xref: /openbmc/linux/scripts/kconfig/confdata.c (revision 57ddd07c456053dfdabebc6a2d030c57cd3fb75b)

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
 */

#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "lkc.h"

/* return true if 'path' exists, false otherwise */
static bool is_present(const char *path)
{
	struct stat st;

	return !stat(path, &st);
}

/* return true if 'path' exists and it is a directory, false otherwise */
static bool is_dir(const char *path)
{
	struct stat st;

	if (stat(path, &st))
		return false;

	return S_ISDIR(st.st_mode);
}

/* return true if the given two files are the same, false otherwise */
static bool is_same(const char *file1, const char *file2)
{
	int fd1, fd2;
	struct stat st1, st2;
	void *map1, *map2;
	bool ret = false;

	fd1 = open(file1, O_RDONLY);
	if (fd1 < 0)
		return ret;

	fd2 = open(file2, O_RDONLY);
	if (fd2 < 0)
		goto close1;

	ret = fstat(fd1, &st1);
	if (ret)
		goto close2;
	ret = fstat(fd2, &st2);
	if (ret)
		goto close2;

	if (st1.st_size != st2.st_size)
		goto close2;

	map1 = mmap(NULL, st1.st_size, PROT_READ, MAP_PRIVATE, fd1, 0);
	if (map1 == MAP_FAILED)
		goto close2;

	map2 = mmap(NULL, st2.st_size, PROT_READ, MAP_PRIVATE, fd2, 0);
	if (map2 == MAP_FAILED)
		goto close2;

	if (bcmp(map1, map2, st1.st_size))
		goto close2;

	ret = true;
close2:
	close(fd2);
close1:
	close(fd1);

	return ret;
}

/*
 * Create the parent directory of the given path.
 *
 * For example, if 'include/config/auto.conf' is given, create 'include/config'.
 */
static int make_parent_dir(const char *path)
{
	char tmp[PATH_MAX + 1];
	char *p;

	strncpy(tmp, path, sizeof(tmp));
	tmp[sizeof(tmp) - 1] = 0;

	/* Remove the base name. Just return if nothing is left */
	p = strrchr(tmp, '/');
	if (!p)
		return 0;
	*(p + 1) = 0;

	/* Just in case it is an absolute path */
	p = tmp;
	while (*p == '/')
		p++;

	while ((p = strchr(p, '/'))) {
		*p = 0;

		/* skip if the directory exists */
		if (!is_dir(tmp) && mkdir(tmp, 0755))
			return -1;

		*p = '/';
		while (*p == '/')
			p++;
	}

	return 0;
}

static char depfile_path[PATH_MAX];
static size_t depfile_prefix_len;

/* touch depfile for symbol 'name' */
static int conf_touch_dep(const char *name)
{
	int fd, ret;
	char *d;

	/* check overflow: prefix + name + '\0' must fit in buffer. */
	if (depfile_prefix_len + strlen(name) + 1 > sizeof(depfile_path))
		return -1;

	d = depfile_path + depfile_prefix_len;
	strcpy(d, name);

	/* Assume directory path already exists. */
	fd = open(depfile_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (fd == -1) {
		if (errno != ENOENT)
			return -1;

		ret = make_parent_dir(depfile_path);
		if (ret)
			return ret;

		/* Try it again. */
		fd = open(depfile_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
		if (fd == -1)
			return -1;
	}
	close(fd);

	return 0;
}

static void conf_warning(const char *fmt, ...)
	__attribute__ ((format (printf, 1, 2)));

static void conf_message(const char *fmt, ...)
	__attribute__ ((format (printf, 1, 2)));

static const char *conf_filename;
static int conf_lineno, conf_warnings;

static void conf_warning(const char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);
	fprintf(stderr, "%s:%d:warning: ", conf_filename, conf_lineno);
	vfprintf(stderr, fmt, ap);
	fprintf(stderr, "\n");
	va_end(ap);
	conf_warnings++;
}

static void conf_default_message_callback(const char *s)
{
	printf("#\n# ");
	printf("%s", s);
	printf("\n#\n");
}

static void (*conf_message_callback)(const char *s) =
	conf_default_message_callback;
void conf_set_message_callback(void (*fn)(const char *s))
{
	conf_message_callback = fn;
}

static void conf_message(const char *fmt, ...)
{
	va_list ap;
	char buf[4096];

	if (!conf_message_callback)
		return;

	va_start(ap, fmt);

	vsnprintf(buf, sizeof(buf), fmt, ap);
	conf_message_callback(buf);
	va_end(ap);
}

const char *conf_get_configname(void)
{
	char *name = getenv("KCONFIG_CONFIG");

	return name ? name : ".config";
}

static const char *conf_get_autoconfig_name(void)
{
	char *name = getenv("KCONFIG_AUTOCONFIG");

	return name ? name : "include/config/auto.conf";
}

static const char *conf_get_autoheader_name(void)
{
	char *name = getenv("KCONFIG_AUTOHEADER");

	return name ? name : "include/generated/autoconf.h";
}

static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
{
	char *p2;

	switch (sym->type) {
	case S_TRISTATE:
		if (p[0] == 'm') {
			sym->def[def].tri = mod;
			sym->flags |= def_flags;
			break;
		}
		/* fall through */
	case S_BOOLEAN:
		if (p[0] == 'y') {
			sym->def[def].tri = yes;
			sym->flags |= def_flags;
			break;
		}
		if (p[0] == 'n') {
			sym->def[def].tri = no;
			sym->flags |= def_flags;
			break;
		}
		if (def != S_DEF_AUTO)
			conf_warning("symbol value '%s' invalid for %s",
				     p, sym->name);
		return 1;
	case S_STRING:
		if (*p++ != '"')
			break;
		for (p2 = p; (p2 = strpbrk(p2, "\"\\")); p2++) {
			if (*p2 == '"') {
				*p2 = 0;
				break;
			}
			memmove(p2, p2 + 1, strlen(p2));
		}
		if (!p2) {
			if (def != S_DEF_AUTO)
				conf_warning("invalid string found");
			return 1;
		}
		/* fall through */
	case S_INT:
	case S_HEX:
		if (sym_string_valid(sym, p)) {
			sym->def[def].val = xstrdup(p);
			sym->flags |= def_flags;
		} else {
			if (def != S_DEF_AUTO)
				conf_warning("symbol value '%s' invalid for %s",
					     p, sym->name);
			return 1;
		}
		break;
	default:
		;
	}
	return 0;
}

#define LINE_GROWTH 16
static int add_byte(int c, char **lineptr, size_t slen, size_t *n)
{
	char *nline;
	size_t new_size = slen + 1;
	if (new_size > *n) {
		new_size += LINE_GROWTH - 1;
		new_size *= 2;
		nline = xrealloc(*lineptr, new_size);
		if (!nline)
			return -1;

		*lineptr = nline;
		*n = new_size;
	}

	(*lineptr)[slen] = c;

	return 0;
}

static ssize_t compat_getline(char **lineptr, size_t *n, FILE *stream)
{
	char *line = *lineptr;
	size_t slen = 0;

	for (;;) {
		int c = getc(stream);

		switch (c) {
		case '\n':
			if (add_byte(c, &line, slen, n) < 0)
				goto e_out;
			slen++;
			/* fall through */
		case EOF:
			if (add_byte('\0', &line, slen, n) < 0)
				goto e_out;
			*lineptr = line;
			if (slen == 0)
				return -1;
			return slen;
		default:
			if (add_byte(c, &line, slen, n) < 0)
				goto e_out;
			slen++;
		}
	}

e_out:
	line[slen-1] = '\0';
	*lineptr = line;
	return -1;
}

int conf_read_simple(const char *name, int def)
{
	FILE *in = NULL;
	char   *line = NULL;
	size_t  line_asize = 0;
	char *p, *p2;
	struct symbol *sym;
	int i, def_flags;

	if (name) {
		in = zconf_fopen(name);
	} else {
		char *env;

		name = conf_get_configname();
		in = zconf_fopen(name);
		if (in)
			goto load;
		conf_set_changed(true);

		env = getenv("KCONFIG_DEFCONFIG_LIST");
		if (!env)
			return 1;

		while (1) {
			bool is_last;

			while (isspace(*env))
				env++;

			if (!*env)
				break;

			p = env;
			while (*p && !isspace(*p))
				p++;

			is_last = (*p == '\0');

