/*
   * linux/kernel/ptrace.c
   *
   * (C) Copyright 1999 Linus Torvalds
   *
   * Common interfaces for "ptrace()" which we do not want
   * to continually duplicate across every architecture.
   */

  #include <linux/capability.h>

  #include <linux/export.h>

  #include <linux/sched.h>
  #include <linux/errno.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>

  #include <linux/ptrace.h>
  #include <linux/security.h>

  #include <linux/signal.h>

  #include <linux/audit.h>

  #include <linux/pid_namespace.h>

  #include <linux/syscalls.h>

  #include <linux/uaccess.h>

  #include <linux/regset.h>

  #include <linux/hw_breakpoint.h>

  #include <linux/cn_proc.h>

  static int ptrace_trapping_sleep_fn(void *flags)
  {
  	schedule();
  	return 0;
  }

  /*

   * ptrace a task: make the debugger its new parent and
   * move it to the ptrace list.
   *
   * Must be called with the tasklist lock write-held.
   */

  void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)

  {

  	BUG_ON(!list_empty(&child->ptrace_entry));
  	list_add(&child->ptrace_entry, &new_parent->ptraced);

  	child->parent = new_parent;

  }

  /**
   * __ptrace_unlink - unlink ptracee and restore its execution state
   * @child: ptracee to be unlinked

   *

   * Remove @child from the ptrace list, move it back to the original parent,
   * and restore the execution state so that it conforms to the group stop
   * state.
   *
   * Unlinking can happen via two paths - explicit PTRACE_DETACH or ptracer
   * exiting.  For PTRACE_DETACH, unless the ptracee has been killed between
   * ptrace_check_attach() and here, it's guaranteed to be in TASK_TRACED.
   * If the ptracer is exiting, the ptracee can be in any state.
   *
   * After detach, the ptracee should be in a state which conforms to the
   * group stop.  If the group is stopped or in the process of stopping, the
   * ptracee should be put into TASK_STOPPED; otherwise, it should be woken
   * up from TASK_TRACED.
   *
   * If the ptracee is in TASK_TRACED and needs to be moved to TASK_STOPPED,
   * it goes through TRACED -> RUNNING -> STOPPED transition which is similar
   * to but in the opposite direction of what happens while attaching to a
   * stopped task.  However, in this direction, the intermediate RUNNING
   * state is not hidden even from the current ptracer and if it immediately
   * re-attaches and performs a WNOHANG wait(2), it may fail.

   *
   * CONTEXT:
   * write_lock_irq(tasklist_lock)

   */

  void __ptrace_unlink(struct task_struct *child)

  {

  	BUG_ON(!child->ptrace);

  	child->ptrace = 0;

  	child->parent = child->real_parent;
  	list_del_init(&child->ptrace_entry);

  	spin_lock(&child->sighand->siglock);

  
  	/*

  	 * Clear all pending traps and TRAPPING.  TRAPPING should be
  	 * cleared regardless of JOBCTL_STOP_PENDING.  Do it explicitly.
  	 */
  	task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK);
  	task_clear_jobctl_trapping(child);
  
  	/*

  	 * Reinstate JOBCTL_STOP_PENDING if group stop is in effect and

  	 * @child isn't dead.
  	 */
  	if (!(child->flags & PF_EXITING) &&
  	    (child->signal->flags & SIGNAL_STOP_STOPPED ||

  	     child->signal->group_stop_count)) {

  		child->jobctl |= JOBCTL_STOP_PENDING;

  		/*
  		 * This is only possible if this thread was cloned by the
  		 * traced task running in the stopped group, set the signal
  		 * for the future reports.
  		 * FIXME: we should change ptrace_init_task() to handle this
  		 * case.
  		 */
  		if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
  			child->jobctl |= SIGSTOP;
  	}

  	/*
  	 * If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
  	 * @child in the butt.  Note that @resume should be used iff @child
  	 * is in TASK_TRACED; otherwise, we might unduly disrupt
  	 * TASK_KILLABLE sleeps.
  	 */

  	if (child->jobctl & JOBCTL_STOP_PENDING || task_is_traced(child))

  		signal_wake_up(child, task_is_traced(child));

  	spin_unlock(&child->sighand->siglock);

