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 exec's credential calculations against our interference;
 189          * SUID, SGID and LSM creds get determined differently under ptrace.
 190          */
 191         retval = mutex_lock_interruptible(&task->cred_exec_mutex);
 192         if (retval  < 0)
 193                 goto out;
 194
 195         retval = -EPERM;
 196 repeat:
 197         /*
 198          * Nasty, nasty.
 199          *
 200          * We want to hold both the task-lock and the
 201          * tasklist_lock for writing at the same time.
 202          * But that's against the rules (tasklist_lock
 203          * is taken for reading by interrupts on other
 204          * cpu's that may have task_lock).
 205          */
 206         task_lock(task);
 207         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 208                 task_unlock(task);
 209                 do {
 210                         cpu_relax();
 211                 } while (!write_can_lock(&tasklist_lock));
 212                 goto repeat;
 213         }
 214
 215         if (!task->mm)
 216                 goto bad;
 217         /* the same process cannot be attached many times */
 218         if (task->ptrace & PT_PTRACED)
 219                 goto bad;
 220         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 221         if (retval)
 222                 goto bad;
 223
 224         /* Go */
 225         task->ptrace |= PT_PTRACED;
 226         if (capable(CAP_SYS_PTRACE))
 227                 task->ptrace |= PT_PTRACE_CAP;
 228
 229         __ptrace_link(task, current);
 230
 231         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 232 bad:
 233         write_unlock_irqrestore(&tasklist_lock, flags);
 234         task_unlock(task);
 235         mutex_unlock(&task->cred_exec_mutex);
 236 out:
 237         return retval;
 238 }
 239
 240 /*
 241  * Called with irqs disabled, returns true if childs should reap themselves.
 242  */
 243 static int ignoring_children(struct sighand_struct *sigh)
 244 {
 245         int ret;
 246         spin_lock(&sigh->siglock);
 247         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 248               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 249         spin_unlock(&sigh->siglock);
 250         return ret;
 251 }
 252
 253 /*
 254  * Called with tasklist_lock held for writing.
 255  * Unlink a traced task, and clean it up if it was a traced zombie.
 256  * Return true if it needs to be reaped with release_task().
 257  * (We can't call release_task() here because we already hold tasklist_lock.)
 258  *
 259  * If it's a zombie, our attachedness prevented normal parent notification
 260  * or self-reaping.  Do notification now if it would have happened earlier.
 261  * If it should reap itself, return true.
 262  *
 263  * If it's our own child, there is no notification to do.
 264  * But if our normal children self-reap, then this child
 265  * was prevented by ptrace and we must reap it now.
 266  */
 267 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 268 {
 269         __ptrace_unlink(p);
 270
 271         if (p->exit_state == EXIT_ZOMBIE) {
 272                 if (!task_detached(p) && thread_group_empty(p)) {
 273                         if (!same_thread_group(p->real_parent, tracer))
 274                                 do_notify_parent(p, p->exit_signal);
 275                         else if (ignoring_children(tracer->sighand))
 276                                 p->exit_signal = -1;
 277                 }
 278                 if (task_detached(p)) {
 279                         /* Mark it as in the process of being reaped. */
 280                         p->exit_state = EXIT_DEAD;
 281                         return true;
 282                 }
 283         }
 284
 285         return false;
 286 }
 287
 288 int ptrace_detach(struct task_struct *child, unsigned int data)
 289 {
 290         bool dead = false;
 291
 292         if (!valid_signal(data))
 293                 return -EIO;
 294
 295         /* Architecture-specific hardware disable .. */
 296         ptrace_disable(child);
 297         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 298
 299         write_lock_irq(&tasklist_lock);
 300         /*
 301          * This child can be already killed. Make sure de_thread() or
 302          * our sub-thread doing do_wait() didn't do release_task() yet.
 303          */
 304         if (child->ptrace) {
 305                 child->exit_code = data;
 306                 dead = __ptrace_detach(current, child);
 307                 if (!child->exit_state)
 308                         wake_up_process(child);
 309         }
 310         write_unlock_irq(&tasklist_lock);
 311
 312         if (unlikely(dead))
 313                 release_task(child);
 314
 315         return 0;
 316 }
 317
 318 /*
 319  * Detach all tasks we were using ptrace on.
