1 /******************************************************************************
2  *
3  * Module Name: tbxfroot - Find the root ACPI table (RSDT)
4  *
5  *****************************************************************************/
6 
7 /*
8  * Copyright (C) 2000 - 2022, Intel Corp.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions, and the following disclaimer,
16  *    without modification.
17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
18  *    substantially similar to the "NO WARRANTY" disclaimer below
19  *    ("Disclaimer") and any redistribution must be conditioned upon
20  *    including a substantially similar Disclaimer requirement for further
21  *    binary redistribution.
22  * 3. Neither the names of the above-listed copyright holders nor the names
23  *    of any contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * Alternatively, this software may be distributed under the terms of the
27  * GNU General Public License ("GPL") version 2 as published by the Free
28  * Software Foundation.
29  *
30  * NO WARRANTY
31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41  * POSSIBILITY OF SUCH DAMAGES.
42  */
43 
44 #include "acpi.h"
45 #include "accommon.h"
46 #include "actables.h"
47 
48 
49 #define _COMPONENT          ACPI_TABLES
50         ACPI_MODULE_NAME    ("tbxfroot")
51 
52 
53 /*******************************************************************************
54  *
55  * FUNCTION:    AcpiTbGetRsdpLength
56  *
57  * PARAMETERS:  Rsdp                - Pointer to RSDP
58  *
59  * RETURN:      Table length
60  *
61  * DESCRIPTION: Get the length of the RSDP
62  *
63  ******************************************************************************/
64 
65 UINT32
66 AcpiTbGetRsdpLength (
67     ACPI_TABLE_RSDP         *Rsdp)
68 {
69 
70     if (!ACPI_VALIDATE_RSDP_SIG (Rsdp->Signature))
71     {
72         /* BAD Signature */
73 
74         return (0);
75     }
76 
77     /* "Length" field is available if table version >= 2 */
78 
79     if (Rsdp->Revision >= 2)
80     {
81         return (Rsdp->Length);
82     }
83     else
84     {
85         return (ACPI_RSDP_CHECKSUM_LENGTH);
86     }
87 }
88 
89 
90 /*******************************************************************************
91  *
92  * FUNCTION:    AcpiTbValidateRsdp
93  *
94  * PARAMETERS:  Rsdp                - Pointer to unvalidated RSDP
95  *
96  * RETURN:      Status
97  *
98  * DESCRIPTION: Validate the RSDP (ptr)
99  *
100  ******************************************************************************/
101 
102 ACPI_STATUS
103 AcpiTbValidateRsdp (
104     ACPI_TABLE_RSDP         *Rsdp)
105 {
106 
107     /*
108      * The signature and checksum must both be correct
109      *
110      * Note: Sometimes there exists more than one RSDP in memory; the valid
111      * RSDP has a valid checksum, all others have an invalid checksum.
112      */
113     if (!ACPI_VALIDATE_RSDP_SIG (Rsdp->Signature))
114     {
115         /* Nope, BAD Signature */
116 
117         return (AE_BAD_SIGNATURE);
118     }
119 
120     /* Check the standard checksum */
121 
122     if (AcpiUtChecksum ((UINT8 *) Rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0)
123     {
124         return (AE_BAD_CHECKSUM);
125     }
126 
127     /* Check extended checksum if table version >= 2 */
128 
129     if ((Rsdp->Revision >= 2) &&
130         (AcpiUtChecksum ((UINT8 *) Rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0))
131     {
132         return (AE_BAD_CHECKSUM);
133     }
134 
135     return (AE_OK);
136 }
137 
138 
139 /*******************************************************************************
140  *
141  * FUNCTION:    AcpiFindRootPointer
142  *
143  * PARAMETERS:  TableAddress            - Where the table pointer is returned
144  *
145  * RETURN:      Status, RSDP physical address
146  *
147  * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor
148  *              pointer structure. If it is found, set *RSDP to point to it.
149  *
150  * NOTE1:       The RSDP must be either in the first 1K of the Extended
151  *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
152  *              Only a 32-bit physical address is necessary.
153  *
154  * NOTE2:       This function is always available, regardless of the
155  *              initialization state of the rest of ACPI.
156  *
157  ******************************************************************************/
158 
159 ACPI_STATUS ACPI_INIT_FUNCTION
160 AcpiFindRootPointer (
161     ACPI_PHYSICAL_ADDRESS   *TableAddress)
162 {
163     UINT8                   *TablePtr;
164     UINT8                   *MemRover;
165     UINT32                  PhysicalAddress;
166     UINT32                  EbdaWindowSize;
167 
168 
169     ACPI_FUNCTION_TRACE (AcpiFindRootPointer);
170 
171 
172     /* 1a) Get the location of the Extended BIOS Data Area (EBDA) */
173 
174     TablePtr = AcpiOsMapMemory (
175         (ACPI_PHYSICAL_ADDRESS) ACPI_EBDA_PTR_LOCATION,
176         ACPI_EBDA_PTR_LENGTH);
177     if (!TablePtr)
178     {
179         ACPI_ERROR ((AE_INFO,
180             "Could not map memory at 0x%8.8X for length %u",
181             ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));
182 
183         return_ACPI_STATUS (AE_NO_MEMORY);
184     }
185 
186     ACPI_MOVE_16_TO_32 (&PhysicalAddress, TablePtr);
187 
188     /* Convert segment part to physical address */
189 
190     PhysicalAddress <<= 4;
191     AcpiOsUnmapMemory (TablePtr, ACPI_EBDA_PTR_LENGTH);
192 
193     /* EBDA present? */
194 
195     /*
196      * Check that the EBDA pointer from memory is sane and does not point
197      * above valid low memory
198      */
199     if (PhysicalAddress > 0x400 &&
200         PhysicalAddress < 0xA0000)
201     {
202         /*
203          * Calculate the scan window size
204          * The EBDA is not guaranteed to be larger than a KiB and in case
205          * that it is smaller, the scanning function would leave the low
206          * memory and continue to the VGA range.
