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 <stdarg.h>
  28 #include <sys/types.h>
  29 #ifdef HAVE_SYS_PTRACE_H
  30 # include <sys/ptrace.h>
  31 #endif
  32 #ifdef HAVE_SYS_WAIT_H
  33 # include <sys/wait.h>
  34 #endif
  35 #include <unistd.h>
  36
  37 #include "ntstatus.h"
  38 #define WIN32_NO_STATUS
  39 #include "winternl.h"
  40
  41 #include "file.h"
  42 #include "process.h"
  43 #include "thread.h"
  44
  45 #ifndef PTRACE_CONT
  46 #define PTRACE_CONT PT_CONTINUE
  47 #endif
  48 #ifndef PTRACE_SINGLESTEP
  49 #define PTRACE_SINGLESTEP PT_STEP
  50 #endif
  51 #ifndef PTRACE_ATTACH
  52 #define PTRACE_ATTACH PT_ATTACH
  53 #endif
  54 #ifndef PTRACE_DETACH
  55 #define PTRACE_DETACH PT_DETACH
  56 #endif
  57 #ifndef PTRACE_PEEKDATA
  58 #define PTRACE_PEEKDATA PT_READ_D
  59 #endif
  60 #ifndef PTRACE_POKEDATA
  61 #define PTRACE_POKEDATA PT_WRITE_D
  62 #endif
  63
  64 #ifndef HAVE_SYS_PTRACE_H
  65 #define PT_CONTINUE 0
  66 #define PT_ATTACH   1
  67 #define PT_DETACH   2
  68 #define PT_READ_D   3
  69 #define PT_WRITE_D  4
  70 #define PT_STEP     5
  71 inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
  72 #endif  /* HAVE_SYS_PTRACE_H */
  73
  74 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  75
  76 /* handle a status returned by wait4 */
  77 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  78 {
  79     if (WIFSTOPPED(status))
  80     {
  81         int sig = WSTOPSIG(status);
  82         if (debug_level && thread)
  83             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
  84         if (sig != want_sig)
  85         {
  86             /* ignore other signals for now */
  87             if (thread && get_thread_single_step( thread ))
  88                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  89             else
  90                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  91         }
  92         return sig;
  93     }
  94     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  95     {
  96         thread->attached = 0;
  97         thread->unix_pid = -1;
  98         thread->unix_tid = -1;
  99         if (debug_level)
 100         {
 101             if (WIFSIGNALED(status))
 102                 fprintf( stderr, "%04x: *exited* signal=%d\n",
 103                          thread->id, WTERMSIG(status) );
 104             else
 105                 fprintf( stderr, "%04x: *exited* status=%d\n",
 106                          thread->id, WEXITSTATUS(status) );
 107         }
 108     }
 109     return 0;
 110 }
 111
 112 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 113 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 114 {
 115 #ifdef __WALL
 116     static int wall_flag = __WALL;
 117
 118     for (;;)
 119     {
 120         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 121         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 122         wall_flag = 0;
 123     }
 124 #else
 125     return wait4( pid, status, options, usage );
 126 #endif
 127 }
 128
 129 /* handle a SIGCHLD signal */
 130 void sigchld_callback(void)
 131 {
 132     int pid, status;
 133
 134     for (;;)
 135     {
 136         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 137         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 138         else break;
 139     }
 140 }
 141
 142 /* wait for a ptraced child to get a certain signal */
 143 static int wait4_thread( struct thread *thread, int signal )
 144 {
 145     int res, status;
 146
 147     start_watchdog();
 148     for (;;)
 149     {
 150         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 151         {
 152             if (errno == EINTR)
 153             {
 154                 if (!watchdog_triggered()) continue;
 155                 if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
 156             }
 157             else if (errno == ECHILD)  /* must have died */
 158             {
 159                 thread->unix_pid = -1;
 160                 thread->unix_tid = -1;
 161                 thread->attached = 0;
 162             }
 163             else perror( "wait4" );
 164             stop_watchdog();
 165             return 0;
 166         }
 167         res = handle_child_status( thread, res, status, signal );
 168         if (!res || res == signal) break;
 169     }
 170     stop_watchdog();
 171     return (thread->unix_pid != -1);
 172 }
 173
