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1b2adad892
a kernel race condition.
305 lines
8.6 KiB
C
305 lines
8.6 KiB
C
/*
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* Server-side ptrace support
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*
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* Copyright (C) 1999 Alexandre Julliard
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "config.h"
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#include <assert.h>
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#include <errno.h>
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#include <stdio.h>
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#include <signal.h>
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#include <sys/types.h>
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#ifdef HAVE_SYS_PTRACE_H
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# include <sys/ptrace.h>
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#endif
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#ifdef HAVE_SYS_WAIT_H
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# include <sys/wait.h>
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#endif
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#include <unistd.h>
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#include "file.h"
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#include "process.h"
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#include "thread.h"
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#ifndef PTRACE_CONT
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#define PTRACE_CONT PT_CONTINUE
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#endif
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#ifndef PTRACE_SINGLESTEP
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#define PTRACE_SINGLESTEP PT_STEP
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#endif
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#ifndef PTRACE_ATTACH
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#define PTRACE_ATTACH PT_ATTACH
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#endif
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#ifndef PTRACE_DETACH
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#define PTRACE_DETACH PT_DETACH
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#endif
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#ifndef PTRACE_PEEKDATA
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#define PTRACE_PEEKDATA PT_READ_D
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#endif
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#ifndef PTRACE_POKEDATA
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#define PTRACE_POKEDATA PT_WRITE_D
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#endif
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#ifndef HAVE_SYS_PTRACE_H
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#define PT_CONTINUE 0
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#define PT_ATTACH 1
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#define PT_DETACH 2
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#define PT_READ_D 3
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#define PT_WRITE_D 4
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#define PT_STEP 5
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inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
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#endif /* HAVE_SYS_PTRACE_H */
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static const int use_ptrace = 1; /* set to 0 to disable ptrace */
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/* handle a status returned by wait4 */
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static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
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{
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if (WIFSTOPPED(status))
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{
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int sig = WSTOPSIG(status);
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if (debug_level && thread)
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fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
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if (sig != want_sig)
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{
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/* ignore other signals for now */
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if (thread && get_thread_single_step( thread ))
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ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
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else
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ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
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}
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return sig;
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}
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if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
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{
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thread->attached = 0;
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thread->unix_pid = -1;
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thread->unix_tid = -1;
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if (debug_level)
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{
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if (WIFSIGNALED(status))
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fprintf( stderr, "%04x: *exited* signal=%d\n",
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thread->id, WTERMSIG(status) );
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else
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fprintf( stderr, "%04x: *exited* status=%d\n",
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thread->id, WEXITSTATUS(status) );
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}
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}
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return 0;
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}
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/* wait4 wrapper to handle missing __WALL flag in older kernels */
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static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
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{
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#ifdef __WALL
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static int wall_flag = __WALL;
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for (;;)
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{
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pid_t ret = wait4( pid, status, options | wall_flag, usage );
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if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
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wall_flag = 0;
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}
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#else
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return wait4( pid, status, options, usage );
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#endif
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}
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/* handle a SIGCHLD signal */
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void sigchld_callback(void)
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{
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int pid, status;
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for (;;)
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{
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if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
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if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
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else break;
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}
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}
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/* wait for a ptraced child to get a certain signal */
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static int wait4_thread( struct thread *thread, int signal )
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{
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int res, status;
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start_watchdog();
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for (;;)
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{
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if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
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{
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if (errno == EINTR)
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{
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if (!watchdog_triggered()) continue;
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if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
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}
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else if (errno == ECHILD) /* must have died */
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{
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thread->unix_pid = -1;
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thread->unix_tid = -1;
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thread->attached = 0;
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}
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else perror( "wait4" );
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stop_watchdog();
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return 0;
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}
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res = handle_child_status( thread, res, status, signal );
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if (!res || res == signal) break;
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}
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stop_watchdog();
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return (thread->unix_pid != -1);
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}
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/* return the Unix pid to use in ptrace calls for a given thread */
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int get_ptrace_pid( struct thread *thread )
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{
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if (thread->unix_tid != -1) return thread->unix_tid;
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return thread->unix_pid;
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}
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/* send a Unix signal to a specific thread */
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int send_thread_signal( struct thread *thread, int sig )
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{
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int ret = -1;
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if (thread->unix_pid != -1)
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{
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if (thread->unix_tid != -1)
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{
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ret = tkill( thread->unix_tid, sig );
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if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
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}
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else ret = kill( thread->unix_pid, sig );
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if (ret == -1 && errno == ESRCH) /* thread got killed */
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{
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thread->unix_pid = -1;
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thread->unix_tid = -1;
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thread->attached = 0;
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}
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}
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return (ret != -1);
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}
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/* attach to a Unix process with ptrace */
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int attach_process( struct process *process )
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{
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struct thread *thread;
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int ret = 1;
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if (list_empty( &process->thread_list )) /* need at least one running thread */
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{
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set_error( STATUS_ACCESS_DENIED );
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return 0;
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}
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LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
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{
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if (thread->attached) continue;
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if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
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else ret = 0;
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}
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return ret;
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}
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/* detach from a ptraced Unix process */
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void detach_process( struct process *process )
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{
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struct thread *thread;
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LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
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{
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if (thread->attached)
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{
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/* make sure it is stopped */
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suspend_for_ptrace( thread );
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if (thread->unix_pid == -1) return;
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if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
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ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 );
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thread->attached = 0;
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}
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}
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}
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/* suspend a thread to allow using ptrace on it */
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/* you must do a resume_after_ptrace when finished with the thread */
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int suspend_for_ptrace( struct thread *thread )
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{
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/* can't stop a thread while initialisation is in progress */
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if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
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if (thread->attached)
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{
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if (!send_thread_signal( thread, SIGSTOP )) goto error;
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}
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else
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{
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/* this may fail if the client is already being debugged */
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if (!use_ptrace) goto error;
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if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
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{
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if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1; /* thread got killed */
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goto error;
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}
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if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
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thread->attached = 1;
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}
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if (wait4_thread( thread, SIGSTOP )) return 1;
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resume_after_ptrace( thread );
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error:
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set_error( STATUS_ACCESS_DENIED );
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return 0;
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}
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/* resume a thread after we have used ptrace on it */
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void resume_after_ptrace( struct thread *thread )
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{
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if (thread->unix_pid == -1) return;
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assert( thread->attached );
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ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
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get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
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}
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/* read an int from a thread address space */
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int read_thread_int( struct thread *thread, const int *addr, int *data )
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{
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errno = 0;
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*data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
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if ( *data == -1 && errno)
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{
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file_set_error();
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return -1;
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}
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return 0;
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}
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/* write an int to a thread address space */
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int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
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{
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int res;
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if (mask != ~0)
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{
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if (read_thread_int( thread, addr, &res ) == -1) return -1;
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data = (data & mask) | (res & ~mask);
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}
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if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
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file_set_error();
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return res;
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}
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