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 15 /* 16 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be 17 * executable, everything else can be mapped with the XN bits 18 * set. Also take the new (optional) RO/XP bits into account. 19 */ 20 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md) 21 { 22 u64 attr = md->attribute; 23 u32 type = md->type; 24 25 if (type == EFI_MEMORY_MAPPED_IO) 26 return PROT_DEVICE_nGnRE; 27 28 if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr), 29 "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?")) 30 /* 31 * If the region is not aligned to the page size of the OS, we 32 * can not use strict permissions, since that would also affect 33 * the mapping attributes of the adjacent regions. 34 */ 35 return pgprot_val(PAGE_KERNEL_EXEC); 36 37 /* R-- */ 38 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) == 39 (EFI_MEMORY_XP | EFI_MEMORY_RO)) 40 return pgprot_val(PAGE_KERNEL_RO); 41 42 /* R-X */ 43 if (attr & EFI_MEMORY_RO) 44 return pgprot_val(PAGE_KERNEL_ROX); 45 46 /* RW- */ 47 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) == 48 EFI_MEMORY_XP) || 49 type != EFI_RUNTIME_SERVICES_CODE) 50 return pgprot_val(PAGE_KERNEL); 51 52 /* RWX */ 53 return pgprot_val(PAGE_KERNEL_EXEC); 54 } 55 56 /* we will fill this structure from the stub, so don't put it in .bss */ 57 struct screen_info screen_info __section(".data"); 58 EXPORT_SYMBOL(screen_info); 59 60 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) 61 { 62 pteval_t prot_val = create_mapping_protection(md); 63 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE || 64 md->type == EFI_RUNTIME_SERVICES_DATA); 65 66 if (!PAGE_ALIGNED(md->phys_addr) || 67 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) { 68 /* 69 * If the end address of this region is not aligned to page 70 * size, the mapping is rounded up, and may end up sharing a 71 * page frame with the next UEFI memory region. If we create 72 * a block entry now, we may need to split it again when mapping 73 * the next region, and support for that is going to be removed 74 * from the MMU routines. So avoid block mappings altogether in 75 * that case. 76 */ 77 page_mappings_only = true; 78 } 79 80 create_pgd_mapping(mm, md->phys_addr, md->virt_addr, 81 md->num_pages << EFI_PAGE_SHIFT, 82 __pgprot(prot_val | PTE_NG), page_mappings_only); 83 return 0; 84 } 85 86 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) 87 { 88 efi_memory_desc_t *md = data; 89 pte_t pte = READ_ONCE(*ptep); 90 91 if (md->attribute & EFI_MEMORY_RO) 92 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); 93 if (md->attribute & EFI_MEMORY_XP) 94 pte = set_pte_bit(pte, __pgprot(PTE_PXN)); 95 set_pte(ptep, pte); 96 return 0; 97 } 98 99 int __init efi_set_mapping_permissions(struct mm_struct *mm, 100 efi_memory_desc_t *md) 101 { 102 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE && 103 md->type != EFI_RUNTIME_SERVICES_DATA); 104 105 /* 106 * Calling apply_to_page_range() is only safe on regions that are 107 * guaranteed to be mapped down to pages. Since we are only called 108 * for regions that have been mapped using efi_create_mapping() above 109 * (and this is checked by the generic Memory Attributes table parsing 110 * routines), there is no need to check that again here. 111 */ 112 return apply_to_page_range(mm, md->virt_addr, 113 md->num_pages << EFI_PAGE_SHIFT, 114 set_permissions, md); 115 } 116 117 /* 118 * UpdateCapsule() depends on the system being shutdown via 119 * ResetSystem(). 120 */ 121 bool efi_poweroff_required(void) 122 { 123 return efi_enabled(EFI_RUNTIME_SERVICES); 124 } 125 126 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) 127 { 128 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f); 129 return s; 130 } 131