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authorUwe Hermann <uwe@hermann-uwe.de>2008-03-01 19:09:01 +0000
committerUwe Hermann <uwe@hermann-uwe.de>2008-03-01 19:09:01 +0000
commitcbb5ba8633c2ad143366c3bc367f8c4f6434c084 (patch)
tree5cd9812c1ca9ab13e3791221bdd8217627df860f /util/nvramtool/nvramtool.c
parent66d83cfa84f75ad3fba38d3b926da531d800b8a5 (diff)
downloadcoreboot-cbb5ba8633c2ad143366c3bc367f8c4f6434c084.tar.xz
Rename lxbios to nvramtool, step 3 (rename directory).
Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de> Acked-by: Stefan Reinauer <stepan@coresystems.de> git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3124 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
Diffstat (limited to 'util/nvramtool/nvramtool.c')
-rw-r--r--util/nvramtool/nvramtool.c754
1 files changed, 754 insertions, 0 deletions
diff --git a/util/nvramtool/nvramtool.c b/util/nvramtool/nvramtool.c
new file mode 100644
index 0000000000..98de6dc929
--- /dev/null
+++ b/util/nvramtool/nvramtool.c
@@ -0,0 +1,754 @@
+/*****************************************************************************\
+ * nvramtool.c
+ * $Id$
+ *****************************************************************************
+ * Copyright (C) 2002-2005 The Regents of the University of California.
+ * Produced at the Lawrence Livermore National Laboratory.
+ * Written by Dave Peterson <dsp@llnl.gov> <dave_peterson@pobox.com>.
+ * UCRL-CODE-2003-012
+ * All rights reserved.
+ *
+ * This file is part of nvramtool, a utility for reading/writing coreboot
+ * parameters and displaying information from the coreboot table.
+ * For details, see http://coreboot.org/nvramtool.
+ *
+ * Please also read the file DISCLAIMER which is included in this software
+ * distribution.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License (as published by the
+ * Free Software Foundation) version 2, dated June 1991.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+ * conditions of the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+\*****************************************************************************/
+
+#include "common.h"
+#include "opts.h"
+#include "lbtable.h"
+#include "layout.h"
+#include "layout_file.h"
+#include "input_file.h"
+#include "cmos_ops.h"
+#include "cmos_lowlevel.h"
+#include "reg_expr.h"
+#include "hexdump.h"
+
+typedef void (*op_fn_t) (void);
+
+static void op_show_version (void);
+static void op_show_usage (void);
+static void op_lbtable_show_info (void);
+static void op_lbtable_dump (void);
+static void op_show_param_values (void);
+static void op_cmos_show_one_param (void);
+static void op_cmos_show_all_params (void);
+static void op_cmos_set_one_param (void);
+static void op_cmos_set_params_stdin (void);
+static void op_cmos_set_params_file (void);
+static void op_cmos_checksum (void);
+static void op_show_layout (void);
+static void op_write_cmos_dump (void);
+static void op_read_cmos_dump (void);
+static void op_show_cmos_hex_dump (void);
+static void op_show_cmos_dumpfile (void);
+static int list_one_param (const char name[], int show_name);
+static int list_all_params (void);
+static void list_param_enums (const char name[]);
+static void set_one_param (const char name[], const char value[]);
+static void set_params (FILE *f);
+static void parse_assignment (char arg[], const char **name,
+ const char **value);
+static int list_cmos_entry (const cmos_entry_t *e, int show_name);
+static uint16_t convert_checksum_value (const char value[]);
+
+static const op_fn_t op_fns[] =
+ { op_show_version,
+ op_show_usage,
+ op_lbtable_show_info,
+ op_lbtable_dump,
+ op_show_param_values,
+ op_cmos_show_one_param,
+ op_cmos_show_all_params,
+ op_cmos_set_one_param,
+ op_cmos_set_params_stdin,
+ op_cmos_set_params_file,
+ op_cmos_checksum,
+ op_show_layout,
+ op_write_cmos_dump,
+ op_read_cmos_dump,
+ op_show_cmos_hex_dump,
+ op_show_cmos_dumpfile
+ };
+
+static const hexdump_format_t cmos_dump_format =
+ { 16, 2, "", " | ", " ", " | ", '.', NULL };
+
+/****************************************************************************
+ * main
+ ****************************************************************************/
+int main (int argc, char *argv[])
+ { cmos_layout_get_fn_t fn;
+
+ parse_nvramtool_args(argc, argv);
+
+ if (nvramtool_op_modifiers[NVRAMTOOL_MOD_USE_CMOS_LAYOUT_FILE].found)
+ { set_layout_filename(
+ nvramtool_op_modifiers[NVRAMTOOL_MOD_USE_CMOS_LAYOUT_FILE].param);
+ fn = get_layout_from_file;
+ }
+ else
+ fn = get_layout_from_cmos_table;
+
+ register_cmos_layout_get_fn(fn);
+ op_fns[nvramtool_op.op]();
+ return 0;
+ }
+
+/****************************************************************************
+ * op_show_version
+ *
+ * -v
+ *
+ * Show version information for this program.
