2 * linux/kernel/ptrace.c
4 * (C) Copyright 1999 Linus Torvalds
6 * Common interfaces for "ptrace()" which we do not want
7 * to continually duplicate across every architecture.
10 #include <linux/capability.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/errno.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>
25 #include <asm/pgtable.h>
26 #include <asm/uaccess.h>
29 * ptrace a task: make the debugger its new parent and
30 * move it to the ptrace list.
32 * Must be called with the tasklist lock write-held.
34 void __ptrace_link(struct task_struct
*child
, struct task_struct
*new_parent
)
36 BUG_ON(!list_empty(&child
->ptrace_entry
));
37 list_add(&child
->ptrace_entry
, &new_parent
->ptraced
);
38 child
->parent
= new_parent
;
42 * Turn a tracing stop into a normal stop now, since with no tracer there
43 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
44 * signal sent that would resume the child, but didn't because it was in
45 * TASK_TRACED, resume it now.
46 * Requires that irqs be disabled.
48 static void ptrace_untrace(struct task_struct
*child
)
50 spin_lock(&child
->sighand
->siglock
);
51 if (task_is_traced(child
)) {
52 if (child
->signal
->flags
& SIGNAL_STOP_STOPPED
) {
53 __set_task_state(child
, TASK_STOPPED
);
55 signal_wake_up(child
, 1);
58 spin_unlock(&child
->sighand
->siglock
);
62 * unptrace a task: move it back to its original parent and
63 * remove it from the ptrace list.
65 * Must be called with the tasklist lock write-held.
67 void __ptrace_unlink(struct task_struct
*child
)
69 BUG_ON(!child
->ptrace
);
72 child
->parent
= child
->real_parent
;
73 list_del_init(&child
->ptrace_entry
);
75 if (task_is_traced(child
))
76 ptrace_untrace(child
);
80 * Check that we have indeed attached to the thing..
82 int ptrace_check_attach(struct task_struct
*child
, int kill
)
87 * We take the read lock around doing both checks to close a
88 * possible race where someone else was tracing our child and
89 * detached between these two checks. After this locked check,
90 * we are sure that this is our traced child and that can only
91 * be changed by us so it's not changing right after this.
93 read_lock(&tasklist_lock
);
94 if ((child
->ptrace
& PT_PTRACED
) && child
->parent
== current
) {
97 * child->sighand can't be NULL, release_task()
98 * does ptrace_unlink() before __exit_signal().
100 spin_lock_irq(&child
->sighand
->siglock
);
101 if (task_is_stopped(child
))
102 child
->state
= TASK_TRACED
;
103 else if (!task_is_traced(child
) && !kill
)
105 spin_unlock_irq(&child
->sighand
->siglock
);
107 read_unlock(&tasklist_lock
);
110 ret
= wait_task_inactive(child
, TASK_TRACED
) ? 0 : -ESRCH
;
112 /* All systems go.. */
116 int __ptrace_may_access(struct task_struct
*task
, unsigned int mode
)
118 /* May we inspect the given task?
119 * This check is used both for attaching with ptrace
120 * and for allowing access to sensitive information in /proc.
122 * ptrace_attach denies several cases that /proc allows
123 * because setting up the necessary parent/child relationship
124 * or halting the specified task is impossible.
129 /* Don't let security modules deny introspection */
132 current_uid_gid(&uid
, &gid
);
133 if ((uid
!= task
->euid
||
138 gid
!= task
->gid
) && !capable(CAP_SYS_PTRACE
))
142 dumpable
= get_dumpable(task
->mm
);
143 if (!dumpable
&& !capable(CAP_SYS_PTRACE
))
146 return security_ptrace_may_access(task
, mode
);
149 bool ptrace_may_access(struct task_struct
*task
, unsigned int mode
)
153 err
= __ptrace_may_access(task
, mode
);
155 return (!err
? true : false);
158 int ptrace_attach(struct task_struct
*task
)
166 if (same_thread_group(task
, current
))
173 * We want to hold both the task-lock and the
174 * tasklist_lock for writing at the same time.
175 * But that's against the rules (tasklist_lock
176 * is taken for reading by interrupts on other
177 * cpu's that may have task_lock).
