Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-3.10.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  * 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 (same_thread_group(task, current))
176                 goto out;
177
178         /* Protect exec's credential calculations against our interference;
179          * SUID, SGID and LSM creds get determined differently under ptrace.
180          */
181         retval = mutex_lock_interruptible(&task->cred_exec_mutex);
182         if (retval  < 0)
183                 goto out;
184
185         retval = -EPERM;
186 repeat:
187         /*
188          * Nasty, nasty.
189          *
190          * We want to hold both the task-lock and the
191          * tasklist_lock for writing at the same time.
192          * But that's against the rules (tasklist_lock
193          * is taken for reading by interrupts on other
194          * cpu's that may have task_lock).
195          */
196         task_lock(task);
197         if (!write_trylock_irqsave(&tasklist_lock, flags)) {
198                 task_unlock(task);
199                 do {
200                         cpu_relax();
201                 } while (!write_can_lock(&tasklist_lock));
202                 goto repeat;
203         }
204
205         if (!task->mm)
206                 goto bad;
207         /* the same process cannot be attached many times */
208         if (task->ptrace & PT_PTRACED)
209                 goto bad;
210         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
211         if (retval)
212                 goto bad;
213
214         /* Go */
215         task->ptrace |= PT_PTRACED;
216         if (capable(CAP_SYS_PTRACE))
217                 task->ptrace |= PT_PTRACE_CAP;
218
219         __ptrace_link(task, current);
220
221         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
222 bad:
223         write_unlock_irqrestore(&tasklist_lock, flags);
224         task_unlock(task);
225         mutex_unlock(&task->cred_exec_mutex);
226 out:
227         return retval;
228 }
229
230 /*
231  * Called with irqs disabled, returns true if childs should reap themselves.
232  */
233 static int ignoring_children(struct sighand_struct *sigh)
234 {
235         int ret;
236         spin_lock(&sigh->siglock);
237         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
238               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
239         spin_unlock(&sigh->siglock);
240         return ret;
241 }
242
243 /*
244  * Called with tasklist_lock held for writing.
245  * Unlink a traced task, and clean it up if it was a traced zombie.
246  * Return true if it needs to be reaped with release_task().
247  * (We can't call release_task() here because we already hold tasklist_lock.)
248  *
249  * If it's a zombie, our attachedness prevented normal parent notification
250  * or self-reaping.  Do notification now if it would have happened earlier.
251  * If it should reap itself, return true.
252  *
253  * If it's our own child, there is no notification to do.
254  * But if our normal children self-reap, then this child
255  * was prevented by ptrace and we must reap it now.
256  */
257 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
258 {
259         __ptrace_unlink(p);
260
261         if (p->exit_state == EXIT_ZOMBIE) {
262                 if (!task_detached(p) && thread_group_empty(p)) {
263                         if (!same_thread_group(p->real_parent, tracer))
264                                 do_notify_parent(p, p->exit_signal);
265                         else if (ignoring_children(tracer->sighand))
266                                 p->exit_signal = -1;
267                 }
268                 if (task_detached(p)) {
269                         /* Mark it as in the process of being reaped. */
270                         p->exit_state = EXIT_DEAD;
271                         return true;
272                 }
273         }
274
275         return false;
276 }
277
278 int ptrace_detach(struct task_struct *child, unsigned int data)
279 {
280         bool dead = false;
281
282         if (!valid_signal(data))
283                 return -EIO;
284
285         /* Architecture-specific hardware disable .. */
286         ptrace_disable(child);
287         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
288
289         write_lock_irq(&tasklist_lock);
290         /*
291          * This child can be already killed. Make sure de_thread() or
292          * our sub-thread doing do_wait() didn't do release_task() yet.
293          */
294         if (child->ptrace) {
295                 child->exit_code = data;
296                 dead = __ptrace_detach(current, child);
297                 if (!child->exit_state)
298                         wake_up_process(child);
299         }
300         write_unlock_irq(&tasklist_lock);
301
302         if (unlikely(dead))
303                 release_task(child);
304
305         return 0;
306 }
307
308 /*
309  * Detach all tasks we were using ptrace on.
