X-Git-Url: http://git.sven.stormbind.net/?p=sven%2Fjattach.git;a=blobdiff_plain;f=src%2Fposix%2Fjattach_hotspot.c;fp=src%2Fposix%2Fjattach_hotspot.c;h=e23e4609a0e3dcb31e38ad1e12475f31b1413cea;hp=0000000000000000000000000000000000000000;hb=91eb05a0b9cfabc7670a4f0f1e2b8083307a2fca;hpb=b330d6f5cff47911c6b1faf488d0d2791e1a181b

diff --git a/src/posix/jattach_hotspot.c b/src/posix/jattach_hotspot.c
new file mode 100644
index 0000000..e23e460
--- /dev/null
+++ b/src/posix/jattach_hotspot.c
@@ -0,0 +1,184 @@
+/*
+ * 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 <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <time.h>
+#include <unistd.h>
+#include "psutil.h"
+
+
+// Check if remote JVM has already opened socket for Dynamic Attach
+static int check_socket(int pid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.java_pid%d", tmp_path, pid);
+
+    struct stat stats;
+    return stat(path, &stats) == 0 && S_ISSOCK(stats.st_mode) ? 0 : -1;
+}
+
+// Check if a file is owned by current user
+static uid_t get_file_owner(const char* path) {
+    struct stat stats;
+    return stat(path, &stats) == 0 ? stats.st_uid : (uid_t)-1;
+}
+
+// Force remote JVM to start Attach listener.
+// HotSpot will start Attach listener in response to SIGQUIT if it sees .attach_pid file
+static int start_attach_mechanism(int pid, int nspid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "/proc/%d/cwd/.attach_pid%d", nspid, nspid);
+
+    int fd = creat(path, 0660);
+    if (fd == -1 || (close(fd) == 0 && get_file_owner(path) != geteuid())) {
+        // Some mounted filesystems may change the ownership of the file.
+        // JVM will not trust such file, so it's better to remove it and try a different path
+        unlink(path);
+
+        // Failed to create attach trigger in current directory. Retry in /tmp
+        snprintf(path, sizeof(path), "%s/.attach_pid%d", tmp_path, nspid);
+        fd = creat(path, 0660);
+        if (fd == -1) {
+            return -1;
+        }
+        close(fd);
+    }
+
+    // We have to still use the host namespace pid here for the kill() call
+    kill(pid, SIGQUIT);
+
+    // Start with 20 ms sleep and increment delay each iteration. Total timeout is 6000 ms
+    struct timespec ts = {0, 20000000};
+    int result;
+    do {
+        nanosleep(&ts, NULL);
+        result = check_socket(nspid);
+    } while (result != 0 && (ts.tv_nsec += 20000000) < 500000000);
+
+    unlink(path);
+    return result;
+}
+
+// Connect to UNIX domain socket created by JVM for Dynamic Attach
+static int connect_socket(int pid) {
+    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
+    if (fd == -1) {
+        return -1;
+    }
+
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+
+    int bytes = snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.java_pid%d", tmp_path, pid);
+    if (bytes >= sizeof(addr.sun_path)) {
+        addr.sun_path[sizeof(addr.sun_path) - 1] = 0;
+    }
+
+    if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
+        close(fd);
+        return -1;
+    }
+    return fd;
+}
+
+// Send command with arguments to socket
+static int write_command(int fd, int argc, char** argv) {
+    // Protocol version
+    if (write(fd, "1", 2) <= 0) {
+        return -1;
+    }
+
+    int i;
+    for (i = 0; i < 4; i++) {
+        const char* arg = i < argc ? argv[i] : "";
+        if (write(fd, arg, strlen(arg) + 1) <= 0) {
+            return -1;
+        }
+    }
+    return 0;
+}
+
+// Mirror response from remote JVM to stdout
+static int read_response(int fd, int argc, char** argv) {
+    char buf[8192];
+    ssize_t bytes = read(fd, buf, sizeof(buf) - 1);
+    if (bytes == 0) {
+        fprintf(stderr, "Unexpected EOF reading response\n");
+        return 1;
+    } else if (bytes < 0) {
+        perror("Error reading response");
+        return 1;
+    }
+
+    // First line of response is the command result code
+    buf[bytes] = 0;
+    int result = atoi(buf);
+
+    // Special treatment of 'load' command
+    if (result == 0 && argc > 0 && strcmp(argv[0], "load") == 0) {
+        size_t total = bytes;
+        while (total < sizeof(buf) - 1 && (bytes = read(fd, buf + total, sizeof(buf) - 1 - total)) > 0) {
+            total += (size_t)bytes;
+        }
+        bytes = total;
+
+        // The second line is the result of 'load' command; since JDK 9 it starts from "return code: "
+        buf[bytes] = 0;
+        result = atoi(strncmp(buf + 2, "return code: ", 13) == 0 ? buf + 15 : buf + 2);
+    }
+
+    // Mirror JVM response to stdout
+    printf("JVM response code = ");
+    do {
+        fwrite(buf, 1, bytes, stdout);
+        bytes = read(fd, buf, sizeof(buf));
+    } while (bytes > 0);
+    printf("\n");
+
+    return result;
+}
+
+int jattach_hotspot(int pid, int nspid, int argc, char** argv) {
+    if (check_socket(nspid) != 0 && start_attach_mechanism(pid, nspid) != 0) {
+        perror("Could not start attach mechanism");
+        return 1;
+    }
+
+    int fd = connect_socket(nspid);
+    if (fd == -1) {
+        perror("Could not connect to socket");
+        return 1;
+    }
+
+    printf("Connected to remote JVM\n");
+
+    if (write_command(fd, argc, argv) != 0) {
+        perror("Error writing to socket");
+        close(fd);
+        return 1;
+    }
+
+    int result = read_response(fd, argc, argv);
+    close(fd);
+
+    return result;
+}