  }

  /**
   * ptrace_check_attach - check whether ptracee is ready for ptrace operation
   * @child: ptracee to check for
   * @ignore_state: don't check whether @child is currently %TASK_TRACED
   *
   * Check whether @child is being ptraced by %current and ready for further
   * ptrace operations.  If @ignore_state is %false, @child also should be in
   * %TASK_TRACED state and on return the child is guaranteed to be traced
   * and not executing.  If @ignore_state is %true, @child can be in any
   * state.
   *
   * CONTEXT:
   * Grabs and releases tasklist_lock and @child->sighand->siglock.
   *
   * RETURNS:
   * 0 on success, -ESRCH if %child is not ready.

   */

  int ptrace_check_attach(struct task_struct *child, bool ignore_state)

  {
  	int ret = -ESRCH;
  
  	/*
  	 * We take the read lock around doing both checks to close a
  	 * possible race where someone else was tracing our child and
  	 * detached between these two checks.  After this locked check,
  	 * we are sure that this is our traced child and that can only
  	 * be changed by us so it's not changing right after this.
  	 */
  	read_lock(&tasklist_lock);

  	if ((child->ptrace & PT_PTRACED) && child->parent == current) {

  		/*
  		 * child->sighand can't be NULL, release_task()
  		 * does ptrace_unlink() before __exit_signal().
  		 */

  		spin_lock_irq(&child->sighand->siglock);

  		WARN_ON_ONCE(task_is_stopped(child));

  		if (ignore_state || (task_is_traced(child) &&
  				     !(child->jobctl & JOBCTL_LISTENING)))

  			ret = 0;

  		spin_unlock_irq(&child->sighand->siglock);
  	}
  	read_unlock(&tasklist_lock);

  	if (!ret && !ignore_state)

  		ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;

  
  	/* All systems go.. */
  	return ret;
  }

  static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
  {
  	if (mode & PTRACE_MODE_NOAUDIT)
  		return has_ns_capability_noaudit(current, ns, CAP_SYS_PTRACE);
  	else
  		return has_ns_capability(current, ns, CAP_SYS_PTRACE);
  }

  int __ptrace_may_access(struct task_struct *task, unsigned int mode)

  {

  	const struct cred *cred = current_cred(), *tcred;

  	/* May we inspect the given task?
  	 * This check is used both for attaching with ptrace
  	 * and for allowing access to sensitive information in /proc.
  	 *
  	 * ptrace_attach denies several cases that /proc allows
  	 * because setting up the necessary parent/child relationship
  	 * or halting the specified task is impossible.
  	 */
  	int dumpable = 0;
  	/* Don't let security modules deny introspection */
  	if (task == current)
  		return 0;

  	rcu_read_lock();
  	tcred = __task_cred(task);

  	if (cred->user->user_ns == tcred->user->user_ns &&
  	    (cred->uid == tcred->euid &&
  	     cred->uid == tcred->suid &&
  	     cred->uid == tcred->uid  &&
  	     cred->gid == tcred->egid &&
  	     cred->gid == tcred->sgid &&
  	     cred->gid == tcred->gid))
  		goto ok;

  	if (ptrace_has_cap(tcred->user->user_ns, mode))

  		goto ok;
  	rcu_read_unlock();
  	return -EPERM;
  ok:

  	rcu_read_unlock();

  	smp_rmb();

  	if (task->mm)

  		dumpable = get_dumpable(task->mm);

  	if (!dumpable  && !ptrace_has_cap(task_user_ns(task), mode))

  		return -EPERM;

  	return security_ptrace_access_check(task, mode);

  }

  bool ptrace_may_access(struct task_struct *task, unsigned int mode)

  {
  	int err;
  	task_lock(task);

  	err = __ptrace_may_access(task, mode);

  	task_unlock(task);

  	return !err;

  }

  static int ptrace_attach(struct task_struct *task, long request,
  			 unsigned long flags)

  {

  	bool seize = (request == PTRACE_SEIZE);

  	int retval;

