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>
24 #include <asm/pgtable.h>
25 #include <asm/uaccess.h>
28 * ptrace a task: make the debugger its new parent and
29 * move it to the ptrace list.
31 * Must be called with the tasklist lock write-held.
33 void __ptrace_link(struct task_struct
*child
, struct task_struct
*new_parent
)
35 BUG_ON(!list_empty(&child
->ptrace_list
));
36 if (child
->parent
== new_parent
)
38 list_add(&child
->ptrace_list
, &child
->parent
->ptrace_children
);
40 child
->parent
= new_parent
;
45 * Turn a tracing stop into a normal stop now, since with no tracer there
46 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
47 * signal sent that would resume the child, but didn't because it was in
48 * TASK_TRACED, resume it now.
49 * Requires that irqs be disabled.
51 void ptrace_untrace(struct task_struct
*child
)
53 spin_lock(&child
->sighand
->siglock
);
54 if (task_is_traced(child
)) {
55 if (child
->signal
->flags
& SIGNAL_STOP_STOPPED
) {
56 child
->state
= TASK_STOPPED
;
58 signal_wake_up(child
, 1);
61 spin_unlock(&child
->sighand
->siglock
);
65 * unptrace a task: move it back to its original parent and
66 * remove it from the ptrace list.
68 * Must be called with the tasklist lock write-held.
70 void __ptrace_unlink(struct task_struct
*child
)
72 BUG_ON(!child
->ptrace
);
75 if (!list_empty(&child
->ptrace_list
)) {
76 list_del_init(&child
->ptrace_list
);
78 child
->parent
= child
->real_parent
;
82 if (task_is_traced(child
))
83 ptrace_untrace(child
);
87 * Check that we have indeed attached to the thing..
89 int ptrace_check_attach(struct task_struct
*child
, int kill
)
94 * We take the read lock around doing both checks to close a
95 * possible race where someone else was tracing our child and
96 * detached between these two checks. After this locked check,
97 * we are sure that this is our traced child and that can only
98 * be changed by us so it's not changing right after this.
100 read_lock(&tasklist_lock
);
101 if ((child
->ptrace
& PT_PTRACED
) && child
->parent
== current
&&
102 (!(child
->ptrace
& PT_ATTACHED
) || child
->real_parent
!= current
)
103 && child
->signal
!= NULL
) {
105 spin_lock_irq(&child
->sighand
->siglock
);
106 if (task_is_stopped(child
)) {
107 child
->state
= TASK_TRACED
;
108 } else if (!task_is_traced(child
) && !kill
) {
111 spin_unlock_irq(&child
->sighand
->siglock
);
113 read_unlock(&tasklist_lock
);
116 wait_task_inactive(child
);
119 /* All systems go.. */
123 int __ptrace_may_attach(struct task_struct
*task
)
125 /* May we inspect the given task?
126 * This check is used both for attaching with ptrace
127 * and for allowing access to sensitive information in /proc.
129 * ptrace_attach denies several cases that /proc allows
130 * because setting up the necessary parent/child relationship
131 * or halting the specified task is impossible.
134 /* Don't let security modules deny introspection */
137 if (((current
->uid
!= task
->euid
) ||
138 (current
->uid
!= task
->suid
) ||
139 (current
->uid
!= task
->uid
) ||
140 (current
->gid
!= task
->egid
) ||
141 (current
->gid
!= task
->sgid
) ||
142 (current
->gid
!= task
->gid
)) && !capable(CAP_SYS_PTRACE
))
146 dumpable
= get_dumpable(task
->mm
);
147 if (!dumpable
&& !capable(CAP_SYS_PTRACE
))
150 return security_ptrace(current
, task
);
153 int ptrace_may_attach(struct task_struct
*task
)
157 err
= __ptrace_may_attach(task
);
162 int ptrace_attach(struct task_struct
*task
)
172 if (same_thread_group(task
, current
))
179 * We want to hold both the task-lock and the
180 * tasklist_lock for writing at the same time.
181 * But that's against the rules (tasklist_lock
182 * is taken for reading by interrupts on other
183 * cpu's that may have task_lock).
