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->unix_pid = -1;
  94         thread->unix_tid = -1;
  95         if (debug_level)
  96         {
  97             if (WIFSIGNALED(status))
  98                 fprintf( stderr, "%04x: *exited* signal=%d\n",
  99                          thread->id, WTERMSIG(status) );
 100             else
 101                 fprintf( stderr, "%04x: *exited* status=%d\n",
 102                          thread->id, WEXITSTATUS(status) );
 103         }
 104     }
 105     return 0;
 106 }
 107
 108 /* wait4 wrapper to handle missing __WALL flag in older kernels */
 109 static inline pid_t wait4_wrapper( pid_t pid, int *status, int options, struct rusage *usage )
 110 {
 111 #ifdef __WALL
 112     static int wall_flag = __WALL;
 113
 114     for (;;)
 115     {
 116         pid_t ret = wait4( pid, status, options | wall_flag, usage );
 117         if (ret != -1 || !wall_flag || errno != EINVAL) return ret;
 118         wall_flag = 0;
 119     }
 120 #else
 121     return wait4( pid, status, options, usage );
 122 #endif
 123 }
 124
 125 /* handle a SIGCHLD signal */
 126 void sigchld_callback(void)
 127 {
 128     int pid, status;
 129
 130     for (;;)
 131     {
 132         if (!(pid = wait4_wrapper( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
 133         if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
 134         else break;
 135     }
 136 }
 137
 138 /* wait for a ptraced child to get a certain signal */
 139 static int wait4_thread( struct thread *thread, int signal )
 140 {
 141     int res, status;
 142
 143     start_watchdog();
 144     for (;;)
 145     {
 146         if ((res = wait4_wrapper( get_ptrace_pid(thread), &status, WUNTRACED, NULL )) == -1)
 147         {
 148             if (errno == EINTR)
 149             {
 150                 if (!watchdog_triggered()) continue;
 151                 if (debug_level) fprintf( stderr, "%04x: *watchdog* wait4 aborted\n", thread->id );
 152             }
 153             else if (errno == ECHILD)  /* must have died */
 154             {
 155                 thread->unix_pid = -1;
 156                 thread->unix_tid = -1;
 157             }
 158             else perror( "wait4" );
 159             stop_watchdog();
 160             return 0;
 161         }
 162         res = handle_child_status( thread, res, status, signal );
 163         if (!res || res == signal) break;
 164     }
 165     stop_watchdog();
 166     return (thread->unix_pid != -1);
 167 }
 168
 169 /* return the Unix pid to use in ptrace calls for a given thread */
 170 int get_ptrace_pid( struct thread *thread )
 171 {
 172     if (thread->unix_tid != -1) return thread->unix_tid;
 173     return thread->unix_pid;
 174 }
 175
 176 /* send a signal to a specific thread */
 177 static inline int tkill( int tgid, int pid, int sig )
 178 {
 179     int ret = -ENOSYS;
 180
 181 #ifdef __linux__
 182 # ifdef __i386__
 183     __asm__( "pushl %%ebx\n\t"
 184              "movl %2,%%ebx\n\t"
 185              "int $0x80\n\t"
 186              "popl %%ebx\n\t"
 187              : "=a" (ret)
 188              : "0" (270) /*SYS_tgkill*/, "r" (tgid), "c" (pid), "d" (sig) );
 189     if (ret == -ENOSYS)
 190         __asm__( "pushl %%ebx\n\t"
 191                  "movl %2,%%ebx\n\t"
 192                  "int $0x80\n\t"
 193                  "popl %%ebx\n\t"
 194                  : "=a" (ret)
 195                  : "0" (238) /*SYS_tkill*/, "r" (pid), "c" (sig) );
 196 # elif defined(__x86_64__)
 197     __asm__( "syscall" : "=a" (ret)
 198              : "0" (200) /*SYS_tkill*/, "D" (pid), "S" (sig) );
 199 # endif
 200 #endif  /* __linux__ */
 201
 202     if (ret >= 0) return ret;
 203     errno = -ret;
 204     return -1;
 205 }
 206
 207 /* send a Unix signal to a specific thread */
 208 int send_thread_signal( struct thread *thread, int sig )
 209 {
 210     int ret = -1;
 211
 212     if (thread->unix_pid != -1)
 213     {
 214         if (thread->unix_tid != -1)
 215         {