  	/*
  	 * SEIZE will enable new ptrace behaviors which will be implemented
  	 * gradually.  SEIZE_DEVEL is used to prevent applications
  	 * expecting full SEIZE behaviors trapping on kernel commits which
  	 * are still in the process of implementing them.
  	 *
  	 * Only test programs for new ptrace behaviors being implemented
  	 * should set SEIZE_DEVEL.  If unset, SEIZE will fail with -EIO.
  	 *
  	 * Once SEIZE behaviors are completely implemented, this flag and
  	 * the following test will be removed.
  	 */
  	retval = -EIO;
  	if (seize && !(flags & PTRACE_SEIZE_DEVEL))
  		goto out;

  	audit_ptrace(task);

  	retval = -EPERM;

  	if (unlikely(task->flags & PF_KTHREAD))
  		goto out;

  	if (same_thread_group(task, current))

  		goto out;

  	/*
  	 * Protect exec's credential calculations against our interference;

  	 * interference; SUID, SGID and LSM creds get determined differently
  	 * under ptrace.

  	 */

  	retval = -ERESTARTNOINTR;

  	if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))

  		goto out;

  	task_lock(task);

  	retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);

  	task_unlock(task);

  	if (retval)

  		goto unlock_creds;

  	write_lock_irq(&tasklist_lock);

  	retval = -EPERM;
  	if (unlikely(task->exit_state))

  		goto unlock_tasklist;

  	if (task->ptrace)

  		goto unlock_tasklist;

  	task->ptrace = PT_PTRACED;

  	if (seize)
  		task->ptrace |= PT_SEIZED;

  	if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))

  		task->ptrace |= PT_PTRACE_CAP;

  	__ptrace_link(task, current);

  
  	/* SEIZE doesn't trap tracee on attach */
  	if (!seize)
  		send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);

  	spin_lock(&task->sighand->siglock);
  
  	/*

  	 * If the task is already STOPPED, set JOBCTL_TRAP_STOP and

  	 * TRAPPING, and kick it so that it transits to TRACED.  TRAPPING
  	 * will be cleared if the child completes the transition or any
  	 * event which clears the group stop states happens.  We'll wait
  	 * for the transition to complete before returning from this
  	 * function.
  	 *
  	 * This hides STOPPED -> RUNNING -> TRACED transition from the
  	 * attaching thread but a different thread in the same group can
  	 * still observe the transient RUNNING state.  IOW, if another
  	 * thread's WNOHANG wait(2) on the stopped tracee races against
  	 * ATTACH, the wait(2) may fail due to the transient RUNNING.
  	 *
  	 * The following task_is_stopped() test is safe as both transitions
  	 * in and out of STOPPED are protected by siglock.
  	 */

  	if (task_is_stopped(task) &&

  	    task_set_jobctl_pending(task, JOBCTL_TRAP_STOP | JOBCTL_TRAPPING))

  		signal_wake_up(task, 1);

  
  	spin_unlock(&task->sighand->siglock);

  	retval = 0;

  unlock_tasklist:
  	write_unlock_irq(&tasklist_lock);
  unlock_creds:

  	mutex_unlock(&task->signal->cred_guard_mutex);

  out:

  	if (!retval) {

  		wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT,
  			    ptrace_trapping_sleep_fn, TASK_UNINTERRUPTIBLE);

  		proc_ptrace_connector(task, PTRACE_ATTACH);
  	}

  	return retval;
  }

  /**
   * ptrace_traceme  --  helper for PTRACE_TRACEME
   *
   * Performs checks and sets PT_PTRACED.
   * Should be used by all ptrace implementations for PTRACE_TRACEME.
   */

  static int ptrace_traceme(void)

  {
  	int ret = -EPERM;

  	write_lock_irq(&tasklist_lock);
  	/* Are we already being traced? */

  	if (!current->ptrace) {

  		ret = security_ptrace_traceme(current->parent);

  		/*
  		 * Check PF_EXITING to ensure ->real_parent has not passed
  		 * exit_ptrace(). Otherwise we don't report the error but
  		 * pretend ->real_parent untraces us right after return.
  		 */
  		if (!ret && !(current->real_parent->flags & PF_EXITING)) {
  			current->ptrace = PT_PTRACED;
  			__ptrace_link(current, current->real_parent);
  		}

