ptrace: revert "ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic"
[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 exec's credential calculations against our interference;
189          * SUID, SGID and LSM creds get determined differently under ptrace.
190          */
191         retval = mutex_lock_interruptible(&task->cred_exec_mutex);
192         if (retval  < 0)
193                 goto out;
194
195         retval = -EPERM;
196 repeat:
197         /*
198          * Nasty, nasty.
199          *
200          * We want to hold both the task-lock and the
201          * tasklist_lock for writing at the same time.
202          * But that's against the rules (tasklist_lock
203          * is taken for reading by interrupts on other
204          * cpu's that may have task_lock).
205          */
206         task_lock(task);
207         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
208                 task_unlock(task);
209                 do {
210                         cpu_relax();
211                 } while (!write_can_lock(&tasklist_lock));
212                 goto repeat;
213         }
214
215         if (!task->mm)
216                 goto bad;
217         /* the same process cannot be attached many times */
218         if (task->ptrace & PT_PTRACED)
219                 goto bad;
220         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
221         if (retval)
222                 goto bad;
223
224         /* Go */
225         task->ptrace |= PT_PTRACED;
226         if (capable(CAP_SYS_PTRACE))
227                 task->ptrace |= PT_PTRACE_CAP;
228
229         __ptrace_link(task, current);
230
231         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
232 bad:
233         write_unlock_irqrestore(&tasklist_lock, flags);
234         task_unlock(task);
235         mutex_unlock(&task->cred_exec_mutex);
236 out:
237         return retval;
238 }
239
240 /*
241  * Called with irqs disabled, returns true if childs should reap themselves.
242  */
243 static int ignoring_children(struct sighand_struct *sigh)
244 {
245         int ret;
246         spin_lock(&sigh->siglock);
247         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
248               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
249         spin_unlock(&sigh->siglock);
250         return ret;
251 }
252
253 /*
254  * Called with tasklist_lock held for writing.
255  * Unlink a traced task, and clean it up if it was a traced zombie.
256  * Return true if it needs to be reaped with release_task().
257  * (We can't call release_task() here because we already hold tasklist_lock.)
258  *
259  * If it's a zombie, our attachedness prevented normal parent notification
260  * or self-reaping.  Do notification now if it would have happened earlier.
261  * If it should reap itself, return true.
262  *
263  * If it's our own child, there is no notification to do.
264  * But if our normal children self-reap, then this child
265  * was prevented by ptrace and we must reap it now.
266  */
267 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
268 {
269         __ptrace_unlink(p);
270
271         if (p->exit_state == EXIT_ZOMBIE) {
272                 if (!task_detached(p) && thread_group_empty(p)) {
273                         if (!same_thread_group(p->real_parent, tracer))
274                                 do_notify_parent(p, p->exit_signal);
275                         else if (ignoring_children(tracer->sighand))
276                                 p->exit_signal = -1;
277                 }
278                 if (task_detached(p)) {
279                         /* Mark it as in the process of being reaped. */
280                         p->exit_state = EXIT_DEAD;
281                         return true;
282                 }
283         }
284
285         return false;
286 }
287
288 int ptrace_detach(struct task_struct *child, unsigned int data)
289 {
290         bool dead = false;
291
292         if (!valid_signal(data))
293                 return -EIO;
294
295         /* Architecture-specific hardware disable .. */
296         ptrace_disable(child);
297         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
298
299         write_lock_irq(&tasklist_lock);
300         /*
301          * This child can be already killed. Make sure de_thread() or
302          * our sub-thread doing do_wait() didn't do release_task() yet.
303          */
304         if (child->ptrace) {
305                 child->exit_code = data;
306                 dead = __ptrace_detach(current, child);
307                 if (!child->exit_state)
308                         wake_up_process(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         } else {
500                 user_disable_single_step(child);
501         }
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                  * Check PF_EXITING to ensure ->real_parent has not passed
610                  * exit_ptrace(). Otherwise we don't report the error but
611                  * pretend ->real_parent untraces us right after return.
612                  */
613                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
614                         current->ptrace |= PT_PTRACED;
615                         __ptrace_link(current, current->real_parent);
616                 }
617
618                 write_unlock_irqrestore(&tasklist_lock, flags);
619         }
620         task_unlock(current);
621         return ret;
622 }
623
624 /**
625  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
626  * @pid:       process id to grab a task_struct reference of
627  *
628  * This function is a helper for ptrace implementations.  It checks
629  * permissions and then grabs a task struct for use of the actual
630  * ptrace implementation.
631  *
632  * Returns the task_struct for @pid or an ERR_PTR() on failure.
