kernel/ptrace.c

   1 /*
   2  * linux/kernel/ptrace.c
   3  *
   4  * (C) Copyright 1999 Linus Torvalds
   5  *
   6  * Common interfaces for "ptrace()" which we do not want
   7  * to continually duplicate across every architecture.
   8  */
   9
  10 #include <linux/capability.h>
  11 #include <linux/module.h>
  12 #include <linux/sched.h>
  13 #include <linux/errno.h>
  14 #include <linux/mm.h>
  15 #include <linux/highmem.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/smp_lock.h>
  18 #include <linux/ptrace.h>
  19 #include <linux/security.h>
  20 #include <linux/signal.h>
  21 #include <linux/audit.h>
  22 #include <linux/pid_namespace.h>
  23 #include <linux/syscalls.h>
  24 #include <linux/uaccess.h>
  25
  26
  27 /*
  28  * Initialize a new task whose father had been ptraced.
  29  *
  30  * Called from copy_process().
  31  */
  32 void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
  33 {
  34         arch_ptrace_fork(child, clone_flags);
  35 }
  36
  37 /*
  38  * ptrace a task: make the debugger its new parent and
  39  * move it to the ptrace list.
  40  *
  41  * Must be called with the tasklist lock write-held.
  42  */
  43 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
  44 {
  45         BUG_ON(!list_empty(&child->ptrace_entry));
  46         list_add(&child->ptrace_entry, &new_parent->ptraced);
  47         child->parent = new_parent;
  48 }
  49
  50 /*
  51  * Turn a tracing stop into a normal stop now, since with no tracer there
  52  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
  53  * signal sent that would resume the child, but didn't because it was in
  54  * TASK_TRACED, resume it now.
  55  * Requires that irqs be disabled.
  56  */
  57 static void ptrace_untrace(struct task_struct *child)
  58 {
  59         spin_lock(&child->sighand->siglock);
  60         if (task_is_traced(child)) {
  61                 /*
  62                  * If the group stop is completed or in progress,
  63                  * this thread was already counted as stopped.
  64                  */
  65                 if (child->signal->flags & SIGNAL_STOP_STOPPED ||
  66                     child->signal->group_stop_count)
  67                         __set_task_state(child, TASK_STOPPED);
  68                 else
  69                         signal_wake_up(child, 1);
  70         }
  71         spin_unlock(&child->sighand->siglock);
  72 }
  73
  74 /*
  75  * unptrace a task: move it back to its original parent and
  76  * remove it from the ptrace list.
  77  *
  78  * Must be called with the tasklist lock write-held.
  79  */
  80 void __ptrace_unlink(struct task_struct *child)
  81 {
  82         BUG_ON(!child->ptrace);
  83
  84         child->ptrace = 0;
  85         child->parent = child->real_parent;
  86         list_del_init(&child->ptrace_entry);
  87
  88         arch_ptrace_untrace(child);
  89         if (task_is_traced(child))
  90                 ptrace_untrace(child);
  91 }
  92
  93 /*
  94  * Check that we have indeed attached to the thing..
  95  */
  96 int ptrace_check_attach(struct task_struct *child, int kill)
  97 {
  98         int ret = -ESRCH;
  99
 100         /*
 101          * We take the read lock around doing both checks to close a
 102          * possible race where someone else was tracing our child and
 103          * detached between these two checks.  After this locked check,
 104          * we are sure that this is our traced child and that can only
 105          * be changed by us so it's not changing right after this.
 106          */
 107         read_lock(&tasklist_lock);
 108         if ((child->ptrace & PT_PTRACED) && child->parent == current) {
 109                 ret = 0;
 110                 /*
 111                  * child->sighand can't be NULL, release_task()
 112                  * does ptrace_unlink() before __exit_signal().
 113                  */
 114                 spin_lock_irq(&child->sighand->siglock);
 115                 if (task_is_stopped(child))
 116                         child->state = TASK_TRACED;
 117                 else if (!task_is_traced(child) && !kill)
 118                         ret = -ESRCH;
 119                 spin_unlock_irq(&child->sighand->siglock);
 120         }
 121         read_unlock(&tasklist_lock);
 122
 123         if (!ret && !kill)
 124                 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
 125
 126         /* All systems go.. */
 127         return ret;
 128 }
 129
 130 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 131 {
 132         const struct cred *cred = current_cred(), *tcred;
 133
 134         /* May we inspect the given task?