310  */
311 void exit_ptrace(struct task_struct *tracer)
312 {
313         struct task_struct *p, *n;
314         LIST_HEAD(ptrace_dead);
315
316         write_lock_irq(&tasklist_lock);
317         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
318                 if (__ptrace_detach(tracer, p))
319                         list_add(&p->ptrace_entry, &ptrace_dead);
320         }
321         write_unlock_irq(&tasklist_lock);
322
323         BUG_ON(!list_empty(&tracer->ptraced));
324
325         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
326                 list_del_init(&p->ptrace_entry);
327                 release_task(p);
328         }
329 }
330
331 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
332 {
333         int copied = 0;
334
335         while (len > 0) {
336                 char buf[128];
337                 int this_len, retval;
338
339                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
340                 retval = access_process_vm(tsk, src, buf, this_len, 0);
341                 if (!retval) {
342                         if (copied)
343                                 break;
344                         return -EIO;
345                 }
346                 if (copy_to_user(dst, buf, retval))
347                         return -EFAULT;
348                 copied += retval;
349                 src += retval;
350                 dst += retval;
351                 len -= retval;
352         }
353         return copied;
354 }
355
356 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
357 {
358         int copied = 0;
359
360         while (len > 0) {
361                 char buf[128];
362                 int this_len, retval;
363
364                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
365                 if (copy_from_user(buf, src, this_len))
366                         return -EFAULT;
367                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
368                 if (!retval) {
369                         if (copied)
370                                 break;
371                         return -EIO;
372                 }
373                 copied += retval;
374                 src += retval;
375                 dst += retval;
376                 len -= retval;
377         }
378         return copied;
379 }
380
381 static int ptrace_setoptions(struct task_struct *child, long data)
382 {
383         child->ptrace &= ~PT_TRACE_MASK;
384
385         if (data & PTRACE_O_TRACESYSGOOD)
386                 child->ptrace |= PT_TRACESYSGOOD;
387
388         if (data & PTRACE_O_TRACEFORK)
389                 child->ptrace |= PT_TRACE_FORK;
390
391         if (data & PTRACE_O_TRACEVFORK)
392                 child->ptrace |= PT_TRACE_VFORK;
393
394         if (data & PTRACE_O_TRACECLONE)
395                 child->ptrace |= PT_TRACE_CLONE;
396
397         if (data & PTRACE_O_TRACEEXEC)
398                 child->ptrace |= PT_TRACE_EXEC;
399
400         if (data & PTRACE_O_TRACEVFORKDONE)
401                 child->ptrace |= PT_TRACE_VFORK_DONE;
402
403         if (data & PTRACE_O_TRACEEXIT)
404                 child->ptrace |= PT_TRACE_EXIT;
405
406         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
407 }
408
409 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
410 {
411         int error = -ESRCH;
412
413         read_lock(&tasklist_lock);
414         if (likely(child->sighand != NULL)) {
415                 error = -EINVAL;
416                 spin_lock_irq(&child->sighand->siglock);
417                 if (likely(child->last_siginfo != NULL)) {
418                         *info = *child->last_siginfo;
419                         error = 0;
420                 }
421                 spin_unlock_irq(&child->sighand->siglock);
422         }
423         read_unlock(&tasklist_lock);
424         return error;
425 }
426
427 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
428 {
429         int error = -ESRCH;
430
431         read_lock(&tasklist_lock);
432         if (likely(child->sighand != NULL)) {
433                 error = -EINVAL;
434                 spin_lock_irq(&child->sighand->siglock);
435                 if (likely(child->last_siginfo != NULL)) {
436                         *child->last_siginfo = *info;
437                         error = 0;
438                 }
439                 spin_unlock_irq(&child->sighand->siglock);
440         }
441         read_unlock(&tasklist_lock);
442         return error;
443 }
444
445
446 #ifdef PTRACE_SINGLESTEP
447 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
448 #else
449 #define is_singlestep(request)          0
450 #endif
451
452 #ifdef PTRACE_SINGLEBLOCK
453 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
454 #else
455 #define is_singleblock(request)         0
456 #endif
457
458 #ifdef PTRACE_SYSEMU
459 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
460 #else
461 #define is_sysemu_singlestep(request)   0
462 #endif
463
464 static int ptrace_resume(struct task_struct *child, long request, long data)
465 {
466         if (!valid_signal(data))
467                 return -EIO;
468
469         if (request == PTRACE_SYSCALL)
470                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
471         else
472                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
