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 #ifndef HAVE_SYS_PTRACE_H
  46 #define PT_CONTINUE 0
  47 #define PT_ATTACH   1
  48 #define PT_DETACH   2
  49 #define PT_READ_D   3
  50 #define PT_WRITE_D  4
  51 #define PT_STEP     5
  52 inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
  53 #endif  /* HAVE_SYS_PTRACE_H */
  54
  55 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  56
  57 /* handle a status returned by wait4 */
  58 static int handle_child_status( struct thread *thread, int pid, int status )
  59 {
  60     if (WIFSTOPPED(status))
  61     {
  62         int sig = WSTOPSIG(status);
  63         if (debug_level && thread)
  64             fprintf( stderr, "%08x: *signal* signal=%d\n", (unsigned int)thread, sig );
  65         switch(sig)
  66         {
  67         case SIGSTOP:  /* continue at once if not suspended */
  68             if (thread && (thread->process->suspend + thread->suspend)) break;
  69             /* fall through */
  70         default:  /* ignore other signals for now */
  71             if (thread && get_thread_single_step( thread ))
  72                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
  73             else
  74                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  75             break;
  76         }
  77         return sig;
  78     }
  79     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  80     {
  81         thread->attached = 0;
  82         thread->unix_pid = 0;
  83         if (debug_level)
  84         {
  85             if (WIFSIGNALED(status))
  86                 fprintf( stderr, "%08x: *exited* signal=%d\n",
  87                          (unsigned int)thread, WTERMSIG(status) );
  88             else
  89                 fprintf( stderr, "%08x: *exited* status=%d\n",
  90                          (unsigned int)thread, WEXITSTATUS(status) );
  91         }
  92     }
  93     return 0;
  94 }
  95
  96 /* handle a SIGCHLD signal */
  97 void sigchld_handler()
  98 {
  99     int pid, status;
 100
 101     for (;;)
 102     {
 103         if (!(pid = wait4( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 104         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status );
 105         else break;
 106     }
 107 }
 108
 109 /* wait for a ptraced child to get a certain signal */
 110 void wait4_thread( struct thread *thread, int signal )
 111 {
 112     int res, status;
 113
 114     do
 115     {
 116         if ((res = wait4( thread->unix_pid, &status, WUNTRACED, NULL )) == -1)
 117         {
 118             perror( "wait4" );
 119             return;
 120         }
 121         res = handle_child_status( thread, res, status );
 122     } while (res && res != signal);
 123 }
 124
 125 /* attach to a Unix thread */
 126 static int attach_thread( struct thread *thread )
 127 {
 128     /* this may fail if the client is already being debugged */
 129     if (!use_ptrace) return 0;
 130     if (ptrace( PTRACE_ATTACH, thread->unix_pid, 0, 0 ) == -1)
 131     {
 132         if (errno == ESRCH) thread->unix_pid = 0;  /* process got killed */
 133         return 0;
 134     }
 135     if (debug_level) fprintf( stderr, "%08x: *attached*\n", (unsigned int)thread );
 136     thread->attached = 1;
 137     wait4_thread( thread, SIGSTOP );
 138     return 1;
 139 }
 140
 141 /* detach from a Unix thread and kill it */
 142 void detach_thread( struct thread *thread, int sig )
 143 {
 144     if (!thread->unix_pid) return;
 145     if (thread->attached)
 146     {
 147         /* make sure it is stopped */
 148         suspend_thread( thread, 0 );
 149         if (sig) kill( thread->unix_pid, sig );
 150         if (debug_level) fprintf( stderr, "%08x: *detached*\n", (unsigned int)thread );
 151         ptrace( PTRACE_DETACH, thread->unix_pid, (caddr_t)1, sig );
 152         thread->suspend = 0;  /* detach makes it continue */
 153         thread->attached = 0;
 154     }
 155     else
 156     {
 157         if (sig) kill( thread->unix_pid, sig );
 158         if (thread->suspend + thread->process->suspend) continue_thread( thread );
 159     }
 160 }
 161
 162 /* stop a thread (at the Unix level) */
 163 void stop_thread( struct thread *thread )
 164 {
 165     /* can't stop a thread while initialisation is in progress */
 166     if (!thread->unix_pid || thread->process->init_event) return;
 167     /* first try to attach to it */
 168     if (!thread->attached)
 169         if (attach_thread( thread )) return;  /* this will have stopped it */
 170     /* attached already, or attach failed -> send a signal */
 171     kill( thread->unix_pid, SIGSTOP );
 172     if (thread->attached) wait4_thread( thread, SIGSTOP );
 173 }
 174
 175 /* make a thread continue (at the Unix level) */
 176 void continue_thread( struct thread *thread )
 177 {
 178     if (!thread->unix_pid) return;
 179     if (!thread->attached) kill( thread->unix_pid, SIGCONT );
 180     else ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 181                  thread->unix_pid, (caddr_t)1, SIGSTOP );
 182 }
 183
 184 /* suspend a thread to allow using ptrace on it */
 185 /* you must do a resume_thread when finished with the thread */
 186 int suspend_for_ptrace( struct thread *thread )
 187 {
 188     if (thread->attached)
 189     {
 190         suspend_thread( thread, 0 );
 191         return 1;
 192     }
 193     /* can't stop a thread while initialisation is in progress */
 194     if (!thread->unix_pid || thread->process->init_event) goto error;
 195     thread->suspend++;
 196     if (attach_thread( thread )) return 1;
 197     thread->suspend--;
 198  error:
 199     set_error( STATUS_ACCESS_DENIED );
 200     return 0;
 201 }
 202
 203 /* read an int from a thread address space */
 204 int read_thread_int( struct thread *thread, const int *addr, int *data )
 205 {
 206     *data = ptrace( PTRACE_PEEKDATA, thread->unix_pid, (caddr_t)addr, 0 );
 207     if ( *data == -1 && errno)
 208     {
 209         file_set_error();
 210         return -1;
 211     }
 212     return 0;
 213 }
 214
 215 /* write an int to a thread address space */
 216 int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 217 {
 218     int res;
 219     if (mask != ~0)
 220     {
 221         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 222         data = (data & mask) | (res & ~mask);
 223     }
 224     if ((res = ptrace( PTRACE_POKEDATA, thread->unix_pid, (caddr_t)addr, data )) == -1)
 225         file_set_error();
 226     return res;
 227 }