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   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                 if (!child->exit_state)
 309                         wake_up_process(child);
 310         }
 311         write_unlock_irq(&tasklist_lock);
 312
 313         if (unlikely(dead))
 314                 release_task(child);
 315
 316         return 0;
 317 }
 318
 319 /*
 320  * Detach all tasks we were using ptrace on.
 321  */
 322 void exit_ptrace(struct task_struct *tracer)
 323 {
 324         struct task_struct *p, *n;
 325         LIST_HEAD(ptrace_dead);
 326
 327         write_lock_irq(&tasklist_lock);
 328         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 329                 if (__ptrace_detach(tracer, p))
 330                         list_add(&p->ptrace_entry, &ptrace_dead);
 331         }
 332         write_unlock_irq(&tasklist_lock);
 333
 334         BUG_ON(!list_empty(&tracer->ptraced));
 335
 336         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 337                 list_del_init(&p->ptrace_entry);
 338                 release_task(p);
 339         }
 340 }
 341
 342 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 343 {
 344         int copied = 0;
 345
 346         while (len > 0) {
 347                 char buf[128];
 348                 int this_len, retval;
 349
 350                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 351                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 352                 if (!retval) {
 353                         if (copied)
 354                                 break;
 355                         return -EIO;
 356                 }
 357                 if (copy_to_user(dst, buf, retval))
 358                         return -EFAULT;
 359                 copied += retval;
 360                 src += retval;
 361                 dst += retval;
 362                 len -= retval;
 363         }
 364         return copied;
 365 }
 366
 367 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 368 {
 369         int copied = 0;
 370
 371         while (len > 0) {
 372                 char buf[128];
 373                 int this_len, retval;
 374
 375                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 376                 if (copy_from_user(buf, src, this_len))
 377                         return -EFAULT;
 378                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 379                 if (!retval) {
 380                         if (copied)
 381                                 break;
 382                         return -EIO;
 383                 }
 384                 copied += retval;
 385                 src += retval;
 386                 dst += retval;
 387                 len -= retval;
 388         }
 389         return copied;
 390 }
 391
 392 static int ptrace_setoptions(struct task_struct *child, long data)
 393 {
 394         child->ptrace &= ~PT_TRACE_MASK;
 395
 396         if (data & PTRACE_O_TRACESYSGOOD)
 397                 child->ptrace |= PT_TRACESYSGOOD;
 398
 399         if (data & PTRACE_O_TRACEFORK)
 400                 child->ptrace |= PT_TRACE_FORK;
 401
 402         if (data & PTRACE_O_TRACEVFORK)
 403                 child->ptrace |= PT_TRACE_VFORK;
 404
 405         if (data & PTRACE_O_TRACECLONE)
 406                 child->ptrace |= PT_TRACE_CLONE;
 407
 408         if (data & PTRACE_O_TRACEEXEC)
 409                 child->ptrace |= PT_TRACE_EXEC;
 410
 411         if (data & PTRACE_O_TRACEVFORKDONE)
 412                 child->ptrace |= PT_TRACE_VFORK_DONE;
 413
 414         if (data & PTRACE_O_TRACEEXIT)
 415                 child->ptrace |= PT_TRACE_EXIT;
 416
 417         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 418 }
 419
 420 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 421 {
 422         int error = -ESRCH;
 423
 424         read_lock(&tasklist_lock);
 425         if (likely(child->sighand != NULL)) {
 426                 error = -EINVAL;
 427                 spin_lock_irq(&child->sighand->siglock);
 428                 if (likely(child->last_siginfo != NULL)) {
 429                         *info = *child->last_siginfo;
 430                         error = 0;
 431                 }
 432                 spin_unlock_irq(&child->sighand->siglock);
 433         }
 434         read_unlock(&tasklist_lock);
 435         return error;
 436 }
 437
 438 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 439 {
 440         int error = -ESRCH;
 441
 442         read_lock(&tasklist_lock);
 443         if (likely(child->sighand != NULL)) {
 444                 error = -EINVAL;
 445                 spin_lock_irq(&child->sighand->siglock);
 446                 if (likely(child->last_siginfo != NULL)) {
 447                         *child->last_siginfo = *info;
 448                         error = 0;
 449                 }
 450                 spin_unlock_irq(&child->sighand->siglock);
 451         }
 452         read_unlock(&tasklist_lock);
 453         return error;
 454 }
 455
 456
 457 #ifdef PTRACE_SINGLESTEP
 458 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 459 #else
 460 #define is_singlestep(request)          0
 461 #endif
 462
 463 #ifdef PTRACE_SINGLEBLOCK
 464 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 465 #else
 466 #define is_singleblock(request)         0
 467 #endif
 468
 469 #ifdef PTRACE_SYSEMU
 470 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 471 #else
 472 #define is_sysemu_singlestep(request)   0
 473 #endif
 474
 475 static int ptrace_resume(struct task_struct *child, long request, long data)
