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_list
));
37 if (child
->parent
== new_parent
)
39 list_add(&child
->ptrace_list
, &child
->parent
->ptrace_children
);
41 child
->parent
= new_parent
;
46 * Turn a tracing stop into a normal stop now, since with no tracer there
47 * would be no way to wake it up with SIGCONT or SIGKILL. If there was a
48 * signal sent that would resume the child, but didn't because it was in
49 * TASK_TRACED, resume it now.
50 * Requires that irqs be disabled.
52 void ptrace_untrace(struct task_struct
*child
)
54 spin_lock(&child
->sighand
->siglock
);
55 if (task_is_traced(child
)) {
56 if (child
->signal
->flags
& SIGNAL_STOP_STOPPED
) {
57 __set_task_state(child
, TASK_STOPPED
);
59 signal_wake_up(child
, 1);
62 spin_unlock(&child
->sighand
->siglock
);
66 * unptrace a task: move it back to its original parent and
67 * remove it from the ptrace list.
69 * Must be called with the tasklist lock write-held.
71 void __ptrace_unlink(struct task_struct
*child
)
73 BUG_ON(!child
->ptrace
);
76 if (!list_empty(&child
->ptrace_list
)) {
77 list_del_init(&child
->ptrace_list
);
79 child
->parent
= child
->real_parent
;
83 if (task_is_traced(child
))
84 ptrace_untrace(child
);
88 * Check that we have indeed attached to the thing..
90 int ptrace_check_attach(struct task_struct
*child
, int kill
)
95 * We take the read lock around doing both checks to close a
96 * possible race where someone else was tracing our child and
97 * detached between these two checks. After this locked check,
98 * we are sure that this is our traced child and that can only
99 * be changed by us so it's not changing right after this.
101 read_lock(&tasklist_lock
);
102 if ((child
->ptrace
& PT_PTRACED
) && child
->parent
== current
) {
105 * child->sighand can't be NULL, release_task()
106 * does ptrace_unlink() before __exit_signal().
108 spin_lock_irq(&child
->sighand
->siglock
);
109 if (task_is_stopped(child
))
110 child
->state
= TASK_TRACED
;
111 else if (!task_is_traced(child
) && !kill
)
113 spin_unlock_irq(&child
->sighand
->siglock
);
115 read_unlock(&tasklist_lock
);
118 wait_task_inactive(child
);
120 /* All systems go.. */
124 int __ptrace_may_attach(struct task_struct
*task
)
126 /* May we inspect the given task?
127 * This check is used both for attaching with ptrace
128 * and for allowing access to sensitive information in /proc.
130 * ptrace_attach denies several cases that /proc allows
131 * because setting up the necessary parent/child relationship
132 * or halting the specified task is impossible.
135 /* Don't let security modules deny introspection */
138 if (((current
->uid
!= task
->euid
) ||
139 (current
->uid
!= task
->suid
) ||
140 (current
->uid
!= task
->uid
) ||
141 (current
->gid
!= task
->egid
) ||
142 (current
->gid
!= task
->sgid
) ||
143 (current
->gid
!= task
->gid
)) && !capable(CAP_SYS_PTRACE
))
147 dumpable
= get_dumpable(task
->mm
);
148 if (!dumpable
&& !capable(CAP_SYS_PTRACE
))
151 return security_ptrace(current
, task
);
154 int ptrace_may_attach(struct task_struct
*task
)
158 err
= __ptrace_may_attach(task
);
163 int ptrace_attach(struct task_struct
*task
)
173 if (same_thread_group(task
, current
))
180 * We want to hold both the task-lock and the
181 * tasklist_lock for writing at the same time.
182 * But that's against the rules (tasklist_lock
183 * is taken for reading by interrupts on other
184 * cpu's that may have task_lock).
187 if (!write_trylock_irqsave(&tasklist_lock
, flags
)) {
191 } while (!write_can_lock(&tasklist_lock
));
197 /* the same process cannot be attached many times */
198 if (task
->ptrace
& PT_PTRACED
)
200 retval
= __ptrace_may_attach(task
);
205 task
->ptrace
|= PT_PTRACED
;
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
*info
)
330 read_lock(&tasklist_lock
);
331 if (likely(child
->sighand
!= NULL
)) {
333 spin_lock_irq(&child
->sighand
->siglock
);
334 if (likely(child
->last_siginfo
!= NULL
)) {
335 *info
= *child
->last_siginfo
;
338 spin_unlock_irq(&child
->sighand
->siglock
);
340 read_unlock(&tasklist_lock
);
344 static int ptrace_setsiginfo(struct task_struct
*child
, const siginfo_t
*info
)
348 read_lock(&tasklist_lock
);
349 if (likely(child
->sighand
!= NULL
)) {
351 spin_lock_irq(&child
->sighand
->siglock
);
352 if (likely(child
->last_siginfo
!= NULL
)) {
353 *child
->last_siginfo
= *info
;
356 spin_unlock_irq(&child
->sighand
->siglock
);
358 read_unlock(&tasklist_lock
);
363 #ifdef PTRACE_SINGLESTEP
364 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
366 #define is_singlestep(request) 0
369 #ifdef PTRACE_SINGLEBLOCK
370 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
372 #define is_singleblock(request) 0
376 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
378 #define is_sysemu_singlestep(request) 0
381 static int ptrace_resume(struct task_struct
*child
, long request
, long data
)
383 if (!valid_signal(data
))
386 if (request
== PTRACE_SYSCALL
)
387 set_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
389 clear_tsk_thread_flag(child
, TIF_SYSCALL_TRACE
);
391 #ifdef TIF_SYSCALL_EMU
392 if (request
== PTRACE_SYSEMU
|| request
== PTRACE_SYSEMU_SINGLESTEP
)
393 set_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
395 clear_tsk_thread_flag(child
, TIF_SYSCALL_EMU
);
398 if (is_singleblock(request
)) {
399 if (unlikely(!arch_has_block_step()))
401 user_enable_block_step(child
);
402 } else if (is_singlestep(request
) || is_sysemu_singlestep(request
)) {
403 if (unlikely(!arch_has_single_step()))
405 user_enable_single_step(child
);
408 user_disable_single_step(child
);
410 child
->exit_code
= data
;
411 wake_up_process(child
);
416 int ptrace_request(struct task_struct
*child
, long request
,
417 long addr
, long data
)
423 case PTRACE_PEEKTEXT
:
424 case PTRACE_PEEKDATA
:
425 return generic_ptrace_peekdata(child
, addr
, data
);
426 case PTRACE_POKETEXT
:
427 case PTRACE_POKEDATA
:
428 return generic_ptrace_pokedata(child
, addr
, data
);
430 #ifdef PTRACE_OLDSETOPTIONS
431 case PTRACE_OLDSETOPTIONS
:
433 case PTRACE_SETOPTIONS
:
434 ret
= ptrace_setoptions(child
, data
);
436 case PTRACE_GETEVENTMSG
:
437 ret
= put_user(child
->ptrace_message
, (unsigned long __user
*) data
);
440 case PTRACE_GETSIGINFO
:
441 ret
= ptrace_getsiginfo(child
, &siginfo
);
443 ret
= copy_siginfo_to_user((siginfo_t __user
*) data
,
447 case PTRACE_SETSIGINFO
:
448 if (copy_from_user(&siginfo
, (siginfo_t __user
*) data
,
452 ret
= ptrace_setsiginfo(child
, &siginfo
);
455 case PTRACE_DETACH
: /* detach a process that was attached. */
456 ret
= ptrace_detach(child
, data
);
459 #ifdef PTRACE_SINGLESTEP
460 case PTRACE_SINGLESTEP
:
462 #ifdef PTRACE_SINGLEBLOCK
463 case PTRACE_SINGLEBLOCK
:
467 case PTRACE_SYSEMU_SINGLESTEP
:
471 return ptrace_resume(child
, request
, data
);
474 if (child
->exit_state
) /* already dead */
476 return ptrace_resume(child
, request
, SIGKILL
);
486 * ptrace_traceme -- helper for PTRACE_TRACEME
488 * Performs checks and sets PT_PTRACED.
489 * Should be used by all ptrace implementations for PTRACE_TRACEME.
491 int ptrace_traceme(void)
496 * Are we already being traced?
499 if (!(current
->ptrace
& PT_PTRACED
)) {
500 ret
= security_ptrace(current
->parent
, current
);
502 * Set the ptrace bit in the process ptrace flags.
505 current
->ptrace
|= PT_PTRACED
;
507 task_unlock(current
);
512 * ptrace_get_task_struct -- grab a task struct reference for ptrace
513 * @pid: process id to grab a task_struct reference of
515 * This function is a helper for ptrace implementations. It checks
516 * permissions and then grabs a task struct for use of the actual
517 * ptrace implementation.
519 * Returns the task_struct for @pid or an ERR_PTR() on failure.
521 struct task_struct
*ptrace_get_task_struct(pid_t pid
)
523 struct task_struct
*child
;
526 * Tracing init is not allowed.