473
474 #ifdef TIF_SYSCALL_EMU
475         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
476                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
477         else
478                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
479 #endif
480
481         if (is_singleblock(request)) {
482                 if (unlikely(!arch_has_block_step()))
483                         return -EIO;
484                 user_enable_block_step(child);
485         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
486                 if (unlikely(!arch_has_single_step()))
487                         return -EIO;
488                 user_enable_single_step(child);
489         } else {
490                 user_disable_single_step(child);
491         }
492
493         child->exit_code = data;
494         wake_up_process(child);
495
496         return 0;
497 }
498
499 int ptrace_request(struct task_struct *child, long request,
500                    long addr, long data)
501 {
502         int ret = -EIO;
503         siginfo_t siginfo;
504
505         switch (request) {
506         case PTRACE_PEEKTEXT:
507         case PTRACE_PEEKDATA:
508                 return generic_ptrace_peekdata(child, addr, data);
509         case PTRACE_POKETEXT:
510         case PTRACE_POKEDATA:
511                 return generic_ptrace_pokedata(child, addr, data);
512
513 #ifdef PTRACE_OLDSETOPTIONS
514         case PTRACE_OLDSETOPTIONS:
515 #endif
516         case PTRACE_SETOPTIONS:
517                 ret = ptrace_setoptions(child, data);
518                 break;
519         case PTRACE_GETEVENTMSG:
520                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
521                 break;
522
523         case PTRACE_GETSIGINFO:
524                 ret = ptrace_getsiginfo(child, &siginfo);
525                 if (!ret)
526                         ret = copy_siginfo_to_user((siginfo_t __user *) data,
527                                                    &siginfo);
528                 break;
529
530         case PTRACE_SETSIGINFO:
531                 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
532                                    sizeof siginfo))
533                         ret = -EFAULT;
534                 else
535                         ret = ptrace_setsiginfo(child, &siginfo);
536                 break;
537
538         case PTRACE_DETACH:      /* detach a process that was attached. */
539                 ret = ptrace_detach(child, data);
540                 break;
541
542 #ifdef PTRACE_SINGLESTEP
543         case PTRACE_SINGLESTEP:
544 #endif
545 #ifdef PTRACE_SINGLEBLOCK
546         case PTRACE_SINGLEBLOCK:
547 #endif
548 #ifdef PTRACE_SYSEMU
549         case PTRACE_SYSEMU:
550         case PTRACE_SYSEMU_SINGLESTEP:
551 #endif
552         case PTRACE_SYSCALL:
553         case PTRACE_CONT:
554                 return ptrace_resume(child, request, data);
555
556         case PTRACE_KILL:
557                 if (child->exit_state)  /* already dead */
558                         return 0;
559                 return ptrace_resume(child, request, SIGKILL);
560
561         default:
562                 break;
563         }
564
565         return ret;
566 }
567
568 /**
569  * ptrace_traceme  --  helper for PTRACE_TRACEME
570  *
571  * Performs checks and sets PT_PTRACED.
572  * Should be used by all ptrace implementations for PTRACE_TRACEME.
573  */
574 int ptrace_traceme(void)
575 {
576         int ret = -EPERM;
577
578         /*
579          * Are we already being traced?
580          */
581 repeat:
582         task_lock(current);
583         if (!(current->ptrace & PT_PTRACED)) {
584                 /*
585                  * See ptrace_attach() comments about the locking here.
586                  */
587                 unsigned long flags;
588                 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
589                         task_unlock(current);
590                         do {
591                                 cpu_relax();
592                         } while (!write_can_lock(&tasklist_lock));
593                         goto repeat;
594                 }
595
596                 ret = security_ptrace_traceme(current->parent);
597
598                 /*
599                  * Check PF_EXITING to ensure ->real_parent has not passed
600                  * exit_ptrace(). Otherwise we don't report the error but
601                  * pretend ->real_parent untraces us right after return.
602                  */
603                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
604                         current->ptrace |= PT_PTRACED;
605                         __ptrace_link(current, current->real_parent);
606                 }
607
608                 write_unlock_irqrestore(&tasklist_lock, flags);
609         }
610         task_unlock(current);
611         return ret;
612 }
613
614 /**
615  * ptrace_get_task_struct  --  grab a task struct reference for ptrace
616  * @pid:       process id to grab a task_struct reference of
617  *
618  * This function is a helper for ptrace implementations.  It checks
619  * permissions and then grabs a task struct for use of the actual
620  * ptrace implementation.
621  *
622  * Returns the task_struct for @pid or an ERR_PTR() on failure.