 135          * This check is used both for attaching with ptrace
 136          * and for allowing access to sensitive information in /proc.
 137          *
 138          * ptrace_attach denies several cases that /proc allows
 139          * because setting up the necessary parent/child relationship
 140          * or halting the specified task is impossible.
 141          */
 142         int dumpable = 0;
 143         /* Don't let security modules deny introspection */
 144         if (task == current)
 145                 return 0;
 146         rcu_read_lock();
 147         tcred = __task_cred(task);
 148         if ((cred->uid != tcred->euid ||
 149              cred->uid != tcred->suid ||
 150              cred->uid != tcred->uid  ||
 151              cred->gid != tcred->egid ||
 152              cred->gid != tcred->sgid ||
 153              cred->gid != tcred->gid) &&
 154             !capable(CAP_SYS_PTRACE)) {
 155                 rcu_read_unlock();
 156                 return -EPERM;
 157         }
 158         rcu_read_unlock();
 159         smp_rmb();
 160         if (task->mm)
 161                 dumpable = get_dumpable(task->mm);
 162         if (!dumpable && !capable(CAP_SYS_PTRACE))
 163                 return -EPERM;
 164
 165         return security_ptrace_may_access(task, mode);
 166 }
 167
 168 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
 169 {
 170         int err;
 171         task_lock(task);
 172         err = __ptrace_may_access(task, mode);
 173         task_unlock(task);
 174         return !err;
 175 }
 176
 177 int ptrace_attach(struct task_struct *task)
 178 {
 179         int retval;
 180         unsigned long flags;
 181
 182         audit_ptrace(task);
 183
 184         retval = -EPERM;
 185         if (same_thread_group(task, current))
 186                 goto out;
 187
 188         /* Protect the target's credential calculations against our
 189          * interference; SUID, SGID and LSM creds get determined differently
 190          * under ptrace.
 191          */
 192         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
 193         if (retval  < 0)
 194                 goto out;
 195
 196         retval = -EPERM;
 197 repeat:
 198         /*
 199          * Nasty, nasty.
 200          *
 201          * We want to hold both the task-lock and the
 202          * tasklist_lock for writing at the same time.
 203          * But that's against the rules (tasklist_lock
 204          * is taken for reading by interrupts on other
 205          * cpu's that may have task_lock).
 206          */
 207         task_lock(task);
 208         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 209                 task_unlock(task);
 210                 do {
 211                         cpu_relax();
 212                 } while (!write_can_lock(&tasklist_lock));
 213                 goto repeat;
 214         }
 215
 216         if (!task->mm)
 217                 goto bad;
 218         /* the same process cannot be attached many times */
 219         if (task->ptrace & PT_PTRACED)
 220                 goto bad;
 221         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 222         if (retval)
 223                 goto bad;
 224
 225         /* Go */
 226         task->ptrace |= PT_PTRACED;
 227         if (capable(CAP_SYS_PTRACE))
 228                 task->ptrace |= PT_PTRACE_CAP;
 229
 230         __ptrace_link(task, current);
 231
 232         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 233 bad:
 234         write_unlock_irqrestore(&tasklist_lock, flags);
 235         task_unlock(task);
 236         mutex_unlock(&task->cred_guard_mutex);
 237 out:
 238         return retval;
 239 }
 240
 241 /*
 242  * Called with irqs disabled, returns true if childs should reap themselves.
 243  */
 244 static int ignoring_children(struct sighand_struct *sigh)
 245 {
 246         int ret;
 247         spin_lock(&sigh->siglock);
 248         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 249               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 250         spin_unlock(&sigh->siglock);
 251         return ret;
 252 }
 253
 254 /*
 255  * Called with tasklist_lock held for writing.
 256  * Unlink a traced task, and clean it up if it was a traced zombie.
 257  * Return true if it needs to be reaped with release_task().
 258  * (We can't call release_task() here because we already hold tasklist_lock.)
