8287007: [cgroups] Consistently use stringStream throughout parsing code

Reviewed-by: iklam

src/hotspot/os/linux/cgroupV1Subsystem_linux.cpp

@@ -37,40 +37,26 @@
  * on the contents of the mountinfo and cgroup files.
  */
 void CgroupV1Controller::set_subsystem_path(char *cgroup_path) {
-  char buf[MAXPATHLEN+1];
+  stringStream ss;
   if (_root != NULL && cgroup_path != NULL) {
     if (strcmp(_root, "/") == 0) {
-      int buflen;
-      strncpy(buf, _mount_point, MAXPATHLEN);
-      buf[MAXPATHLEN-1] = '\0';
+      ss.print_raw(_mount_point);
       if (strcmp(cgroup_path,"/") != 0) {
-        buflen = strlen(buf);
-        if ((buflen + strlen(cgroup_path)) > (MAXPATHLEN-1)) {
-          return;
-        }
-        strncat(buf, cgroup_path, MAXPATHLEN-buflen);
-        buf[MAXPATHLEN-1] = '\0';
+        ss.print_raw(cgroup_path);
       }
-      _path = os::strdup(buf);
+      _path = os::strdup(ss.base());
     } else {
       if (strcmp(_root, cgroup_path) == 0) {
-        strncpy(buf, _mount_point, MAXPATHLEN);
-        buf[MAXPATHLEN-1] = '\0';
-        _path = os::strdup(buf);
+        ss.print_raw(_mount_point);
+        _path = os::strdup(ss.base());
       } else {
         char *p = strstr(cgroup_path, _root);
         if (p != NULL && p == _root) {
           if (strlen(cgroup_path) > strlen(_root)) {
-            int buflen;
-            strncpy(buf, _mount_point, MAXPATHLEN);
-            buf[MAXPATHLEN-1] = '\0';
-            buflen = strlen(buf);
-            if ((buflen + strlen(cgroup_path) - strlen(_root)) > (MAXPATHLEN-1)) {
-              return;
-            }
-            strncat(buf, cgroup_path + strlen(_root), MAXPATHLEN-buflen);
-            buf[MAXPATHLEN-1] = '\0';
-            _path = os::strdup(buf);
+            ss.print_raw(_mount_point);
+            const char* cg_path_sub = cgroup_path + strlen(_root);
+            ss.print_raw(cg_path_sub);
+            _path = os::strdup(ss.base());
           }
         }
       }

src/hotspot/os/linux/cgroupV2Subsystem_linux.cpp

@@ -213,17 +213,12 @@ char* CgroupV2Subsystem::mem_limit_val() {
 }
 
 char* CgroupV2Controller::construct_path(char* mount_path, char *cgroup_path) {
-  char buf[MAXPATHLEN+1];
-  int buflen;
-  strncpy(buf, mount_path, MAXPATHLEN);
-  buf[MAXPATHLEN] = '\0';
-  buflen = strlen(buf);
-  if ((buflen + strlen(cgroup_path)) > MAXPATHLEN) {
-    return NULL;
+  stringStream ss;
+  ss.print_raw(mount_path);
+  if (strcmp(cgroup_path, "/") != 0) {
+    ss.print_raw(cgroup_path);
   }
-  strncat(buf, cgroup_path, MAXPATHLEN-buflen);
-  buf[MAXPATHLEN] = '\0';
-  return os::strdup(buf);
+  return os::strdup(ss.base());
 }
 
 char* CgroupV2Subsystem::pids_max_val() {

test/hotspot/gtest/runtime/test_os_linux_cgroups.cpp

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2022, Red Hat, Inc.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "precompiled.hpp"
+
+#ifdef LINUX
+
+#include "cgroupV1Subsystem_linux.hpp"
+#include "cgroupV2Subsystem_linux.hpp"
+#include "unittest.hpp"
+
+typedef struct {
+  const char* mount_path;
+  const char* root_path;
+  const char* cgroup_path;
+  const char* expected_path;
+} TestCase;
+
+TEST(os_linux_cgroup, set_cgroupv1_subsystem_path) {
+  TestCase host = {
+    "/sys/fs/cgroup/memory",                                             // mount_path
+    "/",                                                                 // root_path
+    "/user.slice/user-1000.slice/user@1000.service",                     // cgroup_path
+    "/sys/fs/cgroup/memory/user.slice/user-1000.slice/user@1000.service" // expected_path
+  };
+  TestCase container_engine = {
+    "/sys/fs/cgroup/mem",                            // mount_path
+    "/user.slice/user-1000.slice/user@1000.service", // root_path
+    "/user.slice/user-1000.slice/user@1000.service", // cgroup_path
+    "/sys/fs/cgroup/mem"                             // expected_path
+  };
+  int length = 2;
+  TestCase* testCases[] = { &host,
+                            &container_engine };
+  for (int i = 0; i < length; i++) {
+    CgroupV1Controller* ctrl = new CgroupV1Controller( (char*)testCases[i]->root_path,
+                                                       (char*)testCases[i]->mount_path);
+    ctrl->set_subsystem_path((char*)testCases[i]->cgroup_path);
+    ASSERT_STREQ(testCases[i]->expected_path, ctrl->subsystem_path());
+  }
+}
+
+TEST(os_linux_cgroup, set_cgroupv2_subsystem_path) {
+  TestCase at_mount_root = {
+    "/sys/fs/cgroup",       // mount_path
+    NULL,                   // root_path, ignored
+    "/",                    // cgroup_path
+    "/sys/fs/cgroup"        // expected_path
+  };
+  TestCase sub_path = {
+    "/sys/fs/cgroup",       // mount_path
+    NULL,                   // root_path, ignored
+    "/foobar",              // cgroup_path
+    "/sys/fs/cgroup/foobar" // expected_path
+  };
+  int length = 2;
+  TestCase* testCases[] = { &at_mount_root,
+                            &sub_path };
+  for (int i = 0; i < length; i++) {
+    CgroupV2Controller* ctrl = new CgroupV2Controller( (char*)testCases[i]->mount_path,
+                                                       (char*)testCases[i]->cgroup_path);
+    ASSERT_STREQ(testCases[i]->expected_path, ctrl->subsystem_path());
+  }
+}
+
+#endif

test/jdk/jdk/internal/platform/cgroup/CgroupV1SubsystemControllerTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2022, Red Hat, Inc.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import jdk.internal.platform.cgroupv1.CgroupV1SubsystemController;
+
+/*
+ * @test
+ * @key cgroups
+ * @requires os.family == "linux"
+ * @modules java.base/jdk.internal.platform.cgroupv1
+ * @library /test/lib
+ * @run junit/othervm CgroupV1SubsystemControllerTest
+ */
+public class CgroupV1SubsystemControllerTest {
+
+
+    /*
+     * Common case: Containers
+     */
+    @Test
+    public void testCgPathEqualsRoot() {
+        String root = "/machine.slice/libpod-7145e2e7dbeab5aa96bd79beed79eda286a2d299a0ee386e704cad9f53a70979.scope";
+        String mountPoint = "/somemount";
+        CgroupV1SubsystemController ctrl = new CgroupV1SubsystemController(root, mountPoint);
+        ctrl.setPath("/machine.slice/libpod-7145e2e7dbeab5aa96bd79beed79eda286a2d299a0ee386e704cad9f53a70979.scope");
+        assertEquals(mountPoint, ctrl.path());
+    }
+
+    /*
+     * Common case: Host
+     */
+    @Test
+    public void testCgPathNonEmptyRoot() {
+        String root = "/";
+        String mountPoint = "/sys/fs/cgroup/memory";
+        CgroupV1SubsystemController ctrl = new CgroupV1SubsystemController(root, mountPoint);
+        String cgroupPath = "/subpath";
+        ctrl.setPath(cgroupPath);
+        String expectedPath = mountPoint + cgroupPath;
+        assertEquals(expectedPath, ctrl.path());
+    }
+
+    @Test
+    public void testCgPathSubstring() {
+        String root = "/foo/bar/baz";
+        String mountPoint = "/sys/fs/cgroup/memory";
+        CgroupV1SubsystemController ctrl = new CgroupV1SubsystemController(root, mountPoint);
+        String cgroupPath = "/foo/bar/baz/some";
+        ctrl.setPath(cgroupPath);
+        String expectedPath = mountPoint + "/some";
+        assertEquals(expectedPath, ctrl.path());
+    }
+
+}

test/jdk/jdk/internal/platform/cgroup/CgroupV2SubsystemControllerTest.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2022, Red Hat, Inc.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import jdk.internal.platform.cgroupv2.CgroupV2SubsystemController;
+
+/*
+ * @test
+ * @key cgroups
+ * @requires os.family == "linux"
+ * @modules java.base/jdk.internal.platform.cgroupv2
+ * @library /test/lib
+ * @run junit/othervm CgroupV2SubsystemControllerTest
+ */
+public class CgroupV2SubsystemControllerTest {
+
+
+    /*
+     * Common case: No nested cgroup path (i.e. at the unified root)
+     */
+    @Test
+    public void testCgPathAtRoot() {
+        String mountPoint = "/sys/fs/cgroup";
+        String cgroupPath = "/";
+        CgroupV2SubsystemController ctrl = new CgroupV2SubsystemController(mountPoint, cgroupPath);
+        assertEquals(mountPoint, ctrl.path());
+    }
+
+    /*
+     * Cgroup path at a sub-path
+     */
+    @Test
+    public void testCgPathNonEmptyRoot() {
+        String mountPoint = "/sys/fs/cgroup";
+        String cgroupPath = "/foobar";
+        CgroupV2SubsystemController ctrl = new CgroupV2SubsystemController(mountPoint, cgroupPath);
+        String expectedPath = mountPoint + cgroupPath;
+        assertEquals(expectedPath, ctrl.path());
+    }
+
+}