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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, 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 <stdarg.h>
  28 #include <sys/types.h>
  29 #ifdef HAVE_SYS_PTRACE_H
  30 # include <sys/ptrace.h>
  31 #endif
  32 #ifdef HAVE_SYS_PARAM_H
  33 # include <sys/param.h>
  34 #endif
  35 #ifdef HAVE_SYS_WAIT_H
  36 # include <sys/wait.h>
  37 #endif
  38 #ifdef HAVE_SYS_THR_H
  39 # include <sys/ucontext.h>
  40 # include <sys/thr.h>
  41 #endif
  42 #include <unistd.h>
  43
  44 #include "ntstatus.h"
  45 #define WIN32_NO_STATUS
  46 #include "winternl.h"
  47
  48 #include "file.h"
  49 #include "process.h"
  50 #include "thread.h"
  51
  52 #ifdef USE_PTRACE
  53
  54 #ifndef PTRACE_CONT
  55 #define PTRACE_CONT PT_CONTINUE
  56 #endif
  57 #ifndef PTRACE_SINGLESTEP
  58 #define PTRACE_SINGLESTEP PT_STEP
  59 #endif
  60 #ifndef PTRACE_ATTACH
  61 #define PTRACE_ATTACH PT_ATTACH
  62 #endif
  63 #ifndef PTRACE_DETACH
  64 #define PTRACE_DETACH PT_DETACH
  65 #endif
  66 #ifndef PTRACE_PEEKDATA
  67 #define PTRACE_PEEKDATA PT_READ_D
  68 #endif
  69 #ifndef PTRACE_POKEDATA
  70 #define PTRACE_POKEDATA PT_WRITE_D
  71 #endif
  72 #ifndef PTRACE_PEEKUSER
  73 #define PTRACE_PEEKUSER PT_READ_U
  74 #endif
  75 #ifndef PTRACE_POKEUSER
  76 #define PTRACE_POKEUSER PT_WRITE_U
  77 #endif
  78
  79 #ifdef PT_GETDBREGS
  80 #define PTRACE_GETDBREGS PT_GETDBREGS
  81 #endif
  82 #ifdef PT_SETDBREGS
  83 #define PTRACE_SETDBREGS PT_SETDBREGS
  84 #endif
  85
  86 #ifndef HAVE_SYS_PTRACE_H
  87 #define PT_CONTINUE 0
  88 #define PT_ATTACH   1
  89 #define PT_DETACH   2
  90 #define PT_READ_D   3
  91 #define PT_WRITE_D  4
  92 #define PT_STEP     5
  93 static inline int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
  94 #endif  /* HAVE_SYS_PTRACE_H */
  95
  96 /* handle a status returned by wait4 */
  97 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  98 {
  99     if (WIFSTOPPED(status))
 100     {
 101         int sig = WSTOPSIG(status);
 102         if (debug_level && thread)
 103             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
 104         if (sig != want_sig)
 105         {
 106             /* ignore other signals for now */
 107             ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
 108         }
 109         return sig;
 110     }
 111     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
 112     {
 113         thread->unix_pid = -1;
 114         thread->unix_tid = -1;
 115         if (debug_level)
 116         {
 117             if (WIFSIGNALED(status))
 118                 fprintf( stderr, "%04x: *exited* signal=%d\n",
 119                          thread->id, WTERMSIG(status) );
 120             else
 121                 fprintf( stderr, "%04x: *exited* status=%d\n",
 122                          thread->id, WEXITSTATUS(status) );
 123         }
 124     }
 125     return 0;
 126 }
 127
 128 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 129 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 130 {
 131 #ifdef __WALL
 132     static int wall_flag = __WALL;
 133
 134     for (;;)
 135     {
 136         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 137         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 138         wall_flag = 0;
 139     }
 140 #else
 141     return wait4( pid, status, options, usage );
 142 #endif
 143 }
 144
 145 /* handle a SIGCHLD signal */
 146 void sigchld_callback(void)
 147 {
 148     int pid, status;
 149
 150     for (;;)
 151     {
 152         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 153         if (pid != -1)
 154         {
 155             struct thread *thread = get_thread_from_tid( pid );
 156             if (!thread) thread = get_thread_from_pid( pid );
 157             handle_child_status( thread, pid, status, -1 );
 158         }
 159         else break;
 160     }
 161 }
 162
 163 /* return the Unix pid to use in ptrace calls for a given process */
 164 static int get_ptrace_pid( struct thread *thread )
 165 {
 166 #ifdef linux  /* linux always uses thread id */
 167     if (thread->unix_tid != -1) return thread->unix_tid;
 168 #endif
 169     return thread->unix_pid;
 170 }
 171
 172 /* return the Unix tid to use in ptrace calls for a given thread */
 173 static int get_ptrace_tid( struct thread *thread )
 174 {
 175     if (thread->unix_tid != -1) return thread->unix_tid;
