Merge branch 'master' into next
[linux-2.6.git] / 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  * Initialize a new task whose father had been ptraced.
29  *
30  * Called from copy_process().
31  */
32 void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
33 {
34         arch_ptrace_fork(child, clone_flags);
35 }
36
37 /*
38  * ptrace a task: make the debugger its new parent and
39  * move it to the ptrace list.
40  *
41  * Must be called with the tasklist lock write-held.
42  */
43 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
44 {
45         BUG_ON(!list_empty(&child->ptrace_entry));
46         list_add(&child->ptrace_entry, &new_parent->ptraced);
47         child->parent = new_parent;
48 }
49
50 /*
51  * Turn a tracing stop into a normal stop now, since with no tracer there
52  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
53  * signal sent that would resume the child, but didn't because it was in
54  * TASK_TRACED, resume it now.
55  * Requires that irqs be disabled.
56  */
57 static void ptrace_untrace(struct task_struct *child)
58 {
59         spin_lock(&child->sighand->siglock);
60         if (task_is_traced(child)) {
61                 /*
62                  * If the group stop is completed or in progress,
63                  * this thread was already counted as stopped.
64                  */
65                 if (child->signal->flags & SIGNAL_STOP_STOPPED ||
66                     child->signal->group_stop_count)
67                         __set_task_state(child, TASK_STOPPED);
68                 else
69                         signal_wake_up(child, 1);
70         }
71         spin_unlock(&child->sighand->siglock);
72 }
73
74 /*
75  * unptrace a task: move it back to its original parent and
76  * remove it from the ptrace list.
77  *
78  * Must be called with the tasklist lock write-held.
79  */
80 void __ptrace_unlink(struct task_struct *child)
81 {
82         BUG_ON(!child->ptrace);
83
84         child->ptrace = 0;
85         child->parent = child->real_parent;
86         list_del_init(&child->ptrace_entry);
87
88         arch_ptrace_untrace(child);
89         if (task_is_traced(child))
90                 ptrace_untrace(child);
91 }
92
93 /*
94  * Check that we have indeed attached to the thing..
95  */
96 int ptrace_check_attach(struct task_struct *child, int kill)
97 {
98         int ret = -ESRCH;
99
100         /*
101          * We take the read lock around doing both checks to close a
102          * possible race where someone else was tracing our child and
103          * detached between these two checks.  After this locked check,
104          * we are sure that this is our traced child and that can only
105          * be changed by us so it's not changing right after this.
106          */
107         read_lock(&tasklist_lock);
108         if ((child->ptrace & PT_PTRACED) && child->parent == current) {
109                 ret = 0;
110                 /*
111                  * child->sighand can't be NULL, release_task()
112                  * does ptrace_unlink() before __exit_signal().
113                  */
114                 spin_lock_irq(&child->sighand->siglock);
115                 if (task_is_stopped(child))
116                         child->state = TASK_TRACED;
117                 else if (!task_is_traced(child) && !kill)
118                         ret = -ESRCH;
119                 spin_unlock_irq(&child->sighand->siglock);
120         }
121         read_unlock(&tasklist_lock);
122
123         if (!ret && !kill)
124                 ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
125
126         /* All systems go.. */
127         return ret;
128 }
129
130 int __ptrace_may_access(struct task_struct *task, unsigned int mode)
131 {
132         const struct cred *cred = current_cred(), *tcred;
133
134         /* May we inspect the given task?
135          * This check is used both for attaching with ptrace
136          * and for allowing access to sensitive information in /proc.
137          *
138          * ptrace_attach denies several cases that /proc allows
139          * because setting up the necessary parent/child relationship
140          * or halting the specified task is impossible.
141          */
142         int dumpable = 0;
143         /* Don't let security modules deny introspection */
144         if (task == current)
145                 return 0;
146         rcu_read_lock();
147         tcred = __task_cred(task);
148         if ((cred->uid != tcred->euid ||
149              cred->uid != tcred->suid ||
150              cred->uid != tcred->uid  ||
151              cred->gid != tcred->egid ||
152              cred->gid != tcred->sgid ||
153              cred->gid != tcred->gid) &&
154             !capable(CAP_SYS_PTRACE)) {
155                 rcu_read_unlock();
156                 return -EPERM;
157         }
158         rcu_read_unlock();
159         smp_rmb();
160         if (task->mm)
161                 dumpable = get_dumpable(task->mm);
162         if (!dumpable && !capable(CAP_SYS_PTRACE))
163                 return -EPERM;
164
165         return security_ptrace_may_access(task, mode);
166 }
167
168 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
169 {
170         int err;
171         task_lock(task);
172         err = __ptrace_may_access(task, mode);
173         task_unlock(task);
174         return !err;
175 }
176
177 int ptrace_attach(struct task_struct *task)
178 {
179         int retval;
180         unsigned long flags;
181
182         audit_ptrace(task);
183
184         retval = -EPERM;
185         if (same_thread_group(task, current))
186                 goto out;
187
188         /* Protect the target's credential calculations against our
189          * interference; SUID, SGID and LSM creds get determined differently
190          * under ptrace.
191          */
192         retval = mutex_lock_interruptible(&task->cred_guard_mutex);
193         if (retval  < 0)
194                 goto out;
195
196         retval = -EPERM;
197 repeat:
198         /*
199          * Nasty, nasty.
200          *
201          * We want to hold both the task-lock and the
202          * tasklist_lock for writing at the same time.
203          * But that's against the rules (tasklist_lock
204          * is taken for reading by interrupts on other
205          * cpu's that may have task_lock).
206          */
207         task_lock(task);
208         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
209                 task_unlock(task);
210                 do {
211                         cpu_relax();
212                 } while (!write_can_lock(&tasklist_lock));
213                 goto repeat;
214         }
215
216         if (!task->mm)
217                 goto bad;
218         /* the same process cannot be attached many times */
219         if (task->ptrace & PT_PTRACED)
220                 goto bad;
221         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
222         if (retval)
223                 goto bad;
224
225         /* Go */
226         task->ptrace |= PT_PTRACED;
227         if (capable(CAP_SYS_PTRACE))
228                 task->ptrace |= PT_PTRACE_CAP;
229
230         __ptrace_link(task, current);
231
232         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
233 bad:
234         write_unlock_irqrestore(&tasklist_lock, flags);
235         task_unlock(task);
236         mutex_unlock(&task->cred_guard_mutex);
237 out:
238         return retval;
239 }
240
241 /*
242  * Called with irqs disabled, returns true if childs should reap themselves.
243  */
244 static int ignoring_children(struct sighand_struct *sigh)
245 {
246         int ret;
247         spin_lock(&sigh->siglock);
248         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
249               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
250         spin_unlock(&sigh->siglock);
251         return ret;
252 }
253
254 /*
255  * Called with tasklist_lock held for writing.
256  * Unlink a traced task, and clean it up if it was a traced zombie.
257  * Return true if it needs to be reaped with release_task().
258  * (We can't call release_task() here because we already hold tasklist_lock.)
259  *
260  * If it's a zombie, our attachedness prevented normal parent notification
261  * or self-reaping.  Do notification now if it would have happened earlier.
262  * If it should reap itself, return true.
263  *
264  * If it's our own child, there is no notification to do.
265  * But if our normal children self-reap, then this child
266  * was prevented by ptrace and we must reap it now.
267  */
268 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
269 {
270         __ptrace_unlink(p);
271
272         if (p->exit_state == EXIT_ZOMBIE) {
273                 if (!task_detached(p) && thread_group_empty(p)) {
274                         if (!same_thread_group(p->real_parent, tracer))
275                                 do_notify_parent(p, p->exit_signal);
276                         else if (ignoring_children(tracer->sighand))
277                                 p->exit_signal = -1;
278                 }
279                 if (task_detached(p)) {
280                         /* Mark it as in the process of being reaped. */
281                         p->exit_state = EXIT_DEAD;
282                         return true;
283                 }
284         }
285
286         return false;
287 }
288
289 int ptrace_detach(struct task_struct *child, unsigned int data)
290 {
291         bool dead = false;
292
293         if (!valid_signal(data))
294                 return -EIO;
295
296         /* Architecture-specific hardware disable .. */
297         ptrace_disable(child);
298         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
299
300         write_lock_irq(&tasklist_lock);
301         /*
302          * This child can be already killed. Make sure de_thread() or
303          * our sub-thread doing do_wait() didn't do release_task() yet.
304          */
305         if (child->ptrace) {
306                 child->exit_code = data;
307                 dead = __ptrace_detach(current, child);
308                 if (!child->exit_state)
309                         wake_up_process(child);
310         }
311         write_unlock_irq(&tasklist_lock);
312
313         if (unlikely(dead))
314                 release_task(child);
315
316         return 0;
317 }
318
319 /*
320  * Detach all tasks we were using ptrace on.
321  */
322 void exit_ptrace(struct task_struct *tracer)
323 {
324         struct task_struct *p, *n;
325         LIST_HEAD(ptrace_dead);
326
327         write_lock_irq(&tasklist_lock);
328         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
329                 if (__ptrace_detach(tracer, p))
330                         list_add(&p->ptrace_entry, &ptrace_dead);
331         }
332         write_unlock_irq(&tasklist_lock);
333
334         BUG_ON(!list_empty(&tracer->ptraced));
335
336         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
337                 list_del_init(&p->ptrace_entry);
338                 release_task(p);
339         }
340 }
341
342 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
343 {
344         int copied = 0;
345
346         while (len > 0) {
347                 char buf[128];
348                 int this_len, retval;
349
350                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
351                 retval = access_process_vm(tsk, src, buf, this_len, 0);
352                 if (!retval) {
353                         if (copied)
354                                 break;
355                         return -EIO;
356                 }
357                 if (copy_to_user(dst, buf, retval))
358                         return -EFAULT;
359                 copied += retval;
360                 src += retval;
361                 dst += retval;
362                 len -= retval;
363         }
364         return copied;
365 }
366
367 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
368 {
369         int copied = 0;
370
371         while (len > 0) {
372                 char buf[128];
373                 int this_len, retval;
374
375                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
376                 if (copy_from_user(buf, src, this_len))
377                         return -EFAULT;
378                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
379                 if (!retval) {
380                         if (copied)
381                                 break;
382                         return -EIO;
383                 }
384                 copied += retval;
385                 src += retval;
386                 dst += retval;
387                 len -= retval;
388         }
389         return copied;
390 }
391
392 static int ptrace_setoptions(struct task_struct *child, long data)
393 {
394         child->ptrace &= ~PT_TRACE_MASK;
395
396         if (data & PTRACE_O_TRACESYSGOOD)
397                 child->ptrace |= PT_TRACESYSGOOD;
398
399         if (data & PTRACE_O_TRACEFORK)
400                 child->ptrace |= PT_TRACE_FORK;
401
402         if (data & PTRACE_O_TRACEVFORK)
403                 child->ptrace |= PT_TRACE_VFORK;
404
405         if (data & PTRACE_O_TRACECLONE)
406                 child->ptrace |= PT_TRACE_CLONE;
407
408         if (data & PTRACE_O_TRACEEXEC)
409                 child->ptrace |= PT_TRACE_EXEC;
410
411         if (data & PTRACE_O_TRACEVFORKDONE)
412                 child->ptrace |= PT_TRACE_VFORK_DONE;
413
414         if (data & PTRACE_O_TRACEEXIT)
415                 child->ptrace |= PT_TRACE_EXIT;
416
417         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
418 }
419
420 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
421 {
422         int error = -ESRCH;
423
424         read_lock(&tasklist_lock);
425         if (likely(child->sighand != NULL)) {
426                 error = -EINVAL;
427                 spin_lock_irq(&child->sighand->siglock);
428                 if (likely(child->last_siginfo != NULL)) {
429                         *info = *child->last_siginfo;
430                         error = 0;
431                 }
432                 spin_unlock_irq(&child->sighand->siglock);
433         }
434         read_unlock(&tasklist_lock);
435         return error;
436 }
437
438 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
439 {
440         int error = -ESRCH;
441
442         read_lock(&tasklist_lock);
443         if (likely(child->sighand != NULL)) {
444                 error = -EINVAL;
445                 spin_lock_irq(&child->sighand->siglock);
446                 if (likely(child->last_siginfo != NULL)) {
447                         *child->last_siginfo = *info;
448                         error = 0;
449                 }
450                 spin_unlock_irq(&child->sighand->siglock);
451         }
452         read_unlock(&tasklist_lock);
453         return error;
454 }
455
456
457 #ifdef PTRACE_SINGLESTEP
458 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
459 #else
460 #define is_singlestep(request)          0
461 #endif
462
463 #ifdef PTRACE_SINGLEBLOCK
464 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
465 #else
466 #define is_singleblock(request)         0
467 #endif
468
469 #ifdef PTRACE_SYSEMU
470 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
471 #else
472 #define is_sysemu_singlestep(request)   0
473 #endif
474
475 static int ptrace_resume(struct task_struct *child, long request, long data)
476 {
477         if (!valid_signal(data))
478                 return -EIO;
479
480         if (request == PTRACE_SYSCALL)
481                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
482         else
483                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
