diff --git a/Documentation/perf_counter/config.c b/Documentation/perf_counter/config.c
new file mode 100644
index 0000000..672d539
--- /dev/null
+++ b/Documentation/perf_counter/config.c
@@ -0,0 +1,966 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ * Copyright (C) Johannes Schindelin, 2005
+ *
+ */
+#include "util.h"
+#include "cache.h"
+#include "exec_cmd.h"
+
+#define MAXNAME (256)
+
+static FILE *config_file;
+static const char *config_file_name;
+static int config_linenr;
+static int config_file_eof;
+static int zlib_compression_seen;
+
+const char *config_exclusive_filename = NULL;
+
+static int get_next_char(void)
+{
+	int c;
+	FILE *f;
+
+	c = '\n';
+	if ((f = config_file) != NULL) {
+		c = fgetc(f);
+		if (c == '\r') {
+			/* DOS like systems */
+			c = fgetc(f);
+			if (c != '\n') {
+				ungetc(c, f);
+				c = '\r';
+			}
+		}
+		if (c == '\n')
+			config_linenr++;
+		if (c == EOF) {
+			config_file_eof = 1;
+			c = '\n';
+		}
+	}
+	return c;
+}
+
+static char *parse_value(void)
+{
+	static char value[1024];
+	int quote = 0, comment = 0, len = 0, space = 0;
+
+	for (;;) {
+		int c = get_next_char();
+		if (len >= sizeof(value) - 1)
+			return NULL;
+		if (c == '\n') {
+			if (quote)
+				return NULL;
+			value[len] = 0;
+			return value;
+		}
+		if (comment)
+			continue;
+		if (isspace(c) && !quote) {
+			space = 1;
+			continue;
+		}
+		if (!quote) {
+			if (c == ';' || c == '#') {
+				comment = 1;
+				continue;
+			}
+		}
+		if (space) {
+			if (len)
+				value[len++] = ' ';
+			space = 0;
+		}
+		if (c == '\\') {
+			c = get_next_char();
+			switch (c) {
+			case '\n':
+				continue;
+			case 't':
+				c = '\t';
+				break;
+			case 'b':
+				c = '\b';
+				break;
+			case 'n':
+				c = '\n';
+				break;
+			/* Some characters escape as themselves */
+			case '\\': case '"':
+				break;
+			/* Reject unknown escape sequences */
+			default:
+				return NULL;
+			}
+			value[len++] = c;
+			continue;
+		}
+		if (c == '"') {
+			quote = 1-quote;
+			continue;
+		}
+		value[len++] = c;
+	}
+}
+
+static inline int iskeychar(int c)
+{
+	return isalnum(c) || c == '-';
+}
+
+static int get_value(config_fn_t fn, void *data, char *name, unsigned int len)
+{
+	int c;
+	char *value;
+
+	/* Get the full name */
+	for (;;) {
+		c = get_next_char();
+		if (config_file_eof)
+			break;
+		if (!iskeychar(c))
+			break;
+		name[len++] = tolower(c);
+		if (len >= MAXNAME)
+			return -1;
+	}
+	name[len] = 0;
+	while (c == ' ' || c == '\t')
+		c = get_next_char();
+
+	value = NULL;
+	if (c != '\n') {
+		if (c != '=')
+			return -1;
+		value = parse_value();
+		if (!value)
+			return -1;
+	}
+	return fn(name, value, data);
+}
+
+static int get_extended_base_var(char *name, int baselen, int c)
+{
+	do {
+		if (c == '\n')
+			return -1;
+		c = get_next_char();
+	} while (isspace(c));
+
+	/* We require the format to be '[base "extension"]' */
+	if (c != '"')
+		return -1;
+	name[baselen++] = '.';
+
+	for (;;) {
+		int c = get_next_char();
+		if (c == '\n')
+			return -1;
+		if (c == '"')
+			break;
+		if (c == '\\') {
+			c = get_next_char();
+			if (c == '\n')
+				return -1;
+		}
+		name[baselen++] = c;
+		if (baselen > MAXNAME / 2)
+			return -1;
+	}
+
+	/* Final ']' */
+	if (get_next_char() != ']')
+		return -1;
+	return baselen;
+}
+
+static int get_base_var(char *name)
+{
+	int baselen = 0;
+
+	for (;;) {
+		int c = get_next_char();
+		if (config_file_eof)
+			return -1;
+		if (c == ']')
+			return baselen;
+		if (isspace(c))
+			return get_extended_base_var(name, baselen, c);
+		if (!iskeychar(c) && c != '.')
