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