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