			*p = '\0';

			in = zconf_fopen(env);
			if (in) {
				conf_message("using defaults found in %s",
					     env);
				goto load;
			}

			if (is_last)
				break;

			env = p + 1;
		}
	}
	if (!in)
		return 1;

load:
	conf_filename = name;
	conf_lineno = 0;
	conf_warnings = 0;

	def_flags = SYMBOL_DEF << def;
	for_all_symbols(i, sym) {
		sym->flags |= SYMBOL_CHANGED;
		sym->flags &= ~(def_flags|SYMBOL_VALID);
		if (sym_is_choice(sym))
			sym->flags |= def_flags;
		switch (sym->type) {
		case S_INT:
		case S_HEX:
		case S_STRING:
			if (sym->def[def].val)
				free(sym->def[def].val);
			/* fall through */
		default:
			sym->def[def].val = NULL;
			sym->def[def].tri = no;
		}
	}

	while (compat_getline(&line, &line_asize, in) != -1) {
		conf_lineno++;
		sym = NULL;
		if (line[0] == '#') {
			if (memcmp(line + 2, CONFIG_, strlen(CONFIG_)))
				continue;
			p = strchr(line + 2 + strlen(CONFIG_), ' ');
			if (!p)
				continue;
			*p++ = 0;
			if (strncmp(p, "is not set", 10))
				continue;
			if (def == S_DEF_USER) {
				sym = sym_find(line + 2 + strlen(CONFIG_));
				if (!sym) {
					conf_set_changed(true);
					continue;
				}
			} else {
				sym = sym_lookup(line + 2 + strlen(CONFIG_), 0);
				if (sym->type == S_UNKNOWN)
					sym->type = S_BOOLEAN;
			}
			if (sym->flags & def_flags) {
				conf_warning("override: reassigning to symbol %s", sym->name);
			}
			switch (sym->type) {
			case S_BOOLEAN:
			case S_TRISTATE:
				sym->def[def].tri = no;
				sym->flags |= def_flags;
				break;
			default:
				;
			}
		} else if (memcmp(line, CONFIG_, strlen(CONFIG_)) == 0) {
			p = strchr(line + strlen(CONFIG_), '=');
			if (!p)
				continue;
			*p++ = 0;
			p2 = strchr(p, '\n');
			if (p2) {
				*p2-- = 0;
				if (*p2 == '\r')
					*p2 = 0;
			}

			sym = sym_find(line + strlen(CONFIG_));
			if (!sym) {
				if (def == S_DEF_AUTO)
					/*
					 * Reading from include/config/auto.conf
					 * If CONFIG_FOO previously existed in
					 * auto.conf but it is missing now,
					 * include/config/FOO must be touched.
					 */
					conf_touch_dep(line + strlen(CONFIG_));
				else
					conf_set_changed(true);
				continue;
			}

			if (sym->flags & def_flags) {
				conf_warning("override: reassigning to symbol %s", sym->name);
			}
			if (conf_set_sym_val(sym, def, def_flags, p))
				continue;
		} else {
			if (line[0] != '\r' && line[0] != '\n')
				conf_warning("unexpected data: %.*s",
					     (int)strcspn(line, "\r\n"), line);

			continue;
		}

		if (sym && sym_is_choice_value(sym)) {
			struct symbol *cs = prop_get_symbol(sym_get_choice_prop(sym));
			switch (sym->def[def].tri) {
			case no:
				break;
			case mod:
				if (cs->def[def].tri == yes) {
					conf_warning("%s creates inconsistent choice state", sym->name);
					cs->flags &= ~def_flags;
				}
				break;
			case yes:
				if (cs->def[def].tri != no)
					conf_warning("override: %s changes choice state", sym->name);
				cs->def[def].val = sym;
				break;
			}
			cs->def[def].tri = EXPR_OR(cs->def[def].tri, sym->def[def].tri);
		}
	}
	free(line);
	fclose(in);
	return 0;
}

int conf_read(const char *name)
{
	struct symbol *sym;
	int conf_unsaved = 0;
	int i;

