sys/kern/subr_syscall.c

/*-
 * Copyright (C) 1994, David Greenman
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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 <sys/cdefs.h>
__FBSDID("$FreeBSD: head/sys/kern/subr_trap.c 164936 2006-12-06 06:34:57Z julian $");

#include "opt_ktrace.h"
#include "opt_mac.h"
#ifdef __i386__
#include "opt_npx.h"
#endif

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/ktr.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/systm.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif

#include <machine/cpu.h>
#include <machine/pcb.h>

#include <security/mac/mac_framework.h>

/*
 * Define the code needed before returning to user mode, for
 * trap and syscall.
 *
 * MPSAFE
 */
void
userret(struct thread *td, struct trapframe *frame)
{
	struct proc *p = td->td_proc;

	CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
            p->p_comm);
#ifdef DIAGNOSTIC
	/* Check that we called signotify() enough. */
	PROC_LOCK(p);
	mtx_lock_spin(&sched_lock);
	if (SIGPENDING(td) && ((td->td_flags & TDF_NEEDSIGCHK) == 0 ||
	    (td->td_flags & TDF_ASTPENDING) == 0))
		printf("failed to set signal flags properly for ast()\n");
	mtx_unlock_spin(&sched_lock);
	PROC_UNLOCK(p);
#endif

#ifdef KTRACE
	KTRUSERRET(td);
#endif

	/*
	 * If this thread tickled GEOM, we need to wait for the giggling to
	 * stop before we return to userland
	 */
	if (td->td_pflags & TDP_GEOM)
		g_waitidle();

	/*
	 * We need to check to see if we have to exit or wait due to a
	 * single threading requirement or some other STOP condition.
	 * Don't bother doing all the work if the stop bits are not set
	 * at this time.. If we miss it, we miss it.. no big deal.
	 */
	if (P_SHOULDSTOP(p)) {
		PROC_LOCK(p);
		thread_suspend_check(0);	/* Can suspend or kill */
		PROC_UNLOCK(p);
	}

#ifdef KSE
	/*
	 * Do special thread processing, e.g. upcall tweaking and such.
	 */
	if (p->p_flag & P_SA)
		thread_userret(td, frame);
#endif

	/*
	 * Charge system time if profiling.
	 */
	if (p->p_flag & P_PROFIL) {

		addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
	}

	/*
	 * Let the scheduler adjust our priority etc.
	 */
	sched_userret(td);
	KASSERT(td->td_locks == 0,
	    ("userret: Returning with %d locks held.", td->td_locks));
}

/*
 * Process an asynchronous software trap.
 * This is relatively easy.
 * This function will return with preemption disabled.
 */
void
ast(struct trapframe *framep)
{
	struct thread *td;
	struct proc *p;
	struct rlimit rlim;
	int sflag;
	int flags;
	int sig;
#if defined(DEV_NPX) && !defined(SMP)
	int ucode;
	ksiginfo_t ksi;
#endif

	td = curthread;
	p = td->td_proc;

	CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
            p->p_comm);
	KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
	WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
	mtx_assert(&Giant, MA_NOTOWNED);
	mtx_assert(&sched_lock, MA_NOTOWNED);
	td->td_frame = framep;
	td->td_pticks = 0;

#ifdef KSE
	if ((p->p_flag & P_SA) && (td->td_mailbox == NULL))
		thread_user_enter(td);
#endif

	/*
	 * This updates the p_sflag's for the checks below in one
	 * "atomic" operation with turning off the astpending flag.
	 * If another AST is triggered while we are handling the
	 * AST's saved in sflag, the astpending flag will be set and
	 * ast() will be called again.
	 */
	mtx_lock_spin(&sched_lock);
	flags = td->td_flags;
	sflag = p->p_sflag;
	if (p->p_sflag & (PS_ALRMPEND | PS_PROFPEND | PS_XCPU))
		p->p_sflag &= ~(PS_ALRMPEND | PS_PROFPEND | PS_XCPU);
#ifdef MAC
	if (p->p_sflag & PS_MACPEND)
		p->p_sflag &= ~PS_MACPEND;
#endif
	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK |
	    TDF_NEEDRESCHED | TDF_INTERRUPT);
	cnt.v_trap++;
	mtx_unlock_spin(&sched_lock);

	/*
	 * XXXKSE While the fact that we owe a user profiling
	 * tick is stored per thread in this code, the statistics
	 * themselves are still stored per process.
	 * This should probably change, by which I mean that
	 * possibly the location of both might change.
	 */
	if (td->td_ucred != p->p_ucred)
		cred_update_thread(td);
	if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
		addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
		td->td_profil_ticks = 0;
		td->td_pflags &= ~TDP_OWEUPC;
	}
	if (sflag & PS_ALRMPEND) {
		PROC_LOCK(p);
		psignal(p, SIGVTALRM);
		PROC_UNLOCK(p);
	}
#if defined(DEV_NPX) && !defined(SMP)
	if (PCPU_GET(curpcb)->pcb_flags & PCB_NPXTRAP) {
		atomic_clear_int(&PCPU_GET(curpcb)->pcb_flags,
		    PCB_NPXTRAP);
		ucode = npxtrap();
		if (ucode != -1) {
			ksiginfo_init_trap(&ksi);
			ksi.ksi_signo = SIGFPE;
			ksi.ksi_code = ucode;
			trapsignal(td, &ksi);
		}
	}
#endif
	if (sflag & PS_PROFPEND) {
		PROC_LOCK(p);
		psignal(p, SIGPROF);
		PROC_UNLOCK(p);
	}
	if (sflag & PS_XCPU) {
		PROC_LOCK(p);
		lim_rlimit(p, RLIMIT_CPU, &rlim);
		mtx_lock_spin(&sched_lock);
		if (p->p_rux.rux_runtime >= rlim.rlim_max * cpu_tickrate()) {
			mtx_unlock_spin(&sched_lock);
			killproc(p, "exceeded maximum CPU limit");
		} else {
			if (p->p_cpulimit < rlim.rlim_max)
				p->p_cpulimit += 5;
			mtx_unlock_spin(&sched_lock);
			psignal(p, SIGXCPU);
		}
		PROC_UNLOCK(p);
	}
#ifdef MAC
	if (sflag & PS_MACPEND)
		mac_thread_userret(td);
#endif
	if (flags & TDF_NEEDRESCHED) {
#ifdef KTRACE
		if (KTRPOINT(td, KTR_CSW))
			ktrcsw(1, 1);
#endif
		mtx_lock_spin(&sched_lock);
		sched_prio(td, td->td_user_pri);
		mi_switch(SW_INVOL, NULL);
		mtx_unlock_spin(&sched_lock);
#ifdef KTRACE
		if (KTRPOINT(td, KTR_CSW))
			ktrcsw(0, 1);
#endif
	}
	if (flags & TDF_NEEDSIGCHK) {
		PROC_LOCK(p);
		mtx_lock(&p->p_sigacts->ps_mtx);
		while ((sig = cursig(td)) != 0)
			postsig(sig);
		mtx_unlock(&p->p_sigacts->ps_mtx);
		PROC_UNLOCK(p);
	}

	userret(td, framep);
	mtx_assert(&Giant, MA_NOTOWNED);
}