 259  *
 260  * If it's a zombie, our attachedness prevented normal parent notification
 261  * or self-reaping.  Do notification now if it would have happened earlier.
 262  * If it should reap itself, return true.
 263  *
 264  * If it's our own child, there is no notification to do.
 265  * But if our normal children self-reap, then this child
 266  * was prevented by ptrace and we must reap it now.
 267  */
 268 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 269 {
 270         __ptrace_unlink(p);
 271
 272         if (p->exit_state == EXIT_ZOMBIE) {
 273                 if (!task_detached(p) && thread_group_empty(p)) {
 274                         if (!same_thread_group(p->real_parent, tracer))
 275                                 do_notify_parent(p, p->exit_signal);
 276                         else if (ignoring_children(tracer->sighand))
 277                                 p->exit_signal = -1;
 278                 }
 279                 if (task_detached(p)) {
 280                         /* Mark it as in the process of being reaped. */
 281                         p->exit_state = EXIT_DEAD;
 282                         return true;
 283                 }
 284         }
 285
 286         return false;
 287 }
 288
 289 int ptrace_detach(struct task_struct *child, unsigned int data)
 290 {
 291         bool dead = false;
 292
 293         if (!valid_signal(data))
 294                 return -EIO;
 295
 296         /* Architecture-specific hardware disable .. */
 297         ptrace_disable(child);
 298         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 299
 300         write_lock_irq(&tasklist_lock);
 301         /*
 302          * This child can be already killed. Make sure de_thread() or
 303          * our sub-thread doing do_wait() didn't do release_task() yet.
 304          */
 305         if (child->ptrace) {
 306                 child->exit_code = data;
 307                 dead = __ptrace_detach(current, child);
 308         }
 309         write_unlock_irq(&tasklist_lock);
 310
 311         if (unlikely(dead))
 312                 release_task(child);
 313
 314         return 0;
 315 }
 316
 317 /*
 318  * Detach all tasks we were using ptrace on.
 319  */
 320 void exit_ptrace(struct task_struct *tracer)
 321 {
 322         struct task_struct *p, *n;
 323         LIST_HEAD(ptrace_dead);
 324
 325         write_lock_irq(&tasklist_lock);
 326         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 327                 if (__ptrace_detach(tracer, p))
 328                         list_add(&p->ptrace_entry, &ptrace_dead);
 329         }
 330         write_unlock_irq(&tasklist_lock);
 331
 332         BUG_ON(!list_empty(&tracer->ptraced));
 333
 334         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 335                 list_del_init(&p->ptrace_entry);
 336                 release_task(p);
 337         }
 338 }
 339
 340 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 341 {
 342         int copied = 0;
 343
 344         while (len > 0) {
 345                 char buf[128];
 346                 int this_len, retval;
 347
 348                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 349                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 350                 if (!retval) {
 351                         if (copied)
 352                                 break;
 353                         return -EIO;
 354                 }
 355                 if (copy_to_user(dst, buf, retval))
 356                         return -EFAULT;
 357                 copied += retval;
 358                 src += retval;
 359                 dst += retval;
 360                 len -= retval;
 361         }
 362         return copied;
 363 }
 364
 365 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 366 {
 367         int copied = 0;
 368
 369         while (len > 0) {
 370                 char buf[128];
 371                 int this_len, retval;
 372
 373                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 374                 if (copy_from_user(buf, src, this_len))
 375                         return -EFAULT;
 376                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 377                 if (!retval) {
 378                         if (copied)
 379                                 break;
 380                         return -EIO;
 381                 }
 382                 copied += retval;
 383                 src += retval;
 384                 dst += retval;
 385                 len -= retval;
 386         }
 387         return copied;
 388 }
 389
 390 static int ptrace_setoptions(struct task_struct *child, long data)
 391 {
 392         child->ptrace &= ~PT_TRACE_MASK;
 393
 394         if (data & PTRACE_O_TRACESYSGOOD)
 395                 child->ptrace |= PT_TRACESYSGOOD;
