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_access_check(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
 171         audit_ptrace(task);
 172
 173         retval = -EPERM;
 174         if (unlikely(task->flags & PF_KTHREAD))
 175                 goto out;
 176         if (same_thread_group(task, current))
 177                 goto out;
 178
 179         /*
 180          * Protect exec's credential calculations against our interference;
 181          * interference; SUID, SGID and LSM creds get determined differently
 182          * under ptrace.
 183          */
 184         retval = -ERESTARTNOINTR;
 185         if (mutex_lock_interruptible(&task->cred_guard_mutex))
 186                 goto out;
 187
 188         task_lock(task);
 189         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 190         task_unlock(task);
 191         if (retval)
 192                 goto unlock_creds;
 193
 194         write_lock_irq(&tasklist_lock);
 195         retval = -EPERM;
 196         if (unlikely(task->exit_state))
 197                 goto unlock_tasklist;
 198         if (task->ptrace)
 199                 goto unlock_tasklist;
 200
 201         task->ptrace = PT_PTRACED;
 202         if (capable(CAP_SYS_PTRACE))
 203                 task->ptrace |= PT_PTRACE_CAP;
 204
 205         __ptrace_link(task, current);
 206         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 207
 208         retval = 0;
 209 unlock_tasklist:
 210         write_unlock_irq(&tasklist_lock);
 211 unlock_creds:
 212         mutex_unlock(&task->cred_guard_mutex);
 213 out:
 214         return retval;
 215 }
 216
 217 /**
 218  * ptrace_traceme  --  helper for PTRACE_TRACEME
 219  *
 220  * Performs checks and sets PT_PTRACED.
 221  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 222  */
 223 int ptrace_traceme(void)
 224 {
 225         int ret = -EPERM;
 226
 227         write_lock_irq(&tasklist_lock);
 228         /* Are we already being traced? */
 229         if (!current->ptrace) {
 230                 ret = security_ptrace_traceme(current->parent);
 231                 /*
 232                  * Check PF_EXITING to ensure ->real_parent has not passed
 233                  * exit_ptrace(). Otherwise we don't report the error but
 234                  * pretend ->real_parent untraces us right after return.
 235                  */
 236                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 237                         current->ptrace = PT_PTRACED;
 238                         __ptrace_link(current, current->real_parent);
 239                 }
 240         }
 241         write_unlock_irq(&tasklist_lock);
 242
 243         return ret;
 244 }
 245
 246 /*
 247  * Called with irqs disabled, returns true if childs should reap themselves.
 248  */
 249 static int ignoring_children(struct sighand_struct *sigh)
 250 {
 251         int ret;
 252         spin_lock(&sigh->siglock);
 253         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 254               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 255         spin_unlock(&sigh->siglock);
 256         return ret;
 257 }
 258
 259 /*
 260  * Called with tasklist_lock held for writing.
 261  * Unlink a traced task, and clean it up if it was a traced zombie.
 262  * Return true if it needs to be reaped with release_task().
 263  * (We can't call release_task() here because we already hold tasklist_lock.)
 264  *
 265  * If it's a zombie, our attachedness prevented normal parent notification
 266  * or self-reaping.  Do notification now if it would have happened earlier.
 267  * If it should reap itself, return true.
 268  *
 269  * If it's our own child, there is no notification to do. But if our normal
 270  * children self-reap, then this child was prevented by ptrace and we must
 271  * reap it now, in that case we must also wake up sub-threads sleeping in
 272  * do_wait().
 273  */
 274 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 275 {
 276         __ptrace_unlink(p);
 277
 278         if (p->exit_state == EXIT_ZOMBIE) {
 279                 if (!task_detached(p) && thread_group_empty(p)) {
 280                         if (!same_thread_group(p->real_parent, tracer))
 281                                 do_notify_parent(p, p->exit_signal);
 282                         else if (ignoring_children(tracer->sighand)) {
 283                                 __wake_up_parent(p, tracer);
 284                                 p->exit_signal = -1;
 285                         }
 286                 }
 287                 if (task_detached(p)) {
 288                         /* Mark it as in the process of being reaped. */
 289                         p->exit_state = EXIT_DEAD;
 290                         return true;
 291                 }
 292         }
 293
 294         return false;
 295 }
 296
 297 int ptrace_detach(struct task_struct *child, unsigned int data)
 298 {
 299         bool dead = false;
 300
 301         if (!valid_signal(data))
 302                 return -EIO;
 303
 304         /* Architecture-specific hardware disable .. */
 305         ptrace_disable(child);
 306         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 307
 308         write_lock_irq(&tasklist_lock);
 309         /*
 310          * This child can be already killed. Make sure de_thread() or
 311          * our sub-thread doing do_wait() didn't do release_task() yet.
