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 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  70
  71 /* handle a status returned by wait4 */
  72 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  73 {
  74     if (WIFSTOPPED(status))
  75     {
  76         int sig = WSTOPSIG(status);
  77         if (debug_level && thread)
  78             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
  79         if (sig != want_sig)
  80         {
  81             /* ignore other signals for now */
  82             if (thread && get_thread_single_step( thread ))
  83                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  84             else
  85                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  86         }
  87         return sig;
  88     }
  89     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  90     {
  91         thread->attached = 0;
  92         thread->unix_pid = -1;
  93         thread->unix_tid = -1;
  94         if (debug_level)
  95         {
  96             if (WIFSIGNALED(status))
  97                 fprintf( stderr, "%04x: *exited* signal=%d\n",
  98                          thread->id, WTERMSIG(status) );
  99             else
 100                 fprintf( stderr, "%04x: *exited* status=%d\n",
 101                          thread->id, WEXITSTATUS(status) );
 102         }
 103     }
 104     return 0;
 105 }
 106
 107 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 108 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 109 {
 110 #ifdef __WALL
 111     static int wall_flag = __WALL;
 112
 113     for (;;)
 114     {
 115         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 116         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 117         wall_flag = 0;
 118     }
 119 #else
 120     return wait4( pid, status, options, usage );
 121 #endif
 122 }
 123
 124 /* handle a SIGCHLD signal */
 125 void sigchld_callback(void)
 126 {
 127     int pid, status;
 128
 129     for (;;)
 130     {
 131         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 132         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 133         else break;
 134     }
 135 }
 136
 137 /* wait for a ptraced child to get a certain signal */
 138 static int wait4_thread( struct thread *thread, int signal )
 139 {
 140     int res, status;
 141
 142     do
 143     {
 144         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 145         {
 146             if (errno == ECHILD)  /* must have died */
 147             {
 148                 thread->unix_pid = -1;
 149                 thread->unix_tid = -1;
 150                 thread->attached = 0;
 151             }
 152             else perror( "wait4" );
 153             return 0;
 154         }
 155         res = handle_child_status( thread, res, status, signal );
 156     } while (res && res != signal);
 157     return (thread->unix_pid != -1);
 158 }
 159
 160 /* return the Unix pid to use in ptrace calls for a given thread */
 161 int get_ptrace_pid( struct thread *thread )
 162 {
 163     if (thread->unix_tid != -1) return thread->unix_tid;
 164     return thread->unix_pid;
 165 }
 166
 167 /* send a Unix signal to a specific thread */
 168 int send_thread_signal( struct thread *thread, int sig )
 169 {
 170     int ret = -1;
 171
 172     if (thread->unix_pid != -1)
 173     {
 174         if (thread->unix_tid != -1)
 175         {
 176             ret = tkill( thread->unix_tid, sig );
 177             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 178         }
 179         else ret = kill( thread->unix_pid, sig );
 180
 181         if (ret == -1 && errno == ESRCH) /* thread got killed */
 182         {
 183             thread->unix_pid = -1;
 184             thread->unix_tid = -1;
 185             thread->attached = 0;
 186         }
 187     }
 188     return (ret != -1);
 189 }
 190
 191 /* attach to a Unix thread */
 192 static int attach_thread( struct thread *thread )
 193 {
 194     /* this may fail if the client is already being debugged */
 195     if (!use_ptrace) return 0;
 196     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 197     {
 198         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 199         return 0;
 200     }
 201     if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
 202     thread->attached = 1;
 203     return wait4_thread( thread, SIGSTOP );
 204 }
 205
 206 /* detach from a Unix thread and kill it */
 207 void detach_thread( struct thread *thread, int sig )
 208 {
 209     if (thread->unix_pid == -1) return;
 210     if (thread->attached)
 211     {
 212         /* make sure it is stopped */
 213         suspend_for_ptrace( thread );
 214         if (sig) send_thread_signal( thread, sig );
 215         if (thread->unix_pid == -1) return;
 216         if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
 217         ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, sig );
 218         thread->attached = 0;
 219     }
 220     else if (sig) send_thread_signal( thread, sig );
 221 }
 222
 223 /* attach to a Unix process with ptrace */
 224 int attach_process( struct process *process )
 225 {
 226     struct thread *thread;
 227     int ret = 1;
 228
 229     if (!process->thread_list)  /* need at least one running thread */
 230     {
 231         set_error( STATUS_ACCESS_DENIED );
 232         return 0;
 233     }
 234     for (thread = process->thread_list; thread; thread = thread->proc_next)
 235     {
 236         if (thread->attached) continue;
 237         if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
 238         else ret = 0;
 239     }
 240     return ret;
 241 }
 242
 243 /* detach from a ptraced Unix process */
 244 void detach_process( struct process *process )
 245 {
 246     struct thread *thread;
 247
 248     for (thread = process->thread_list; thread; thread = thread->proc_next)
 249     {
 250         if (thread->attached) detach_thread( thread, 0 );
 251     }
 252 }
 253
 254 /* suspend a thread to allow using ptrace on it */
 255 /* you must do a resume_after_ptrace when finished with the thread */
 256 int suspend_for_ptrace( struct thread *thread )
 257 {
 258     /* can't stop a thread while initialisation is in progress */
 259     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 260
 261     if (thread->attached)
 262     {
 263         if (!send_thread_signal( thread, SIGSTOP )) goto error;
 264         if (!wait4_thread( thread, SIGSTOP )) goto error;
 265         return 1;
 266     }
 267     if (attach_thread( thread )) return 1;
 268  error:
 269     set_error( STATUS_ACCESS_DENIED );
 270     return 0;
 271 }
 272
 273 /* resume a thread after we have used ptrace on it */
 274 void resume_after_ptrace( struct thread *thread )
 275 {
 276     if (thread->unix_pid == -1) return;
 277     assert( thread->attached );
 278     ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 279             get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
 280 }
 281
 282 /* read an int from a thread address space */
 283 int read_thread_int( struct thread *thread, const int *addr, int *data )
 284 {
 285     errno = 0;
 286     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 287     if ( *data == -1 && errno)
 288     {
 289         file_set_error();
 290         return -1;
 291     }
 292     return 0;
 293 }
 294
 295 /* write an int to a thread address space */
 296 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 297 {
 298     int res;
 299     if (mask != ~0)
 300     {
 301         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 302         data = (data & mask) | (res & ~mask);
 303     }
 304     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 305         file_set_error();
 306     return res;
 307 }