  	}

  	write_unlock_irq(&tasklist_lock);

  	return ret;
  }

  /*
   * Called with irqs disabled, returns true if childs should reap themselves.
   */
  static int ignoring_children(struct sighand_struct *sigh)
  {
  	int ret;
  	spin_lock(&sigh->siglock);
  	ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
  	      (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
  	spin_unlock(&sigh->siglock);
  	return ret;
  }
  
  /*
   * Called with tasklist_lock held for writing.
   * Unlink a traced task, and clean it up if it was a traced zombie.
   * Return true if it needs to be reaped with release_task().
   * (We can't call release_task() here because we already hold tasklist_lock.)
   *
   * If it's a zombie, our attachedness prevented normal parent notification
   * or self-reaping.  Do notification now if it would have happened earlier.
   * If it should reap itself, return true.
   *

   * If it's our own child, there is no notification to do. But if our normal
   * children self-reap, then this child was prevented by ptrace and we must
   * reap it now, in that case we must also wake up sub-threads sleeping in
   * do_wait().

   */
  static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
  {

  	bool dead;

  	__ptrace_unlink(p);

  	if (p->exit_state != EXIT_ZOMBIE)
  		return false;
  
  	dead = !thread_group_leader(p);
  
  	if (!dead && thread_group_empty(p)) {
  		if (!same_thread_group(p->real_parent, tracer))
  			dead = do_notify_parent(p, p->exit_signal);
  		else if (ignoring_children(tracer->sighand)) {
  			__wake_up_parent(p, tracer);

  			dead = true;

  		}
  	}

  	/* Mark it as in the process of being reaped. */
  	if (dead)
  		p->exit_state = EXIT_DEAD;
  	return dead;

  }

  static int ptrace_detach(struct task_struct *child, unsigned int data)

  {

  	bool dead = false;

  	if (!valid_signal(data))

  		return -EIO;

  
  	/* Architecture-specific hardware disable .. */
  	ptrace_disable(child);

  	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

  	write_lock_irq(&tasklist_lock);

  	/*
  	 * This child can be already killed. Make sure de_thread() or
  	 * our sub-thread doing do_wait() didn't do release_task() yet.
  	 */

  	if (child->ptrace) {
  		child->exit_code = data;

  		dead = __ptrace_detach(current, child);

  	}

  	write_unlock_irq(&tasklist_lock);

  	proc_ptrace_connector(child, PTRACE_DETACH);

  	if (unlikely(dead))
  		release_task(child);

  	return 0;
  }

  /*

   * Detach all tasks we were using ptrace on. Called with tasklist held
   * for writing, and returns with it held too. But note it can release
   * and reacquire the lock.

   */
  void exit_ptrace(struct task_struct *tracer)

  	__releases(&tasklist_lock)
  	__acquires(&tasklist_lock)

  {
  	struct task_struct *p, *n;
  	LIST_HEAD(ptrace_dead);

  	if (likely(list_empty(&tracer->ptraced)))
  		return;

  	list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
  		if (__ptrace_detach(tracer, p))
  			list_add(&p->ptrace_entry, &ptrace_dead);
  	}

  	write_unlock_irq(&tasklist_lock);

  	BUG_ON(!list_empty(&tracer->ptraced));
  
  	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
  		list_del_init(&p->ptrace_entry);
  		release_task(p);
  	}

  
  	write_lock_irq(&tasklist_lock);

  }

  int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
  {
  	int copied = 0;
  
  	while (len > 0) {
  		char buf[128];
  		int this_len, retval;
  
  		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
  		retval = access_process_vm(tsk, src, buf, this_len, 0);
  		if (!retval) {
  			if (copied)
  				break;
  			return -EIO;
  		}
  		if (copy_to_user(dst, buf, retval))
  			return -EFAULT;
  		copied += retval;
  		src += retval;
  		dst += retval;

  		len -= retval;

  	}
  	return copied;
  }
  
  int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
  {
  	int copied = 0;
  
  	while (len > 0) {
  		char buf[128];
  		int this_len, retval;
  
  		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
  		if (copy_from_user(buf, src, this_len))
  			return -EFAULT;
  		retval = access_process_vm(tsk, dst, buf, this_len, 1);
  		if (!retval) {
  			if (copied)
  				break;
  			return -EIO;
  		}
  		copied += retval;
  		src += retval;
  		dst += retval;

  		len -= retval;

