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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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_WAIT_H
  33 # include <sys/wait.h>
  34 #endif
  35 #include <unistd.h>
  36
  37 #include "ntstatus.h"
  38 #define WIN32_NO_STATUS
  39 #include "winternl.h"
  40
  41 #include "file.h"
  42 #include "process.h"
  43 #include "thread.h"
  44
  45 #ifndef PTRACE_CONT
  46 #define PTRACE_CONT PT_CONTINUE
  47 #endif
  48 #ifndef PTRACE_SINGLESTEP
  49 #define PTRACE_SINGLESTEP PT_STEP
  50 #endif
  51 #ifndef PTRACE_ATTACH
  52 #define PTRACE_ATTACH PT_ATTACH
  53 #endif
  54 #ifndef PTRACE_DETACH
  55 #define PTRACE_DETACH PT_DETACH
  56 #endif
  57 #ifndef PTRACE_PEEKDATA
  58 #define PTRACE_PEEKDATA PT_READ_D
  59 #endif
  60 #ifndef PTRACE_POKEDATA
  61 #define PTRACE_POKEDATA PT_WRITE_D
  62 #endif
  63
  64 #ifndef HAVE_SYS_PTRACE_H
  65 #define PT_CONTINUE 0
  66 #define PT_ATTACH   1
  67 #define PT_DETACH   2
  68 #define PT_READ_D   3
  69 #define PT_WRITE_D  4
  70 #define PT_STEP     5
  71 inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
  72 #endif  /* HAVE_SYS_PTRACE_H */
  73
  74 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
  75
  76 /* handle a status returned by wait4 */
  77 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  78 {
  79     if (WIFSTOPPED(status))
  80     {
  81         int sig = WSTOPSIG(status);
  82         if (debug_level && thread)
  83             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
  84         if (sig != want_sig)
  85         {
  86             /* ignore other signals for now */
  87             ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  88         }
  89         return sig;
  90     }
  91     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  92     {
  93         thread->attached = 0;
  94         thread->unix_pid = -1;
  95         thread->unix_tid = -1;
  96         if (debug_level)
  97         {
  98             if (WIFSIGNALED(status))
  99                 fprintf( stderr, "%04x: *exited* signal=%d\n",
 100                          thread->id, WTERMSIG(status) );
 101             else
 102                 fprintf( stderr, "%04x: *exited* status=%d\n",
 103                          thread->id, WEXITSTATUS(status) );
 104         }
 105     }
 106     return 0;
 107 }
 108
 109 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 110 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 111 {
 112 #ifdef __WALL
 113     static int wall_flag = __WALL;
 114
 115     for (;;)
 116     {
 117         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 118         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 119         wall_flag = 0;
 120     }
 121 #else
 122     return wait4( pid, status, options, usage );
 123 #endif
 124 }
 125
 126 /* handle a SIGCHLD signal */
 127 void sigchld_callback(void)
 128 {
 129     int pid, status;
 130
 131     for (;;)
 132     {
 133         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 134         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 135         else break;
 136     }
 137 }
 138
 139 /* wait for a ptraced child to get a certain signal */
 140 static int wait4_thread( struct thread *thread, int signal )
 141 {
 142     int res, status;
 143
 144     start_watchdog();
 145     for (;;)
 146     {
 147         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 148         {
 149             if (errno == EINTR)
 150             {
 151                 if (!watchdog_triggered()) continue;
 152                 if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
 153             }
 154             else if (errno == ECHILD)  /* must have died */
 155             {
 156                 thread->unix_pid = -1;
 157                 thread->unix_tid = -1;
 158                 thread->attached = 0;
 159             }
 160             else perror( "wait4" );
 161             stop_watchdog();
 162             return 0;
 163         }
 164         res = handle_child_status( thread, res, status, signal );
 165         if (!res || res == signal) break;
 166     }
 167     stop_watchdog();
 168     return (thread->unix_pid != -1);
 169 }
 170
 171 /* return the Unix pid to use in ptrace calls for a given thread */
 172 int get_ptrace_pid( struct thread *thread )
 173 {
 174     if (thread->unix_tid != -1) return thread->unix_tid;
 175     return thread->unix_pid;
 176 }
 177
 178 /* send a Unix signal to a specific thread */
 179 int send_thread_signal( struct thread *thread, int sig )
 180 {
 181     int ret = -1;
 182
 183     if (thread->unix_pid != -1)
 184     {
 185         if (thread->unix_tid != -1)
 186         {
 187             ret = tkill( thread->unix_pid, thread->unix_tid, sig );