 320  */
 321 void exit_ptrace(struct task_struct *tracer)
 322 {
 323         struct task_struct *p, *n;
 324         LIST_HEAD(ptrace_dead);
 325
 326         write_lock_irq(&tasklist_lock);
 327         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 328                 if (__ptrace_detach(tracer, p))
 329                         list_add(&p->ptrace_entry, &ptrace_dead);
 330         }
 331         write_unlock_irq(&tasklist_lock);
 332
 333         BUG_ON(!list_empty(&tracer->ptraced));
 334
 335         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 336                 list_del_init(&p->ptrace_entry);
 337                 release_task(p);
 338         }
 339 }
 340
 341 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 342 {
 343         int copied = 0;
 344
 345         while (len > 0) {
 346                 char buf[128];
 347                 int this_len, retval;
 348
 349                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 350                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 351                 if (!retval) {
 352                         if (copied)
 353                                 break;
 354                         return -EIO;
 355                 }
 356                 if (copy_to_user(dst, buf, retval))
 357                         return -EFAULT;
 358                 copied += retval;
 359                 src += retval;
 360                 dst += retval;
 361                 len -= retval;
 362         }
 363         return copied;
 364 }
 365
 366 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 367 {
 368         int copied = 0;
 369
 370         while (len > 0) {
 371                 char buf[128];
 372                 int this_len, retval;
 373
 374                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 375                 if (copy_from_user(buf, src, this_len))
 376                         return -EFAULT;
 377                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 378                 if (!retval) {
 379                         if (copied)
 380                                 break;
 381                         return -EIO;
 382                 }
 383                 copied += retval;
 384                 src += retval;
 385                 dst += retval;
 386                 len -= retval;
 387         }
 388         return copied;
 389 }
 390
 391 static int ptrace_setoptions(struct task_struct *child, long data)
 392 {
 393         child->ptrace &= ~PT_TRACE_MASK;
 394
 395         if (data & PTRACE_O_TRACESYSGOOD)
 396                 child->ptrace |= PT_TRACESYSGOOD;
 397
 398         if (data & PTRACE_O_TRACEFORK)
 399                 child->ptrace |= PT_TRACE_FORK;
 400
 401         if (data & PTRACE_O_TRACEVFORK)
 402                 child->ptrace |= PT_TRACE_VFORK;
 403
 404         if (data & PTRACE_O_TRACECLONE)
 405                 child->ptrace |= PT_TRACE_CLONE;
 406
 407         if (data & PTRACE_O_TRACEEXEC)
 408                 child->ptrace |= PT_TRACE_EXEC;
 409
 410         if (data & PTRACE_O_TRACEVFORKDONE)
 411                 child->ptrace |= PT_TRACE_VFORK_DONE;
 412
 413         if (data & PTRACE_O_TRACEEXIT)
 414                 child->ptrace |= PT_TRACE_EXIT;
 415
 416         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 417 }
 418
 419 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 420 {
 421         int error = -ESRCH;
 422
 423         read_lock(&tasklist_lock);
 424         if (likely(child->sighand != NULL)) {
 425                 error = -EINVAL;
 426                 spin_lock_irq(&child->sighand->siglock);
 427                 if (likely(child->last_siginfo != NULL)) {
 428                         *info = *child->last_siginfo;
 429                         error = 0;
 430                 }
 431                 spin_unlock_irq(&child->sighand->siglock);
 432         }
 433         read_unlock(&tasklist_lock);
 434         return error;
 435 }
 436
 437 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 438 {
 439         int error = -ESRCH;
 440
 441         read_lock(&tasklist_lock);
 442         if (likely(child->sighand != NULL)) {
 443                 error = -EINVAL;
 444                 spin_lock_irq(&child->sighand->siglock);
 445                 if (likely(child->last_siginfo != NULL)) {
 446                         *child->last_siginfo = *info;
 447                         error = 0;
 448                 }
 449                 spin_unlock_irq(&child->sighand->siglock);
 450         }
 451         read_unlock(&tasklist_lock);
 452         return error;
 453 }
 454
 455
 456 #ifdef PTRACE_SINGLESTEP
 457 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 458 #else
 459 #define is_singlestep(request)          0
 460 #endif
 461
 462 #ifdef PTRACE_SINGLEBLOCK
 463 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 464 #else
 465 #define is_singleblock(request)         0
 466 #endif
 467
 468 #ifdef PTRACE_SYSEMU
 469 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 470 #else
 471 #define is_sysemu_singlestep(request)   0
 472 #endif
 473
 474 static int ptrace_resume(struct task_struct *child, long request, long data)
 475 {
 476         if (!valid_signal(data))
 477                 return -EIO;
 478
 479         if (request == PTRACE_SYSCALL)
 480                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 481         else