  	}
  	return copied;
  }

  static int ptrace_setoptions(struct task_struct *child, unsigned long data)

  {
  	child->ptrace &= ~PT_TRACE_MASK;
  
  	if (data & PTRACE_O_TRACESYSGOOD)
  		child->ptrace |= PT_TRACESYSGOOD;
  
  	if (data & PTRACE_O_TRACEFORK)
  		child->ptrace |= PT_TRACE_FORK;
  
  	if (data & PTRACE_O_TRACEVFORK)
  		child->ptrace |= PT_TRACE_VFORK;
  
  	if (data & PTRACE_O_TRACECLONE)
  		child->ptrace |= PT_TRACE_CLONE;
  
  	if (data & PTRACE_O_TRACEEXEC)
  		child->ptrace |= PT_TRACE_EXEC;
  
  	if (data & PTRACE_O_TRACEVFORKDONE)
  		child->ptrace |= PT_TRACE_VFORK_DONE;
  
  	if (data & PTRACE_O_TRACEEXIT)
  		child->ptrace |= PT_TRACE_EXIT;
  
  	return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
  }

  static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)

  {

  	unsigned long flags;

  	int error = -ESRCH;

  	if (lock_task_sighand(child, &flags)) {

  		error = -EINVAL;

  		if (likely(child->last_siginfo != NULL)) {

  			*info = *child->last_siginfo;

  			error = 0;
  		}

  		unlock_task_sighand(child, &flags);

  	}

  	return error;
  }

  static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)

  {

  	unsigned long flags;

  	int error = -ESRCH;

  	if (lock_task_sighand(child, &flags)) {

  		error = -EINVAL;

  		if (likely(child->last_siginfo != NULL)) {

  			*child->last_siginfo = *info;

  			error = 0;
  		}

  		unlock_task_sighand(child, &flags);

  	}

  	return error;
  }

  
  #ifdef PTRACE_SINGLESTEP
  #define is_singlestep(request)		((request) == PTRACE_SINGLESTEP)
  #else
  #define is_singlestep(request)		0
  #endif

  #ifdef PTRACE_SINGLEBLOCK
  #define is_singleblock(request)		((request) == PTRACE_SINGLEBLOCK)
  #else
  #define is_singleblock(request)		0
  #endif

  #ifdef PTRACE_SYSEMU
  #define is_sysemu_singlestep(request)	((request) == PTRACE_SYSEMU_SINGLESTEP)
  #else
  #define is_sysemu_singlestep(request)	0
  #endif

  static int ptrace_resume(struct task_struct *child, long request,
  			 unsigned long data)

  {
  	if (!valid_signal(data))
  		return -EIO;
  
  	if (request == PTRACE_SYSCALL)
  		set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
  	else
  		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
  
  #ifdef TIF_SYSCALL_EMU
  	if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
  		set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
  	else
  		clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
  #endif

  	if (is_singleblock(request)) {
  		if (unlikely(!arch_has_block_step()))
  			return -EIO;
  		user_enable_block_step(child);
  	} else if (is_singlestep(request) || is_sysemu_singlestep(request)) {

  		if (unlikely(!arch_has_single_step()))
  			return -EIO;
  		user_enable_single_step(child);

  	} else {

  		user_disable_single_step(child);

  	}

  
  	child->exit_code = data;

  	wake_up_state(child, __TASK_TRACED);

  
  	return 0;
  }

  #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
  
  static const struct user_regset *
  find_regset(const struct user_regset_view *view, unsigned int type)
  {
  	const struct user_regset *regset;
  	int n;
  
  	for (n = 0; n < view->n; ++n) {
  		regset = view->regsets + n;
  		if (regset->core_note_type == type)
  			return regset;
  	}
  
  	return NULL;
  }
  
  static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
  			 struct iovec *kiov)
  {
  	const struct user_regset_view *view = task_user_regset_view(task);
  	const struct user_regset *regset = find_regset(view, type);
  	int regset_no;
  
  	if (!regset || (kiov->iov_len % regset->size) != 0)

  		return -EINVAL;

  
  	regset_no = regset - view->regsets;
  	kiov->iov_len = min(kiov->iov_len,
  			    (__kernel_size_t) (regset->n * regset->size));
  
  	if (req == PTRACE_GETREGSET)
  		return copy_regset_to_user(task, view, regset_no, 0,
  					   kiov->iov_len, kiov->iov_base);
  	else
  		return copy_regset_from_user(task, view, regset_no, 0,
  					     kiov->iov_len, kiov->iov_base);
  }
  
