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     return (ret != -1);
 266 }
 267
 268 /* resume a thread after we have used ptrace on it */
 269 static void resume_after_ptrace( struct thread *thread )
 270 {
 271     if (thread->unix_pid == -1) return;
 272     if (ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 ) == -1)
 273     {
 274         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 275     }
 276 }
 277
 278 /* suspend a thread to allow using ptrace on it */
 279 /* you must do a resume_after_ptrace when finished with the thread */
 280 static int suspend_for_ptrace( struct thread *thread )
 281 {
 282     /* can't stop a thread while initialisation is in progress */
 283     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 284
 285     /* this may fail if the client is already being debugged */
 286     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 287     {
 288         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 289         goto error;
 290     }
 291     if (wait4_thread( thread, SIGSTOP )) return 1;
 292     resume_after_ptrace( thread );
 293  error:
 294     set_error( STATUS_ACCESS_DENIED );
 295     return 0;
 296 }
 297
 298 /* read an int from a thread address space */
 299 static int read_thread_int( struct thread *thread, int *addr, int *data )
 300 {
 301     errno = 0;
 302     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 303     if ( *data == -1 && errno)
 304     {
 305         file_set_error();
 306         return -1;
 307     }
 308     return 0;
 309 }
 310
 311 /* write an int to a thread address space */
 312 static int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 313 {
 314     int res;
 315     if (mask != ~0u)
 316     {
 317         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 318         data = (data & mask) | (res & ~mask);
 319     }
 320     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 321         file_set_error();
 322     return res;
 323 }
 324
 325 /* return a thread of the process suitable for ptracing */
 326 static struct thread *get_ptrace_thread( struct process *process )
 327 {
 328     struct thread *thread;
 329
 330     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 331     {
 332         if (thread->unix_pid != -1) return thread;
 333     }
 334     set_error( STATUS_ACCESS_DENIED );  /* process is dead */
 335     return NULL;
 336 }
 337
 338 /* read data from a process memory space */
 339 int read_process_memory( struct process *process, const void *ptr, data_size_t size, char *dest )
 340 {
 341     struct thread *thread = get_ptrace_thread( process );
 342     unsigned int first_offset, last_offset, len;
 343     int data, *addr;
 344
 345     if (!thread) return 0;
 346
 347     first_offset = (unsigned long)ptr % sizeof(int);
 348     last_offset = (size + first_offset) % sizeof(int);
 349     if (!last_offset) last_offset = sizeof(int);
 350
 351     addr = (int *)((char *)ptr - first_offset);
 352     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 353
 354     if (suspend_for_ptrace( thread ))
 355     {
 356         if (len > 1)
 357         {
 358             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 359             memcpy( dest, (char *)&data + first_offset, sizeof(int) - first_offset );
 360             dest += sizeof(int) - first_offset;
 361             first_offset = 0;
 362             len--;
 363         }
 364
 365         while (len > 1)
 366         {
 367             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 368             memcpy( dest, &data, sizeof(int) );
 369             dest += sizeof(int);
 370             len--;
 371         }
 372
 373         if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 374         memcpy( dest, (char *)&data + first_offset, last_offset - first_offset );
 375         len--;
 376
 377     done:
 378         resume_after_ptrace( thread );
 379     }
 380     return !len;
 381 }
 382
 383 /* make sure we can write to the whole address range */
 384 /* len is the total size (in ints) */
 385 static int check_process_write_access( struct thread *thread, int *addr, data_size_t len )
 386 {
 387     int page = get_page_size() / sizeof(int);
 388
 389     for (;;)
 390     {
 391         if (write_thread_int( thread, addr, 0, 0 ) == -1) return 0;
 392         if (len <= page) break;
 393         addr += page;
 394         len -= page;
 395     }
 396     return (write_thread_int( thread, addr + len - 1, 0, 0 ) != -1);
 397 }
 398
 399 /* write data to a process memory space */
 400 int write_process_memory( struct process *process, void *ptr, data_size_t size, const char *src )
 401 {
 402     struct thread *thread = get_ptrace_thread( process );
