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/kthread.h> 14 #include <linux/screen_info.h> 15 #include <linux/vmalloc.h> 16 17 #include <asm/efi.h> 18 #include <asm/stacktrace.h> 19 #include <asm/vmap_stack.h> 20 21 static bool region_is_misaligned(const efi_memory_desc_t *md) 22 { 23 if (PAGE_SIZE == EFI_PAGE_SIZE) 24 return false; 25 return !PAGE_ALIGNED(md->phys_addr) || 26 !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT); 27 } 28 29 /* 30 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be 31 * executable, everything else can be mapped with the XN bits 32 * set. Also take the new (optional) RO/XP bits into account. 33 */ 34 static __init ptval_t create_mapping_protection(efi_memory_desc_t *md) 35 { 36 u64 attr = md->attribute; 37 u32 type = md->type; 38 39 if (type == EFI_MEMORY_MAPPED_IO) { 40 pgprot_t prot = __pgprot(PROT_DEVICE_nGnRE); 41 42 if (arm64_is_protected_mmio(md->phys_addr, 43 md->num_pages << EFI_PAGE_SHIFT)) 44 prot = pgprot_encrypted(prot); 45 else 46 prot = pgprot_decrypted(prot); 47 return pgprot_val(prot); 48 } 49 50 if (region_is_misaligned(md)) { 51 static bool __initdata code_is_misaligned; 52 53 /* 54 * Regions that are not aligned to the OS page size cannot be 55 * mapped with strict permissions, as those might interfere 56 * with the permissions that are needed by the adjacent 57 * region's mapping. However, if we haven't encountered any 58 * misaligned runtime code regions so far, we can safely use 59 * non-executable permissions for non-code regions. 60 */ 61 code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE); 62 63 return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC) 64 : pgprot_val(PAGE_KERNEL); 65 } 66 67 /* R-- */ 68 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) == 69 (EFI_MEMORY_XP | EFI_MEMORY_RO)) 70 return pgprot_val(PAGE_KERNEL_RO); 71 72 /* R-X */ 73 if (attr & EFI_MEMORY_RO) 74 return pgprot_val(PAGE_KERNEL_ROX); 75 76 /* RW- */ 77 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) == 78 EFI_MEMORY_XP) || 79 type != EFI_RUNTIME_SERVICES_CODE) 80 return pgprot_val(PAGE_KERNEL); 81 82 /* RWX */ 83 return pgprot_val(PAGE_KERNEL_EXEC); 84 } 85 86 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) 87 { 88 ptval_t prot_val = create_mapping_protection(md); 89 bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE || 90 md->type == EFI_RUNTIME_SERVICES_DATA); 91 92 /* 93 * If this region is not aligned to the page size used by the OS, the 94 * mapping will be rounded outwards, and may end up sharing a page 95 * frame with an adjacent runtime memory region. Given that the page 96 * table descriptor covering the shared page will be rewritten when the 97 * adjacent region gets mapped, we must avoid block mappings here so we 98 * don't have to worry about splitting them when that happens. 99 */ 100 if (region_is_misaligned(md)) 101 page_mappings_only = true; 102 103 create_pgd_mapping(mm, md->phys_addr, md->virt_addr, 104 md->num_pages << EFI_PAGE_SHIFT, 105 __pgprot(prot_val | PTE_NG), page_mappings_only); 106 return 0; 107 } 108 109 struct set_perm_data { 110 const efi_memory_desc_t *md; 111 bool has_bti; 112 }; 113 114 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) 115 { 116 struct set_perm_data *spd = data; 117 const efi_memory_desc_t *md = spd->md; 118 pte_t pte = __ptep_get(ptep); 119 120 /* 121 * Clear PTE_WRITE as well: it doubles as the DBM bit, and leaving it 122 * set would permit the hardware to make the mapping writable again 123 * when TCR_EL1.HD is set. 124 */ 125 if (md->attribute & EFI_MEMORY_RO) 126 pte = set_pte_bit(clear_pte_bit(pte, __pgprot(PTE_WRITE)), 127 __pgprot(PTE_RDONLY)); 128 if (md->attribute & EFI_MEMORY_XP) 129 pte = set_pte_bit(pte, __pgprot(PTE_PXN)); 130 else if (system_supports_bti_kernel() && spd->has_bti) 131 pte = set_pte_bit(pte, __pgprot(PTE_GP)); 132 __set_pte(ptep, pte); 133 return 0; 134 } 135 136 int __init