crtools: also print the current kernel version

In addition to writing the CRIU version to the log file this adds the
current kernel version to the log file:

(00.000008) Version: 3.5 (gitid v3.5-511-ga8cc6cf)
(00.000303) Running on node01 Linux 3.10.0-513.el7.x86_64 #1 SMP Tue Feb 29 06:78:90 EST 2017 x86_64

v2:
 - small changes as suggested by Dmitry (thanks)
Signed-off-by: Adrian Reber <areber@redhat.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/crtools.c

@@ -19,6 +19,8 @@
 
 #include <dlfcn.h>
 
+#include <sys/utsname.h>
+
 #include "int.h"
 #include "page.h"
 #include "common/compiler.h"
@@ -230,6 +232,20 @@ static void soccr_print_on_level(unsigned int loglevel, const char *format, ...)
 	va_end(args);
 }
 
+static void print_kernel_version(void)
+{
+	struct utsname buf;
+
+	if (uname(&buf) < 0) {
+		pr_perror("Reading kernel version failed!");
+		/* This pretty unlikely, just keep on running. */
+		return;
+	}
+
+	pr_info("Running on %s %s %s %s %s\n", buf.nodename, buf.sysname,
+		buf.release, buf.version, buf.machine);
+}
+
 int main(int argc, char *argv[], char *envp[])
 {
 
@@ -714,6 +730,9 @@ int main(int argc, char *argv[], char *envp[])
 	compel_log_init(vprint_on_level, log_get_loglevel());
 
 	pr_info("Version: %s (gitid %s)\n", CRIU_VERSION, CRIU_GITID);
+
+	print_kernel_version();
+
 	if (opts.deprecated_ok)
 		pr_debug("DEPRECATED ON\n");