add kill_all helper

This is similar to the sysvinit killall5 utility.  It should only be used
in service scripts, so it will not be installed in the path.

This closes #129.

src/rc/.gitignore

@@ -62,3 +62,4 @@ openrc
 openrc-init
 openrc-run
 openrc-shutdown
+kill_all

src/rc/Makefile

@@ -14,7 +14,7 @@ SRCS+=		rc-selinux.c
 endif
 
 ifeq (${OS},Linux)
-SRCS+=		openrc-init.c openrc-shutdown.c
+SRCS+=		kill_all.c openrc-init.c openrc-shutdown.c
 endif
 
 CLEANFILES=	version.h rc-selinux.o
@@ -44,6 +44,7 @@ RC_SBINPROGS=	mark_service_starting mark_service_started \
 		rc-abort swclock
 
 ifeq (${OS},Linux)
+RC_BINPROGS+= kill_all
 SBINPROGS+= openrc-init openrc-shutdown
 endif
 
@@ -99,6 +100,9 @@ checkpath: rc-selinux.o
 endif
 	${CC} ${LOCAL_CFLAGS} ${LOCAL_LDFLAGS} ${CFLAGS} ${LDFLAGS} -o $@ $^ ${LDADD}
 
+kill_all: kill_all.o _usage.o
+	${CC} ${LOCAL_CFLAGS} ${LOCAL_LDFLAGS} ${CFLAGS} ${LDFLAGS} -o $@ $^ ${LDADD}
+
 einfon einfo ewarnn ewarn eerrorn eerror ebegin eend ewend \
 eindent eoutdent esyslog eval_ecolors ewaitfile \
 veinfo vewarn vebegin veend vewend veindent veoutdent: do_e.o rc-misc.o