633  */
634 struct task_struct *ptrace_get_task_struct(pid_t pid)
635 {
636         struct task_struct *child;
637
638         read_lock(&tasklist_lock);
639         child = find_task_by_vpid(pid);
640         if (child)
641                 get_task_struct(child);
642
643         read_unlock(&tasklist_lock);
644         if (!child)
645                 return ERR_PTR(-ESRCH);
646         return child;
647 }
648
649 #ifndef arch_ptrace_attach
650 #define arch_ptrace_attach(child)       do { } while (0)
651 #endif
652
653 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
654 {
655         struct task_struct *child;
656         long ret;
657
658         /*
659          * This lock_kernel fixes a subtle race with suid exec
660          */
661         lock_kernel();
662         if (request == PTRACE_TRACEME) {
663                 ret = ptrace_traceme();
664                 if (!ret)
665                         arch_ptrace_attach(current);
666                 goto out;
667         }
668
669         child = ptrace_get_task_struct(pid);
670         if (IS_ERR(child)) {
671                 ret = PTR_ERR(child);
672                 goto out;
673         }
674
675         if (request == PTRACE_ATTACH) {
676                 ret = ptrace_attach(child);
677                 /*
678                  * Some architectures need to do book-keeping after
679                  * a ptrace attach.
680                  */
681                 if (!ret)
682                         arch_ptrace_attach(child);
683                 goto out_put_task_struct;
684         }
685
686         ret = ptrace_check_attach(child, request == PTRACE_KILL);
687         if (ret < 0)
688                 goto out_put_task_struct;
689
690         ret = arch_ptrace(child, request, addr, data);
691
692  out_put_task_struct:
693         put_task_struct(child);
694  out:
695         unlock_kernel();
696         return ret;
697 }
698
699 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
700 {
701         unsigned long tmp;
702         int copied;
703
704         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
705         if (copied != sizeof(tmp))
706                 return -EIO;
707         return put_user(tmp, (unsigned long __user *)data);
708 }
709
710 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
711 {
712         int copied;
713
714         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
715         return (copied == sizeof(data)) ? 0 : -EIO;
716 }
717
718 #if defined CONFIG_COMPAT
719 #include <linux/compat.h>
720
721 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
722                           compat_ulong_t addr, compat_ulong_t data)
723 {
724         compat_ulong_t __user *datap = compat_ptr(data);
725         compat_ulong_t word;
726         siginfo_t siginfo;
727         int ret;
728
729         switch (request) {
730         case PTRACE_PEEKTEXT:
731         case PTRACE_PEEKDATA:
732                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
733                 if (ret != sizeof(word))
734                         ret = -EIO;
735                 else
736                         ret = put_user(word, datap);
737                 break;
738
739         case PTRACE_POKETEXT:
740         case PTRACE_POKEDATA:
741                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
742                 ret = (ret != sizeof(data) ? -EIO : 0);
743                 break;
744
745         case PTRACE_GETEVENTMSG:
746                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
747                 break;
748
749         case PTRACE_GETSIGINFO:
750                 ret = ptrace_getsiginfo(child, &siginfo);
751                 if (!ret)
752                         ret = copy_siginfo_to_user32(
753                                 (struct compat_siginfo __user *) datap,
754                                 &siginfo);
755                 break;
756
757         case PTRACE_SETSIGINFO:
758                 memset(&siginfo, 0, sizeof siginfo);
759                 if (copy_siginfo_from_user32(
760                             &siginfo, (struct compat_siginfo __user *) datap))
761                         ret = -EFAULT;
762                 else
763                         ret = ptrace_setsiginfo(child, &siginfo);
764                 break;
765
766         default:
767                 ret = ptrace_request(child, request, addr, data);
768         }
769
770         return ret;
771 }
772
773 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
774                                   compat_long_t addr, compat_long_t data)
775 {
776         struct task_struct *child;
777         long ret;
778
779         /*
780          * This lock_kernel fixes a subtle race with suid exec
781          */
782         lock_kernel();
783         if (request == PTRACE_TRACEME) {
784                 ret = ptrace_traceme();
785                 goto out;
786         }
787
788         child = ptrace_get_task_struct(pid);
789         if (IS_ERR(child)) {
790                 ret = PTR_ERR(child);
791                 goto out;
792         }
793
794         if (request == PTRACE_ATTACH) {
795                 ret = ptrace_attach(child);
796                 /*
797                  * Some architectures need to do book-keeping after
798                  * a ptrace attach.
799                  */
800                 if (!ret)
801                         arch_ptrace_attach(child);
802                 goto out_put_task_struct;
803         }
804
805         ret = ptrace_check_attach(child, request == PTRACE_KILL);
806         if (!ret)
807                 ret = compat_arch_ptrace(child, request, addr, data);
808
809  out_put_task_struct:
810         put_task_struct(child);
811  out:
812         unlock_kernel();
813         return ret;
814 }
815 #endif  /* CONFIG_COMPAT */