Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 1241 insertions, 0 deletions

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
new file mode 100644
index 000000000..4234a51d1
--- /dev/null
+++ b/scripts/kconfig/confdata.c
@@ -0,0 +1,1241 @@
+// 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 <xalloc.h>
+#include "internal.h"
+#include "lkc.h"
+
+struct gstr autoconf_cmd;
+
+/* 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 (memcmp(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;
+
+	/* check overflow: prefix + name + '\0' must fit in buffer. */
+	if (depfile_prefix_len + strlen(name) + 1 > sizeof(depfile_path))
+		return -1;
+
+	strcpy(depfile_path + depfile_prefix_len, name);
+
+	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;
+
+bool conf_errors(void)
+{
+	if (conf_warnings)
+		return getenv("KCONFIG_WERROR");
+	return false;
+}
+
+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);
+}
+
+static void conf_changed_input_warning(const char *s)
+{
+	fputs(s, stderr);
+}
+
+static bool conf_warn_changed_input_enabled(void)
+{
+	const char *env = getenv("KCONFIG_WARN_CHANGED_INPUT");
+
+	return env && *env;
+}
+
+static const char *sym_get_user_value_string(struct symbol *sym)
+{
+	switch (sym->type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		switch (sym->def[S_DEF_USER].tri) {
+		case yes:
+			return "y";
+		case mod:
+			return "m";
+		default:
+			return "n";
+		}
+	default:
+		return sym->def[S_DEF_USER].val ?: "";
+	}
+}
+
+static bool sym_user_value_changed(struct symbol *sym)
+{
+	if (!sym_has_value(sym) || sym->type == S_UNKNOWN)
+		return false;
+
+	switch (sym->type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		return sym->def[S_DEF_USER].tri != sym_get_tristate_value(sym);
+	default:
+		return strcmp(sym_get_user_value_string(sym),
+			      sym_get_string_value(sym));
+	}
+}
+
+static void conf_clear_written_flags(void)
+{
+	struct symbol *sym;
+
+	for_all_symbols(sym)
+		sym->flags &= ~SYMBOL_WRITTEN;
+}
+
+static void conf_append_changed_input_warning(struct gstr *gs,
+					      struct symbol *sym,
+					      bool *changed_input_found)
+{
+	if (!sym_user_value_changed(sym))
+		return;
+
+	if (!*changed_input_found) {
+		str_printf(gs,
+			   "warning: user-provided values changed by Kconfig:\n");
+		*changed_input_found = true;
+	}
+
+	str_printf(gs, "  %s%s: %s -> %s\n",
+		   CONFIG_, sym->name,
+		   sym_get_user_value_string(sym),
+		   sym_get_string_value(sym));
+}
+
+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 const char *conf_get_rustccfg_name(void)
+{
+	char *name = getenv("KCONFIG_RUSTCCFG");
+
+	return name ? name : "include/generated/rustc_cfg";
+}
+
+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:
+		/* No escaping for S_DEF_AUTO (include/config/auto.conf) */
+		if (def != S_DEF_AUTO) {
+			if (*p++ != '"')
+				break;
+			for (p2 = p; (p2 = strpbrk(p2, "\"\\")); p2++) {
+				if (*p2 == '"') {
+					*p2 = 0;
+					break;
+				}
+				memmove(p2, p2 + 1, strlen(p2));
+			}
+			if (!p2) {
+				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;
+}
+
+/* like getline(), but the newline character is stripped away */
+static ssize_t getline_stripped(char **lineptr, size_t *n, FILE *stream)
+{
+	ssize_t len;
+
+	len = getline(lineptr, n, stream);
+
+	if (len > 0 && (*lineptr)[len - 1] == '\n') {
+		len--;
+		(*lineptr)[len] = '\0';
+
+		if (len > 0 && (*lineptr)[len - 1] == '\r') {
+			len--;