 176     return thread->unix_pid;
 177 }
 178
 179 /* wait for a ptraced child to get a certain signal */
 180 static int wait4_thread( struct thread *thread, int signal )
 181 {
 182     int res, status;
 183
 184     start_watchdog();
 185     for (;;)
 186     {
 187         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 188         {
 189             if (errno == EINTR)
 190             {
 191                 if (!watchdog_triggered()) continue;
 192                 if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
 193             }
 194             else if (errno == ECHILD)  /* must have died */
 195             {
 196                 thread->unix_pid = -1;
 197                 thread->unix_tid = -1;
 198             }
 199             else perror( "wait4" );
 200             stop_watchdog();
 201             return 0;
 202         }
 203         res = handle_child_status( thread, res, status, signal );
 204         if (!res || res == signal) break;
 205     }
 206     stop_watchdog();
 207     return (thread->unix_pid != -1);
 208 }
 209
 210 /* send a signal to a specific thread */
 211 static inline int tkill( int tgid, int pid, int sig )
 212 {
 213 #ifdef __linux__
 214     int ret = -ENOSYS;
 215 # ifdef __i386__
 216     __asm__( "pushl %%ebx\n\t"
 217              "movl %2,%%ebx\n\t"
 218              "int $0x80\n\t"
 219              "popl %%ebx\n\t"
 220              : "=a" (ret)
 221              : "0" (270) /*SYS_tgkill*/, "r" (tgid), "c" (pid), "d" (sig) );
 222     if (ret == -ENOSYS)
 223         __asm__( "pushl %%ebx\n\t"
 224                  "movl %2,%%ebx\n\t"
 225                  "int $0x80\n\t"
 226                  "popl %%ebx\n\t"
 227                  : "=a" (ret)
 228                  : "0" (238) /*SYS_tkill*/, "r" (pid), "c" (sig) );
 229 # elif defined(__x86_64__)
 230     __asm__( "syscall" : "=a" (ret)
 231              : "0" (200) /*SYS_tkill*/, "D" (pid), "S" (sig) );
 232 # endif
 233     if (ret >= 0) return ret;
 234     errno = -ret;
 235     return -1;
 236 #elif defined(__FreeBSD__) && defined(HAVE_THR_KILL2)
 237     return thr_kill2( tgid, pid, sig );
 238 #else
 239     errno = ENOSYS;
 240     return -1;
 241 #endif
 242 }
 243
 244 /* initialize the process tracing mechanism */
 245 void init_tracing_mechanism(void)
 246 {
 247     /* no initialization needed for ptrace */
 248 }
 249
 250 /* initialize the per-process tracing mechanism */
 251 void init_process_tracing( struct process *process )
 252 {
 253     /* ptrace setup is done on-demand */
 254 }
 255
 256 /* terminate the per-process tracing mechanism */
 257 void finish_process_tracing( struct process *process )
 258 {
 259 }
 260
 261 /* send a Unix signal to a specific thread */
 262 int send_thread_signal( struct thread *thread, int sig )
 263 {
 264     int ret = -1;
 265
 266     if (thread->unix_pid != -1)
 267     {
 268         if (thread->unix_tid != -1)
 269         {
 270             ret = tkill( thread->unix_pid, thread->unix_tid, sig );
 271             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 272         }
 273         else ret = kill( thread->unix_pid, sig );
 274
 275         if (ret == -1 && errno == ESRCH) /* thread got killed */
 276         {
 277             thread->unix_pid = -1;
 278             thread->unix_tid = -1;
 279         }
 280     }
 281     if (debug_level && ret != -1)
 282         fprintf( stderr, "%04x: *sent signal* signal=%d\n", thread->id, sig );
 283     return (ret != -1);
 284 }
 285
 286 /* resume a thread after we have used ptrace on it */
 287 static void resume_after_ptrace( struct thread *thread )
 288 {
 289     if (thread->unix_pid == -1) return;
 290     if (ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 ) == -1)
 291     {
 292         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 293     }
 294 }
 295
 296 /* suspend a thread to allow using ptrace on it */
 297 /* you must do a resume_after_ptrace when finished with the thread */
 298 static int suspend_for_ptrace( struct thread *thread )
 299 {
 300     /* can't stop a thread while initialisation is in progress */
 301     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 302
 303     /* this may fail if the client is already being debugged */
 304     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 305     {
