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Sweden-Number/server/ptrace.c

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/*
* Server-side ptrace support
*
* Copyright (C) 1999 Alexandre Julliard
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "config.h"
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#ifdef HAVE_SYS_PTRACE_H
# include <sys/ptrace.h>
#endif
#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif
#include <unistd.h>
#include "file.h"
#include "process.h"
#include "thread.h"
#ifndef PTRACE_CONT
#define PTRACE_CONT PT_CONTINUE
#endif
#ifndef PTRACE_SINGLESTEP
#define PTRACE_SINGLESTEP PT_STEP
#endif
#ifndef PTRACE_ATTACH
#define PTRACE_ATTACH PT_ATTACH
#endif
#ifndef PTRACE_DETACH
#define PTRACE_DETACH PT_DETACH
#endif
#ifndef PTRACE_PEEKDATA
#define PTRACE_PEEKDATA PT_READ_D
#endif
#ifndef PTRACE_POKEDATA
#define PTRACE_POKEDATA PT_WRITE_D
#endif
#ifndef HAVE_SYS_PTRACE_H
#define PT_CONTINUE 0
#define PT_ATTACH 1
#define PT_DETACH 2
#define PT_READ_D 3
#define PT_WRITE_D 4
#define PT_STEP 5
inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
#endif /* HAVE_SYS_PTRACE_H */
static const int use_ptrace = 1; /* set to 0 to disable ptrace */
/* handle a status returned by wait4 */
static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
{
if (WIFSTOPPED(status))
{
int sig = WSTOPSIG(status);
if (debug_level && thread)
fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
if (sig != want_sig)
{
/* ignore other signals for now */
if (thread && get_thread_single_step( thread ))
ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
else
ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
}
return sig;
}
if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
{
thread->attached = 0;
thread->unix_pid = -1;
thread->unix_tid = -1;
if (debug_level)
{
if (WIFSIGNALED(status))
fprintf( stderr, "%04x: *exited* signal=%d\n",
thread->id, WTERMSIG(status) );
else
fprintf( stderr, "%04x: *exited* status=%d\n",
thread->id, WEXITSTATUS(status) );
}
}
return 0;
}
/* wait4 wrapper to handle missing __WALL flag in older kernels */
static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
{
#ifdef __WALL
static int wall_flag = __WALL;
for (;;)
{
pid_t ret = wait4( pid, status, options | wall_flag, usage );
if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
wall_flag = 0;
}
#else
return wait4( pid, status, options, usage );
#endif
}
/* handle a SIGCHLD signal */
void sigchld_callback(void)
{
int pid, status;
for (;;)
{
if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
else break;
}
}
/* wait for a ptraced child to get a certain signal */
static int wait4_thread( struct thread *thread, int signal )
{
int res, status;
for (;;)
{
if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
{
if (errno == EINTR) continue;
if (errno == ECHILD) /* must have died */
{
thread->unix_pid = -1;
thread->unix_tid = -1;
thread->attached = 0;
}
else perror( "wait4" );
return 0;
}
res = handle_child_status( thread, res, status, signal );
if (!res || res == signal) break;
}
return (thread->unix_pid != -1);
}
/* return the Unix pid to use in ptrace calls for a given thread */
int get_ptrace_pid( struct thread *thread )
{
if (thread->unix_tid != -1) return thread->unix_tid;
return thread->unix_pid;
}
/* send a Unix signal to a specific thread */
int send_thread_signal( struct thread *thread, int sig )
{
int ret = -1;
if (thread->unix_pid != -1)
{
if (thread->unix_tid != -1)
{
ret = tkill( thread->unix_tid, sig );
if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
}
else ret = kill( thread->unix_pid, sig );
if (ret == -1 && errno == ESRCH) /* thread got killed */
{
thread->unix_pid = -1;
thread->unix_tid = -1;
thread->attached = 0;
}
}
return (ret != -1);
}
/* attach to a Unix thread */
static int attach_thread( struct thread *thread )
{
/* this may fail if the client is already being debugged */
if (!use_ptrace) return 0;
if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
{
if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1; /* thread got killed */
return 0;
}
if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
thread->attached = 1;
return wait4_thread( thread, SIGSTOP );
}
/* detach from a Unix thread and kill it */
void detach_thread( struct thread *thread, int sig )
{
if (thread->unix_pid == -1) return;
if (thread->attached)
{
/* make sure it is stopped */
suspend_for_ptrace( thread );
if (sig) send_thread_signal( thread, sig );
if (thread->unix_pid == -1) return;
if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, sig );
thread->attached = 0;
}
else if (sig) send_thread_signal( thread, sig );
}
/* attach to a Unix process with ptrace */
int attach_process( struct process *process )
{
struct thread *thread;
int ret = 1;
if (!process->thread_list) /* need at least one running thread */
{
set_error( STATUS_ACCESS_DENIED );
return 0;
}
for (thread = process->thread_list; thread; thread = thread->proc_next)
{
if (thread->attached) continue;
if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
else ret = 0;
}
return ret;
}
/* detach from a ptraced Unix process */
void detach_process( struct process *process )
{
struct thread *thread;
for (thread = process->thread_list; thread; thread = thread->proc_next)
{
if (thread->attached) detach_thread( thread, 0 );
}
}
/* suspend a thread to allow using ptrace on it */
/* you must do a resume_after_ptrace when finished with the thread */
int suspend_for_ptrace( struct thread *thread )
{
/* can't stop a thread while initialisation is in progress */
if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
if (thread->attached)
{
if (!send_thread_signal( thread, SIGSTOP )) goto error;
if (!wait4_thread( thread, SIGSTOP )) goto error;
return 1;
}
if (attach_thread( thread )) return 1;
error:
set_error( STATUS_ACCESS_DENIED );
return 0;
}
/* resume a thread after we have used ptrace on it */
void resume_after_ptrace( struct thread *thread )
{
if (thread->unix_pid == -1) return;
assert( thread->attached );
ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
}
/* read an int from a thread address space */
int read_thread_int( struct thread *thread, const int *addr, int *data )
{
errno = 0;
*data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
if ( *data == -1 && errno)
{
file_set_error();
return -1;
}
return 0;
}
/* write an int to a thread address space */
int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
{
int res;
if (mask != ~0)
{
if (read_thread_int( thread, addr, &res ) == -1) return -1;
data = (data & mask) | (res & ~mask);
}
if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
file_set_error();
return res;
}
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