1/******************************************************************************
2 *
3 * Module Name: tbxfroot - Find the root ACPI table (RSDT)
4 *
5 *****************************************************************************/
6
7/*
8 * Copyright (C) 2000 - 2015, 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 MERCHANTIBILITY 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/acpi.h>
45#include "accommon.h"
46#include "actables.h"
47
48#define _COMPONENT          ACPI_TABLES
49ACPI_MODULE_NAME("tbxfroot")
50
51/*******************************************************************************
52 *
53 * FUNCTION:    acpi_tb_get_rsdp_length
54 *
55 * PARAMETERS:  rsdp                - Pointer to RSDP
56 *
57 * RETURN:      Table length
58 *
59 * DESCRIPTION: Get the length of the RSDP
60 *
61 ******************************************************************************/
62u32 acpi_tb_get_rsdp_length(struct acpi_table_rsdp *rsdp)
63{
64
65	if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {
66
67		/* BAD Signature */
68
69		return (0);
70	}
71
72	/* "Length" field is available if table version >= 2 */
73
74	if (rsdp->revision >= 2) {
75		return (rsdp->length);
76	} else {
77		return (ACPI_RSDP_CHECKSUM_LENGTH);
78	}
79}
80
81/*******************************************************************************
82 *
83 * FUNCTION:    acpi_tb_validate_rsdp
84 *
85 * PARAMETERS:  rsdp                - Pointer to unvalidated RSDP
86 *
87 * RETURN:      Status
88 *
89 * DESCRIPTION: Validate the RSDP (ptr)
90 *
91 ******************************************************************************/
92
93acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp * rsdp)
94{
95
96	/*
97	 * The signature and checksum must both be correct
98	 *
99	 * Note: Sometimes there exists more than one RSDP in memory; the valid
100	 * RSDP has a valid checksum, all others have an invalid checksum.
101	 */
102	if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {
103
104		/* Nope, BAD Signature */
105
106		return (AE_BAD_SIGNATURE);
107	}
108
109	/* Check the standard checksum */
110
111	if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {
112		return (AE_BAD_CHECKSUM);
113	}
114
115	/* Check extended checksum if table version >= 2 */
116
117	if ((rsdp->revision >= 2) &&
118	    (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {
119		return (AE_BAD_CHECKSUM);
120	}
121
122	return (AE_OK);
123}
124
125/*******************************************************************************
126 *
127 * FUNCTION:    acpi_find_root_pointer
128 *
129 * PARAMETERS:  table_address           - Where the table pointer is returned
130 *
131 * RETURN:      Status, RSDP physical address
132 *
133 * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor
134 *              pointer structure. If it is found, set *RSDP to point to it.
135 *
136 * NOTE1:       The RSDP must be either in the first 1K of the Extended
137 *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
138 *              Only a 32-bit physical address is necessary.
139 *
140 * NOTE2:       This function is always available, regardless of the
141 *              initialization state of the rest of ACPI.
