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 (ptrace_reparented(child)) {
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 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
213 write_unlock_irqrestore(&tasklist_lock, flags);
219 static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
221 child->exit_code = data;
222 /* .. re-parent .. */
223 __ptrace_unlink(child);
224 /* .. and wake it up. */
225 if (child->exit_state != EXIT_ZOMBIE)
226 wake_up_process(child);
229 int ptrace_detach(struct task_struct *child, unsigned int data)
231 if (!valid_signal(data))
234 /* Architecture-specific hardware disable .. */
235 ptrace_disable(child);
236 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
238 write_lock_irq(&tasklist_lock);
239 /* protect against de_thread()->release_task() */
241 __ptrace_detach(child, data);
242 write_unlock_irq(&tasklist_lock);
247 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
253 int this_len, retval;
255 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
256 retval = access_process_vm(tsk, src, buf, this_len, 0);
262 if (copy_to_user(dst, buf, retval))
272 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
278 int this_len, retval;
280 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
281 if (copy_from_user(buf, src, this_len))
283 retval = access_process_vm(tsk, dst, buf, this_len, 1);
297 static int ptrace_setoptions(struct task_struct *child, long data)
299 child->ptrace &= ~PT_TRACE_MASK;
301 if (data & PTRACE_O_TRACESYSGOOD)
302 child->ptrace |= PT_TRACESYSGOOD;
304 if (data & PTRACE_O_TRACEFORK)
305 child->ptrace |= PT_TRACE_FORK;
307 if (data & PTRACE_O_TRACEVFORK)
308 child->ptrace |= PT_TRACE_VFORK;
310 if (data & PTRACE_O_TRACECLONE)
311 child->ptrace |= PT_TRACE_CLONE;
313 if (data & PTRACE_O_TRACEEXEC)
314 child->ptrace |= PT_TRACE_EXEC;
316 if (data & PTRACE_O_TRACEVFORKDONE)
317 child->ptrace |= PT_TRACE_VFORK_DONE;
319 if (data & PTRACE_O_TRACEEXIT)
320 child->ptrace |= PT_TRACE_EXIT;
322 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
325 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
329 read_lock(&tasklist_lock);
330 if (likely(child->sighand != NULL)) {
332 spin_lock_irq(&child->sighand->siglock);
333 if (likely(child->last_siginfo != NULL)) {
334 *info = *child->last_siginfo;
337 spin_unlock_irq(&child->sighand->siglock);
339 read_unlock(&tasklist_lock);
343 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
347 read_lock(&tasklist_lock);
348 if (likely(child->sighand != NULL)) {
350 spin_lock_irq(&child->sighand->siglock);
351 if (likely(child->last_siginfo != NULL)) {
352 *child->last_siginfo = *info;
355 spin_unlock_irq(&child->sighand->siglock);
357 read_unlock(&tasklist_lock);
362 #ifdef PTRACE_SINGLESTEP
363 #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
365 #define is_singlestep(request) 0
368 #ifdef PTRACE_SINGLEBLOCK
369 #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
371 #define is_singleblock(request) 0
375 #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
377 #define is_sysemu_singlestep(request) 0
380 static int ptrace_resume(struct task_struct *child, long request, long data)
382 if (!valid_signal(data))
385 if (request == PTRACE_SYSCALL)
386 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
388 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
390 #ifdef TIF_SYSCALL_EMU
391 if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
392 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
394 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
397 if (is_singleblock(request)) {
398 if (unlikely(!arch_has_block_step()))
400 user_enable_block_step(child);
401 } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
402 if (unlikely(!arch_has_single_step()))
404 user_enable_single_step(child);
407 user_disable_single_step(child);
409 child->exit_code = data;
410 wake_up_process(child);
415 int ptrace_request(struct task_struct *child, long request,
416 long addr, long data)
422 case PTRACE_PEEKTEXT:
423 case PTRACE_PEEKDATA:
424 return generic_ptrace_peekdata(child, addr, data);
425 case PTRACE_POKETEXT:
426 case PTRACE_POKEDATA:
427 return generic_ptrace_pokedata(child, addr, data);
429 #ifdef PTRACE_OLDSETOPTIONS
430 case PTRACE_OLDSETOPTIONS:
432 case PTRACE_SETOPTIONS:
433 ret = ptrace_setoptions(child, data);
435 case PTRACE_GETEVENTMSG:
436 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
439 case PTRACE_GETSIGINFO:
440 ret = ptrace_getsiginfo(child, &siginfo);
442 ret = copy_siginfo_to_user((siginfo_t __user *) data,
446 case PTRACE_SETSIGINFO:
447 if (copy_from_user(&siginfo, (siginfo_t __user *) data,
451 ret = ptrace_setsiginfo(child, &siginfo);
454 case PTRACE_DETACH: /* detach a process that was attached. */
455 ret = ptrace_detach(child, data);
458 #ifdef PTRACE_SINGLESTEP
459 case PTRACE_SINGLESTEP:
461 #ifdef PTRACE_SINGLEBLOCK
462 case PTRACE_SINGLEBLOCK:
466 case PTRACE_SYSEMU_SINGLESTEP:
470 return ptrace_resume(child, request, data);
473 if (child->exit_state) /* already dead */
475 return ptrace_resume(child, request, SIGKILL);
485 * ptrace_traceme -- helper for PTRACE_TRACEME
487 * Performs checks and sets PT_PTRACED.