623  */
624 struct task_struct *ptrace_get_task_struct(pid_t pid)
625 {
626         struct task_struct *child;
627
628         read_lock(&tasklist_lock);
629         child = find_task_by_vpid(pid);
630         if (child)
631                 get_task_struct(child);
632
633         read_unlock(&tasklist_lock);
634         if (!child)
635                 return ERR_PTR(-ESRCH);
636         return child;
637 }
638
639 #ifndef arch_ptrace_attach
640 #define arch_ptrace_attach(child)       do { } while (0)
641 #endif
642
643 SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
644 {
645         struct task_struct *child;
646         long ret;
647
648         /*
649          * This lock_kernel fixes a subtle race with suid exec
650          */
651         lock_kernel();
652         if (request == PTRACE_TRACEME) {
653                 ret = ptrace_traceme();
654                 if (!ret)
655                         arch_ptrace_attach(current);
656                 goto out;
657         }
658
659         child = ptrace_get_task_struct(pid);
660         if (IS_ERR(child)) {
661                 ret = PTR_ERR(child);
662                 goto out;
663         }
664
665         if (request == PTRACE_ATTACH) {
666                 ret = ptrace_attach(child);
667                 /*
668                  * Some architectures need to do book-keeping after
669                  * a ptrace attach.
670                  */
671                 if (!ret)
672                         arch_ptrace_attach(child);
673                 goto out_put_task_struct;
674         }
675
676         ret = ptrace_check_attach(child, request == PTRACE_KILL);
677         if (ret < 0)
678                 goto out_put_task_struct;
679
680         ret = arch_ptrace(child, request, addr, data);
681
682  out_put_task_struct:
683         put_task_struct(child);
684  out:
685         unlock_kernel();
686         return ret;
687 }
688
689 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
690 {
691         unsigned long tmp;
692         int copied;
693
694         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
695         if (copied != sizeof(tmp))
696                 return -EIO;
697         return put_user(tmp, (unsigned long __user *)data);
698 }
699
700 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
701 {
702         int copied;
703
704         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
705         return (copied == sizeof(data)) ? 0 : -EIO;
706 }
707
708 #if defined CONFIG_COMPAT
709 #include <linux/compat.h>
710
711 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
712                           compat_ulong_t addr, compat_ulong_t data)
713 {
714         compat_ulong_t __user *datap = compat_ptr(data);
715         compat_ulong_t word;
716         siginfo_t siginfo;
717         int ret;
718
719         switch (request) {
720         case PTRACE_PEEKTEXT:
721         case PTRACE_PEEKDATA:
722                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
723                 if (ret != sizeof(word))
724                         ret = -EIO;
725                 else
726                         ret = put_user(word, datap);
727                 break;
728
729         case PTRACE_POKETEXT:
730         case PTRACE_POKEDATA:
731                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
732                 ret = (ret != sizeof(data) ? -EIO : 0);
733                 break;
734
735         case PTRACE_GETEVENTMSG:
736                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
737                 break;
738
739         case PTRACE_GETSIGINFO:
740                 ret = ptrace_getsiginfo(child, &siginfo);
741                 if (!ret)
742                         ret = copy_siginfo_to_user32(
743                                 (struct compat_siginfo __user *) datap,
744                                 &siginfo);
745                 break;
746
747         case PTRACE_SETSIGINFO:
748                 memset(&siginfo, 0, sizeof siginfo);
749                 if (copy_siginfo_from_user32(
750                             &siginfo, (struct compat_siginfo __user *) datap))
751                         ret = -EFAULT;
752                 else
753                         ret = ptrace_setsiginfo(child, &siginfo);
754                 break;
755
756         default:
757                 ret = ptrace_request(child, request, addr, data);
758         }
759
760         return ret;
761 }
762
763 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
764                                   compat_long_t addr, compat_long_t data)
765 {
766         struct task_struct *child;
767         long ret;
768
769         /*
770          * This lock_kernel fixes a subtle race with suid exec
771          */
772         lock_kernel();
773         if (request == PTRACE_TRACEME) {
774                 ret = ptrace_traceme();
775                 goto out;
776         }
777
778         child = ptrace_get_task_struct(pid);
779         if (IS_ERR(child)) {
780                 ret = PTR_ERR(child);
781                 goto out;
782         }
783
784         if (request == PTRACE_ATTACH) {
785                 ret = ptrace_attach(child);
786                 /*
787                  * Some architectures need to do book-keeping after
788                  * a ptrace attach.
789                  */
790                 if (!ret)
791                         arch_ptrace_attach(child);
792                 goto out_put_task_struct;
793         }
794
795         ret = ptrace_check_attach(child, request == PTRACE_KILL);
796         if (!ret)
797                 ret = compat_arch_ptrace(child, request, addr, data);
798
799  out_put_task_struct:
800         put_task_struct(child);
801  out:
802         unlock_kernel();
803         return ret;
804 }
805 #endif  /* CONFIG_COMPAT */