8202884: SA: Attach/detach might fail on Linux if debugee application create/destroy threads during attaching
While doing a ptrace attach, do not attach to threads which are in the process of exiting or are zombies -- skip these threads. Reviewed-by: jcbeyler, ysuenaga
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parent
35bd56fcdf
commit
12355f9ca8
src/jdk.hotspot.agent/linux/native/libsaproc
@ -274,6 +274,26 @@ thread_info* add_thread_info(struct ps_prochandle* ph, pthread_t pthread_id, lwp
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return newthr;
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}
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void delete_thread_info(struct ps_prochandle* ph, thread_info* thr_to_be_removed) {
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thread_info* current_thr = ph->threads;
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if (thr_to_be_removed == ph->threads) {
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ph->threads = ph->threads->next;
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} else {
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thread_info* previous_thr;
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while (current_thr && current_thr != thr_to_be_removed) {
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previous_thr = current_thr;
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current_thr = current_thr->next;
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}
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if (current_thr == NULL) {
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print_error("Could not find the thread to be removed");
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return;
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}
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previous_thr->next = current_thr->next;
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}
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ph->num_threads--;
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free(current_thr);
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}
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// struct used for client data from thread_db callback
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struct thread_db_client_data {
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@ -296,6 +316,11 @@ static int thread_db_callback(const td_thrhandle_t *th_p, void *data) {
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print_debug("thread_db : pthread %d (lwp %d)\n", ti.ti_tid, ti.ti_lid);
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if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE) {
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print_debug("Skipping pthread %d (lwp %d)\n", ti.ti_tid, ti.ti_lid);
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return TD_OK;
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}
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if (ptr->callback(ptr->ph, ti.ti_tid, ti.ti_lid) != true)
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return TD_ERR;
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -113,6 +113,9 @@ typedef bool (*thread_info_callback)(struct ps_prochandle* ph, pthread_t pid, lw
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// reads thread info using libthread_db and calls above callback for each thread
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bool read_thread_info(struct ps_prochandle* ph, thread_info_callback cb);
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// deletes a thread from the thread list
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void delete_thread_info(struct ps_prochandle* ph, thread_info* thr);
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// adds a new shared object to lib list, returns NULL on failure
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lib_info* add_lib_info(struct ps_prochandle* ph, const char* libname, uintptr_t base);
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@ -29,6 +29,7 @@
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#include <errno.h>
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#include <elf.h>
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#include <dirent.h>
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#include <ctype.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/ptrace.h>
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@ -46,6 +47,12 @@
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// This file has the libproc implementation specific to live process
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// For core files, refer to ps_core.c
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typedef enum {
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ATTACH_SUCCESS,
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ATTACH_FAIL,
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ATTACH_THREAD_DEAD
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} attach_state_t;
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static inline uintptr_t align(uintptr_t ptr, size_t size) {
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return (ptr & ~(size - 1));
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}
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@ -168,9 +175,10 @@ static bool ptrace_continue(pid_t pid, int signal) {
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// waits until the ATTACH has stopped the process
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// by signal SIGSTOP
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static bool ptrace_waitpid(pid_t pid) {
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static attach_state_t ptrace_waitpid(pid_t pid) {
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int ret;
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int status;
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errno = 0;
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while (true) {
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// Wait for debuggee to stop.
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ret = waitpid(pid, &status, 0);
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@ -185,15 +193,15 @@ static bool ptrace_waitpid(pid_t pid) {
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// will go to sleep.
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if (WSTOPSIG(status) == SIGSTOP) {
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// Debuggee stopped by SIGSTOP.
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return true;
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return ATTACH_SUCCESS;
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}
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if (!ptrace_continue(pid, WSTOPSIG(status))) {
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print_error("Failed to correctly attach to VM. VM might HANG! [PTRACE_CONT failed, stopped by %d]\n", WSTOPSIG(status));
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return false;
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return ATTACH_FAIL;
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}
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} else {
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print_debug("waitpid(): Child process exited/terminated (status = 0x%x)\n", status);
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return false;
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print_debug("waitpid(): Child process %d exited/terminated (status = 0x%x)\n", pid, status);
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return ATTACH_THREAD_DEAD;
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}
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} else {
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switch (errno) {
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@ -202,29 +210,89 @@ static bool ptrace_waitpid(pid_t pid) {
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break;
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case ECHILD:
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print_debug("waitpid() failed. Child process pid (%d) does not exist \n", pid);
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break;
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return ATTACH_THREAD_DEAD;
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case EINVAL:
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print_debug("waitpid() failed. Invalid options argument.\n");
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break;
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print_error("waitpid() failed. Invalid options argument.\n");
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return ATTACH_FAIL;
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default:
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print_debug("waitpid() failed. Unexpected error %d\n",errno);
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break;
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print_error("waitpid() failed. Unexpected error %d\n", errno);
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return ATTACH_FAIL;
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}
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return false;
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} // else
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} // while
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}
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// checks the state of the thread/process specified by "pid", by reading
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// in the 'State:' value from the /proc/<pid>/status file. From the proc
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// man page, "Current state of the process. One of "R (running)",
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// "S (sleeping)", "D (disk sleep)", "T (stopped)", "T (tracing stop)",
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// "Z (zombie)", or "X (dead)"." Assumes that the thread is dead if we
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// don't find the status file or if the status is 'X' or 'Z'.