 476 {
 477         if (!valid_signal(data))
 478                 return -EIO;
 479
 480         if (request == PTRACE_SYSCALL)
 481                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 482         else
 483                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 484
 485 #ifdef TIF_SYSCALL_EMU
 486         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 487                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 488         else
 489                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 490 #endif
 491
 492         if (is_singleblock(request)) {
 493                 if (unlikely(!arch_has_block_step()))
 494                         return -EIO;
 495                 user_enable_block_step(child);
 496         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 497                 if (unlikely(!arch_has_single_step()))
 498                         return -EIO;
 499                 user_enable_single_step(child);
 500         } else {
 501                 user_disable_single_step(child);
 502         }
 503
 504         child->exit_code = data;
 505         wake_up_process(child);
 506
 507         return 0;
 508 }
 509
 510 int ptrace_request(struct task_struct *child, long request,
 511                    long addr, long data)
 512 {
 513         int ret = -EIO;
 514         siginfo_t siginfo;
 515
 516         switch (request) {
 517         case PTRACE_PEEKTEXT:
 518         case PTRACE_PEEKDATA:
 519                 return generic_ptrace_peekdata(child, addr, data);
 520         case PTRACE_POKETEXT:
 521         case PTRACE_POKEDATA:
 522                 return generic_ptrace_pokedata(child, addr, data);
 523
 524 #ifdef PTRACE_OLDSETOPTIONS
 525         case PTRACE_OLDSETOPTIONS:
 526 #endif
 527         case PTRACE_SETOPTIONS:
 528                 ret = ptrace_setoptions(child, data);
 529                 break;
 530         case PTRACE_GETEVENTMSG:
 531                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 532                 break;
 533
 534         case PTRACE_GETSIGINFO:
 535                 ret = ptrace_getsiginfo(child, &siginfo);
 536                 if (!ret)
 537                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 538                                                    &siginfo);
 539                 break;
 540
 541         case PTRACE_SETSIGINFO:
 542                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 543                                    sizeof siginfo))
 544                         ret = -EFAULT;
 545                 else
 546                         ret = ptrace_setsiginfo(child, &siginfo);
 547                 break;
 548
 549         case PTRACE_DETACH:      /* detach a process that was attached. */
 550                 ret = ptrace_detach(child, data);
 551                 break;
 552
 553 #ifdef PTRACE_SINGLESTEP
 554         case PTRACE_SINGLESTEP:
 555 #endif
 556 #ifdef PTRACE_SINGLEBLOCK
 557         case PTRACE_SINGLEBLOCK:
 558 #endif
 559 #ifdef PTRACE_SYSEMU
 560         case PTRACE_SYSEMU:
 561         case PTRACE_SYSEMU_SINGLESTEP:
 562 #endif
 563         case PTRACE_SYSCALL:
 564         case PTRACE_CONT:
 565                 return ptrace_resume(child, request, data);
 566
 567         case PTRACE_KILL:
 568                 if (child->exit_state)  /* already dead */
 569                         return 0;
 570                 return ptrace_resume(child, request, SIGKILL);
 571
 572         default:
 573                 break;
 574         }
 575
 576         return ret;
 577 }
 578
 579 /**
 580  * ptrace_traceme  --  helper for PTRACE_TRACEME
 581  *
 582  * Performs checks and sets PT_PTRACED.
 583  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 584  */
 585 int ptrace_traceme(void)
 586 {
 587         int ret = -EPERM;
 588
 589         /*
 590          * Are we already being traced?
 591          */
 592 repeat:
 593         task_lock(current);
 594         if (!(current->ptrace & PT_PTRACED)) {
 595                 /*
 596                  * See ptrace_attach() comments about the locking here.
 597                  */
 598                 unsigned long flags;
 599                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 600                         task_unlock(current);
 601                         do {
 602                                 cpu_relax();
 603                         } while (!write_can_lock(&tasklist_lock));
 604                         goto repeat;
 605                 }
 606
 607                 ret = security_ptrace_traceme(current->parent);
 608
 609                 /*
 610                  * Check PF_EXITING to ensure ->real_parent has not passed
 611                  * exit_ptrace(). Otherwise we don't report the error but
 612                  * pretend ->real_parent untraces us right after return.
 613                  */
 614                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 615                         current->ptrace |= PT_PTRACED;
 616                         __ptrace_link(current, current->real_parent);
 617                 }
 618
 619                 write_unlock_irqrestore(&tasklist_lock, flags);
 620         }
 621         task_unlock(current);
 622         return ret;
 623 }
 624
 625 /**
 626  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 627  * @pid:       process id to grab a task_struct reference of
 628  *
 629  * This function is a helper for ptrace implementations.  It checks
 630  * permissions and then grabs a task struct for use of the actual
 631  * ptrace implementation.
