Add coreupdownd: and configurations and daemonisation1.0

Signed-off-by: Mattias Andrée <maandree@kth.se>

5 files changed, 725 insertions, 47 deletions

diff --git a/.gitignore b/.gitignore
index a7d0aa5..9978821 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,3 +16,4 @@
 /coreup
 /coredown
 /coreupdownd
+*.conf
diff --git a/Makefile b/Makefile
index 63eedf7..89ddfb5 100644
--- a/Makefile
+++ b/Makefile
@@ -4,14 +4,14 @@ CONFIGFILE = config.mk
 include $(CONFIGFILE)
 
 CPPFLAGS_CONFS =\
-	-D'COREUP_THRESHOLD_CPU=$(COREUP_THRESHOLD_CPU)'\
-	-D'COREUP_THRESHOLD_TIME=$(COREUP_THRESHOLD_TIME)'\
-	-D'COREUP_COOLDOWN=$(COREUP_COOLDOWN)'\
-	-D'COREDOWN_THRESHOLD_CPU=$(COREDOWN_THRESHOLD_CPU)'\
-	-D'COREDOWN_THRESHOLD_TIME=$(COREDOWN_THRESHOLD_TIME)'\
-	-D'COREDOWN_COOLDOWN=$(COREDOWN_COOLDOWN)'\
-	-D'DAEMON_INTERVAL_SEC=$(DAEMON_INTERVAL_SEC)'\
-	-D'DAEMON_INTERVAL_NSEC=$(DAEMON_INTERVAL_NSEC)'\
+	-D'COREUP_THRESHOLD_CPU=$(COREUP_THRESHOLD_CPU)U'\
+	-D'COREUP_THRESHOLD_TIME=$(COREUP_THRESHOLD_TIME)U'\
+	-D'COREUP_COOLDOWN=$(COREUP_COOLDOWN)U'\
+	-D'COREDOWN_THRESHOLD_CPU=$(COREDOWN_THRESHOLD_CPU)U'\
+	-D'COREDOWN_THRESHOLD_TIME=$(COREDOWN_THRESHOLD_TIME)U'\
+	-D'COREDOWN_COOLDOWN=$(COREDOWN_COOLDOWN)U'\
+	-D'DAEMON_INTERVAL_SEC=$(DAEMON_INTERVAL_SEC)U'\
+	-D'DAEMON_INTERVAL_NSEC=$(DAEMON_INTERVAL_NSEC)UL'\
 	-D'DAEMON_PATH="$(PREFIX)/bin/coreupdownd"'
 
 OBJ =\
@@ -31,6 +31,7 @@ coreupdown: $(OBJ)
 install: coreupdown
 	mkdir -p -- "$(DESTDIR)$(PREFIX)/bin"
 	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man1"
+	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man5"
 	test -f "$(DESTDIR)$(PREFIX)/bin/coreup" || test ! -e "$(DESTDIR)$(PREFIX)/bin/coreup"
 	test -f "$(DESTDIR)$(PREFIX)/bin/coredown" || test ! -e "$(DESTDIR)$(PREFIX)/bin/coredown"
 	test -f "$(DESTDIR)$(PREFIX)/bin/coreupdownd" || test ! -e "$(DESTDIR)$(PREFIX)/bin/coreupdownd"
@@ -38,6 +39,7 @@ install: coreupdown
 	ln -sf -- coreup "$(DESTDIR)$(PREFIX)/bin/coredown"
 	ln -sf -- coreup "$(DESTDIR)$(PREFIX)/bin/coreupdownd"
 	cp -- coreup.1 coredown.1 coreupdownd.1 "$(DESTDIR)$(MANPREFIX)/man1"
+	cp -- coreupdownd.conf.5 "$(DESTDIR)$(MANPREFIX)/man5"
 
 postinstall:
 	chown '0:0' "$(DESTDIR)$(PREFIX)/bin/coreup"
@@ -50,6 +52,7 @@ uninstall:
 	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man1/coreup.1"
 	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man1/coredown.1"
 	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man1/coreupdownd.1"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man5/coreupdownd.conf.5"
 
 clean:
 	-rm -f -- *.o *.a *.lo *.su *.so *.so.* *.gch *.gcov *.gcno *.gcda
diff --git a/coreupdown.c b/coreupdown.c
index ab3d4e9..500839f 100644
--- a/coreupdown.c
+++ b/coreupdown.c
@@ -1,4 +1,7 @@
 /* See LICENSE file for copyright and license details. */
+#include <linux/close_range.h>
+#include <sys/file.h>
+#include <sys/stat.h>
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -11,7 +14,9 @@
 #include <time.h>
 #include <unistd.h>
 