	conf_set_changed(false);

	if (conf_read_simple(name, S_DEF_USER)) {
		sym_calc_value(modules_sym);
		return 1;
	}

	sym_calc_value(modules_sym);

	for_all_symbols(i, sym) {
		sym_calc_value(sym);
		if (sym_is_choice(sym) || (sym->flags & SYMBOL_NO_WRITE))
			continue;
		if (sym_has_value(sym) && (sym->flags & SYMBOL_WRITE)) {
			/* check that calculated value agrees with saved value */
			switch (sym->type) {
			case S_BOOLEAN:
			case S_TRISTATE:
				if (sym->def[S_DEF_USER].tri == sym_get_tristate_value(sym))
					continue;
				break;
			default:
				if (!strcmp(sym->curr.val, sym->def[S_DEF_USER].val))
					continue;
				break;
			}
		} else if (!sym_has_value(sym) && !(sym->flags & SYMBOL_WRITE))
			/* no previous value and not saved */
			continue;
		conf_unsaved++;
		/* maybe print value in verbose mode... */
	}

	for_all_symbols(i, sym) {
		if (sym_has_value(sym) && !sym_is_choice_value(sym)) {
			/* Reset values of generates values, so they'll appear
			 * as new, if they should become visible, but that
			 * doesn't quite work if the Kconfig and the saved
			 * configuration disagree.
			 */
			if (sym->visible == no && !conf_unsaved)
				sym->flags &= ~SYMBOL_DEF_USER;
			switch (sym->type) {
			case S_STRING:
			case S_INT:
			case S_HEX:
				/* Reset a string value if it's out of range */
				if (sym_string_within_range(sym, sym->def[S_DEF_USER].val))
					break;
				sym->flags &= ~(SYMBOL_VALID|SYMBOL_DEF_USER);
				conf_unsaved++;
				break;
			default:
				break;
			}
		}
	}

	if (conf_warnings || conf_unsaved)
		conf_set_changed(true);

	return 0;
}

struct comment_style {
	const char *decoration;
	const char *prefix;
	const char *postfix;
};

static const struct comment_style comment_style_pound = {
	.decoration = "#",
	.prefix = "#",
	.postfix = "#",
};

static const struct comment_style comment_style_c = {
	.decoration = " *",
	.prefix = "/*",
	.postfix = " */",
};

static void conf_write_heading(FILE *fp, const struct comment_style *cs)
{
	fprintf(fp, "%s\n", cs->prefix);

	fprintf(fp, "%s Automatically generated file; DO NOT EDIT.\n",
		cs->decoration);

	fprintf(fp, "%s %s\n", cs->decoration, rootmenu.prompt->text);

	fprintf(fp, "%s\n", cs->postfix);
}

/* The returned pointer must be freed on the caller side */
static char *escape_string_value(const char *in)
{
	const char *p;
	char *out;
	size_t len;

	len = strlen(in) + strlen("\"\"") + 1;

	p = in;
	while (1) {
		p += strcspn(p, "\"\\");

		if (p[0] == '\0')
			break;

		len++;
		p++;
	}

	out = xmalloc(len);
	out[0] = '\0';

	strcat(out, "\"");

	p = in;
	while (1) {
		len = strcspn(p, "\"\\");
		strncat(out, p, len);
		p += len;

		if (p[0] == '\0')
			break;

		strcat(out, "\\");
		strncat(out, p++, 1);
	}

	strcat(out, "\"");

	return out;
}

/*
 * Kconfig configuration printer
 *
 * This printer is used when generating the resulting configuration after
 * kconfig invocation and `defconfig' files. Unset symbol might be omitted by
 * passing a non-NULL argument to the printer.
 */
enum output_n { OUTPUT_N, OUTPUT_N_AS_UNSET, OUTPUT_N_NONE };

static void __print_symbol(FILE *fp, struct symbol *sym, enum output_n output_n,
			   bool escape_string)
{
	const char *val;
	char *escaped = NULL;

	if (sym->type == S_UNKNOWN)
		return;

	val = sym_get_string_value(sym);

