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 "process.h"
  37 #include "thread.h"
  38
  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 )
  73 {
  74     if (WIFSTOPPED(status))
  75     {
  76         int sig = WSTOPSIG(status);
  77         if (debug_level && thread)
  78             fprintf( stderr, "%08x: *signal* signal=%d\n", (unsigned int)thread, sig );
  79         switch(sig)
  80         {
  81         case SIGSTOP:  /* continue at once if not suspended */
  82             if (thread && (thread->process->suspend + thread->suspend)) break;
  83             /* fall through */
  84         default:  /* ignore other signals for now */
  85             if (thread && get_thread_single_step( thread ))
  86                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  87             else
  88                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  89             break;
  90         }
  91         return sig;
  92     }
  93     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  94     {
  95         thread->attached = 0;
  96         thread->unix_pid = 0;
  97         if (debug_level)
  98         {
  99             if (WIFSIGNALED(status))
 100                 fprintf( stderr, "%08x: *exited* signal=%d\n",
 101                          (unsigned int)thread, WTERMSIG(status) );
 102             else
 103                 fprintf( stderr, "%08x: *exited* status=%d\n",
 104                          (unsigned int)thread, WEXITSTATUS(status) );
 105         }
 106     }
 107     return 0;
 108 }
 109
 110 /* handle a SIGCHLD signal */
 111 void sigchld_handler()
 112 {
 113     int pid, status;
 114
 115     for (;;)
 116     {
 117         if (!(pid = wait4( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 118         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status );
 119         else break;
 120     }
 121 }
 122
 123 /* wait for a ptraced child to get a certain signal */
 124 void wait4_thread( struct thread *thread, int signal )
 125 {
 126     int res, status;
 127
 128     do
 129     {
 130         if ((res = wait4( thread->unix_pid, &status, WUNTRACED, NULL )) == -1)
 131         {
 132             perror( "wait4" );
 133             return;
 134         }
 135         res = handle_child_status( thread, res, status );
 136     } while (res && res != signal);
 137 }
 138
 139 /* attach to a Unix thread */
 140 static int attach_thread( struct thread *thread )
 141 {
 142     /* this may fail if the client is already being debugged */
 143     if (!use_ptrace) return 0;
 144     if (ptrace( PTRACE_ATTACH, thread->unix_pid, 0, 0 ) == -1)
 145     {
 146         if (errno == ESRCH) thread->unix_pid = 0;  /* process got killed */
 147         return 0;
 148     }
 149     if (debug_level) fprintf( stderr, "%08x: *attached*\n", (unsigned int)thread );
 150     thread->attached = 1;
 151     wait4_thread( thread, SIGSTOP );
 152     return 1;
 153 }
 154
 155 /* detach from a Unix thread and kill it */
 156 void detach_thread( struct thread *thread, int sig )
 157 {
 158     if (!thread->unix_pid) return;
 159     if (thread->attached)
 160     {
 161         /* make sure it is stopped */
 162         suspend_thread( thread, 0 );
 163         if (sig) kill( thread->unix_pid, sig );
 164         if (debug_level) fprintf( stderr, "%08x: *detached*\n", (unsigned int)thread );
 165         ptrace( PTRACE_DETACH, thread->unix_pid, (caddr_t)1, sig );
 166         thread->suspend = 0;  /* detach makes it continue */
 167         thread->attached = 0;
 168     }
 169     else
 170     {
 171         if (sig) kill( thread->unix_pid, sig );
 172         if (thread->suspend + thread->process->suspend) continue_thread( thread );
 173     }
 174 }
 175
 176 /* stop a thread (at the Unix level) */
 177 void stop_thread( struct thread *thread )
 178 {
 179     /* can't stop a thread while initialisation is in progress */
 180     if (!thread->unix_pid || !is_process_init_done(thread->process)) return;
 181     /* first try to attach to it */
 182     if (!thread->attached)
 183         if (attach_thread( thread )) return;  /* this will have stopped it */
 184     /* attached already, or attach failed -> send a signal */
 185     if (!thread->unix_pid) return;
 186     kill( thread->unix_pid, SIGSTOP );
 187     if (thread->attached) wait4_thread( thread, SIGSTOP );
 188 }
 189
 190 /* make a thread continue (at the Unix level) */
 191 void continue_thread( struct thread *thread )
 192 {
 193     if (!thread->unix_pid) return;
 194     if (!thread->attached) kill( thread->unix_pid, SIGCONT );
 195     else ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 196                  thread->unix_pid, (caddr_t)1, SIGSTOP );
 197 }
 198
 199 /* suspend a thread to allow using ptrace on it */
 200 /* you must do a resume_thread when finished with the thread */
 201 int suspend_for_ptrace( struct thread *thread )
 202 {
 203     if (thread->attached)
 204     {
 205         suspend_thread( thread, 0 );
 206         return 1;
 207     }
 208     /* can't stop a thread while initialisation is in progress */
 209     if (!thread->unix_pid || !is_process_init_done(thread->process)) goto error;
 210     thread->suspend++;
 211     if (attach_thread( thread )) return 1;
 212     thread->suspend--;
 213  error:
 214     set_error( STATUS_ACCESS_DENIED );
 215     return 0;
 216 }
 217
 218 /* read an int from a thread address space */
 219 int read_thread_int( struct thread *thread, const int *addr, int *data )
 220 {
 221     *data = ptrace( PTRACE_PEEKDATA, thread->unix_pid, (caddr_t)addr, 0 );
 222     if ( *data == -1 && errno)
 223     {
 224         file_set_error();
 225         return -1;
 226     }
 227     return 0;
 228 }
 229
 230 /* write an int to a thread address space */
 231 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 232 {
 233     int res;
 234     if (mask != ~0)
 235     {
 236         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 237         data = (data & mask) | (res & ~mask);
 238     }
 239     if ((res = ptrace( PTRACE_POKEDATA, thread->unix_pid, (caddr_t)addr, data )) == -1)
 240         file_set_error();
 241     return res;
 242 }