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 - 2025, 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
 17ACPI_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 ******************************************************************************/
 35acpi_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
 86acpi_status
 87acpi_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
129u8 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
160u8 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}