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 &&
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)
110 spin_unlock_irq(&child->sighand->siglock);
112 read_unlock(&tasklist_lock);
115 wait_task_inactive(child);
117 /* All systems go.. */
121 int __ptrace_may_attach(struct task_struct *task)
123 /* May we inspect the given task?
124 * This check is used both for attaching with ptrace
125 * and for allowing access to sensitive information in /proc.
127 * ptrace_attach denies several cases that /proc allows
128 * because setting up the necessary parent/child relationship
129 * or halting the specified task is impossible.
132 /* Don't let security modules deny introspection */
135 if (((current->uid != task->euid) ||
136 (current->uid != task->suid) ||
137 (current->uid != task->uid) ||
138 (current->gid != task->egid) ||
139 (current->gid != task->sgid) ||
140 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
144 dumpable = get_dumpable(task->mm);
145 if (!dumpable && !capable(CAP_SYS_PTRACE))
148 return security_ptrace(current, task);
151 int ptrace_may_attach(struct task_struct *task)
155 err = __ptrace_may_attach(task);
160 int ptrace_attach(struct task_struct *task)
170 if (same_thread_group(task, current))
177 * We want to hold both the task-lock and the
178 * tasklist_lock for writing at the same time.
179 * But that's against the rules (tasklist_lock
180 * is taken for reading by interrupts on other
181 * cpu's that may have task_lock).
184 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
188 } while (!write_can_lock(&tasklist_lock));
194 /* the same process cannot be attached many times */
195 if (task->ptrace & PT_PTRACED)
197 retval = __ptrace_may_attach(task);
202 task->ptrace |= PT_PTRACED;
203 if (capable(CAP_SYS_PTRACE))
204 task->ptrace |= PT_PTRACE_CAP;
206 __ptrace_link(task, current);
208 force_sig_specific(SIGSTOP, task);
211 write_unlock_irqrestore(&tasklist_lock, flags);
217 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
219 child->exit_code = data;
220 /* .. re-parent .. */
221 __ptrace_unlink(child);
222 /* .. and wake it up. */
223 if (child->exit_state != EXIT_ZOMBIE)
224 wake_up_process(child);
227 int ptrace_detach(struct task_struct *child, unsigned int data)
229 if (!valid_signal(data))
232 /* Architecture-specific hardware disable .. */
233 ptrace_disable(child);
234 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
236 write_lock_irq(&tasklist_lock);
237 /* protect against de_thread()->release_task() */
239 __ptrace_detach(child, data);
240 write_unlock_irq(&tasklist_lock);
245 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
251 int this_len, retval;
253 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
254 retval = access_process_vm(tsk, src, buf, this_len, 0);
260 if (copy_to_user(dst, buf, retval))
270 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
276 int this_len, retval;
278 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
279 if (copy_from_user(buf, src, this_len))
281 retval = access_process_vm(tsk, dst, buf, this_len, 1);
295 static int ptrace_setoptions(struct task_struct *child, long data)
297 child->ptrace &= ~PT_TRACE_MASK;
299 if (data & PTRACE_O_TRACESYSGOOD)
300 child->ptrace |= PT_TRACESYSGOOD;
302 if (data & PTRACE_O_TRACEFORK)
303 child->ptrace |= PT_TRACE_FORK;
305 if (data & PTRACE_O_TRACEVFORK)
306 child->ptrace |= PT_TRACE_VFORK;
308 if (data & PTRACE_O_TRACECLONE)
309 child->ptrace |= PT_TRACE_CLONE;
311 if (data & PTRACE_O_TRACEEXEC)
312 child->ptrace |= PT_TRACE_EXEC;
314 if (data & PTRACE_O_TRACEVFORKDONE)
315 child->ptrace |= PT_TRACE_VFORK_DONE;
317 if (data & PTRACE_O_TRACEEXIT)
318 child->ptrace |= PT_TRACE_EXIT;
320 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
323 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
328 read_lock(&tasklist_lock);
329 if (likely(child->sighand != NULL)) {
331 spin_lock_irq(&child->sighand->siglock);
332 if (likely(child->last_siginfo != NULL)) {
333 lastinfo = *child->last_siginfo;
336 spin_unlock_irq(&child->sighand->siglock);
338 read_unlock(&tasklist_lock);
340 return copy_siginfo_to_user(data, &lastinfo);
344 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
349 if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
352 read_lock(&tasklist_lock);
353 if (likely(child->sighand != NULL)) {
355 spin_lock_irq(&child->sighand->siglock);
356 if (likely(child->last_siginfo != NULL)) {
357 *child->last_siginfo = newinfo;
360 spin_unlock_irq(&child->sighand->siglock);
362 read_unlock(&tasklist_lock);
367 #ifdef PTRACE_SINGLESTEP
368 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
370 #define is_singlestep(request) 0
373 #ifdef PTRACE_SINGLEBLOCK
374 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
376 #define is_singleblock(request) 0
380 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
382 #define is_sysemu_singlestep(request) 0
385 static int ptrace_resume(struct task_struct *child, long request, long data)
387 if (!valid_signal(data))
390 if (request == PTRACE_SYSCALL)
391 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
393 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
395 #ifdef TIF_SYSCALL_EMU
396 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
397 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
399 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
402 if (is_singleblock(request)) {
403 if (unlikely(!arch_has_block_step()))
405 user_enable_block_step(child);
406 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
407 if (unlikely(!arch_has_single_step()))
409 user_enable_single_step(child);
412 user_disable_single_step(child);
414 child->exit_code = data;
415 wake_up_process(child);
420 int ptrace_request(struct task_struct *child, long request,
421 long addr, long data)
426 case PTRACE_PEEKTEXT:
427 case PTRACE_PEEKDATA:
428 return generic_ptrace_peekdata(child, addr, data);
429 case PTRACE_POKETEXT:
430 case PTRACE_POKEDATA:
431 return generic_ptrace_pokedata(child, addr, data);
433 #ifdef PTRACE_OLDSETOPTIONS
434 case PTRACE_OLDSETOPTIONS:
436 case PTRACE_SETOPTIONS:
437 ret = ptrace_setoptions(child, data);
439 case PTRACE_GETEVENTMSG:
440 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
442 case PTRACE_GETSIGINFO:
443 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
445 case PTRACE_SETSIGINFO:
446 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
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?