  #endif

  int ptrace_request(struct task_struct *child, long request,

  		   unsigned long addr, unsigned long data)

  {

  	bool seized = child->ptrace & PT_SEIZED;

  	int ret = -EIO;

  	siginfo_t siginfo, *si;

  	void __user *datavp = (void __user *) data;
  	unsigned long __user *datalp = datavp;

  	unsigned long flags;

  
  	switch (request) {

  	case PTRACE_PEEKTEXT:
  	case PTRACE_PEEKDATA:
  		return generic_ptrace_peekdata(child, addr, data);
  	case PTRACE_POKETEXT:
  	case PTRACE_POKEDATA:
  		return generic_ptrace_pokedata(child, addr, data);

  #ifdef PTRACE_OLDSETOPTIONS
  	case PTRACE_OLDSETOPTIONS:
  #endif
  	case PTRACE_SETOPTIONS:
  		ret = ptrace_setoptions(child, data);
  		break;
  	case PTRACE_GETEVENTMSG:

  		ret = put_user(child->ptrace_message, datalp);

  		break;

  	case PTRACE_GETSIGINFO:

  		ret = ptrace_getsiginfo(child, &siginfo);
  		if (!ret)

  			ret = copy_siginfo_to_user(datavp, &siginfo);

  		break;

  	case PTRACE_SETSIGINFO:

  		if (copy_from_user(&siginfo, datavp, sizeof siginfo))

  			ret = -EFAULT;
  		else
  			ret = ptrace_setsiginfo(child, &siginfo);

  		break;

  	case PTRACE_INTERRUPT:
  		/*
  		 * Stop tracee without any side-effect on signal or job
  		 * control.  At least one trap is guaranteed to happen
  		 * after this request.  If @child is already trapped, the
  		 * current trap is not disturbed and another trap will
  		 * happen after the current trap is ended with PTRACE_CONT.
  		 *
  		 * The actual trap might not be PTRACE_EVENT_STOP trap but
  		 * the pending condition is cleared regardless.
  		 */
  		if (unlikely(!seized || !lock_task_sighand(child, &flags)))
  			break;

  		/*
  		 * INTERRUPT doesn't disturb existing trap sans one
  		 * exception.  If ptracer issued LISTEN for the current
  		 * STOP, this INTERRUPT should clear LISTEN and re-trap
  		 * tracee into STOP.
  		 */

  		if (likely(task_set_jobctl_pending(child, JOBCTL_TRAP_STOP)))

  			signal_wake_up(child, child->jobctl & JOBCTL_LISTENING);
  
  		unlock_task_sighand(child, &flags);
  		ret = 0;
  		break;
  
  	case PTRACE_LISTEN:
  		/*
  		 * Listen for events.  Tracee must be in STOP.  It's not
  		 * resumed per-se but is not considered to be in TRACED by
  		 * wait(2) or ptrace(2).  If an async event (e.g. group
  		 * stop state change) happens, tracee will enter STOP trap
  		 * again.  Alternatively, ptracer can issue INTERRUPT to
  		 * finish listening and re-trap tracee into STOP.
  		 */
  		if (unlikely(!seized || !lock_task_sighand(child, &flags)))
  			break;
  
  		si = child->last_siginfo;

  		if (likely(si && (si->si_code >> 8) == PTRACE_EVENT_STOP)) {
  			child->jobctl |= JOBCTL_LISTENING;
  			/*
  			 * If NOTIFY is set, it means event happened between
  			 * start of this trap and now.  Trigger re-trap.
  			 */
  			if (child->jobctl & JOBCTL_TRAP_NOTIFY)
  				signal_wake_up(child, true);
  			ret = 0;
  		}

  		unlock_task_sighand(child, &flags);

  		break;

  	case PTRACE_DETACH:	 /* detach a process that was attached. */
  		ret = ptrace_detach(child, data);
  		break;