180 if (!write_trylock_irqsave(&tasklist_lock
, flags
)) {
184 } while (!write_can_lock(&tasklist_lock
));
190 /* the same process cannot be attached many times */
191 if (task
->ptrace
& PT_PTRACED
)
193 retval
= __ptrace_may_access(task
, PTRACE_MODE_ATTACH
);
198 task
->ptrace
|= PT_PTRACED
;
199 if (capable(CAP_SYS_PTRACE
))
200 task
->ptrace
|= PT_PTRACE_CAP
;
202 __ptrace_link(task
, current
);
204 send_sig_info(SIGSTOP
, SEND_SIG_FORCED
, task
);
206 write_unlock_irqrestore(&tasklist_lock
, flags
);
212 static inline void __ptrace_detach(struct task_struct
*child
, unsigned int data
)
214 child
->exit_code
= data
;
215 /* .. re-parent .. */
216 __ptrace_unlink(child
);
217 /* .. and wake it up. */
218 if (child
->exit_state
!= EXIT_ZOMBIE
)
219 wake_up_process(child
);
222 int ptrace_detach(struct task_struct
*child
, unsigned int data
)
224 if (!valid_signal(data
))
227 /* Architecture-specific hardware disable .. */
228 ptrace_disable(child
);
229 clear_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
231 write_lock_irq(&tasklist_lock
);
232 /* protect against de_thread()->release_task() */
234 __ptrace_detach(child
, data
);
235 write_unlock_irq(&tasklist_lock
);
240 int ptrace_readdata(struct task_struct
*tsk
, unsigned long src
, char __user
*dst
, int len
)
246 int this_len
, retval
;
248 this_len
= (len
> sizeof(buf
)) ? sizeof(buf
) : len
;
249 retval
= access_process_vm(tsk
, src
, buf
, this_len
, 0);
255 if (copy_to_user(dst
, buf
, retval
))
265 int ptrace_writedata(struct task_struct
*tsk
, char __user
*src
, unsigned long dst
, int len
)
271 int this_len
, retval
;
273 this_len
= (len
> sizeof(buf
)) ? sizeof(buf
) : len
;
274 if (copy_from_user(buf
, src
, this_len
))
276 retval
= access_process_vm(tsk
, dst
, buf
, this_len
, 1);
290 static int ptrace_setoptions(struct task_struct
*child
, long data
)
292 child
->ptrace
&= ~PT_TRACE_MASK
;
294 if (data
& PTRACE_O_TRACESYSGOOD
)
295 child
->ptrace
|= PT_TRACESYSGOOD
;
297 if (data
& PTRACE_O_TRACEFORK
)
298 child
->ptrace
|= PT_TRACE_FORK
;
300 if (data
& PTRACE_O_TRACEVFORK
)
301 child
->ptrace
|= PT_TRACE_VFORK
;
303 if (data
& PTRACE_O_TRACECLONE
)
304 child
->ptrace
|= PT_TRACE_CLONE
;
306 if (data
& PTRACE_O_TRACEEXEC
)
307 child
->ptrace
|= PT_TRACE_EXEC
;
309 if (data
& PTRACE_O_TRACEVFORKDONE
)
310 child
->ptrace
|= PT_TRACE_VFORK_DONE
;
312 if (data
& PTRACE_O_TRACEEXIT
)
313 child
->ptrace
|= PT_TRACE_EXIT
;
315 return (data
& ~PTRACE_O_MASK
) ? -EINVAL
: 0;
318 static int ptrace_getsiginfo(struct task_struct
*child
, siginfo_t
*info
)
322 read_lock(&tasklist_lock
);
323 if (likely(child
->sighand
!= NULL
)) {
325 spin_lock_irq(&child
->sighand
->siglock
);
326 if (likely(child
->last_siginfo
!= NULL
)) {
327 *info
= *child
->last_siginfo
;
330 spin_unlock_irq(&child
->sighand
->siglock
);
332 read_unlock(&tasklist_lock
);
336 static int ptrace_setsiginfo(struct task_struct
*child
, const siginfo_t
*info
)
340 read_lock(&tasklist_lock
);
341 if (likely(child
->sighand
!= NULL
)) {
343 spin_lock_irq(&child
->sighand
->siglock
);
344 if (likely(child
->last_siginfo
!= NULL
)) {
345 *child
->last_siginfo
= *info
;
348 spin_unlock_irq(&child
->sighand
->siglock
);
350 read_unlock(&tasklist_lock
);
355 #ifdef PTRACE_SINGLESTEP
356 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
358 #define is_singlestep(request) 0
361 #ifdef PTRACE_SINGLEBLOCK
362 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