 632  *
 633  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 634  */
 635 struct task_struct *ptrace_get_task_struct(pid_t pid)
 636 {
 637         struct task_struct *child;
 638
 639         read_lock(&tasklist_lock);
 640         child = find_task_by_vpid(pid);
 641         if (child)
 642                 get_task_struct(child);
 643
 644         read_unlock(&tasklist_lock);
 645         if (!child)
 646                 return ERR_PTR(-ESRCH);
 647         return child;
 648 }
 649
 650 #ifndef arch_ptrace_attach
 651 #define arch_ptrace_attach(child)       do { } while (0)
 652 #endif
 653
 654 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 655 {
 656         struct task_struct *child;
 657         long ret;
 658
 659         /*
 660          * This lock_kernel fixes a subtle race with suid exec
 661          */
 662         lock_kernel();
 663         if (request == PTRACE_TRACEME) {
 664                 ret = ptrace_traceme();
 665                 if (!ret)
 666                         arch_ptrace_attach(current);
 667                 goto out;
 668         }
 669
 670         child = ptrace_get_task_struct(pid);
 671         if (IS_ERR(child)) {
 672                 ret = PTR_ERR(child);
 673                 goto out;
 674         }
 675
 676         if (request == PTRACE_ATTACH) {
 677                 ret = ptrace_attach(child);
 678                 /*
 679                  * Some architectures need to do book-keeping after
 680                  * a ptrace attach.
 681                  */
 682                 if (!ret)
 683                         arch_ptrace_attach(child);
 684                 goto out_put_task_struct;
 685         }
 686
 687         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 688         if (ret < 0)
 689                 goto out_put_task_struct;
 690
 691         ret = arch_ptrace(child, request, addr, data);
 692
 693  out_put_task_struct:
 694         put_task_struct(child);
 695  out:
 696         unlock_kernel();
 697         return ret;
 698 }
 699
 700 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 701 {
 702         unsigned long tmp;
 703         int copied;
 704
 705         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 706         if (copied != sizeof(tmp))
 707                 return -EIO;
 708         return put_user(tmp, (unsigned long __user *)data);
 709 }
 710
 711 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 712 {
 713         int copied;
 714
 715         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 716         return (copied == sizeof(data)) ? 0 : -EIO;
 717 }
 718
 719 #if defined CONFIG_COMPAT
 720 #include <linux/compat.h>
 721
 722 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 723                           compat_ulong_t addr, compat_ulong_t data)
 724 {
 725         compat_ulong_t __user *datap = compat_ptr(data);
 726         compat_ulong_t word;
 727         siginfo_t siginfo;
 728         int ret;
 729
 730         switch (request) {
 731         case PTRACE_PEEKTEXT:
 732         case PTRACE_PEEKDATA:
 733                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 734                 if (ret != sizeof(word))
 735                         ret = -EIO;
 736                 else
 737                         ret = put_user(word, datap);
 738                 break;
 739
 740         case PTRACE_POKETEXT:
 741         case PTRACE_POKEDATA:
 742                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 743                 ret = (ret != sizeof(data) ? -EIO : 0);
 744                 break;
 745
 746         case PTRACE_GETEVENTMSG:
 747                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 748                 break;
 749
 750         case PTRACE_GETSIGINFO:
 751                 ret = ptrace_getsiginfo(child, &siginfo);
 752                 if (!ret)
 753                         ret = copy_siginfo_to_user32(
 754                                 (struct compat_siginfo __user *) datap,
 755                                 &siginfo);
 756                 break;
 757
 758         case PTRACE_SETSIGINFO:
 759                 memset(&siginfo, 0, sizeof siginfo);
 760                 if (copy_siginfo_from_user32(
 761                             &siginfo, (struct compat_siginfo __user *) datap))
 762                         ret = -EFAULT;
 763                 else
 764                         ret = ptrace_setsiginfo(child, &siginfo);
 765                 break;
 766
 767         default:
 768                 ret = ptrace_request(child, request, addr, data);
 769         }
 770
 771         return ret;
 772 }
 773
 774 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 775                                   compat_long_t addr, compat_long_t data)
 776 {
 777         struct task_struct *child;
 778         long ret;
 779
 780         /*
 781          * This lock_kernel fixes a subtle race with suid exec
 782          */
 783         lock_kernel();
 784         if (request == PTRACE_TRACEME) {
 785                 ret = ptrace_traceme();
 786                 goto out;
 787         }
 788
 789         child = ptrace_get_task_struct(pid);
 790         if (IS_ERR(child)) {
 791                 ret = PTR_ERR(child);
 792                 goto out;
 793         }
 794
 795         if (request == PTRACE_ATTACH) {
 796                 ret = ptrace_attach(child);
 797                 /*
 798                  * Some architectures need to do book-keeping after
 799                  * a ptrace attach.
 800                  */
 801                 if (!ret)
 802                         arch_ptrace_attach(child);
 803                 goto out_put_task_struct;
 804         }
 805
 806         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 807         if (!ret)
 808                 ret = compat_arch_ptrace(child, request, addr, data);
 809
 810  out_put_task_struct:
 811         put_task_struct(child);
 812  out:
 813         unlock_kernel();
 814         return ret;
 815 }
 816 #endif  /* CONFIG_COMPAT */