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_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 /* handle a status returned by wait4 */
  75 static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
  76 {
  77     if (WIFSTOPPED(status))
  78     {
  79         int sig = WSTOPSIG(status);
  80         if (debug_level && thread)
  81             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
  82         if (sig != want_sig)
  83         {
  84             /* ignore other signals for now */
  85             ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
  86         }
  87         return sig;
  88     }
  89     if (thread && (WIFSIGNALED(status) || WIFEXITED(status)))
  90     {
  91         thread->unix_pid = -1;
  92         thread->unix_tid = -1;
  93         if (debug_level)
  94         {
  95             if (WIFSIGNALED(status))
  96                 fprintf( stderr, "%04x: *exited* signal=%d\n",
  97                          thread->id, WTERMSIG(status) );
  98             else
  99                 fprintf( stderr, "%04x: *exited* status=%d\n",
 100                          thread->id, WEXITSTATUS(status) );
 101         }
 102     }
 103     return 0;
 104 }
 105
 106 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 107 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 108 {
 109 #ifdef __WALL
 110     static int wall_flag = __WALL;
 111
 112     for (;;)
 113     {
 114         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 115         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 116         wall_flag = 0;
 117     }
 118 #else
 119     return wait4( pid, status, options, usage );
 120 #endif
 121 }
 122
 123 /* handle a SIGCHLD signal */
 124 void sigchld_callback(void)
 125 {
 126     int pid, status;
 127
 128     for (;;)
 129     {
 130         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 131         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 132         else break;
 133     }
 134 }
 135
 136 /* wait for a ptraced child to get a certain signal */
 137 static int wait4_thread( struct thread *thread, int signal )
 138 {
 139     int res, status;
 140
 141     start_watchdog();
 142     for (;;)
 143     {
 144         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 145         {
 146             if (errno == EINTR)
 147             {
 148                 if (!watchdog_triggered()) continue;
 149                 if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
 150             }
 151             else if (errno == ECHILD)  /* must have died */
 152             {
 153                 thread->unix_pid = -1;
 154                 thread->unix_tid = -1;
 155             }
 156             else perror( "wait4" );
 157             stop_watchdog();
 158             return 0;
 159         }
 160         res = handle_child_status( thread, res, status, signal );
 161         if (!res || res == signal) break;
 162     }
 163     stop_watchdog();
 164     return (thread->unix_pid != -1);
 165 }
 166
 167 /* return the Unix pid to use in ptrace calls for a given thread */
 168 int get_ptrace_pid( struct thread *thread )
 169 {
 170     if (thread->unix_tid != -1) return thread->unix_tid;
 171     return thread->unix_pid;
 172 }
 173
 174 /* send a signal to a specific thread */
 175 static inline int tkill( int tgid, int pid, int sig )
 176 {
 177     int ret = -ENOSYS;
 178
 179 #ifdef __linux__
 180 # ifdef __i386__
 181     __asm__( "pushl %%ebx\n\t"
 182              "movl %2,%%ebx\n\t"
 183              "int $0x80\n\t"
 184              "popl %%ebx\n\t"
 185              : "=a" (ret)
 186              : "0" (270) /*SYS_tgkill*/, "r" (tgid), "c" (pid), "d" (sig) );
 187     if (ret == -ENOSYS)
 188         __asm__( "pushl %%ebx\n\t"
 189                  "movl %2,%%ebx\n\t"
 190                  "int $0x80\n\t"
 191                  "popl %%ebx\n\t"
 192                  : "=a" (ret)
 193                  : "0" (238) /*SYS_tkill*/, "r" (pid), "c" (sig) );
 194 # elif defined(__x86_64__)
 195     __asm__( "syscall" : "=a" (ret)
 196              : "0" (200) /*SYS_tkill*/, "D" (pid), "S" (sig) );
 197 # endif
 198 #endif  /* __linux__ */
 199
 200     if (ret >= 0) return ret;
 201     errno = -ret;
 202     return -1;
 203 }
 204
 205 /* send a Unix signal to a specific thread */
 206 int send_thread_signal( struct thread *thread, int sig )
 207 {
 208     int ret = -1;
 209
 210     if (thread->unix_pid != -1)
 211     {
 212         if (thread->unix_tid != -1)
 213         {
 214             ret = tkill( thread->unix_pid, thread->unix_tid, sig );
 215             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 216         }
 217         else ret = kill( thread->unix_pid, sig );
 218
 219         if (ret == -1 && errno == ESRCH) /* thread got killed */
 220         {
 221             thread->unix_pid = -1;
 222             thread->unix_tid = -1;
 223         }
 224     }
 225     return (ret != -1);
 226 }
 227
 228 /* suspend a thread to allow using ptrace on it */
 229 /* you must do a resume_after_ptrace when finished with the thread */
 230 int suspend_for_ptrace( struct thread *thread )
 231 {
 232     /* can't stop a thread while initialisation is in progress */
 233     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 234
 235     /* this may fail if the client is already being debugged */
 236     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 237     {
 238         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 239         goto error;
 240     }
 241     if (wait4_thread( thread, SIGSTOP )) return 1;
 242     resume_after_ptrace( thread );
 243  error:
 244     set_error( STATUS_ACCESS_DENIED );
 245     return 0;
 246 }
 247
 248 /* resume a thread after we have used ptrace on it */
 249 void resume_after_ptrace( struct thread *thread )
 250 {
 251     if (thread->unix_pid == -1) return;
 252     if (ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 ) == -1)
 253     {
 254         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 255     }
 256 }
 257
 258 /* read an int from a thread address space */
 259 static int read_thread_int( struct thread *thread, const int *addr, int *data )
 260 {
 261     errno = 0;
 262     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 263     if ( *data == -1 && errno)
 264     {
 265         file_set_error();
 266         return -1;
 267     }
 268     return 0;
 269 }
 270
 271 /* write an int to a thread address space */
 272 static int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 273 {
 274     int res;
 275     if (mask != ~0)
 276     {
 277         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 278         data = (data & mask) | (res & ~mask);
 279     }
 280     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 281         file_set_error();
 282     return res;
 283 }
 284
 285 /* read data from a process memory space */
 286 int read_process_memory( struct process *process, const void *ptr, size_t size, char *dest )
 287 {
 288     struct thread *thread = get_process_first_thread( process );
 289     unsigned int first_offset, last_offset, len;
 290     int data, *addr;
 291
 292     if (!thread)  /* process is dead */
 293     {
 294         set_error( STATUS_ACCESS_DENIED );
 295         return 0;
 296     }
 297
 298     first_offset = (unsigned long)ptr % sizeof(int);
 299     last_offset = (size + first_offset) % sizeof(int);
 300     if (!last_offset) last_offset = sizeof(int);
 301
 302     addr = (int *)((char *)ptr - first_offset);
 303     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 304
 305     if (suspend_for_ptrace( thread ))
 306     {
 307         if (len > 1)
 308         {
 309             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 310             memcpy( dest, (char *)&data + first_offset, sizeof(int) - first_offset );
 311             dest += sizeof(int) - first_offset;
 312             first_offset = 0;
 313             len--;
 314         }
 315
 316         while (len > 1)
 317         {
 318             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 319             memcpy( dest, &data, sizeof(int) );
 320             dest += sizeof(int);
 321             len--;
 322         }
 323
 324         if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 325         memcpy( dest, (char *)&data + first_offset, last_offset - first_offset );
 326         len--;
 327
 328     done:
 329         resume_after_ptrace( thread );
 330     }
 331     return !len;
 332 }
 333
 334 /* make sure we can write to the whole address range */
 335 /* len is the total size (in ints) */
 336 static int check_process_write_access( struct thread *thread, int *addr, size_t len )
 337 {
 338     int page = get_page_size() / sizeof(int);
 339
 340     for (;;)
 341     {
 342         if (write_thread_int( thread, addr, 0, 0 ) == -1) return 0;
 343         if (len <= page) break;
 344         addr += page;
 345         len -= page;
 346     }
 347     return (write_thread_int( thread, addr + len - 1, 0, 0 ) != -1);
 348 }
 349
 350 /* write data to a process memory space */
 351 int write_process_memory( struct process *process, void *ptr, size_t size, const char *src )
 352 {
 353     struct thread *thread = get_process_first_thread( process );
 354     int ret = 0, data = 0;
 355     size_t len;
 356     int *addr;
 357     unsigned int first_mask, first_offset, last_mask, last_offset;
 358
 359     if (!thread)  /* process is dead */
 360     {
 361         set_error( STATUS_ACCESS_DENIED );
 362         return 0;
 363     }
 364
 365     /* compute the mask for the first int */
 366     first_mask = ~0;
 367     first_offset = (unsigned long)ptr % sizeof(int);
 368     memset( &first_mask, 0, first_offset );
 369
 370     /* compute the mask for the last int */
 371     last_offset = (size + first_offset) % sizeof(int);
 372     if (!last_offset) last_offset = sizeof(int);
 373     last_mask = 0;
 374     memset( &last_mask, 0xff, last_offset );
 375
 376     addr = (int *)((char *)ptr - first_offset);
 377     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 378
 379     if (suspend_for_ptrace( thread ))
 380     {
 381         if (!check_process_write_access( thread, addr, len ))
 382         {
 383             set_error( STATUS_ACCESS_DENIED );
 384             goto done;
 385         }
 386         /* first word is special */
 387         if (len > 1)
 388         {
 389             memcpy( (char *)&data + first_offset, src, sizeof(int) - first_offset );
 390             src += sizeof(int) - first_offset;
 391             if (write_thread_int( thread, addr++, data, first_mask ) == -1) goto done;
 392             first_offset = 0;
 393             len--;
 394         }
 395         else last_mask &= first_mask;
 396
 397         while (len > 1)
 398         {
 399             memcpy( &data, src, sizeof(int) );
 400             src += sizeof(int);
 401             if (write_thread_int( thread, addr++, data, ~0 ) == -1) goto done;
 402             len--;
 403         }
 404
 405         /* last word is special too */
 406         memcpy( (char *)&data + first_offset, src, last_offset - first_offset );
 407         if (write_thread_int( thread, addr, data, last_mask ) == -1) goto done;
 408         ret = 1;
 409
 410     done:
 411         resume_after_ptrace( thread );
 412     }
 413     return ret;
 414 }
 415
 416 /* retrieve an LDT selector entry */
 417 void get_selector_entry( struct thread *thread, int entry, unsigned int *base,
 418                          unsigned int *limit, unsigned char *flags )
 419 {
 420     if (!thread->process->ldt_copy)
 421     {
 422         set_error( STATUS_ACCESS_DENIED );
 423         return;
 424     }
 425     if (entry >= 8192)
 426     {
 427         set_error( STATUS_INVALID_PARAMETER );  /* FIXME */
 428         return;
 429     }
 430     if (suspend_for_ptrace( thread ))
 431     {
 432         unsigned char flags_buf[4];
 433         int *addr = (int *)thread->process->ldt_copy + entry;
 434         if (read_thread_int( thread, addr, (int *)base ) == -1) goto done;
 435         if (read_thread_int( thread, addr + 8192, (int *)limit ) == -1) goto done;
 436         addr = (int *)thread->process->ldt_copy + 2*8192 + (entry >> 2);
 437         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 438         *flags = flags_buf[entry & 3];
 439     done:
 440         resume_after_ptrace( thread );
 441     }
 442 }