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