484
485 #ifdef TIF_SYSCALL_EMU
486         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
487                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
488         else
489                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
490 #endif
491
492         if (is_singleblock(request)) {
493                 if (unlikely(!arch_has_block_step()))
494                         return -EIO;
495                 user_enable_block_step(child);
496         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
497                 if (unlikely(!arch_has_single_step()))
498                         return -EIO;
499                 user_enable_single_step(child);
500         } else {
501                 user_disable_single_step(child);
502         }
503
504         child->exit_code = data;
505         wake_up_process(child);
506
507         return 0;
508 }
509
510 int ptrace_request(struct task_struct *child, long request,
511                    long addr, long data)
512 {
513         int ret = -EIO;
514         siginfo_t siginfo;
515
516         switch (request) {
517         case PTRACE_PEEKTEXT:
518         case PTRACE_PEEKDATA:
519                 return generic_ptrace_peekdata(child, addr, data);
520         case PTRACE_POKETEXT:
521         case PTRACE_POKEDATA:
522                 return generic_ptrace_pokedata(child, addr, data);
523
524 #ifdef PTRACE_OLDSETOPTIONS
525         case PTRACE_OLDSETOPTIONS:
526 #endif
527         case PTRACE_SETOPTIONS:
528                 ret = ptrace_setoptions(child, data);
529                 break;
530         case PTRACE_GETEVENTMSG:
531                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
532                 break;
533
534         case PTRACE_GETSIGINFO:
535                 ret = ptrace_getsiginfo(child, &siginfo);
536                 if (!ret)
537                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
538                                                    &siginfo);
539                 break;
540
541         case PTRACE_SETSIGINFO:
542                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
543                                    sizeof siginfo))
544                         ret = -EFAULT;
545                 else
546                         ret = ptrace_setsiginfo(child, &siginfo);
547                 break;
548
549         case PTRACE_DETACH:      /* detach a process that was attached. */
550                 ret = ptrace_detach(child, data);
551                 break;
552
553 #ifdef PTRACE_SINGLESTEP
554         case PTRACE_SINGLESTEP:
555 #endif
556 #ifdef PTRACE_SINGLEBLOCK
557         case PTRACE_SINGLEBLOCK:
558 #endif
559 #ifdef PTRACE_SYSEMU
560         case PTRACE_SYSEMU:
561         case PTRACE_SYSEMU_SINGLESTEP:
562 #endif
563         case PTRACE_SYSCALL:
564         case PTRACE_CONT:
565                 return ptrace_resume(child, request, data);
566
567         case PTRACE_KILL:
568                 if (child->exit_state)  /* already dead */
569                         return 0;
570                 return ptrace_resume(child, request, SIGKILL);
571
572         default:
573                 break;
574         }
575
576         return ret;
577 }
578
579 /**
580  * ptrace_traceme  --  helper for PTRACE_TRACEME
581  *
582  * Performs checks and sets PT_PTRACED.
583  * Should be used by all ptrace implementations for PTRACE_TRACEME.
584  */
585 int ptrace_traceme(void)
586 {
587         int ret = -EPERM;
588
589         /*
590          * Are we already being traced?
591          */
592 repeat:
593         task_lock(current);
594         if (!(current->ptrace & PT_PTRACED)) {
595                 /*
596                  * See ptrace_attach() comments about the locking here.
597                  */
598                 unsigned long flags;
599                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
600                         task_unlock(current);
601                         do {
602                                 cpu_relax();
603                         } while (!write_can_lock(&tasklist_lock));
604                         goto repeat;
605                 }
606
607                 ret = security_ptrace_traceme(current->parent);
608
609                 /*
610                  * Check PF_EXITING to ensure ->real_parent has not passed
611                  * exit_ptrace(). Otherwise we don't report the error but
612                  * pretend ->real_parent untraces us right after return.
613                  */
614                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
615                         current->ptrace |= PT_PTRACED;
616                         __ptrace_link(current, current->real_parent);
617                 }
618
619                 write_unlock_irqrestore(&tasklist_lock, flags);
620         }
621         task_unlock(current);
622         return ret;
623 }
624
625 /**
626  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
627  * @pid:       process id to grab a task_struct reference of
628  *
629  * This function is a helper for ptrace implementations.  It checks
630  * permissions and then grabs a task struct for use of the actual
631  * ptrace implementation.
632  *
633  * Returns the task_struct for @pid or an ERR_PTR() on failure.
