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 /* May we inspect the given task?
119 * This check is used both for attaching with ptrace
120 * and for allowing access to sensitive information in /proc.
122 * ptrace_attach denies several cases that /proc allows
123 * because setting up the necessary parent/child relationship
124 * or halting the specified task is impossible.
129 /* Don't let security modules deny introspection */
132 current_uid_gid(&uid, &gid);
133 if ((uid != task->euid ||
138 gid != task->gid) && !capable(CAP_SYS_PTRACE))
142 dumpable = get_dumpable(task->mm);
143 if (!dumpable && !capable(CAP_SYS_PTRACE))
146 return security_ptrace_may_access(task, mode);
149 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
153 err = __ptrace_may_access(task, mode);
155 return (!err ? true : false);
158 int ptrace_attach(struct task_struct *task)
166 if (same_thread_group(task, current))
173 * We want to hold both the task-lock and the
174 * tasklist_lock for writing at the same time.
175 * But that's against the rules (tasklist_lock
176 * is taken for reading by interrupts on other
177 * cpu's that may have task_lock).
180 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
184 } while (!write_can_lock(&tasklist_lock));
190 /* the same process cannot be attached many times */
191 if (task->ptrace & PT_PTRACED)
193 retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
198 task->ptrace |= PT_PTRACED;
199 if (capable(CAP_SYS_PTRACE))
200 task->ptrace |= PT_PTRACE_CAP;
202 __ptrace_link(task, current);
204 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
206 write_unlock_irqrestore(&tasklist_lock, flags);
212 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
214 child->exit_code = data;
215 /* .. re-parent .. */
216 __ptrace_unlink(child);
217 /* .. and wake it up. */
218 if (child->exit_state != EXIT_ZOMBIE)
219 wake_up_process(child);
222 int ptrace_detach(struct task_struct *child, unsigned int data)
224 if (!valid_signal(data))
227 /* Architecture-specific hardware disable .. */
228 ptrace_disable(child);
229 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
231 write_lock_irq(&tasklist_lock);
232 /* protect against de_thread()->release_task() */
234 __ptrace_detach(child, data);
235 write_unlock_irq(&tasklist_lock);
240 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
246 int this_len, retval;
248 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
249 retval = access_process_vm(tsk, src, buf, this_len, 0);
255 if (copy_to_user(dst, buf, retval))
265 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
271 int this_len, retval;
273 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
274 if (copy_from_user(buf, src, this_len))
276 retval = access_process_vm(tsk, dst, buf, this_len, 1);
290 static int ptrace_setoptions(struct task_struct *child, long data)
292 child->ptrace &= ~PT_TRACE_MASK;
294 if (data & PTRACE_O_TRACESYSGOOD)
295 child->ptrace |= PT_TRACESYSGOOD;
297 if (data & PTRACE_O_TRACEFORK)
298 child->ptrace |= PT_TRACE_FORK;
300 if (data & PTRACE_O_TRACEVFORK)
301 child->ptrace |= PT_TRACE_VFORK;
303 if (data & PTRACE_O_TRACECLONE)
304 child->ptrace |= PT_TRACE_CLONE;
306 if (data & PTRACE_O_TRACEEXEC)
307 child->ptrace |= PT_TRACE_EXEC;
309 if (data & PTRACE_O_TRACEVFORKDONE)
310 child->ptrace |= PT_TRACE_VFORK_DONE;
312 if (data & PTRACE_O_TRACEEXIT)
313 child->ptrace |= PT_TRACE_EXIT;
315 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
318 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
322 read_lock(&tasklist_lock);
323 if (likely(child->sighand != NULL)) {
325 spin_lock_irq(&child->sighand->siglock);
326 if (likely(child->last_siginfo != NULL)) {
327 *info = *child->last_siginfo;
330 spin_unlock_irq(&child->sighand->siglock);
332 read_unlock(&tasklist_lock);
336 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
340 read_lock(&tasklist_lock);
341 if (likely(child->sighand != NULL)) {
343 spin_lock_irq(&child->sighand->siglock);
344 if (likely(child->last_siginfo != NULL)) {
345 *child->last_siginfo = *info;
348 spin_unlock_irq(&child->sighand->siglock);
350 read_unlock(&tasklist_lock);
355 #ifdef PTRACE_SINGLESTEP
356 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
358 #define is_singlestep(request) 0
361 #ifdef PTRACE_SINGLEBLOCK
362 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
364 #define is_singleblock(request) 0
368 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
370 #define is_sysemu_singlestep(request) 0
373 static int ptrace_resume(struct task_struct *child, long request, long data)
375 if (!valid_signal(data))
378 if (request == PTRACE_SYSCALL)
379 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
381 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
383 #ifdef TIF_SYSCALL_EMU
384 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
385 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
387 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
390 if (is_singleblock(request)) {
391 if (unlikely(!arch_has_block_step()))
393 user_enable_block_step(child);
394 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
395 if (unlikely(!arch_has_single_step()))
397 user_enable_single_step(child);
400 user_disable_single_step(child);
402 child->exit_code = data;
403 wake_up_process(child);
408 int ptrace_request(struct task_struct *child, long request,
409 long addr, long data)
415 case PTRACE_PEEKTEXT:
416 case PTRACE_PEEKDATA:
417 return generic_ptrace_peekdata(child, addr, data);
418 case PTRACE_POKETEXT:
419 case PTRACE_POKEDATA:
420 return generic_ptrace_pokedata(child, addr, data);
422 #ifdef PTRACE_OLDSETOPTIONS
423 case PTRACE_OLDSETOPTIONS:
425 case PTRACE_SETOPTIONS:
426 ret = ptrace_setoptions(child, data);
428 case PTRACE_GETEVENTMSG:
429 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
432 case PTRACE_GETSIGINFO:
433 ret = ptrace_getsiginfo(child, &siginfo);
435 ret = copy_siginfo_to_user((siginfo_t __user *) data,
439 case PTRACE_SETSIGINFO:
440 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
444 ret = ptrace_setsiginfo(child, &siginfo);
447 case PTRACE_DETACH: /* detach a process that was attached. */
448 ret = ptrace_detach(child, data);
451 #ifdef PTRACE_SINGLESTEP
452 case PTRACE_SINGLESTEP:
454 #ifdef PTRACE_SINGLEBLOCK
455 case PTRACE_SINGLEBLOCK:
459 case PTRACE_SYSEMU_SINGLESTEP:
463 return ptrace_resume(child, request, data);
466 if (child->exit_state) /* already dead */
468 return ptrace_resume(child, request, SIGKILL);
478 * ptrace_traceme -- helper for PTRACE_TRACEME
480 * Performs checks and sets PT_PTRACED.