 396
 397         if (data & PTRACE_O_TRACEFORK)
 398                 child->ptrace |= PT_TRACE_FORK;
 399
 400         if (data & PTRACE_O_TRACEVFORK)
 401                 child->ptrace |= PT_TRACE_VFORK;
 402
 403         if (data & PTRACE_O_TRACECLONE)
 404                 child->ptrace |= PT_TRACE_CLONE;
 405
 406         if (data & PTRACE_O_TRACEEXEC)
 407                 child->ptrace |= PT_TRACE_EXEC;
 408
 409         if (data & PTRACE_O_TRACEVFORKDONE)
 410                 child->ptrace |= PT_TRACE_VFORK_DONE;
 411
 412         if (data & PTRACE_O_TRACEEXIT)
 413                 child->ptrace |= PT_TRACE_EXIT;
 414
 415         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 416 }
 417
 418 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 419 {
 420         int error = -ESRCH;
 421
 422         read_lock(&tasklist_lock);
 423         if (likely(child->sighand != NULL)) {
 424                 error = -EINVAL;
 425                 spin_lock_irq(&child->sighand->siglock);
 426                 if (likely(child->last_siginfo != NULL)) {
 427                         *info = *child->last_siginfo;
 428                         error = 0;
 429                 }
 430                 spin_unlock_irq(&child->sighand->siglock);
 431         }
 432         read_unlock(&tasklist_lock);
 433         return error;
 434 }
 435
 436 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 437 {
 438         int error = -ESRCH;
 439
 440         read_lock(&tasklist_lock);
 441         if (likely(child->sighand != NULL)) {
 442                 error = -EINVAL;
 443                 spin_lock_irq(&child->sighand->siglock);
 444                 if (likely(child->last_siginfo != NULL)) {
 445                         *child->last_siginfo = *info;
 446                         error = 0;
 447                 }
 448                 spin_unlock_irq(&child->sighand->siglock);
 449         }
 450         read_unlock(&tasklist_lock);
 451         return error;
 452 }
 453
 454
 455 #ifdef PTRACE_SINGLESTEP
 456 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 457 #else
 458 #define is_singlestep(request)          0
 459 #endif
 460
 461 #ifdef PTRACE_SINGLEBLOCK
 462 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 463 #else
 464 #define is_singleblock(request)         0
 465 #endif
 466
 467 #ifdef PTRACE_SYSEMU
 468 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 469 #else
 470 #define is_sysemu_singlestep(request)   0
 471 #endif
 472
 473 static int ptrace_resume(struct task_struct *child, long request, long data)
 474 {
 475         if (!valid_signal(data))
 476                 return -EIO;
 477
 478         if (request == PTRACE_SYSCALL)
 479                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 480         else
 481                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 482
 483 #ifdef TIF_SYSCALL_EMU
 484         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 485                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 486         else
 487                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 488 #endif
 489
 490         if (is_singleblock(request)) {
 491                 if (unlikely(!arch_has_block_step()))
 492                         return -EIO;
 493                 user_enable_block_step(child);
 494         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 495                 if (unlikely(!arch_has_single_step()))
 496                         return -EIO;
 497                 user_enable_single_step(child);
 498         } else {
 499                 user_disable_single_step(child);
 500         }
 501
 502         child->exit_code = data;
 503         wake_up_process(child);
 504
 505         return 0;
 506 }
 507
 508 int ptrace_request(struct task_struct *child, long request,
 509                    long addr, long data)
 510 {
 511         int ret = -EIO;
 512         siginfo_t siginfo;
 513
 514         switch (request) {
 515         case PTRACE_PEEKTEXT:
 516         case PTRACE_PEEKDATA:
 517                 return generic_ptrace_peekdata(child, addr, data);
 518         case PTRACE_POKETEXT:
 519         case PTRACE_POKEDATA:
 520                 return generic_ptrace_pokedata(child, addr, data);
 521
 522 #ifdef PTRACE_OLDSETOPTIONS
 523         case PTRACE_OLDSETOPTIONS:
 524 #endif
 525         case PTRACE_SETOPTIONS:
 526                 ret = ptrace_setoptions(child, data);
 527                 break;
 528         case PTRACE_GETEVENTMSG:
 529                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 530                 break;
 531
 532         case PTRACE_GETSIGINFO:
 533                 ret = ptrace_getsiginfo(child, &siginfo);
 534                 if (!ret)
 535                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 536                                                    &siginfo);
 537                 break;
 538
 539         case PTRACE_SETSIGINFO:
 540                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 541                                    sizeof siginfo))
 542                         ret = -EFAULT;
 543                 else
 544                         ret = ptrace_setsiginfo(child, &siginfo);
 545                 break;
 546
 547         case PTRACE_DETACH:      /* detach a process that was attached. */
 548                 ret = ptrace_detach(child, data);
 549                 break;
 550
 551 #ifdef PTRACE_SINGLESTEP
 552         case PTRACE_SINGLESTEP:
 553 #endif
 554 #ifdef PTRACE_SINGLEBLOCK
 555         case PTRACE_SINGLEBLOCK:
 556 #endif
 557 #ifdef PTRACE_SYSEMU
 558         case PTRACE_SYSEMU:
 559         case PTRACE_SYSEMU_SINGLESTEP:
 560 #endif
 561         case PTRACE_SYSCALL:
 562         case PTRACE_CONT:
 563                 return ptrace_resume(child, request, data);
 564
 565         case PTRACE_KILL:
 566                 if (child->exit_state)  /* already dead */
 567                         return 0;
 568                 return ptrace_resume(child, request, SIGKILL);
 569
 570         default:
 571                 break;
 572         }
 573
 574         return ret;
 575 }
 576
 577 /**
 578  * ptrace_traceme  --  helper for PTRACE_TRACEME
 579  *
 580  * Performs checks and sets PT_PTRACED.
 581  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 582  */
 583 int ptrace_traceme(void)
 584 {
 585         int ret = -EPERM;
 586
 587         /*
 588          * Are we already being traced?
 589          */
 590 repeat:
 591         task_lock(current);
 592         if (!(current->ptrace & PT_PTRACED)) {
 593                 /*
 594                  * See ptrace_attach() comments about the locking here.
 595                  */
 596                 unsigned long flags;
 597                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 598                         task_unlock(current);
 599                         do {
 600                                 cpu_relax();
 601                         } while (!write_can_lock(&tasklist_lock));
 602                         goto repeat;
 603                 }
 604
 605                 ret = security_ptrace_traceme(current->parent);
 606
 607                 /*
 608                  * Check PF_EXITING to ensure ->real_parent has not passed
 609                  * exit_ptrace(). Otherwise we don't report the error but
 610                  * pretend ->real_parent untraces us right after return.
 611                  */
 612                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 613                         current->ptrace |= PT_PTRACED;
 614                         __ptrace_link(current, current->real_parent);
 615                 }
 616
 617                 write_unlock_irqrestore(&tasklist_lock, flags);
 618         }
 619         task_unlock(current);
 620         return ret;
 621 }
 622
 623 /**
 624  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 625  * @pid:       process id to grab a task_struct reference of
 626  *
 627  * This function is a helper for ptrace implementations.  It checks
 628  * permissions and then grabs a task struct for use of the actual
 629  * ptrace implementation.
 630  *
 631  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 632  */
 633 struct task_struct *ptrace_get_task_struct(pid_t pid)
 634 {
 635         struct task_struct *child;
 636
 637         read_lock(&tasklist_lock);
 638         child = find_task_by_vpid(pid);
 639         if (child)
 640                 get_task_struct(child);
 641
 642         read_unlock(&tasklist_lock);
 643         if (!child)
 644                 return ERR_PTR(-ESRCH);
 645         return child;
 646 }
 647
 648 #ifndef arch_ptrace_attach
 649 #define arch_ptrace_attach(child)       do { } while (0)
 650 #endif
 651
 652 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 653 {
 654         struct task_struct *child;
 655         long ret;
 656
 657         /*
 658          * This lock_kernel fixes a subtle race with suid exec
 659          */
 660         lock_kernel();
 661         if (request == PTRACE_TRACEME) {
 662                 ret = ptrace_traceme();
 663                 if (!ret)
 664                         arch_ptrace_attach(current);
 665                 goto out;
 666         }
 667
 668         child = ptrace_get_task_struct(pid);
 669         if (IS_ERR(child)) {
 670                 ret = PTR_ERR(child);
 671                 goto out;
 672         }
 673
 674         if (request == PTRACE_ATTACH) {
 675                 ret = ptrace_attach(child);
 676                 /*
 677                  * Some architectures need to do book-keeping after
 678                  * a ptrace attach.
 679                  */
 680                 if (!ret)
 681                         arch_ptrace_attach(child);
 682                 goto out_put_task_struct;
 683         }
 684
 685         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 686         if (ret < 0)
 687                 goto out_put_task_struct;
 688
 689         ret = arch_ptrace(child, request, addr, data);
 690
 691  out_put_task_struct:
 692         put_task_struct(child);
 693  out:
 694         unlock_kernel();
 695         return ret;
 696 }
 697
 698 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 699 {
 700         unsigned long tmp;
 701         int copied;
 702
 703         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 704         if (copied != sizeof(tmp))
 705                 return -EIO;
 706         return put_user(tmp, (unsigned long __user *)data);
 707 }
 708
 709 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 710 {
 711         int copied;
 712
 713         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 714         return (copied == sizeof(data)) ? 0 : -EIO;
 715 }
 716
 717 #if defined CONFIG_COMPAT
 718 #include <linux/compat.h>
 719
 720 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 721                           compat_ulong_t addr, compat_ulong_t data)
 722 {
 723         compat_ulong_t __user *datap = compat_ptr(data);
 724         compat_ulong_t word;
 725         siginfo_t siginfo;
 726         int ret;
 727
 728         switch (request) {
 729         case PTRACE_PEEKTEXT:
 730         case PTRACE_PEEKDATA:
 731                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 732                 if (ret != sizeof(word))
 733                         ret = -EIO;
 734                 else
 735                         ret = put_user(word, datap);
 736                 break;
 737
 738         case PTRACE_POKETEXT:
 739         case PTRACE_POKEDATA:
 740                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 741                 ret = (ret != sizeof(data) ? -EIO : 0);
 742                 break;
 743
 744         case PTRACE_GETEVENTMSG:
 745                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 746                 break;
 747
 748         case PTRACE_GETSIGINFO:
 749                 ret = ptrace_getsiginfo(child, &siginfo);
 750                 if (!ret)
 751                         ret = copy_siginfo_to_user32(
 752                                 (struct compat_siginfo __user *) datap,
 753                                 &siginfo);
 754                 break;
 755
 756         case PTRACE_SETSIGINFO:
 757                 memset(&siginfo, 0, sizeof siginfo);
 758                 if (copy_siginfo_from_user32(
 759                             &siginfo, (struct compat_siginfo __user *) datap))
 760                         ret = -EFAULT;
 761                 else
 762                         ret = ptrace_setsiginfo(child, &siginfo);
 763                 break;
 764
 765         default:
 766                 ret = ptrace_request(child, request, addr, data);
 767         }
 768
 769         return ret;
 770 }
 771
 772 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 773                                   compat_long_t addr, compat_long_t data)
 774 {
 775         struct task_struct *child;
 776         long ret;
 777
 778         /*
 779          * This lock_kernel fixes a subtle race with suid exec
 780          */
 781         lock_kernel();
 782         if (request == PTRACE_TRACEME) {
 783                 ret = ptrace_traceme();
 784                 goto out;
 785         }
 786
 787         child = ptrace_get_task_struct(pid);
 788         if (IS_ERR(child)) {
 789                 ret = PTR_ERR(child);
 790                 goto out;
 791         }
 792
 793         if (request == PTRACE_ATTACH) {
 794                 ret = ptrace_attach(child);
 795                 /*
 796                  * Some architectures need to do book-keeping after
 797                  * a ptrace attach.
 798                  */
 799                 if (!ret)
 800                         arch_ptrace_attach(child);
 801                 goto out_put_task_struct;
 802         }
 803
 804         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 805         if (!ret)
 806                 ret = compat_arch_ptrace(child, request, addr, data);
 807
 808  out_put_task_struct:
 809         put_task_struct(child);
 810  out:
 811         unlock_kernel();
 812         return ret;
 813 }
 814 #endif  /* CONFIG_COMPAT */