+			return -1;
+		if (baselen > MAXNAME / 2)
+			return -1;
+		name[baselen++] = tolower(c);
+	}
+}
+
+static int perf_parse_file(config_fn_t fn, void *data)
+{
+	int comment = 0;
+	int baselen = 0;
+	static char var[MAXNAME];
+
+	/* U+FEFF Byte Order Mark in UTF8 */
+	static const unsigned char *utf8_bom = (unsigned char *) "\xef\xbb\xbf";
+	const unsigned char *bomptr = utf8_bom;
+
+	for (;;) {
+		int c = get_next_char();
+		if (bomptr && *bomptr) {
+			/* We are at the file beginning; skip UTF8-encoded BOM
+			 * if present. Sane editors won't put this in on their
+			 * own, but e.g. Windows Notepad will do it happily. */
+			if ((unsigned char) c == *bomptr) {
+				bomptr++;
+				continue;
+			} else {
+				/* Do not tolerate partial BOM. */
+				if (bomptr != utf8_bom)
+					break;
+				/* No BOM at file beginning. Cool. */
+				bomptr = NULL;
+			}
+		}
+		if (c == '\n') {
+			if (config_file_eof)
+				return 0;
+			comment = 0;
+			continue;
+		}
+		if (comment || isspace(c))
+			continue;
+		if (c == '#' || c == ';') {
+			comment = 1;
+			continue;
+		}
+		if (c == '[') {
+			baselen = get_base_var(var);
+			if (baselen <= 0)
+				break;
+			var[baselen++] = '.';
+			var[baselen] = 0;
+			continue;
+		}
+		if (!isalpha(c))
+			break;
+		var[baselen] = tolower(c);
+		if (get_value(fn, data, var, baselen+1) < 0)
+			break;
+	}
+	die("bad config file line %d in %s", config_linenr, config_file_name);
+}
+
+static int parse_unit_factor(const char *end, unsigned long *val)
+{
+	if (!*end)
+		return 1;
+	else if (!strcasecmp(end, "k")) {
+		*val *= 1024;
+		return 1;
+	}
+	else if (!strcasecmp(end, "m")) {
+		*val *= 1024 * 1024;
+		return 1;
+	}
+	else if (!strcasecmp(end, "g")) {
+		*val *= 1024 * 1024 * 1024;
+		return 1;
+	}
+	return 0;
+}
+
+static int perf_parse_long(const char *value, long *ret)
+{
+	if (value && *value) {
+		char *end;
+		long val = strtol(value, &end, 0);
+		unsigned long factor = 1;
+		if (!parse_unit_factor(end, &factor))
+			return 0;
+		*ret = val * factor;
+		return 1;
+	}
+	return 0;
+}
+
+int perf_parse_ulong(const char *value, unsigned long *ret)
+{
+	if (value && *value) {
+		char *end;
+		unsigned long val = strtoul(value, &end, 0);
+		if (!parse_unit_factor(end, &val))
+			return 0;
+		*ret = val;
+		return 1;
+	}
+	return 0;
+}
+
+static void die_bad_config(const char *name)
+{
+	if (config_file_name)
+		die("bad config value for '%s' in %s", name, config_file_name);
+	die("bad config value for '%s'", name);
+}
+
+int perf_config_int(const char *name, const char *value)
+{
+	long ret = 0;
+	if (!perf_parse_long(value, &ret))
+		die_bad_config(name);
+	return ret;
+}
+
+unsigned long perf_config_ulong(const char *name, const char *value)
+{
+	unsigned long ret;
+	if (!perf_parse_ulong(value, &ret))
+		die_bad_config(name);
+	return ret;
+}
+
+int perf_config_bool_or_int(const char *name, const char *value, int *is_bool)
+{