src/rc/kill_all.c

@@ -0,0 +1,250 @@
+/*
+ * kill_all.c
+ * Sends a signal to all processes on the system.
+ */
+
+/*
+ * Copyright (c) 2017 The OpenRC Authors.
+ * See the Authors file at the top-level directory of this distribution and
+ * https://github.com/OpenRC/openrc/blob/master/AUTHORS
+ *
+ * This file is part of OpenRC. It is subject to the license terms in
+ * the LICENSE file found in the top-level directory of this
+ * distribution and at https://github.com/OpenRC/openrc/blob/master/LICENSE
+ * This file may not be copied, modified, propagated, or distributed
+ *    except according to the terms contained in the LICENSE file.
+ */
+
+
+#include <dirent.h>
+#include <errno.h>
+#include <getopt.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "einfo.h"
+#include "rc.h"
+#include "rc-misc.h"
+#include "_usage.h"
+
+const char *applet = NULL;
+const char *extraopts = "[signal number]";
+const char *getoptstring = "do:" getoptstring_COMMON;
+const struct option longopts[] = {
+	{ "dry-run",        0, NULL, 'd' },
+	{ "omit",        1, NULL, 'o' },
+	longopts_COMMON
+};
+const char * const longopts_help[] = {
+	"print what would be done",
+	"omit this pid (can be repeated)",
+	longopts_help_COMMON
+};
+const char *usagestring = NULL;
+
+static int mount_proc(void)
+{
+	pid_t pid;
+	pid_t rc;
+	int status;
+
+	if (exists("/proc/version"))
+		return 0;
+	pid = fork();
+	switch(pid) {
+		case -1:
+			syslog(LOG_ERR, "Unable to fork");
+			return -1;
+			break;
+		case 0:
+			/* attempt to mount /proc */
+			execl("mount", "mount", "-t", "proc", "proc", "/proc", NULL);
+			syslog(LOG_ERR, "Unable to execute mount");
+			exit(1);
+			break;
+		default:
+			/* wait for child process */
+			while ((rc = wait(&status)) != pid)
+				if (rc < 0 && errno == ECHILD)
+					break;
+			if (rc != pid || WEXITSTATUS(status) != 0)
+				syslog(LOG_ERR, "mount returned non-zero exit status");
+			break;
+	}
+	if (! exists("/proc/version")) {
+		syslog(LOG_ERR, "Could not mount /proc");
+		return -1;
+	}
+	return 0;
+}
+
+static bool is_user_process(pid_t pid)
+{
+	char buf[PATH_MAX+1];
+	FILE *fp;
+	char path[PATH_MAX+1];
+	pid_t temp_pid;
+	bool user_process = true;
+
+	while (pid >0 && user_process) {
+		if (pid == 2) {
+			user_process = false;
+			continue;
+		}
+		snprintf(path, sizeof(path), "/proc/%d/status", pid);
+		fp = fopen(path, "r");
+		/*
+		 * if we could not open the file, the process disappeared, which
+		 * leaves us no way to determine for sure whether it was a user
+		 * process or kernel thread, so we say it is a kernel thread to
+		 * avoid accidentally killing it.
+		 */
+		if (!fp) {
+			user_process = false;
+			continue;
+		}
+		temp_pid = -1;
+		while (! feof(fp)) {
+			buf[0] = 0;
+			if (fgets(buf, sizeof(buf), fp))
+				sscanf(buf, "PPid: %d", &temp_pid);
+			else
+				break;
+		}
+		fclose(fp);
+		if (temp_pid == -1) {
+			syslog(LOG_ERR, "Unable to read pid from /proc/%d/status", pid);
+			user_process = false;
+			continue;
+		}
+		pid = temp_pid;
+	}
+	return user_process;
+}
+
+static int signal_processes(int sig, RC_STRINGLIST *omits, bool dryrun)
+{
+	sigset_t signals;
+	sigset_t oldsigs;
+	DIR *dir;
+	struct dirent	*d;
+	char buf[PATH_MAX+1];
+	pid_t pid;
+	int sendcount = 0;
+
+	kill(-1, SIGSTOP);
+	sigfillset(&signals);
+	sigemptyset(&oldsigs);
+	sigprocmask(SIG_SETMASK, &signals, &oldsigs);
+	/*
+	 * Open the /proc directory.
+	 * CWD must be /proc to avoid problems if / is affected by the killing
+	 * (i.e. depends on fuse).
+	 */
+	if (chdir("/proc") == -1) {
+		syslog(LOG_ERR, "chdir /proc failed");
+		sigprocmask(SIG_SETMASK, &oldsigs, NULL);
+		kill(-1, SIGCONT);
+		return -1;
+	}
+	dir = opendir(".");
+	if (!dir) {
+		syslog(LOG_ERR, "cannot opendir(/proc)");
+		sigprocmask(SIG_SETMASK, &oldsigs, NULL);
+		kill(-1, SIGCONT);
+		return -1;
+	}
+
+	/* Walk through the directory. */
+	while ((d = readdir(dir)) != NULL) {
+		/* Is this a process? */
+		pid = (pid_t) atoi(d->d_name);
+		if (pid == 0)
+			continue;
+
+		/* Is this a process we have been requested to omit? */
+		sprintf(buf, "%d", pid);
+		if (rc_stringlist_find(omits, buf))
+			continue;
+
+		/* Is this process in our session? */
+		if (getsid(getpid()) == getsid(pid))
+			continue;
+
+		/* Is this a kernel thread? */
+		if (!is_user_process(pid))
+			continue;
+
+		if (dryrun)
+			einfo("Would send signal %d to process %d", sig, pid);
+		else if (kill(pid, sig) == 0)
+			sendcount++;
+	}
+	closedir(dir);
+	sigprocmask(SIG_SETMASK, &oldsigs, NULL);
+	kill(-1, SIGCONT);
+	return sendcount;
+}
+
+int main(int argc, char **argv)
+{
+	char *arg = NULL;
+	int opt;
+	bool dryrun = false;
+	RC_STRINGLIST *omits = rc_stringlist_new();
+	int sig = SIGKILL;
+	char *here;
+	char *token;
+
+	/* Ensure that we are only quiet when explicitly told to be */
+	unsetenv("EINFO_QUIET");
+
+	applet = basename_c(argv[0]);
+	rc_stringlist_addu(omits, "1");
+	while ((opt = getopt_long(argc, argv, getoptstring,
+		    longopts, (int *) 0)) != -1)
+	{
+		switch (opt) {
+			case 'd':
+				dryrun = true;
+				break;
+			case 'o':
+				here = optarg;
+				while ((token = strsep(&here, ",;:"))) {
+					if ((pid_t) atoi(token) > 0)
+						rc_stringlist_addu(omits, token);
+					else {
+						eerror("Invalid omit pid value %s", token);
+						usage(EXIT_FAILURE);
+					}
+				}
+				break;
+			case_RC_COMMON_GETOPT
+		}
+	}
+
+	if (argc > optind) {
+	arg = argv[optind];
+	sig = atoi(arg);
+	if (sig <= 0 || sig > 31) {
+		rc_stringlist_free(omits);
+		eerror("Invalid signal %s", arg);
+		usage(EXIT_FAILURE);
+	}
+	}
+	
+	openlog(applet, LOG_CONS|LOG_PID, LOG_DAEMON);
+	if (mount_proc() != 0) {
+		rc_stringlist_free(omits);
+		eerrorx("Unable to mount /proc file system");
+	}
+	signal_processes(sig, omits, dryrun);
+	rc_stringlist_free(omits);
+	return 0;
+}