 306         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 307         goto error;
 308     }
 309     if (wait4_thread( thread, SIGSTOP )) return 1;
 310     resume_after_ptrace( thread );
 311  error:
 312     set_error( STATUS_ACCESS_DENIED );
 313     return 0;
 314 }
 315
 316 /* read an int from a thread address space */
 317 static int read_thread_int( struct thread *thread, int *addr, int *data )
 318 {
 319     errno = 0;
 320     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 321     if ( *data == -1 && errno)
 322     {
 323         file_set_error();
 324         return -1;
 325     }
 326     return 0;
 327 }
 328
 329 /* write an int to a thread address space */
 330 static int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 331 {
 332     int res;
 333     if (mask != ~0u)
 334     {
 335         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 336         data = (data & mask) | (res & ~mask);
 337     }
 338     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 339         file_set_error();
 340     return res;
 341 }
 342
 343 /* return a thread of the process suitable for ptracing */
 344 static struct thread *get_ptrace_thread( struct process *process )
 345 {
 346     struct thread *thread;
 347
 348     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 349     {
 350         if (thread->unix_pid != -1) return thread;
 351     }
 352     set_error( STATUS_ACCESS_DENIED );  /* process is dead */
 353     return NULL;
 354 }
 355
 356 /* read data from a process memory space */
 357 int read_process_memory( struct process *process, const void *ptr, data_size_t size, char *dest )
 358 {
 359     struct thread *thread = get_ptrace_thread( process );
 360     unsigned int first_offset, last_offset, len;
 361     int data, *addr;
 362
 363     if (!thread) return 0;
 364
 365     first_offset = (unsigned long)ptr % sizeof(int);
 366     last_offset = (size + first_offset) % sizeof(int);
 367     if (!last_offset) last_offset = sizeof(int);
 368
 369     addr = (int *)((char *)ptr - first_offset);
 370     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 371
 372     if (suspend_for_ptrace( thread ))
 373     {
 374         if (len > 1)
 375         {
 376             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 377             memcpy( dest, (char *)&data + first_offset, sizeof(int) - first_offset );
 378             dest += sizeof(int) - first_offset;
 379             first_offset = 0;
 380             len--;
 381         }
 382
 383         while (len > 1)
 384         {
 385             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 386             memcpy( dest, &data, sizeof(int) );
 387             dest += sizeof(int);
 388             len--;
 389         }
 390
 391         if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 392         memcpy( dest, (char *)&data + first_offset, last_offset - first_offset );
 393         len--;
 394
 395     done:
 396         resume_after_ptrace( thread );
 397     }
 398     return !len;
 399 }
 400
 401 /* make sure we can write to the whole address range */
 402 /* len is the total size (in ints) */
 403 static int check_process_write_access( struct thread *thread, int *addr, data_size_t len )
 404 {
 405     int page = get_page_size() / sizeof(int);
 406
 407     for (;;)
 408     {
 409         if (write_thread_int( thread, addr, 0, 0 ) == -1) return 0;
 410         if (len <= page) break;
 411         addr += page;
 412         len -= page;
 413     }
 414     return (write_thread_int( thread, addr + len - 1, 0, 0 ) != -1);
 415 }
 416
 417 /* write data to a process memory space */
 418 int write_process_memory( struct process *process, void *ptr, data_size_t size, const char *src )
 419 {
 420     struct thread *thread = get_ptrace_thread( process );
 421     int ret = 0, data = 0;
 422     data_size_t len;
 423     int *addr;
 424     unsigned int first_mask, first_offset, last_mask, last_offset;
 425
 426     if (!thread) return 0;
 427
 428     /* compute the mask for the first int */
 429     first_mask = ~0;
 430     first_offset = (unsigned long)ptr % sizeof(int);
 431     memset( &first_mask, 0, first_offset );
 432
 433     /* compute the mask for the last int */
 434     last_offset = (size + first_offset) % sizeof(int);
 435     if (!last_offset) last_offset = sizeof(int);
 436     last_mask = 0;
 437     memset( &last_mask, 0xff, last_offset );