186 if (!write_trylock_irqsave(&tasklist_lock
, flags
)) {
190 } while (!write_can_lock(&tasklist_lock
));
196 /* the same process cannot be attached many times */
197 if (task
->ptrace
& PT_PTRACED
)
199 retval
= __ptrace_may_attach(task
);
204 task
->ptrace
|= PT_PTRACED
| ((task
->real_parent
!= current
)
206 if (capable(CAP_SYS_PTRACE
))
207 task
->ptrace
|= PT_PTRACE_CAP
;
209 __ptrace_link(task
, current
);
211 force_sig_specific(SIGSTOP
, task
);
214 write_unlock_irqrestore(&tasklist_lock
, flags
);
220 static inline void __ptrace_detach(struct task_struct
*child
, unsigned int data
)
222 child
->exit_code
= data
;
223 /* .. re-parent .. */
224 __ptrace_unlink(child
);
225 /* .. and wake it up. */
226 if (child
->exit_state
!= EXIT_ZOMBIE
)
227 wake_up_process(child
);
230 int ptrace_detach(struct task_struct
*child
, unsigned int data
)
232 if (!valid_signal(data
))
235 /* Architecture-specific hardware disable .. */
236 ptrace_disable(child
);
237 clear_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
239 write_lock_irq(&tasklist_lock
);
240 /* protect against de_thread()->release_task() */
242 __ptrace_detach(child
, data
);
243 write_unlock_irq(&tasklist_lock
);
248 int ptrace_readdata(struct task_struct
*tsk
, unsigned long src
, char __user
*dst
, int len
)
254 int this_len
, retval
;
256 this_len
= (len
> sizeof(buf
)) ? sizeof(buf
) : len
;
257 retval
= access_process_vm(tsk
, src
, buf
, this_len
, 0);
263 if (copy_to_user(dst
, buf
, retval
))
273 int ptrace_writedata(struct task_struct
*tsk
, char __user
*src
, unsigned long dst
, int len
)
279 int this_len
, retval
;
281 this_len
= (len
> sizeof(buf
)) ? sizeof(buf
) : len
;
282 if (copy_from_user(buf
, src
, this_len
))
284 retval
= access_process_vm(tsk
, dst
, buf
, this_len
, 1);
298 static int ptrace_setoptions(struct task_struct
*child
, long data
)
300 child
->ptrace
&= ~PT_TRACE_MASK
;
302 if (data
& PTRACE_O_TRACESYSGOOD
)
303 child
->ptrace
|= PT_TRACESYSGOOD
;
305 if (data
& PTRACE_O_TRACEFORK
)
306 child
->ptrace
|= PT_TRACE_FORK
;
308 if (data
& PTRACE_O_TRACEVFORK
)
309 child
->ptrace
|= PT_TRACE_VFORK
;
311 if (data
& PTRACE_O_TRACECLONE
)
312 child
->ptrace
|= PT_TRACE_CLONE
;
314 if (data
& PTRACE_O_TRACEEXEC
)
315 child
->ptrace
|= PT_TRACE_EXEC
;
317 if (data
& PTRACE_O_TRACEVFORKDONE
)
318 child
->ptrace
|= PT_TRACE_VFORK_DONE
;
320 if (data
& PTRACE_O_TRACEEXIT
)
321 child
->ptrace
|= PT_TRACE_EXIT
;
323 return (data
& ~PTRACE_O_MASK
) ? -EINVAL
: 0;
326 static int ptrace_getsiginfo(struct task_struct
*child
, siginfo_t __user
* data
)
331 read_lock(&tasklist_lock
);
332 if (likely(child
->sighand
!= NULL
)) {
334 spin_lock_irq(&child
->sighand
->siglock
);
335 if (likely(child
->last_siginfo
!= NULL
)) {
336 lastinfo
= *child
->last_siginfo
;
339 spin_unlock_irq(&child
->sighand
->siglock
);
341 read_unlock(&tasklist_lock
);
343 return copy_siginfo_to_user(data
, &lastinfo
);
347 static int ptrace_setsiginfo(struct task_struct
*child
, siginfo_t __user
* data
)
352 if (copy_from_user(&newinfo
, data
, sizeof (siginfo_t
)))
355 read_lock(&tasklist_lock
);
356 if (likely(child
->sighand
!= NULL
)) {
358 spin_lock_irq(&child
->sighand
->siglock
);
359 if (likely(child
->last_siginfo
!= NULL
)) {
360 *child
->last_siginfo
= newinfo