 174 /* return the Unix pid to use in ptrace calls for a given thread */
 175 int get_ptrace_pid( struct thread *thread )
 176 {
 177     if (thread->unix_tid != -1) return thread->unix_tid;
 178     return thread->unix_pid;
 179 }
 180
 181 /* send a Unix signal to a specific thread */
 182 int send_thread_signal( struct thread *thread, int sig )
 183 {
 184     int ret = -1;
 185
 186     if (thread->unix_pid != -1)
 187     {
 188         if (thread->unix_tid != -1)
 189         {
 190             ret = tkill( thread->unix_pid, thread->unix_tid, sig );
 191             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 192         }
 193         else ret = kill( thread->unix_pid, sig );
 194
 195         if (ret == -1 && errno == ESRCH) /* thread got killed */
 196         {
 197             thread->unix_pid = -1;
 198             thread->unix_tid = -1;
 199             thread->attached = 0;
 200         }
 201     }
 202     return (ret != -1);
 203 }
 204
 205 /* attach to a Unix process with ptrace */
 206 int attach_process( struct process *process )
 207 {
 208     struct thread *thread;
 209     int ret = 1;
 210
 211     if (list_empty( &process->thread_list ))  /* need at least one running thread */
 212     {
 213         set_error( STATUS_ACCESS_DENIED );
 214         return 0;
 215     }
 216
 217     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 218     {
 219         if (thread->attached) continue;
 220         if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
 221         else ret = 0;
 222     }
 223     return ret;
 224 }
 225
 226 /* detach from a ptraced Unix process */
 227 void detach_process( struct process *process )
 228 {
 229     struct thread *thread;
 230
 231     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 232     {
 233         if (thread->attached)
 234         {
 235             /* make sure it is stopped */
 236             suspend_for_ptrace( thread );
 237             if (thread->unix_pid == -1) return;
 238             if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
 239             ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 );
 240             thread->attached = 0;
 241         }
 242     }
 243 }
 244
 245 /* suspend a thread to allow using ptrace on it */
 246 /* you must do a resume_after_ptrace when finished with the thread */
 247 int suspend_for_ptrace( struct thread *thread )
 248 {
 249     /* can't stop a thread while initialisation is in progress */
 250     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 251
 252     if (thread->attached)
 253     {
 254         if (!send_thread_signal( thread, SIGSTOP )) goto error;
 255     }
 256     else
 257     {
 258         /* this may fail if the client is already being debugged */
 259         if (!use_ptrace) goto error;
 260         if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 261         {
 262             if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 263             goto error;
 264         }
 265         if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
 266         thread->attached = 1;
 267     }
 268     if (wait4_thread( thread, SIGSTOP )) return 1;
 269     resume_after_ptrace( thread );
 270  error:
 271     set_error( STATUS_ACCESS_DENIED );
 272     return 0;
 273 }
 274
 275 /* resume a thread after we have used ptrace on it */
 276 void resume_after_ptrace( struct thread *thread )
 277 {
 278     if (thread->unix_pid == -1) return;
 279     assert( thread->attached );
 280     ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 281             get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
 282 }
 283
 284 /* read an int from a thread address space */
 285 int read_thread_int( struct thread *thread, const int *addr, int *data )
 286 {
 287     errno = 0;
 288     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 289     if ( *data == -1 && errno)
 290     {
 291         file_set_error();
 292         return -1;
 293     }
 294     return 0;
 295 }
 296
 297 /* write an int to a thread address space */
 298 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 299 {
 300     int res;
 301     if (mask != ~0)
 302     {
 303         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 304         data = (data & mask) | (res & ~mask);
 305     }
 306     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 307         file_set_error();
 308     return res;
 309 }