+			(*lineptr)[len] = '\0';
+		}
+	}
+
+	return len;
+}
+
+int conf_read_simple(const char *name, int def)
+{
+	FILE *in = NULL;
+	char   *line = NULL;
+	size_t  line_asize = 0;
+	char *p, *val;
+	struct symbol *sym;
+	int def_flags;
+	const char *warn_unknown, *sym_name;
+
+	warn_unknown = getenv("KCONFIG_WARN_UNKNOWN_SYMBOLS");
+	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';
+
+			name = env;
+
+			in = zconf_fopen(name);
+			if (in) {
+				conf_message("using defaults found in %s",
+					     name);
+				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(sym) {
+		sym->flags &= ~def_flags;
+		switch (sym->type) {
+		case S_INT:
+		case S_HEX:
+		case S_STRING:
+			free(sym->def[def].val);
+			/* fall through */
+		default:
+			sym->def[def].val = NULL;
+			sym->def[def].tri = no;
+		}
+	}
+
+	if (def == S_DEF_USER) {
+		for_all_symbols(sym)
+			sym->flags &= ~SYMBOL_VALID;
+		expr_invalidate_all();
+	}
+
+	while (getline_stripped(&line, &line_asize, in) != -1) {
+		struct menu *choice;
+
+		conf_lineno++;
+
+		if (!line[0]) /* blank line */
+			continue;
+
+		if (line[0] == '#') {
+			if (line[1] != ' ')
+				continue;
+			p = line + 2;
+			if (memcmp(p, CONFIG_, strlen(CONFIG_)))
+				continue;
+			sym_name = p + strlen(CONFIG_);
+			p = strchr(sym_name, ' ');
+			if (!p)
+				continue;
+			*p++ = 0;
+			if (strcmp(p, "is not set"))
+				continue;
+
+			val = "n";
+		} else {
+			if (memcmp(line, CONFIG_, strlen(CONFIG_))) {
+				conf_warning("unexpected data: %s", line);
+				continue;
+			}
+
+			sym_name = line + strlen(CONFIG_);
+			p = strchr(sym_name, '=');
+			if (!p) {
+				conf_warning("unexpected data: %s", line);
+				continue;
+			}
+			*p = 0;
+			val = p + 1;
+		}
+
+		sym = sym_find(sym_name);
+		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(sym_name);
+			} else {
+				if (warn_unknown)
+					conf_warning("unknown symbol: %s", sym_name);
+
+				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, val))
+			continue;
+
+		if (def != S_DEF_USER)
+			continue;
+
+		/*
+		 * If this is a choice member, give it the highest priority.
+		 * If conflicting CONFIG options are given from an input file,
+		 * the last one wins.
+		 */
+		choice = sym_get_choice_menu(sym);
+		if (choice)
+			list_move(&sym->choice_link, &choice->choice_members);
+	}
+	free(line);
+	fclose(in);
+
+	return 0;
+}
+
+int conf_read(const char *name)
+{
+	struct symbol *sym;
+
+	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(sym) {
+		sym_calc_value(sym);
+		if (sym_is_choice(sym))
+			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_set_changed(true);
+		/* maybe print value in verbose mode... */
+	}
+
+	if (conf_warnings)
+		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)
+{
+	if (!cs)
+		return;
+
+	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;
+}
+
+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, false);
+}
+
+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);
+}
+
+static void print_symbol_for_rustccfg(FILE *fp, struct symbol *sym)
+{
+	const char *val;
+	const char *val_prefix = "";
+	char *val_prefixed = NULL;
+	size_t val_prefixed_len;
+	char *escaped = NULL;
+
+	if (sym->type == S_UNKNOWN)
+		return;
+
+	val = sym_get_string_value(sym);
+
+	switch (sym->type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		/*
+		 * We do not care about disabled ones, i.e. no need for
+		 * what otherwise are "comments" in other printers.