;
363 spin_unlock_irq(&child
->sighand
->siglock
);
365 read_unlock(&tasklist_lock
);
370 #ifdef PTRACE_SINGLESTEP
371 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
373 #define is_singlestep(request) 0
376 #ifdef PTRACE_SINGLEBLOCK
377 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
379 #define is_singleblock(request) 0
383 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
385 #define is_sysemu_singlestep(request) 0
388 static int ptrace_resume(struct task_struct
*child
, long request
, long data
)
390 if (!valid_signal(data
))
393 if (request
== PTRACE_SYSCALL
)
394 set_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
396 clear_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
398 #ifdef TIF_SYSCALL_EMU
399 if (request
== PTRACE_SYSEMU
|| request
== PTRACE_SYSEMU_SINGLESTEP
)
400 set_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
402 clear_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
405 if (is_singleblock(request
)) {
406 if (unlikely(!arch_has_block_step()))
408 user_enable_block_step(child
);
409 } else if (is_singlestep(request
) || is_sysemu_singlestep(request
)) {
410 if (unlikely(!arch_has_single_step()))
412 user_enable_single_step(child
);
415 user_disable_single_step(child
);
417 child
->exit_code
= data
;
418 wake_up_process(child
);
423 int ptrace_request(struct task_struct
*child
, long request
,
424 long addr
, long data
)
429 case PTRACE_PEEKTEXT
:
430 case PTRACE_PEEKDATA
:
431 return generic_ptrace_peekdata(child
, addr
, data
);
432 case PTRACE_POKETEXT
:
433 case PTRACE_POKEDATA
:
434 return generic_ptrace_pokedata(child
, addr
, data
);
436 #ifdef PTRACE_OLDSETOPTIONS
437 case PTRACE_OLDSETOPTIONS
:
439 case PTRACE_SETOPTIONS
:
440 ret
= ptrace_setoptions(child
, data
);
442 case PTRACE_GETEVENTMSG
:
443 ret
= put_user(child
->ptrace_message
, (unsigned long __user
*) data
);
445 case PTRACE_GETSIGINFO
:
446 ret
= ptrace_getsiginfo(child
, (siginfo_t __user
*) data
);
448 case PTRACE_SETSIGINFO
:
449 ret
= ptrace_setsiginfo(child
, (siginfo_t __user
*) data
);
451 case PTRACE_DETACH
: /* detach a process that was attached. */
452 ret
= ptrace_detach(child
, data
);
455 #ifdef PTRACE_SINGLESTEP
456 case PTRACE_SINGLESTEP
:
458 #ifdef PTRACE_SINGLEBLOCK
459 case PTRACE_SINGLEBLOCK
:
463 case PTRACE_SYSEMU_SINGLESTEP
:
467 return ptrace_resume(child
, request
, data
);
470 if (child
->exit_state
) /* already dead */
472 return ptrace_resume(child
, request
, SIGKILL
);
482 * ptrace_traceme -- helper for PTRACE_TRACEME
484 * Performs checks and sets PT_PTRACED.
485 * Should be used by all ptrace implementations for PTRACE_TRACEME.
487 int ptrace_traceme(void)
492 * Are we already being traced?
495 if (!(current
->ptrace
& PT_PTRACED
)) {
496 ret
= security_ptrace(current
->parent
, current
);
498 * Set the ptrace bit in the process ptrace flags.
501 current
->ptrace
|= PT_PTRACED
;
503 task_unlock(current
);
508 * ptrace_get_task_struct -- grab a task struct reference for ptrace
509 * @pid: process id to grab a task_struct reference of
511 * This function is a helper for ptrace implementations. It checks
512 * permissions and then grabs a task struct for use of the actual
513 * ptrace implementation.
515 * Returns the task_struct for @pid or an ERR_PTR() on failure.
