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     for (;;)
 143     {
 144         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 145         {
 146             if (errno == EINTR) continue;
 147             if (errno == ECHILD)  /* must have died */
 148             {
 149                 thread->unix_pid = -1;
 150                 thread->unix_tid = -1;
 151                 thread->attached = 0;
 152             }
 153             else perror( "wait4" );
 154             return 0;
 155         }
 156         res = handle_child_status( thread, res, status, signal );
 157         if (!res || res == signal) break;
 158     }
 159     return (thread->unix_pid != -1);
 160 }
 161
 162 /* return the Unix pid to use in ptrace calls for a given thread */
 163 int get_ptrace_pid( struct thread *thread )
 164 {
 165     if (thread->unix_tid != -1) return thread->unix_tid;
 166     return thread->unix_pid;
 167 }
 168
 169 /* send a Unix signal to a specific thread */
 170 int send_thread_signal( struct thread *thread, int sig )
 171 {
 172     int ret = -1;
 173
 174     if (thread->unix_pid != -1)
 175     {
 176         if (thread->unix_tid != -1)
 177         {
 178             ret = tkill( thread->unix_tid, sig );
 179             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 180         }
 181         else ret = kill( thread->unix_pid, sig );
 182
 183         if (ret == -1 && errno == ESRCH) /* thread got killed */
 184         {
 185             thread->unix_pid = -1;
 186             thread->unix_tid = -1;
 187             thread->attached = 0;
 188         }
 189     }
 190     return (ret != -1);
 191 }
 192
 193 /* attach to a Unix thread */
 194 static int attach_thread( struct thread *thread )
 195 {
 196     /* this may fail if the client is already being debugged */
 197     if (!use_ptrace) return 0;
 198     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 199     {
 200         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 201         return 0;
 202     }
 203     if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
 204     thread->attached = 1;
 205     return wait4_thread( thread, SIGSTOP );
 206 }
 207
 208 /* detach from a Unix thread and kill it */
 209 void detach_thread( struct thread *thread, int sig )
 210 {
 211     if (thread->unix_pid == -1) return;
 212     if (thread->attached)
 213     {
 214         /* make sure it is stopped */
 215         suspend_for_ptrace( thread );
 216         if (sig) send_thread_signal( thread, sig );
 217         if (thread->unix_pid == -1) return;
 218         if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
 219         ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, sig );
 220         thread->attached = 0;
 221     }
 222     else if (sig) send_thread_signal( thread, sig );
 223 }
 224
 225 /* attach to a Unix process with ptrace */
 226 int attach_process( struct process *process )
 227 {
 228     struct thread *thread;
 229     int ret = 1;
 230
 231     if (list_empty( &process->thread_list ))  /* need at least one running thread */
 232     {
 233         set_error( STATUS_ACCESS_DENIED );
 234         return 0;
 235     }
 236
 237     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 238     {
 239         if (thread->attached) continue;
 240         if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
 241         else ret = 0;
 242     }
 243     return ret;
 244 }
 245
 246 /* detach from a ptraced Unix process */
 247 void detach_process( struct process *process )
 248 {
 249     struct thread *thread;
 250
 251     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 252     {
 253         if (thread->attached) detach_thread( thread, 0 );
 254     }
 255 }
 256
 257 /* suspend a thread to allow using ptrace on it */
 258 /* you must do a resume_after_ptrace when finished with the thread */
 259 int suspend_for_ptrace( struct thread *thread )
 260 {
 261     /* can't stop a thread while initialisation is in progress */
 262     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 263
 264     if (thread->attached)
 265     {
 266         if (!send_thread_signal( thread, SIGSTOP )) goto error;
 267         if (!wait4_thread( thread, SIGSTOP )) goto error;
 268         return 1;
 269     }
 270     if (attach_thread( thread )) return 1;
 271  error:
 272     set_error( STATUS_ACCESS_DENIED );
 273     return 0;
 274 }
 275
 276 /* resume a thread after we have used ptrace on it */
 277 void resume_after_ptrace( struct thread *thread )
 278 {
 279     if (thread->unix_pid == -1) return;
 280     assert( thread->attached );
 281     ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 282             get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
 283 }
 284
 285 /* read an int from a thread address space */
 286 int read_thread_int( struct thread *thread, const int *addr, int *data )
 287 {
 288     errno = 0;
 289     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 290     if ( *data == -1 && errno)
 291     {
 292         file_set_error();
 293         return -1;
 294     }
 295     return 0;
 296 }
 297
 298 /* write an int to a thread address space */
 299 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 300 {
 301     int res;
 302     if (mask != ~0)
 303     {
 304         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 305         data = (data & mask) | (res & ~mask);
 306     }
 307     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 308         file_set_error();
 309     return res;
 310 }