text: /*-
   * Copyright (C) 1994, David Greenman
   * Copyright (c) 1990, 1993
   *	The Regents of the University of California.  All rights reserved.
   * Copyright (C) 2010 Konstantin Belousov <kib@freebsd.org>
   *
   * This code is derived from software contributed to Berkeley by
   * the University of Utah, and William Jolitz.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
   */
  
  #include "opt_capsicum.h"
  #include "opt_ktrace.h"
  #include "opt_kdtrace.h"
  
  __FBSDID("$FreeBSD: release/9.1.0/sys/kern/subr_syscall.c 236648 2012-06-06 01:01:12Z kib $");
  
  #include <sys/capability.h>
  #include <sys/ktr.h>
  #ifdef KTRACE
  #include <sys/uio.h>
  #include <sys/ktrace.h>
  #endif
  #include <security/audit/audit.h>
  
  static inline int
  syscallenter(struct thread *td, struct syscall_args *sa)
  {
  	struct proc *p;
  	int error, traced;
  
  	PCPU_INC(cnt.v_syscall);
  	p = td->td_proc;
  
  	td->td_pticks = 0;
  	if (td->td_ucred != p->p_ucred)
  		cred_update_thread(td);
  	if (p->p_flag & P_TRACED) {
  		traced = 1;
  		PROC_LOCK(p);
  		td->td_dbgflags &= ~TDB_USERWR;
  		td->td_dbgflags |= TDB_SCE;
  		PROC_UNLOCK(p);
  	} else
  		traced = 0;
  	error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
  #ifdef KTRACE
  	if (KTRPOINT(td, KTR_SYSCALL))
  		ktrsyscall(sa->code, sa->narg, sa->args);
  #endif
  
  	CTR6(KTR_SYSC,
  "syscall: td=%p pid %d %s (%#lx, %#lx, %#lx)",
  	    td, td->td_proc->p_pid, syscallname(p, sa->code),
  	    sa->args[0], sa->args[1], sa->args[2]);
  
  	if (error == 0) {
  		STOPEVENT(p, S_SCE, sa->narg);
  		if (p->p_flag & P_TRACED && p->p_stops & S_PT_SCE) {
  			PROC_LOCK(p);
  			ptracestop((td), SIGTRAP);
  			PROC_UNLOCK(p);
  		}
  		if (td->td_dbgflags & TDB_USERWR) {
  			/*
  			 * Reread syscall number and arguments if
  			 * debugger modified registers or memory.
  			 */
  			error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
  #ifdef KTRACE
  			if (KTRPOINT(td, KTR_SYSCALL))
  				ktrsyscall(sa->code, sa->narg, sa->args);
  #endif
  			if (error != 0)
  				goto retval;
  		}
  
  #ifdef CAPABILITY_MODE
  		/*
  		 * In capability mode, we only allow access to system calls
  		 * flagged with SYF_CAPENABLED.
  		 */
  		if (IN_CAPABILITY_MODE(td) &&
  		    !(sa->callp->sy_flags & SYF_CAPENABLED)) {
  			error = ECAPMODE;
  			goto retval;
  		}
  #endif
  
  		error = syscall_thread_enter(td, sa->callp);
  		if (error != 0)
  			goto retval;
  
  #ifdef KDTRACE_HOOKS
  		/*
  		 * If the systrace module has registered it's probe
  		 * callback and if there is a probe active for the
  		 * syscall 'entry', process the probe.
  		 */
  		if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
  			(*systrace_probe_func)(sa->callp->sy_entry, sa->code,
  			    sa->callp, sa->args, 0);
  #endif
  
  		AUDIT_SYSCALL_ENTER(sa->code, td);
  		error = (sa->callp->sy_call)(td, sa->args);
  		AUDIT_SYSCALL_EXIT(error, td);
  
  		/* Save the latest error return value. */
  		if ((td->td_pflags & TDP_NERRNO) == 0)
  			td->td_errno = error;
  