+	*is_bool = 1;
+	if (!value)
+		return 1;
+	if (!*value)
+		return 0;
+	if (!strcasecmp(value, "true") || !strcasecmp(value, "yes") || !strcasecmp(value, "on"))
+		return 1;
+	if (!strcasecmp(value, "false") || !strcasecmp(value, "no") || !strcasecmp(value, "off"))
+		return 0;
+	*is_bool = 0;
+	return perf_config_int(name, value);
+}
+
+int perf_config_bool(const char *name, const char *value)
+{
+	int discard;
+	return !!perf_config_bool_or_int(name, value, &discard);
+}
+
+int perf_config_string(const char **dest, const char *var, const char *value)
+{
+	if (!value)
+		return config_error_nonbool(var);
+	*dest = strdup(value);
+	return 0;
+}
+
+static int perf_default_core_config(const char *var, const char *value)
+{
+	/* Add other config variables here and to Documentation/config.txt. */
+	return 0;
+}
+
+int perf_default_config(const char *var, const char *value, void *dummy)
+{
+	if (!prefixcmp(var, "core."))
+		return perf_default_core_config(var, value);
+
+	/* Add other config variables here and to Documentation/config.txt. */
+	return 0;
+}
+
+int perf_config_from_file(config_fn_t fn, const char *filename, void *data)
+{
+	int ret;
+	FILE *f = fopen(filename, "r");
+
+	ret = -1;
+	if (f) {
+		config_file = f;
+		config_file_name = filename;
+		config_linenr = 1;
+		config_file_eof = 0;
+		ret = perf_parse_file(fn, data);
+		fclose(f);
+		config_file_name = NULL;
+	}
+	return ret;
+}
+
+const char *perf_etc_perfconfig(void)
+{
+	static const char *system_wide;
+	if (!system_wide)
+		system_wide = system_path(ETC_PERFCONFIG);
+	return system_wide;
+}
+
+static int perf_env_bool(const char *k, int def)
+{
+	const char *v = getenv(k);
+	return v ? perf_config_bool(k, v) : def;
+}
+
+int perf_config_system(void)
+{
+	return !perf_env_bool("PERF_CONFIG_NOSYSTEM", 0);
+}
+
+int perf_config_global(void)
+{
+	return !perf_env_bool("PERF_CONFIG_NOGLOBAL", 0);
+}
+
+int perf_config(config_fn_t fn, void *data)
+{
+	int ret = 0, found = 0;
+	char *repo_config = NULL;
+	const char *home = NULL;
+
+	/* Setting $PERF_CONFIG makes perf read _only_ the given config file. */
+	if (config_exclusive_filename)
+		return perf_config_from_file(fn, config_exclusive_filename, data);
+	if (perf_config_system() && !access(perf_etc_perfconfig(), R_OK)) {
+		ret += perf_config_from_file(fn, perf_etc_perfconfig(),
+					    data);
+		found += 1;
+	}
+
+	home = getenv("HOME");
+	if (perf_config_global() && home) {
+		char *user_config = strdup(mkpath("%s/.perfconfig", home));
+		if (!access(user_config, R_OK)) {
+			ret += perf_config_from_file(fn, user_config, data);
+			found += 1;
+		}
+		free(user_config);
+	}
+
+	repo_config = perf_pathdup("config");
+	if (!access(repo_config, R_OK)) {
+		ret += perf_config_from_file(fn, repo_config, data);
+		found += 1;
+	}
+	free(repo_config);
+	if (found == 0)
+		return -1;
+	return ret;
+}
+
+/*
+ * Find all the stuff for perf_config_set() below.
+ */
+
+#define MAX_MATCHES 512
+
+static struct {
+	int baselen;
+	char* key;
+	int do_not_match;
+	regex_t* value_regex;
+	int multi_replace;
+	size_t offset[MAX_MATCHES];
+	enum { START, SECTION_SEEN, SECTION_END_SEEN, KEY_SEEN } state;
+	int seen;
+} store;
+
+static int matches(const char* key, const char* value)
+{
+	return !strcmp(key, store.key) &&
+		(store.value_regex == NULL ||
+		 (store.do_not_match ^
+		  !regexec(store.value_regex, value, 0, NULL, 0)));
+}
+
+static int store_aux(const char* key, const char* value, void *cb)
+{
+	const char *ep;
+	size_t section_len;
+
+	switch (store.state) {
+	case KEY_SEEN:
+		if (matches(key, value)) {
+			if (store.seen == 1 && store.multi_replace == 0) {
+				warning("%s has multiple values", key);
+			} else if (store.seen >= MAX_MATCHES) {
+				error("too many matches for %s", key);
+				return 1;
+			}
+
+			store.offset[store.seen] = ftell(config_file);
+			store.seen++;
+		}
+		break;
+	case SECTION_SEEN:
+		/*
+		 * What we are looking for is in store.key (both
+		 * section and var), and its section part is baselen
+		 * long.  We found key (again, both section and var).
+		 * We would want to know if this key is in the same
+		 * section as what we are looking for.  We already
+		 * know we are in the same section as what should
+		 * hold store.key.
+		 */
+		ep = strrchr(key, '.');
+		section_len = ep - key;
+
+		if ((section_len != store.baselen) ||
+		    memcmp(key, store.key, section_len+1)) {
+			store.state = SECTION_END_SEEN;
+			break;
+		}
+
+		/*
+		 * Do not increment matches: this is no match, but we
+		 * just made sure we are in the desired section.
+		 */
+		store.offset[store.seen] = ftell(config_file);
+		/* fallthru */
+	case SECTION_END_SEEN:
+	case START:
+		if (matches(key, value)) {
+			store.offset[store.seen] = ftell(config_file);
+			store.state = KEY_SEEN;
+			store.seen++;
+		} else {
+			if (strrchr(key, '.') - key == store.baselen &&
+			      !strncmp(key, store.key, store.baselen)) {
+					store.state = SECTION_SEEN;
+					store.offset[store.seen] = ftell(config_file);
+			}
+		}
+	}
+	return 0;
+}
+
+static int write_error(const char *filename)
+{
+	error("failed to write new configuration file %s", filename);
+
+	/* Same error code as "failed to rename". */
+	return 4;
+}
+
+static int store_write_section(int fd, const char* key)
+{
+	const char *dot;
+	int i, success;
+	struct strbuf sb = STRBUF_INIT;
+
+	dot = memchr(key, '.', store.baselen);
+	if (dot) {
+		strbuf_addf(&sb, "[%.*s \"", (int)(dot - key), key);
+		for (i = dot - key + 1; i < store.baselen; i++) {
+			if (key[i] == '"' || key[i] == '\\')
+				strbuf_addch(&sb, '\\');
+			strbuf_addch(&sb, key[i]);
+		}
+		strbuf_addstr(&sb, "\"]\n");
+	} else {
+		strbuf_addf(&sb, "[%.*s]\n", store.baselen, key);
+	}
+
+	success = write_in_full(fd, sb.buf, sb.len) == sb.len;
+	strbuf_release(&sb);
+
+	return success;
+}
+
+static int store_write_pair(int fd, const char* key, const char* value)
+{
+	int i, success;
+	int length = strlen(key + store.baselen + 1);
+	const char *quote = "";
+	struct strbuf sb = STRBUF_INIT;
+
+	/*
+	 * Check to see if the value needs to be surrounded with a dq pair.
