test/zdtm: mount a new tmpfs to the zdtm root /dev

The current file system can be mounted with nodev.

Fixes checkpoint-restore#2441

Signed-off-by: Andrei Vagin <[email protected]>

test/zdtm.py

@@ -74,7 +74,9 @@ def traceit(f, e, a):
 def clean_tests_root():
     global tests_root
     if tests_root and tests_root[0] == os.getpid():
+        subprocess.call(["./umount2", os.path.join(tests_root[1], "dev")])
         os.rmdir(os.path.join(tests_root[1], "root"))
+        os.rmdir(os.path.join(tests_root[1], "dev"))
         os.rmdir(tests_root[1])
 
 
@@ -85,8 +87,11 @@ def make_tests_root():
         tests_root = (os.getpid(), tempfile.mkdtemp("", "criu-root-", tmpdir))
         atexit.register(clean_tests_root)
         os.mkdir(os.path.join(tests_root[1], "root"))
+        devpath = os.path.join(tests_root[1], "dev")
+        os.mkdir(devpath)
+        subprocess.check_call(["mount", "-t", "tmpfs", "criu-test-dev", devpath])
     os.chmod(tests_root[1], 0o777)
-    return os.path.join(tests_root[1], "root")
+    return os.path.join(tests_root[1], "root"), os.path.join(tests_root[1], "dev")
 
 
 # Report generation
@@ -182,15 +187,16 @@ def clean():
 
 class ns_flavor:
     __root_dirs = [
-        "/bin", "/sbin", "/etc", "/lib", "/lib64", "/dev", "/dev/pts",
-        "/dev/net", "/tmp", "/usr", "/proc", "/run"
+        "/bin", "/sbin", "/etc", "/lib", "/lib64", "/dev",
+        "/tmp", "/usr", "/proc", "/run"
     ]
+    __dev_dirs = ["pts", "net"]
 
     def __init__(self, opts):
         self.name = "ns"
         self.ns = True
         self.uns = False
-        self.root = make_tests_root()
+        self.root, self.devpath = make_tests_root()
         self.root_mounted = False
 
     def __copy_one(self, fname):
@@ -236,15 +242,14 @@ def __copy_libs(self, binary):
             self.__copy_one(lib)
 
     def __mknod(self, name, rdev=None):
-        name = "/dev/" + name
         if not rdev:
-            if not os.access(name, os.F_OK):
+            if not os.access(os.path.join("/dev", name), os.F_OK):
                 print("Skipping %s at root" % name)
                 return
             else:
-                rdev = os.stat(name).st_rdev
+                rdev = os.stat(os.path.join("/dev", name)).st_rdev
 
-        name = self.root + name
+        name = os.path.join(self.devpath, name)
         os.mknod(name, stat.S_IFCHR, rdev)
         os.chmod(name, 0o666)
 
@@ -256,6 +261,10 @@ def __construct_root(self):
         for ldir in ["/bin", "/sbin", "/lib", "/lib64"]:
             os.symlink(".." + ldir, self.root + "/usr" + ldir)
 
+    def __construct_dev(self):
+        for dir in self.__dev_dirs:
+            os.mkdir(os.path.join(self.devpath, dir))
+            os.chmod(os.path.join(self.devpath, dir), 0o777)
         self.__mknod("tty", os.makedev(5, 0))
         self.__mknod("null", os.makedev(1, 3))
         self.__mknod("net/tun")
@@ -283,6 +292,9 @@ def init(self, l_bins, x_bins):
                     self.__construct_root()
                     os.mknod(self.root + "/.constructed", stat.S_IFREG | 0o600)
 
+        if not os.access(self.devpath + "/.constructed", os.F_OK):
+            self.__construct_dev()
+            os.mknod(self.devpath + "/.constructed", stat.S_IFREG | 0o600)
         for b in l_bins:
             self.__copy_libs(b)
         for b in x_bins:
@@ -480,6 +492,7 @@ def start(self):
         if self.__flavor.ns:
             env['ZDTM_NEWNS'] = "1"
             env['ZDTM_ROOT'] = self.__flavor.root
+            env['ZDTM_DEV'] = self.__flavor.devpath
             env['PATH'] = "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
             if self.__flavor.uns:
@@ -510,6 +523,7 @@ def start(self):
             # unprivileged users. The permissions here are set to test
             # this use case.
             os.chmod(os.path.dirname(self.__flavor.root), 0o700)
+            os.chmod(os.path.dirname(self.__flavor.devpath), 0o755)
 
     def kill(self, sig=signal.SIGKILL):
         self.__freezer.thaw()
@@ -587,12 +601,18 @@ def __getcropts(self):
         return opts
 
     def getdopts(self):
-        return self.__getcropts() + self.__freezer.getdopts(
-        ) + self.__desc.get('dopts', '').split()
+        opts = self.__getcropts() + self.__freezer.getdopts() + \
+            self.__desc.get('dopts', '').split()
+        if self.__flavor.ns:
+            opts += ["--external", "mnt[/dev]:ZDTM_DEV"]
+        return opts
 
     def getropts(self):
-        return self.__getcropts() + self.__freezer.getropts(
-        ) + self.__desc.get('ropts', '').split()
+        opts = self.__getcropts() + self.__freezer.getropts() + \
+            self.__desc.get('ropts', '').split()
+        if self.__flavor.ns:
+            opts += ["--external", "mnt[ZDTM_DEV]:%s" % self.__flavor.devpath]
+        return opts
 
     def unlink_pidfile(self):
         self.__pid = 0

test/zdtm/lib/ns.c

@@ -27,7 +27,7 @@ extern int pivot_root(const char *new_root, const char *put_old);
 static int prepare_mntns(void)
 {
 	int dfd, ret;
-	char *root, *criu_path;
+	char *root, *criu_path, *dev_path;
 	char path[PATH_MAX];
 
 	root = getenv("ZDTM_ROOT");
@@ -51,6 +51,15 @@ static int prepare_mntns(void)
 		return -1;
 	}
 
+	dev_path = getenv("ZDTM_DEV");
+	if (dev_path) {
+		snprintf(path, sizeof(path), "%s/dev", root);
+		if (mount(dev_path, path, NULL, MS_BIND | MS_REC, NULL)) {
+			pr_perror("Unable to mount %s",  path);
+			return -1;
+		}
+	}
+
 	criu_path = getenv("ZDTM_CRIU");
 	if (criu_path) {
 		snprintf(path, sizeof(path), "%s%s", root, criu_path);