zdtm: check that two continuous grow-down VMA-s are restored correctly

It's a special case, because if we've split the stack vma,
only the lowest one has the guard page.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/live/static/Makefile

@@ -100,6 +100,7 @@ TST_NOFILE	=				\
 		sk-netlink			\
 		mem-touch			\
 		grow_map			\
+		grow_map02			\
 		tun				\
 #		jobctl00			\
 

test/zdtm/live/static/grow_map02.c

+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
+#include <sys/wait.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that a few grow-down VMA-s are restored correctly";
+const char *test_author	= "Andrew Vagin <avagin@openvz.org>";
+
+int main(int argc, char **argv)
+{
+	char *start_addr, *grow_down;
+	test_init(argc, argv);
+
+	start_addr = mmap(NULL, PAGE_SIZE * 10, PROT_READ | PROT_WRITE,
+					MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (start_addr == MAP_FAILED) {
+		err("Can't mal a new region");
+		return 1;
+	}
+	munmap(start_addr, PAGE_SIZE * 10);
+
+	grow_down = mmap(start_addr + PAGE_SIZE * 3, PAGE_SIZE * 3,
+			 PROT_READ | PROT_WRITE,
+			 MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED | MAP_GROWSDOWN, -1, 0);
+	if (grow_down == MAP_FAILED) {
+		err("Can't mal a new region");
+		return 1;
+	}
+
+	grow_down[0 * PAGE_SIZE] = 'x';
+	grow_down[1 * PAGE_SIZE] = 'y';
+	grow_down[2 * PAGE_SIZE] = 'z';
+
+	/*
+	 * Split the grow-down vma on three parts.
+	 * Only the irst one will have a guard page
+	 */
+	if (mprotect(grow_down + PAGE_SIZE, PAGE_SIZE, PROT_READ)) {
+		err("Can't change set protection on a region of memory");
+		return 1;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	test_msg("%c %c %c\n", grow_down[0 * PAGE_SIZE],
+		 grow_down[1 * PAGE_SIZE], grow_down[2 * PAGE_SIZE]);
+
+	if (grow_down[0 * PAGE_SIZE] != 'x')
+		return 1;
+	if (grow_down[1 * PAGE_SIZE] != 'y')
+		return 1;
+	if (grow_down[2 * PAGE_SIZE] != 'z')
+		return 1;
+
+	pass();
+
+	return 0;
+}