 403     int ret = 0, data = 0;
 404     data_size_t len;
 405     int *addr;
 406     unsigned int first_mask, first_offset, last_mask, last_offset;
 407
 408     if (!thread) return 0;
 409
 410     /* compute the mask for the first int */
 411     first_mask = ~0;
 412     first_offset = (unsigned long)ptr % sizeof(int);
 413     memset( &first_mask, 0, first_offset );
 414
 415     /* compute the mask for the last int */
 416     last_offset = (size + first_offset) % sizeof(int);
 417     if (!last_offset) last_offset = sizeof(int);
 418     last_mask = 0;
 419     memset( &last_mask, 0xff, last_offset );
 420
 421     addr = (int *)((char *)ptr - first_offset);
 422     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 423
 424     if (suspend_for_ptrace( thread ))
 425     {
 426         if (!check_process_write_access( thread, addr, len ))
 427         {
 428             set_error( STATUS_ACCESS_DENIED );
 429             goto done;
 430         }
 431         /* first word is special */
 432         if (len > 1)
 433         {
 434             memcpy( (char *)&data + first_offset, src, sizeof(int) - first_offset );
 435             src += sizeof(int) - first_offset;
 436             if (write_thread_int( thread, addr++, data, first_mask ) == -1) goto done;
 437             first_offset = 0;
 438             len--;
 439         }
 440         else last_mask &= first_mask;
 441
 442         while (len > 1)
 443         {
 444             memcpy( &data, src, sizeof(int) );
 445             src += sizeof(int);
 446             if (write_thread_int( thread, addr++, data, ~0 ) == -1) goto done;
 447             len--;
 448         }
 449
 450         /* last word is special too */
 451         memcpy( (char *)&data + first_offset, src, last_offset - first_offset );
 452         if (write_thread_int( thread, addr, data, last_mask ) == -1) goto done;
 453         ret = 1;
 454
 455     done:
 456         resume_after_ptrace( thread );
 457     }
 458     return ret;
 459 }
 460
 461 /* retrieve an LDT selector entry */
 462 void get_selector_entry( struct thread *thread, int entry, unsigned int *base,
 463                          unsigned int *limit, unsigned char *flags )
 464 {
 465     if (!thread->process->ldt_copy)
 466     {
 467         set_error( STATUS_ACCESS_DENIED );
 468         return;
 469     }
 470     if (entry >= 8192)
 471     {
 472         set_error( STATUS_ACCESS_VIOLATION );
 473         return;
 474     }
 475     if (suspend_for_ptrace( thread ))
 476     {
 477         unsigned char flags_buf[4];
 478         int *addr = (int *)thread->process->ldt_copy + entry;
 479         if (read_thread_int( thread, addr, (int *)base ) == -1) goto done;
 480         if (read_thread_int( thread, addr + 8192, (int *)limit ) == -1) goto done;
 481         addr = (int *)thread->process->ldt_copy + 2*8192 + (entry >> 2);
 482         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 483         *flags = flags_buf[entry & 3];
 484     done:
 485         resume_after_ptrace( thread );
 486     }
 487 }
 488
 489
 490 #if defined(linux) && (defined(__i386__) || defined(__x86_64__))
 491
 492 #ifdef HAVE_SYS_USER_H
 493 # include <sys/user.h>
 494 #endif
 495
 496 /* debug register offset in struct user */
 497 #define DR_OFFSET(dr) ((((struct user *)0)->u_debugreg) + (dr))
 498
 499 /* retrieve the thread x86 registers */
 500 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 501 {
 502     int i, pid = get_ptrace_pid(thread);
 503     long data[8];
 504
 505     /* all other regs are handled on the client side */
 506     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 507
 508     if (!suspend_for_ptrace( thread )) return;
 509
 510     for (i = 0; i < 8; i++)
 511     {
 512         if (i == 4 || i == 5) continue;
 513         errno = 0;
 514         data[i] = ptrace( PTRACE_PEEKUSER, pid, DR_OFFSET(i), 0 );
 515         if ((data[i] == -1) && errno)
 516         {
 517             file_set_error();
 518             goto done;
 519         }
 520     }
 521     context->Dr0 = data[0];
 522     context->Dr1 = data[1];
 523     context->Dr2 = data[2];
 524     context->Dr3 = data[3];
 525     context->Dr6 = data[6];
 526     context->Dr7 = data[7];
 527     context->ContextFlags |= CONTEXT_DEBUG_REGISTERS;
 528 done:
 529     resume_after_ptrace( thread );
 530 }
 531
 532 /* set the thread x86 registers */
 533 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 534 {
 535     int pid = get_ptrace_pid( thread );
 536
 537     /* all other regs are handled on the client side */
 538     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 539
 540     if (!suspend_for_ptrace( thread )) return;
 541