364 #define is_singleblock(request) 0
368 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
370 #define is_sysemu_singlestep(request) 0
373 static int ptrace_resume(struct task_struct
*child
, long request
, long data
)
375 if (!valid_signal(data
))
378 if (request
== PTRACE_SYSCALL
)
379 set_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
381 clear_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
383 #ifdef TIF_SYSCALL_EMU
384 if (request
== PTRACE_SYSEMU
|| request
== PTRACE_SYSEMU_SINGLESTEP
)
385 set_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
387 clear_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
390 if (is_singleblock(request
)) {
391 if (unlikely(!arch_has_block_step()))
393 user_enable_block_step(child
);
394 } else if (is_singlestep(request
) || is_sysemu_singlestep(request
)) {
395 if (unlikely(!arch_has_single_step()))
397 user_enable_single_step(child
);
400 user_disable_single_step(child
);
402 child
->exit_code
= data
;
403 wake_up_process(child
);
408 int ptrace_request(struct task_struct
*child
, long request
,
409 long addr
, long data
)
415 case PTRACE_PEEKTEXT
:
416 case PTRACE_PEEKDATA
:
417 return generic_ptrace_peekdata(child
, addr
, data
);
418 case PTRACE_POKETEXT
:
419 case PTRACE_POKEDATA
:
420 return generic_ptrace_pokedata(child
, addr
, data
);
422 #ifdef PTRACE_OLDSETOPTIONS
423 case PTRACE_OLDSETOPTIONS
:
425 case PTRACE_SETOPTIONS
:
426 ret
= ptrace_setoptions(child
, data
);
428 case PTRACE_GETEVENTMSG
:
429 ret
= put_user(child
->ptrace_message
, (unsigned long __user
*) data
);
432 case PTRACE_GETSIGINFO
:
433 ret
= ptrace_getsiginfo(child
, &siginfo
);
435 ret
= copy_siginfo_to_user((siginfo_t __user
*) data
,
439 case PTRACE_SETSIGINFO
:
440 if (copy_from_user(&siginfo
, (siginfo_t __user
*) data
,
444 ret
= ptrace_setsiginfo(child
, &siginfo
);
447 case PTRACE_DETACH
: /* detach a process that was attached. */
448 ret
= ptrace_detach(child
, data
);
451 #ifdef PTRACE_SINGLESTEP
452 case PTRACE_SINGLESTEP
:
454 #ifdef PTRACE_SINGLEBLOCK
455 case PTRACE_SINGLEBLOCK
:
459 case PTRACE_SYSEMU_SINGLESTEP
:
463 return ptrace_resume(child
, request
, data
);
466 if (child
->exit_state
) /* already dead */
468 return ptrace_resume(child
, request
, SIGKILL
);
478 * ptrace_traceme -- helper for PTRACE_TRACEME
480 * Performs checks and sets PT_PTRACED.
481 * Should be used by all ptrace implementations for PTRACE_TRACEME.
483 int ptrace_traceme(void)
488 * Are we already being traced?
492 if (!(current
->ptrace
& PT_PTRACED
)) {
494 * See ptrace_attach() comments about the locking here.
497 if (!write_trylock_irqsave(&tasklist_lock
, flags
)) {
498 task_unlock(current
);
501 } while (!write_can_lock(&tasklist_lock
));
505 ret
= security_ptrace_traceme(current
->parent
);
508 * Set the ptrace bit in the process ptrace flags.
509 * Then link us on our parent's ptraced list.
512 current
->ptrace
|= PT_PTRACED
;
513 __ptrace_link(current
, current
->real_parent
);
516 write_unlock_irqrestore(&tasklist_lock
, flags
);
518 task_unlock(current
);
523 * ptrace_get_task_struct -- grab a task struct reference for ptrace
524 * @pid: process id to grab a task_struct reference of
526 * This function is a helper for ptrace implementations. It checks
527 * permissions and then grabs a task struct for use of the actual
528 * ptrace implementation.
530 * Returns the task_struct for @pid or an ERR_PTR() on failure.