517 struct task_struct
*ptrace_get_task_struct(pid_t pid
)
519 struct task_struct
*child
;
522 * Tracing init is not allowed.
525 return ERR_PTR(-EPERM
);
527 read_lock(&tasklist_lock
);
528 child
= find_task_by_vpid(pid
);
530 get_task_struct(child
);
532 read_unlock(&tasklist_lock
);
534 return ERR_PTR(-ESRCH
);
538 #ifndef arch_ptrace_attach
539 #define arch_ptrace_attach(child) do { } while (0)
542 #ifndef __ARCH_SYS_PTRACE
543 asmlinkage
long sys_ptrace(long request
, long pid
, long addr
, long data
)
545 struct task_struct
*child
;
549 * This lock_kernel fixes a subtle race with suid exec
552 if (request
== PTRACE_TRACEME
) {
553 ret
= ptrace_traceme();
555 arch_ptrace_attach(current
);
559 child
= ptrace_get_task_struct(pid
);
561 ret
= PTR_ERR(child
);
565 if (request
== PTRACE_ATTACH
) {
566 ret
= ptrace_attach(child
);
568 * Some architectures need to do book-keeping after
572 arch_ptrace_attach(child
);
573 goto out_put_task_struct
;
576 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
578 goto out_put_task_struct
;
580 ret
= arch_ptrace(child
, request
, addr
, data
);
582 goto out_put_task_struct
;
585 put_task_struct(child
);
590 #endif /* __ARCH_SYS_PTRACE */
592 int generic_ptrace_peekdata(struct task_struct
*tsk
, long addr
, long data
)
597 copied
= access_process_vm(tsk
, addr
, &tmp
, sizeof(tmp
), 0);
598 if (copied
!= sizeof(tmp
))
600 return put_user(tmp
, (unsigned long __user
*)data
);
603 int generic_ptrace_pokedata(struct task_struct
*tsk
, long addr
, long data
)
607 copied
= access_process_vm(tsk
, addr
, &data
, sizeof(data
), 1);
608 return (copied
== sizeof(data
)) ? 0 : -EIO
;
612 #include <linux/compat.h>
614 int compat_ptrace_request(struct task_struct
*child
, compat_long_t request
,
615 compat_ulong_t addr
, compat_ulong_t data
)
617 compat_ulong_t __user
*datap
= compat_ptr(data
);
622 case PTRACE_PEEKTEXT
:
623 case PTRACE_PEEKDATA
:
624 ret
= access_process_vm(child
, addr
, &word
, sizeof(word
), 0);
625 if (ret
!= sizeof(word
))
628 ret
= put_user(word
, datap
);
631 case PTRACE_POKETEXT
:
632 case PTRACE_POKEDATA
:
633 ret
= access_process_vm(child
, addr
, &data
, sizeof(data
), 1);
634 ret
= (ret
!= sizeof(data
) ? -EIO
: 0);
637 case PTRACE_GETEVENTMSG
:
638 ret
= put_user((compat_ulong_t
) child
->ptrace_message
, datap
);
642 ret
= ptrace_request(child
, request
, addr
, data
);
648 #ifdef __ARCH_WANT_COMPAT_SYS_PTRACE
649 asmlinkage
long compat_sys_ptrace(compat_long_t request
, compat_long_t pid
,
650 compat_long_t addr
, compat_long_t data
)
652 struct task_struct
*child
;
656 * This lock_kernel fixes a subtle race with suid exec
659 if (request
== PTRACE_TRACEME
) {
660 ret
= ptrace_traceme();
664 child
= ptrace_get_task_struct(pid
);
666 ret
= PTR_ERR(child
);
670 if (request
== PTRACE_ATTACH
) {
671 ret
= ptrace_attach(child
);
673 * Some architectures need to do book-keeping after
677 arch_ptrace_attach(child
);
678 goto out_put_task_struct
;
681 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
683 ret
= compat_arch_ptrace(child
, request
, addr
, data
);
686 put_task_struct(child
);
691 #endif /* __ARCH_WANT_COMPAT_SYS_PTRACE */
693 #endif /* CONFIG_COMPAT */