-static const char *argv0;
+#include <libsimple-arg.h>
+
+char *argv0;
 static volatile sig_atomic_t caught_sighup = 0;
 
 #define coreup() coreupdown(ULONG_MAX)
@@ -22,7 +27,7 @@ coreupdown(unsigned long int count)
 {
 	char path[sizeof("/sys/devices/system/cpu/cpu/online") + 3 * sizeof(count)];
 	unsigned long int i;
-	int fd, ret = 0;
+	int fd, have_success = 0, have_failure = 0;
 
 	for (i = 1; i; i++) {
 		sprintf(path, "/sys/devices/system/cpu/cpu%zu/online", i);
@@ -33,13 +38,39 @@ coreupdown(unsigned long int count)
 			fprintf(stderr, "%s: open %s O_WRONLY\n", argv0, path);
 			return -1;
 		}
+	write_again:
 		if (write(fd, i < count ? "1\n" : "0\n", 2) < 0) {
+			if (errno == EINTR)
+				goto write_again;
 			fprintf(stderr, "%s: write %s\n", argv0, path);
-			ret = -1;
+			have_failure = 1;
+		} else {
+			have_success = 1;
 		}
 		close(fd);
 	}
-	return ret;
+	return -(have_failure && !have_success);
+}
+
+static void
+oneshot_usage(const char *command)
+{
+	fprintf(stderr, "usage: %s [count]\n", command);
+}
+
+static void
+daemon_usage(const char *command)
+{
+	fprintf(stderr, "usage: %s "
+	                "[-C coreup-cooldown-time] "
+	                "[-c coredown-cooldown-time] "
+	                "[-i check-interval] "
+	                "[-s configuration-file] "
+	                "[-T coreup-cpu-usage-time-consistency-threshold] "
+	                "[-t coredown-cpu-usage-time-consistency-threshold] "
+	                "[-U coreup-cpu-usage-threshold] "
+	                "[-u coredown-cpu-usage-threshold] "
+	                "[-ef]\n", command);
 }
 
 static int
@@ -52,7 +83,7 @@ oneshot_main(int argc, char **argv, unsigned long int count)
 
 	if (argc > 1) {
 	usage:
-		fprintf(stderr, "usage: %s [count]\n", argv0);
+		oneshot_usage(argv0);
 		return 1;
 	}
 