634  */
635 struct task_struct *ptrace_get_task_struct(pid_t pid)
636 {
637         struct task_struct *child;
638
639         read_lock(&tasklist_lock);
640         child = find_task_by_vpid(pid);
641         if (child)
642                 get_task_struct(child);
643
644         read_unlock(&tasklist_lock);
645         if (!child)
646                 return ERR_PTR(-ESRCH);
647         return child;
648 }
649
650 #ifndef arch_ptrace_attach
651 #define arch_ptrace_attach(child)       do { } while (0)
652 #endif
653
654 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
655 {
656         struct task_struct *child;
657         long ret;
658
659         /*
660          * This lock_kernel fixes a subtle race with suid exec
661          */
662         lock_kernel();
663         if (request == PTRACE_TRACEME) {
664                 ret = ptrace_traceme();
665                 if (!ret)
666                         arch_ptrace_attach(current);
667                 goto out;
668         }
669
670         child = ptrace_get_task_struct(pid);
671         if (IS_ERR(child)) {
672                 ret = PTR_ERR(child);
673                 goto out;
674         }
675
676         if (request == PTRACE_ATTACH) {
677                 ret = ptrace_attach(child);
678                 /*
679                  * Some architectures need to do book-keeping after
680                  * a ptrace attach.
681                  */
682                 if (!ret)
683                         arch_ptrace_attach(child);
684                 goto out_put_task_struct;
685         }
686
687         ret = ptrace_check_attach(child, request == PTRACE_KILL);
688         if (ret < 0)
689                 goto out_put_task_struct;
690
691         ret = arch_ptrace(child, request, addr, data);
692
693  out_put_task_struct:
694         put_task_struct(child);
695  out:
696         unlock_kernel();
697         return ret;
698 }
699
700 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
701 {
702         unsigned long tmp;
703         int copied;
704
705         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
706         if (copied != sizeof(tmp))
707                 return -EIO;
708         return put_user(tmp, (unsigned long __user *)data);
709 }
710
711 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
712 {
713         int copied;
714
715         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
716         return (copied == sizeof(data)) ? 0 : -EIO;
717 }
718
719 #if defined CONFIG_COMPAT
720 #include <linux/compat.h>
721
722 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
723                           compat_ulong_t addr, compat_ulong_t data)
724 {
725         compat_ulong_t __user *datap = compat_ptr(data);
726         compat_ulong_t word;
727         siginfo_t siginfo;
728         int ret;
729
730         switch (request) {
731         case PTRACE_PEEKTEXT:
732         case PTRACE_PEEKDATA:
733                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
734                 if (ret != sizeof(word))
735                         ret = -EIO;
736                 else
737                         ret = put_user(word, datap);
738                 break;
739
740         case PTRACE_POKETEXT:
741         case PTRACE_POKEDATA:
742                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
743                 ret = (ret != sizeof(data) ? -EIO : 0);
744                 break;
745
746         case PTRACE_GETEVENTMSG:
747                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
748                 break;
749
750         case PTRACE_GETSIGINFO:
751                 ret = ptrace_getsiginfo(child, &siginfo);
752                 if (!ret)
753                         ret = copy_siginfo_to_user32(
754                                 (struct compat_siginfo __user *) datap,
755                                 &siginfo);
756                 break;
757
758         case PTRACE_SETSIGINFO:
759                 memset(&siginfo, 0, sizeof siginfo);
760                 if (copy_siginfo_from_user32(
761                             &siginfo, (struct compat_siginfo __user *) datap))
762                         ret = -EFAULT;
763                 else
764                         ret = ptrace_setsiginfo(child, &siginfo);
765                 break;
766
767         default:
768                 ret = ptrace_request(child, request, addr, data);
769         }
770
771         return ret;
772 }
773
774 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
775                                   compat_long_t addr, compat_long_t data)
776 {
777         struct task_struct *child;
778         long ret;
779
780         /*
781          * This lock_kernel fixes a subtle race with suid exec
782          */
783         lock_kernel();
784         if (request == PTRACE_TRACEME) {
785                 ret = ptrace_traceme();
786                 goto out;
787         }
788
789         child = ptrace_get_task_struct(pid);
790         if (IS_ERR(child)) {
791                 ret = PTR_ERR(child);
792                 goto out;
793         }
794
795         if (request == PTRACE_ATTACH) {
796                 ret = ptrace_attach(child);
797                 /*
798                  * Some architectures need to do book-keeping after
799                  * a ptrace attach.
800                  */
801                 if (!ret)
802                         arch_ptrace_attach(child);
803                 goto out_put_task_struct;
804         }
805
806         ret = ptrace_check_attach(child, request == PTRACE_KILL);
807         if (!ret)
808                 ret = compat_arch_ptrace(child, request, addr, data);
809
810  out_put_task_struct:
811         put_task_struct(child);
812  out:
813         unlock_kernel();
814         return ret;
815 }
816 #endif  /* CONFIG_COMPAT */