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 const struct cred *cred = current_cred(), *tcred;
120 /* May we inspect the given task?
121 * This check is used both for attaching with ptrace
122 * and for allowing access to sensitive information in /proc.
124 * ptrace_attach denies several cases that /proc allows
125 * because setting up the necessary parent/child relationship
126 * or halting the specified task is impossible.
129 /* Don't let security modules deny introspection */
133 tcred = __task_cred(task);
134 if ((cred->uid != tcred->euid ||
135 cred->uid != tcred->suid ||
136 cred->uid != tcred->uid ||
137 cred->gid != tcred->egid ||
138 cred->gid != tcred->sgid ||
139 cred->gid != tcred->gid) &&
140 !capable(CAP_SYS_PTRACE)) {
147 dumpable = get_dumpable(task->mm);
148 if (!dumpable && !capable(CAP_SYS_PTRACE))
151 return security_ptrace_may_access(task, mode);
154 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
158 err = __ptrace_may_access(task, mode);
160 return (!err ? true : false);
163 int ptrace_attach(struct task_struct *task)
171 if (same_thread_group(task, current))
174 /* Protect exec's credential calculations against our interference;
175 * SUID, SGID and LSM creds get determined differently under ptrace.
177 retval = mutex_lock_interruptible(¤t->cred_exec_mutex);
186 * We want to hold both the task-lock and the
187 * tasklist_lock for writing at the same time.
188 * But that's against the rules (tasklist_lock
189 * is taken for reading by interrupts on other
190 * cpu's that may have task_lock).
193 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
197 } while (!write_can_lock(&tasklist_lock));
203 /* the same process cannot be attached many times */
204 if (task->ptrace & PT_PTRACED)
206 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
211 task->ptrace |= PT_PTRACED;
212 if (capable(CAP_SYS_PTRACE))
213 task->ptrace |= PT_PTRACE_CAP;
215 __ptrace_link(task, current);
217 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
219 write_unlock_irqrestore(&tasklist_lock, flags);
221 mutex_unlock(¤t->cred_exec_mutex);
226 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
228 child->exit_code = data;
229 /* .. re-parent .. */
230 __ptrace_unlink(child);
231 /* .. and wake it up. */
232 if (child->exit_state != EXIT_ZOMBIE)
233 wake_up_process(child);
236 int ptrace_detach(struct task_struct *child, unsigned int data)
238 if (!valid_signal(data))
241 /* Architecture-specific hardware disable .. */
242 ptrace_disable(child);
243 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
245 write_lock_irq(&tasklist_lock);
246 /* protect against de_thread()->release_task() */
248 __ptrace_detach(child, data);
249 write_unlock_irq(&tasklist_lock);
254 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
260 int this_len, retval;
262 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
263 retval = access_process_vm(tsk, src, buf, this_len, 0);
269 if (copy_to_user(dst, buf, retval))
279 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
285 int this_len, retval;
287 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
288 if (copy_from_user(buf, src, this_len))
290 retval = access_process_vm(tsk, dst, buf, this_len, 1);
304 static int ptrace_setoptions(struct task_struct *child, long data)
306 child->ptrace &= ~PT_TRACE_MASK;
308 if (data & PTRACE_O_TRACESYSGOOD)
309 child->ptrace |= PT_TRACESYSGOOD;
311 if (data & PTRACE_O_TRACEFORK)
312 child->ptrace |= PT_TRACE_FORK;
314 if (data & PTRACE_O_TRACEVFORK)
315 child->ptrace |= PT_TRACE_VFORK;
317 if (data & PTRACE_O_TRACECLONE)
318 child->ptrace |= PT_TRACE_CLONE;
320 if (data & PTRACE_O_TRACEEXEC)
321 child->ptrace |= PT_TRACE_EXEC;
323 if (data & PTRACE_O_TRACEVFORKDONE)
324 child->ptrace |= PT_TRACE_VFORK_DONE;
326 if (data & PTRACE_O_TRACEEXIT)
327 child->ptrace |= PT_TRACE_EXIT;
329 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
332 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
336 read_lock(&tasklist_lock);
337 if (likely(child->sighand != NULL)) {
339 spin_lock_irq(&child->sighand->siglock);
340 if (likely(child->last_siginfo != NULL)) {
341 *info = *child->last_siginfo;
344 spin_unlock_irq(&child->sighand->siglock);
346 read_unlock(&tasklist_lock);
350 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
354 read_lock(&tasklist_lock);
355 if (likely(child->sighand != NULL)) {
357 spin_lock_irq(&child->sighand->siglock);
358 if (likely(child->last_siginfo != NULL)) {
359 *child->last_siginfo = *info;
362 spin_unlock_irq(&child->sighand->siglock);
364 read_unlock(&tasklist_lock);
369 #ifdef PTRACE_SINGLESTEP
370 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
372 #define is_singlestep(request) 0
375 #ifdef PTRACE_SINGLEBLOCK
376 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
378 #define is_singleblock(request) 0
382 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
384 #define is_sysemu_singlestep(request) 0
387 static int ptrace_resume(struct task_struct *child, long request, long data)
389 if (!valid_signal(data))
392 if (request == PTRACE_SYSCALL)
393 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
395 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
397 #ifdef TIF_SYSCALL_EMU
398 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
399 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
401 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
404 if (is_singleblock(request)) {
405 if (unlikely(!arch_has_block_step()))
407 user_enable_block_step(child);
408 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
409 if (unlikely(!arch_has_single_step()))
411 user_enable_single_step(child);
414 user_disable_single_step(child);
416 child->exit_code = data;
417 wake_up_process(child);
422 int ptrace_request(struct task_struct *child, long request,
423 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);
446 case PTRACE_GETSIGINFO:
447 ret = ptrace_getsiginfo(child, &siginfo);
449 ret = copy_siginfo_to_user((siginfo_t __user *) data,
453 case PTRACE_SETSIGINFO:
454 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
458 ret = ptrace_setsiginfo(child, &siginfo);
461 case PTRACE_DETACH: /* detach a process that was attached. */
462 ret = ptrace_detach(child, data);
465 #ifdef PTRACE_SINGLESTEP
466 case PTRACE_SINGLESTEP:
468 #ifdef PTRACE_SINGLEBLOCK
469 case PTRACE_SINGLEBLOCK:
473 case PTRACE_SYSEMU_SINGLESTEP:
477 return ptrace_resume(child, request, data);
480 if (child->exit_state) /* already dead */
482 return ptrace_resume(child, request, SIGKILL);
492 * ptrace_traceme -- helper for PTRACE_TRACEME
494 * Performs checks and sets PT_PTRACED.
