server/ptrace.c

   1 /*
   2  * Server-side ptrace support
   3  *
   4  * Copyright (C) 1999 Alexandre Julliard
   5  */
   6
   7 #include "config.h"
   8
   9 #include <assert.h>
  10 #include <errno.h>
  11 #include <stdio.h>
  12 #include <signal.h>
  13 #include <sys/types.h>
  14 #ifdef HAVE_SYS_PTRACE_H
  15 # include <sys/ptrace.h>
  16 #endif
  17 #ifdef HAVE_SYS_WAIT_H
  18 # include <sys/wait.h>
  19 #endif
  20 #include <unistd.h>
  21
  22 #include "process.h"
  23 #include "thread.h"
  24
  25
  26 #ifndef PTRACE_CONT
  27 #define PTRACE_CONT PT_CONTINUE
  28 #endif
  29 #ifndef PTRACE_SINGLESTEP
  30 #define PTRACE_SINGLESTEP PT_STEP
  31 #endif
  32 #ifndef PTRACE_ATTACH
  33 #define PTRACE_ATTACH PT_ATTACH
  34 #endif
  35 #ifndef PTRACE_DETACH
  36 #define PTRACE_DETACH PT_DETACH
  37 #endif
  38 #ifndef PTRACE_PEEKDATA
  39 #define PTRACE_PEEKDATA PT_READ_D
  40 #endif
  41 #ifndef PTRACE_POKEDATA
  42 #define PTRACE_POKEDATA PT_WRITE_D
  43 #endif
  44
  45 #ifdef HAVE_SYS_PTRACE_H
  46 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  47 #else
  48 static const int use_ptrace = 0;
  49
  50 #define PT_CONTINUE 0
  51 #define PT_ATTACH   1
  52 #define PT_DETACH   2
  53 #define PT_READ_D   3
  54 #define PT_WRITE_D  4
  55 #define PT_STEP     5
  56
  57 static int ptrace(int req, ...) { return -1; /*FAIL*/ }
  58 #endif
  59
  60 /* handle a status returned by wait4 */
  61 static int handle_child_status( struct thread *thread, int pid, int status )
  62 {
  63     if (WIFSTOPPED(status))
  64     {
  65         int sig = WSTOPSIG(status);
  66         if (debug_level && thread)
  67             fprintf( stderr, "%08x: *signal* signal=%d\n", (unsigned int)thread, sig );
  68         switch(sig)
  69         {
  70         case SIGSTOP:  /* continue at once if not suspended */
  71             if (thread && (thread->process->suspend + thread->suspend)) break;
  72             /* fall through */
  73         default:  /* ignore other signals for now */
  74             if (thread && get_thread_single_step( thread ))
  75                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  76             else
  77                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  78             break;
  79         }
  80         return sig;
  81     }
  82     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  83     {
  84         thread->attached = 0;
  85         thread->unix_pid = 0;
  86         if (debug_level)
  87         {
  88             if (WIFSIGNALED(status))
  89                 fprintf( stderr, "%08x: *exited* signal=%d\n",
  90                          (unsigned int)thread, WTERMSIG(status) );
  91             else
  92                 fprintf( stderr, "%08x: *exited* status=%d\n",
  93                          (unsigned int)thread, WEXITSTATUS(status) );
  94         }
  95     }
  96     return 0;
  97 }
  98
  99 /* handle a SIGCHLD signal */
 100 void sigchld_handler()
 101 {
 102     int pid, status;
 103
 104     for (;;)
 105     {
 106         if (!(pid = wait4( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 107         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status );
 108         else break;
 109     }
 110 }
 111
 112 /* wait for a ptraced child to get a certain signal */
 113 void wait4_thread( struct thread *thread, int signal )
 114 {
 115     int res, status;
 116
 117     do
 118     {
 119         if ((res = wait4( thread->unix_pid, &status, WUNTRACED, NULL )) == -1)
 120         {
 121             perror( "wait4" );
 122             return;
 123         }
 124         res = handle_child_status( thread, res, status );
