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