zdtm: Add zombie01 test

Create a zombie with specific pgid and check that
pgid remains the same after restore.

This test hangs criu restore without any of two previous patches:
1)without "restore: Call prepare_fds() in restore_one_zombie()"
  in 100% cases;

2)without "restore: Split restore_one_helper() and wait exiting
  zombie children" fail is racy, but you can add something like

criu/cr-restore.c:
## -1130,6 +1130,8 @@ static int restore_one_zombie(CoreEntry *core)

        if (task_entries != NULL) {
                restore_finish_stage(task_entries, CR_STATE_RESTORE);
+               if (current->parent->pid->state == TASK_ALIVE)
+                       sleep(2);
                zombie_prepare_signals();
        }

and it will fail with almost 100% probability.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm/static/Makefile

@@ -10,6 +10,7 @@ TST_NOFILE	:=				\
 		caps00				\
 		wait00				\
 		zombie00			\
+		zombie01			\
 		fpu00				\
 		fpu01				\
 		arm-neon00			\

test/zdtm/static/zombie01.c

+#include <sched.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <signal.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that zombie pgid is restored";
+const char *test_author	= "Kirill Tkhai <ktkhai@virtuozzo.com>";
+
+int main(int argc, char **argv)
+{
+	pid_t pid, pgrp;
+	siginfo_t info;
+	int status;
+
+	test_init(argc, argv);
+
+	pid = fork();
+	if (pid < 0) {
+		fail("fork");
+		exit(1);
+	}
+
+	if (!pid) {
+		/* Child */
+		if (setpgid(0, 0) < 0) {
+			fail("setpgid");
+			exit(1);
+		}
+		pid = sys_clone_unified(CLONE_PARENT|SIGCHLD, NULL, NULL, NULL, 0);
+		if (pid < 0) {
+			fail("fork");
+			exit(1);
+		}
+
+		exit(0);
+	}
+
+	if (waitpid(pid, &status, 0) < 0) {
+		fail("waitpid");
+		exit(1);
+	}
+	if (!WIFEXITED(status) || WEXITSTATUS(status)) {
+		pr_err("Exited with problems: status=%d\n", status);
+		fail("fail");
+		exit(1);
+	}
+
+	if (waitid(P_ALL, 0, &info, WEXITED|WNOWAIT) < 0) {
+		fail("waitpid");
+		exit(1);
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	if (waitid(P_ALL, 0, &info, WEXITED|WNOWAIT) < 0) {
+		fail("waitpid");
+		exit(1);
+	}
+
+	pgrp = getpgid(info.si_pid);
+	if (pgrp < 0) {
+		fail("getpgrp");
+		exit(1);
+	}
+
+	if (pgrp != pid) {
+		pr_err("Wrong pgrp: %d != %d\n", pgrp, pid);
+		fail("fail");
+		exit(1);
+	}
+
+	pass();
+	return 0;
+}

test/zdtm/static/zombie01.desc

+{'flags': 'suid'}