@@ -236,17 +267,428 @@ sighup_handler(int signo)
 }
 
 static int
+init_daemon(char **cwd_out)
+{
+	int sig;
+	sigset_t sigmask;
+	char *cwd = NULL;
+	size_t cwd_size = 0;
+
+	for (;;) {
+		cwd = realloc(cwd, cwd_size += 512);
+		if (cwd) {
+			if (getcwd(cwd, cwd_size))
+				break;
+			if (errno == ERANGE)
+				continue;
+		}
+		fprintf(stderr, "%s: getcwd: %s\n", argv0, strerror(errno));
+		return -1;
+	}
+	*cwd_out = cwd;
+
+	umask(0);
+	if (chdir("/"))
+		fprintf(stderr, "%s: chdir /: %s\n", argv0, strerror(errno));
+	if (sigemptyset(&sigmask))
+		fprintf(stderr, "%s: sigemptyset: %s\n", argv0, strerror(errno));
+	else if (sigprocmask(SIG_SETMASK, &sigmask, NULL))
+		fprintf(stderr, "%s: sigprocmask SIG_SETMASK {}: %s\n", argv0, strerror(errno));
+	for (sig = 1; sig < _NSIG; sig++)
+		if (signal(sig, SIG_DFL) == SIG_ERR && errno != EINVAL)
+			fprintf(stderr, "%s: signal %i SIG_DFL: %s\n", argv0, sig, strerror(errno));
+	if (close_range(3, UINT_MAX, 0))
+		fprintf(stderr, "%s: close_range 3 <max> 0: %s\n", argv0, strerror(errno));
+
+	return 0;
+}
+
+static void
+writefile(const char *path, const char *data, size_t len)
+{
+	int fd;
+	size_t off;
+	ssize_t r;
+
+	fd = open(path, O_CREAT | O_WRONLY, 0644);
+	if (fd < 0) {
+		fprintf(stderr, "%s: open %s O_CREAT|O_WRONLY, 0644: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+
+	while (flock(fd, LOCK_EX)) {
+		if (errno != EINTR) {
+			fprintf(stderr, "%s: flock %s LOCK_EX: %s\n", argv0, path, strerror(errno));
+			exit(1);
+		}
+	}
+
+	if (ftruncate(fd, 0)) {
+		fprintf(stderr, "%s: ftruncate %s 0: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+
+	for (off = 0; off < len; off++) {
+		r = write(fd, &data[off], len - off);
+		if (r < 0) {
+			if (errno == EINTR)
+				continue;
+		write_error:
+			fprintf(stderr, "%s: write %s: %s\n", argv0, path, strerror(errno));
+			exit(1);
+		}
+		off += (size_t)r;
+	}
+
+	if (close(fd))
+		goto write_error;
+}
+
+static void
+daemonise(int keep_stderr)
+{
+	pid_t pid;
+	char buf[3 * sizeof(uintmax_t) + 2];
+	int len, pipe_rw[2], fd;
+	ssize_t r;
+
+	if (pipe(pipe_rw)) {
+		fprintf(stderr, "%s: pipe: %s\n", argv0, strerror(errno));
+		exit(1);
+	}
+
+	pid = fork();
+	switch (pid) {
+	case -1:
+	fork_failure:
+		fprintf(stderr, "%s: fork: %s\n", argv0, strerror(errno));
+		_exit(1);
+
+	case 0:
+		close(pipe_rw[0]);
+		if (pipe_rw[0] <= STDERR_FILENO) {
+			fd = fcntl(pipe_rw[0], F_DUPFD, STDERR_FILENO + 1);
+			if (fd <= STDERR_FILENO) {
+				fprintf(stderr, "%s: fcntl DUPFD: %s\n", argv0, strerror(errno));
+				exit(1);
+			}
+			close(pipe_rw[0]);
+			pipe_rw[0] = fd;
+		}
+
+		if (setsid() == -1) {
+			fprintf(stderr, "%s: setsid: %s\n", argv0, strerror(errno));
+			exit(1);
+		}
+
+		pid = fork();
+		switch (pid) {
+		case -1:
+			goto fork_failure;
+		case 0:
+			pid = getpid();
+			len = snprintf(buf, sizeof(buf), "%ju\n", (uintmax_t)pid);
+			if (len < 2)
+				abort();
+			writefile("/run/coreupdown.pid", buf, (size_t)len);
+
+			if (write(pipe_rw[1], &(char){0}, 1) <= 0 || close(pipe_rw[1])) {
+				fprintf(stderr, "%s: write <pipe>: %s\n", argv0, strerror(errno));
+				exit(1);
+			}
+
+			if (!keep_stderr) {
+				close(STDERR_FILENO);
+				fd = open("/dev/null", O_WRONLY);
+				if (fd >= 0 && fd != STDERR_FILENO) {
+					dup2(fd, STDERR_FILENO);
+					close(fd);
+				}
+			}
+			break;
+		default:
+			_exit(1);
+		}
+		break;
+
+	default:
+		close(pipe_rw[1]);
+		r = read(pipe_rw[0], buf, 1);
+		if (!r)
+			_exit(1);
+		if (r < 0) {
+			fprintf(stderr, "%s: read <pipe>: %s\n", argv0, strerror(errno));
+			_exit(1);
+		}
+		_exit(0);
+	}
+}
+
+static int
+parse_nanotime(const char *s, unsigned int *sec, unsigned long int *nsec)
+{
+	unsigned long int tmp;
+	int digits;
+	char *end;
+
+	if (!isdigit(*s))
+		goto invalid;
+	tmp = strtoul(s, &end, 10);
+	s = end;
+	if (errno)
+		goto invalid;
+#if UINT_MAX < ULONG_MAX
+	if (tmp > UINT_MAX)
+		goto invalid;
+#endif
+
+	*sec = (unsigned int)tmp;
+	*nsec = 0;
+
+	if (!*s)
+		goto done;
+	if (*s != '.')
+		goto invalid;
+	s++;
+
+	for (digits = 0; digits < 9 && *s; digits++, s++) {
+		if (!isdigit(*s))
+			goto invalid;
+		*nsec *= 10;
+		*nsec += (*s & 15);
+	}
+	for (; digits < 9; digits++)
+		*nsec *= 10;
+	if (!*s)
+		goto done;
+	if (!isdigit(*s))
+		goto invalid;
+
+	if (*s >= '5') {
+		if (*nsec < 999999999UL) {
+			*nsec += 1;
+		} else if (*sec < UINT_MAX) {
+			*sec += 1;
+			*nsec = 0;
+		}
+	}
+	for (; *s; s++)
+		if (!isdigit(*s))
+			goto invalid;
+
+done:
+	return 0;
+invalid:
+	return -1;
+}
+
+#if defined(__GNUC__)
+__attribute__((pure))
+#endif
+static char *
+rstrip(char *s)
+{
+	char *ret = s;
+	while (*s) {
+		while (*s && !isspace(*s) && *s != '#')
+			s++;
+		ret = s;
+		while (isspace(*s))
+			s++;
+		if (*s == '#')
+			break;
+	}
+	return ret;
+}
+
+static void
+load_configurations(const char *file, int optional,
+                    unsigned int *coreup_threshold_cpu, unsigned int *coredown_threshold_cpu,
+                    unsigned int *coreup_threshold_time, unsigned int *coredown_threshold_time,
+                    unsigned int *coreup_cooldown, unsigned int *coredown_cooldown,
+                    unsigned int *daemon_interval_sec, unsigned long int *daemon_interval_nsec)
+{
+	unsigned int *uintp;
+	unsigned long int tmp;
+	int fd;
+	FILE *f;
+	ssize_t len;
+	char *line = NULL, *s, *p, pc;
+	size_t size = 0, n;
+
+	fd = open(file, O_RDONLY);
+	if (fd < 0) {
+		if (optional && errno == ENOENT)
+			return;
+		fprintf(stderr, "%s: open %s O_RDONLY: %s\n", argv0, file, strerror(errno));
+		exit(1);
+	}
+
+	f = fdopen(fd, "r");
+	if (!f) {
+		fprintf(stderr, "%s: fdopen %s r: %s\n", argv0, file, strerror(errno));
+		exit(1);
+	}
+
+#define OPTION(OPT) (!strncmp(s, OPT, n = sizeof(OPT) - 1) && (isspace(s[n]) || s[n] == '='))
+
+	while ((len = getline(&line, &size, f)) != -1) {
+		if (len && line[len - 1] == '\n')
+			line[--len] = 0;
+		s = line;
+		while (isspace(*s))
+			s++;
+		if (!*s || *s == '#')
+			continue;
+
+		if (OPTION("coreup-cpu-usage-threshold"))
+			uintp = coreup_threshold_cpu;
+		else if (OPTION("coredown-cpu-usage-threshold"))
+			uintp = coredown_threshold_cpu;
+		else if (OPTION("coreup-cpu-usage-time-consistency-threshold"))
+			uintp = coreup_threshold_time;
+		else if (OPTION("coredown-cpu-usage-time-consistency-threshold"))
+			uintp = coredown_threshold_time;
+		else if (OPTION("coreup-cooldown-time"))
+			uintp = coreup_cooldown;
+		else if (OPTION("coredown-cooldown-time"))
+			uintp = coredown_cooldown;
+		else
+			goto not_uint;
+
+		s = &s[n];
+		while (isspace(*s))
+			s++;
+		if (*s != '=')