 312          */
 313         if (child->ptrace) {
 314                 child->exit_code = data;
 315                 dead = __ptrace_detach(current, child);
 316                 if (!child->exit_state)
 317                         wake_up_state(child, TASK_TRACED | TASK_STOPPED);
 318         }
 319         write_unlock_irq(&tasklist_lock);
 320
 321         if (unlikely(dead))
 322                 release_task(child);
 323
 324         return 0;
 325 }
 326
 327 /*
 328  * Detach all tasks we were using ptrace on.
 329  */
 330 void exit_ptrace(struct task_struct *tracer)
 331 {
 332         struct task_struct *p, *n;
 333         LIST_HEAD(ptrace_dead);
 334
 335         write_lock_irq(&tasklist_lock);
 336         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 337                 if (__ptrace_detach(tracer, p))
 338                         list_add(&p->ptrace_entry, &ptrace_dead);
 339         }
 340         write_unlock_irq(&tasklist_lock);
 341
 342         BUG_ON(!list_empty(&tracer->ptraced));
 343
 344         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 345                 list_del_init(&p->ptrace_entry);
 346                 release_task(p);
 347         }
 348 }
 349
 350 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 351 {
 352         int copied = 0;
 353
 354         while (len > 0) {
 355                 char buf[128];
 356                 int this_len, retval;
 357
 358                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 359                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 360                 if (!retval) {
 361                         if (copied)
 362                                 break;
 363                         return -EIO;
 364                 }
 365                 if (copy_to_user(dst, buf, retval))
 366                         return -EFAULT;
 367                 copied += retval;
 368                 src += retval;
 369                 dst += retval;
 370                 len -= retval;
 371         }
 372         return copied;
 373 }
 374
 375 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 376 {
 377         int copied = 0;
 378
 379         while (len > 0) {
 380                 char buf[128];
 381                 int this_len, retval;
 382
 383                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 384                 if (copy_from_user(buf, src, this_len))
 385                         return -EFAULT;
 386                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 387                 if (!retval) {
 388                         if (copied)
 389                                 break;
 390                         return -EIO;
 391                 }
 392                 copied += retval;
 393                 src += retval;
 394                 dst += retval;
 395                 len -= retval;
 396         }
 397         return copied;
 398 }
 399
 400 static int ptrace_setoptions(struct task_struct *child, long data)
 401 {
 402         child->ptrace &= ~PT_TRACE_MASK;
 403
 404         if (data & PTRACE_O_TRACESYSGOOD)
 405                 child->ptrace |= PT_TRACESYSGOOD;
 406
 407         if (data & PTRACE_O_TRACEFORK)
 408                 child->ptrace |= PT_TRACE_FORK;
 409
 410         if (data & PTRACE_O_TRACEVFORK)
 411                 child->ptrace |= PT_TRACE_VFORK;
 412
 413         if (data & PTRACE_O_TRACECLONE)
 414                 child->ptrace |= PT_TRACE_CLONE;
 415
 416         if (data & PTRACE_O_TRACEEXEC)
 417                 child->ptrace |= PT_TRACE_EXEC;
 418
 419         if (data & PTRACE_O_TRACEVFORKDONE)
 420                 child->ptrace |= PT_TRACE_VFORK_DONE;
 421
 422         if (data & PTRACE_O_TRACEEXIT)
 423                 child->ptrace |= PT_TRACE_EXIT;
 424
 425         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 426 }
 427
 428 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 429 {
 430         unsigned long flags;
 431         int error = -ESRCH;
 432
 433         if (lock_task_sighand(child, &flags)) {
 434                 error = -EINVAL;
 435                 if (likely(child->last_siginfo != NULL)) {
 436                         *info = *child->last_siginfo;
 437                         error = 0;
 438                 }
 439                 unlock_task_sighand(child, &flags);
 440         }
 441         return error;
 442 }
 443
 444 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 445 {
 446         unsigned long flags;
 447         int error = -ESRCH;
 448
 449         if (lock_task_sighand(child, &flags)) {
 450                 error = -EINVAL;
 451                 if (likely(child->last_siginfo != NULL)) {
 452                         *child->last_siginfo = *info;
 453                         error = 0;
 454                 }
 455                 unlock_task_sighand(child, &flags);
 456         }
 457         return error;
 458 }
 459
 460
 461 #ifdef PTRACE_SINGLESTEP
 462 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 463 #else
 464 #define is_singlestep(request)          0
 465 #endif
 466
 467 #ifdef PTRACE_SINGLEBLOCK
 468 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 469 #else
 470 #define is_singleblock(request)         0
 471 #endif
 472
