1/******************************************************************************
2 *
3 * Module Name: tbxfroot - Find the root ACPI table (RSDT)
4 *
5 *****************************************************************************/
6
7/*
8 * Copyright (C) 2000 - 2007, R. Byron Moore
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 <acpi/actables.h>
46
47#define _COMPONENT          ACPI_TABLES
48ACPI_MODULE_NAME("tbxfroot")
49
50/* Local prototypes */
51static u8 *acpi_tb_scan_memory_for_rsdp(u8 * start_address, u32 length);
52
53static acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp);
54
55/*******************************************************************************
56 *
57 * FUNCTION:    acpi_tb_validate_rsdp
58 *
59 * PARAMETERS:  Rsdp                - Pointer to unvalidated RSDP
60 *
61 * RETURN:      Status
62 *
63 * DESCRIPTION: Validate the RSDP (ptr)
64 *
65 ******************************************************************************/
66
67static acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp)
68{
69	ACPI_FUNCTION_ENTRY();
70
71	/*
72	 * The signature and checksum must both be correct
73	 *
74	 * Note: Sometimes there exists more than one RSDP in memory; the valid
75	 * RSDP has a valid checksum, all others have an invalid checksum.
76	 */
77	if (ACPI_STRNCMP((char *)rsdp, ACPI_SIG_RSDP, sizeof(ACPI_SIG_RSDP) - 1)
78	    != 0) {
79
80		/* Nope, BAD Signature */
81
82		return (AE_BAD_SIGNATURE);
83	}
84
85	/* Check the standard checksum */
86
87	if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {
88		return (AE_BAD_CHECKSUM);
89	}
90
91	/* Check extended checksum if table version >= 2 */
92
93	if ((rsdp->revision >= 2) &&
94	    (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {
95		return (AE_BAD_CHECKSUM);
96	}
97
98	return (AE_OK);
99}
100
101/*******************************************************************************
102 *
103 * FUNCTION:    acpi_tb_find_rsdp
104 *
105 * PARAMETERS:  table_address           - Where the table pointer is returned
106 *
107 * RETURN:      Status, RSDP physical address
108 *
109 * DESCRIPTION: Search lower 1_mbyte of memory for the root system descriptor
110 *              pointer structure.  If it is found, set *RSDP to point to it.
111 *
112 * NOTE1:       The RSDP must be either in the first 1_k of the Extended
113 *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
114 *              Only a 32-bit physical address is necessary.
115 *
116 * NOTE2:       This function is always available, regardless of the
117 *              initialization state of the rest of ACPI.
118 *
119 ******************************************************************************/
120
121acpi_status acpi_find_root_pointer(acpi_native_uint * table_address)
122{
123	u8 *table_ptr;
124	u8 *mem_rover;
125	u32 physical_address;
126
127	ACPI_FUNCTION_TRACE(acpi_find_root_pointer);
128
129	/* 1a) Get the location of the Extended BIOS Data Area (EBDA) */
130
131	table_ptr = acpi_os_map_memory((acpi_physical_address)
132				       ACPI_EBDA_PTR_LOCATION,
133				       ACPI_EBDA_PTR_LENGTH);
134	if (!table_ptr) {
135		ACPI_ERROR((AE_INFO,
136			    "Could not map memory at %8.8X for length %X",
137			    ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));
138
139		return_ACPI_STATUS(AE_NO_MEMORY);
140	}
141
142	ACPI_MOVE_16_TO_32(&physical_address, table_ptr);
143
144	/* Convert segment part to physical address */
145
146	physical_address <<= 4;
147	acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);
148
149	/* EBDA present? */
150
151	if (physical_address > 0x400) {
152		/*
153		 * 1b) Search EBDA paragraphs (EBDA is required to be a
154		 *     minimum of 1_k length)
155		 */
156		table_ptr = acpi_os_map_memory((acpi_native_uint)
157					       physical_address,
158					       ACPI_EBDA_WINDOW_SIZE);
159		if (!table_ptr) {
160			ACPI_ERROR((AE_INFO,
161				    "Could not map memory at %8.8X for length %X",
162				    physical_address, ACPI_EBDA_WINDOW_SIZE));
163
164			return_ACPI_STATUS(AE_NO_MEMORY);
165		}
166
167		mem_rover =
168		    acpi_tb_scan_memory_for_rsdp(table_ptr,
169						 ACPI_EBDA_WINDOW_SIZE);
170		acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);
171
172		if (mem_rover) {
173
174			/* Return the physical address */
175
176			physical_address +=
177			    (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);
178
179			*table_address = physical_address;
180			return_ACPI_STATUS(AE_OK);
181		}
182	}
183
184	/*
185	 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
186	 */
187	table_ptr = acpi_os_map_memory((acpi_physical_address)
188				       ACPI_HI_RSDP_WINDOW_BASE,
189				       ACPI_HI_RSDP_WINDOW_SIZE);
190
191	if (!table_ptr) {
192		ACPI_ERROR((AE_INFO,
193			    "Could not map memory at %8.8X for length %X",
194			    ACPI_HI_RSDP_WINDOW_BASE,
195			    ACPI_HI_RSDP_WINDOW_SIZE));
196
197		return_ACPI_STATUS(AE_NO_MEMORY);
198	}
199
200	mem_rover =
201	    acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
202	acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
203
204	if (mem_rover) {
205
206		/* Return the physical address */
207
208		physical_address = (u32)
209		    (ACPI_HI_RSDP_WINDOW_BASE +
210		     ACPI_PTR_DIFF(mem_rover, table_ptr));
211
212		*table_address = physical_address;
213		return_ACPI_STATUS(AE_OK);
214	}
215
216	/* A valid RSDP was not found */
217
218	ACPI_ERROR((AE_INFO, "A valid RSDP was not found"));
219	return_ACPI_STATUS(AE_NOT_FOUND);
220}
221
222ACPI_EXPORT_SYMBOL(acpi_find_root_pointer)
223
224/*******************************************************************************
225 *
226 * FUNCTION:    acpi_tb_scan_memory_for_rsdp
227 *
228 * PARAMETERS:  start_address       - Starting pointer for search
229 *              Length              - Maximum length to search
230 *
231 * RETURN:      Pointer to the RSDP if found, otherwise NULL.
232 *
233 * DESCRIPTION: Search a block of memory for the RSDP signature
234 *
235 ******************************************************************************/
236static u8 *acpi_tb_scan_memory_for_rsdp(u8 * start_address, u32 length)
237{
238	acpi_status status;
239	u8 *mem_rover;
240	u8 *end_address;
241
242	ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);
243
244	end_address = start_address + length;
245
246	/* Search from given start address for the requested length */
247
248	for (mem_rover = start_address; mem_rover < end_address;
249	     mem_rover += ACPI_RSDP_SCAN_STEP) {
250
251		/* The RSDP signature and checksum must both be correct */
252
253		status =
254		    acpi_tb_validate_rsdp(ACPI_CAST_PTR
255					  (struct acpi_table_rsdp, mem_rover));
256		if (ACPI_SUCCESS(status)) {
257
258			/* Sig and checksum valid, we have found a real RSDP */
259
260			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
261					  "RSDP located at physical address %p\n",
262					  mem_rover));
263			return_PTR(mem_rover);
264		}
265
266		/* No sig match or bad checksum, keep searching */
267	}
268
269	/* Searched entire block, no RSDP was found */
270
271	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
272			  "Searched entire block from %p, valid RSDP was not found\n",
273			  start_address));
274	return_PTR(NULL);
275}
276