532 struct task_struct
*ptrace_get_task_struct(pid_t pid
)
534 struct task_struct
*child
;
536 read_lock(&tasklist_lock
);
537 child
= find_task_by_vpid(pid
);
539 get_task_struct(child
);
541 read_unlock(&tasklist_lock
);
543 return ERR_PTR(-ESRCH
);
547 #ifndef arch_ptrace_attach
548 #define arch_ptrace_attach(child) do { } while (0)
551 asmlinkage
long sys_ptrace(long request
, long pid
, long addr
, long data
)
553 struct task_struct
*child
;
557 * This lock_kernel fixes a subtle race with suid exec
560 if (request
== PTRACE_TRACEME
) {
561 ret
= ptrace_traceme();
563 arch_ptrace_attach(current
);
567 child
= ptrace_get_task_struct(pid
);
569 ret
= PTR_ERR(child
);
573 if (request
== PTRACE_ATTACH
) {
574 ret
= ptrace_attach(child
);
576 * Some architectures need to do book-keeping after
580 arch_ptrace_attach(child
);
581 goto out_put_task_struct
;
584 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
586 goto out_put_task_struct
;
588 ret
= arch_ptrace(child
, request
, addr
, data
);
590 goto out_put_task_struct
;
593 put_task_struct(child
);
599 int generic_ptrace_peekdata(struct task_struct
*tsk
, long addr
, long data
)
604 copied
= access_process_vm(tsk
, addr
, &tmp
, sizeof(tmp
), 0);
605 if (copied
!= sizeof(tmp
))
607 return put_user(tmp
, (unsigned long __user
*)data
);
610 int generic_ptrace_pokedata(struct task_struct
*tsk
, long addr
, long data
)
614 copied
= access_process_vm(tsk
, addr
, &data
, sizeof(data
), 1);
615 return (copied
== sizeof(data
)) ? 0 : -EIO
;
618 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
619 #include <linux/compat.h>
621 int compat_ptrace_request(struct task_struct
*child
, compat_long_t request
,
622 compat_ulong_t addr
, compat_ulong_t data
)
624 compat_ulong_t __user
*datap
= compat_ptr(data
);
630 case PTRACE_PEEKTEXT
:
631 case PTRACE_PEEKDATA
:
632 ret
= access_process_vm(child
, addr
, &word
, sizeof(word
), 0);
633 if (ret
!= sizeof(word
))
636 ret
= put_user(word
, datap
);
639 case PTRACE_POKETEXT
:
640 case PTRACE_POKEDATA
:
641 ret
= access_process_vm(child
, addr
, &data
, sizeof(data
), 1);
642 ret
= (ret
!= sizeof(data
) ? -EIO
: 0);
645 case PTRACE_GETEVENTMSG
:
646 ret
= put_user((compat_ulong_t
) child
->ptrace_message
, datap
);
649 case PTRACE_GETSIGINFO
:
650 ret
= ptrace_getsiginfo(child
, &siginfo
);
652 ret
= copy_siginfo_to_user32(
653 (struct compat_siginfo __user
*) datap
,
657 case PTRACE_SETSIGINFO
:
658 memset(&siginfo
, 0, sizeof siginfo
);
659 if (copy_siginfo_from_user32(
660 &siginfo
, (struct compat_siginfo __user
*) datap
))
663 ret
= ptrace_setsiginfo(child
, &siginfo
);
667 ret
= ptrace_request(child
, request
, addr
, data
);
673 asmlinkage
long compat_sys_ptrace(compat_long_t request
, compat_long_t pid
,
674 compat_long_t addr
, compat_long_t data
)
676 struct task_struct
*child
;
680 * This lock_kernel fixes a subtle race with suid exec
683 if (request
== PTRACE_TRACEME
) {
684 ret
= ptrace_traceme();
688 child
= ptrace_get_task_struct(pid
);
690 ret
= PTR_ERR(child
);
694 if (request
== PTRACE_ATTACH
) {
695 ret
= ptrace_attach(child
);
697 * Some architectures need to do book-keeping after
701 arch_ptrace_attach(child
);
702 goto out_put_task_struct
;
705 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
707 ret
= compat_arch_ptrace(child
, request
, addr
, data
);
710 put_task_struct(child
);
715 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */
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