freebsd-dev/sys/kern/subr_trap.c
John Baldwin 8e2e767b1f Add a per-thread ucred reference for syscalls and synchronous traps from
userland.  The per thread ucred reference is immutable and thus needs no
locks to be read.  However, until all the proc locking associated with
writes to p_ucred are completed, it is still not safe to use the per-thread
reference.

Tested on:	x86 (SMP), alpha, sparc64
2001-10-26 08:12:54 +00:00

208 lines
6.0 KiB
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
* $FreeBSD$
*/
#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/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/systm.h>
#include <sys/vmmeter.h>
#include <machine/cpu.h>
#include <machine/pcb.h>
/*
* Define the code needed before returning to user mode, for
* trap and syscall.
*
* MPSAFE
*/
void
userret(td, frame, oticks)
struct thread *td;
struct trapframe *frame;
u_int oticks;
{
struct proc *p = td->td_proc;
struct kse *ke = td->td_kse;
struct ksegrp *kg = td->td_ksegrp;
int sig;
mtx_lock(&Giant);
PROC_LOCK(p);
while ((sig = CURSIG(p)) != 0)
postsig(sig);
PROC_UNLOCK(p);
mtx_unlock(&Giant);
mtx_lock_spin(&sched_lock);
kg->kg_pri.pri_level = kg->kg_pri.pri_user;
if (ke->ke_flags & KEF_NEEDRESCHED) {
/*
* Since we are curproc, a clock interrupt could
* change our priority without changing run queues
* (the running process is not kept on a run queue).
* If this happened after we setrunqueue ourselves but
* before we switch()'ed, we might not be on the queue
* indicated by our priority.
*/
DROP_GIANT_NOSWITCH();
setrunqueue(td);
p->p_stats->p_ru.ru_nivcsw++;
mi_switch();
mtx_unlock_spin(&sched_lock);
PICKUP_GIANT();
mtx_lock(&Giant);
PROC_LOCK(p);
while ((sig = CURSIG(p)) != 0)
postsig(sig);
mtx_unlock(&Giant);
PROC_UNLOCK(p);
} else
mtx_unlock_spin(&sched_lock);
/*
* Charge system time if profiling.
*/
if (p->p_sflag & PS_PROFIL) {
addupc_task(ke, TRAPF_PC(frame),
(u_int)(ke->ke_sticks - oticks) * psratio);
}
}
/*
* Process an asynchronous software trap.
* This is relatively easy.
* This function will return with preemption disabled.
*/
void
ast(framep)
struct trapframe *framep;
{
struct thread *td = curthread;
struct proc *p = td->td_proc;
struct kse *ke = td->td_kse;
u_int prticks, sticks;
critical_t s;
int sflag;
int flags;
#if defined(DEV_NPX) && !defined(SMP)
int ucode;
#endif
KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
KASSERT(td->td_ucred == NULL, ("leaked ucred"));
#ifdef WITNESS
if (witness_list(td))
panic("Returning to user mode with mutex(s) held");
#endif
mtx_assert(&Giant, MA_NOTOWNED);
s = critical_enter();
while ((ke->ke_flags & (KEF_ASTPENDING | KEF_NEEDRESCHED)) != 0) {
critical_exit(s);
td->td_frame = framep;
/*
* 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
* we will loop again.
*/
mtx_lock_spin(&sched_lock);
sticks = ke->ke_sticks;
sflag = p->p_sflag;
flags = ke->ke_flags;
p->p_sflag &= ~(PS_PROFPEND | PS_ALRMPEND);
ke->ke_flags &= ~(KEF_OWEUPC | KEF_ASTPENDING);
cnt.v_soft++;
if (flags & KEF_OWEUPC) {
prticks = p->p_stats->p_prof.pr_ticks;
p->p_stats->p_prof.pr_ticks = 0;
}
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
td->td_ucred = crhold(p->p_ucred);
PROC_UNLOCK(p);
if (flags & KEF_OWEUPC)
addupc_task(ke, p->p_stats->p_prof.pr_addr, prticks);
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_char(&PCPU_GET(curpcb)->pcb_flags,
PCB_NPXTRAP);
ucode = npxtrap();
if (ucode != -1) {
trapsignal(p, SIGFPE, ucode);
}
}
#endif
if (sflag & PS_PROFPEND) {
PROC_LOCK(p);
psignal(p, SIGPROF);
PROC_UNLOCK(p);
}
userret(td, framep, sticks);
mtx_lock(&Giant);
crfree(td->td_ucred);
mtx_unlock(&Giant);
td->td_ucred = NULL;
s = critical_enter();
}
mtx_assert(&Giant, MA_NOTOWNED);
/*
* We need to keep interrupts disabled so that if any further AST's
* come in, the interrupt they come in on will be delayed until we
* finish returning to userland. We assume that the return to userland
* will perform the equivalent of critical_exit().
*/
}