 125     } while (res && res != signal);
 126 }
 127
 128 /* attach to a Unix thread */
 129 static int attach_thread( struct thread *thread )
 130 {
 131     /* this may fail if the client is already being debugged */
 132     if (!use_ptrace || (ptrace( PTRACE_ATTACH, thread->unix_pid, 0, 0 ) == -1)) return 0;
 133     if (debug_level) fprintf( stderr, "%08x: *attached*\n", (unsigned int)thread );
 134     thread->attached = 1;
 135     wait4_thread( thread, SIGSTOP );
 136     return 1;
 137 }
 138
 139 /* detach from a Unix thread and kill it */
 140 void detach_thread( struct thread *thread, int sig )
 141 {
 142     if (!thread->unix_pid) return;
 143     if (thread->attached)
 144     {
 145         /* make sure it is stopped */
 146         if (!(thread->suspend + thread->process->suspend)) stop_thread( thread );
 147         if (sig) kill( thread->unix_pid, sig );
 148         if (debug_level) fprintf( stderr, "%08x: *detached*\n", (unsigned int)thread );
 149         ptrace( PTRACE_DETACH, thread->unix_pid, (caddr_t)1, sig );
 150         thread->attached = 0;
 151     }
 152     else
 153     {
 154         if (sig) kill( thread->unix_pid, sig );
 155         if (thread->suspend + thread->process->suspend) continue_thread( thread );
 156     }
 157 }
 158
 159 /* stop a thread (at the Unix level) */
 160 void stop_thread( struct thread *thread )
 161 {
 162     /* can't stop a thread while initialisation is in progress */
 163     if (!thread->unix_pid || thread->process->init_event) return;
 164     /* first try to attach to it */
 165     if (!thread->attached)
 166         if (attach_thread( thread )) return;  /* this will have stopped it */
 167     /* attached already, or attach failed -> send a signal */
 168     kill( thread->unix_pid, SIGSTOP );
 169     if (thread->attached) wait4_thread( thread, SIGSTOP );
 170 }
 171
 172 /* make a thread continue (at the Unix level) */
 173 void continue_thread( struct thread *thread )
 174 {
 175     if (!thread->unix_pid) return;
 176     if (!thread->attached) kill( thread->unix_pid, SIGCONT );
 177     else ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 178                  thread->unix_pid, (caddr_t)1, SIGSTOP );
 179 }
 180
 181 /* suspend a thread to allow using ptrace on it */
 182 /* you must do a resume_thread when finished with the thread */
 183 int suspend_for_ptrace( struct thread *thread )
 184 {
 185     if (thread->attached)
 186     {
 187         suspend_thread( thread, 0 );
 188         return 1;
 189     }
 190     /* can't stop a thread while initialisation is in progress */
 191     if (!thread->unix_pid || thread->process->init_event) goto error;
 192     thread->suspend++;
 193     if (attach_thread( thread )) return 1;
 194     thread->suspend--;
 195  error:
 196     set_error( STATUS_ACCESS_DENIED );
 197     return 0;
 198 }
 199
 200 /* read an int from a thread address space */
 201 int read_thread_int( struct thread *thread, const int *addr, int *data )
 202 {
 203     *data = ptrace( PTRACE_PEEKDATA, thread->unix_pid, (caddr_t)addr, 0 );
 204     if ( *data == -1 && errno)
 205     {
 206         file_set_error();
 207         return -1;
 208     }
 209     return 0;
 210 }
 211
 212 /* write an int to a thread address space */
 213 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 214 {
 215     int res;
 216     if (mask != ~0)
 217     {
 218         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 219         data = (data & mask) | (res & ~mask);
 220     }
 221     if ((res = ptrace( PTRACE_POKEDATA, thread->unix_pid, (caddr_t)addr, data )) == -1)
 222         file_set_error();
 223     return res;
 224 }