+ ****************************************************************************/
+static void op_show_version (void)
+ { printf("This is %s version %s.\n", prog_name, prog_version); }
+
+/****************************************************************************
+ * op_show_usage
+ *
+ * -h
+ *
+ * Show a usage message for this program.
+ ****************************************************************************/
+static void op_show_usage (void)
+ { usage(stdout); }
+
+/****************************************************************************
+ * op_lbtable_show_info
+ *
+ * -l [ARG]
+ *
+ * If ARG is present, show coreboot table information specified by ARG.
+ * Else show all possible values for ARG.
+ ****************************************************************************/
+static void op_lbtable_show_info (void)
+ { if (nvramtool_op.param == NULL)
+ list_lbtable_choices();
+ else
+ { get_lbtable();
+ list_lbtable_item(nvramtool_op.param);
+ }
+ }
+
+/****************************************************************************
+ * op_lbtable_dump
+ *
+ * -d
+ *
+ * Do low-level dump of coreboot table.
+ ****************************************************************************/
+static void op_lbtable_dump (void)
+ { get_lbtable();
+ dump_lbtable();
+ }
+
+/****************************************************************************
+ * op_show_param_values
+ *
+ * -e NAME option
+ *
+ * Show all possible values for parameter NAME.
+ ****************************************************************************/
+static void op_show_param_values (void)
+ { get_cmos_layout();
+ list_param_enums(nvramtool_op.param);
+ }
+
+/****************************************************************************
+ * op_cmos_show_one_param
+ *
+ * [-n] -r NAME
+ *
+ * Show parameter NAME. If -n is specified, show value only. Else show name
+ * and value.
+ ****************************************************************************/
+static void op_cmos_show_one_param (void)
+ { int result;
+
+ get_cmos_layout();
+ result = list_one_param(nvramtool_op.param,
+ !nvramtool_op_modifiers[NVRAMTOOL_MOD_SHOW_VALUE_ONLY].found);
+ cmos_checksum_verify();
+
+ if (result)
+ exit(1);
+ }
+
+/****************************************************************************
+ * op_cmos_show_all_params
+ *
+ * -a
+ *
+ * Show names and values for all parameters.
+ ****************************************************************************/
+static void op_cmos_show_all_params (void)
+ { int result;
+
+ get_cmos_layout();
+ result = list_all_params();
+ cmos_checksum_verify();
+
+ if (result)
+ exit(1);
+ }
+
+/****************************************************************************
+ * op_cmos_set_one_param
+ *
+ * -w NAME=VALUE
+ *
+ * Set parameter NAME to VALUE.
+ ****************************************************************************/
+static void op_cmos_set_one_param (void)
+ { const char *name, *value;
+
+ get_cmos_layout();
+
+ /* Separate 'NAME=VALUE' syntax into two strings representing NAME and
+ * VALUE.
+ */
+ parse_assignment(nvramtool_op.param, &name, &value);
+
+ set_one_param(name, value);
+ }
+
+/****************************************************************************
+ * op_cmos_set_params_stdin
+ *
+ * -i
+ *
+ * Set parameters according to standard input.
+ ****************************************************************************/
+static void op_cmos_set_params_stdin (void)
+ { get_cmos_layout();
+ set_params(stdin);
+ }
+
+/****************************************************************************
+ * op_cmos_set_params_file
+ *
+ * -p INPUT_FILE
+ *
+ * Set parameters according to INPUT_FILE.
