acpica/utcksum.c

   1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
   2 /******************************************************************************
   3  *
   4  * Module Name: utcksum - Support generating table checksums
   5  *
   6  * Copyright (C) 2000 - 2023, Intel Corp.
   7  *
   8  *****************************************************************************/
   9
  10 #include <acpi/acpi.h>
  11 #include "accommon.h"
  12 #include "acutils.h"
  13
  14 /* This module used for application-level code only */
  15
  16 #define _COMPONENT          ACPI_CA_DISASSEMBLER
  17 ACPI_MODULE_NAME("utcksum")
  18
  19 /*******************************************************************************
  20  *
  21  * FUNCTION:    acpi_ut_verify_checksum
  22  *
  23  * PARAMETERS:  table               - ACPI table to verify
  24  *              length              - Length of entire table
  25  *
  26  * RETURN:      Status
  27  *
  28  * DESCRIPTION: Verifies that the table checksums to zero. Optionally returns
  29  *              exception on bad checksum.
  30  *              Note: We don't have to check for a CDAT here, since CDAT is
  31  *              not in the RSDT/XSDT, and the CDAT table is never installed
  32  *              via ACPICA.
  33  *
  34  ******************************************************************************/
  35 acpi_status acpi_ut_verify_checksum(struct acpi_table_header *table, u32 length)
  36 {
  37         u8 checksum;
  38
  39         /*
  40          * FACS/S3PT:
  41          * They are the odd tables, have no standard ACPI header and no checksum
  42          */
  43         if (ACPI_COMPARE_NAMESEG(table->signature, ACPI_SIG_S3PT) ||
  44             ACPI_COMPARE_NAMESEG(table->signature, ACPI_SIG_FACS)) {
  45                 return (AE_OK);
  46         }
  47
  48         /* Compute the checksum on the table */
  49
  50         length = table->length;
  51         checksum =
  52             acpi_ut_generate_checksum(ACPI_CAST_PTR(u8, table), length,
  53                                       table->checksum);
  54
  55         /* Computed checksum matches table? */
  56
  57         if (checksum != table->checksum) {
  58                 ACPI_BIOS_WARNING((AE_INFO,
  59                                    "Incorrect checksum in table [%4.4s] - 0x%2.2X, "
  60                                    "should be 0x%2.2X",
  61                                    table->signature, table->checksum,
  62                                    table->checksum - checksum));
  63
  64 #if (ACPI_CHECKSUM_ABORT)
  65                 return (AE_BAD_CHECKSUM);
  66 #endif
  67         }
  68
  69         return (AE_OK);
  70 }
  71
  72 /*******************************************************************************
  73  *
  74  * FUNCTION:    acpi_ut_verify_cdat_checksum
  75  *
  76  * PARAMETERS:  table               - CDAT ACPI table to verify
  77  *              length              - Length of entire table
  78  *
  79  * RETURN:      Status
  80  *
  81  * DESCRIPTION: Verifies that the CDAT table checksums to zero. Optionally
  82  *              returns an exception on bad checksum.
  83  *
  84  ******************************************************************************/
  85
  86 acpi_status
  87 acpi_ut_verify_cdat_checksum(struct acpi_table_cdat *cdat_table, u32 length)
  88 {
  89         u8 checksum;
  90
  91         /* Compute the checksum on the table */
  92
  93         checksum = acpi_ut_generate_checksum(ACPI_CAST_PTR(u8, cdat_table),
  94                                              cdat_table->length,
  95                                              cdat_table->checksum);
  96
  97         /* Computed checksum matches table? */
  98
  99         if (checksum != cdat_table->checksum) {
 100                 ACPI_BIOS_WARNING((AE_INFO,
 101                                    "Incorrect checksum in table [%4.4s] - 0x%2.2X, "
 102                                    "should be 0x%2.2X",
 103                                    acpi_gbl_CDAT, cdat_table->checksum,
 104                                    checksum));
 105
 106 #if (ACPI_CHECKSUM_ABORT)
 107                 return (AE_BAD_CHECKSUM);
 108 #endif
 109         }
 110
 111         cdat_table->checksum = checksum;
 112         return (AE_OK);
 113 }
 114
 115 /*******************************************************************************
 116  *
 117  * FUNCTION:    acpi_ut_generate_checksum
 118  *
 119  * PARAMETERS:  table               - Pointer to table to be checksummed
 120  *              length              - Length of the table
 121  *              original_checksum   - Value of the checksum field
 122  *
 123  * RETURN:      8 bit checksum of buffer
 124  *
 125  * DESCRIPTION: Computes an 8 bit checksum of the table.
 126  *
 127  ******************************************************************************/
 128
 129 u8 acpi_ut_generate_checksum(void *table, u32 length, u8 original_checksum)
 130 {
 131         u8 checksum;
 132
 133         /* Sum the entire table as-is */
 134
 135         checksum = acpi_ut_checksum((u8 *)table, length);
 136
 137         /* Subtract off the existing checksum value in the table */
 138
 139         checksum = (u8)(checksum - original_checksum);
 140
 141         /* Compute and return the final checksum */
 142
 143         checksum = (u8)(0 - checksum);
 144         return (checksum);
 145 }
 146
 147 /*******************************************************************************
 148  *
 149  * FUNCTION:    acpi_ut_checksum
 150  *
 151  * PARAMETERS:  buffer          - Pointer to memory region to be checked
 152  *              length          - Length of this memory region
 153  *
 154  * RETURN:      Checksum (u8)
 155  *
 156  * DESCRIPTION: Calculates circular checksum of memory region.
 157  *
 158  ******************************************************************************/
 159
 160 u8 acpi_ut_checksum(u8 *buffer, u32 length)
 161 {
 162         u8 sum = 0;
 163         u8 *end = buffer + length;
 164
 165         while (buffer < end) {
 166                 sum = (u8)(sum + *(buffer++));
 167         }
 168
 169         return (sum);
 170 }