  #ifdef CONFIG_BINFMT_ELF_FDPIC
  	case PTRACE_GETFDPIC: {

  		struct mm_struct *mm = get_task_mm(child);

  		unsigned long tmp = 0;

  		ret = -ESRCH;
  		if (!mm)
  			break;

  		switch (addr) {
  		case PTRACE_GETFDPIC_EXEC:

  			tmp = mm->context.exec_fdpic_loadmap;

  			break;
  		case PTRACE_GETFDPIC_INTERP:

  			tmp = mm->context.interp_fdpic_loadmap;

  			break;
  		default:
  			break;
  		}

  		mmput(mm);

  		ret = put_user(tmp, datalp);

  		break;
  	}
  #endif

  #ifdef PTRACE_SINGLESTEP
  	case PTRACE_SINGLESTEP:
  #endif

  #ifdef PTRACE_SINGLEBLOCK
  	case PTRACE_SINGLEBLOCK:
  #endif

  #ifdef PTRACE_SYSEMU
  	case PTRACE_SYSEMU:
  	case PTRACE_SYSEMU_SINGLESTEP:
  #endif
  	case PTRACE_SYSCALL:
  	case PTRACE_CONT:
  		return ptrace_resume(child, request, data);
  
  	case PTRACE_KILL:
  		if (child->exit_state)	/* already dead */
  			return 0;
  		return ptrace_resume(child, request, SIGKILL);

  #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
  	case PTRACE_GETREGSET:
  	case PTRACE_SETREGSET:
  	{
  		struct iovec kiov;

  		struct iovec __user *uiov = datavp;

  
  		if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
  			return -EFAULT;
  
  		if (__get_user(kiov.iov_base, &uiov->iov_base) ||
  		    __get_user(kiov.iov_len, &uiov->iov_len))
  			return -EFAULT;
  
  		ret = ptrace_regset(child, request, addr, &kiov);
  		if (!ret)
  			ret = __put_user(kiov.iov_len, &uiov->iov_len);
  		break;
  	}
  #endif

  	default:
  		break;
  	}
  
  	return ret;
  }

  static struct task_struct *ptrace_get_task_struct(pid_t pid)

  {
  	struct task_struct *child;

  	rcu_read_lock();

  	child = find_task_by_vpid(pid);

  	if (child)
  		get_task_struct(child);

  	rcu_read_unlock();

  	if (!child)

  		return ERR_PTR(-ESRCH);
  	return child;

  }

  #ifndef arch_ptrace_attach
  #define arch_ptrace_attach(child)	do { } while (0)
  #endif

  SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
  		unsigned long, data)

  {
  	struct task_struct *child;
  	long ret;

  	if (request == PTRACE_TRACEME) {
  		ret = ptrace_traceme();

  		if (!ret)
  			arch_ptrace_attach(current);

  		goto out;

  	}
  
  	child = ptrace_get_task_struct(pid);
  	if (IS_ERR(child)) {
  		ret = PTR_ERR(child);
  		goto out;
  	}

  	if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
  		ret = ptrace_attach(child, request, data);

  		/*
  		 * Some architectures need to do book-keeping after
  		 * a ptrace attach.
  		 */
  		if (!ret)
  			arch_ptrace_attach(child);

  		goto out_put_task_struct;

  	}

  	ret = ptrace_check_attach(child, request == PTRACE_KILL ||
  				  request == PTRACE_INTERRUPT);

  	if (ret < 0)
  		goto out_put_task_struct;
  
  	ret = arch_ptrace(child, request, addr, data);

  
   out_put_task_struct:
  	put_task_struct(child);
   out:

  	return ret;
  }

  int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
  			    unsigned long data)

  {
  	unsigned long tmp;
  	int copied;
  
  	copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
  	if (copied != sizeof(tmp))
  		return -EIO;
  	return put_user(tmp, (unsigned long __user *)data);
  }

  int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
  			    unsigned long data)