492 if (!(current->ptrace & PT_PTRACED)) {
493 ret = security_ptrace(current->parent, current);
495 * Set the ptrace bit in the process ptrace flags.
498 current->ptrace |= PT_PTRACED;
500 task_unlock(current);
505 * ptrace_get_task_struct -- grab a task struct reference for ptrace
506 * @pid: process id to grab a task_struct reference of
508 * This function is a helper for ptrace implementations. It checks
509 * permissions and then grabs a task struct for use of the actual
510 * ptrace implementation.
512 * Returns the task_struct for @pid or an ERR_PTR() on failure.
514 struct task_struct *ptrace_get_task_struct(pid_t pid)
516 struct task_struct *child;
519 * Tracing init is not allowed.
522 return ERR_PTR(-EPERM);
524 read_lock(&tasklist_lock);
525 child = find_task_by_vpid(pid);
527 get_task_struct(child);
529 read_unlock(&tasklist_lock);
531 return ERR_PTR(-ESRCH);
535 #ifndef arch_ptrace_attach
536 #define arch_ptrace_attach(child) do { } while (0)
539 #ifndef __ARCH_SYS_PTRACE
540 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
542 struct task_struct *child;
546 * This lock_kernel fixes a subtle race with suid exec
549 if (request == PTRACE_TRACEME) {
550 ret = ptrace_traceme();
552 arch_ptrace_attach(current);
556 child = ptrace_get_task_struct(pid);
558 ret = PTR_ERR(child);
562 if (request == PTRACE_ATTACH) {
563 ret = ptrace_attach(child);
565 * Some architectures need to do book-keeping after
569 arch_ptrace_attach(child);
570 goto out_put_task_struct;
573 ret = ptrace_check_attach(child, request == PTRACE_KILL);
575 goto out_put_task_struct;
577 ret = arch_ptrace(child, request, addr, data);
579 goto out_put_task_struct;
582 put_task_struct(child);
587 #endif /* __ARCH_SYS_PTRACE */
589 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
594 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
595 if (copied != sizeof(tmp))
597 return put_user(tmp, (unsigned long __user *)data);
600 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
604 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
605 return (copied == sizeof(data)) ? 0 : -EIO;
609 #include <linux/compat.h>
611 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
612 compat_ulong_t addr, compat_ulong_t data)
614 compat_ulong_t __user *datap = compat_ptr(data);
619 case PTRACE_PEEKTEXT:
620 case PTRACE_PEEKDATA:
621 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
622 if (ret != sizeof(word))
625 ret = put_user(word, datap);
628 case PTRACE_POKETEXT:
629 case PTRACE_POKEDATA:
630 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
631 ret = (ret != sizeof(data) ? -EIO : 0);
634 case PTRACE_GETEVENTMSG:
635 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
639 ret = ptrace_request(child, request, addr, data);
645 #ifdef __ARCH_WANT_COMPAT_SYS_PTRACE
646 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
647 compat_long_t addr, compat_long_t data)
649 struct task_struct *child;
653 * This lock_kernel fixes a subtle race with suid exec
656 if (request == PTRACE_TRACEME) {
657 ret = ptrace_traceme();
661 child = ptrace_get_task_struct(pid);
663 ret = PTR_ERR(child);
667 if (request == PTRACE_ATTACH) {
668 ret = ptrace_attach(child);
670 * Some architectures need to do book-keeping after
674 arch_ptrace_attach(child);
675 goto out_put_task_struct;
678 ret = ptrace_check_attach(child, request == PTRACE_KILL);
680 ret = compat_arch_ptrace(child, request, addr, data);
683 put_task_struct(child);
688 #endif /* __ARCH_WANT_COMPAT_SYS_PTRACE */
690 #endif /* CONFIG_COMPAT */