = efi_rt_stack_top[-1];
166 regs->pc = (u64)__efi_rt_asm_recover;
168 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
169 regs->regs[18] = efi_rt_stack_top[-2];
174 /* EFI requires 8 KiB of stack space for runtime services */
175 static_assert(THREAD_SIZE >= SZ_8K);
177 static int __init arm64_efi_rt_init(void)
181 if (!efi_enabled(EFI_RUNTIME_SERVICES))
184 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
187 pr_warn("Failed to allocate EFI runtime stack\n");
188 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
192 efi_rt_stack_top = p + THREAD_SIZE;
195 core_initcall(arm64_efi_rt_init);