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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         /* Protect the target's credential calculations against our
 181          * interference; SUID, SGID and LSM creds get determined differently
 182          * under ptrace.
 183          */
 184         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
 185         if (retval  < 0)
 186                 goto out;
 187 repeat:
 188         /*
 189          * Nasty, nasty.
 190          *
 191          * We want to hold both the task-lock and the
 192          * tasklist_lock for writing at the same time.
 193          * But that's against the rules (tasklist_lock
 194          * is taken for reading by interrupts on other
 195          * cpu's that may have task_lock).
 196          */
 197         task_lock(task);
 198         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 199                 task_unlock(task);
 200                 do {
 201                         cpu_relax();
 202                 } while (!write_can_lock(&tasklist_lock));
 203                 goto repeat;
 204         }
 205
 206         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
 207         if (retval)
 208                 goto bad;
 209
 210         retval = -EPERM;
 211         if (unlikely(task->exit_state))
 212                 goto bad;
 213         if (task->ptrace & PT_PTRACED)
 214                 goto bad;
 215
 216         task->ptrace |= PT_PTRACED;
 217         if (capable(CAP_SYS_PTRACE))
 218                 task->ptrace |= PT_PTRACE_CAP;
 219
 220         __ptrace_link(task, current);
 221         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
 222
 223         retval = 0;
 224 bad:
 225         write_unlock_irqrestore(&tasklist_lock, flags);
 226         task_unlock(task);
 227         mutex_unlock(&task->cred_guard_mutex);
 228 out:
 229         return retval;
 230 }
 231
 232 /*
 233  * Called with irqs disabled, returns true if childs should reap themselves.
 234  */
 235 static int ignoring_children(struct sighand_struct *sigh)
 236 {
 237         int ret;
 238         spin_lock(&sigh->siglock);
 239         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
 240               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
 241         spin_unlock(&sigh->siglock);
 242         return ret;
 243 }
 244
 245 /*
 246  * Called with tasklist_lock held for writing.
 247  * Unlink a traced task, and clean it up if it was a traced zombie.
 248  * Return true if it needs to be reaped with release_task().
 249  * (We can't call release_task() here because we already hold tasklist_lock.)
 250  *
 251  * If it's a zombie, our attachedness prevented normal parent notification
 252  * or self-reaping.  Do notification now if it would have happened earlier.
 253  * If it should reap itself, return true.
 254  *
 255  * If it's our own child, there is no notification to do.
 256  * But if our normal children self-reap, then this child
 257  * was prevented by ptrace and we must reap it now.
 258  */
 259 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 260 {
 261         __ptrace_unlink(p);
 262
 263         if (p->exit_state == EXIT_ZOMBIE) {
 264                 if (!task_detached(p) && thread_group_empty(p)) {
 265                         if (!same_thread_group(p->real_parent, tracer))
 266                                 do_notify_parent(p, p->exit_signal);
 267                         else if (ignoring_children(tracer->sighand))
 268                                 p->exit_signal = -1;
 269                 }
 270                 if (task_detached(p)) {
 271                         /* Mark it as in the process of being reaped. */
 272                         p->exit_state = EXIT_DEAD;
 273                         return true;
 274                 }
 275         }
 276
 277         return false;
 278 }
 279
 280 int ptrace_detach(struct task_struct *child, unsigned int data)
 281 {
 282         bool dead = false;
 283
 284         if (!valid_signal(data))
 285                 return -EIO;
 286
 287         /* Architecture-specific hardware disable .. */
 288         ptrace_disable(child);
 289         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 290
 291         write_lock_irq(&tasklist_lock);
 292         /*
 293          * This child can be already killed. Make sure de_thread() or
 294          * our sub-thread doing do_wait() didn't do release_task() yet.
 295          */
 296         if (child->ptrace) {
 297                 child->exit_code = data;
 298                 dead = __ptrace_detach(current, child);
 299                 if (!child->exit_state)
 300                         wake_up_process(child);
 301         }
 302         write_unlock_irq(&tasklist_lock);
 303
 304         if (unlikely(dead))
 305                 release_task(child);
 306
 307         return 0;
 308 }
 309
 310 /*
 311  * Detach all tasks we were using ptrace on.