 482                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 483
 484 #ifdef TIF_SYSCALL_EMU
 485         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 486                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 487         else
 488                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 489 #endif
 490
 491         if (is_singleblock(request)) {
 492                 if (unlikely(!arch_has_block_step()))
 493                         return -EIO;
 494                 user_enable_block_step(child);
 495         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 496                 if (unlikely(!arch_has_single_step()))
 497                         return -EIO;
 498                 user_enable_single_step(child);
 499         } else {
 500                 user_disable_single_step(child);
 501         }
 502
 503         child->exit_code = data;
 504         wake_up_process(child);
 505
 506         return 0;
 507 }
 508
 509 int ptrace_request(struct task_struct *child, long request,
 510                    long addr, long data)
 511 {
 512         int ret = -EIO;
 513         siginfo_t siginfo;
 514
 515         switch (request) {
 516         case PTRACE_PEEKTEXT:
 517         case PTRACE_PEEKDATA:
 518                 return generic_ptrace_peekdata(child, addr, data);
 519         case PTRACE_POKETEXT:
 520         case PTRACE_POKEDATA:
 521                 return generic_ptrace_pokedata(child, addr, data);
 522
 523 #ifdef PTRACE_OLDSETOPTIONS
 524         case PTRACE_OLDSETOPTIONS:
 525 #endif
 526         case PTRACE_SETOPTIONS:
 527                 ret = ptrace_setoptions(child, data);
 528                 break;
 529         case PTRACE_GETEVENTMSG:
 530                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 531                 break;
 532
 533         case PTRACE_GETSIGINFO:
 534                 ret = ptrace_getsiginfo(child, &siginfo);
 535                 if (!ret)
 536                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 537                                                    &siginfo);
 538                 break;
 539
 540         case PTRACE_SETSIGINFO:
 541                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 542                                    sizeof siginfo))
 543                         ret = -EFAULT;
 544                 else
 545                         ret = ptrace_setsiginfo(child, &siginfo);
 546                 break;
 547
 548         case PTRACE_DETACH:      /* detach a process that was attached. */
 549                 ret = ptrace_detach(child, data);
 550                 break;
 551
 552 #ifdef PTRACE_SINGLESTEP
 553         case PTRACE_SINGLESTEP:
 554 #endif
 555 #ifdef PTRACE_SINGLEBLOCK
 556         case PTRACE_SINGLEBLOCK:
 557 #endif
 558 #ifdef PTRACE_SYSEMU
 559         case PTRACE_SYSEMU:
 560         case PTRACE_SYSEMU_SINGLESTEP:
 561 #endif
 562         case PTRACE_SYSCALL:
 563         case PTRACE_CONT:
 564                 return ptrace_resume(child, request, data);
 565
 566         case PTRACE_KILL:
 567                 if (child->exit_state)  /* already dead */
 568                         return 0;
 569                 return ptrace_resume(child, request, SIGKILL);
 570
 571         default:
 572                 break;
 573         }
 574
 575         return ret;
 576 }
 577
 578 /**
 579  * ptrace_traceme  --  helper for PTRACE_TRACEME
 580  *
 581  * Performs checks and sets PT_PTRACED.
 582  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 583  */
 584 int ptrace_traceme(void)
 585 {
 586         int ret = -EPERM;
 587
 588         /*
 589          * Are we already being traced?
 590          */
 591 repeat:
 592         task_lock(current);
 593         if (!(current->ptrace & PT_PTRACED)) {
 594                 /*
 595                  * See ptrace_attach() comments about the locking here.
 596                  */
 597                 unsigned long flags;
 598                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 599                         task_unlock(current);
 600                         do {
 601                                 cpu_relax();
 602                         } while (!write_can_lock(&tasklist_lock));
 603                         goto repeat;
 604                 }
 605
 606                 ret = security_ptrace_traceme(current->parent);
 607
 608                 /*
 609                  * Check PF_EXITING to ensure ->real_parent has not passed
 610                  * exit_ptrace(). Otherwise we don't report the error but
 611                  * pretend ->real_parent untraces us right after return.
 612                  */
 613                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 614                         current->ptrace |= PT_PTRACED;
 615                         __ptrace_link(current, current->real_parent);
 616                 }
 617
 618                 write_unlock_irqrestore(&tasklist_lock, flags);
 619         }
 620         task_unlock(current);
 621         return ret;
 622 }
 623
 624 /**
 625  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 626  * @pid:       process id to grab a task_struct reference of
 627  *
 628  * This function is a helper for ptrace implementations.  It checks
 629  * permissions and then grabs a task struct for use of the actual
 630  * ptrace implementation.