+ ****************************************************************************/
+static void op_cmos_set_params_file (void)
+ { FILE *f;
+
+ if ((f = fopen(nvramtool_op.param, "r")) == NULL)
+ { fprintf(stderr, "%s: Can not open file %s for reading: %s\n",
+ prog_name, nvramtool_op.param, strerror(errno));
+ exit(1);
+ }
+
+ get_cmos_layout();
+ set_params(f);
+ fclose(f);
+ }
+
+/****************************************************************************
+ * op_cmos_checksum
+ *
+ * -c [VALUE]
+ *
+ * If VALUE is present, set coreboot CMOS checksum to VALUE. Else show
+ * checksum value.
+ ****************************************************************************/
+static void op_cmos_checksum (void)
+ { uint16_t checksum;
+
+ get_cmos_layout();
+
+ if (nvramtool_op.param == NULL)
+ { set_iopl(3);
+ checksum = cmos_checksum_read();
+ set_iopl(0);
+ printf("0x%x\n", checksum);
+ }
+ else
+ { checksum = convert_checksum_value(nvramtool_op.param);
+ set_iopl(3);
+ cmos_checksum_write(checksum);
+ set_iopl(0);
+ }
+ }
+
+/****************************************************************************
+ * op_show_layout
+ *
+ * -Y
+ *
+ * Write CMOS layout information to standard output.
+ ****************************************************************************/
+static void op_show_layout (void)
+ { get_cmos_layout();
+ write_cmos_layout(stdout);
+ }
+
+/****************************************************************************
+ * op_write_cmos_dump
+ *
+ * -b OUTPUT_FILE
+ *
+ * Write the contents of CMOS memory to a binary file.
+ ****************************************************************************/
+static void op_write_cmos_dump (void)
+ { unsigned char data[CMOS_SIZE];
+ FILE *f;
+
+ if ((f = fopen(nvramtool_op.param, "w")) == NULL)
+ { fprintf(stderr, "%s: Can not open file %s for writing: %s\n",
+ prog_name, nvramtool_op.param, strerror(errno));
+ exit(1);
+ }
+
+ set_iopl(3);
+ cmos_read_all(data);
+ set_iopl(0);
+
+ if (fwrite(data, 1, CMOS_SIZE, f) != CMOS_SIZE)
+ { fprintf(stderr, "%s: Error writing CMOS data to file %s: %s\n",
+ prog_name, nvramtool_op.param, strerror(errno));
+ exit(1);
+ }
+
+ fclose(f);
+ }
+
+/****************************************************************************
+ * op_read_cmos_dump
+ *
+ * -B INPUT_FILE
+ *
+ * Read binary data from a file and write the data to CMOS memory.
+ ****************************************************************************/
+static void op_read_cmos_dump (void)
+ { unsigned char data[CMOS_SIZE];
+ size_t nr_bytes;
+ FILE *f;
+
+ if ((f = fopen(nvramtool_op.param, "r")) == NULL)
+ { fprintf(stderr, "%s: Can not open file %s for reading: %s\n",
+ prog_name, nvramtool_op.param, strerror(errno));
+ exit(1);
+ }
+
+ if ((nr_bytes = fread(data, 1, CMOS_SIZE, f)) != CMOS_SIZE)
+ { fprintf(stderr, "%s: Error: Only able to read %d bytes of CMOS data "
+ "from file %s. CMOS data is unchanged.\n", prog_name,
+ (int) nr_bytes, nvramtool_op.param);
+ exit(1);
+ }
+
+ fclose(f);
+ set_iopl(3);
+ cmos_write_all(data);
+ set_iopl(0);
+ }
+
+/****************************************************************************
+ * op_show_cmos_hex_dump
+ *
+ * -x
+ *
+ * Write a hex dump of CMOS memory to standard output.
