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
  25 #include <asm/pgtable.h>
  26 #include <asm/uaccess.h>
  27
  28
  29 /*
  30  * Initialize a new task whose father had been ptraced.
  31  *
  32  * Called from copy_process().
  33  */
  34 void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
  35 {
  36         arch_ptrace_fork(child, clone_flags);
  37 }
  38
  39 /*
  40  * ptrace a task: make the debugger its new parent and
  41  * move it to the ptrace list.
  42  *
  43  * Must be called with the tasklist lock write-held.
  44  */
  45 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
  46 {
  47         BUG_ON(!list_empty(&child->ptrace_entry));
  48         list_add(&child->ptrace_entry, &new_parent->ptraced);
  49         child->parent = new_parent;
  50 }
  51
  52 /*
  53  * Turn a tracing stop into a normal stop now, since with no tracer there
  54  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
  55  * signal sent that would resume the child, but didn't because it was in
  56  * TASK_TRACED, resume it now.
  57  * Requires that irqs be disabled.
  58  */
  59 static void ptrace_untrace(struct task_struct *child)
  60 {
  61         spin_lock(&child->sighand->siglock);
  62         if (task_is_traced(child)) {
  63                 /*
  64                  * If the group stop is completed or in progress,
  65                  * this thread was already counted as stopped.
  66                  */
  67                 if (child->signal->flags & SIGNAL_STOP_STOPPED ||
  68                     child->signal->group_stop_count)
  69                         __set_task_state(child, TASK_STOPPED);
  70                 else
  71                         signal_wake_up(child, 1);
  72         }
  73         spin_unlock(&child->sighand->siglock);
  74 }
  75
  76 /*
  77  * unptrace a task: move it back to its original parent and
  78  * remove it from the ptrace list.
  79  *
  80  * Must be called with the tasklist lock write-held.
  81  */
  82 void __ptrace_unlink(struct task_struct *child)
  83 {
  84         BUG_ON(!child->ptrace);
  85
  86         child->ptrace = 0;
  87         child->parent = child->real_parent;
  88         list_del_init(&child->ptrace_entry);
  89
  90         arch_ptrace_untrace(child);
  91         if (task_is_traced(child))
  92                 ptrace_untrace(child);
  93 }
  94
  95 /*
  96  * Check that we have indeed attached to the thing..
  97  */
  98 int ptrace_check_attach(struct task_struct *child, int kill)
  99 {
 100         int ret = -ESRCH;
 101
 102         /*
 103          * We take the read lock around doing both checks to close a
 104          * possible race where someone else was tracing our child and
 105          * detached between these two checks.  After this locked check,
 106          * we are sure that this is our traced child and that can only
 107          * be changed by us so it's not changing right after this.
 108          */
 109         read_lock(&tasklist_lock);
 110         if ((child->ptrace & PT_PTRACED) && child->parent == current) {
 111                 ret = 0;
 112                 /*
 113                  * child->sighand can't be NULL, release_task()
 114                  * does ptrace_unlink() before __exit_signal().
 115                  */
 116                 spin_lock_irq(&child->sighand->siglock);
 117                 if (task_is_stopped(child))
 118                         child->state = TASK_TRACED;
 119                 else if (!task_is_traced(child) && !kill)
 120                         ret = -ESRCH;
 121                 spin_unlock_irq(&child->sighand->siglock);
 122         }
 123         read_unlock(&tasklist_lock);
 124
 125         if (!ret && !kill)
 126                 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
 127
 128         /* All systems go.. */
 129         return ret;
 130 }
 131
 132 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 133 {
 134         const struct cred *cred = current_cred(), *tcred;
 135
 136         /* May we inspect the given task?
 137          * This check is used both for attaching with ptrace
 138          * and for allowing access to sensitive information in /proc.
 139          *
 140          * ptrace_attach denies several cases that /proc allows
 141          * because setting up the necessary parent/child relationship
 142          * or halting the specified task is impossible.
 143          */
 144         int dumpable = 0;
 145         /* Don't let security modules deny introspection */
 146         if (task == current)
 147                 return 0;
 148         rcu_read_lock();
 149         tcred = __task_cred(task);
 150         if ((cred->uid != tcred->euid ||
 151              cred->uid != tcred->suid ||
 152              cred->uid != tcred->uid  ||
 153              cred->gid != tcred->egid ||
 154              cred->gid != tcred->sgid ||
 155              cred->gid != tcred->gid) &&
 156             !capable(CAP_SYS_PTRACE)) {
 157                 rcu_read_unlock();
 158                 return -EPERM;
 159         }
 160         rcu_read_unlock();
 161         smp_rmb();
 162         if (task->mm)
 163                 dumpable = get_dumpable(task->mm);
 164         if (!dumpable && !capable(CAP_SYS_PTRACE))
 165                 return -EPERM;
 166
 167         return security_ptrace_may_access(task, mode);
 168 }
 169
 170 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
 171 {
 172         int err;
 173         task_lock(task);
 174         err = __ptrace_may_access(task, mode);
 175         task_unlock(task);
 176         return (!err ? true : false);
 177 }
 178
 179 int ptrace_attach(struct task_struct *task)
 180 {
 181         int retval;
 182         unsigned long flags;
 183
 184         audit_ptrace(task);
 185
 186         retval = -EPERM;
 187         if (same_thread_group(task, current))
 188                 goto out;
 189
 190         /* Protect exec's credential calculations against our interference;
 191          * SUID, SGID and LSM creds get determined differently under ptrace.
 192          */
 193         retval = mutex_lock_interruptible(&current->cred_exec_mutex);
 194         if (retval  < 0)
 195                 goto out;
 196
 197         retval = -EPERM;
 198 repeat:
 199         /*
 200          * Nasty, nasty.
 201          *
 202          * We want to hold both the task-lock and the
 203          * tasklist_lock for writing at the same time.
 204          * But that's against the rules (tasklist_lock
 205          * is taken for reading by interrupts on other
 206          * cpu's that may have task_lock).
 207          */
 208         task_lock(task);
 209         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 210                 task_unlock(task);
 211                 do {
 212                         cpu_relax();
 213                 } while (!write_can_lock(&tasklist_lock));
 214                 goto repeat;
 215         }
 216
 217         if (!task->mm)
 218                 goto bad;
 219         /* the same process cannot be attached many times */
 220         if (task->ptrace & PT_PTRACED)
 221                 goto bad;
 222         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 223         if (retval)
 224                 goto bad;
 225
 226         /* Go */
 227         task->ptrace |= PT_PTRACED;
 228         if (capable(CAP_SYS_PTRACE))
 229                 task->ptrace |= PT_PTRACE_CAP;
 230
 231         __ptrace_link(task, current);
 232
 233         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 234 bad:
 235         write_unlock_irqrestore(&tasklist_lock, flags);
 236         task_unlock(task);
 237         mutex_unlock(&current->cred_exec_mutex);
 238 out:
 239         return retval;
 240 }
 241
 242 /*
 243  * Called with irqs disabled, returns true if childs should reap themselves.
 244  */
 245 static int ignoring_children(struct sighand_struct *sigh)
 246 {
 247         int ret;
 248         spin_lock(&sigh->siglock);
 249         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 250               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 251         spin_unlock(&sigh->siglock);
 252         return ret;
 253 }
 254
 255 /*
 256  * Called with tasklist_lock held for writing.
 257  * Unlink a traced task, and clean it up if it was a traced zombie.
 258  * Return true if it needs to be reaped with release_task().
 259  * (We can't call release_task() here because we already hold tasklist_lock.)
 260  *
 261  * If it's a zombie, our attachedness prevented normal parent notification
 262  * or self-reaping.  Do notification now if it would have happened earlier.
 263  * If it should reap itself, return true.
 264  *
 265  * If it's our own child, there is no notification to do.
 266  * But if our normal children self-reap, then this child
 267  * was prevented by ptrace and we must reap it now.