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static bool process_doesnt_exist(pid_t pid) {
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char fname[32];
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char buf[30];
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FILE *fp = NULL;
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const char state_string[] = "State:";
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sprintf(fname, "/proc/%d/status", pid);
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fp = fopen(fname, "r");
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if (fp == NULL) {
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print_debug("can't open /proc/%d/status file\n", pid);
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// Assume the thread does not exist anymore.
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return true;
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}
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bool found_state = false;
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size_t state_len = strlen(state_string);
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while (fgets(buf, sizeof(buf), fp) != NULL) {
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char *state = NULL;
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if (strncmp (buf, state_string, state_len) == 0) {
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found_state = true;
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state = buf + state_len;
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// Skip the spaces
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while (isspace(*state)) {
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state++;
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}
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// A state value of 'X' indicates that the thread is dead. 'Z'
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// indicates that the thread is a zombie.
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if (*state == 'X' || *state == 'Z') {
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fclose (fp);
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return true;
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}
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break;
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}
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}
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// If the state value is not 'X' or 'Z', the thread exists.
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if (!found_state) {
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// We haven't found the line beginning with 'State:'.
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// Assuming the thread exists.
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print_error("Could not find the 'State:' string in the /proc/%d/status file\n", pid);
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}
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fclose (fp);
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return false;
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}
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// attach to a process/thread specified by "pid"
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static bool ptrace_attach(pid_t pid, char* err_buf, size_t err_buf_len) {
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static attach_state_t ptrace_attach(pid_t pid, char* err_buf, size_t err_buf_len) {
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errno = 0;
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if (ptrace(PTRACE_ATTACH, pid, NULL, NULL) < 0) {
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if (errno == EPERM || errno == ESRCH) {
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// Check if the process/thread is exiting or is a zombie
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if (process_doesnt_exist(pid)) {
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print_debug("Thread with pid %d does not exist\n", pid);
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return ATTACH_THREAD_DEAD;
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}
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}
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char buf[200];
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char* msg = strerror_r(errno, buf, sizeof(buf));
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snprintf(err_buf, err_buf_len, "ptrace(PTRACE_ATTACH, ..) failed for %d: %s", pid, msg);
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print_debug("%s\n", err_buf);
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return false;
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print_error("%s\n", err_buf);
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return ATTACH_FAIL;
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} else {
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return ptrace_waitpid(pid);
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attach_state_t wait_ret = ptrace_waitpid(pid);
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if (wait_ret == ATTACH_THREAD_DEAD) {
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print_debug("Thread with pid %d does not exist\n", pid);
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}
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return wait_ret;
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}
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}
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@ -378,16 +446,20 @@ JNIEXPORT struct ps_prochandle* JNICALL
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Pgrab(pid_t pid, char* err_buf, size_t err_buf_len, bool is_in_container) {
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struct ps_prochandle* ph = NULL;
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thread_info* thr = NULL;
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attach_state_t attach_status = ATTACH_SUCCESS;
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if ( (ph = (struct ps_prochandle*) calloc(1, sizeof(struct ps_prochandle))) == NULL) {
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snprintf(err_buf, err_buf_len, "can't allocate memory for ps_prochandle");
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print_debug("%s\n", err_buf);
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return NULL;
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snprintf(err_buf, err_buf_len, "can't allocate memory for ps_prochandle");
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print_debug("%s\n", err_buf);
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return NULL;
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}
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if (ptrace_attach(pid, err_buf, err_buf_len) != true) {
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free(ph);
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return NULL;
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if ((attach_status = ptrace_attach(pid, err_buf, err_buf_len)) != ATTACH_SUCCESS) {
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if (attach_status == ATTACH_THREAD_DEAD) {
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print_error("The process with pid %d does not exist.\n", pid);
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}
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free(ph);
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return NULL;
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}
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// initialize ps_prochandle
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@ -431,14 +503,23 @@ Pgrab(pid_t pid, char* err_buf, size_t err_buf_len, bool is_in_container) {
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// attach to the threads
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thr = ph->threads;
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while (thr) {
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// don't attach to the main thread again
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if (ph->pid != thr->lwp_id && ptrace_attach(thr->lwp_id, err_buf, err_buf_len) != true) {
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// even if one attach fails, we get return NULL
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Prelease(ph);
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return NULL;
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}
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thr = thr->next;
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thread_info* current_thr = thr;
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thr = thr->next;
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// don't attach to the main thread again
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if (ph->pid != current_thr->lwp_id) {
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if ((attach_status = ptrace_attach(current_thr->lwp_id, err_buf, err_buf_len)) != ATTACH_SUCCESS) {
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if (attach_status == ATTACH_THREAD_DEAD) {
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// Remove this thread from the threads list
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delete_thread_info(ph, current_thr);
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}
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else {
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Prelease(ph);
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return NULL;
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} // ATTACH_THREAD_DEAD
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} // !ATTACH_SUCCESS
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}
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}
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return ph;
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}
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