 473 #ifdef PTRACE_SYSEMU
 474 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 475 #else
 476 #define is_sysemu_singlestep(request)   0
 477 #endif
 478
 479 static int ptrace_resume(struct task_struct *child, long request, long data)
 480 {
 481         if (!valid_signal(data))
 482                 return -EIO;
 483
 484         if (request == PTRACE_SYSCALL)
 485                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 486         else
 487                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 488
 489 #ifdef TIF_SYSCALL_EMU
 490         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 491                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 492         else
 493                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 494 #endif
 495
 496         if (is_singleblock(request)) {
 497                 if (unlikely(!arch_has_block_step()))
 498                         return -EIO;
 499                 user_enable_block_step(child);
 500         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 501                 if (unlikely(!arch_has_single_step()))
 502                         return -EIO;
 503                 user_enable_single_step(child);
 504         } else {
 505                 user_disable_single_step(child);
 506         }
 507
 508         child->exit_code = data;
 509         wake_up_process(child);
 510
 511         return 0;
 512 }
 513
 514 int ptrace_request(struct task_struct *child, long request,
 515                    long addr, long data)
 516 {
 517         int ret = -EIO;
 518         siginfo_t siginfo;
 519
 520         switch (request) {
 521         case PTRACE_PEEKTEXT:
 522         case PTRACE_PEEKDATA:
 523                 return generic_ptrace_peekdata(child, addr, data);
 524         case PTRACE_POKETEXT:
 525         case PTRACE_POKEDATA:
 526                 return generic_ptrace_pokedata(child, addr, data);
 527
 528 #ifdef PTRACE_OLDSETOPTIONS
 529         case PTRACE_OLDSETOPTIONS:
 530 #endif
 531         case PTRACE_SETOPTIONS:
 532                 ret = ptrace_setoptions(child, data);
 533                 break;
 534         case PTRACE_GETEVENTMSG:
 535                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 536                 break;
 537
 538         case PTRACE_GETSIGINFO:
 539                 ret = ptrace_getsiginfo(child, &siginfo);
 540                 if (!ret)
 541                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 542                                                    &siginfo);
 543                 break;
 544
 545         case PTRACE_SETSIGINFO:
 546                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 547                                    sizeof siginfo))
 548                         ret = -EFAULT;
 549                 else
 550                         ret = ptrace_setsiginfo(child, &siginfo);
 551                 break;
 552
 553         case PTRACE_DETACH:      /* detach a process that was attached. */
 554                 ret = ptrace_detach(child, data);
 555                 break;
 556
 557 #ifdef PTRACE_SINGLESTEP
 558         case PTRACE_SINGLESTEP:
 559 #endif
 560 #ifdef PTRACE_SINGLEBLOCK
 561         case PTRACE_SINGLEBLOCK:
 562 #endif
 563 #ifdef PTRACE_SYSEMU
 564         case PTRACE_SYSEMU:
 565         case PTRACE_SYSEMU_SINGLESTEP:
 566 #endif
 567         case PTRACE_SYSCALL:
 568         case PTRACE_CONT:
 569                 return ptrace_resume(child, request, data);
 570
 571         case PTRACE_KILL:
 572                 if (child->exit_state)  /* already dead */
 573                         return 0;
 574                 return ptrace_resume(child, request, SIGKILL);
 575
 576         default:
 577                 break;
 578         }
 579
 580         return ret;
 581 }
 582
 583 static struct task_struct *ptrace_get_task_struct(pid_t pid)
 584 {
 585         struct task_struct *child;
 586
 587         rcu_read_lock();
 588         child = find_task_by_vpid(pid);
 589         if (child)
 590                 get_task_struct(child);
 591         rcu_read_unlock();
 592
 593         if (!child)
 594                 return ERR_PTR(-ESRCH);
 595         return child;
 596 }
 597
 598 #ifndef arch_ptrace_attach
 599 #define arch_ptrace_attach(child)       do { } while (0)
 600 #endif
 601
 602 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 603 {
 604         struct task_struct *child;
 605         long ret;
 606
 607         /*
 608          * This lock_kernel fixes a subtle race with suid exec
 609          */
 610         lock_kernel();
 611         if (request == PTRACE_TRACEME) {
 612                 ret = ptrace_traceme();
 613                 if (!ret)
 614                         arch_ptrace_attach(current);
 615                 goto out;
 616         }
 617
 618         child = ptrace_get_task_struct(pid);
 619         if (IS_ERR(child)) {
 620                 ret = PTR_ERR(child);
 621                 goto out;
 622         }
 623
 624         if (request == PTRACE_ATTACH) {
 625                 ret = ptrace_attach(child);
 626                 /*
 627                  * Some architectures need to do book-keeping after
 628                  * a ptrace attach.