+		 */
+		if (*val == 'n')
+			return;
+
+		/*
+		 * To have similar functionality to the C macro `IS_ENABLED()`
+		 * we provide an empty `--cfg CONFIG_X` here in both `y`
+		 * and `m` cases.
+		 *
+		 * Then, the common `fprintf()` below will also give us
+		 * a `--cfg CONFIG_X="y"` or `--cfg CONFIG_X="m"`, which can
+		 * be used as the equivalent of `IS_BUILTIN()`/`IS_MODULE()`.
+		 */
+		fprintf(fp, "--cfg=%s%s\n", CONFIG_, sym->name);
+		break;
+	case S_HEX:
+		if (val[0] != '0' || (val[1] != 'x' && val[1] != 'X'))
+			val_prefix = "0x";
+		break;
+	default:
+		break;
+	}
+
+	if (strlen(val_prefix) > 0) {
+		val_prefixed_len = strlen(val) + strlen(val_prefix) + 1;
+		val_prefixed = xmalloc(val_prefixed_len);
+		snprintf(val_prefixed, val_prefixed_len, "%s%s", val_prefix, val);
+		val = val_prefixed;
+	}
+
+	/* All values get escaped: the `--cfg` option only takes strings */
+	escaped = escape_string_value(val);
+	val = escaped;
+
+	fprintf(fp, "--cfg=%s%s=%s\n", CONFIG_, sym->name, val);
+
+	free(escaped);
+	free(val_prefixed);
+}
+
+/*
+ * 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;
+	struct gstr gs;
+	FILE *out;
+	bool warn_changed_input = conf_warn_changed_input_enabled();
+	bool changed_input_found = false;
+
+	out = fopen(filename, "w");
+	if (!out)
+		return 1;
+	gs = str_new();
+
+	sym_clear_all_valid();
+
+	menu_for_each_entry(menu) {
+		struct menu *choice;
+
+		sym = menu->sym;
+
+		if (!sym || sym_is_choice(sym) || sym->flags & SYMBOL_WRITTEN)
+			continue;
+
+		sym_calc_value(sym);
+		if (warn_changed_input)
+			conf_append_changed_input_warning(&gs, sym,
+							  &changed_input_found);
+		sym->flags |= SYMBOL_WRITTEN;
+		if (!(sym->flags & SYMBOL_WRITE))
+			continue;
+		sym->flags &= ~SYMBOL_WRITE;
+		/* Skip unchangeable symbols */
+		if (!sym_is_changeable(sym))
+			continue;
+		/* Skip symbols that are equal to the default */
+		if (!strcmp(sym_get_string_value(sym), sym_get_string_default(sym)))
+			continue;
+
+		/* Skip choice values that are equal to the default */
+		choice = sym_get_choice_menu(sym);
+		if (choice) {
+			struct symbol *ds;
+
+			ds = sym_choice_default(choice);
+			if (sym == ds && sym_get_tristate_value(sym) == yes)
+				continue;
+		}
+		print_symbol_for_dotconfig(out, sym);
+	}
+	fclose(out);
+
+	conf_clear_written_flags();
+
+	if (changed_input_found)
+		conf_changed_input_warning(str_get(&gs));
+
+	str_free(&gs);
+	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;
+	struct gstr gs;
+	bool need_newline = false;
+	bool warn_changed_input = conf_warn_changed_input_enabled();
+	bool changed_input_found = 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;
+	gs = str_new();
+
+	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_is_choice(sym) &&
+			   !(sym->flags & SYMBOL_WRITTEN)) {
+			sym_calc_value(sym);
+			if (warn_changed_input)
+				conf_append_changed_input_warning(&gs, sym,
+								  &changed_input_found);
+			sym->flags |= SYMBOL_WRITTEN;
+			if (!(sym->flags & SYMBOL_WRITE))
+				goto next;
+			if (need_newline) {
+				fprintf(out, "\n");
+				need_newline = false;
+			}
+			print_symbol_for_dotconfig(out, sym);
+		}
+
+next:
+		if (menu->list) {
+			menu = menu->list;
+			continue;
+		}
+
+end_check:
+		if (!menu->sym && menu_is_visible(menu) && menu != &rootmenu &&
+		    menu->prompt->type == P_MENU) {
+			fprintf(out, "# end of %s\n", menu_get_prompt(menu));
+			need_newline = true;
+		}
+
+		if (menu->next) {
+			menu = menu->next;
+		} else {
+			menu = menu->parent;
+			if (menu)
+				goto end_check;
+		}
+	}
+	fclose(out);
+
+	conf_clear_written_flags();
+
+	if (changed_input_found)
+		conf_changed_input_warning(str_get(&gs));
+
+	str_free(&gs);
+
+	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_autoconf_cmd(const char *autoconf_name)
+{
+	char name[PATH_MAX], tmp[PATH_MAX];
+	FILE *out;
+	int ret;
+
+	ret = snprintf(name, sizeof(name), "%s.cmd", autoconf_name);
+	if (ret >= sizeof(name)) /* check truncation */
+		return -1;
+
+	if (make_parent_dir(name))
+		return -1;
+
+	ret = snprintf(tmp, sizeof(tmp), "%s.cmd.tmp", autoconf_name);
+	if (ret >= sizeof(tmp)) /* check truncation */
+		return -1;
+
+	out = fopen(tmp, "w");
+	if (!out) {
+		perror("fopen");
+		return -1;
+	}
+
+	fprintf(out, "autoconfig := %s\n", autoconf_name);
+
+	fputs(str_get(&autoconf_cmd), out);
+
+	fflush(out);
+	ret = ferror(out); /* error check for all fprintf() calls */
+	fclose(out);
+	if (ret)
+		return -1;
+
+	if (rename(tmp, name)) {
+		perror("rename");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int conf_touch_deps(void)
+{
+	const char *name, *tmp;
+	struct symbol *sym;
+	int res;
+
+	name = conf_get_autoconfig_name();
+	tmp = strrchr(name, '/');
+	depfile_prefix_len = tmp ? tmp - name + 1 : 0;
+	if (depfile_prefix_len + 1 > sizeof(depfile_path))
+		return -1;
+
+	strncpy(depfile_path, name, depfile_prefix_len);
+	depfile_path[depfile_prefix_len] = 0;
+
+	conf_read_simple(name, S_DEF_AUTO);
+
+	for_all_symbols(sym) {
+		if (sym_is_choice(sym))
+			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;
+
+	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(sym)
+		if ((sym->flags & SYMBOL_WRITE) && sym->name)
+			print_symbol(file, sym);
+
+	fflush(file);
+	/* check possible errors in conf_write_heading() and print_symbol() */
+	ret = ferror(file);
+	fclose(file);
+	if (ret)
+		return -1;
+
+	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;
+
+	if (!overwrite && is_present(autoconf_name))
+		return 0;
+
+	ret = conf_write_autoconf_cmd(autoconf_name);
+	if (ret)
+		return -1;
+
+	for_all_symbols(sym)
+		sym_calc_value(sym);
+
+	if (conf_touch_deps())
+		return 1;
+
+	ret = __conf_write_autoconf(conf_get_autoheader_name(),
+				    print_symbol_for_c,
+				    &comment_style_c);
+	if (ret)
+		return ret;
+
+	ret = __conf_write_autoconf(conf_get_rustccfg_name(),
+				    print_symbol_for_rustccfg,
+				    NULL);
+	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)(bool);
+
+void conf_set_changed(bool val)
+{
+	if (conf_changed_callback && conf_changed != val)
+		conf_changed_callback(val);
+
+	conf_changed = val;
+}
+
+bool conf_get_changed(void)
+{
+	return conf_changed;
+}
+
+void conf_set_changed_callback(void (*fn)(bool))
+{
+	conf_changed_callback = fn;
+}