 438
 439     addr = (int *)((char *)ptr - first_offset);
 440     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 441
 442     if (suspend_for_ptrace( thread ))
 443     {
 444         if (!check_process_write_access( thread, addr, len ))
 445         {
 446             set_error( STATUS_ACCESS_DENIED );
 447             goto done;
 448         }
 449         /* first word is special */
 450         if (len > 1)
 451         {
 452             memcpy( (char *)&data + first_offset, src, sizeof(int) - first_offset );
 453             src += sizeof(int) - first_offset;
 454             if (write_thread_int( thread, addr++, data, first_mask ) == -1) goto done;
 455             first_offset = 0;
 456             len--;
 457         }
 458         else last_mask &= first_mask;
 459
 460         while (len > 1)
 461         {
 462             memcpy( &data, src, sizeof(int) );
 463             src += sizeof(int);
 464             if (write_thread_int( thread, addr++, data, ~0 ) == -1) goto done;
 465             len--;
 466         }
 467
 468         /* last word is special too */
 469         memcpy( (char *)&data + first_offset, src, last_offset - first_offset );
 470         if (write_thread_int( thread, addr, data, last_mask ) == -1) goto done;
 471         ret = 1;
 472
 473     done:
 474         resume_after_ptrace( thread );
 475     }
 476     return ret;
 477 }
 478
 479 /* retrieve an LDT selector entry */
 480 void get_selector_entry( struct thread *thread, int entry, unsigned int *base,
 481                          unsigned int *limit, unsigned char *flags )
 482 {
 483     if (!thread->process->ldt_copy)
 484     {
 485         set_error( STATUS_ACCESS_DENIED );
 486         return;
 487     }
 488     if (entry >= 8192)
 489     {
 490         set_error( STATUS_ACCESS_VIOLATION );
 491         return;
 492     }
 493     if (suspend_for_ptrace( thread ))
 494     {
 495         unsigned char flags_buf[4];
 496         int *addr = (int *)thread->process->ldt_copy + entry;
 497         if (read_thread_int( thread, addr, (int *)base ) == -1) goto done;
 498         if (read_thread_int( thread, addr + 8192, (int *)limit ) == -1) goto done;
 499         addr = (int *)thread->process->ldt_copy + 2*8192 + (entry >> 2);
 500         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 501         *flags = flags_buf[entry & 3];
 502     done:
 503         resume_after_ptrace( thread );
 504     }
 505 }
 506
 507
 508 #if defined(linux) && (defined(__i386__) || defined(__x86_64__))
 509
 510 #ifdef HAVE_SYS_USER_H
 511 # include <sys/user.h>
 512 #endif
 513
 514 /* debug register offset in struct user */
 515 #define DR_OFFSET(dr) ((((struct user *)0)->u_debugreg) + (dr))
 516
 517 /* retrieve the thread x86 registers */
 518 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 519 {
 520     int i, pid = get_ptrace_tid(thread);
 521     long data[8];
 522
 523     /* all other regs are handled on the client side */
 524     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 525
 526     if (!suspend_for_ptrace( thread )) return;
 527
 528     for (i = 0; i < 8; i++)
 529     {
 530         if (i == 4 || i == 5) continue;
 531         errno = 0;
 532         data[i] = ptrace( PTRACE_PEEKUSER, pid, DR_OFFSET(i), 0 );
 533         if ((data[i] == -1) && errno)
 534         {
 535             file_set_error();
 536             goto done;
 537         }
 538     }
 539     context->Dr0 = data[0];
 540     context->Dr1 = data[1];
 541     context->Dr2 = data[2];
 542     context->Dr3 = data[3];
 543     context->Dr6 = data[6];
 544     context->Dr7 = data[7];
 545     context->ContextFlags |= CONTEXT_DEBUG_REGISTERS;
 546 done:
 547     resume_after_ptrace( thread );
 548 }
 549
 550 /* set the thread x86 registers */
 551 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 552 {
 553     int pid = get_ptrace_tid( thread );
 554
 555     /* all other regs are handled on the client side */
 556     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 557
 558     if (!suspend_for_ptrace( thread )) return;
 559
 560     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(0), context->Dr0 ) == -1) goto error;
 561     if (thread->context) thread->context->Dr0 = context->Dr0;
 562     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(1), context->Dr1 ) == -1) goto error;