207          */
208         EbdaWindowSize = ACPI_MIN(ACPI_EBDA_WINDOW_SIZE,
209             0xA0000 - PhysicalAddress);
210 
211         /*
212          * 1b) Search EBDA paragraphs
213          */
214         TablePtr = AcpiOsMapMemory (
215             (ACPI_PHYSICAL_ADDRESS) PhysicalAddress,
216             EbdaWindowSize);
217         if (!TablePtr)
218         {
219             ACPI_ERROR ((AE_INFO,
220                 "Could not map memory at 0x%8.8X for length %u",
221                 PhysicalAddress, EbdaWindowSize));
222 
223             return_ACPI_STATUS (AE_NO_MEMORY);
224         }
225 
226         MemRover = AcpiTbScanMemoryForRsdp (
227             TablePtr, EbdaWindowSize);
228         AcpiOsUnmapMemory (TablePtr, EbdaWindowSize);
229 
230         if (MemRover)
231         {
232             /* Return the physical address */
233 
234             PhysicalAddress +=
235                 (UINT32) ACPI_PTR_DIFF (MemRover, TablePtr);
236 
237             *TableAddress = (ACPI_PHYSICAL_ADDRESS) PhysicalAddress;
238             return_ACPI_STATUS (AE_OK);
239         }
240     }
241 
242     /*
243      * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
244      */
245     TablePtr = AcpiOsMapMemory (
246         (ACPI_PHYSICAL_ADDRESS) ACPI_HI_RSDP_WINDOW_BASE,
247         ACPI_HI_RSDP_WINDOW_SIZE);
248 
249     if (!TablePtr)
250     {
251         ACPI_ERROR ((AE_INFO,
252             "Could not map memory at 0x%8.8X for length %u",
253             ACPI_HI_RSDP_WINDOW_BASE, ACPI_HI_RSDP_WINDOW_SIZE));
254 
255         return_ACPI_STATUS (AE_NO_MEMORY);
256     }
257 
258     MemRover = AcpiTbScanMemoryForRsdp (
259         TablePtr, ACPI_HI_RSDP_WINDOW_SIZE);
260     AcpiOsUnmapMemory (TablePtr, ACPI_HI_RSDP_WINDOW_SIZE);
261 
262     if (MemRover)
263     {
264         /* Return the physical address */
265 
266         PhysicalAddress = (UINT32)
267             (ACPI_HI_RSDP_WINDOW_BASE + ACPI_PTR_DIFF (MemRover, TablePtr));
268 
269         *TableAddress = (ACPI_PHYSICAL_ADDRESS) PhysicalAddress;
270         return_ACPI_STATUS (AE_OK);
271     }
272 
273     /* A valid RSDP was not found */
274 
275     ACPI_BIOS_ERROR ((AE_INFO, "A valid RSDP was not found"));
276     return_ACPI_STATUS (AE_NOT_FOUND);
277 }
278 
279 ACPI_EXPORT_SYMBOL_INIT (AcpiFindRootPointer)
280 
281 
282 /*******************************************************************************
283  *
284  * FUNCTION:    AcpiTbScanMemoryForRsdp
285  *
286  * PARAMETERS:  StartAddress        - Starting pointer for search
287  *              Length              - Maximum length to search
288  *
289  * RETURN:      Pointer to the RSDP if found, otherwise NULL.
290  *
291  * DESCRIPTION: Search a block of memory for the RSDP signature
292  *
293  ******************************************************************************/
294 
295 UINT8 *
296 AcpiTbScanMemoryForRsdp (
297     UINT8                   *StartAddress,
298     UINT32                  Length)
299 {
300     ACPI_STATUS             Status;
301     UINT8                   *MemRover;
302     UINT8                   *EndAddress;
303 
304 
305     ACPI_FUNCTION_TRACE (TbScanMemoryForRsdp);
306 
307 
308     EndAddress = StartAddress + Length;
309 
310     /* Search from given start address for the requested length */
311 
312     for (MemRover = StartAddress; MemRover < EndAddress;
313          MemRover += ACPI_RSDP_SCAN_STEP)
314     {
315         /* The RSDP signature and checksum must both be correct */
316 
317         Status = AcpiTbValidateRsdp (
318             ACPI_CAST_PTR (ACPI_TABLE_RSDP, MemRover));
319         if (ACPI_SUCCESS (Status))
320         {
321             /* Sig and checksum valid, we have found a real RSDP */
322 
323             ACPI_DEBUG_PRINT ((ACPI_DB_INFO,
324                 "RSDP located at physical address %p\n", MemRover));
325             return_PTR (MemRover);
326         }
327 
328         /* No sig match or bad checksum, keep searching */
329     }
330 
331     /* Searched entire block, no RSDP was found */
332 
333     ACPI_DEBUG_PRINT ((ACPI_DB_INFO,
334         "Searched entire block from %p, valid RSDP was not found\n",
335         StartAddress));
336     return_PTR (NULL);
337 }
338