  #ifdef KDTRACE_HOOKS
  		/*
  		 * If the systrace module has registered it's probe
  		 * callback and if there is a probe active for the
  		 * syscall 'return', process the probe.
  		 */
  		if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
  			(*systrace_probe_func)(sa->callp->sy_return, sa->code,
  			    sa->callp, NULL, (error) ? -1 : td->td_retval[0]);
  #endif
  		syscall_thread_exit(td, sa->callp);
  		CTR4(KTR_SYSC, "syscall: p=%p error=%d return %#lx %#lx",
  		    p, error, td->td_retval[0], td->td_retval[1]);
  	}
   retval:
  	if (traced) {
  		PROC_LOCK(p);
  		td->td_dbgflags &= ~TDB_SCE;
  		PROC_UNLOCK(p);
  	}
  	(p->p_sysent->sv_set_syscall_retval)(td, error);
  	return (error);
  }
  
  static inline void
  syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
  {
  	struct proc *p, *p2;
  	int traced;
  
  	p = td->td_proc;
  
  	/*
  	 * Check for misbehavior.
  	 */
  	WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
  	    syscallname(p, sa->code));
  	KASSERT(td->td_critnest == 0,
  	    ("System call %s returning in a critical section",
  	    syscallname(p, sa->code)));
  	KASSERT(td->td_locks == 0,
  	    ("System call %s returning with %d locks held",
  	     syscallname(p, sa->code), td->td_locks));
  	KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
  	    ("System call %s returning with pagefaults disabled",
  	     syscallname(p, sa->code)));
  	KASSERT((td->td_pflags & TDP_NOSLEEPING) == 0,
  	    ("System call %s returning with sleep disabled",
  	     syscallname(p, sa->code)));
  
  	/*
  	 * Handle reschedule and other end-of-syscall issues
  	 */
  	userret(td, td->td_frame);
  
  	CTR4(KTR_SYSC, "syscall %s exit thread %p pid %d proc %s",
  	    syscallname(p, sa->code), td, td->td_proc->p_pid, td->td_name);
  
  #ifdef KTRACE
  	if (KTRPOINT(td, KTR_SYSRET)) {
  		ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
  		    error : td->td_errno, td->td_retval[0]);
  	}
  #endif
  	td->td_pflags &= ~TDP_NERRNO;
  
  	if (p->p_flag & P_TRACED) {
  		traced = 1;
  		PROC_LOCK(p);
  		td->td_dbgflags |= TDB_SCX;
  		PROC_UNLOCK(p);
  	} else
  		traced = 0;
  	/*
  	 * This works because errno is findable through the
  	 * register set.  If we ever support an emulation where this
  	 * is not the case, this code will need to be revisited.
  	 */
  	STOPEVENT(p, S_SCX, sa->code);
  	if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
  		PROC_LOCK(p);
  		/*
  		 * If tracing the execed process, trap to the debugger
  		 * so that breakpoints can be set before the program
  		 * executes.  If debugger requested tracing of syscall
  		 * returns, do it now too.
  		 */
  		if (traced &&
  		    ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
  		    (p->p_stops & S_PT_SCX) != 0))
  			ptracestop(td, SIGTRAP);
  		td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
  		PROC_UNLOCK(p);
  	}
  
  	if (td->td_pflags & TDP_RFPPWAIT) {
  		/*
  		 * Preserve synchronization semantics of vfork.  If
  		 * waiting for child to exec or exit, fork set
  		 * P_PPWAIT on child, and there we sleep on our proc
  		 * (in case of exit).
  		 *
  		 * Do it after the ptracestop() above is finished, to
  		 * not block our debugger until child execs or exits
  		 * to finish vfork wait.
  		 */
  		td->td_pflags &= ~TDP_RFPPWAIT;
  		p2 = td->td_rfppwait_p;
  		PROC_LOCK(p2);
  		while (p2->p_flag & P_PPWAIT)
  			cv_wait(&p2->p_pwait, &p2->p_mtx);
  		PROC_UNLOCK(p2);
  	}
  }
  