1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Helpers for early access to EFI configuration table. 4 * 5 * Originally derived from arch/x86/boot/compressed/acpi.c 6 */ 7 8 #include "misc.h" 9 10 /** 11 * efi_get_type - Given a pointer to boot_params, determine the type of EFI environment. 12 * 13 * @bp: pointer to boot_params 14 * 15 * Return: EFI_TYPE_{32,64} for valid EFI environments, EFI_TYPE_NONE otherwise. 16 */ 17 enum efi_type efi_get_type(struct boot_params *bp) 18 { 19 struct efi_info *ei; 20 enum efi_type et; 21 const char *sig; 22 23 ei = &bp->efi_info; 24 sig = (char *)&ei->efi_loader_signature; 25 26 if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) { 27 et = EFI_TYPE_64; 28 } else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) { 29 et = EFI_TYPE_32; 30 } else { 31 debug_putstr("No EFI environment detected.\n"); 32 et = EFI_TYPE_NONE; 33 } 34 35 #ifndef CONFIG_X86_64 36 /* 37 * Existing callers like acpi.c treat this case as an indicator to 38 * fall-through to non-EFI, rather than an error, so maintain that 39 * functionality here as well. 40 */ 41 if (ei->efi_systab_hi || ei->efi_memmap_hi) { 42 debug_putstr("EFI system table is located above 4GB and cannot be accessed.\n"); 43 et = EFI_TYPE_NONE; 44 } 45 #endif 46 47 return et; 48 } 49 50 /** 51 * efi_get_system_table - Given a pointer to boot_params, retrieve the physical address 52 * of the EFI system table. 53 * 54 * @bp: pointer to boot_params 55 * 56 * Return: EFI system table address on success. On error, return 0. 57 */ 58 unsigned long efi_get_system_table(struct boot_params *bp) 59 { 60 unsigned long sys_tbl_pa; 61 struct efi_info *ei; 62 enum efi_type et; 63 64 /* Get systab from boot params. */ 65 ei = &bp->efi_info; 66 #ifdef CONFIG_X86_64 67 sys_tbl_pa = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32); 68 #else 69 sys_tbl_pa = ei->efi_systab; 70 #endif 71 if (!sys_tbl_pa) { 72 debug_putstr("EFI system table not found."); 73 return 0; 74 } 75 76 return sys_tbl_pa; 77 } 78 79 /* 80 * EFI config table address changes to virtual address after boot, which may 81 * not be accessible for the kexec'd kernel. To address this, kexec provides 82 * the initial physical address via a struct setup_data entry, which is 83 * checked for here, along with some sanity checks. 84 */ 85 static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp, 86 enum efi_type et) 87 { 88 #ifdef CONFIG_X86_64 89 struct efi_setup_data *esd = NULL; 90 struct setup_data *data; 91 u64 pa_data; 92 93 pa_data = bp->hdr.setup_data; 94 while (pa_data) { 95 data = (struct setup_data *)pa_data; 96 if (data->type == SETUP_EFI) { 97 esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data)); 98 break; 99 } 100 101 pa_data = data->next; 102 } 103 104 /* 105 * Original ACPI code falls back to attempting normal EFI boot in these 106 * cases, so maintain existing behavior by indicating non-kexec 107 * environment to the caller, but print them for debugging. 108 */ 109 if (esd && !esd->tables) { 110 debug_putstr("kexec EFI environment missing valid configuration table.\n"); 111 return NULL; 112 } 113 114 return esd; 115 #endif 116 return NULL; 117 } 118 119 /** 120 * efi_get_conf_table - Given a pointer to boot_params, locate and return the physical 121 * address of EFI configuration table. 122 * 123 * @bp: pointer to boot_params 124 * @cfg_tbl_pa: location to store physical address of config table 125 * @cfg_tbl_len: location to store number of config table entries 126 * 127 * Return: 0 on success. On error, return params are left unchanged. 128 */ 129 int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa, 130 unsigned int *cfg_tbl_len) 131 { 132 unsigned long sys_tbl_pa; 133 enum efi_type et; 134 int ret; 135 136 if (!cfg_tbl_pa || !cfg_tbl_len) 137 return -EINVAL; 138 139 sys_tbl_pa = efi_get_system_table(bp); 140 if (!sys_tbl_pa) 141 return -EINVAL; 142 143 /* Handle EFI bitness properly */ 144 et = efi_get_type(bp); 145 if (et == EFI_TYPE_64) { 146 efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa; 147 struct efi_setup_data *esd; 148 149 /* kexec provides an alternative EFI conf table, check for it. */ 150 esd = get_kexec_setup_data(bp, et); 151 152 *cfg_tbl_pa = esd ? esd->tables : stbl->tables; 153 *cfg_tbl_len = stbl->nr_tables; 154 } else if (et == EFI_TYPE_32) { 155 efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa; 156 157 *cfg_tbl_pa = stbl->tables; 158 *cfg_tbl_len = stbl->nr_tables; 159 } else { 160 return -EINVAL; 161 } 162 163 return 0; 164 } 165 166 /* Get vendor table address/guid from EFI config table at the given index */ 167 static int get_vendor_table(void *cfg_tbl, unsigned int idx, 168 unsigned long *vendor_tbl_pa, 169 efi_guid_t *vendor_tbl_guid, 170 enum efi_type et) 171 { 172 if (et == EFI_TYPE_64) { 173 efi_config_table_64_t *tbl_entry = (efi_config_table_64_t *)cfg_tbl + idx; 174 175 if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) { 176 debug_putstr("Error: EFI config table entry located above 4GB.\n"); 177 return -EINVAL; 178 } 179 180 *vendor_tbl_pa = tbl_entry->table; 181 *vendor_tbl_guid = tbl_entry->guid; 182 183 } else if (et == EFI_TYPE_32) { 184 efi_config_table_32_t *tbl_entry = (efi_config_table_32_t *)cfg_tbl + idx; 185 186 *vendor_tbl_pa = tbl_entry->table; 187 *vendor_tbl_guid = tbl_entry->guid; 188 } else { 189 return -EINVAL; 190 } 191 192 return 0; 193 } 194 195 /** 196 * efi_find_vendor_table - Given EFI config table, search it for the physical 197 * address of the vendor table associated with GUID. 198 * 199 * @bp: pointer to boot_params 200 * @cfg_tbl_pa: pointer to EFI configuration table 201 * @cfg_tbl_len: number of entries in EFI configuration table 202 * @guid: GUID of vendor table 203 * 204 * Return: vendor table address on success. On error, return 0. 205 */ 206 unsigned long efi_find_vendor_table(struct boot_params *bp, 207 unsigned long cfg_tbl_pa, 208 unsigned int cfg_tbl_len, 209 efi_guid_t guid) 210 { 211 enum efi_type et; 212 unsigned int i; 213 214 et = efi_get_type(bp); 215 if (et == EFI_TYPE_NONE) 216 return 0; 217 218 for (i = 0; i < cfg_tbl_len; i++) { 219 unsigned long vendor_tbl_pa; 220 efi_guid_t vendor_tbl_guid; 221 int ret; 222 223 ret = get_vendor_table((void *)cfg_tbl_pa, i, 224 &vendor_tbl_pa, 225 &vendor_tbl_guid, et); 226 if (ret) 227 return 0; 228 229 if (!efi_guidcmp(guid, vendor_tbl_guid)) 230 return vendor_tbl_pa; 231 } 232 233 return 0; 234 } 235