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