 312  */
 313 void exit_ptrace(struct task_struct *tracer)
 314 {
 315         struct task_struct *p, *n;
 316         LIST_HEAD(ptrace_dead);
 317
 318         write_lock_irq(&tasklist_lock);
 319         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 320                 if (__ptrace_detach(tracer, p))
 321                         list_add(&p->ptrace_entry, &ptrace_dead);
 322         }
 323         write_unlock_irq(&tasklist_lock);
 324
 325         BUG_ON(!list_empty(&tracer->ptraced));
 326
 327         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 328                 list_del_init(&p->ptrace_entry);
 329                 release_task(p);
 330         }
 331 }
 332
 333 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 334 {
 335         int copied = 0;
 336
 337         while (len > 0) {
 338                 char buf[128];
 339                 int this_len, retval;
 340
 341                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 342                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 343                 if (!retval) {
 344                         if (copied)
 345                                 break;
 346                         return -EIO;
 347                 }
 348                 if (copy_to_user(dst, buf, retval))
 349                         return -EFAULT;
 350                 copied += retval;
 351                 src += retval;
 352                 dst += retval;
 353                 len -= retval;
 354         }
 355         return copied;
 356 }
 357
 358 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 359 {
 360         int copied = 0;
 361
 362         while (len > 0) {
 363                 char buf[128];
 364                 int this_len, retval;
 365
 366                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 367                 if (copy_from_user(buf, src, this_len))
 368                         return -EFAULT;
 369                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 370                 if (!retval) {
 371                         if (copied)
 372                                 break;
 373                         return -EIO;
 374                 }
 375                 copied += retval;
 376                 src += retval;
 377                 dst += retval;
 378                 len -= retval;
 379         }
 380         return copied;
 381 }
 382
 383 static int ptrace_setoptions(struct task_struct *child, long data)
 384 {
 385         child->ptrace &= ~PT_TRACE_MASK;
 386
 387         if (data & PTRACE_O_TRACESYSGOOD)
 388                 child->ptrace |= PT_TRACESYSGOOD;
 389
 390         if (data & PTRACE_O_TRACEFORK)
 391                 child->ptrace |= PT_TRACE_FORK;
 392
 393         if (data & PTRACE_O_TRACEVFORK)
 394                 child->ptrace |= PT_TRACE_VFORK;
 395
 396         if (data & PTRACE_O_TRACECLONE)
 397                 child->ptrace |= PT_TRACE_CLONE;
 398
 399         if (data & PTRACE_O_TRACEEXEC)
 400                 child->ptrace |= PT_TRACE_EXEC;
 401
 402         if (data & PTRACE_O_TRACEVFORKDONE)
 403                 child->ptrace |= PT_TRACE_VFORK_DONE;
 404
 405         if (data & PTRACE_O_TRACEEXIT)
 406                 child->ptrace |= PT_TRACE_EXIT;
 407
 408         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 409 }
 410
 411 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 412 {
 413         int error = -ESRCH;
 414
 415         read_lock(&tasklist_lock);
 416         if (likely(child->sighand != NULL)) {
 417                 error = -EINVAL;
 418                 spin_lock_irq(&child->sighand->siglock);
 419                 if (likely(child->last_siginfo != NULL)) {
 420                         *info = *child->last_siginfo;
 421                         error = 0;
 422                 }
 423                 spin_unlock_irq(&child->sighand->siglock);
 424         }
 425         read_unlock(&tasklist_lock);
 426         return error;
 427 }
 428
 429 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 430 {
 431         int error = -ESRCH;
 432
 433         read_lock(&tasklist_lock);
 434         if (likely(child->sighand != NULL)) {
 435                 error = -EINVAL;
 436                 spin_lock_irq(&child->sighand->siglock);
 437                 if (likely(child->last_siginfo != NULL)) {
 438                         *child->last_siginfo = *info;
 439                         error = 0;
 440                 }
 441                 spin_unlock_irq(&child->sighand->siglock);
 442         }
 443         read_unlock(&tasklist_lock);
 444         return error;
 445 }
 446
 447
 448 #ifdef PTRACE_SINGLESTEP
 449 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
 450 #else
 451 #define is_singlestep(request)          0
 452 #endif
 453
 454 #ifdef PTRACE_SINGLEBLOCK
 455 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
 456 #else
 457 #define is_singleblock(request)         0
 458 #endif
 459
 460 #ifdef PTRACE_SYSEMU
 461 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
 462 #else
 463 #define is_sysemu_singlestep(request)   0
 464 #endif
 465
 466 static int ptrace_resume(struct task_struct *child, long request, long data)
 467 {
 468         if (!valid_signal(data))
 469                 return -EIO;
 470
 471         if (request == PTRACE_SYSCALL)
 472                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 473         else
 474                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 475
 476 #ifdef TIF_SYSCALL_EMU
 477         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
 478                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 479         else
 480                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 481 #endif
 482
 483         if (is_singleblock(request)) {
 484                 if (unlikely(!arch_has_block_step()))
 485                         return -EIO;
 486                 user_enable_block_step(child);
 487         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
 488                 if (unlikely(!arch_has_single_step()))
 489                         return -EIO;
 490                 user_enable_single_step(child);
 491         } else {
 492                 user_disable_single_step(child);
 493         }
 494
 495         child->exit_code = data;
 496         wake_up_process(child);
 497
 498         return 0;
 499 }
 500
 501 int ptrace_request(struct task_struct *child, long request,
 502                    long addr, long data)
 503 {
 504         int ret = -EIO;
 505         siginfo_t siginfo;
 506
 507         switch (request) {
 508         case PTRACE_PEEKTEXT:
 509         case PTRACE_PEEKDATA:
 510                 return generic_ptrace_peekdata(child, addr, data);
 511         case PTRACE_POKETEXT:
 512         case PTRACE_POKEDATA:
 513                 return generic_ptrace_pokedata(child, addr, data);
 514
 515 #ifdef PTRACE_OLDSETOPTIONS
 516         case PTRACE_OLDSETOPTIONS:
 517 #endif
 518         case PTRACE_SETOPTIONS:
 519                 ret = ptrace_setoptions(child, data);
 520                 break;
 521         case PTRACE_GETEVENTMSG:
 522                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 523                 break;
 524
 525         case PTRACE_GETSIGINFO:
 526                 ret = ptrace_getsiginfo(child, &siginfo);
 527                 if (!ret)
 528                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
 529                                                    &siginfo);
 530                 break;
 531
 532         case PTRACE_SETSIGINFO:
 533                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
 534                                    sizeof siginfo))
 535                         ret = -EFAULT;
 536                 else
 537                         ret = ptrace_setsiginfo(child, &siginfo);
 538                 break;
 539
 540         case PTRACE_DETACH:      /* detach a process that was attached. */
 541                 ret = ptrace_detach(child, data);
 542                 break;
 543
 544 #ifdef PTRACE_SINGLESTEP
 545         case PTRACE_SINGLESTEP:
 546 #endif
 547 #ifdef PTRACE_SINGLEBLOCK
 548         case PTRACE_SINGLEBLOCK:
 549 #endif
 550 #ifdef PTRACE_SYSEMU
 551         case PTRACE_SYSEMU:
 552         case PTRACE_SYSEMU_SINGLESTEP:
 553 #endif
 554         case PTRACE_SYSCALL:
 555         case PTRACE_CONT:
 556                 return ptrace_resume(child, request, data);
 557
 558         case PTRACE_KILL:
 559                 if (child->exit_state)  /* already dead */
 560                         return 0;
 561                 return ptrace_resume(child, request, SIGKILL);
 562
 563         default:
 564                 break;
 565         }
 566
 567         return ret;
 568 }
 569
 570 /**
 571  * ptrace_traceme  --  helper for PTRACE_TRACEME
 572  *
 573  * Performs checks and sets PT_PTRACED.
 574  * Should be used by all ptrace implementations for PTRACE_TRACEME.
 575  */
 576 int ptrace_traceme(void)
 577 {
 578         int ret = -EPERM;
 579
 580         /*
 581          * Are we already being traced?
 582          */
 583 repeat:
 584         task_lock(current);
 585         if (!(current->ptrace & PT_PTRACED)) {
 586                 /*
 587                  * See ptrace_attach() comments about the locking here.
 588                  */
 589                 unsigned long flags;
 590                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
 591                         task_unlock(current);
 592                         do {
 593                                 cpu_relax();
 594                         } while (!write_can_lock(&tasklist_lock));
 595                         goto repeat;
 596                 }
 597
 598                 ret = security_ptrace_traceme(current->parent);
 599
 600                 /*
 601                  * Check PF_EXITING to ensure ->real_parent has not passed
 602                  * exit_ptrace(). Otherwise we don't report the error but
 603                  * pretend ->real_parent untraces us right after return.
 604                  */
 605                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
 606                         current->ptrace |= PT_PTRACED;
 607                         __ptrace_link(current, current->real_parent);
 608                 }
 609
 610                 write_unlock_irqrestore(&tasklist_lock, flags);
 611         }
 612         task_unlock(current);
 613         return ret;
 614 }
 615
 616 /**
 617  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 618  * @pid:       process id to grab a task_struct reference of
 619  *
 620  * This function is a helper for ptrace implementations.  It checks
 621  * permissions and then grabs a task struct for use of the actual
 622  * ptrace implementation.
 623  *
 624  * Returns the task_struct for @pid or an ERR_PTR() on failure.