+ ****************************************************************************/
+static void op_show_cmos_hex_dump (void)
+ { unsigned char data[CMOS_SIZE];
+
+ set_iopl(3);
+ cmos_read_all(data);
+ set_iopl(0);
+ hexdump(data, CMOS_SIZE, 0, stdout, &cmos_dump_format);
+ }
+
+/****************************************************************************
+ * op_show_cmos_dumpfile
+ *
+ * -X DUMP_FILE
+ *
+ * Read binary data from a file (presumably a CMOS dump file) and display a
+ * hex dump of the CMOS data from the file.
+ ****************************************************************************/
+static void op_show_cmos_dumpfile (void)
+ { unsigned char data[CMOS_SIZE];
+ size_t nr_bytes;
+ FILE *f;
+
+ if ((f = fopen(nvramtool_op.param, "r")) == NULL)
+ { fprintf(stderr, "%s: Can not open file %s for reading: %s\n",
+ prog_name, nvramtool_op.param, strerror(errno));
+ exit(1);
+ }
+
+ nr_bytes = fread(data, 1, CMOS_SIZE, f);
+ fclose(f);
+ hexdump(data, nr_bytes, 0, stdout, &cmos_dump_format);
+ }
+
+/****************************************************************************
+ * list_one_param
+ *
+ * Attempt to list one CMOS parameter given by 'name'. 'show_name' is a
+ * boolean value indicating whether the parameter name should be displayed
+ * along with its value. Return 1 if error was encountered. Else return OK.
+ ****************************************************************************/
+static int list_one_param (const char name[], int show_name)
+ { const cmos_entry_t *e;
+
+ if (is_checksum_name(name) || ((e = find_cmos_entry(name)) == NULL))
+ { fprintf(stderr, "%s: CMOS parameter %s not found.\n", prog_name, name);
+ exit(1);
+ }
+
+ if (e->config == CMOS_ENTRY_RESERVED)
+ { fprintf(stderr, "%s: Parameter %s is reserved.\n", prog_name, name);
+ exit(1);
+ }
+
+ return (list_cmos_entry(e, show_name) != 0);
+ }
+
+/****************************************************************************
+ * list_all_params
+ *
+ * Attempt to list all CMOS parameters. Return 1 if error was encountered.
+ * Else return OK.
+ ****************************************************************************/
+static int list_all_params (void)
+ { const cmos_entry_t *e;
+ int result;
+
+ result = OK;
+
+ for (e = first_cmos_entry(); e != NULL; e = next_cmos_entry(e))
+ { if ((e->config == CMOS_ENTRY_RESERVED) || is_checksum_name(e->name))
+ continue;
+
+ if (list_cmos_entry(e, TRUE))
+ result = 1;
+ }
+
+ return result;
+ }
+
+/****************************************************************************
+ * list_param_enums
+ *
+ * List all possible values for CMOS parameter given by 'name'.
+ ****************************************************************************/
+static void list_param_enums (const char name[])
+ { const cmos_entry_t *e;
+ const cmos_enum_t *p;
+
+ if (is_checksum_name(name) || (e = find_cmos_entry(name)) == NULL)
+ { fprintf(stderr, "%s: CMOS parameter %s not found.\n", prog_name, name);
+ exit(1);
+ }
+
+ switch (e->config)
+ { case CMOS_ENTRY_ENUM:
+ for (p = first_cmos_enum_id(e->config_id);
+ p != NULL;
+ p = next_cmos_enum_id(p))
+ printf("%s\n", p->text);
+
+ break;
+
+ case CMOS_ENTRY_HEX:
+ printf("Parameter %s requires a %u-bit unsigned integer.\n", name,
+ e->length);
+ break;
+
+ case CMOS_ENTRY_RESERVED:
+ printf("Parameter %s is reserved.\n", name);
+ break;
+
+ default:
+ BUG();
+ }
+ }
+
+/****************************************************************************
+ * set_one_param
+ *
+ * Set the CMOS parameter given by 'name' to 'value'. The 'name' parameter
+ * is case-sensitive. If we are setting an enum parameter, then 'value' is
+ * interpreted as a case-sensitive string that must match the option name
+ * exactly. If we are setting a 'hex' parameter, then 'value' is treated as
+ * a string representation of an unsigned integer that may be specified in
+ * decimal, hex, or octal.