 631  *
 632  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 633  */
 634 struct task_struct *ptrace_get_task_struct(pid_t pid)
 635 {
 636         struct task_struct *child;
 637
 638         read_lock(&tasklist_lock);
 639         child = find_task_by_vpid(pid);
 640         if (child)
 641                 get_task_struct(child);
 642
 643         read_unlock(&tasklist_lock);
 644         if (!child)
 645                 return ERR_PTR(-ESRCH);
 646         return child;
 647 }
 648
 649 #ifndef arch_ptrace_attach
 650 #define arch_ptrace_attach(child)       do { } while (0)
 651 #endif
 652
 653 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 654 {
 655         struct task_struct *child;
 656         long ret;
 657
 658         /*
 659          * This lock_kernel fixes a subtle race with suid exec
 660          */
 661         lock_kernel();
 662         if (request == PTRACE_TRACEME) {
 663                 ret = ptrace_traceme();
 664                 if (!ret)
 665                         arch_ptrace_attach(current);
 666                 goto out;
 667         }
 668
 669         child = ptrace_get_task_struct(pid);
 670         if (IS_ERR(child)) {
 671                 ret = PTR_ERR(child);
 672                 goto out;
 673         }
 674
 675         if (request == PTRACE_ATTACH) {
 676                 ret = ptrace_attach(child);
 677                 /*
 678                  * Some architectures need to do book-keeping after
 679                  * a ptrace attach.
 680                  */
 681                 if (!ret)
 682                         arch_ptrace_attach(child);
 683                 goto out_put_task_struct;
 684         }
 685
 686         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 687         if (ret < 0)
 688                 goto out_put_task_struct;
 689
 690         ret = arch_ptrace(child, request, addr, data);
 691
 692  out_put_task_struct:
 693         put_task_struct(child);
 694  out:
 695         unlock_kernel();
 696         return ret;
 697 }
 698
 699 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 700 {
 701         unsigned long tmp;
 702         int copied;
 703
 704         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 705         if (copied != sizeof(tmp))
 706                 return -EIO;
 707         return put_user(tmp, (unsigned long __user *)data);
 708 }
 709
 710 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 711 {
 712         int copied;
 713
 714         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 715         return (copied == sizeof(data)) ? 0 : -EIO;
 716 }
 717
 718 #if defined CONFIG_COMPAT
 719 #include <linux/compat.h>
 720
 721 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 722                           compat_ulong_t addr, compat_ulong_t data)
 723 {
 724         compat_ulong_t __user *datap = compat_ptr(data);
 725         compat_ulong_t word;
 726         siginfo_t siginfo;
 727         int ret;
 728
 729         switch (request) {
 730         case PTRACE_PEEKTEXT:
 731         case PTRACE_PEEKDATA:
 732                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 733                 if (ret != sizeof(word))
 734                         ret = -EIO;
 735                 else
 736                         ret = put_user(word, datap);
 737                 break;
 738
 739         case PTRACE_POKETEXT:
 740         case PTRACE_POKEDATA:
 741                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 742                 ret = (ret != sizeof(data) ? -EIO : 0);
 743                 break;
 744
 745         case PTRACE_GETEVENTMSG:
 746                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 747                 break;
 748
 749         case PTRACE_GETSIGINFO:
 750                 ret = ptrace_getsiginfo(child, &siginfo);
 751                 if (!ret)
 752                         ret = copy_siginfo_to_user32(
 753                                 (struct compat_siginfo __user *) datap,
 754                                 &siginfo);
 755                 break;
 756
 757         case PTRACE_SETSIGINFO:
 758                 memset(&siginfo, 0, sizeof siginfo);
 759                 if (copy_siginfo_from_user32(
 760                             &siginfo, (struct compat_siginfo __user *) datap))
 761                         ret = -EFAULT;
 762                 else
 763                         ret = ptrace_setsiginfo(child, &siginfo);
 764                 break;
 765
 766         default:
 767                 ret = ptrace_request(child, request, addr, data);
 768         }
 769
 770         return ret;
 771 }
 772
 773 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 774                                   compat_long_t addr, compat_long_t data)
 775 {
 776         struct task_struct *child;
 777         long ret;
 778
 779         /*
 780          * This lock_kernel fixes a subtle race with suid exec
 781          */
 782         lock_kernel();
 783         if (request == PTRACE_TRACEME) {
 784                 ret = ptrace_traceme();
 785                 goto out;
 786         }
 787
 788         child = ptrace_get_task_struct(pid);
 789         if (IS_ERR(child)) {
 790                 ret = PTR_ERR(child);
 791                 goto out;
 792         }
 793
 794         if (request == PTRACE_ATTACH) {
 795                 ret = ptrace_attach(child);
 796                 /*
 797                  * Some architectures need to do book-keeping after
 798                  * a ptrace attach.
 799                  */
 800                 if (!ret)
 801                         arch_ptrace_attach(child);
 802                 goto out_put_task_struct;
 803         }
 804
 805         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 806         if (!ret)
 807                 ret = compat_arch_ptrace(child, request, addr, data);
 808
 809  out_put_task_struct:
 810         put_task_struct(child);
 811  out:
 812         unlock_kernel();
 813         return ret;
 814 }
 815 #endif  /* CONFIG_COMPAT */