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 59 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) 60 { 61 pteval_t prot_val = create_mapping_protection(md); 62 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE || 63 md->type == EFI_RUNTIME_SERVICES_DATA); 64 65 if (!PAGE_ALIGNED(md->phys_addr) || 66 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) { 67 /* 68 * If the end address of this region is not aligned to page 69 * size, the mapping is rounded up, and may end up sharing a 70 * page frame with the next UEFI memory region. If we create 71 * a block entry now, we may need to split it again when mapping 72 * the next region, and support for that is going to be removed 73 * from the MMU routines. So avoid block mappings altogether in 74 * that case. 75 */ 76 page_mappings_only = true; 77 } 78 79 create_pgd_mapping(mm, md->phys_addr, md->virt_addr, 80 md->num_pages << EFI_PAGE_SHIFT, 81 __pgprot(prot_val | PTE_NG), page_mappings_only); 82 return 0; 83 } 84 85 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) 86 { 87 efi_memory_desc_t *md = data; 88 pte_t pte = READ_ONCE(*ptep); 89 90 if (md->attribute & EFI_MEMORY_RO) 91 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); 92 if (md->attribute & EFI_MEMORY_XP) 93 pte = set_pte_bit(pte, __pgprot(PTE_PXN)); 94 set_pte(ptep, pte); 95 return 0; 96 } 97 98 int __init efi_set_mapping_permissions(struct mm_struct *mm, 99 efi_memory_desc_t *md) 100 { 101 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE && 102 md->type != EFI_RUNTIME_SERVICES_DATA); 103 104 /* 105 * Calling apply_to_page_range() is only safe on regions that are 106 * guaranteed to be mapped down to pages. Since we are only called 107 * for regions that have been mapped using efi_create_mapping() above 108 * (and this is checked by the generic Memory Attributes table parsing 109 * routines), there is no need to check that again here. 110 */ 111 return apply_to_page_range(mm, md->virt_addr, 112 md->num_pages << EFI_PAGE_SHIFT, 113 set_permissions, md); 114 } 115 116 /* 117 * UpdateCapsule() depends on the system being shutdown via 118 * ResetSystem(). 119 */ 120 bool efi_poweroff_required(void) 121 { 122 return efi_enabled(EFI_RUNTIME_SERVICES); 123 } 124 125 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) 126 { 127 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f); 128 return s; 129 } 130