 268  */
 269 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 270 {
 271         __ptrace_unlink(p);
 272
 273         if (p->exit_state == EXIT_ZOMBIE) {
 274                 if (!task_detached(p) && thread_group_empty(p)) {
 275                         if (!same_thread_group(p->real_parent, tracer))
 276                                 do_notify_parent(p, p->exit_signal);
 277                         else if (ignoring_children(tracer->sighand))
 278                                 p->exit_signal = -1;
 279                 }
 280                 if (task_detached(p)) {
 281                         /* Mark it as in the process of being reaped. */
 282                         p->exit_state = EXIT_DEAD;
 283                         return true;
 284                 }
 285         }
 286
 287         return false;
 288 }
 289
 290 int ptrace_detach(struct task_struct *child, unsigned int data)
 291 {
 292         bool dead = false;
 293
 294         if (!valid_signal(data))
 295                 return -EIO;
 296
 297         /* Architecture-specific hardware disable .. */
 298         ptrace_disable(child);
 299         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 300
 301         write_lock_irq(&tasklist_lock);
 302         /*
 303          * This child can be already killed. Make sure de_thread() or
 304          * our sub-thread doing do_wait() didn't do release_task() yet.
 305          */
 306         if (child->ptrace) {
 307                 child->exit_code = data;
 308                 dead = __ptrace_detach(current, child);
 309         }
 310         write_unlock_irq(&tasklist_lock);
 311
 312         if (unlikely(dead))
 313                 release_task(child);
 314
 315         return 0;
 316 }
 317
 318 /*
 319  * Detach all tasks we were using ptrace on.
 320  */
 321 void exit_ptrace(struct task_struct *tracer)
 322 {
 323         struct task_struct *p, *n;
 324         LIST_HEAD(ptrace_dead);
 325
 326         write_lock_irq(&tasklist_lock);
 327         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 328                 if (__ptrace_detach(tracer, p))
 329                         list_add(&p->ptrace_entry, &ptrace_dead);
 330         }
 331         write_unlock_irq(&tasklist_lock);
 332
 333         BUG_ON(!list_empty(&tracer->ptraced));
 334
 335         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 336                 list_del_init(&p->ptrace_entry);
 337                 release_task(p);
 338         }
 339 }
 340
 341 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 342 {
 343         int copied = 0;
 344
 345         while (len > 0) {
 346                 char buf[128];
 347                 int this_len, retval;
 348
 349                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 350                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 351                 if (!retval) {
 352                         if (copied)
 353                                 break;
 354                         return -EIO;
 355                 }
 356                 if (copy_to_user(dst, buf, retval))
 357                         return -EFAULT;
 358                 copied += retval;
 359                 src += retval;
 360                 dst += retval;
 361                 len -= retval;
 362         }
 363         return copied;
 364 }
 365
 366 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 367 {
 368         int copied = 0;
 369
 370         while (len > 0) {
 371                 char buf[128];
 372                 int this_len, retval;
 373
 374                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 375                 if (copy_from_user(buf, src, this_len))
 376                         return -EFAULT;
 377                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 378                 if (!retval) {
 379                         if (copied)
 380                                 break;
 381                         return -EIO;
 382                 }
 383                 copied += retval;
 384                 src += retval;
 385                 dst += retval;
 386                 len -= retval;
 387         }
 388         return copied;
 389 }
 390
 391 static int ptrace_setoptions(struct task_struct *child, long data)
 392 {
 393         child->ptrace &= ~PT_TRACE_MASK;
 394
 395         if (data & PTRACE_O_TRACESYSGOOD)
 396                 child->ptrace |= PT_TRACESYSGOOD;
 397
 398         if (data & PTRACE_O_TRACEFORK)
 399                 child->ptrace |= PT_TRACE_FORK;
 400
 401         if (data & PTRACE_O_TRACEVFORK)
 402                 child->ptrace |= PT_TRACE_VFORK;
 403