 625  */
 626 struct task_struct *ptrace_get_task_struct(pid_t pid)
 627 {
 628         struct task_struct *child;
 629
 630         read_lock(&tasklist_lock);
 631         child = find_task_by_vpid(pid);
 632         if (child)
 633                 get_task_struct(child);
 634
 635         read_unlock(&tasklist_lock);
 636         if (!child)
 637                 return ERR_PTR(-ESRCH);
 638         return child;
 639 }
 640
 641 #ifndef arch_ptrace_attach
 642 #define arch_ptrace_attach(child)       do { } while (0)
 643 #endif
 644
 645 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
 646 {
 647         struct task_struct *child;
 648         long ret;
 649
 650         /*
 651          * This lock_kernel fixes a subtle race with suid exec
 652          */
 653         lock_kernel();
 654         if (request == PTRACE_TRACEME) {
 655                 ret = ptrace_traceme();
 656                 if (!ret)
 657                         arch_ptrace_attach(current);
 658                 goto out;
 659         }
 660
 661         child = ptrace_get_task_struct(pid);
 662         if (IS_ERR(child)) {
 663                 ret = PTR_ERR(child);
 664                 goto out;
 665         }
 666
 667         if (request == PTRACE_ATTACH) {
 668                 ret = ptrace_attach(child);
 669                 /*
 670                  * Some architectures need to do book-keeping after
 671                  * a ptrace attach.
 672                  */
 673                 if (!ret)
 674                         arch_ptrace_attach(child);
 675                 goto out_put_task_struct;
 676         }
 677
 678         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 679         if (ret < 0)
 680                 goto out_put_task_struct;
 681
 682         ret = arch_ptrace(child, request, addr, data);
 683
 684  out_put_task_struct:
 685         put_task_struct(child);
 686  out:
 687         unlock_kernel();
 688         return ret;
 689 }
 690
 691 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
 692 {
 693         unsigned long tmp;
 694         int copied;
 695
 696         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
 697         if (copied != sizeof(tmp))
 698                 return -EIO;
 699         return put_user(tmp, (unsigned long __user *)data);
 700 }
 701
 702 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
 703 {
 704         int copied;
 705
 706         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
 707         return (copied == sizeof(data)) ? 0 : -EIO;
 708 }
 709
 710 #if defined CONFIG_COMPAT
 711 #include <linux/compat.h>
 712
 713 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 714                           compat_ulong_t addr, compat_ulong_t data)
 715 {
 716         compat_ulong_t __user *datap = compat_ptr(data);
 717         compat_ulong_t word;
 718         siginfo_t siginfo;
 719         int ret;
 720
 721         switch (request) {
 722         case PTRACE_PEEKTEXT:
 723         case PTRACE_PEEKDATA:
 724                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
 725                 if (ret != sizeof(word))
 726                         ret = -EIO;
 727                 else
 728                         ret = put_user(word, datap);
 729                 break;
 730
 731         case PTRACE_POKETEXT:
 732         case PTRACE_POKEDATA:
 733                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
 734                 ret = (ret != sizeof(data) ? -EIO : 0);
 735                 break;
 736
 737         case PTRACE_GETEVENTMSG:
 738                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 739                 break;
 740
 741         case PTRACE_GETSIGINFO:
 742                 ret = ptrace_getsiginfo(child, &siginfo);
 743                 if (!ret)
 744                         ret = copy_siginfo_to_user32(
 745                                 (struct compat_siginfo __user *) datap,
 746                                 &siginfo);
 747                 break;
 748
 749         case PTRACE_SETSIGINFO:
 750                 memset(&siginfo, 0, sizeof siginfo);
 751                 if (copy_siginfo_from_user32(
 752                             &siginfo, (struct compat_siginfo __user *) datap))
 753                         ret = -EFAULT;
 754                 else
 755                         ret = ptrace_setsiginfo(child, &siginfo);
 756                 break;
 757
 758         default:
 759                 ret = ptrace_request(child, request, addr, data);
 760         }
 761
 762         return ret;
 763 }
 764
 765 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 766                                   compat_long_t addr, compat_long_t data)
 767 {
 768         struct task_struct *child;
 769         long ret;
 770
 771         /*
 772          * This lock_kernel fixes a subtle race with suid exec
 773          */
 774         lock_kernel();
 775         if (request == PTRACE_TRACEME) {
 776                 ret = ptrace_traceme();
 777                 goto out;
 778         }
 779
 780         child = ptrace_get_task_struct(pid);
 781         if (IS_ERR(child)) {
 782                 ret = PTR_ERR(child);
 783                 goto out;
 784         }
 785
 786         if (request == PTRACE_ATTACH) {
 787                 ret = ptrace_attach(child);
 788                 /*
 789                  * Some architectures need to do book-keeping after
 790                  * a ptrace attach.
 791                  */
 792                 if (!ret)
 793                         arch_ptrace_attach(child);
 794                 goto out_put_task_struct;
 795         }
 796
 797         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 798         if (!ret)
 799                 ret = compat_arch_ptrace(child, request, addr, data);
 800
 801  out_put_task_struct:
 802         put_task_struct(child);
 803  out:
 804         unlock_kernel();
 805         return ret;
 806 }
 807 #endif  /* CONFIG_COMPAT */