 629                  */
 630                 if (!ret)
 631                         arch_ptrace_attach(child);
 632                 goto out_put_task_struct;
 633         }
 634
 635         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 636         if (ret < 0)
 637                 goto out_put_task_struct;
 638
 639         ret = arch_ptrace(child, request, addr, data);
 640
 641  out_put_task_struct:
 642         put_task_struct(child);
 643  out:
 644         unlock_kernel();
 645         return ret;
 646 }
 647
 648 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 649 {
 650         unsigned long tmp;
 651         int copied;
 652
 653         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 654         if (copied != sizeof(tmp))
 655                 return -EIO;
 656         return put_user(tmp, (unsigned long __user *)data);
 657 }
 658
 659 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 660 {
 661         int copied;
 662
 663         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 664         return (copied == sizeof(data)) ? 0 : -EIO;
 665 }
 666
 667 #if defined CONFIG_COMPAT
 668 #include <linux/compat.h>
 669
 670 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 671                           compat_ulong_t addr, compat_ulong_t data)
 672 {
 673         compat_ulong_t __user *datap = compat_ptr(data);
 674         compat_ulong_t word;
 675         siginfo_t siginfo;
 676         int ret;
 677
 678         switch (request) {
 679         case PTRACE_PEEKTEXT:
 680         case PTRACE_PEEKDATA:
 681                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 682                 if (ret != sizeof(word))
 683                         ret = -EIO;
 684                 else
 685                         ret = put_user(word, datap);
 686                 break;
 687
 688         case PTRACE_POKETEXT:
 689         case PTRACE_POKEDATA:
 690                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 691                 ret = (ret != sizeof(data) ? -EIO : 0);
 692                 break;
 693
 694         case PTRACE_GETEVENTMSG:
 695                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 696                 break;
 697
 698         case PTRACE_GETSIGINFO:
 699                 ret = ptrace_getsiginfo(child, &siginfo);
 700                 if (!ret)
 701                         ret = copy_siginfo_to_user32(
 702                                 (struct compat_siginfo __user *) datap,
 703                                 &siginfo);
 704                 break;
 705
 706         case PTRACE_SETSIGINFO:
 707                 memset(&siginfo, 0, sizeof siginfo);
 708                 if (copy_siginfo_from_user32(
 709                             &siginfo, (struct compat_siginfo __user *) datap))
 710                         ret = -EFAULT;
 711                 else
 712                         ret = ptrace_setsiginfo(child, &siginfo);
 713                 break;
 714
 715         default:
 716                 ret = ptrace_request(child, request, addr, data);
 717         }
 718
 719         return ret;
 720 }
 721
 722 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 723                                   compat_long_t addr, compat_long_t data)
 724 {
 725         struct task_struct *child;
 726         long ret;
 727
 728         /*
 729          * This lock_kernel fixes a subtle race with suid exec
 730          */
 731         lock_kernel();
 732         if (request == PTRACE_TRACEME) {
 733                 ret = ptrace_traceme();
 734                 goto out;
 735         }
 736
 737         child = ptrace_get_task_struct(pid);
 738         if (IS_ERR(child)) {
 739                 ret = PTR_ERR(child);
 740                 goto out;
 741         }
 742
 743         if (request == PTRACE_ATTACH) {
 744                 ret = ptrace_attach(child);
 745                 /*
 746                  * Some architectures need to do book-keeping after
 747                  * a ptrace attach.
 748                  */
 749                 if (!ret)
 750                         arch_ptrace_attach(child);
 751                 goto out_put_task_struct;
 752         }
 753
 754         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 755         if (!ret)
 756                 ret = compat_arch_ptrace(child, request, addr, data);
 757
 758  out_put_task_struct:
 759         put_task_struct(child);
 760  out:
 761         unlock_kernel();
 762         return ret;
 763 }
 764 #endif  /* CONFIG_COMPAT */