--- /dev/null
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include "psutil.h"
+
+
+extern int is_openj9_process(int pid);
+extern int jattach_openj9(int pid, int nspid, int argc, char** argv);
+extern int jattach_hotspot(int pid, int nspid, int argc, char** argv);
+
+
+__attribute__((visibility("default")))
+int jattach(int pid, int argc, char** argv) {
+ uid_t my_uid = geteuid();
+ gid_t my_gid = getegid();
+ uid_t target_uid = my_uid;
+ gid_t target_gid = my_gid;
+ int nspid;
+ if (get_process_info(pid, &target_uid, &target_gid, &nspid) < 0) {
+ fprintf(stderr, "Process %d not found\n", pid);
+ return 1;
+ }
+
+ // Container support: switch to the target namespaces.
+ // Network and IPC namespaces are essential for OpenJ9 connection.
+ enter_ns(pid, "net");
+ enter_ns(pid, "ipc");
+ int mnt_changed = enter_ns(pid, "mnt");
+
+ // In HotSpot, dynamic attach is allowed only for the clients with the same euid/egid.
+ // If we are running under root, switch to the required euid/egid automatically.
+ if ((my_gid != target_gid && setegid(target_gid) != 0) ||
+ (my_uid != target_uid && seteuid(target_uid) != 0)) {
+ perror("Failed to change credentials to match the target process");
+ return 1;
+ }
+
+ get_tmp_path(mnt_changed > 0 ? nspid : pid);
+
+ // Make write() return EPIPE instead of abnormal process termination
+ signal(SIGPIPE, SIG_IGN);
+
+ if (is_openj9_process(nspid)) {
+ return jattach_openj9(pid, nspid, argc, argv);
+ } else {
+ return jattach_hotspot(pid, nspid, argc, argv);
+ }
+}
+
+int main(int argc, char** argv) {
+ if (argc < 3) {
+ printf("jattach " JATTACH_VERSION " built on " __DATE__ "\n"
+ "Copyright 2021 Andrei Pangin\n"
+ "\n"
+ "Usage: jattach <pid> <cmd> [args ...]\n"
+ "\n"
+ "Commands:\n"
+ " load threaddump dumpheap setflag properties\n"
+ " jcmd inspectheap datadump printflag agentProperties\n"
+ );
+ return 1;
+ }
+
+ int pid = atoi(argv[1]);
+ if (pid <= 0) {
+ fprintf(stderr, "%s is not a valid process ID\n", argv[1]);
+ return 1;
+ }
+
+ return jattach(pid, argc - 2, argv + 2);
+}