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