 404         if (data & PTRACE_O_TRACECLONE)
 405                 child->ptrace |= PT_TRACE_CLONE;
 406
 407         if (data & PTRACE_O_TRACEEXEC)
 408                 child->ptrace |= PT_TRACE_EXEC;
 409
 410         if (data & PTRACE_O_TRACEVFORKDONE)
 411                 child->ptrace |= PT_TRACE_VFORK_DONE;
 412
 413         if (data & PTRACE_O_TRACEEXIT)
 414                 child->ptrace |= PT_TRACE_EXIT;
 415
 416         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 417 }
 418
 419 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 420 {
 421         int error = -ESRCH;
 422
 423         read_lock(&tasklist_lock);
 424         if (likely(child->sighand != NULL)) {
 425                 error = -EINVAL;
 426                 spin_lock_irq(&child->sighand->siglock);
 427                 if (likely(child->last_siginfo != NULL)) {
 428                         *info = *child->last_siginfo;
 429                         error = 0;
 430                 }
 431                 spin_unlock_irq(&child->sighand->siglock);
 432         }
 433         read_unlock(&tasklist_lock);
 434         return error;
 435 }
 436
 437 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 438 {
 439         int error = -ESRCH;
 440
 441         read_lock(&tasklist_lock);
 442         if (likely(child->sighand != NULL)) {
 443                 error = -EINVAL;
 444                 spin_lock_irq(&child->sighand->siglock);
 445                 if (likely(child->last_siginfo != NULL)) {
 446                         *child->last_siginfo = *info;
 447                         error = 0;
 448                 }
 449                 spin_unlock_irq(&child->sighand->siglock);
 450         }
 451         read_unlock(&tasklist_lock);
 452         return error;
 453 }
 454
 455
 456 #ifdef PTRACE_SINGLESTEP
 457 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 458 #else
 459 #define is_singlestep(request)          0
 460 #endif
 461
 462 #ifdef PTRACE_SINGLEBLOCK
 463 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 464 #else
 465 #define is_singleblock(request)         0
 466 #endif
 467
 468 #ifdef PTRACE_SYSEMU
 469 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 470 #else
 471 #define is_sysemu_singlestep(request)   0
 472 #endif
 473
 474 static int ptrace_resume(struct task_struct *child, long request, long data)
 475 {
 476         if (!valid_signal(data))
 477                 return -EIO;
 478
 479         if (request == PTRACE_SYSCALL)
 480                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 481         else
 482                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 483
 484 #ifdef TIF_SYSCALL_EMU
 485         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 486                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 487         else
 488                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 489 #endif
 490
 491         if (is_singleblock(request)) {
 492                 if (unlikely(!arch_has_block_step()))
 493                         return -EIO;
 494                 user_enable_block_step(child);
 495         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 496                 if (unlikely(!arch_has_single_step()))
 497                         return -EIO;
 498                 user_enable_single_step(child);
 499         }
 500         else
 501                 user_disable_single_step(child);
 502
 503         child->exit_code = data;
 504         wake_up_process(child);
 505
 506         return 0;
 507 }
 508
 509 int ptrace_request(struct task_struct *child, long request,
 510                    long addr, long data)
 511 {
 512         int ret = -EIO;
 513         siginfo_t siginfo;
 514
 515         switch (request) {
 516         case PTRACE_PEEKTEXT:
 517         case PTRACE_PEEKDATA:
 518                 return generic_ptrace_peekdata(child, addr, data);
 519         case PTRACE_POKETEXT:
 520         case PTRACE_POKEDATA:
 521                 return generic_ptrace_pokedata(child, addr, data);
 522
 523 #ifdef PTRACE_OLDSETOPTIONS
 524         case PTRACE_OLDSETOPTIONS:
 525 #endif
 526         case PTRACE_SETOPTIONS:
 527                 ret = ptrace_setoptions(child, data);
 528                 break;
 529         case PTRACE_GETEVENTMSG:
 530                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 531                 break;
 532
 533         case PTRACE_GETSIGINFO:
 534                 ret = ptrace_getsiginfo(child, &siginfo);
 535                 if (!ret)
 536                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 537                                                    &siginfo);
