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

  
  /*

   * 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;

  }

  /*
   * Turn a tracing stop into a normal stop now, since with no tracer there
   * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
   * signal sent that would resume the child, but didn't because it was in
   * TASK_TRACED, resume it now.
   * Requires that irqs be disabled.
   */

  static void ptrace_untrace(struct task_struct *child)

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

  	if (task_is_traced(child)) {

  		/*
  		 * If the group stop is completed or in progress,
  		 * this thread was already counted as stopped.
  		 */
  		if (child->signal->flags & SIGNAL_STOP_STOPPED ||
  		    child->signal->group_stop_count)

  			__set_task_state(child, TASK_STOPPED);

  		else

  			signal_wake_up(child, 1);

  	}
  	spin_unlock(&child->sighand->siglock);
  }
  
  /*
   * unptrace a task: move it back to its original parent and
   * remove it from the ptrace list.
   *
   * Must be called with the tasklist lock write-held.
   */

  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);

  	arch_ptrace_untrace(child);

  	if (task_is_traced(child))

  		ptrace_untrace(child);

  }
  
  /*
   * Check that we have indeed attached to the thing..
   */
  int ptrace_check_attach(struct task_struct *child, int kill)
  {
  	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) {

  		ret = 0;

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

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

  		if (task_is_stopped(child))

  			child->state = TASK_TRACED;

  		else if (!task_is_traced(child) && !kill)

  			ret = -ESRCH;

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

  	if (!ret && !kill)

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

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

  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->uid != tcred->euid ||
  	     cred->uid != tcred->suid ||
  	     cred->uid != tcred->uid  ||
  	     cred->gid != tcred->egid ||
  	     cred->gid != tcred->sgid ||
  	     cred->gid != tcred->gid) &&
  	    !capable(CAP_SYS_PTRACE)) {
  		rcu_read_unlock();

  		return -EPERM;

  	}
  	rcu_read_unlock();

  	smp_rmb();

  	if (task->mm)

  		dumpable = get_dumpable(task->mm);

  	if (!dumpable && !capable(CAP_SYS_PTRACE))

  		return -EPERM;

  	return security_ptrace_may_access(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;

  }

  int ptrace_attach(struct task_struct *task)
  {
  	int retval;

  	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 = mutex_lock_interruptible(&task->cred_guard_mutex);

  	if (retval < 0)

  		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 (capable(CAP_SYS_PTRACE))
  		task->ptrace |= PT_PTRACE_CAP;

  	__ptrace_link(task, current);

  	send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);

  
  	retval = 0;

  unlock_tasklist:
  	write_unlock_irq(&tasklist_lock);
  unlock_creds:

  	mutex_unlock(&task->cred_guard_mutex);

  out:

  	return retval;
  }

  /**
   * ptrace_traceme  --  helper for PTRACE_TRACEME
   *
   * Performs checks and sets PT_PTRACED.
   * Should be used by all ptrace implementations for PTRACE_TRACEME.
   */
  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.
   */
  static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
  {
  	__ptrace_unlink(p);
  
  	if (p->exit_state == EXIT_ZOMBIE) {
  		if (!task_detached(p) && thread_group_empty(p)) {
  			if (!same_thread_group(p->real_parent, tracer))
  				do_notify_parent(p, p->exit_signal);
  			else if (ignoring_children(tracer->sighand))
  				p->exit_signal = -1;
  		}
  		if (task_detached(p)) {
  			/* Mark it as in the process of being reaped. */
  			p->exit_state = EXIT_DEAD;
  			return true;
  		}
  	}
  
  	return false;
  }

  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);

  		if (!child->exit_state)
  			wake_up_process(child);

  	}

  	write_unlock_irq(&tasklist_lock);

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

  	return 0;
  }

  /*
   * Detach all tasks we were using ptrace on.
   */
  void exit_ptrace(struct task_struct *tracer)
  {
  	struct task_struct *p, *n;
  	LIST_HEAD(ptrace_dead);
  
  	write_lock_irq(&tasklist_lock);
  	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);
  	}
  }

  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, 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, 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_process(child);
  
  	return 0;
  }

  int ptrace_request(struct task_struct *child, long request,
  		   long addr, long data)
  {
  	int ret = -EIO;

  	siginfo_t siginfo;

  
  	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, (unsigned long __user *) data);
  		break;

  	case PTRACE_GETSIGINFO:

  		ret = ptrace_getsiginfo(child, &siginfo);
  		if (!ret)
  			ret = copy_siginfo_to_user((siginfo_t __user *) data,
  						   &siginfo);

  		break;

  	case PTRACE_SETSIGINFO:

  		if (copy_from_user(&siginfo, (siginfo_t __user *) data,
  				   sizeof siginfo))
  			ret = -EFAULT;
  		else
  			ret = ptrace_setsiginfo(child, &siginfo);

  		break;

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

  
  #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);

  	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, long, addr, long, data)

  {
  	struct task_struct *child;
  	long ret;
  
  	/*
  	 * This lock_kernel fixes a subtle race with suid exec
  	 */
  	lock_kernel();

  	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) {
  		ret = ptrace_attach(child);

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

  
   out_put_task_struct:
  	put_task_struct(child);
   out:
  	unlock_kernel();
  	return ret;
  }

  
  int generic_ptrace_peekdata(struct task_struct *tsk, long addr, 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, long addr, 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;

  	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;
  
  	/*
  	 * This lock_kernel fixes a subtle race with suid exec
  	 */
  	lock_kernel();
  	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) {
  		ret = ptrace_attach(child);
  		/*
  		 * 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);
  	if (!ret)
  		ret = compat_arch_ptrace(child, request, addr, data);
  
   out_put_task_struct:
  	put_task_struct(child);
   out:
  	unlock_kernel();
  	return ret;
  }

  #endif	/* CONFIG_COMPAT */