 188             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 189         }
 190         else ret = kill( thread->unix_pid, sig );
 191
 192         if (ret == -1 && errno == ESRCH) /* thread got killed */
 193         {
 194             thread->unix_pid = -1;
 195             thread->unix_tid = -1;
 196             thread->attached = 0;
 197         }
 198     }
 199     return (ret != -1);
 200 }
 201
 202 /* attach to a Unix process with ptrace */
 203 int attach_process( struct process *process )
 204 {
 205     struct thread *thread;
 206     int ret = 1;
 207
 208     if (list_empty( &process->thread_list ))  /* need at least one running thread */
 209     {
 210         set_error( STATUS_ACCESS_DENIED );
 211         return 0;
 212     }
 213
 214     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 215     {
 216         if (thread->attached) continue;
 217         if (suspend_for_ptrace( thread )) resume_after_ptrace( thread );
 218         else ret = 0;
 219     }
 220     return ret;
 221 }
 222
 223 /* detach from a ptraced Unix process */
 224 void detach_process( struct process *process )
 225 {
 226     struct thread *thread;
 227
 228     LIST_FOR_EACH_ENTRY( thread, &process->thread_list, struct thread, proc_entry )
 229     {
 230         if (thread->attached)
 231         {
 232             /* make sure it is stopped */
 233             suspend_for_ptrace( thread );
 234             if (thread->unix_pid == -1) return;
 235             if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
 236             ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 );
 237             thread->attached = 0;
 238         }
 239     }
 240 }
 241
 242 /* suspend a thread to allow using ptrace on it */
 243 /* you must do a resume_after_ptrace when finished with the thread */
 244 int suspend_for_ptrace( struct thread *thread )
 245 {
 246     /* can't stop a thread while initialisation is in progress */
 247     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 248
 249     if (thread->attached)
 250     {
 251         if (!send_thread_signal( thread, SIGSTOP )) goto error;
 252     }
 253     else
 254     {
 255         /* this may fail if the client is already being debugged */
 256         if (!use_ptrace) goto error;
 257         if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 258         {
 259             if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 260             goto error;
 261         }
 262         if (debug_level) fprintf( stderr, "%04x: *attached*\n", thread->id );
 263         thread->attached = 1;
 264     }
 265     if (wait4_thread( thread, SIGSTOP )) return 1;
 266     resume_after_ptrace( thread );
 267  error:
 268     set_error( STATUS_ACCESS_DENIED );
 269     return 0;
 270 }
 271
 272 /* resume a thread after we have used ptrace on it */
 273 void resume_after_ptrace( struct thread *thread )
 274 {
 275     if (thread->unix_pid == -1) return;
 276     assert( thread->attached );
 277     ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
 278             get_ptrace_pid(thread), (caddr_t)1, 0 /* cancel the SIGSTOP */ );
 279 }
 280
 281 /* read an int from a thread address space */
 282 static int read_thread_int( struct thread *thread, const int *addr, int *data )
 283 {
 284     errno = 0;
 285     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 286     if ( *data == -1 && errno)
 287     {
 288         file_set_error();
 289         return -1;
 290     }
 291     return 0;
 292 }
 293
 294 /* write an int to a thread address space */
 295 static int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 296 {
 297     int res;
 298     if (mask != ~0)
 299     {
 300         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 301         data = (data & mask) | (res & ~mask);
 302     }
 303     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 304         file_set_error();
 305     return res;
 306 }
 307
 308 /* read data from a process memory space */
 309 int read_process_memory( struct process *process, const void *ptr, size_t size, char *dest )
 310 {
 311     struct thread *thread = get_process_first_thread( process );
 312     unsigned int first_offset, last_offset, len;
 313     int data, *addr;
 314
 315     if (!thread)  /* process is dead */
 316     {
 317         set_error( STATUS_ACCESS_DENIED );
 318         return 0;
 319     }
 320
 321     first_offset = (unsigned long)ptr % sizeof(int);
 322     last_offset = (size + first_offset) % sizeof(int);
 323     if (!last_offset) last_offset = sizeof(int);
 324
 325     addr = (int *)((char *)ptr - first_offset);
 326     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 327
 328     if (suspend_for_ptrace( thread ))
 329     {
 330         if (len > 1)
 331         {
 332             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 333             memcpy( dest, (char *)&data + first_offset, sizeof(int) - first_offset );
 334             dest += sizeof(int) - first_offset;
 335             first_offset = 0;
 336             len--;
 337         }
 338
 339         while (len > 1)
 340         {
 341             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 342             memcpy( dest, &data, sizeof(int) );
 343             dest += sizeof(int);
 344             len--;
 345         }
 346
 347         if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 348         memcpy( dest, (char *)&data + first_offset, last_offset - first_offset );
 349         len--;
 350
 351     done:
 352         resume_after_ptrace( thread );
 353     }
 354     return !len;
 355 }
 356
 357 /* make sure we can write to the whole address range */
 358 /* len is the total size (in ints) */
 359 static int check_process_write_access( struct thread *thread, int *addr, size_t len )
 360 {
 361     int page = get_page_size() / sizeof(int);
 362
 363     for (;;)
 364     {
 365         if (write_thread_int( thread, addr, 0, 0 ) == -1) return 0;
 366         if (len <= page) break;
 367         addr += page;
 368         len -= page;
 369     }
 370     return (write_thread_int( thread, addr + len - 1, 0, 0 ) != -1);
 371 }
 372
 373 /* write data to a process memory space */
 374 int write_process_memory( struct process *process, void *ptr, size_t size, const char *src )
 375 {
 376     struct thread *thread = get_process_first_thread( process );
 377     int ret = 0, data = 0;
 378     size_t len;
 379     int *addr;
 380     unsigned int first_mask, first_offset, last_mask, last_offset;
 381
 382     if (!thread)  /* process is dead */
 383     {
 384         set_error( STATUS_ACCESS_DENIED );
 385         return 0;
 386     }
 387
 388     /* compute the mask for the first int */
 389     first_mask = ~0;
 390     first_offset = (unsigned long)ptr % sizeof(int);
 391     memset( &first_mask, 0, first_offset );
 392
 393     /* compute the mask for the last int */
 394     last_offset = (size + first_offset) % sizeof(int);
 395     if (!last_offset) last_offset = sizeof(int);
 396     last_mask = 0;
 397     memset( &last_mask, 0xff, last_offset );
 398
 399     addr = (int *)((char *)ptr - first_offset);
 400     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 401
 402     if (suspend_for_ptrace( thread ))
 403     {
 404         if (!check_process_write_access( thread, addr, len ))
 405         {
 406             set_error( STATUS_ACCESS_DENIED );
 407             goto done;
 408         }
 409         /* first word is special */
 410         if (len > 1)
 411         {
 412             memcpy( (char *)&data + first_offset, src, sizeof(int) - first_offset );
 413             src += sizeof(int) - first_offset;
 414             if (write_thread_int( thread, addr++, data, first_mask ) == -1) goto done;
 415             first_offset = 0;
 416             len--;
 417         }
 418         else last_mask &= first_mask;
 419
 420         while (len > 1)
 421         {
 422             memcpy( &data, src, sizeof(int) );
 423             src += sizeof(int);
 424             if (write_thread_int( thread, addr++, data, ~0 ) == -1) goto done;
 425             len--;
 426         }
 427
 428         /* last word is special too */
 429         memcpy( (char *)&data + first_offset, src, last_offset - first_offset );
 430         if (write_thread_int( thread, addr, data, last_mask ) == -1) goto done;
 431         ret = 1;
 432
 433     done:
 434         resume_after_ptrace( thread );
 435     }
 436     return ret;
 437 }
 438
 439 /* retrieve an LDT selector entry */
 440 void get_selector_entry( struct thread *thread, int entry, unsigned int *base,
 441                          unsigned int *limit, unsigned char *flags )
 442 {
 443     if (!thread->process->ldt_copy)
 444     {
 445         set_error( STATUS_ACCESS_DENIED );
 446         return;
 447     }
 448     if (entry >= 8192)
 449     {
 450         set_error( STATUS_INVALID_PARAMETER );  /* FIXME */
 451         return;
 452     }
 453     if (suspend_for_ptrace( thread ))
 454     {
 455         unsigned char flags_buf[4];
 456         int *addr = (int *)thread->process->ldt_copy + entry;
 457         if (read_thread_int( thread, addr, (int *)base ) == -1) goto done;
 458         if (read_thread_int( thread, addr + 8192, (int *)limit ) == -1) goto done;
 459         addr = (int *)thread->process->ldt_copy + 2*8192 + (entry >> 2);
 460         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 461         *flags = flags_buf[entry & 3];
 462     done:
 463         resume_after_ptrace( thread );
 464     }
 465 }