+ ****************************************************************************/
+static void set_one_param (const char name[], const char value[])
+ { const cmos_entry_t *e;
+ unsigned long long n;
+
+ if (is_checksum_name(name) || (e = find_cmos_entry(name)) == NULL)
+ { fprintf(stderr, "%s: CMOS parameter %s not found.", prog_name, name);
+ exit(1);
+ }
+
+ switch (prepare_cmos_write(e, value, &n))
+ { case OK:
+ break;
+
+ case CMOS_OP_BAD_ENUM_VALUE:
+ fprintf(stderr, "%s: Bad value for parameter %s.", prog_name, name);
+ goto fail;
+
+ case CMOS_OP_NEGATIVE_INT:
+ fprintf(stderr,
+ "%s: This program does not support assignment of negative "
+ "numbers to coreboot parameters.", prog_name);
+ goto fail;
+
+ case CMOS_OP_INVALID_INT:
+ fprintf(stderr, "%s: %s is not a valid integer.", prog_name, value);
+ goto fail;
+
+ case CMOS_OP_RESERVED:
+ fprintf(stderr,
+ "%s: Can not modify reserved coreboot parameter %s.",
+ prog_name, name);
+ goto fail;
+
+ case CMOS_OP_VALUE_TOO_WIDE:
+ fprintf(stderr,
+ "%s: Can not write value %s to CMOS parameter %s that is "
+ "only %d bits wide.", prog_name, value, name, e->length);
+ goto fail;
+
+ case CMOS_OP_NO_MATCHING_ENUM:
+ fprintf(stderr,
+ "%s: coreboot parameter %s has no matching enums.",
+ prog_name, name);
+ goto fail;
+
+ case CMOS_AREA_OUT_OF_RANGE:
+ fprintf(stderr,
+ "%s: The CMOS area specified by the layout info for "
+ "coreboot parameter %s is out of range.", prog_name, name);
+ goto fail;
+
+ case CMOS_AREA_OVERLAPS_RTC:
+ fprintf(stderr,
+ "%s: The CMOS area specified by the layout info for "
+ "coreboot parameter %s overlaps the realtime clock area.",
+ prog_name, name);
+ goto fail;
+
+ case CMOS_AREA_TOO_WIDE:
+ fprintf(stderr,
+ "%s: The CMOS area specified by the layout info for "
+ "coreboot parameter %s is too wide.",
+ prog_name, name);
+ goto fail;
+
+ default:
+ fprintf(stderr,
+ "%s: Unknown error encountered while attempting to modify "
+ "coreboot parameter %s.", prog_name, name);
+ goto fail;
+ }
+
+ /* write the value to nonvolatile RAM */
+ set_iopl(3);
+ cmos_write(e->bit, e->length, n);
+ cmos_checksum_write(cmos_checksum_compute());
+ set_iopl(0);
+ return;
+
+fail:
+ fprintf(stderr, " CMOS write not performed.\n");
+ exit(1);
+ }
+
+/****************************************************************************
+ * set_params
+ *
+ * Set coreboot parameters according to the contents of file 'f'.
+ ****************************************************************************/
+static void set_params (FILE *f)
+ { /* First process the input file. Then perform writes only if there were
+ * no problems processing the input. Either all values will be written
+ * successfully or no values will be written.
+ */
+ do_cmos_writes(process_input_file(f));
+ }
+
+/****************************************************************************
+ * parse_assignment
+ *
+ * Parse the string 'arg' (which supposedly represents an assignment) into a
+ * NAME and a VALUE. If 'arg' does not conform to the proper assignment
+ * syntax, exit with a usage message. Otherwise, on return, 'arg' is broken
+ * into substrings representing NAME and VALUE, and *name and *value are set
+ * to point to these two substrings.
+ ****************************************************************************/
+static void parse_assignment (char arg[], const char **name,
+ const char **value)
+ { static const size_t N_MATCHES = 4;
+ regmatch_t match[N_MATCHES];
+ regex_t assignment;
+
+ compile_reg_exprs(REG_EXTENDED | REG_NEWLINE, 1, assignment_regex,
+ &assignment);
+
+ /* Does 'arg' conform to proper assignment syntax? If not, exit with a
+ * usage message.
+ */
+ if (regexec(&assignment, arg, N_MATCHES, match, 0))
+ usage(stderr);
+
+ /* Ok, we found a valid assignment. Break it into two strings
+ * representing NAME and VALUE.
+ */
+ arg[match[1].rm_eo] = '\0';
+ arg[match[2].rm_eo] = '\0';
+ *name = &arg[match[1].rm_so];
+ *value = &arg[match[2].rm_so];
+
+ free_reg_exprs(1, &assignment);
+ }
+
+/****************************************************************************
+ * list_cmos_entry
+ *
+ * Attempt to list the CMOS entry represented by 'e'. 'show_name' is a
+ * boolean value indicating whether the parameter name should be displayed
+ * along with its value. On success, return OK. On error, print an error
+ * message and return 1.
+ ****************************************************************************/
+static int list_cmos_entry (const cmos_entry_t *e, int show_name)
+ { const cmos_enum_t *p;
+ unsigned long long value;
+
+ /* sanity check CMOS entry */
+ switch (prepare_cmos_read(e))
+ { case OK:
+ break;
+
+ case CMOS_OP_RESERVED:
+ BUG();
+
+ case CMOS_AREA_OUT_OF_RANGE:
+ fprintf(stderr, "%s: Can not read coreboot parameter %s because "
+ "layout info specifies out of range CMOS area.\n", prog_name,
+ e->name);
+ return 1;
+
+ case CMOS_AREA_OVERLAPS_RTC:
+ fprintf(stderr, "%s: Can not read coreboot parameter %s because "
+ "layout info specifies CMOS area that overlaps realtime "
+ "clock area.\n", prog_name, e->name);
+ return 1;
+
+ case CMOS_AREA_TOO_WIDE:
+ fprintf(stderr, "%s: Can not read coreboot parameter %s because "
+ "layout info specifies CMOS area that is too wide.\n",
+ prog_name, e->name);
+ return 1;
+
+ default:
+ fprintf(stderr, "%s: Unknown error encountered while attempting to "
+ "read coreboot parameter %s\n", prog_name, e->name);
+ return 1;
+ }
+
+ /* read the value from CMOS */
+ set_iopl(3);
+ value = cmos_read(e->bit, e->length);
+ set_iopl(0);
+
+ /* display the value */
+ switch (e->config)
+ { case CMOS_ENTRY_ENUM:
+ if ((p = find_cmos_enum(e->config_id, value)) == NULL)
+ { if (show_name)
+ printf("# Bad value -> %s = 0x%llx\n", e->name, value);
+ else
+ printf("Bad value -> 0x%llx\n", value);
+ }
+ else
+ { if (show_name)
+ printf("%s = %s\n", e->name, p->text);
+ else
+ printf("%s\n", p->text);
+ }
+
+ break;
+
+ case CMOS_ENTRY_HEX:
+ if (show_name)
+ printf("%s = 0x%llx\n", e->name, value);
+ else
+ printf("0x%llx\n", value);
+
+ break;
+
+ case CMOS_ENTRY_RESERVED:
+ default:
+ BUG();
+ }
+
+ return OK;
+ }
+
+/****************************************************************************
+ * convert_checksum_value
+ *
+ * 'value' is the string representation of a checksum value that the user
+ * wishes to set using the -c option. Convert the string to a 16-bit
+ * unsigned integer and return the result. Exit with an error message if
+ * 'value' is invalid.
+ ****************************************************************************/
+static uint16_t convert_checksum_value (const char value[])
+ { unsigned long n;
+ const char *p;
+ uint16_t result;
+ int negative;
+
+ for (p = value; isspace(*p); p++);
+
+ negative = (*p == '-');
+ n = strtoul(value, (char **) &p, 0);
+
+ if (*p)
+ { fprintf(stderr, "%s: Checksum value %s is not a valid integer.\n",
+ prog_name, value);
+ exit(1);
+ }
+
+ if (negative)
+ { fprintf(stderr,
+ "%s: Checksum must be an unsigned integer.\n", prog_name);
+ exit(1);
+ }
+
+ result = (uint16_t) n;
+
+ if (result != n)
+ { fprintf(stderr,
+ "%s: Checksum value must fit within 16 bits.\n", prog_name);
+ exit(1);
+ }
+
+ return result;
+ }