 563     if (thread->context) thread->context->Dr1 = context->Dr1;
 564     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(2), context->Dr2 ) == -1) goto error;
 565     if (thread->context) thread->context->Dr2 = context->Dr2;
 566     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(3), context->Dr3 ) == -1) goto error;
 567     if (thread->context) thread->context->Dr3 = context->Dr3;
 568     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(6), context->Dr6 ) == -1) goto error;
 569     if (thread->context) thread->context->Dr6 = context->Dr6;
 570     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(7), context->Dr7 ) == -1) goto error;
 571     if (thread->context) thread->context->Dr7 = context->Dr7;
 572     resume_after_ptrace( thread );
 573     return;
 574  error:
 575     file_set_error();
 576     resume_after_ptrace( thread );
 577 }
 578
 579 #elif defined(__i386__) && defined(PTRACE_GETDBREGS) && defined(PTRACE_SETDBREGS) && \
 580     (defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__) || defined(__NetBSD__))
 581
 582 #include <machine/reg.h>
 583
 584 /* retrieve the thread x86 registers */
 585 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 586 {
 587     int pid = get_ptrace_tid(thread);
 588     struct dbreg dbregs;
 589
 590     /* all other regs are handled on the client side */
 591     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 592
 593     if (!suspend_for_ptrace( thread )) return;
 594
 595     if (ptrace( PTRACE_GETDBREGS, pid, (caddr_t) &dbregs, 0 ) == -1) file_set_error();
 596     else
 597     {
 598 #ifdef DBREG_DRX
 599         /* needed for FreeBSD, the structure fields have changed under 5.x */
 600         context->Dr0 = DBREG_DRX((&dbregs), 0);
 601         context->Dr1 = DBREG_DRX((&dbregs), 1);
 602         context->Dr2 = DBREG_DRX((&dbregs), 2);
 603         context->Dr3 = DBREG_DRX((&dbregs), 3);
 604         context->Dr6 = DBREG_DRX((&dbregs), 6);
 605         context->Dr7 = DBREG_DRX((&dbregs), 7);
 606 #else
 607         context->Dr0 = dbregs.dr0;
 608         context->Dr1 = dbregs.dr1;
 609         context->Dr2 = dbregs.dr2;
 610         context->Dr3 = dbregs.dr3;
 611         context->Dr6 = dbregs.dr6;
 612         context->Dr7 = dbregs.dr7;
 613 #endif
 614         context->ContextFlags |= CONTEXT_DEBUG_REGISTERS;
 615     }
 616     resume_after_ptrace( thread );
 617 }
 618
 619 /* set the thread x86 registers */
 620 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 621 {
 622     int pid = get_ptrace_tid(thread);
 623     struct dbreg dbregs;
 624
 625     /* all other regs are handled on the client side */
 626     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 627
 628     if (!suspend_for_ptrace( thread )) return;
 629
 630 #ifdef DBREG_DRX
 631     /* needed for FreeBSD, the structure fields have changed under 5.x */
 632     DBREG_DRX((&dbregs), 0) = context->Dr0;
 633     DBREG_DRX((&dbregs), 1) = context->Dr1;
 634     DBREG_DRX((&dbregs), 2) = context->Dr2;
 635     DBREG_DRX((&dbregs), 3) = context->Dr3;
 636     DBREG_DRX((&dbregs), 4) = 0;
 637     DBREG_DRX((&dbregs), 5) = 0;
 638     DBREG_DRX((&dbregs), 6) = context->Dr6;
 639     DBREG_DRX((&dbregs), 7) = context->Dr7;
 640 #else
 641     dbregs.dr0 = context->Dr0;
 642     dbregs.dr1 = context->Dr1;
 643     dbregs.dr2 = context->Dr2;
 644     dbregs.dr3 = context->Dr3;
 645     dbregs.dr4 = 0;
 646     dbregs.dr5 = 0;
 647     dbregs.dr6 = context->Dr6;
 648     dbregs.dr7 = context->Dr7;
 649 #endif
 650     if (ptrace( PTRACE_SETDBREGS, pid, (caddr_t) &dbregs, 0 ) == -1) file_set_error();
 651     else if (thread->context)  /* update the cached values */
 652     {
 653         thread->context->Dr0 = context->Dr0;
 654         thread->context->Dr1 = context->Dr1;
 655         thread->context->Dr2 = context->Dr2;
 656         thread->context->Dr3 = context->Dr3;
 657         thread->context->Dr6 = context->Dr6;
 658         thread->context->Dr7 = context->Dr7;
 659     }
 660     resume_after_ptrace( thread );
 661 }
 662
 663 #else  /* linux || __FreeBSD__ */
 664
 665 /* retrieve the thread x86 registers */
 666 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 667 {
 668 }
 669
 670 /* set the thread x86 debug registers */
 671 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 672 {
 673 }
 674
 675 #endif  /* linux || __FreeBSD__ */
 676
 677 #endif  /* USE_PTRACE */