drivers/acpi/tables/tbxfroot.c

   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
  48 ACPI_MODULE_NAME("tbxfroot")
  49
  50 /* Local prototypes */
  51 static u8 *acpi_tb_scan_memory_for_rsdp(u8 * start_address, u32 length);
  52
  53 static 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
  67 static 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
 121 acpi_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
 222 ACPI_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  ******************************************************************************/
 236 static 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 }