 538                 break;
 539
 540         case PTRACE_SETSIGINFO:
 541                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 542                                    sizeof siginfo))
 543                         ret = -EFAULT;
 544                 else
 545                         ret = ptrace_setsiginfo(child, &siginfo);
 546                 break;
 547
 548         case PTRACE_DETACH:      /* detach a process that was attached. */
 549                 ret = ptrace_detach(child, data);
 550                 break;
 551
 552 #ifdef PTRACE_SINGLESTEP
 553         case PTRACE_SINGLESTEP:
 554 #endif
 555 #ifdef PTRACE_SINGLEBLOCK
 556         case PTRACE_SINGLEBLOCK:
 557 #endif
 558 #ifdef PTRACE_SYSEMU
 559         case PTRACE_SYSEMU:
 560         case PTRACE_SYSEMU_SINGLESTEP:
 561 #endif
 562         case PTRACE_SYSCALL:
 563         case PTRACE_CONT:
 564                 return ptrace_resume(child, request, data);
 565
 566         case PTRACE_KILL:
 567                 if (child->exit_state)  /* already dead */
 568                         return 0;
 569                 return ptrace_resume(child, request, SIGKILL);
 570
 571         default:
 572                 break;
 573         }
 574
 575         return ret;
 576 }
 577
 578 /**
 579  * ptrace_traceme  --  helper for PTRACE_TRACEME
 580  *
 581  * Performs checks and sets PT_PTRACED.
 582  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 583  */
 584 int ptrace_traceme(void)
 585 {
 586         int ret = -EPERM;
 587
 588         /*
 589          * Are we already being traced?
 590          */
 591 repeat:
 592         task_lock(current);
 593         if (!(current->ptrace & PT_PTRACED)) {
 594                 /*
 595                  * See ptrace_attach() comments about the locking here.
 596                  */
 597                 unsigned long flags;
 598                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 599                         task_unlock(current);
 600                         do {
 601                                 cpu_relax();
 602                         } while (!write_can_lock(&tasklist_lock));
 603                         goto repeat;
 604                 }
 605
 606                 ret = security_ptrace_traceme(current->parent);
 607
 608                 /*
 609                  * Set the ptrace bit in the process ptrace flags.
 610                  * Then link us on our parent's ptraced list.
 611                  */
 612                 if (!ret) {
 613                         current->ptrace |= PT_PTRACED;
 614                         __ptrace_link(current, current->real_parent);
 615                 }
 616
 617                 write_unlock_irqrestore(&tasklist_lock, flags);
 618         }
 619         task_unlock(current);
 620         return ret;
 621 }
 622
 623 /**
 624  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 625  * @pid:       process id to grab a task_struct reference of
 626  *
 627  * This function is a helper for ptrace implementations.  It checks
 628  * permissions and then grabs a task struct for use of the actual
 629  * ptrace implementation.
 630  *
 631  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 632  */
 633 struct task_struct *ptrace_get_task_struct(pid_t pid)
 634 {
 635         struct task_struct *child;
 636
 637         read_lock(&tasklist_lock);
 638         child = find_task_by_vpid(pid);
 639         if (child)
 640                 get_task_struct(child);
 641
 642         read_unlock(&tasklist_lock);
 643         if (!child)
 644                 return ERR_PTR(-ESRCH);
 645         return child;
 646 }
 647
 648 #ifndef arch_ptrace_attach
 649 #define arch_ptrace_attach(child)       do { } while (0)
 650 #endif
 651
 652 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 653 {
 654         struct task_struct *child;
 655         long ret;
 656
 657         /*
 658          * This lock_kernel fixes a subtle race with suid exec
 659          */
 660         lock_kernel();
 661         if (request == PTRACE_TRACEME) {
 662                 ret = ptrace_traceme();
 663                 if (!ret)
 664                         arch_ptrace_attach(current);
 665                 goto out;
 666         }
 667
 668         child = ptrace_get_task_struct(pid);
 669         if (IS_ERR(child)) {
 670                 ret = PTR_ERR(child);
 671                 goto out;
 672         }
 673
 674         if (request == PTRACE_ATTACH) {
 675                 ret = ptrace_attach(child);
 676                 /*
 677                  * Some architectures need to do book-keeping after
 678                  * a ptrace attach.
