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 - 2019, 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 }