+	 * Note that problematic characters are always backslash-quoted; this
+	 * check is about not losing leading or trailing SP and strings that
+	 * follow beginning-of-comment characters (i.e. ';' and '#') by the
+	 * configuration parser.
+	 */
+	if (value[0] == ' ')
+		quote = "\"";
+	for (i = 0; value[i]; i++)
+		if (value[i] == ';' || value[i] == '#')
+			quote = "\"";
+	if (i && value[i - 1] == ' ')
+		quote = "\"";
+
+	strbuf_addf(&sb, "\t%.*s = %s",
+		    length, key + store.baselen + 1, quote);
+
+	for (i = 0; value[i]; i++)
+		switch (value[i]) {
+		case '\n':
+			strbuf_addstr(&sb, "\\n");
+			break;
+		case '\t':
+			strbuf_addstr(&sb, "\\t");
+			break;
+		case '"':
+		case '\\':
+			strbuf_addch(&sb, '\\');
+		default:
+			strbuf_addch(&sb, value[i]);
+			break;
+		}
+	strbuf_addf(&sb, "%s\n", quote);
+
+	success = write_in_full(fd, sb.buf, sb.len) == sb.len;
+	strbuf_release(&sb);
+
+	return success;
+}
+
+static ssize_t find_beginning_of_line(const char* contents, size_t size,
+	size_t offset_, int* found_bracket)
+{
+	size_t equal_offset = size, bracket_offset = size;
+	ssize_t offset;
+
+contline:
+	for (offset = offset_-2; offset > 0
+			&& contents[offset] != '\n'; offset--)
+		switch (contents[offset]) {
+			case '=': equal_offset = offset; break;
+			case ']': bracket_offset = offset; break;
+		}
+	if (offset > 0 && contents[offset-1] == '\\') {
+		offset_ = offset;
+		goto contline;
+	}
+	if (bracket_offset < equal_offset) {
+		*found_bracket = 1;
+		offset = bracket_offset+1;
+	} else
+		offset++;
+
+	return offset;
+}
+
+int perf_config_set(const char* key, const char* value)
+{
+	return perf_config_set_multivar(key, value, NULL, 0);
+}
+
+/*
+ * If value==NULL, unset in (remove from) config,
+ * if value_regex!=NULL, disregard key/value pairs where value does not match.
+ * if multi_replace==0, nothing, or only one matching key/value is replaced,
+ *     else all matching key/values (regardless how many) are removed,
+ *     before the new pair is written.
+ *
+ * Returns 0 on success.
+ *
+ * This function does this:
+ *
+ * - it locks the config file by creating ".perf/config.lock"
+ *
+ * - it then parses the config using store_aux() as validator to find
+ *   the position on the key/value pair to replace. If it is to be unset,
+ *   it must be found exactly once.
+ *
+ * - the config file is mmap()ed and the part before the match (if any) is
+ *   written to the lock file, then the changed part and the rest.
+ *
+ * - the config file is removed and the lock file rename()d to it.
+ *
+ */
+int perf_config_set_multivar(const char* key, const char* value,
+	const char* value_regex, int multi_replace)
+{
+	int i, dot;
+	int fd = -1, in_fd;
+	int ret;
+	char* config_filename;
+	const char* last_dot = strrchr(key, '.');
+
+	if (config_exclusive_filename)
+		config_filename = strdup(config_exclusive_filename);
+	else
+		config_filename = perf_pathdup("config");
+
+	/*
+	 * Since "key" actually contains the section name and the real
+	 * key name separated by a dot, we have to know where the dot is.
+	 */
+
+	if (last_dot == NULL) {
+		error("key does not contain a section: %s", key);
+		ret = 2;
+		goto out_free;
+	}
+	store.baselen = last_dot - key;
+
+	store.multi_replace = multi_replace;
+
+	/*
+	 * Validate the key and while at it, lower case it for matching.