495 * Should be used by all ptrace implementations for PTRACE_TRACEME.
497 int ptrace_traceme(void)
502 * Are we already being traced?
506 if (!(current->ptrace & PT_PTRACED)) {
508 * See ptrace_attach() comments about the locking here.
511 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
512 task_unlock(current);
515 } while (!write_can_lock(&tasklist_lock));
519 ret = security_ptrace_traceme(current->parent);
522 * Set the ptrace bit in the process ptrace flags.
523 * Then link us on our parent's ptraced list.
526 current->ptrace |= PT_PTRACED;
527 __ptrace_link(current, current->real_parent);
530 write_unlock_irqrestore(&tasklist_lock, flags);
532 task_unlock(current);
537 * ptrace_get_task_struct -- grab a task struct reference for ptrace
538 * @pid: process id to grab a task_struct reference of
540 * This function is a helper for ptrace implementations. It checks
541 * permissions and then grabs a task struct for use of the actual
542 * ptrace implementation.
544 * Returns the task_struct for @pid or an ERR_PTR() on failure.
546 struct task_struct *ptrace_get_task_struct(pid_t pid)
548 struct task_struct *child;
550 read_lock(&tasklist_lock);
551 child = find_task_by_vpid(pid);
553 get_task_struct(child);
555 read_unlock(&tasklist_lock);
557 return ERR_PTR(-ESRCH);
561 #ifndef arch_ptrace_attach
562 #define arch_ptrace_attach(child) do { } while (0)
565 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
567 struct task_struct *child;
571 * This lock_kernel fixes a subtle race with suid exec
574 if (request == PTRACE_TRACEME) {
575 ret = ptrace_traceme();
577 arch_ptrace_attach(current);
581 child = ptrace_get_task_struct(pid);
583 ret = PTR_ERR(child);
587 if (request == PTRACE_ATTACH) {
588 ret = ptrace_attach(child);
590 * Some architectures need to do book-keeping after
594 arch_ptrace_attach(child);
595 goto out_put_task_struct;
598 ret = ptrace_check_attach(child, request == PTRACE_KILL);
600 goto out_put_task_struct;
602 ret = arch_ptrace(child, request, addr, data);
604 goto out_put_task_struct;
607 put_task_struct(child);
613 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
618 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
619 if (copied != sizeof(tmp))
621 return put_user(tmp, (unsigned long __user *)data);
624 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
628 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
629 return (copied == sizeof(data)) ? 0 : -EIO;
632 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
633 #include <linux/compat.h>
635 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
636 compat_ulong_t addr, compat_ulong_t data)
638 compat_ulong_t __user *datap = compat_ptr(data);
644 case PTRACE_PEEKTEXT:
645 case PTRACE_PEEKDATA:
646 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
647 if (ret != sizeof(word))
650 ret = put_user(word, datap);
653 case PTRACE_POKETEXT:
654 case PTRACE_POKEDATA:
655 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
656 ret = (ret != sizeof(data) ? -EIO : 0);
659 case PTRACE_GETEVENTMSG:
660 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
663 case PTRACE_GETSIGINFO:
664 ret = ptrace_getsiginfo(child, &siginfo);
666 ret = copy_siginfo_to_user32(
667 (struct compat_siginfo __user *) datap,
671 case PTRACE_SETSIGINFO:
672 memset(&siginfo, 0, sizeof siginfo);
673 if (copy_siginfo_from_user32(
674 &siginfo, (struct compat_siginfo __user *) datap))
677 ret = ptrace_setsiginfo(child, &siginfo);
681 ret = ptrace_request(child, request, addr, data);
687 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
688 compat_long_t addr, compat_long_t data)
690 struct task_struct *child;
694 * This lock_kernel fixes a subtle race with suid exec
697 if (request == PTRACE_TRACEME) {
698 ret = ptrace_traceme();
702 child = ptrace_get_task_struct(pid);
704 ret = PTR_ERR(child);
708 if (request == PTRACE_ATTACH) {
709 ret = ptrace_attach(child);
711 * Some architectures need to do book-keeping after
715 arch_ptrace_attach(child);
716 goto out_put_task_struct;
719 ret = ptrace_check_attach(child, request == PTRACE_KILL);
721 ret = compat_arch_ptrace(child, request, addr, data);
724 put_task_struct(child);
729 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */