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