+	 */
+	store.key = malloc(strlen(key) + 1);
+	dot = 0;
+	for (i = 0; key[i]; i++) {
+		unsigned char c = key[i];
+		if (c == '.')
+			dot = 1;
+		/* Leave the extended basename untouched.. */
+		if (!dot || i > store.baselen) {
+			if (!iskeychar(c) || (i == store.baselen+1 && !isalpha(c))) {
+				error("invalid key: %s", key);
+				free(store.key);
+				ret = 1;
+				goto out_free;
+			}
+			c = tolower(c);
+		} else if (c == '\n') {
+			error("invalid key (newline): %s", key);
+			free(store.key);
+			ret = 1;
+			goto out_free;
+		}
+		store.key[i] = c;
+	}
+	store.key[i] = 0;
+
+	/*
+	 * If .perf/config does not exist yet, write a minimal version.
+	 */
+	in_fd = open(config_filename, O_RDONLY);
+	if ( in_fd < 0 ) {
+		free(store.key);
+
+		if ( ENOENT != errno ) {
+			error("opening %s: %s", config_filename,
+			      strerror(errno));
+			ret = 3; /* same as "invalid config file" */
+			goto out_free;
+		}
+		/* if nothing to unset, error out */
+		if (value == NULL) {
+			ret = 5;
+			goto out_free;
+		}
+
+		store.key = (char*)key;
+		if (!store_write_section(fd, key) ||
+		    !store_write_pair(fd, key, value))
+			goto write_err_out;
+	} else {
+		struct stat st;
+		char* contents;
+		size_t contents_sz, copy_begin, copy_end;
+		int i, new_line = 0;
+
+		if (value_regex == NULL)
+			store.value_regex = NULL;
+		else {
+			if (value_regex[0] == '!') {
+				store.do_not_match = 1;
+				value_regex++;
+			} else
+				store.do_not_match = 0;
+
+			store.value_regex = (regex_t*)malloc(sizeof(regex_t));
+			if (regcomp(store.value_regex, value_regex,
+					REG_EXTENDED)) {
+				error("invalid pattern: %s", value_regex);
+				free(store.value_regex);
+				ret = 6;
+				goto out_free;
+			}
+		}
+
+		store.offset[0] = 0;
+		store.state = START;
+		store.seen = 0;
+
+		/*
+		 * After this, store.offset will contain the *end* offset
+		 * of the last match, or remain at 0 if no match was found.
+		 * As a side effect, we make sure to transform only a valid
+		 * existing config file.
+		 */
+		if (perf_config_from_file(store_aux, config_filename, NULL)) {
+			error("invalid config file %s", config_filename);
+			free(store.key);
+			if (store.value_regex != NULL) {
+				regfree(store.value_regex);
+				free(store.value_regex);
+			}
+			ret = 3;
+			goto out_free;
+		}
+
+		free(store.key);
+		if (store.value_regex != NULL) {
+			regfree(store.value_regex);
+			free(store.value_regex);
+		}
+
+		/* if nothing to unset, or too many matches, error out */
+		if ((store.seen == 0 && value == NULL) ||
+				(store.seen > 1 && multi_replace == 0)) {
+			ret = 5;
+			goto out_free;
+		}
+
+		fstat(in_fd, &st);
+		contents_sz = xsize_t(st.st_size);
+		contents = mmap(NULL, contents_sz, PROT_READ,
+			MAP_PRIVATE, in_fd, 0);
+		close(in_fd);
+
+		if (store.seen == 0)
+			store.seen = 1;
+
+		for (i = 0, copy_begin = 0; i < store.seen; i++) {
+			if (store.offset[i] == 0) {
+				store.offset[i] = copy_end = contents_sz;
+			} else if (store.state != KEY_SEEN) {
+				copy_end = store.offset[i];
+			} else
+				copy_end = find_beginning_of_line(
+					contents, contents_sz,
+					store.offset[i]-2, &new_line);
+
+			if (copy_end > 0 && contents[copy_end-1] != '\n')
+				new_line = 1;
+
+			/* write the first part of the config */
+			if (copy_end > copy_begin) {
+				if (write_in_full(fd, contents + copy_begin,
+						  copy_end - copy_begin) <
+				    copy_end - copy_begin)
+					goto write_err_out;
+				if (new_line &&
+				    write_in_full(fd, "\n", 1) != 1)
+					goto write_err_out;
+			}
+			copy_begin = store.offset[i];
+		}
+
+		/* write the pair (value == NULL means unset) */
+		if (value != NULL) {
+			if (store.state == START) {
+				if (!store_write_section(fd, key))
+					goto write_err_out;
+			}
+			if (!store_write_pair(fd, key, value))
+				goto write_err_out;
+		}
+
+		/* write the rest of the config */
+		if (copy_begin < contents_sz)
+			if (write_in_full(fd, contents + copy_begin,
+					  contents_sz - copy_begin) <
+			    contents_sz - copy_begin)
+				goto write_err_out;
+
+		munmap(contents, contents_sz);
+	}
+
+	ret = 0;
+
+out_free:
+	free(config_filename);
+	return ret;
+
+write_err_out:
+	goto out_free;
+
+}
+
+static int section_name_match (const char *buf, const char *name)
+{
+	int i = 0, j = 0, dot = 0;
+	for (; buf[i] && buf[i] != ']'; i++) {
+		if (!dot && isspace(buf[i])) {
+			dot = 1;
+			if (name[j++] != '.')
+				break;
+			for (i++; isspace(buf[i]); i++)
+				; /* do nothing */
+			if (buf[i] != '"')
+				break;
+			continue;
+		}
+		if (buf[i] == '\\' && dot)
+			i++;
+		else if (buf[i] == '"' && dot) {
+			for (i++; isspace(buf[i]); i++)
+				; /* do_nothing */
+			break;
+		}
+		if (buf[i] != name[j++])
+			break;
+	}
+	return (buf[i] == ']' && name[j] == 0);
+}
+
+/* if new_name == NULL, the section is removed instead */
+int perf_config_rename_section(const char *old_name, const char *new_name)
+{
+	int ret = 0, remove = 0;
+	char *config_filename;
+	int out_fd;
+	char buf[1024];
+
+	if (config_exclusive_filename)
+		config_filename = strdup(config_exclusive_filename);
+	else
+		config_filename = perf_pathdup("config");
+	if (out_fd < 0) {
+		ret = error("could not lock config file %s", config_filename);
+		goto out;
+	}
+
+	if (!(config_file = fopen(config_filename, "rb"))) {
+		/* no config file means nothing to rename, no error */
+		goto unlock_and_out;
+	}
+
+	while (fgets(buf, sizeof(buf), config_file)) {
+		int i;
+		int length;
+		for (i = 0; buf[i] && isspace(buf[i]); i++)
+			; /* do nothing */
+		if (buf[i] == '[') {
+			/* it's a section */
+			if (section_name_match (&buf[i+1], old_name)) {
+				ret++;
+				if (new_name == NULL) {
+					remove = 1;
+					continue;
+				}
+				store.baselen = strlen(new_name);
+				if (!store_write_section(out_fd, new_name)) {
+					goto out;
+				}
+				continue;
+			}
+			remove = 0;
+		}
+		if (remove)
+			continue;
+		length = strlen(buf);
+		if (write_in_full(out_fd, buf, length) != length) {
+			goto out;
+		}
+	}
+	fclose(config_file);
+ unlock_and_out:
+ out:
+	free(config_filename);
+	return ret;
+}
+
+/*
+ * Call this to report error for your variable that should not
+ * get a boolean value (i.e. "[my] var" means "true").
+ */
+int config_error_nonbool(const char *var)
+{
+	return error("Missing value for '%s'", var);
+}