1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 2 /****************************************************************************** 3 * 4 * Module Name: tbxfroot - Find the root ACPI table (RSDT) 5 * 6 * Copyright (C) 2000 - 2021, Intel Corp. 7 * 8 *****************************************************************************/ 9 10 #include <acpi/acpi.h> 11 #include "accommon.h" 12 #include "actables.h" 13 14 #define _COMPONENT ACPI_TABLES 15 ACPI_MODULE_NAME("tbxfroot") 16 17 /******************************************************************************* 18 * 19 * FUNCTION: acpi_tb_get_rsdp_length 20 * 21 * PARAMETERS: rsdp - Pointer to RSDP 22 * 23 * RETURN: Table length 24 * 25 * DESCRIPTION: Get the length of the RSDP 26 * 27 ******************************************************************************/ 28 u32 acpi_tb_get_rsdp_length(struct acpi_table_rsdp *rsdp) 29 { 30 31 if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) { 32 33 /* BAD Signature */ 34 35 return (0); 36 } 37 38 /* "Length" field is available if table version >= 2 */ 39 40 if (rsdp->revision >= 2) { 41 return (rsdp->length); 42 } else { 43 return (ACPI_RSDP_CHECKSUM_LENGTH); 44 } 45 } 46 47 /******************************************************************************* 48 * 49 * FUNCTION: acpi_tb_validate_rsdp 50 * 51 * PARAMETERS: rsdp - Pointer to unvalidated RSDP 52 * 53 * RETURN: Status 54 * 55 * DESCRIPTION: Validate the RSDP (ptr) 56 * 57 ******************************************************************************/ 58 59 acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp) 60 { 61 62 /* 63 * The signature and checksum must both be correct 64 * 65 * Note: Sometimes there exists more than one RSDP in memory; the valid 66 * RSDP has a valid checksum, all others have an invalid checksum. 67 */ 68 if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) { 69 70 /* Nope, BAD Signature */ 71 72 return (AE_BAD_SIGNATURE); 73 } 74 75 /* Check the standard checksum */ 76 77 if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) { 78 return (AE_BAD_CHECKSUM); 79 } 80 81 /* Check extended checksum if table version >= 2 */ 82 83 if ((rsdp->revision >= 2) && 84 (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) { 85 return (AE_BAD_CHECKSUM); 86 } 87 88 return (AE_OK); 89 } 90 91 /******************************************************************************* 92 * 93 * FUNCTION: acpi_find_root_pointer 94 * 95 * PARAMETERS: table_address - Where the table pointer is returned 96 * 97 * RETURN: Status, RSDP physical address 98 * 99 * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor 100 * pointer structure. If it is found, set *RSDP to point to it. 101 * 102 * NOTE1: The RSDP must be either in the first 1K of the Extended 103 * BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.) 104 * Only a 32-bit physical address is necessary. 105 * 106 * NOTE2: This function is always available, regardless of the 107 * initialization state of the rest of ACPI. 108 * 109 ******************************************************************************/ 110 111 acpi_status ACPI_INIT_FUNCTION 112 acpi_find_root_pointer(acpi_physical_address *table_address) 113 { 114 u8 *table_ptr; 115 u8 *mem_rover; 116 u32 physical_address; 117 118 ACPI_FUNCTION_TRACE(acpi_find_root_pointer); 119 120 /* 1a) Get the location of the Extended BIOS Data Area (EBDA) */ 121 122 table_ptr = acpi_os_map_memory((acpi_physical_address) 123 ACPI_EBDA_PTR_LOCATION, 124 ACPI_EBDA_PTR_LENGTH); 125 if (!table_ptr) { 126 ACPI_ERROR((AE_INFO, 127 "Could not map memory at 0x%8.8X for length %u", 128 ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH)); 129 130 return_ACPI_STATUS(AE_NO_MEMORY); 131 } 132 133 ACPI_MOVE_16_TO_32(&physical_address, table_ptr); 134 135 /* Convert segment part to physical address */ 136 137 physical_address <<= 4; 138 acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH); 139 140 /* EBDA present? */ 141 142 if (physical_address > 0x400) { 143 /* 144 * 1b) Search EBDA paragraphs (EBDA is required to be a 145 * minimum of 1K length) 146 */ 147 table_ptr = acpi_os_map_memory((acpi_physical_address) 148 physical_address, 149 ACPI_EBDA_WINDOW_SIZE); 150 if (!table_ptr) { 151 ACPI_ERROR((AE_INFO, 152 "Could not map memory at 0x%8.8X for length %u", 153 physical_address, ACPI_EBDA_WINDOW_SIZE)); 154 155 return_ACPI_STATUS(AE_NO_MEMORY); 156 } 157 158 mem_rover = 159 acpi_tb_scan_memory_for_rsdp(table_ptr, 160 ACPI_EBDA_WINDOW_SIZE); 161 acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE); 162 163 if (mem_rover) { 164 165 /* Return the physical address */ 166 167 physical_address += 168 (u32) ACPI_PTR_DIFF(mem_rover, table_ptr); 169 170 *table_address = 171 (acpi_physical_address)physical_address; 172 return_ACPI_STATUS(AE_OK); 173 } 174 } 175 176 /* 177 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh 178 */ 179 table_ptr = acpi_os_map_memory((acpi_physical_address) 180 ACPI_HI_RSDP_WINDOW_BASE, 181 ACPI_HI_RSDP_WINDOW_SIZE); 182 183 if (!table_ptr) { 184 ACPI_ERROR((AE_INFO, 185 "Could not map memory at 0x%8.8X for length %u", 186 ACPI_HI_RSDP_WINDOW_BASE, 187 ACPI_HI_RSDP_WINDOW_SIZE)); 188 189 return_ACPI_STATUS(AE_NO_MEMORY); 190 } 191 192 mem_rover = 193 acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE); 194 acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE); 195 196 if (mem_rover) { 197 198 /* Return the physical address */ 199 200 physical_address = (u32) 201 (ACPI_HI_RSDP_WINDOW_BASE + 202 ACPI_PTR_DIFF(mem_rover, table_ptr)); 203 204 *table_address = (acpi_physical_address)physical_address; 205 return_ACPI_STATUS(AE_OK); 206 } 207 208 /* A valid RSDP was not found */ 209 210 ACPI_BIOS_ERROR((AE_INFO, "A valid RSDP was not found")); 211 return_ACPI_STATUS(AE_NOT_FOUND); 212 } 213 214 ACPI_EXPORT_SYMBOL_INIT(acpi_find_root_pointer) 215 216 /******************************************************************************* 217 * 218 * FUNCTION: acpi_tb_scan_memory_for_rsdp 219 * 220 * PARAMETERS: start_address - Starting pointer for search 221 * length - Maximum length to search 222 * 223 * RETURN: Pointer to the RSDP if found, otherwise NULL. 224 * 225 * DESCRIPTION: Search a block of memory for the RSDP signature 226 * 227 ******************************************************************************/ 228 u8 *acpi_tb_scan_memory_for_rsdp(u8 *start_address, u32 length) 229 { 230 acpi_status status; 231 u8 *mem_rover; 232 u8 *end_address; 233 234 ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp); 235 236 end_address = start_address + length; 237 238 /* Search from given start address for the requested length */ 239 240 for (mem_rover = start_address; mem_rover < end_address; 241 mem_rover += ACPI_RSDP_SCAN_STEP) { 242 243 /* The RSDP signature and checksum must both be correct */ 244 245 status = 246 acpi_tb_validate_rsdp(ACPI_CAST_PTR 247 (struct acpi_table_rsdp, mem_rover)); 248 if (ACPI_SUCCESS(status)) { 249 250 /* Sig and checksum valid, we have found a real RSDP */ 251 252 ACPI_DEBUG_PRINT((ACPI_DB_INFO, 253 "RSDP located at physical address %p\n", 254 mem_rover)); 255 return_PTR(mem_rover); 256 } 257 258 /* No sig match or bad checksum, keep searching */ 259 } 260 261 /* Searched entire block, no RSDP was found */ 262 263 ACPI_DEBUG_PRINT((ACPI_DB_INFO, 264 "Searched entire block from %p, valid RSDP was not found\n", 265 start_address)); 266 return_PTR(NULL); 267 } 268