criu: use strsignal to describe kill reason

Where it's possible to use glibc.
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-restore.c

@@ -1304,7 +1304,8 @@ err:
 	if (exit)
 		pr_err("%d exited, status=%d\n", pid, status);
 	else
-		pr_err("%d killed by signal %d\n", pid, status);
+		pr_err("%d killed by signal %d: %s\n",
+			pid, status, strsignal(status));
 
 	futex_abort_and_wake(&task_entries->nr_in_progress);
 }

criu/cr-service.c

@@ -955,8 +955,8 @@ static void reap_worker(int signo)
 			pr_info("Worker(pid %d) exited with %d\n",
 				pid, WEXITSTATUS(status));
 		else if (WIFSIGNALED(status))
-			pr_info("Worker(pid %d) was killed by %d\n",
-				pid, WTERMSIG(status));
+			pr_info("Worker(pid %d) was killed by %d: %s\n", pid,
+				WTERMSIG(status), strsignal(WTERMSIG(status)));
 	}
 }
 

criu/parasite-syscall.c

@@ -401,7 +401,8 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 	if (WIFEXITED(status))
 		pr_err("%d exited with %d unexpectedly\n", pid, WEXITSTATUS(status));
 	else if (WIFSIGNALED(status))
-		pr_err("%d was killed by %d unexpectedly\n", pid, WTERMSIG(status));
+		pr_err("%d was killed by %d unexpectedly: %s\n",
+			pid, WTERMSIG(status), strsignal(WTERMSIG(status)));
 	else if (WIFSTOPPED(status))
 		pr_err("%d was stopped by %d unexpectedly\n", pid, WSTOPSIG(status));
 

criu/seize.c

@@ -446,7 +446,8 @@ static void pstree_wait(struct pstree_item *root_item)
 				break;
 			} else {
 				if (!WIFSIGNALED(status) || WTERMSIG(status) != SIGKILL) {
-					pr_err("Unexpected exit code %d of %d\n", status, pid);
+					pr_err("Unexpected exit code %d of %d: %s\n",
+						status, pid, strsignal(status));
 					BUG();
 				}
 			}

criu/util.c

@@ -670,7 +670,8 @@ out_chld:
 				pr_err("exited, status=%d\n", WEXITSTATUS(status));
 			break;
 		} else if (WIFSIGNALED(status)) {
-			pr_err("killed by signal %d\n", WTERMSIG(status));
+			pr_err("killed by signal %d: %s\n", WTERMSIG(status),
+				strsignal(WTERMSIG(status)));
 			break;
 		} else if (WIFSTOPPED(status)) {
 			pr_err("stopped by signal %d\n", WSTOPSIG(status));