server/ptrace.c

   1 /*
   2  * Server-side ptrace support
   3  *
   4  * Copyright (C) 1999 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include "config.h"
  22
  23 #include <assert.h>
  24 #include <errno.h>
  25 #include <stdio.h>
  26 #include <signal.h>
  27 #include <sys/types.h>
  28 #ifdef HAVE_SYS_PTRACE_H
  29 # include <sys/ptrace.h>
  30 #endif
  31 #ifdef HAVE_SYS_WAIT_H
  32 # include <sys/wait.h>
  33 #endif
  34 #include <unistd.h>
  35
  36 #include "file.h"
  37 #include "process.h"
  38 #include "thread.h"
  39
  40 #ifndef PTRACE_CONT
  41 #define PTRACE_CONT PT_CONTINUE
  42 #endif
  43 #ifndef PTRACE_SINGLESTEP
  44 #define PTRACE_SINGLESTEP PT_STEP
  45 #endif
  46 #ifndef PTRACE_ATTACH
  47 #define PTRACE_ATTACH PT_ATTACH
  48 #endif
  49 #ifndef PTRACE_DETACH
  50 #define PTRACE_DETACH PT_DETACH
  51 #endif
  52 #ifndef PTRACE_PEEKDATA
  53 #define PTRACE_PEEKDATA PT_READ_D
  54 #endif
  55 #ifndef PTRACE_POKEDATA
  56 #define PTRACE_POKEDATA PT_WRITE_D
  57 #endif
  58
  59 #ifndef HAVE_SYS_PTRACE_H
  60 #define PT_CONTINUE 0
  61 #define PT_ATTACH   1
  62 #define PT_DETACH   2
  63 #define PT_READ_D   3
  64 #define PT_WRITE_D  4
  65 #define PT_STEP     5
  66 inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
  67 #endif  /* HAVE_SYS_PTRACE_H */
  68
  69 #ifndef __WALL
  70 #define __WALL 0
  71 #endif
  72
  73 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  74
  75 /* handle a status returned by wait4 */
  76 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  77 {
  78     if (WIFSTOPPED(status))
  79     {
  80         int sig = WSTOPSIG(status);
  81         if (debug_level && thread)
  82             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
  83         if (sig != want_sig)
  84         {
  85             /* ignore other signals for now */
  86             if (thread && get_thread_single_step( thread ))
  87                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  88             else
  89                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  90         }
  91         return sig;
  92     }
  93     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  94     {
  95         thread->attached = 0;
  96         thread->unix_pid = -1;
  97         thread->unix_tid = -1;
  98         if (debug_level)
  99         {
 100             if (WIFSIGNALED(status))
 101                 fprintf( stderr, "%04x: *exited* signal=%d\n",
 102                          thread->id, WTERMSIG(status) );
 103             else
 104                 fprintf( stderr, "%04x: *exited* status=%d\n",
 105                          thread->id, WEXITSTATUS(status) );
 106         }
 107     }
 108     return 0;
 109 }
 110
 111 /* handle a SIGCHLD signal */
 112 void sigchld_callback(void)
 113 {
 114     int pid, status;
 115
 116     for (;;)
 117     {
 118         if (!(pid = wait4( -1, &status, WUNTRACED | WNOHANG | __WALL, NULL ))) break;
 119         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 120         else break;
 121     }
 122 }
 123
 124 /* wait for a ptraced child to get a certain signal */
 125 static void wait4_thread( struct thread *thread, int signal )
 126 {
 127     int res, status;
 128
 129     do
 130     {
 131         if ((res = wait4( get_ptrace_pid(thread), &status, WUNTRACED | __WALL, NULL )) == -1)
 132         {
 133             if (errno == ECHILD)  /* must have died */
 134             {
 135                 thread->unix_pid = -1;
 136                 thread->unix_tid = -1;
 137                 thread->attached = 0;
 138             }
 139             else perror( "wait4" );
 140             return;
 141         }
 142         res = handle_child_status( thread, res, status, signal );
 143     } while (res && res != signal);
 144 }
 145
 146 /* return the Unix pid to use in ptrace calls for a given thread */
 147 int get_ptrace_pid( struct thread *thread )
 148 {
 149     if (thread->unix_tid != -1) return thread->unix_tid;
 150     return thread->unix_pid;
 151 }
 152
 153 /* send a Unix signal to a specific thread */
 154 int send_thread_signal( struct thread *thread, int sig )
 155 {
 156     int ret = -1;
 157
 158     if (thread->unix_pid != -1)
 159     {
 160         if (thread->unix_tid != -1)
 161         {
 162             ret = tkill( thread->unix_tid, sig );
 163             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 164         }
 165         else ret = kill( thread->unix_pid, sig );
 166
 167         if (ret == -1 && errno == ESRCH) /* thread got killed */
 168         {
 169             thread->unix_pid = -1;
 170             thread->unix_tid = -1;
 171             thread->attached = 0;
 172         }
 173     }
 174     return (ret != -1);
 175 }
 176
 177 /* attach to a Unix thread */
 178 static int attach_thread( struct thread *thread )
 179 {
 180     /* this may fail if the client is already being debugged */
 181     if (!use_ptrace) return 0;
 182     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 183     {
 184         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 185         return 0;
 186     }
 187     if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
 188     thread->attached = 1;
 189     wait4_thread( thread, SIGSTOP );
 190     return 1;
 191 }
 192
 193 /* detach from a Unix thread and kill it */
 194 void detach_thread( struct thread *thread, int sig )
 195 {
 196     if (thread->unix_pid == -1) return;
 197     if (thread->attached)
 198     {
 199         /* make sure it is stopped */
 200         suspend_for_ptrace( thread );
 201         if (sig) send_thread_signal( thread, sig );
 202         if (thread->unix_pid == -1) return;
 203         if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
 204         ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, sig );
 205         thread->attached = 0;
 206     }
 207     else if (sig) send_thread_signal( thread, sig );
 208 }
 209
 210 /* attach to a Unix process with ptrace */
 211 int attach_process( struct process *process )
 212 {
 213     struct thread *thread;
 214     int ret = 1;
 215
 216     if (!process->thread_list)  /* need at least one running thread */
 217     {
 218         set_error( STATUS_ACCESS_DENIED );
 219         return 0;
 220     }
 221     for (thread = process->thread_list; thread; thread = thread->proc_next)
 222     {
 223         if (thread->attached) continue;
 224         if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
 225         else ret = 0;
 226     }
 227     return ret;
 228 }
 229
 230 /* detach from a ptraced Unix process */
 231 void detach_process( struct process *process )
 232 {
 233     struct thread *thread;
 234
 235     for (thread = process->thread_list; thread; thread = thread->proc_next)
 236     {
 237         if (thread->attached) detach_thread( thread, 0 );
 238     }
 239 }
 240
 241 /* suspend a thread to allow using ptrace on it */
 242 /* you must do a resume_after_ptrace when finished with the thread */
 243 int suspend_for_ptrace( struct thread *thread )
 244 {
 245     /* can't stop a thread while initialisation is in progress */
 246     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 247
 248     if (thread->attached)
 249     {
 250         send_thread_signal( thread, SIGSTOP );
 251         wait4_thread( thread, SIGSTOP );
 252         return 1;
 253     }
 254     if (attach_thread( thread )) return 1;
 255  error:
 256     set_error( STATUS_ACCESS_DENIED );
 257     return 0;
 258 }
 259
 260 /* resume a thread after we have used ptrace on it */
 261 void resume_after_ptrace( struct thread *thread )
 262 {
 263     if (thread->unix_pid == -1) return;
 264     assert( thread->attached );
 265     ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 266             get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
 267 }
 268
 269 /* read an int from a thread address space */
 270 int read_thread_int( struct thread *thread, const int *addr, int *data )
 271 {
 272     errno = 0;
 273     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 274     if ( *data == -1 && errno)
 275     {
 276         file_set_error();
 277         return -1;
 278     }
 279     return 0;
 280 }
 281
 282 /* write an int to a thread address space */
 283 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 284 {
 285     int res;
 286     if (mask != ~0)
 287     {
 288         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 289         data = (data & mask) | (res & ~mask);
 290     }
 291     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 292         file_set_error();
 293     return res;
 294 }