// SPDX-License-Identifier: GPL-2.0-only

  /*
   * 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/sched/mm.h>

  #include <linux/sched/coredump.h>

  #include <linux/sched/task.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/uio.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>

  #include <linux/compat.h>

  #include <linux/sched/signal.h>

  #include <asm/syscall.h>	/* for syscall_get_* */

  /*
   * Access another process' address space via ptrace.
   * Source/target buffer must be kernel space,
   * Do not walk the page table directly, use get_user_pages
   */
  int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
  		     void *buf, int len, unsigned int gup_flags)
  {
  	struct mm_struct *mm;
  	int ret;
  
  	mm = get_task_mm(tsk);
  	if (!mm)
  		return 0;
  
  	if (!tsk->ptrace ||
  	    (current != tsk->parent) ||
  	    ((get_dumpable(mm) != SUID_DUMP_USER) &&
  	     !ptracer_capable(tsk, mm->user_ns))) {
  		mmput(mm);
  		return 0;
  	}
  
  	ret = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
  	mmput(mm);
  
  	return ret;
  }

  void __ptrace_link(struct task_struct *child, struct task_struct *new_parent,
  		   const struct cred *ptracer_cred)
  {
  	BUG_ON(!list_empty(&child->ptrace_entry));
  	list_add(&child->ptrace_entry, &new_parent->ptraced);
  	child->parent = new_parent;
  	child->ptracer_cred = get_cred(ptracer_cred);
  }

  /*

   * 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.
   */

  static void ptrace_link(struct task_struct *child, struct task_struct *new_parent)

  {

  	__ptrace_link(child, new_parent, current_cred());

  }

  /**
   * __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)

  {

  	const struct cred *old_cred;

  	BUG_ON(!child->ptrace);

  	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

  #ifdef TIF_SYSCALL_EMU
  	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
  #endif

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

  	old_cred = child->ptracer_cred;
  	child->ptracer_cred = NULL;
  	put_cred(old_cred);

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

  	child->ptrace = 0;

  	/*

  	 * 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))

  		ptrace_signal_wake_up(child, true);

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

  }

  /* Ensure that nothing can wake it up, even SIGKILL */
  static bool ptrace_freeze_traced(struct task_struct *task)
  {
  	bool ret = false;
  
  	/* Lockless, nobody but us can set this flag */
  	if (task->jobctl & JOBCTL_LISTENING)
  		return ret;
  
  	spin_lock_irq(&task->sighand->siglock);
  	if (task_is_traced(task) && !__fatal_signal_pending(task)) {
  		task->state = __TASK_TRACED;
  		ret = true;
  	}
  	spin_unlock_irq(&task->sighand->siglock);
  
  	return ret;
  }
  
  static void ptrace_unfreeze_traced(struct task_struct *task)
  {
  	if (task->state != __TASK_TRACED)
  		return;
  
  	WARN_ON(!task->ptrace || task->parent != current);

  	/*
  	 * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely.
  	 * Recheck state under the lock to close this race.
  	 */

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

  	if (task->state == __TASK_TRACED) {
  		if (__fatal_signal_pending(task))
  			wake_up_state(task, __TASK_TRACED);
  		else
  			task->state = TASK_TRACED;
  	}

  	spin_unlock_irq(&task->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.

   */

  static 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 && child->parent == current) {
  		WARN_ON(child->state == __TASK_TRACED);

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

  		if (ignore_state || ptrace_freeze_traced(child))

  			ret = 0;

  	}
  	read_unlock(&tasklist_lock);

  	if (!ret && !ignore_state) {
  		if (!wait_task_inactive(child, __TASK_TRACED)) {
  			/*
  			 * This can only happen if may_ptrace_stop() fails and
  			 * ptrace_stop() changes ->state back to TASK_RUNNING,
  			 * so we should not worry about leaking __TASK_TRACED.
  			 */
  			WARN_ON(child->state == __TASK_TRACED);
  			ret = -ESRCH;
  		}
  	}

  	return ret;
  }

  static bool ptrace_has_cap(struct user_namespace *ns, unsigned int mode)

  {
  	if (mode & PTRACE_MODE_NOAUDIT)

  		return ns_capable_noaudit(ns, CAP_SYS_PTRACE);
  	return ns_capable(ns, CAP_SYS_PTRACE);

  }

  /* Returns 0 on success, -errno on denial. */
  static int __ptrace_may_access(struct task_struct *task, unsigned int mode)