+			goto invalid;
+		s++;
+		while (isspace(*s))
+			s++;
+		p = rstrip(s);
+		pc = *p;
+		*p = 0;
+
+		if (!isdigit(*s))
+			goto invalid_restore;
+		errno = 0;
+		tmp = strtoul(s, &s, 10);
+		if (*s || errno)
+			goto invalid_restore;
+#if UINT_MAX < ULONG_MAX
+		if (tmp > UINT_MAX)
+			goto invalid_restore;
+#endif
+		if (uintp)
+			*uintp = (unsigned int)tmp;
+
+		continue;
+	not_uint:
+
+		if (!OPTION("check-interval"))
+			goto invalid;
+
+		s = &s[n];
+		while (isspace(*s))
+			s++;
+		if (*s != '=')
+			goto invalid;
+		s++;
+		while (isspace(*s))
+			s++;
+		p = rstrip(s);
+		pc = *p;
+		*p = 0;
+
+		if (daemon_interval_sec && daemon_interval_nsec) {
+			if (parse_nanotime(s, daemon_interval_sec, daemon_interval_nsec)) {
+			invalid_restore:
+				*p = pc;
+				goto invalid;
+			}
+		}
+
+		continue;
+
+	invalid:
+		fprintf(stderr, "%s: invalid line in %s: %s\n", argv0, file, line);
+	}
+
+#undef OPTION
+
+	if (fclose(f)) {
+		fprintf(stderr, "%s: fclose %s: %s\n", argv0, file, strerror(errno));
+		exit(1);
+	}
+
+	free(line);
+}
+
+static char *
+pathjoin(const char *a, const char *b)
+{
+	const char *p;
+	char *r;
+	size_t n;
+	int need_slash;
+	p = strrchr(a, '/');
+	if (!p)
+		abort();
+	need_slash = p[1] ? 1 : 0;
+	n = strlen(a) + (size_t)need_slash + strlen(b) + 1;
+	r = malloc(n);
+	if (!r) {
+		fprintf(stderr, "%s: %s\n", argv0, strerror(errno));
+		return NULL;
+	}
+	stpcpy(stpcpy(stpcpy(r, a), need_slash ? "/" : ""), b);
+	return r;
+}
+
+static char *
+memjoin(const char *a, size_t an, const char *b, size_t bn)
+{
+	size_t n = an + bn;
+	char *r = malloc(n);
+	if (!r) {
+		fprintf(stderr, "%s: %s\n", argv0, strerror(errno));
+		return NULL;
+	}
+	memcpy(r, a, an);
+	memcpy(&r[an], b, bn);
+	return r;
+}
+
+static int
 daemon_main(int argc, char **argv, int orig_argc, char **orig_argv, int reexeced)
 {
 	uintmax_t total, idle;
-	size_t cpus;
-	int up_time = 0, down_time = 0, cooldown = 0, err;
+	size_t cpus, offset;
+	unsigned int up_time = 0, down_time = 0, cooldown = 0;
+	int err, foreground = 0, keep_stderr = 0, argnum, different;
 	struct timespec interval, rem;
-	uintmax_t coreup_threshold_cpu, coredown_threshold_cpu;
-	int coreup_threshold_time, coredown_threshold_time;
-	int coreup_cooldown, coredown_cooldown;
-	time_t daemon_interval_sec;
-	long int daemon_interval_nsec;
+	uintmax_t coreup_threshold_cpu_ju, coredown_threshold_cpu_ju;
+	unsigned int coreup_threshold_cpu, coredown_threshold_cpu;
+	unsigned int coreup_threshold_time, coredown_threshold_time;
+	unsigned int coreup_cooldown, coredown_cooldown;
+	unsigned int daemon_interval_sec, *uintp;
+	unsigned long int daemon_interval_nsec, tmp;
+	int have_coreup_threshold_cpu = 0, have_coredown_threshold_cpu = 0;
+	int have_coreup_threshold_time = 0, have_coredown_threshold_time = 0;
+	int have_coreup_cooldown = 0, have_coredown_cooldown = 0;
+	int have_daemon_interval = 0;
+	char *arg, *cwd = NULL, *conffile = NULL;
+	char **proper_orig_argv;
+
+	if (!reexeced && init_daemon(&cwd))
+		return -1;
+
+	proper_orig_argv = calloc((size_t)(orig_argc + 1), sizeof(*orig_argv));
+	if (!proper_orig_argv) {
+		fprintf(stderr, "%s: %s\n", argv0, strerror(errno));
+		return 1;
+	}
+	memcpy(proper_orig_argv, orig_argv, (size_t)(orig_argc + 1) * sizeof(*orig_argv));
+	orig_argv = proper_orig_argv;
 
 restart:
 	coreup_threshold_cpu = COREUP_THRESHOLD_CPU;
@@ -259,40 +701,137 @@ restart:
 	daemon_interval_nsec = DAEMON_INTERVAL_NSEC;
 
 	if (reexeced)
-		argv[0] = "coreupdownd";
-
-	if (argc && !strcmp(argv[0], "--")) {
-		argv++;
-		argc--;
-	}
+		argv[0] = *(char **)(void *)&"coreupdownd";
+
+#define usage() goto usage
+	SUBARGBEGIN {
+	case 'U': uintp = &coreup_threshold_cpu;    have_coreup_threshold_cpu = 1;    goto uint;
+	case 'u': uintp = &coredown_threshold_cpu;  have_coredown_threshold_cpu = 1;  goto uint;
+	case 'T': uintp = &coreup_threshold_time;   have_coreup_threshold_time = 1;   goto uint;
+	case 't': uintp = &coredown_threshold_time; have_coredown_threshold_time = 1; goto uint;
+	case 'C': uintp = &coreup_cooldown;         have_coreup_cooldown = 1;         goto uint;
+	case 'c': uintp = &coredown_cooldown;       have_coredown_cooldown = 1;       goto uint;
+
+	case 'i':
+		arg = ARGNULL();
+		if (!arg)
+			goto usage;
+		if (parse_nanotime(arg, &daemon_interval_sec, &daemon_interval_nsec))
+			goto invalid;
+		have_daemon_interval = 1;
+		break;
+
+	case 'e':
+		keep_stderr = 1;
+		break;
+
+	case 'f':
+		foreground = 1;
+		break;
+
+	case 's':
+		conffile = ARGNULL();
+		if (!conffile || !*conffile)
+			goto usage;
+		if (*conffile == '/')
+			break;
+		offset = (size_t)(conffile - LFLAG());
+		different = (conffile < LFLAG() || offset > strlen(LFLAG()));
+		for (argnum = 0; argnum < orig_argc; argnum++)
+			if (LFLAG() == orig_argv[argnum])
+				break;
+		if (argnum == orig_argc)
+			abort();
+		conffile = pathjoin(cwd, conffile);
+		if (different)
+			orig_argv[argnum + 1] = conffile;
+		else
+			orig_argv[argnum] = memjoin(LFLAG(), offset, conffile, strlen(conffile) + 1);
+		break;
+
+	default:
+		goto usage;
+
+	uint:
+		arg = ARGNULL();
+		if (!arg)
+			goto usage;
+		errno = 0;
+		if (!isdigit(*arg))
+			goto invalid;
+		tmp = strtoul(arg, &arg, 10);
+		if (*arg || errno) {
+		invalid:
+			fprintf(stderr, "%s: invalid argument for option -%c\n", argv0, FLAG());
+			return 1;
+		}
+#if UINT_MAX < ULONG_MAX
+		if (tmp > UINT_MAX)
+			goto invalid;
+#endif
+		*uintp = (unsigned int)tmp;
+		break;
+	} ARGEND;
+#undef usage
 
 	if (argc > 0) {
-		fprintf(stderr, "usage: %s\n", argv0);
+	usage:
+		daemon_usage(argv0);
 		return 1;
 	}
 
-	if (!reexeced) {
-		/* TODO add proper daemonisation */
+	load_configurations(conffile ? conffile : "/etc/coreupdownd.conf", !conffile,
+	                    have_coreup_threshold_cpu ? NULL : &coreup_threshold_cpu,
+	                    have_coredown_threshold_cpu ? NULL : &coredown_threshold_cpu,
+	                    have_coreup_threshold_time ? NULL : &coreup_threshold_time,
+	                    have_coredown_threshold_time ? NULL : &coredown_threshold_time,
+	                    have_coreup_cooldown ? NULL : &coreup_cooldown,
+	                    have_coredown_cooldown ? NULL : &coredown_cooldown,
+	                    have_daemon_interval ? NULL : &daemon_interval_sec,
+	                    have_daemon_interval ? NULL : &daemon_interval_nsec);
+
+	if (coreup_threshold_cpu > 100) {
+		fprintf(stderr, "%s: CPU usage threshold for coreup was above 100, setting to 100\n", argv0);
+		coreup_threshold_cpu = 100;
+	} else if (coreup_threshold_cpu == 0) {
+		fprintf(stderr, "%s: CPU usage threshold for coreup was 0, setting to 1\n", argv0);
+		coreup_threshold_cpu = 1;
+	}
+	if (coredown_threshold_cpu > 99) {
+		fprintf(stderr, "%s: CPU usage threshold for coreup was above 99, setting to 99\n", argv0);
+		coredown_threshold_cpu = 99;
+	}
+	if (!daemon_interval_sec && !daemon_interval_nsec)
+		daemon_interval_nsec = 1;
+
+	interval.tv_sec = (time_t)daemon_interval_sec;
+	interval.tv_nsec = (long int)daemon_interval_nsec;
+	coreup_threshold_cpu_ju = (uintmax_t)coreup_threshold_cpu;
+	coredown_threshold_cpu_ju = (uintmax_t)coredown_threshold_cpu;
+	if (coreup_threshold_cpu_ju <= coredown_threshold_cpu_ju) {
+		fprintf(stderr, "%s: coreup cpu usage threshold must be above "
+		        "coredown cpu usage threshold\n", argv0);
+		return 1;
 	}
 
-	/* TODO configurations should be configurable */
+	if (!reexeced && !foreground)
+		daemonise(keep_stderr);
 
 	if (signal(SIGHUP, sighup_handler) == SIG_ERR)
 		fprintf(stderr, "%s: signal SIGHUP <function>: %s\n", argv0, strerror(errno));
 
-	interval.tv_sec = daemon_interval_sec;
-	interval.tv_nsec = daemon_interval_nsec;
-
 	if (getusage(&total, &idle, &cpus))
 		return 1;
 
-	close(STDIN_FILENO);
-	close(STDOUT_FILENO);
+	if (!reexeced) {
+		close(STDIN_FILENO);
+		close(STDOUT_FILENO);
+	}
 
 	for (;;) {
 		if (caught_sighup) {
 			caught_sighup = 0;
-			orig_argv[0] = "coreupdownd ";
+			orig_argv[0] = *(char **)(void *)&"coreupdownd ";
 			execv(DAEMON_PATH, orig_argv);
 			fprintf(stderr, "%s: execv %s: %s\n", argv0, DAEMON_PATH, strerror(errno));
 			reexeced = 1;
@@ -317,18 +856,20 @@ restart:
 			continue;
 		}
 
-		if (cpus == 1 && 100 * (total - idle) > coreup_threshold_cpu * total) {
+		if (cpus == 1 && 100 * (total - idle) >= coreup_threshold_cpu_ju * total) {
 			down_time = 0;
 			if (up_time++ >= coreup_threshold_time) {
 				cooldown = coreup_cooldown;
-				coreup();
+				if (coreup())
+					return 1;
 				up_time = 0;
 			}
-		} else if (cpus > 1 && 100 * (total - idle) < coredown_threshold_cpu * total * cpus) {
+		} else if (cpus > 1 && 100 * (total - idle) <= coredown_threshold_cpu_ju * total * cpus) {
 			up_time = 0;
 			if (down_time++ >= coredown_threshold_time) {
 				cooldown = coredown_cooldown;
-				coredown();
+				if (coredown())
+					return 1;
 				down_time = 0;
 			}
 		} else {
@@ -358,9 +899,8 @@ main(int argc, char **argv)
 			return daemon_main(argc, argv, argc + 1, &argv[-1], 1);
 	}
 
-	fprintf(stderr, "usage: coreup [count]\n"
-	                "usage: coredown [count]\n"
-	                "usage: coreupdownd\n");
-
+	oneshot_usage("coreup");
+	oneshot_usage("coredown");
+	daemon_usage("coreupdownd");
 	return 1;
 }
diff --git a/coreupdownd.1 b/coreupdownd.1
index 9dde00b..23d7487 100644
--- a/coreupdownd.1
+++ b/coreupdownd.1
@@ -1,8 +1,17 @@
 .TH COREUPDOWND 1 COREUPDOWN
 .SH MAME
-coreupdownd - Dynamically enable and disable CPU' to only use one during low CPU usage
+coreupdownd - Dynamically enable and disable CPU's to only use one during low CPU usage
 .SH SYNPOSIS
 coreupdownd
+.RI "[-C " coreup-cooldown-time ]
+.RI "[-c " coredown-cooldown-time ]
+.RI "[-i " check-interval ]
+.RI "[-s " configuration-file ]
+.RI "[-T " coreup-cpu-usage-time-consistency-threshold ]
+.RI "[-t " coredown-cpu-usage-time-consistency-threshold ]
+.RI "[-U " coreup-cpu-usage-threshold ]
+.RI "[-u " coredown-cpu-usage-threshold ]
+[-ef]
 .SH DESCRIPTION
 The
 .B coreupdownd
@@ -19,7 +28,67 @@ that have input performance issues (keyboard input lag
 and keys getting stuck) when more than one CPU core is
 online.
 .SH OPTIONS
-No options are supported.
+The
+.B coreupdownd
+daemon shall conform to the Base Definitions volume of
+POSIX.1-2017, Section 12.2, Utility  Syntax Guidelines.
+.PP
+The following options are supported:
+.TP
+.BI "-C " coreup-cooldown-time
+The amount of time, measured in (integer) multiples of the
+.IR check-interval ,
+before the daemon may disable CPU's after enabling CPU's.
+During this time, time is not counted toward
+.IR coredown-cpu-usage-threshold .
+.TP
+.BI "-c " coredown-cooldown-time
+The amount of time, measured in (integer) multiples of the
+.IR check-interval ,
+before the daemon may enable CPU's after disabling CPU's.
+During this time, time is not counted toward
+.IR coreup-cpu-usage-threshold .
+.TP
+.B -e
+Do not close standard error at end of initialisation.
+.TP
+.B -f
+Do not daemonise. (The standard input and standard
+output will still be closed when the process has
+completed it's initialisation.)
+
+Implies
+.BR -e .
+.TP
+.BI "-i " check-interval
+The interval, in seconds (need not be integer), with
+which the daemon periodically checks the CPU usage.
+.TP
+.BI "-s " configuration-file
+Configuration file to read instead of
+.BR /etc/coreupdownd.conf .
+.TP
+.BI "-T " coreup-cpu-usage-time-consistency-threshold
+The amount of time, measure in (integer) multiples of the
+.I check-interval
+the CPU usage must have stayed at or above
+.I coreup-cpu-usage-threshold
+before the daemon may enable all CPU's.
+.TP
+.BI "-t " coredown-cpu-usage-time-consistency-threshold
+The amount of time, measured in (integer) multiples of the
+.IR check-interval ,
+the CPU usage must have stayed at or below
+.I coredown-cpu-usage-threshold
+before the daemon may disable all CPU's except the main core .
+.TP
+.BI "-U " coreup-cpu-usage-threshold
+The required CPU usage (integer lower bound) before the
+daemon may enable all CPU's.
+.TP
+.BI "-u " coredown-cpu-usage-threshold
+The required CPU usage (integer upper bound) before the
+daemon may disable all CPU's except the main core.
 .SH OPERANDS
 No operands are supported.
 .SH STDIN
@@ -34,7 +103,14 @@ None.
 No environment variables affects the execution of
 .BR coreupdownd .
 .SH ASYNCHRONOUS EVENTS
-Default.
+If the
+.B coreupdownd
+utility traps the following signals:
+.TP
+.B SIGHUP
+Causes the daemon reload it's configurations, and
+attempt to update to the newest installed version
+of the daemon.
 .SH STDOUT
 The
 .B coreupdownd
@@ -70,5 +146,6 @@ None.
 .SH FUTURE DIRECTIONS
 None.
 .SH SEE ALSO
+.BR coreupdownd.conf (5),
 .BR coreup (1),
 .BR coredown (1)
diff --git a/coreupdownd.conf.5 b/coreupdownd.conf.5
new file mode 100644
index 0000000..3e8759c
--- /dev/null
+++ b/coreupdownd.conf.5
@@ -0,0 +1,57 @@
+.TH COREUPDOWND 5 COREUPDOWN
+.SH MAME
+coreupdownd.conf - Configurations for coreupdownd(1)
+.SH SYNPOSIS
+/etc/coreupdownd.conf
+.SH DESCRIPTION
+The
+.B coreupdownd.conf
+configuration files is a plain line based
+configuration file for the
+.BR coreupdownd (1)
+daemon.
+.PP
+Any hash
+.RB ( # )
+character starts comment that end of the
+end of the cline.
+Comments and otherwise blank lines are ignored.
+Apart from this, each line must be a configuration
+name, followed by an equals sign
+.RB ( = ),
+followed by the value for the configuration.
+Spaces may be added around the equals sign and
+around the line.
+.PP
+The following configurations are recognised,
+refer to the OPTIONS section in
+.BR coreupdownd (1)
+for interpretation of them:
+.PP
+.TP
+*
+coreup-cpu-usage-threshold
+.TP
+*
+coredown-cpu-usage-threshold
+.TP
+*
+coreup-cpu-usage-time-consistency-threshold
+.TP
+*
+coredown-cpu-usage-time-consistency-threshold
+.TP
+*
+coreup-cooldown-time
+.TP
+*
+coredown-cooldown-time
+.TP
+*
+check-interval
+.SH NOTES
+None.
+.SH SEE ALSO
+.BR coreupdownd (1),
+.BR coreup (1),
+.BR coredown (1)