  {
  	int copied;
  
  	copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
  	return (copied == sizeof(data)) ? 0 : -EIO;
  }

  #if defined CONFIG_COMPAT

  #include <linux/compat.h>
  
  int compat_ptrace_request(struct task_struct *child, compat_long_t request,
  			  compat_ulong_t addr, compat_ulong_t data)
  {
  	compat_ulong_t __user *datap = compat_ptr(data);
  	compat_ulong_t word;

  	siginfo_t siginfo;

  	int ret;
  
  	switch (request) {
  	case PTRACE_PEEKTEXT:
  	case PTRACE_PEEKDATA:
  		ret = access_process_vm(child, addr, &word, sizeof(word), 0);
  		if (ret != sizeof(word))
  			ret = -EIO;
  		else
  			ret = put_user(word, datap);
  		break;
  
  	case PTRACE_POKETEXT:
  	case PTRACE_POKEDATA:
  		ret = access_process_vm(child, addr, &data, sizeof(data), 1);
  		ret = (ret != sizeof(data) ? -EIO : 0);
  		break;
  
  	case PTRACE_GETEVENTMSG:
  		ret = put_user((compat_ulong_t) child->ptrace_message, datap);
  		break;

  	case PTRACE_GETSIGINFO:
  		ret = ptrace_getsiginfo(child, &siginfo);
  		if (!ret)
  			ret = copy_siginfo_to_user32(
  				(struct compat_siginfo __user *) datap,
  				&siginfo);
  		break;
  
  	case PTRACE_SETSIGINFO:
  		memset(&siginfo, 0, sizeof siginfo);
  		if (copy_siginfo_from_user32(
  			    &siginfo, (struct compat_siginfo __user *) datap))
  			ret = -EFAULT;
  		else
  			ret = ptrace_setsiginfo(child, &siginfo);
  		break;

  #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
  	case PTRACE_GETREGSET:
  	case PTRACE_SETREGSET:
  	{
  		struct iovec kiov;
  		struct compat_iovec __user *uiov =
  			(struct compat_iovec __user *) datap;
  		compat_uptr_t ptr;
  		compat_size_t len;
  
  		if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
  			return -EFAULT;
  
  		if (__get_user(ptr, &uiov->iov_base) ||
  		    __get_user(len, &uiov->iov_len))
  			return -EFAULT;
  
  		kiov.iov_base = compat_ptr(ptr);
  		kiov.iov_len = len;
  
  		ret = ptrace_regset(child, request, addr, &kiov);
  		if (!ret)
  			ret = __put_user(kiov.iov_len, &uiov->iov_len);
  		break;
  	}
  #endif

  	default:
  		ret = ptrace_request(child, request, addr, data);
  	}
  
  	return ret;
  }

  asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
  				  compat_long_t addr, compat_long_t data)
  {
  	struct task_struct *child;
  	long ret;

  	if (request == PTRACE_TRACEME) {
  		ret = ptrace_traceme();
  		goto out;
  	}
  
  	child = ptrace_get_task_struct(pid);
  	if (IS_ERR(child)) {
  		ret = PTR_ERR(child);
  		goto out;
  	}

  	if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
  		ret = ptrace_attach(child, request, data);

  		/*
  		 * Some architectures need to do book-keeping after
  		 * a ptrace attach.
  		 */
  		if (!ret)
  			arch_ptrace_attach(child);
  		goto out_put_task_struct;
  	}

  	ret = ptrace_check_attach(child, request == PTRACE_KILL ||
  				  request == PTRACE_INTERRUPT);

  	if (!ret)
  		ret = compat_arch_ptrace(child, request, addr, data);
  
   out_put_task_struct:
  	put_task_struct(child);
   out:

  	return ret;
  }

  #endif	/* CONFIG_COMPAT */

  
  #ifdef CONFIG_HAVE_HW_BREAKPOINT
  int ptrace_get_breakpoints(struct task_struct *tsk)
  {
  	if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
  		return 0;
  
  	return -1;
  }
  
  void ptrace_put_breakpoints(struct task_struct *tsk)
  {
  	if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
  		flush_ptrace_hw_breakpoint(tsk);
  }
  #endif /* CONFIG_HAVE_HW_BREAKPOINT */