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 struct cred *cred = current->cred, *tcred = task->cred;
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.
128 uid_t uid = cred->uid;
129 gid_t gid = cred->gid;
131 /* Don't let security modules deny introspection */
134 if ((uid != tcred->euid ||
135 uid != tcred->suid ||
137 gid != tcred->egid ||
138 gid != tcred->sgid ||
139 gid != tcred->gid) && !capable(CAP_SYS_PTRACE))
143 dumpable = get_dumpable(task->mm);
144 if (!dumpable && !capable(CAP_SYS_PTRACE))
147 return security_ptrace_may_access(task, mode);
150 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
154 err = __ptrace_may_access(task, mode);
156 return (!err ? true : false);
159 int ptrace_attach(struct task_struct *task)
167 if (same_thread_group(task, current))
174 * We want to hold both the task-lock and the
175 * tasklist_lock for writing at the same time.
176 * But that's against the rules (tasklist_lock
177 * is taken for reading by interrupts on other
178 * cpu's that may have task_lock).
181 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
185 } while (!write_can_lock(&tasklist_lock));
191 /* the same process cannot be attached many times */
192 if (task->ptrace & PT_PTRACED)
194 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
199 task->ptrace |= PT_PTRACED;
200 if (capable(CAP_SYS_PTRACE))
201 task->ptrace |= PT_PTRACE_CAP;
203 __ptrace_link(task, current);
205 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
207 write_unlock_irqrestore(&tasklist_lock, flags);
213 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
215 child->exit_code = data;
216 /* .. re-parent .. */
217 __ptrace_unlink(child);
218 /* .. and wake it up. */
219 if (child->exit_state != EXIT_ZOMBIE)
220 wake_up_process(child);
223 int ptrace_detach(struct task_struct *child, unsigned int data)
225 if (!valid_signal(data))
228 /* Architecture-specific hardware disable .. */
229 ptrace_disable(child);
230 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
232 write_lock_irq(&tasklist_lock);
233 /* protect against de_thread()->release_task() */
235 __ptrace_detach(child, data);
236 write_unlock_irq(&tasklist_lock);
241 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
247 int this_len, retval;
249 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
250 retval = access_process_vm(tsk, src, buf, this_len, 0);
256 if (copy_to_user(dst, buf, retval))
266 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
272 int this_len, retval;
274 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
275 if (copy_from_user(buf, src, this_len))
277 retval = access_process_vm(tsk, dst, buf, this_len, 1);
291 static int ptrace_setoptions(struct task_struct *child, long data)
293 child->ptrace &= ~PT_TRACE_MASK;
295 if (data & PTRACE_O_TRACESYSGOOD)
296 child->ptrace |= PT_TRACESYSGOOD;
298 if (data & PTRACE_O_TRACEFORK)
299 child->ptrace |= PT_TRACE_FORK;
301 if (data & PTRACE_O_TRACEVFORK)
302 child->ptrace |= PT_TRACE_VFORK;
304 if (data & PTRACE_O_TRACECLONE)
305 child->ptrace |= PT_TRACE_CLONE;
307 if (data & PTRACE_O_TRACEEXEC)
308 child->ptrace |= PT_TRACE_EXEC;
310 if (data & PTRACE_O_TRACEVFORKDONE)
311 child->ptrace |= PT_TRACE_VFORK_DONE;
313 if (data & PTRACE_O_TRACEEXIT)
314 child->ptrace |= PT_TRACE_EXIT;
316 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
319 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
323 read_lock(&tasklist_lock);
324 if (likely(child->sighand != NULL)) {
326 spin_lock_irq(&child->sighand->siglock);
327 if (likely(child->last_siginfo != NULL)) {
328 *info = *child->last_siginfo;
331 spin_unlock_irq(&child->sighand->siglock);
333 read_unlock(&tasklist_lock);
337 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
341 read_lock(&tasklist_lock);
342 if (likely(child->sighand != NULL)) {
344 spin_lock_irq(&child->sighand->siglock);
345 if (likely(child->last_siginfo != NULL)) {
346 *child->last_siginfo = *info;
349 spin_unlock_irq(&child->sighand->siglock);
351 read_unlock(&tasklist_lock);
356 #ifdef PTRACE_SINGLESTEP
357 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
359 #define is_singlestep(request) 0
362 #ifdef PTRACE_SINGLEBLOCK
363 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
365 #define is_singleblock(request) 0
369 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
371 #define is_sysemu_singlestep(request) 0
374 static int ptrace_resume(struct task_struct *child, long request, long data)
376 if (!valid_signal(data))
379 if (request == PTRACE_SYSCALL)
380 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
382 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
384 #ifdef TIF_SYSCALL_EMU
385 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
386 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
388 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
391 if (is_singleblock(request)) {
392 if (unlikely(!arch_has_block_step()))
394 user_enable_block_step(child);
395 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
396 if (unlikely(!arch_has_single_step()))
398 user_enable_single_step(child);
401 user_disable_single_step(child);
403 child->exit_code = data;
404 wake_up_process(child);
409 int ptrace_request(struct task_struct *child, long request,
410 long addr, long data)
416 case PTRACE_PEEKTEXT:
417 case PTRACE_PEEKDATA:
418 return generic_ptrace_peekdata(child, addr, data);
419 case PTRACE_POKETEXT:
420 case PTRACE_POKEDATA:
421 return generic_ptrace_pokedata(child, addr, data);
423 #ifdef PTRACE_OLDSETOPTIONS
424 case PTRACE_OLDSETOPTIONS:
426 case PTRACE_SETOPTIONS:
427 ret = ptrace_setoptions(child, data);
429 case PTRACE_GETEVENTMSG:
430 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
433 case PTRACE_GETSIGINFO:
434 ret = ptrace_getsiginfo(child, &siginfo);
436 ret = copy_siginfo_to_user((siginfo_t __user *) data,
440 case PTRACE_SETSIGINFO:
441 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
445 ret = ptrace_setsiginfo(child, &siginfo);
448 case PTRACE_DETACH: /* detach a process that was attached. */
449 ret = ptrace_detach(child, data);
452 #ifdef PTRACE_SINGLESTEP
453 case PTRACE_SINGLESTEP:
455 #ifdef PTRACE_SINGLEBLOCK
456 case PTRACE_SINGLEBLOCK:
460 case PTRACE_SYSEMU_SINGLESTEP:
464 return ptrace_resume(child, request, data);
467 if (child->exit_state) /* already dead */
469 return ptrace_resume(child, request, SIGKILL);
479 * ptrace_traceme -- helper for PTRACE_TRACEME
481 * Performs checks and sets PT_PTRACED.