142 *
143 ******************************************************************************/
144
145acpi_status __init acpi_find_root_pointer(acpi_physical_address * table_address)
146{
147	u8 *table_ptr;
148	u8 *mem_rover;
149	u32 physical_address;
150
151	ACPI_FUNCTION_TRACE(acpi_find_root_pointer);
152
153	/* 1a) Get the location of the Extended BIOS Data Area (EBDA) */
154
155	table_ptr = acpi_os_map_memory((acpi_physical_address)
156				       ACPI_EBDA_PTR_LOCATION,
157				       ACPI_EBDA_PTR_LENGTH);
158	if (!table_ptr) {
159		ACPI_ERROR((AE_INFO,
160			    "Could not map memory at 0x%8.8X for length %u",
161			    ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));
162
163		return_ACPI_STATUS(AE_NO_MEMORY);
164	}
165
166	ACPI_MOVE_16_TO_32(&physical_address, table_ptr);
167
168	/* Convert segment part to physical address */
169
170	physical_address <<= 4;
171	acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);
172
173	/* EBDA present? */
174
175	if (physical_address > 0x400) {
176		/*
177		 * 1b) Search EBDA paragraphs (EBDA is required to be a
178		 *     minimum of 1K length)
179		 */
180		table_ptr = acpi_os_map_memory((acpi_physical_address)
181					       physical_address,
182					       ACPI_EBDA_WINDOW_SIZE);
183		if (!table_ptr) {
184			ACPI_ERROR((AE_INFO,
185				    "Could not map memory at 0x%8.8X for length %u",
186				    physical_address, ACPI_EBDA_WINDOW_SIZE));
187
188			return_ACPI_STATUS(AE_NO_MEMORY);
189		}
190
191		mem_rover =
192		    acpi_tb_scan_memory_for_rsdp(table_ptr,
193						 ACPI_EBDA_WINDOW_SIZE);
194		acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);
195
196		if (mem_rover) {
197
198			/* Return the physical address */
199
200			physical_address +=
201			    (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);
202
203			*table_address =
204			    (acpi_physical_address) physical_address;
205			return_ACPI_STATUS(AE_OK);
206		}
207	}
208
209	/*
210	 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
211	 */
212	table_ptr = acpi_os_map_memory((acpi_physical_address)
213				       ACPI_HI_RSDP_WINDOW_BASE,
214				       ACPI_HI_RSDP_WINDOW_SIZE);
215
216	if (!table_ptr) {
217		ACPI_ERROR((AE_INFO,
218			    "Could not map memory at 0x%8.8X for length %u",
219			    ACPI_HI_RSDP_WINDOW_BASE,
220			    ACPI_HI_RSDP_WINDOW_SIZE));
221
222		return_ACPI_STATUS(AE_NO_MEMORY);
223	}
224
225	mem_rover =
226	    acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
227	acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
228
229	if (mem_rover) {
230
231		/* Return the physical address */
232
233		physical_address = (u32)
234		    (ACPI_HI_RSDP_WINDOW_BASE +
235		     ACPI_PTR_DIFF(mem_rover, table_ptr));
236
237		*table_address = (acpi_physical_address) physical_address;
238		return_ACPI_STATUS(AE_OK);
239	}
240
241	/* A valid RSDP was not found */
242
243	ACPI_BIOS_ERROR((AE_INFO, "A valid RSDP was not found"));
244	return_ACPI_STATUS(AE_NOT_FOUND);
245}
246
247/*******************************************************************************
248 *
249 * FUNCTION:    acpi_tb_scan_memory_for_rsdp
250 *
251 * PARAMETERS:  start_address       - Starting pointer for search
252 *              length              - Maximum length to search
253 *
254 * RETURN:      Pointer to the RSDP if found, otherwise NULL.
255 *
256 * DESCRIPTION: Search a block of memory for the RSDP signature
257 *
258 ******************************************************************************/
259u8 *acpi_tb_scan_memory_for_rsdp(u8 *start_address, u32 length)
260{
261	acpi_status status;
262	u8 *mem_rover;
263	u8 *end_address;
264
265	ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);
266
267	end_address = start_address + length;
268
269	/* Search from given start address for the requested length */
270
271	for (mem_rover = start_address; mem_rover < end_address;
272	     mem_rover += ACPI_RSDP_SCAN_STEP) {
273
274		/* The RSDP signature and checksum must both be correct */
275
276		status =
277		    acpi_tb_validate_rsdp(ACPI_CAST_PTR
278					  (struct acpi_table_rsdp, mem_rover));
279		if (ACPI_SUCCESS(status)) {
280
281			/* Sig and checksum valid, we have found a real RSDP */
282
283			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
284					  "RSDP located at physical address %p\n",
285					  mem_rover));
286			return_PTR(mem_rover);
287		}
288
289		/* No sig match or bad checksum, keep searching */
290	}
291
292	/* Searched entire block, no RSDP was found */
293
294	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
295			  "Searched entire block from %p, valid RSDP was not found\n",
296			  start_address));
297	return_PTR(NULL);
298}
299