481 * Should be used by all ptrace implementations for PTRACE_TRACEME.
483 int ptrace_traceme(void)
488 * Are we already being traced?
492 if (!(current->ptrace & PT_PTRACED)) {
494 * See ptrace_attach() comments about the locking here.
497 if (!write_trylock_irqsave(&tasklist_lock, flags)) {
498 task_unlock(current);
501 } while (!write_can_lock(&tasklist_lock));
505 ret = security_ptrace_traceme(current->parent);
508 * Set the ptrace bit in the process ptrace flags.
509 * Then link us on our parent's ptraced list.
512 current->ptrace |= PT_PTRACED;
513 __ptrace_link(current, current->real_parent);
516 write_unlock_irqrestore(&tasklist_lock, flags);
518 task_unlock(current);
523 * ptrace_get_task_struct -- grab a task struct reference for ptrace
524 * @pid: process id to grab a task_struct reference of
526 * This function is a helper for ptrace implementations. It checks
527 * permissions and then grabs a task struct for use of the actual
528 * ptrace implementation.
530 * Returns the task_struct for @pid or an ERR_PTR() on failure.
532 struct task_struct *ptrace_get_task_struct(pid_t pid)
534 struct task_struct *child;
536 read_lock(&tasklist_lock);
537 child = find_task_by_vpid(pid);
539 get_task_struct(child);
541 read_unlock(&tasklist_lock);
543 return ERR_PTR(-ESRCH);
547 #ifndef arch_ptrace_attach
548 #define arch_ptrace_attach(child) do { } while (0)
551 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
553 struct task_struct *child;
557 * This lock_kernel fixes a subtle race with suid exec
560 if (request == PTRACE_TRACEME) {
561 ret = ptrace_traceme();
563 arch_ptrace_attach(current);
567 child = ptrace_get_task_struct(pid);
569 ret = PTR_ERR(child);
573 if (request == PTRACE_ATTACH) {
574 ret = ptrace_attach(child);
576 * Some architectures need to do book-keeping after
580 arch_ptrace_attach(child);
581 goto out_put_task_struct;
584 ret = ptrace_check_attach(child, request == PTRACE_KILL);
586 goto out_put_task_struct;
588 ret = arch_ptrace(child, request, addr, data);
590 goto out_put_task_struct;
593 put_task_struct(child);
599 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
604 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
605 if (copied != sizeof(tmp))
607 return put_user(tmp, (unsigned long __user *)data);
610 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
614 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
615 return (copied == sizeof(data)) ? 0 : -EIO;
618 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
619 #include <linux/compat.h>
621 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
622 compat_ulong_t addr, compat_ulong_t data)
624 compat_ulong_t __user *datap = compat_ptr(data);
630 case PTRACE_PEEKTEXT:
631 case PTRACE_PEEKDATA:
632 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
633 if (ret != sizeof(word))
636 ret = put_user(word, datap);
639 case PTRACE_POKETEXT:
640 case PTRACE_POKEDATA:
641 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
642 ret = (ret != sizeof(data) ? -EIO : 0);
645 case PTRACE_GETEVENTMSG:
646 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
649 case PTRACE_GETSIGINFO:
650 ret = ptrace_getsiginfo(child, &siginfo);
652 ret = copy_siginfo_to_user32(
653 (struct compat_siginfo __user *) datap,
657 case PTRACE_SETSIGINFO:
658 memset(&siginfo, 0, sizeof siginfo);
659 if (copy_siginfo_from_user32(
660 &siginfo, (struct compat_siginfo __user *) datap))
663 ret = ptrace_setsiginfo(child, &siginfo);
667 ret = ptrace_request(child, request, addr, data);
673 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
674 compat_long_t addr, compat_long_t data)
676 struct task_struct *child;
680 * This lock_kernel fixes a subtle race with suid exec
683 if (request == PTRACE_TRACEME) {
684 ret = ptrace_traceme();
688 child = ptrace_get_task_struct(pid);
690 ret = PTR_ERR(child);
694 if (request == PTRACE_ATTACH) {
695 ret = ptrace_attach(child);
697 * Some architectures need to do book-keeping after
701 arch_ptrace_attach(child);
702 goto out_put_task_struct;
705 ret = ptrace_check_attach(child, request == PTRACE_KILL);
707 ret = compat_arch_ptrace(child, request, addr, data);
710 put_task_struct(child);
715 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */