Add iexec

4 files changed, 182 insertions, 5 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b93fbd7..4ce01ee 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,6 +51,9 @@ target_link_libraries (fancontrol-ng ${project_libraries})
 add_executable (priod priod.c)
 target_link_libraries (priod ${project_libraries})
 
+add_executable (iexec iexec.c)
+target_link_libraries (iexec ${project_libraries})
+
 if (WITH_GDM)
 	include_directories (${gdm_INCLUDE_DIRS})
 	add_executable (gdm-switch-user gdm-switch-user.c)
@@ -90,8 +93,8 @@ if (WITH_GDM)
 	install (TARGETS gdm-switch-user DESTINATION ${CMAKE_INSTALL_BINDIR})
 endif (WITH_GDM)
 
-install (TARGETS wmstatus brightness input-switch fancontrol-ng priod siprandom
-	DESTINATION ${CMAKE_INSTALL_BINDIR})
+install (TARGETS wmstatus brightness input-switch fancontrol-ng priod iexec
+	siprandom DESTINATION ${CMAKE_INSTALL_BINDIR})
 install (PROGRAMS shellify DESTINATION ${CMAKE_INSTALL_BINDIR})
 install (FILES LICENSE DESTINATION ${CMAKE_INSTALL_DOCDIR})
 
diff --git a/README.adoc b/README.adoc
index 63c919b..595d5f9 100644
--- a/README.adoc
+++ b/README.adoc
@@ -13,10 +13,12 @@ to other people as well:
  - 'fancontrol-ng' is a clone of fancontrol that can handle errors on resume
    from suspend instead of setting fans to maximum speed and quitting;
    in general it doesn't handle everything the original does
- - 'priod' sets CPU, I/O and OOM killer priorities for new processes according
-   to configuration
+ - 'priod' sets process CPU, I/O and OOM killer priorities automatically
+   according to configuration
  - 'shellify' is a simple script that sets up a shell for commands like vgdb
    and nmcli that are painfully lacking it
+ - 'iexec' runs a program and attempts to restart it cleanly when the
+   executable file is replaced on the disk
  - 'gdm-switch-user' tells the running GDM daemon, if any, to show the switch
    user screen
  - 'siprandom' uses the SipHash 2-4 algorithm to produce a stream of
diff --git a/iexec.c b/iexec.c
new file mode 100644
index 0000000..a05e1df
--- /dev/null
+++ b/iexec.c
@@ -0,0 +1,172 @@
+/*
+ * iexec.c: run a program and restart on file change
+ *
+ * Copyright (c) 2017, Přemysl Janouch <p.janouch@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "config.h"
+#undef PROGRAM_NAME
+#define PROGRAM_NAME "iexec"
+#include "liberty/liberty.c"
+
+// This can also work on BSD if someone puts in the effort to support kqueue
+#include <sys/inotify.h>
+
+static pid_t g_child;
+static bool g_restarting = false;
+static int g_inotify_fd, g_inotify_wd;
+
+static void
+handle_file_change (const char *base)
+{
+	char buf[4096]; ssize_t len; const struct inotify_event *e;
+	while ((len = read (g_inotify_fd, buf, sizeof buf)) > 0)
+	for (char *ptr = buf; ptr < buf + len; ptr += sizeof *e + e->len)
+	{
+		e = (const struct inotify_event *) buf;
+		if (e->wd != g_inotify_wd || strcmp (e->name, base))
+			continue;
+
+		print_debug ("file changed, killing child");
+		g_restarting = true;
+		if (kill (g_child, SIGINT))
+			print_error ("kill: %s", strerror (errno));
+	}
+}
+
+static void
+spawn (char *argv[])
+{
+	if ((g_child = fork ()) == -1)
+		exit_fatal ("fork: %s", strerror (errno));
+	else if (!g_child)
+	{
+		execvp (argv[0], argv);
+		exit_fatal ("execvp: %s", strerror (errno));
+	}
+}
+
+static bool
+check_child_death (char *argv[])
+{
+	if (waitpid (g_child, NULL, WNOHANG) != g_child)
+		return true;
+
+	if (!g_restarting)
+	{
+		print_debug ("child died on its own, not respawning");
+		return false;
+	}
+	else
+	{
+		print_debug ("child died on request, respawning");
+		spawn (argv);
+		g_restarting = false;
+		return true;
+	}
+}
+
+static void
+sigchld_handler (int signum)
+{
+	// We need to have this handler so that pselect() can return EINTR
+	(void) signum;
+}
+
+int
+main (int argc, char *argv[])
+{
+	static const struct opt opts[] =
+	{
+		{ 'd', "debug", NULL, 0, "run in debug mode" },
+		{ 'h', "help", NULL, 0, "display this help and exit" },
+		{ 'V', "version", NULL, 0, "output version information and exit" },
+		{ 0, NULL, NULL, 0, NULL }
+	};
+
+	struct opt_handler oh = opt_handler_make (argc, argv, opts,
+		"PROGRAM [ARG...]", "Run a program and restart on file change.");
+
+	// We have to turn that off as it causes more trouble than what it's worth
+	char *nonpermuting = xstrdup_printf ("+%s", oh.opt_string);
+	free (oh.opt_string);
+	oh.opt_string = nonpermuting;
+
+	int c;
+	while ((c = opt_handler_get (&oh)) != -1)
+	switch (c)
+	{
+	case 'd':
+		g_debug_mode = true;
+		break;
+	case 'h':
+		opt_handler_usage (&oh, stdout);
+		exit (EXIT_SUCCESS);
+	case 'V':
+		printf (PROGRAM_NAME " " PROGRAM_VERSION "\n");
+		exit (EXIT_SUCCESS);
+	default:
+		print_error ("wrong options");
+		opt_handler_usage (&oh, stderr);
+		exit (EXIT_FAILURE);
+	}
+
+	if (argc == optind)
+	{
+		opt_handler_usage (&oh, stderr);
+		exit (EXIT_FAILURE);
+	}
+
+	opt_handler_free (&oh);
+	argc -= optind;
+	argv += optind;
+
+	(void) signal (SIGPIPE, SIG_IGN);
+	struct sigaction sa = { .sa_handler = sigchld_handler };
+	sigemptyset (&sa.sa_mask);
+	if (sigaction (SIGCHLD, &sa, NULL))
+		exit_fatal ("sigaction: %s", strerror (errno));
+
+	sigset_t chld, orig;
+	sigemptyset (&chld);
+	sigaddset (&chld, SIGCHLD);
+	if (sigprocmask (SIG_BLOCK, &chld, &orig))
+		exit_fatal ("sigprocmask: %s", strerror (errno));
+
+	char *path = xstrdup (argv[0]);
+
+	if ((g_inotify_fd = inotify_init1 (IN_NONBLOCK)) < 0)
+		exit_fatal ("inotify_init1: %s", strerror (errno));
+	if ((g_inotify_wd = inotify_add_watch (g_inotify_fd,
+		dirname (path), IN_MOVED_TO | IN_CLOSE_WRITE)) < 0)
+		exit_fatal ("inotify_add_watch: %s", strerror (errno));
+
+	free (path);
+	char *base = basename ((path = xstrdup (argv[0])));
+	spawn (argv);
+
+	do
+	{
+		fd_set r; FD_SET (g_inotify_fd, &r);
+		(void) pselect (g_inotify_fd + 1, &r, NULL, NULL, NULL, &orig);
+		handle_file_change (base);
+	}
+	while (check_child_death (argv));
+
+	free (path);
+	close (g_inotify_fd);
+	return EXIT_SUCCESS;
+}
diff --git a/siprandom.c b/siprandom.c
index 690772c..1a4d336 100644
--- a/siprandom.c
+++ b/siprandom.c
@@ -34,7 +34,7 @@ parse_program_arguments (int argc, char **argv)
 	};
 
 	struct opt_handler oh =
-		opt_handler_make (argc, argv, opts, "CONFIG", "PRNG.");
+		opt_handler_make (argc, argv, opts, NULL, "PRNG.");
 
 	int c;
 	while ((c = opt_handler_get (&oh)) != -1)