 216             ret = tkill( thread->unix_pid, thread->unix_tid, sig );
 217             if (ret == -1 && errno == ENOSYS) ret = kill( thread->unix_pid, sig );
 218         }
 219         else ret = kill( thread->unix_pid, sig );
 220
 221         if (ret == -1 && errno == ESRCH) /* thread got killed */
 222         {
 223             thread->unix_pid = -1;
 224             thread->unix_tid = -1;
 225         }
 226     }
 227     return (ret != -1);
 228 }
 229
 230 /* suspend a thread to allow using ptrace on it */
 231 /* you must do a resume_after_ptrace when finished with the thread */
 232 int suspend_for_ptrace( struct thread *thread )
 233 {
 234     /* can't stop a thread while initialisation is in progress */
 235     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
 236
 237     /* this may fail if the client is already being debugged */
 238     if (ptrace( PTRACE_ATTACH, get_ptrace_pid(thread), 0, 0 ) == -1)
 239     {
 240         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 241         goto error;
 242     }
 243     if (wait4_thread( thread, SIGSTOP )) return 1;
 244     resume_after_ptrace( thread );
 245  error:
 246     set_error( STATUS_ACCESS_DENIED );
 247     return 0;
 248 }
 249
 250 /* resume a thread after we have used ptrace on it */
 251 void resume_after_ptrace( struct thread *thread )
 252 {
 253     if (thread->unix_pid == -1) return;
 254     if (ptrace( PTRACE_DETACH, get_ptrace_pid(thread), (caddr_t)1, 0 ) == -1)
 255     {
 256         if (errno == ESRCH) thread->unix_pid = thread->unix_tid = -1;  /* thread got killed */
 257     }
 258 }
 259
 260 /* read an int from a thread address space */
 261 static int read_thread_int( struct thread *thread, const int *addr, int *data )
 262 {
 263     errno = 0;
 264     *data = ptrace( PTRACE_PEEKDATA, get_ptrace_pid(thread), (caddr_t)addr, 0 );
 265     if ( *data == -1 && errno)
 266     {
 267         file_set_error();
 268         return -1;
 269     }
 270     return 0;
 271 }
 272
 273 /* write an int to a thread address space */
 274 static int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask )
 275 {
 276     int res;
 277     if (mask != ~0)
 278     {
 279         if (read_thread_int( thread, addr, &res ) == -1) return -1;
 280         data = (data & mask) | (res & ~mask);
 281     }
 282     if ((res = ptrace( PTRACE_POKEDATA, get_ptrace_pid(thread), (caddr_t)addr, data )) == -1)
 283         file_set_error();
 284     return res;
 285 }
 286
 287 /* read data from a process memory space */
 288 int read_process_memory( struct process *process, const void *ptr, size_t size, char *dest )
 289 {
 290     struct thread *thread = get_process_first_thread( process );
 291     unsigned int first_offset, last_offset, len;
 292     int data, *addr;
 293
 294     if (!thread)  /* process is dead */
 295     {
 296         set_error( STATUS_ACCESS_DENIED );
 297         return 0;
 298     }
 299
 300     first_offset = (unsigned long)ptr % sizeof(int);
 301     last_offset = (size + first_offset) % sizeof(int);
 302     if (!last_offset) last_offset = sizeof(int);
 303
 304     addr = (int *)((char *)ptr - first_offset);
 305     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 306
 307     if (suspend_for_ptrace( thread ))
 308     {
 309         if (len > 1)
 310         {
 311             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 312             memcpy( dest, (char *)&data + first_offset, sizeof(int) - first_offset );
 313             dest += sizeof(int) - first_offset;
 314             first_offset = 0;
 315             len--;
 316         }
 317
 318         while (len > 1)
 319         {
 320             if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 321             memcpy( dest, &data, sizeof(int) );
 322             dest += sizeof(int);
 323             len--;
 324         }
 325
 326         if (read_thread_int( thread, addr++, &data ) == -1) goto done;
 327         memcpy( dest, (char *)&data + first_offset, last_offset - first_offset );
 328         len--;
 329
 330     done:
 331         resume_after_ptrace( thread );
 332     }
 333     return !len;
 334 }
 335
 336 /* make sure we can write to the whole address range */
 337 /* len is the total size (in ints) */
 338 static int check_process_write_access( struct thread *thread, int *addr, size_t len )
 339 {
 340     int page = get_page_size() / sizeof(int);
 341
 342     for (;;)
 343     {
 344         if (write_thread_int( thread, addr, 0, 0 ) == -1) return 0;
 345         if (len <= page) break;
 346         addr += page;
 347         len -= page;
 348     }
 349     return (write_thread_int( thread, addr + len - 1, 0, 0 ) != -1);
 350 }
 351
 352 /* write data to a process memory space */
 353 int write_process_memory( struct process *process, void *ptr, size_t size, const char *src )
 354 {
 355     struct thread *thread = get_process_first_thread( process );
 356     int ret = 0, data = 0;
 357     size_t len;
 358     int *addr;
 359     unsigned int first_mask, first_offset, last_mask, last_offset;
 360
 361     if (!thread)  /* process is dead */
 362     {
 363         set_error( STATUS_ACCESS_DENIED );
 364         return 0;
 365     }
 366
 367     /* compute the mask for the first int */
 368     first_mask = ~0;
 369     first_offset = (unsigned long)ptr % sizeof(int);
 370     memset( &first_mask, 0, first_offset );
 371
 372     /* compute the mask for the last int */
 373     last_offset = (size + first_offset) % sizeof(int);
 374     if (!last_offset) last_offset = sizeof(int);
 375     last_mask = 0;
 376     memset( &last_mask, 0xff, last_offset );
 377
 378     addr = (int *)((char *)ptr - first_offset);
 379     len = (size + first_offset + sizeof(int) - 1) / sizeof(int);
 380
 381     if (suspend_for_ptrace( thread ))
 382     {
 383         if (!check_process_write_access( thread, addr, len ))
 384         {
 385             set_error( STATUS_ACCESS_DENIED );
 386             goto done;
 387         }
 388         /* first word is special */
 389         if (len > 1)
 390         {
 391             memcpy( (char *)&data + first_offset, src, sizeof(int) - first_offset );
 392             src += sizeof(int) - first_offset;
 393             if (write_thread_int( thread, addr++, data, first_mask ) == -1) goto done;
 394             first_offset = 0;
 395             len--;
 396         }
 397         else last_mask &= first_mask;
 398
 399         while (len > 1)
 400         {
 401             memcpy( &data, src, sizeof(int) );
 402             src += sizeof(int);
 403             if (write_thread_int( thread, addr++, data, ~0 ) == -1) goto done;
 404             len--;
 405         }
 406
 407         /* last word is special too */
 408         memcpy( (char *)&data + first_offset, src, last_offset - first_offset );
 409         if (write_thread_int( thread, addr, data, last_mask ) == -1) goto done;
 410         ret = 1;
 411
 412     done:
 413         resume_after_ptrace( thread );
 414     }
 415     return ret;
 416 }
 417
 418 /* retrieve an LDT selector entry */
 419 void get_selector_entry( struct thread *thread, int entry, unsigned int *base,
 420                          unsigned int *limit, unsigned char *flags )
 421 {
 422     if (!thread->process->ldt_copy)
 423     {
 424         set_error( STATUS_ACCESS_DENIED );
 425         return;
 426     }
 427     if (entry >= 8192)
 428     {
 429         set_error( STATUS_INVALID_PARAMETER );  /* FIXME */
 430         return;
 431     }
 432     if (suspend_for_ptrace( thread ))
 433     {
 434         unsigned char flags_buf[4];
 435         int *addr = (int *)thread->process->ldt_copy + entry;
 436         if (read_thread_int( thread, addr, (int *)base ) == -1) goto done;
 437         if (read_thread_int( thread, addr + 8192, (int *)limit ) == -1) goto done;
 438         addr = (int *)thread->process->ldt_copy + 2*8192 + (entry >> 2);
 439         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 440         *flags = flags_buf[entry & 3];
 441     done:
 442         resume_after_ptrace( thread );
 443     }
 444 }