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/kmemleak.h> 13 #include <linux/screen_info.h> 14 #include <linux/vmalloc.h> 15 16 #include <asm/efi.h> 17 #include <asm/stacktrace.h> 18 19 static bool region_is_misaligned(const efi_memory_desc_t *md) 20 { 21 if (PAGE_SIZE == EFI_PAGE_SIZE) 22 return false; 23 return !PAGE_ALIGNED(md->phys_addr) || 24 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT); 25 } 26 27 /* 28 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be 29 * executable, everything else can be mapped with the XN bits 30 * set. Also take the new (optional) RO/XP bits into account. 31 */ 32 static __init pteval_t create_mapping_protection(efi_memory_desc_t *md) 33 { 34 u64 attr = md->attribute; 35 u32 type = md->type; 36 37 if (type == EFI_MEMORY_MAPPED_IO) 38 return PROT_DEVICE_nGnRE; 39 40 if (region_is_misaligned(md)) { 41 static bool __initdata code_is_misaligned; 42 43 /* 44 * Regions that are not aligned to the OS page size cannot be 45 * mapped with strict permissions, as those might interfere 46 * with the permissions that are needed by the adjacent 47 * region's mapping. However, if we haven't encountered any 48 * misaligned runtime code regions so far, we can safely use 49 * non-executable permissions for non-code regions. 50 */ 51 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE); 52 53 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC) 54 : pgprot_val(PAGE_KERNEL); 55 } 56 57 /* R-- */ 58 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) == 59 (EFI_MEMORY_XP | EFI_MEMORY_RO)) 60 return pgprot_val(PAGE_KERNEL_RO); 61 62 /* R-X */ 63 if (attr & EFI_MEMORY_RO) 64 return pgprot_val(PAGE_KERNEL_ROX); 65 66 /* RW- */ 67 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) == 68 EFI_MEMORY_XP) || 69 type != EFI_RUNTIME_SERVICES_CODE) 70 return pgprot_val(PAGE_KERNEL); 71 72 /* RWX */ 73 return pgprot_val(PAGE_KERNEL_EXEC); 74 } 75 76 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) 77 { 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); 81 82 /* 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. 89 */ 90 if (region_is_misaligned(md)) 91 page_mappings_only = true; 92 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); 96 return 0; 97 } 98 99 struct set_perm_data { 100 const efi_memory_desc_t *md; 101 bool has_bti; 102 }; 103 104 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) 105 { 106 struct set_perm_data *spd = data; 107 const efi_memory_desc_t *md = spd->md; 108 pte_t pte = __ptep_get(ptep); 109 110 if (md->attribute & EFI_MEMORY_RO) 111 pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); 112 if (md->attribute & EFI_MEMORY_XP) 113 pte = set_pte_bit(pte, __pgprot(PTE_PXN)); 114 else if (system_supports_bti_kernel() && spd->has_bti) 115 pte = set_pte_bit(pte, __pgprot(PTE_GP)); 116 __set_pte(ptep, pte); 117 return 0; 118 } 119 120 int __init efi_set_mapping_permissions(struct mm_struct *mm, 121 efi_memory_desc_t *md, 122 bool has_bti) 123 { 124 struct set_perm_data data = { md, has_bti }; 125 126 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE && 127 md->type != EFI_RUNTIME_SERVICES_DATA); 128 129 if (region_is_misaligned(md)) 130 return 0; 131 132 /* 133 * Calling apply_to_page_range() is only safe on regions that are 134 * guaranteed to be mapped down to pages. Since we are only called 135 * for regions that have been mapped using efi_create_mapping() above 136 * (and this is checked by the generic Memory Attributes table parsing 137 * routines), there is no need to check that again here. 138 */ 139 return apply_to_page_range(mm, md->virt_addr, 140 md->num_pages << EFI_PAGE_SHIFT, 141 set_permissions, &data); 142 } 143 144 /* 145 * UpdateCapsule() depends on the system being shutdown via 146 * ResetSystem(). 147 */ 148 bool efi_poweroff_required(void) 149 { 150 return efi_enabled(EFI_RUNTIME_SERVICES); 151 } 152 153 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) 154 { 155 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f); 156 return s; 157 } 158 159 static DEFINE_RAW_SPINLOCK(efi_rt_lock); 160 161 void arch_efi_call_virt_setup(void) 162 { 163 efi_virtmap_load(); 164 __efi_fpsimd_begin(); 165 raw_spin_lock(&efi_rt_lock); 166 } 167 168 void arch_efi_call_virt_teardown(void) 169 { 170 raw_spin_unlock(&efi_rt_lock); 171 __efi_fpsimd_end(); 172 efi_virtmap_unload(); 173 } 174 175 asmlinkage u64 *efi_rt_stack_top __ro_after_init; 176 177 asmlinkage efi_status_t __efi_rt_asm_recover(void); 178 179 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg) 180 { 181 /* Check whether the exception occurred while running the firmware */ 182 if (!current_in_efi() || regs->pc >= TASK_SIZE_64) 183 return false; 184 185 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg); 186 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK); 187 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 188 189 regs->regs[0] = EFI_ABORTED; 190 regs->regs[30] = efi_rt_stack_top[-1]; 191 regs->pc = (u64)__efi_rt_asm_recover; 192 193 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) 194 regs->regs[18] = efi_rt_stack_top[-2]; 195 196 return true; 197 } 198 199 /* EFI requires 8 KiB of stack space for runtime services */ 200 static_assert(THREAD_SIZE >= SZ_8K); 201 202 static int __init arm64_efi_rt_init(void) 203 { 204 void *p; 205 206 if (!efi_enabled(EFI_RUNTIME_SERVICES)) 207 return 0; 208 209 p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL, 210 NUMA_NO_NODE, &&l); 211 l: if (!p) { 212 pr_warn("Failed to allocate EFI runtime stack\n"); 213 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 214 return -ENOMEM; 215 } 216 217 kmemleak_not_leak(p); 218 efi_rt_stack_top = p + THREAD_SIZE; 219 return 0; 220 } 221 core_initcall(arm64_efi_rt_init); 222