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