efi_set_mapping_permissions(struct mm_struct *mm, 137 efi_memory_desc_t *md, 138 bool has_bti) 139 { 140 struct set_perm_data data = { md, has_bti }; 141 142 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE && 143 md->type != EFI_RUNTIME_SERVICES_DATA); 144 145 if (region_is_misaligned(md)) 146 return 0; 147 148 /* 149 * Calling apply_to_page_range() is only safe on regions that are 150 * guaranteed to be mapped down to pages. Since we are only called 151 * for regions that have been mapped using efi_create_mapping() above 152 * (and this is checked by the generic Memory Attributes table parsing 153 * routines), there is no need to check that again here. 154 */ 155 return apply_to_page_range(mm, md->virt_addr, 156 md->num_pages << EFI_PAGE_SHIFT, 157 set_permissions, &data); 158 } 159 160 /* 161 * UpdateCapsule() depends on the system being shutdown via 162 * ResetSystem(). 163 */ 164 bool efi_poweroff_required(void) 165 { 166 return efi_enabled(EFI_RUNTIME_SERVICES); 167 } 168 169 asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) 170 { 171 pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f); 172 return s; 173 } 174 175 void arch_efi_call_virt_setup(void) 176 { 177 efi_runtime_assert_lock_held(); 178 179 if (preemptible() && (current->flags & PF_KTHREAD)) { 180 /* 181 * Disable migration to ensure that a preempted EFI runtime 182 * service call will be resumed on the same CPU. This avoids 183 * potential issues with EFI runtime calls that are preempted 184 * while polling for an asynchronous completion of a secure 185 * firmware call, which may not permit the CPU to change. 186 */ 187 migrate_disable(); 188 kthread_use_mm(&efi_mm); 189 } else { 190 efi_virtmap_load(); 191 } 192 193 __efi_fpsimd_begin(); 194 195 /* 196 * Enable access to the valid TTBR0_EL1 and invoke the errata 197 * workaround directly since there is no return from exception when 198 * invoking the EFI run-time services. 199 */ 200 uaccess_ttbr0_enable(); 201 post_ttbr_update_workaround(); 202 } 203 204 void arch_efi_call_virt_teardown(void) 205 { 206 __efi_fpsimd_end(); 207 208 /* 209 * Defer the switch to the current thread's TTBR0_EL1 until 210 * uaccess_enable(). Do so before efi_virtmap_unload() updates the 211 * saved TTBR0 value, so the userland page tables are not activated 212 * inadvertently over the back of an exception. 213 */ 214 uaccess_ttbr0_disable(); 215 216 if (preemptible() && (current->flags & PF_KTHREAD)) { 217 kthread_unuse_mm(&efi_mm); 218 migrate_enable(); 219 } else { 220 efi_virtmap_unload(); 221 } 222 } 223 224 asmlinkage u64 *efi_rt_stack_top __ro_after_init; 225 226 asmlinkage efi_status_t __efi_rt_asm_recover(void); 227 228 bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg) 229 { 230 /* Check whether the exception occurred while running the firmware */ 231 if (!current_in_efi() || regs->pc >= TASK_SIZE_64) 232 return false; 233 234 pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg); 235 add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK); 236 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 237 238 regs->regs[0] = EFI_ABORTED; 239 regs->regs[30] = efi_rt_stack_top[-1]; 240 regs->pc = (u64)__efi_rt_asm_recover; 241 242 if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) 243 regs->regs[18] = efi_rt_stack_top[-2]; 244 245 return true; 246 } 247 248 /* EFI requires 8 KiB of stack space for runtime services */ 249 static_assert(THREAD_SIZE >= SZ_8K); 250 251 static int __init arm64_efi_rt_init(void) 252 { 253 void *p; 254 255 if (!efi_enabled(EFI_RUNTIME_SERVICES)) 256 return 0; 257 258 p = arch_alloc_vmap_stack(THREAD_SIZE, NUMA_NO_NODE); 259 if (!p) { 260 pr_warn("Failed to allocate EFI runtime stack\n"); 261 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 262 return -ENOMEM; 263 } 264 265 kmemleak_not_leak(p); 266 efi_rt_stack_top = p + THREAD_SIZE; 267 return 0; 268 } 269 core_initcall(arm64_efi_rt_init); 270