488 * Should be used by all ptrace implementations for PTRACE_TRACEME.
490 int ptrace_traceme(void)
495 * Are we already being traced?
498 if (!(current->ptrace & PT_PTRACED)) {
499 ret = security_ptrace(current->parent, current);
501 * Set the ptrace bit in the process ptrace flags.
504 current->ptrace |= PT_PTRACED;
506 task_unlock(current);
511 * ptrace_get_task_struct -- grab a task struct reference for ptrace
512 * @pid: process id to grab a task_struct reference of
514 * This function is a helper for ptrace implementations. It checks
515 * permissions and then grabs a task struct for use of the actual
516 * ptrace implementation.
518 * Returns the task_struct for @pid or an ERR_PTR() on failure.
520 struct task_struct *ptrace_get_task_struct(pid_t pid)
522 struct task_struct *child;
525 * Tracing init is not allowed.
528 return ERR_PTR(-EPERM);
530 read_lock(&tasklist_lock);
531 child = find_task_by_vpid(pid);
533 get_task_struct(child);
535 read_unlock(&tasklist_lock);
537 return ERR_PTR(-ESRCH);
541 #ifndef arch_ptrace_attach
542 #define arch_ptrace_attach(child) do { } while (0)
545 #ifndef __ARCH_SYS_PTRACE
546 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
548 struct task_struct *child;
552 * This lock_kernel fixes a subtle race with suid exec
555 if (request == PTRACE_TRACEME) {
556 ret = ptrace_traceme();
558 arch_ptrace_attach(current);
562 child = ptrace_get_task_struct(pid);
564 ret = PTR_ERR(child);
568 if (request == PTRACE_ATTACH) {
569 ret = ptrace_attach(child);
571 * Some architectures need to do book-keeping after
575 arch_ptrace_attach(child);
576 goto out_put_task_struct;
579 ret = ptrace_check_attach(child, request == PTRACE_KILL);
581 goto out_put_task_struct;
583 ret = arch_ptrace(child, request, addr, data);
585 goto out_put_task_struct;
588 put_task_struct(child);
593 #endif /* __ARCH_SYS_PTRACE */
595 int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
600 copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
601 if (copied != sizeof(tmp))
603 return put_user(tmp, (unsigned long __user *)data);
606 int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
610 copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
611 return (copied == sizeof(data)) ? 0 : -EIO;
614 #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
615 #include <linux/compat.h>
617 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
618 compat_ulong_t addr, compat_ulong_t data)
620 compat_ulong_t __user *datap = compat_ptr(data);
626 case PTRACE_PEEKTEXT:
627 case PTRACE_PEEKDATA:
628 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
629 if (ret != sizeof(word))
632 ret = put_user(word, datap);
635 case PTRACE_POKETEXT:
636 case PTRACE_POKEDATA:
637 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
638 ret = (ret != sizeof(data) ? -EIO : 0);
641 case PTRACE_GETEVENTMSG:
642 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
645 case PTRACE_GETSIGINFO:
646 ret = ptrace_getsiginfo(child, &siginfo);
648 ret = copy_siginfo_to_user32(
649 (struct compat_siginfo __user *) datap,
653 case PTRACE_SETSIGINFO:
654 memset(&siginfo, 0, sizeof siginfo);
655 if (copy_siginfo_from_user32(
656 &siginfo, (struct compat_siginfo __user *) datap))
659 ret = ptrace_setsiginfo(child, &siginfo);
663 ret = ptrace_request(child, request, addr, data);
669 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
670 compat_long_t addr, compat_long_t data)
672 struct task_struct *child;
676 * This lock_kernel fixes a subtle race with suid exec
679 if (request == PTRACE_TRACEME) {
680 ret = ptrace_traceme();
684 child = ptrace_get_task_struct(pid);
686 ret = PTR_ERR(child);
690 if (request == PTRACE_ATTACH) {
691 ret = ptrace_attach(child);
693 * Some architectures need to do book-keeping after
697 arch_ptrace_attach(child);
698 goto out_put_task_struct;
701 ret = ptrace_check_attach(child, request == PTRACE_KILL);
703 ret = compat_arch_ptrace(child, request, addr, data);
706 put_task_struct(child);
711 #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */