subr_trap.c

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/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (C) 1994, David Greenman
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2007 The FreeBSD Foundation
 *
 * This code is derived from software contributed to Berkeley by
 * the University of Utah, and William Jolitz.
 *
 * Portions of this software were developed by A. Joseph Koshy under
 * sponsorship from the FreeBSD Foundation and Google, Inc.
 *
 * 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("$FreeBSD$");
 
#include "opt_hwpmc_hooks.h"
#include "opt_ktrace.h"
#include "opt_sched.h"
 
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/capsicum.h>
#include <sys/event.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/pmckern.h>
#include <sys/proc.h>
#include <sys/ktr.h>
#include <sys/ptrace.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/systm.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#include <security/audit/audit.h>
 
#include <machine/cpu.h>
 
#ifdef VIMAGE
#include <net/vnet.h>
#endif
 
#ifdef  HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
 
#include <security/mac/mac_framework.h>
 
void (*softdep_ast_cleanup)(struct thread *);
 
/*
 * Define the code needed before returning to user mode, for trap and
 * syscall.
 */
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,
            td->td_name);
        KASSERT((p->p_flag & P_WEXIT) == 0,
            ("Exiting process returns to usermode"));
#ifdef DIAGNOSTIC
        /*
         * Check that we called signotify() enough.  For
         * multi-threaded processes, where signal distribution might
         * change due to other threads changing sigmask, the check is
         * racy and cannot be performed reliably.
         * If current process is vfork child, indicated by P_PPWAIT, then
         * issignal() ignores stops, so we block the check to avoid
         * classifying pending signals.
         */
        if (p->p_numthreads == 1) {
                PROC_LOCK(p);
                thread_lock(td);
                if ((p->p_flag & P_PPWAIT) == 0 &&
                    (td->td_pflags & TDP_SIGFASTBLOCK) == 0) {
                        if (SIGPENDING(td) && (td->td_flags &
                            (TDF_NEEDSIGCHK | TDF_ASTPENDING)) !=
                            (TDF_NEEDSIGCHK | TDF_ASTPENDING)) {
                                thread_unlock(td);
                                panic(
        "failed to set signal flags for ast p %p td %p fl %x",
                                    p, td, td->td_flags);
                        }
                }
                thread_unlock(td);
                PROC_UNLOCK(p);
        }
#endif
 
        /*
         * Charge system time if profiling.
         */
        if (__predict_false(p->p_flag & P_PROFIL))
                addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
 
#ifdef HWPMC_HOOKS
        if (PMC_THREAD_HAS_SAMPLES(td))
                PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL);
#endif
#ifdef TCPHPTS
        /*
         * @gallatin is adament that this needs to go here, I
         * am not so sure. Running hpts is a lot like
         * a lro_flush() that happens while a user process
         * is running. But he may know best so I will go
         * with his view of accounting. :-)
         */
        tcp_run_hpts();
#endif
        /*
         * Let the scheduler adjust our priority etc.
         */
        sched_userret(td);
 
        /*
         * Check for misbehavior.
         *
         * In case there is a callchain tracing ongoing because of
         * hwpmc(4), skip the scheduler pinning check.
         * hwpmc(4) subsystem, infact, will collect callchain informations
         * at ast() checkpoint, which is past userret().
         */
        WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
        KASSERT(td->td_critnest == 0,
            ("userret: Returning in a critical section"));
        KASSERT(td->td_locks == 0,
            ("userret: Returning with %d locks held", td->td_locks));
        KASSERT(td->td_rw_rlocks == 0,
            ("userret: Returning with %d rwlocks held in read mode",
            td->td_rw_rlocks));
        KASSERT(td->td_sx_slocks == 0,
            ("userret: Returning with %d sx locks held in shared mode",
            td->td_sx_slocks));
        KASSERT(td->td_lk_slocks == 0,
            ("userret: Returning with %d lockmanager locks held in shared mode",
            td->td_lk_slocks));
        KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
            ("userret: Returning with pagefaults disabled"));
        if (__predict_false(!THREAD_CAN_SLEEP())) {
#ifdef EPOCH_TRACE
                epoch_trace_list(curthread);
#endif
                KASSERT(0, ("userret: Returning with sleep disabled"));
        }
        KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
            ("userret: Returning with with pinned thread"));
        KASSERT(td->td_vp_reserved == NULL,
            ("userret: Returning with preallocated vnode"));
        KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
            ("userret: Returning with stop signals deferred"));
        KASSERT(td->td_vslock_sz == 0,
            ("userret: Returning with vslock-wired space"));
#ifdef VIMAGE
        /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
        VNET_ASSERT(curvnet == NULL,
            ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
            __func__, td, p->p_pid, td->td_name, curvnet,
            (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
#endif
}
 
/*
 * 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;
        int flags, sig;
        bool resched_sigs;
 
        kmsan_mark(framep, sizeof(*framep), KMSAN_STATE_INITED);
 
        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);
        THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
        td->td_frame = framep;
        td->td_pticks = 0;
 
        /*
         * This updates the td_flag'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 flags, the astpending flag will be set and
         * ast() will be called again.
         */
        thread_lock(td);
        flags = td->td_flags;
        td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
            TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND |
            TDF_KQTICKLED);
        thread_unlock(td);
        VM_CNT_INC(v_trap);
 
        if (td->td_cowgen != atomic_load_int(&p->p_cowgen))
                thread_cow_update(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;
        }
#ifdef HWPMC_HOOKS
        /* Handle Software PMC callchain capture. */
        if (PMC_IS_PENDING_CALLCHAIN(td))
                PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
#endif
        if ((td->td_pflags & TDP_RFPPWAIT) != 0)
                fork_rfppwait(td);
        if (flags & TDF_ALRMPEND) {
                PROC_LOCK(p);
                kern_psignal(p, SIGVTALRM);
                PROC_UNLOCK(p);
        }
        if (flags & TDF_PROFPEND) {
                PROC_LOCK(p);
                kern_psignal(p, SIGPROF);
                PROC_UNLOCK(p);
        }
#ifdef MAC
        if (flags & TDF_MACPEND)
                mac_thread_userret(td);
#endif
        if (flags & TDF_NEEDRESCHED) {
#ifdef KTRACE
                if (KTRPOINT(td, KTR_CSW))
                        ktrcsw(1, 1, __func__);
#endif
                thread_lock(td);
                sched_prio(td, td->td_user_pri);
                mi_switch(SW_INVOL | SWT_NEEDRESCHED);
#ifdef KTRACE
                if (KTRPOINT(td, KTR_CSW))
                        ktrcsw(0, 1, __func__);
#endif
        }
 
        td_softdep_cleanup(td);
        MPASS(td->td_su == NULL);
 
        /*
         * If this thread tickled GEOM, we need to wait for the giggling to
         * stop before we return to userland
         */
        if (__predict_false(td->td_pflags & TDP_GEOM))
                g_waitidle();
 
#ifdef DIAGNOSTIC
        if (p->p_numthreads == 1 && (flags & TDF_NEEDSIGCHK) == 0) {
                PROC_LOCK(p);
                thread_lock(td);
                /*
                 * Note that TDF_NEEDSIGCHK should be re-read from
                 * td_flags, since signal might have been delivered
                 * after we cleared td_flags above.  This is one of
                 * the reason for looping check for AST condition.
                 * See comment in userret() about P_PPWAIT.
                 */
                if ((p->p_flag & P_PPWAIT) == 0 &&
                    (td->td_pflags & TDP_SIGFASTBLOCK) == 0) {
                        if (SIGPENDING(td) && (td->td_flags &
                            (TDF_NEEDSIGCHK | TDF_ASTPENDING)) !=
                            (TDF_NEEDSIGCHK | TDF_ASTPENDING)) {
                                thread_unlock(td); /* fix dumps */
                                panic(
        "failed2 to set signal flags for ast p %p td %p fl %x %x",
                                    p, td, flags, td->td_flags);
                        }
                }
                thread_unlock(td);
                PROC_UNLOCK(p);
        }
#endif
 
        /*
         * Check for signals. Unlocked reads of p_pendingcnt or
         * p_siglist might cause process-directed signal to be handled
         * later.
         */
        if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
            !SIGISEMPTY(p->p_siglist)) {
                sigfastblock_fetch(td);
                PROC_LOCK(p);
                mtx_lock(&p->p_sigacts->ps_mtx);
                while ((sig = cursig(td)) != 0) {
                        KASSERT(sig >= 0, ("sig %d", sig));
                        postsig(sig);
                }
                mtx_unlock(&p->p_sigacts->ps_mtx);
                PROC_UNLOCK(p);
                resched_sigs = true;
        } else {
                resched_sigs = false;
        }
 
        if ((flags & TDF_KQTICKLED) != 0)
                kqueue_drain_schedtask();
 
        /*
         * Handle deferred update of the fast sigblock value, after
         * the postsig() loop was performed.
         */
        sigfastblock_setpend(td, resched_sigs);
 
#ifdef KTRACE
        KTRUSERRET(td);
#endif
 
        /*
         * We need to check to see if we have to exit or wait due to a
         * single threading requirement or some other STOP condition.
         */
        if (flags & TDF_NEEDSUSPCHK) {
                PROC_LOCK(p);
                thread_suspend_check(0);
                PROC_UNLOCK(p);
        }
 
        if (td->td_pflags & TDP_OLDMASK) {
                td->td_pflags &= ~TDP_OLDMASK;
                kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
        }
 
#ifdef RACCT
        if (__predict_false(racct_enable && p->p_throttled != 0))
                racct_proc_throttled(p);
#endif
 
        userret(td, framep);
}
 
const char *
syscallname(struct proc *p, u_int code)
{
        static const char unknown[] = "unknown";
        struct sysentvec *sv;
 
        sv = p->p_sysent;
        if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
                return (unknown);
        return (sv->sv_syscallnames[code]);
}