529 return ERR_PTR(-EPERM
);
531 read_lock(&tasklist_lock
);
532 child
= find_task_by_vpid(pid
);
534 get_task_struct(child
);
536 read_unlock(&tasklist_lock
);
538 return ERR_PTR(-ESRCH
);
542 #ifndef arch_ptrace_attach
543 #define arch_ptrace_attach(child) do { } while (0)
546 #ifndef __ARCH_SYS_PTRACE
547 asmlinkage
long sys_ptrace(long request
, long pid
, long addr
, long data
)
549 struct task_struct
*child
;
553 * This lock_kernel fixes a subtle race with suid exec
556 if (request
== PTRACE_TRACEME
) {
557 ret
= ptrace_traceme();
559 arch_ptrace_attach(current
);
563 child
= ptrace_get_task_struct(pid
);
565 ret
= PTR_ERR(child
);
569 if (request
== PTRACE_ATTACH
) {
570 ret
= ptrace_attach(child
);
572 * Some architectures need to do book-keeping after
576 arch_ptrace_attach(child
);
577 goto out_put_task_struct
;
580 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
582 goto out_put_task_struct
;
584 ret
= arch_ptrace(child
, request
, addr
, data
);
586 goto out_put_task_struct
;
589 put_task_struct(child
);
594 #endif /* __ARCH_SYS_PTRACE */
596 int generic_ptrace_peekdata(struct task_struct
*tsk
, long addr
, long data
)
601 copied
= access_process_vm(tsk
, addr
, &tmp
, sizeof(tmp
), 0);
602 if (copied
!= sizeof(tmp
))
604 return put_user(tmp
, (unsigned long __user
*)data
);
607 int generic_ptrace_pokedata(struct task_struct
*tsk
, long addr
, long data
)
611 copied
= access_process_vm(tsk
, addr
, &data
, sizeof(data
), 1);
612 return (copied
== sizeof(data
)) ? 0 : -EIO
;
616 #include <linux/compat.h>
618 int compat_ptrace_request(struct task_struct
*child
, compat_long_t request
,
619 compat_ulong_t addr
, compat_ulong_t data
)
621 compat_ulong_t __user
*datap
= compat_ptr(data
);
627 case PTRACE_PEEKTEXT
:
628 case PTRACE_PEEKDATA
:
629 ret
= access_process_vm(child
, addr
, &word
, sizeof(word
), 0);
630 if (ret
!= sizeof(word
))
633 ret
= put_user(word
, datap
);
636 case PTRACE_POKETEXT
:
637 case PTRACE_POKEDATA
:
638 ret
= access_process_vm(child
, addr
, &data
, sizeof(data
), 1);
639 ret
= (ret
!= sizeof(data
) ? -EIO
: 0);
642 case PTRACE_GETEVENTMSG
:
643 ret
= put_user((compat_ulong_t
) child
->ptrace_message
, datap
);
646 case PTRACE_GETSIGINFO
:
647 ret
= ptrace_getsiginfo(child
, &siginfo
);
649 ret
= copy_siginfo_to_user32(
650 (struct compat_siginfo __user
*) datap
,
654 case PTRACE_SETSIGINFO
:
655 memset(&siginfo
, 0, sizeof siginfo
);
656 if (copy_siginfo_from_user32(
657 &siginfo
, (struct compat_siginfo __user
*) datap
))
660 ret
= ptrace_setsiginfo(child
, &siginfo
);
664 ret
= ptrace_request(child
, request
, addr
, data
);
670 #ifdef __ARCH_WANT_COMPAT_SYS_PTRACE
671 asmlinkage
long compat_sys_ptrace(compat_long_t request
, compat_long_t pid
,
672 compat_long_t addr
, compat_long_t data
)
674 struct task_struct
*child
;
678 * This lock_kernel fixes a subtle race with suid exec
681 if (request
== PTRACE_TRACEME
) {
682 ret
= ptrace_traceme();
686 child
= ptrace_get_task_struct(pid
);
688 ret
= PTR_ERR(child
);
692 if (request
== PTRACE_ATTACH
) {
693 ret
= ptrace_attach(child
);
695 * Some architectures need to do book-keeping after
699 arch_ptrace_attach(child
);
700 goto out_put_task_struct
;
703 ret
= ptrace_check_attach(child
, request
== PTRACE_KILL
);
705 ret
= compat_arch_ptrace(child
, request
, addr
, data
);
708 put_task_struct(child
);
713 #endif /* __ARCH_WANT_COMPAT_SYS_PTRACE */
715 #endif /* CONFIG_COMPAT */
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