  {

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

  	struct mm_struct *mm;

  	kuid_t caller_uid;
  	kgid_t caller_gid;
  
  	if (!(mode & PTRACE_MODE_FSCREDS) == !(mode & PTRACE_MODE_REALCREDS)) {
  		WARN(1, "denying ptrace access check without PTRACE_MODE_*CREDS
  ");
  		return -EPERM;
  	}

  	/* 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.
  	 */

  	/* Don't let security modules deny introspection */

  	if (same_thread_group(task, current))

  		return 0;

  	rcu_read_lock();

  	if (mode & PTRACE_MODE_FSCREDS) {
  		caller_uid = cred->fsuid;
  		caller_gid = cred->fsgid;
  	} else {
  		/*
  		 * Using the euid would make more sense here, but something
  		 * in userland might rely on the old behavior, and this
  		 * shouldn't be a security problem since
  		 * PTRACE_MODE_REALCREDS implies that the caller explicitly
  		 * used a syscall that requests access to another process
  		 * (and not a filesystem syscall to procfs).
  		 */
  		caller_uid = cred->uid;
  		caller_gid = cred->gid;
  	}

  	tcred = __task_cred(task);

  	if (uid_eq(caller_uid, tcred->euid) &&
  	    uid_eq(caller_uid, tcred->suid) &&
  	    uid_eq(caller_uid, tcred->uid)  &&
  	    gid_eq(caller_gid, tcred->egid) &&
  	    gid_eq(caller_gid, tcred->sgid) &&
  	    gid_eq(caller_gid, tcred->gid))

  		goto ok;

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

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

  	rcu_read_unlock();

  	/*
  	 * If a task drops privileges and becomes nondumpable (through a syscall
  	 * like setresuid()) while we are trying to access it, we must ensure
  	 * that the dumpability is read after the credentials; otherwise,
  	 * we may be able to attach to a task that we shouldn't be able to
  	 * attach to (as if the task had dropped privileges without becoming
  	 * nondumpable).
  	 * Pairs with a write barrier in commit_creds().
  	 */
  	smp_rmb();

  	mm = task->mm;
  	if (mm &&
  	    ((get_dumpable(mm) != SUID_DUMP_USER) &&

  	     !ptrace_has_cap(mm->user_ns, 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 addr,

  			 unsigned long flags)

  {

  	bool seize = (request == PTRACE_SEIZE);

  	int retval;

  	retval = -EIO;

  	if (seize) {
  		if (addr != 0)
  			goto out;

  		if (flags & ~(unsigned long)PTRACE_O_MASK)
  			goto out;
  		flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
  	} else {
  		flags = PT_PTRACED;
  	}

  	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;

  	 * 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_REALCREDS);

  	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;

  	if (seize)

  		flags |= PT_SEIZED;

  	task->ptrace = flags;

  	ptrace_link(task, current);

  
  	/* SEIZE doesn't trap tracee on attach */
  	if (!seize)

  		send_sig_info(SIGSTOP, SEND_SIG_PRIV, 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_state(task, __TASK_STOPPED);

  
  	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) {

  		/*
  		 * We do not bother to change retval or clear JOBCTL_TRAPPING
  		 * if wait_on_bit() was interrupted by SIGKILL. The tracer will
  		 * not return to user-mode, it will exit and clear this bit in
  		 * __ptrace_unlink() if it wasn't already cleared by the tracee;
  		 * and until then nobody can ptrace this task.
  		 */
  		wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, TASK_KILLABLE);

  		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)

  {

  	if (!valid_signal(data))

  		return -EIO;

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

  	write_lock_irq(&tasklist_lock);

  	/*

  	 * We rely on ptrace_freeze_traced(). It can't be killed and
  	 * untraced by another thread, it can't be a zombie.

  	 */

  	WARN_ON(!child->ptrace || child->exit_state);
  	/*
  	 * tasklist_lock avoids the race with wait_task_stopped(), see
  	 * the comment in ptrace_resume().
  	 */
  	child->exit_code = data;
  	__ptrace_detach(current, child);

  	write_unlock_irq(&tasklist_lock);

  	proc_ptrace_connector(child, PTRACE_DETACH);

  	return 0;
  }

  /*

   * Detach all tasks we were using ptrace on. Called with tasklist held

   * for writing.

   */

  void exit_ptrace(struct task_struct *tracer, struct list_head *dead)

  {
  	struct task_struct *p, *n;

  	list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {

  		if (unlikely(p->ptrace & PT_EXITKILL))

  			send_sig_info(SIGKILL, SEND_SIG_PRIV, p);

  		if (__ptrace_detach(tracer, p))

  			list_add(&p->ptrace_entry, dead);

  	}
  }

  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 = ptrace_access_vm(tsk, src, buf, this_len, FOLL_FORCE);

  		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 = ptrace_access_vm(tsk, dst, buf, this_len,

  				FOLL_FORCE | FOLL_WRITE);

  		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)

  {

  	unsigned flags;

  	if (data & ~(unsigned long)PTRACE_O_MASK)
  		return -EINVAL;

  	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {

  		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
  		    !IS_ENABLED(CONFIG_SECCOMP))

  			return -EINVAL;
  
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  
  		if (seccomp_mode(&current->seccomp) != SECCOMP_MODE_DISABLED ||
  		    current->ptrace & PT_SUSPEND_SECCOMP)
  			return -EPERM;
  	}

  	/* Avoid intermediate state when all opts are cleared */
  	flags = child->ptrace;
  	flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
  	flags |= (data << PT_OPT_FLAG_SHIFT);
  	child->ptrace = flags;

  	return 0;

  }

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

  {

  	unsigned long flags;

  	int error = -ESRCH;

  	if (lock_task_sighand(child, &flags)) {

  		error = -EINVAL;

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

  			copy_siginfo(info, child->last_siginfo);

  			error = 0;
  		}

  		unlock_task_sighand(child, &flags);

  	}

  	return error;
  }

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

  {

  	unsigned long flags;

  	int error = -ESRCH;

  	if (lock_task_sighand(child, &flags)) {

  		error = -EINVAL;

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

  			copy_siginfo(child->last_siginfo, info);

  			error = 0;
  		}

  		unlock_task_sighand(child, &flags);

  	}

  	return error;
  }

  static int ptrace_peek_siginfo(struct task_struct *child,
  				unsigned long addr,
  				unsigned long data)
  {
  	struct ptrace_peeksiginfo_args arg;
  	struct sigpending *pending;
  	struct sigqueue *q;
  	int ret, i;
  
  	ret = copy_from_user(&arg, (void __user *) addr,
  				sizeof(struct ptrace_peeksiginfo_args));
  	if (ret)
  		return -EFAULT;
  
  	if (arg.flags & ~PTRACE_PEEKSIGINFO_SHARED)
  		return -EINVAL; /* unknown flags */
  
  	if (arg.nr < 0)
  		return -EINVAL;

  	/* Ensure arg.off fits in an unsigned long */
  	if (arg.off > ULONG_MAX)
  		return 0;

  	if (arg.flags & PTRACE_PEEKSIGINFO_SHARED)
  		pending = &child->signal->shared_pending;
  	else
  		pending = &child->pending;
  
  	for (i = 0; i < arg.nr; ) {

  		kernel_siginfo_t info;

  		unsigned long off = arg.off + i;
  		bool found = false;

  
  		spin_lock_irq(&child->sighand->siglock);
  		list_for_each_entry(q, &pending->list, list) {
  			if (!off--) {

  				found = true;

  				copy_siginfo(&info, &q->info);
  				break;
  			}
  		}
  		spin_unlock_irq(&child->sighand->siglock);

  		if (!found) /* beyond the end of the list */

  			break;
  
  #ifdef CONFIG_COMPAT

  		if (unlikely(in_compat_syscall())) {

  			compat_siginfo_t __user *uinfo = compat_ptr(data);

  			if (copy_siginfo_to_user32(uinfo, &info)) {

  				ret = -EFAULT;
  				break;
  			}

  		} else
  #endif
  		{
  			siginfo_t __user *uinfo = (siginfo_t __user *) data;

  			if (copy_siginfo_to_user(uinfo, &info)) {

  				ret = -EFAULT;
  				break;
  			}

  		}
  
  		data += sizeof(siginfo_t);
  		i++;
  
  		if (signal_pending(current))
  			break;
  
  		cond_resched();
  	}
  
  	if (i > 0)
  		return i;
  
  	return ret;
  }

  
  #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)

  {

  	bool need_siglock;

  	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);

  	}

  	/*
  	 * Change ->exit_code and ->state under siglock to avoid the race
  	 * with wait_task_stopped() in between; a non-zero ->exit_code will
  	 * wrongly look like another report from tracee.
  	 *
  	 * Note that we need siglock even if ->exit_code == data and/or this
  	 * status was not reported yet, the new status must not be cleared by
  	 * wait_task_stopped() after resume.
  	 *
  	 * If data == 0 we do not care if wait_task_stopped() reports the old
  	 * status and clears the code too; this can't race with the tracee, it
  	 * takes siglock after resume.
  	 */
  	need_siglock = data && !thread_group_empty(current);
  	if (need_siglock)
  		spin_lock_irq(&child->sighand->siglock);

  	child->exit_code = data;

  	wake_up_state(child, __TASK_TRACED);

  	if (need_siglock)
  		spin_unlock_irq(&child->sighand->siglock);

  
  	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);
  }

  /*
   * This is declared in linux/regset.h and defined in machine-dependent
   * code.  We put the export here, near the primary machine-neutral use,
   * to ensure no machine forgets it.
   */
  EXPORT_SYMBOL_GPL(task_user_regset_view);

  
  static unsigned long
  ptrace_get_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
  			      struct ptrace_syscall_info *info)
  {
  	unsigned long args[ARRAY_SIZE(info->entry.args)];
  	int i;
  
  	info->op = PTRACE_SYSCALL_INFO_ENTRY;
  	info->entry.nr = syscall_get_nr(child, regs);
  	syscall_get_arguments(child, regs, args);
  	for (i = 0; i < ARRAY_SIZE(args); i++)
  		info->entry.args[i] = args[i];
  
  	/* args is the last field in struct ptrace_syscall_info.entry */
  	return offsetofend(struct ptrace_syscall_info, entry.args);
  }
  
  static unsigned long
  ptrace_get_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
  				struct ptrace_syscall_info *info)
  {
  	/*
  	 * As struct ptrace_syscall_info.entry is currently a subset
  	 * of struct ptrace_syscall_info.seccomp, it makes sense to
  	 * initialize that subset using ptrace_get_syscall_info_entry().
  	 * This can be reconsidered in the future if these structures
  	 * diverge significantly enough.
  	 */
  	ptrace_get_syscall_info_entry(child, regs, info);
  	info->op = PTRACE_SYSCALL_INFO_SECCOMP;
  	info->seccomp.ret_data = child->ptrace_message;
  
  	/* ret_data is the last field in struct ptrace_syscall_info.seccomp */
  	return offsetofend(struct ptrace_syscall_info, seccomp.ret_data);
  }
  
  static unsigned long
  ptrace_get_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
  			     struct ptrace_syscall_info *info)
  {
  	info->op = PTRACE_SYSCALL_INFO_EXIT;
  	info->exit.rval = syscall_get_error(child, regs);
  	info->exit.is_error = !!info->exit.rval;
  	if (!info->exit.is_error)
  		info->exit.rval = syscall_get_return_value(child, regs);
  
  	/* is_error is the last field in struct ptrace_syscall_info.exit */
  	return offsetofend(struct ptrace_syscall_info, exit.is_error);
  }
  
  static int
  ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
  			void __user *datavp)
  {
  	struct pt_regs *regs = task_pt_regs(child);
  	struct ptrace_syscall_info info = {
  		.op = PTRACE_SYSCALL_INFO_NONE,
  		.arch = syscall_get_arch(child),
  		.instruction_pointer = instruction_pointer(regs),
  		.stack_pointer = user_stack_pointer(regs),
  	};
  	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
  	unsigned long write_size;
  
  	/*
  	 * This does not need lock_task_sighand() to access
  	 * child->last_siginfo because ptrace_freeze_traced()
  	 * called earlier by ptrace_check_attach() ensures that
  	 * the tracee cannot go away and clear its last_siginfo.
  	 */
  	switch (child->last_siginfo ? child->last_siginfo->si_code : 0) {
  	case SIGTRAP | 0x80:
  		switch (child->ptrace_message) {
  		case PTRACE_EVENTMSG_SYSCALL_ENTRY:
  			actual_size = ptrace_get_syscall_info_entry(child, regs,
  								    &info);
  			break;
  		case PTRACE_EVENTMSG_SYSCALL_EXIT:
  			actual_size = ptrace_get_syscall_info_exit(child, regs,
  								   &info);
  			break;
  		}
  		break;
  	case SIGTRAP | (PTRACE_EVENT_SECCOMP << 8):
  		actual_size = ptrace_get_syscall_info_seccomp(child, regs,
  							      &info);
  		break;
  	}
  
  	write_size = min(actual_size, user_size);
  	return copy_to_user(datavp, &info, write_size) ? -EFAULT : actual_size;
  }
  #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */

  int ptrace_request(struct task_struct *child, long request,

  		   unsigned long addr, unsigned long data)

  {

  	bool seized = child->ptrace & PT_SEIZED;

  	int ret = -EIO;

  	kernel_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_PEEKSIGINFO:
  		ret = ptrace_peek_siginfo(child, addr, data);
  		break;

  	case PTRACE_GETSIGINFO:

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

  			ret = copy_siginfo_to_user(datavp, &siginfo);

  		break;

  	case PTRACE_SETSIGINFO:

  		ret = copy_siginfo_from_user(&siginfo, datavp);
  		if (!ret)

  			ret = ptrace_setsiginfo(child, &siginfo);

  		break;

  	case PTRACE_GETSIGMASK: {
  		sigset_t *mask;

  		if (addr != sizeof(sigset_t)) {
  			ret = -EINVAL;
  			break;
  		}

  		if (test_tsk_restore_sigmask(child))
  			mask = &child->saved_sigmask;
  		else
  			mask = &child->blocked;
  
  		if (copy_to_user(datavp, mask, sizeof(sigset_t)))

  			ret = -EFAULT;
  		else
  			ret = 0;
  
  		break;

  	}

  
  	case PTRACE_SETSIGMASK: {
  		sigset_t new_set;
  
  		if (addr != sizeof(sigset_t)) {
  			ret = -EINVAL;
  			break;
  		}
  
  		if (copy_from_user(&new_set, datavp, sizeof(sigset_t))) {
  			ret = -EFAULT;
  			break;
  		}
  
  		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
  
  		/*
  		 * Every thread does recalc_sigpending() after resume, so
  		 * retarget_shared_pending() and recalc_sigpending() are not
  		 * called here.
  		 */
  		spin_lock_irq(&child->sighand->siglock);
  		child->blocked = new_set;
  		spin_unlock_irq(&child->sighand->siglock);

  		clear_tsk_restore_sigmask(child);

  		ret = 0;
  		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)))

  			ptrace_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)

  				ptrace_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(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;
  	}

  
  	case PTRACE_GET_SYSCALL_INFO:
  		ret = ptrace_get_syscall_info(child, addr, datavp);
  		break;

  #endif

  
  	case PTRACE_SECCOMP_GET_FILTER:
  		ret = seccomp_get_filter(child, addr, datavp);
  		break;

  	case PTRACE_SECCOMP_GET_METADATA:
  		ret = seccomp_get_metadata(child, addr, datavp);
  		break;

  	default:
  		break;
  	}
  
  	return ret;
  }

  #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 = find_get_task_by_vpid(pid);
  	if (!child) {
  		ret = -ESRCH;

  		goto out;
  	}

  	if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {

  		ret = ptrace_attach(child, request, addr, 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);

  	if (ret || request != PTRACE_DETACH)
  		ptrace_unfreeze_traced(child);

  
   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 = ptrace_access_vm(tsk, addr, &tmp, sizeof(tmp), FOLL_FORCE);

  	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 = ptrace_access_vm(tsk, addr, &data, sizeof(data),

  			FOLL_FORCE | FOLL_WRITE);

  	return (copied == sizeof(data)) ? 0 : -EIO;
  }

  #if defined CONFIG_COMPAT

  
  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;

  	kernel_siginfo_t siginfo;

  	int ret;
  
  	switch (request) {
  	case PTRACE_PEEKTEXT:
  	case PTRACE_PEEKDATA:

  		ret = ptrace_access_vm(child, addr, &word, sizeof(word),

  				FOLL_FORCE);

  		if (ret != sizeof(word))
  			ret = -EIO;
  		else
  			ret = put_user(word, datap);
  		break;
  
  	case PTRACE_POKETEXT:
  	case PTRACE_POKEDATA:

  		ret = ptrace_access_vm(child, addr, &data, sizeof(data),

  				FOLL_FORCE | FOLL_WRITE);

  		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:

  		ret = copy_siginfo_from_user32(
  			&siginfo, (struct compat_siginfo __user *) datap);
  		if (!ret)

  			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(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;
  }

  COMPAT_SYSCALL_DEFINE4(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 = find_get_task_by_vpid(pid);
  	if (!child) {
  		ret = -ESRCH;

  		goto out;
  	}

  	if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {

  		ret = ptrace_attach(child, request, addr, 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);

  		if (ret || request != PTRACE_DETACH)
  			ptrace_unfreeze_traced(child);
  	}

  
   out_put_task_struct:
  	put_task_struct(child);
   out:

  	return ret;
  }

  #endif	/* CONFIG_COMPAT */