	if ((sym->type == S_BOOLEAN || sym->type == S_TRISTATE) &&
	    output_n != OUTPUT_N && *val == 'n') {
		if (output_n == OUTPUT_N_AS_UNSET)
			fprintf(fp, "# %s%s is not set\n", CONFIG_, sym->name);
		return;
	}

	if (sym->type == S_STRING && escape_string) {
		escaped = escape_string_value(val);
		val = escaped;
	}

	fprintf(fp, "%s%s=%s\n", CONFIG_, sym->name, val);

	free(escaped);
}

static void print_symbol_for_dotconfig(FILE *fp, struct symbol *sym)
{
	__print_symbol(fp, sym, OUTPUT_N_AS_UNSET, true);
}

static void print_symbol_for_autoconf(FILE *fp, struct symbol *sym)
{
	__print_symbol(fp, sym, OUTPUT_N_NONE, true);
}

void print_symbol_for_listconfig(struct symbol *sym)
{
	__print_symbol(stdout, sym, OUTPUT_N, true);
}

static void print_symbol_for_c(FILE *fp, struct symbol *sym)
{
	const char *val;
	const char *sym_suffix = "";
	const char *val_prefix = "";
	char *escaped = NULL;

	if (sym->type == S_UNKNOWN)
		return;

	val = sym_get_string_value(sym);

	switch (sym->type) {
	case S_BOOLEAN:
	case S_TRISTATE:
		switch (*val) {
		case 'n':
			return;
		case 'm':
			sym_suffix = "_MODULE";
			/* fall through */
		default:
			val = "1";
		}
		break;
	case S_HEX:
		if (val[0] != '0' || (val[1] != 'x' && val[1] != 'X'))
			val_prefix = "0x";
		break;
	case S_STRING:
		escaped = escape_string_value(val);
		val = escaped;
	default:
		break;
	}

	fprintf(fp, "#define %s%s%s %s%s\n", CONFIG_, sym->name, sym_suffix,
		val_prefix, val);

	free(escaped);
}

/*
 * Write out a minimal config.
 * All values that has default values are skipped as this is redundant.
 */
int conf_write_defconfig(const char *filename)
{
	struct symbol *sym;
	struct menu *menu;
	FILE *out;

	out = fopen(filename, "w");
	if (!out)
		return 1;

	sym_clear_all_valid();

	/* Traverse all menus to find all relevant symbols */
	menu = rootmenu.list;

	while (menu != NULL)
	{
		sym = menu->sym;
		if (sym == NULL) {
			if (!menu_is_visible(menu))
				goto next_menu;
		} else if (!sym_is_choice(sym)) {
			sym_calc_value(sym);
			if (!(sym->flags & SYMBOL_WRITE))
				goto next_menu;
			sym->flags &= ~SYMBOL_WRITE;
			/* If we cannot change the symbol - skip */
			if (!sym_is_changeable(sym))
				goto next_menu;
			/* If symbol equals to default value - skip */
			if (strcmp(sym_get_string_value(sym), sym_get_string_default(sym)) == 0)
				goto next_menu;

			/*
			 * If symbol is a choice value and equals to the
			 * default for a choice - skip.
			 * But only if value is bool and equal to "y" and
			 * choice is not "optional".
			 * (If choice is "optional" then all values can be "n")
			 */
			if (sym_is_choice_value(sym)) {
				struct symbol *cs;
				struct symbol *ds;

				cs = prop_get_symbol(sym_get_choice_prop(sym));
				ds = sym_choice_default(cs);
				if (!sym_is_optional(cs) && sym == ds) {
					if ((sym->type == S_BOOLEAN) &&
					    sym_get_tristate_value(sym) == yes)
						goto next_menu;
				}
			}
			print_symbol_for_dotconfig(out, sym);
		}
next_menu:
		if (menu->list != NULL) {
			menu = menu->list;
		}
		else if (menu->next != NULL) {
			menu = menu->next;
		} else {
			while ((menu = menu->parent)) {
				if (menu->next != NULL) {
					menu = menu->next;
					break;
				}
			}
		}
	}
	fclose(out);
	return 0;
}

int conf_write(const char *name)
{
	FILE *out;
	struct symbol *sym;
	struct menu *menu;
	const char *str;
	char tmpname[PATH_MAX + 1], oldname[PATH_MAX + 1];
	char *env;
	int i;
	bool need_newline = false;

	if (!name)
		name = conf_get_configname();

	if (!*name) {
		fprintf(stderr, "config name is empty\n");
		return -1;
	}

	if (is_dir(name)) {
		fprintf(stderr, "%s: Is a directory\n", name);
		return -1;
	}

	if (make_parent_dir(name))
		return -1;

	env = getenv("KCONFIG_OVERWRITECONFIG");
	if (env && *env) {
		*tmpname = 0;
		out = fopen(name, "w");
	} else {
		snprintf(tmpname, sizeof(tmpname), "%s.%d.tmp",
			 name, (int)getpid());
		out = fopen(tmpname, "w");
	}
	if (!out)
		return 1;

	conf_write_heading(out, &comment_style_pound);

	if (!conf_get_changed())
		sym_clear_all_valid();

	menu = rootmenu.list;
	while (menu) {
		sym = menu->sym;
		if (!sym) {
			if (!menu_is_visible(menu))
				goto next;
			str = menu_get_prompt(menu);
			fprintf(out, "\n"
				     "#\n"
				     "# %s\n"
				     "#\n", str);
			need_newline = false;
		} else if (!(sym->flags & SYMBOL_CHOICE) &&
			   !(sym->flags & SYMBOL_WRITTEN)) {
			sym_calc_value(sym);
			if (!(sym->flags & SYMBOL_WRITE))
				goto next;
			if (need_newline) {
				fprintf(out, "\n");
				need_newline = false;
			}
			sym->flags |= SYMBOL_WRITTEN;
			print_symbol_for_dotconfig(out, sym);
		}

next:
		if (menu->list) {
			menu = menu->list;
			continue;
		}
		if (menu->next)
			menu = menu->next;
		else while ((menu = menu->parent)) {
			if (!menu->sym && menu_is_visible(menu) &&
			    menu != &rootmenu) {
				str = menu_get_prompt(menu);
				fprintf(out, "# end of %s\n", str);
				need_newline = true;
			}
			if (menu->next) {
				menu = menu->next;
				break;
			}
		}
	}
	fclose(out);

	for_all_symbols(i, sym)
		sym->flags &= ~SYMBOL_WRITTEN;

	if (*tmpname) {
		if (is_same(name, tmpname)) {
			conf_message("No change to %s", name);
			unlink(tmpname);
			conf_set_changed(false);
			return 0;
		}

		snprintf(oldname, sizeof(oldname), "%s.old", name);
		rename(name, oldname);
		if (rename(tmpname, name))
			return 1;
	}

	conf_message("configuration written to %s", name);

	conf_set_changed(false);

	return 0;
}

/* write a dependency file as used by kbuild to track dependencies */
static int conf_write_dep(const char *name)
{
	struct file *file;
	FILE *out;

	out = fopen("..config.tmp", "w");
	if (!out)
		return 1;
	fprintf(out, "deps_config := \\\n");
	for (file = file_list; file; file = file->next) {
		if (file->next)
			fprintf(out, "\t%s \\\n", file->name);
		else
			fprintf(out, "\t%s\n", file->name);
	}
	fprintf(out, "\n%s: \\\n"
		     "\t$(deps_config)\n\n", conf_get_autoconfig_name());

	env_write_dep(out, conf_get_autoconfig_name());

	fprintf(out, "\n$(deps_config): ;\n");
	fclose(out);

	if (make_parent_dir(name))
		return 1;
	rename("..config.tmp", name);
	return 0;
}

static int conf_touch_deps(void)
{
	const char *name;
	struct symbol *sym;
	int res, i;

	strcpy(depfile_path, "include/config/");
	depfile_prefix_len = strlen(depfile_path);

	name = conf_get_autoconfig_name();
	conf_read_simple(name, S_DEF_AUTO);
	sym_calc_value(modules_sym);

	for_all_symbols(i, sym) {
		sym_calc_value(sym);
		if ((sym->flags & SYMBOL_NO_WRITE) || !sym->name)
			continue;
		if (sym->flags & SYMBOL_WRITE) {
			if (sym->flags & SYMBOL_DEF_AUTO) {
				/*
				 * symbol has old and new value,
				 * so compare them...
				 */
				switch (sym->type) {
				case S_BOOLEAN:
				case S_TRISTATE:
					if (sym_get_tristate_value(sym) ==
					    sym->def[S_DEF_AUTO].tri)
						continue;
					break;
				case S_STRING:
				case S_HEX:
				case S_INT:
					if (!strcmp(sym_get_string_value(sym),
						    sym->def[S_DEF_AUTO].val))
						continue;
					break;
				default:
					break;
				}
			} else {
				/*
				 * If there is no old value, only 'no' (unset)
				 * is allowed as new value.
				 */
				switch (sym->type) {
				case S_BOOLEAN:
				case S_TRISTATE:
					if (sym_get_tristate_value(sym) == no)
						continue;
					break;
				default:
					break;
				}
			}
		} else if (!(sym->flags & SYMBOL_DEF_AUTO))
			/* There is neither an old nor a new value. */
			continue;
		/* else
		 *	There is an old value, but no new value ('no' (unset)
		 *	isn't saved in auto.conf, so the old value is always
		 *	different from 'no').
		 */

		res = conf_touch_dep(sym->name);
		if (res)
			return res;
	}

	return 0;
}

static int __conf_write_autoconf(const char *filename,
				 void (*print_symbol)(FILE *, struct symbol *),
				 const struct comment_style *comment_style)
{
	char tmp[PATH_MAX];
	FILE *file;
	struct symbol *sym;
	int ret, i;

	if (make_parent_dir(filename))
		return -1;

	ret = snprintf(tmp, sizeof(tmp), "%s.tmp", filename);
	if (ret >= sizeof(tmp)) /* check truncation */
		return -1;

	file = fopen(tmp, "w");
	if (!file) {
		perror("fopen");
		return -1;
	}

	conf_write_heading(file, comment_style);

	for_all_symbols(i, sym)
		if ((sym->flags & SYMBOL_WRITE) && sym->name)
			print_symbol(file, sym);

	/* check possible errors in conf_write_heading() and print_symbol() */
	if (ferror(file))
		return -1;

	fclose(file);

	if (rename(tmp, filename)) {
		perror("rename");
		return -1;
	}

	return 0;
}

int conf_write_autoconf(int overwrite)
{
	struct symbol *sym;
	const char *autoconf_name = conf_get_autoconfig_name();
	int ret, i;

	if (!overwrite && is_present(autoconf_name))
		return 0;

	conf_write_dep("include/config/auto.conf.cmd");

	if (conf_touch_deps())
		return 1;

	for_all_symbols(i, sym)
		sym_calc_value(sym);

	ret = __conf_write_autoconf(conf_get_autoheader_name(),
				    print_symbol_for_c,
				    &comment_style_c);
	if (ret)
		return ret;

	/*
	 * Create include/config/auto.conf. This must be the last step because
	 * Kbuild has a dependency on auto.conf and this marks the successful
	 * completion of the previous steps.
	 */
	ret = __conf_write_autoconf(conf_get_autoconfig_name(),
				    print_symbol_for_autoconf,
				    &comment_style_pound);
	if (ret)
		return ret;

	return 0;
}

static bool conf_changed;
static void (*conf_changed_callback)(void);

void conf_set_changed(bool val)
{
	if (conf_changed_callback && conf_changed != val)
		conf_changed_callback();

	conf_changed = val;
}

bool conf_get_changed(void)
{
	return conf_changed;
}

void conf_set_changed_callback(void (*fn)(void))
{
	conf_changed_callback = fn;
}

void set_all_choice_values(struct symbol *csym)
{
	struct property *prop;
	struct symbol *sym;
	struct expr *e;

	prop = sym_get_choice_prop(csym);

	/*
	 * Set all non-assinged choice values to no
	 */
	expr_list_for_each_sym(prop->expr, e, sym) {
		if (!sym_has_value(sym))
			sym->def[S_DEF_USER].tri = no;
	}
	csym->flags |= SYMBOL_DEF_USER;
	/* clear VALID to get value calculated */
	csym->flags &= ~(SYMBOL_VALID | SYMBOL_NEED_SET_CHOICE_VALUES);
}