 679                  */
 680                 if (!ret)
 681                         arch_ptrace_attach(child);
 682                 goto out_put_task_struct;
 683         }
 684
 685         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 686         if (ret < 0)
 687                 goto out_put_task_struct;
 688
 689         ret = arch_ptrace(child, request, addr, data);
 690
 691  out_put_task_struct:
 692         put_task_struct(child);
 693  out:
 694         unlock_kernel();
 695         return ret;
 696 }
 697
 698 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 699 {
 700         unsigned long tmp;
 701         int copied;
 702
 703         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 704         if (copied != sizeof(tmp))
 705                 return -EIO;
 706         return put_user(tmp, (unsigned long __user *)data);
 707 }
 708
 709 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 710 {
 711         int copied;
 712
 713         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 714         return (copied == sizeof(data)) ? 0 : -EIO;
 715 }
 716
 717 #if defined CONFIG_COMPAT
 718 #include <linux/compat.h>
 719
 720 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 721                           compat_ulong_t addr, compat_ulong_t data)
 722 {
 723         compat_ulong_t __user *datap = compat_ptr(data);
 724         compat_ulong_t word;
 725         siginfo_t siginfo;
 726         int ret;
 727
 728         switch (request) {
 729         case PTRACE_PEEKTEXT:
 730         case PTRACE_PEEKDATA:
 731                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 732                 if (ret != sizeof(word))
 733                         ret = -EIO;
 734                 else
 735                         ret = put_user(word, datap);
 736                 break;
 737
 738         case PTRACE_POKETEXT:
 739         case PTRACE_POKEDATA:
 740                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 741                 ret = (ret != sizeof(data) ? -EIO : 0);
 742                 break;
 743
 744         case PTRACE_GETEVENTMSG:
 745                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 746                 break;
 747
 748         case PTRACE_GETSIGINFO:
 749                 ret = ptrace_getsiginfo(child, &siginfo);
 750                 if (!ret)
 751                         ret = copy_siginfo_to_user32(
 752                                 (struct compat_siginfo __user *) datap,
 753                                 &siginfo);
 754                 break;
 755
 756         case PTRACE_SETSIGINFO:
 757                 memset(&siginfo, 0, sizeof siginfo);
 758                 if (copy_siginfo_from_user32(
 759                             &siginfo, (struct compat_siginfo __user *) datap))
 760                         ret = -EFAULT;
 761                 else
 762                         ret = ptrace_setsiginfo(child, &siginfo);
 763                 break;
 764
 765         default:
 766                 ret = ptrace_request(child, request, addr, data);
 767         }
 768
 769         return ret;
 770 }
 771
 772 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 773                                   compat_long_t addr, compat_long_t data)
 774 {
 775         struct task_struct *child;
 776         long ret;
 777
 778         /*
 779          * This lock_kernel fixes a subtle race with suid exec
 780          */
 781         lock_kernel();
 782         if (request == PTRACE_TRACEME) {
 783                 ret = ptrace_traceme();
 784                 goto out;
 785         }
 786
 787         child = ptrace_get_task_struct(pid);
 788         if (IS_ERR(child)) {
 789                 ret = PTR_ERR(child);
 790                 goto out;
 791         }
 792
 793         if (request == PTRACE_ATTACH) {
 794                 ret = ptrace_attach(child);
 795                 /*
 796                  * Some architectures need to do book-keeping after
 797                  * a ptrace attach.
 798                  */
 799                 if (!ret)
 800                         arch_ptrace_attach(child);
 801                 goto out_put_task_struct;
 802         }
 803
 804         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 805         if (!ret)
 806                 ret = compat_arch_ptrace(child, request, addr, data);
 807
 808  out_put_task_struct:
 809         put_task_struct(child);
 810  out:
 811         unlock_kernel();
 812         return ret;
 813 }
 814 #endif  /* CONFIG_COMPAT */