482 * Should be used by all ptrace implementations for PTRACE_TRACEME.
484 int ptrace_traceme(void)
489 * Are we already being traced?
493 if (!(current->ptrace & PT_PTRACED)) {
495 * See ptrace_attach() comments about the locking here.
498 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
499 task_unlock(current);
502 } while (!write_can_lock(&tasklist_lock));
506 ret = security_ptrace_traceme(current->parent);
509 * Set the ptrace bit in the process ptrace flags.
510 * Then link us on our parent's ptraced list.
513 current->ptrace |= PT_PTRACED;
514 __ptrace_link(current, current->real_parent);
517 write_unlock_irqrestore(&tasklist_lock, flags);
519 task_unlock(current);
524 * ptrace_get_task_struct -- grab a task struct reference for ptrace
525 * @pid: process id to grab a task_struct reference of
527 * This function is a helper for ptrace implementations. It checks
528 * permissions and then grabs a task struct for use of the actual
529 * ptrace implementation.
531 * Returns the task_struct for @pid or an ERR_PTR() on failure.
533 struct task_struct *ptrace_get_task_struct(pid_t pid)
535 struct task_struct *child;
537 read_lock(&tasklist_lock);
538 child = find_task_by_vpid(pid);
540 get_task_struct(child);
542 read_unlock(&tasklist_lock);
544 return ERR_PTR(-ESRCH);
548 #ifndef arch_ptrace_attach
549 #define arch_ptrace_attach(child) do { } while (0)
552 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
554 struct task_struct *child;
558 * This lock_kernel fixes a subtle race with suid exec
561 if (request == PTRACE_TRACEME) {
562 ret = ptrace_traceme();
564 arch_ptrace_attach(current);
568 child = ptrace_get_task_struct(pid);
570 ret = PTR_ERR(child);
574 if (request == PTRACE_ATTACH) {
575 ret = ptrace_attach(child);
577 * Some architectures need to do book-keeping after
581 arch_ptrace_attach(child);
582 goto out_put_task_struct;
585 ret = ptrace_check_attach(child, request == PTRACE_KILL);
587 goto out_put_task_struct;
589 ret = arch_ptrace(child, request, addr, data);
591 goto out_put_task_struct;
594 put_task_struct(child);
600 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
605 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
606 if (copied != sizeof(tmp))
608 return put_user(tmp, (unsigned long __user *)data);
611 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
615 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
616 return (copied == sizeof(data)) ? 0 : -EIO;
619 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
620 #include <linux/compat.h>
622 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
623 compat_ulong_t addr, compat_ulong_t data)
625 compat_ulong_t __user *datap = compat_ptr(data);
631 case PTRACE_PEEKTEXT:
632 case PTRACE_PEEKDATA:
633 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
634 if (ret != sizeof(word))
637 ret = put_user(word, datap);
640 case PTRACE_POKETEXT:
641 case PTRACE_POKEDATA:
642 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
643 ret = (ret != sizeof(data) ? -EIO : 0);
646 case PTRACE_GETEVENTMSG:
647 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
650 case PTRACE_GETSIGINFO:
651 ret = ptrace_getsiginfo(child, &siginfo);
653 ret = copy_siginfo_to_user32(
654 (struct compat_siginfo __user *) datap,
658 case PTRACE_SETSIGINFO:
659 memset(&siginfo, 0, sizeof siginfo);
660 if (copy_siginfo_from_user32(
661 &siginfo, (struct compat_siginfo __user *) datap))
664 ret = ptrace_setsiginfo(child, &siginfo);
668 ret = ptrace_request(child, request, addr, data);
674 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
675 compat_long_t addr, compat_long_t data)
677 struct task_struct *child;
681 * This lock_kernel fixes a subtle race with suid exec
684 if (request == PTRACE_TRACEME) {
685 ret = ptrace_traceme();
689 child = ptrace_get_task_struct(pid);
691 ret = PTR_ERR(child);
695 if (request == PTRACE_ATTACH) {
696 ret = ptrace_attach(child);
698 * Some architectures need to do book-keeping after
702 arch_ptrace_attach(child);
703 goto out_put_task_struct;
706 ret = ptrace_check_attach(child, request == PTRACE_KILL);
708 ret = compat_arch_ptrace(child, request, addr, data);
711 put_task_struct(child);
716 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */