Quelle  tbxfroot.c   Sprache: C

// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
/******************************************************************************
 *
 * Module Name: tbxfroot - Find the root ACPI table (RSDT)
 *
 * Copyright (C) 2000 - 2025, Intel Corp.
 *
 *****************************************************************************/

#include <acpi/acpi.h>
#include "accommon.h"
#include "actables.h"

#define _COMPONENT          ACPI_TABLES
ACPI_MODULE_NAME("tbxfroot")

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_get_rsdp_length
 *
 * PARAMETERS:  rsdp                - Pointer to RSDP
 *
 * RETURN:      Table length
 *
 * DESCRIPTION: Get the length of the RSDP
 *
 ******************************************************************************/
u32 acpi_tb_get_rsdp_length(struct acpi_table_rsdp *rsdp)
{

 if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {

  /* BAD Signature */

  return (0);
 }

 /* "Length" field is available if table version >= 2 */

 if (rsdp->revision >= 2) {
  return (rsdp->length);
 } else {
  return (ACPI_RSDP_CHECKSUM_LENGTH);
 }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_validate_rsdp
 *
 * PARAMETERS:  rsdp                - Pointer to unvalidated RSDP
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Validate the RSDP (ptr)
 *
 ******************************************************************************/

acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp)
{

 /*
 * The signature and checksum must both be correct
 *
 * Note: Sometimes there exists more than one RSDP in memory; the valid
 * RSDP has a valid checksum, all others have an invalid checksum.
 */
 if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {

  /* Nope, BAD Signature */

  return (AE_BAD_SIGNATURE);
 }

 /* Check the standard checksum */

 if (acpi_ut_checksum((u8 *)rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {
  return (AE_BAD_CHECKSUM);
 }

 /* Check extended checksum if table version >= 2 */

 if ((rsdp->revision >= 2) &&
     (acpi_ut_checksum((u8 *)rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {
  return (AE_BAD_CHECKSUM);
 }

 return (AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_find_root_pointer
 *
 * PARAMETERS:  table_address           - Where the table pointer is returned
 *
 * RETURN:      Status, RSDP physical address
 *
 * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor
 *              pointer structure. If it is found, set *RSDP to point to it.
 *
 * NOTE1:       The RSDP must be either in the first 1K of the Extended
 *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
 *              Only a 32-bit physical address is necessary.
 *
 * NOTE2:       This function is always available, regardless of the
 *              initialization state of the rest of ACPI.
 *
 ******************************************************************************/

acpi_status ACPI_INIT_FUNCTION
acpi_find_root_pointer(acpi_physical_address *table_address)
{
 u8 *table_ptr;
 u8 *mem_rover;
 u32 physical_address;
 u32 ebda_window_size;

 ACPI_FUNCTION_TRACE(acpi_find_root_pointer);

 /* 1a) Get the location of the Extended BIOS Data Area (EBDA) */

 table_ptr = acpi_os_map_memory((acpi_physical_address)
           ACPI_EBDA_PTR_LOCATION,
           ACPI_EBDA_PTR_LENGTH);
 if (!table_ptr) {
  ACPI_ERROR((AE_INFO,
       "Could not map memory at 0x%8.8X for length %u",
       ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));

  return_ACPI_STATUS(AE_NO_MEMORY);
 }

 ACPI_MOVE_16_TO_32(&physical_address, table_ptr);

 /* Convert segment part to physical address */

 physical_address <<= 4;
 acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);

 /* EBDA present? */

 /*
 * Check that the EBDA pointer from memory is sane and does not point
 * above valid low memory
 */
 if (physical_address > 0x400 && physical_address < 0xA0000) {
  /*
 * Calculate the scan window size
 * The EBDA is not guaranteed to be larger than a ki_b and in case
 * that it is smaller, the scanning function would leave the low
 * memory and continue to the VGA range.
 */
  ebda_window_size = ACPI_MIN(ACPI_EBDA_WINDOW_SIZE,
         0xA0000 - physical_address);

  /*
 * 1b) Search EBDA paragraphs
 */
  table_ptr = acpi_os_map_memory((acpi_physical_address)
            physical_address,
            ebda_window_size);
  if (!table_ptr) {
   ACPI_ERROR((AE_INFO,
        "Could not map memory at 0x%8.8X for length %u",
        physical_address, ebda_window_size));

   return_ACPI_STATUS(AE_NO_MEMORY);
  }

  mem_rover =
      acpi_tb_scan_memory_for_rsdp(table_ptr, ebda_window_size);
  acpi_os_unmap_memory(table_ptr, ebda_window_size);

  if (mem_rover) {

   /* Return the physical address */

   physical_address +=
       (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);

   *table_address =
       (acpi_physical_address)physical_address;
   return_ACPI_STATUS(AE_OK);
  }
 }

 /*
 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
 */
 table_ptr = acpi_os_map_memory((acpi_physical_address)
           ACPI_HI_RSDP_WINDOW_BASE,
           ACPI_HI_RSDP_WINDOW_SIZE);

 if (!table_ptr) {
  ACPI_ERROR((AE_INFO,
       "Could not map memory at 0x%8.8X for length %u",
       ACPI_HI_RSDP_WINDOW_BASE,
       ACPI_HI_RSDP_WINDOW_SIZE));

  return_ACPI_STATUS(AE_NO_MEMORY);
 }

 mem_rover =
     acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
 acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);

 if (mem_rover) {

  /* Return the physical address */

  physical_address = (u32)
      (ACPI_HI_RSDP_WINDOW_BASE +
       ACPI_PTR_DIFF(mem_rover, table_ptr));

  *table_address = (acpi_physical_address)physical_address;
  return_ACPI_STATUS(AE_OK);
 }

 /* A valid RSDP was not found */

 ACPI_BIOS_ERROR((AE_INFO, "A valid RSDP was not found"));
 return_ACPI_STATUS(AE_NOT_FOUND);
}

ACPI_EXPORT_SYMBOL_INIT(acpi_find_root_pointer)

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_scan_memory_for_rsdp
 *
 * PARAMETERS:  start_address       - Starting pointer for search
 *              length              - Maximum length to search
 *
 * RETURN:      Pointer to the RSDP if found, otherwise NULL.
 *
 * DESCRIPTION: Search a block of memory for the RSDP signature
 *
 ******************************************************************************/
u8 *acpi_tb_scan_memory_for_rsdp(u8 *start_address, u32 length)
{
 acpi_status status;
 u8 *mem_rover;
 u8 *end_address;

 ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);

 end_address = start_address + length;

 /* Search from given start address for the requested length */

 for (mem_rover = start_address; mem_rover < end_address;
      mem_rover += ACPI_RSDP_SCAN_STEP) {

  /* The RSDP signature and checksum must both be correct */

  status =
      acpi_tb_validate_rsdp(ACPI_CAST_PTR
       (struct acpi_table_rsdp, mem_rover));
  if (ACPI_SUCCESS(status)) {

   /* Sig and checksum valid, we have found a real RSDP */

   ACPI_DEBUG_PRINT((ACPI_DB_INFO,
       "RSDP located at physical address %p\n",
       mem_rover));
   return_PTR(mem_rover);
  }

  /* No sig match or bad checksum, keep searching */
 }

 /* Searched entire block, no RSDP was found */

 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
     "Searched entire block from %p, valid RSDP was not found\n",
     start_address));
 return_PTR(NULL);
}