 542     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(0), context->Dr0 ) == -1) goto error;
 543     if (thread->context) thread->context->Dr0 = context->Dr0;
 544     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(1), context->Dr1 ) == -1) goto error;
 545     if (thread->context) thread->context->Dr1 = context->Dr1;
 546     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(2), context->Dr2 ) == -1) goto error;
 547     if (thread->context) thread->context->Dr2 = context->Dr2;
 548     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(3), context->Dr3 ) == -1) goto error;
 549     if (thread->context) thread->context->Dr3 = context->Dr3;
 550     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(6), context->Dr6 ) == -1) goto error;
 551     if (thread->context) thread->context->Dr6 = context->Dr6;
 552     if (ptrace( PTRACE_POKEUSER, pid, DR_OFFSET(7), context->Dr7 ) == -1) goto error;
 553     if (thread->context) thread->context->Dr7 = context->Dr7;
 554     resume_after_ptrace( thread );
 555     return;
 556  error:
 557     file_set_error();
 558     resume_after_ptrace( thread );
 559 }
 560
 561 #elif defined(__i386__) && defined(PTRACE_GETDBREGS) && defined(PTRACE_SETDBREGS) && \
 562     (defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__) || defined(__NetBSD__))
 563
 564 #include <machine/reg.h>
 565
 566 /* retrieve the thread x86 registers */
 567 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 568 {
 569     int pid = get_ptrace_pid(thread);
 570     struct dbreg dbregs;
 571
 572     /* all other regs are handled on the client side */
 573     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 574
 575     if (!suspend_for_ptrace( thread )) return;
 576
 577     if (ptrace( PTRACE_GETDBREGS, pid, (caddr_t) &dbregs, 0 ) == -1) file_set_error();
 578     else
 579     {
 580 #ifdef DBREG_DRX
 581         /* needed for FreeBSD, the structure fields have changed under 5.x */
 582         context->Dr0 = DBREG_DRX((&dbregs), 0);
 583         context->Dr1 = DBREG_DRX((&dbregs), 1);
 584         context->Dr2 = DBREG_DRX((&dbregs), 2);
 585         context->Dr3 = DBREG_DRX((&dbregs), 3);
 586         context->Dr6 = DBREG_DRX((&dbregs), 6);
 587         context->Dr7 = DBREG_DRX((&dbregs), 7);
 588 #else
 589         context->Dr0 = dbregs.dr0;
 590         context->Dr1 = dbregs.dr1;
 591         context->Dr2 = dbregs.dr2;
 592         context->Dr3 = dbregs.dr3;
 593         context->Dr6 = dbregs.dr6;
 594         context->Dr7 = dbregs.dr7;
 595 #endif
 596         context->ContextFlags |= CONTEXT_DEBUG_REGISTERS;
 597     }
 598     resume_after_ptrace( thread );
 599 }
 600
 601 /* set the thread x86 registers */
 602 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 603 {
 604     int pid = get_ptrace_pid(thread);
 605     struct dbreg dbregs;
 606
 607     /* all other regs are handled on the client side */
 608     assert( (flags | CONTEXT_i386) == CONTEXT_DEBUG_REGISTERS );
 609
 610     if (!suspend_for_ptrace( thread )) return;
 611
 612 #ifdef DBREG_DRX
 613     /* needed for FreeBSD, the structure fields have changed under 5.x */
 614     DBREG_DRX((&dbregs), 0) = context->Dr0;
 615     DBREG_DRX((&dbregs), 1) = context->Dr1;
 616     DBREG_DRX((&dbregs), 2) = context->Dr2;
 617     DBREG_DRX((&dbregs), 3) = context->Dr3;
 618     DBREG_DRX((&dbregs), 4) = 0;
 619     DBREG_DRX((&dbregs), 5) = 0;
 620     DBREG_DRX((&dbregs), 6) = context->Dr6;
 621     DBREG_DRX((&dbregs), 7) = context->Dr7;
 622 #else
 623     dbregs.dr0 = context->Dr0;
 624     dbregs.dr1 = context->Dr1;
 625     dbregs.dr2 = context->Dr2;
 626     dbregs.dr3 = context->Dr3;
 627     dbregs.dr4 = 0;
 628     dbregs.dr5 = 0;
 629     dbregs.dr6 = context->Dr6;
 630     dbregs.dr7 = context->Dr7;
 631 #endif
 632     if (ptrace( PTRACE_SETDBREGS, pid, (caddr_t) &dbregs, 0 ) == -1) file_set_error();
 633     else if (thread->context)  /* update the cached values */
 634     {
 635         thread->context->Dr0 = context->Dr0;
 636         thread->context->Dr1 = context->Dr1;
 637         thread->context->Dr2 = context->Dr2;
 638         thread->context->Dr3 = context->Dr3;
 639         thread->context->Dr6 = context->Dr6;
 640         thread->context->Dr7 = context->Dr7;
 641     }
 642     resume_after_ptrace( thread );
 643 }
 644
 645 #else  /* linux || __FreeBSD__ */
 646
 647 /* retrieve the thread x86 registers */
 648 void get_thread_context( struct thread *thread, CONTEXT *context, unsigned int flags )
 649 {
 650 }
 651
 652 /* set the thread x86 debug registers */
 653 void set_thread_context( struct thread *thread, const CONTEXT *context, unsigned int flags )
 654 {
 655 }
 656
 657 #endif  /* linux || __FreeBSD__ */
 658
 659 #endif  /* USE_PTRACE */