FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_trap.c

     /*-
      * 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, 2022 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 <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/msan.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/ktr.h>
    #include <sys/resourcevar.h>
    #include <sys/sched.h>
    #include <sys/syscall.h>
    #include <sys/syscallsubr.h>
    #include <sys/sysent.h>
    #include <sys/systm.h>
    #include <sys/vmmeter.h>
    
    #include <machine/cpu.h>
    
    #ifdef VIMAGE
    #include <net/vnet.h>
    #endif
    
    #ifdef  HWPMC_HOOKS
    #include <sys/pmckern.h>
    #endif
    
    #ifdef EPOCH_TRACE
    #include <sys/epoch.h>
    #endif
    
    /*
     * 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 &&
                       SIGPENDING(td) && !td_ast_pending(td, TDA_AST) &&
                       !td_ast_pending(td, TDA_SIG)) {
                           thread_unlock(td);
                           panic(
                               "failed to set signal flags for ast p %p "
                               "td %p td_ast %#x fl %#x",
                               p, td, td->td_ast, 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
   }
   
   static void
   ast_prep(struct thread *td, int tda __unused)
   {
           VM_CNT_INC(v_trap);
           td->td_pticks = 0;
           if (td->td_cowgen != atomic_load_int(&td->td_proc->p_cowgen))
                   thread_cow_update(td);
   
   }
   
   struct ast_entry {
           int     ae_flags;
           int     ae_tdp;
           void    (*ae_f)(struct thread *td, int ast);
   };
   
   _Static_assert(TDAI(TDA_MAX) <= UINT_MAX, "Too many ASTs");
   
   static struct ast_entry ast_entries[TDA_MAX] __read_mostly = {
           [TDA_AST] = { .ae_f = ast_prep, .ae_flags = ASTR_UNCOND},
   };
   
   void
   ast_register(int ast, int flags, int tdp,
       void (*f)(struct thread *, int asts))
   {
           struct ast_entry *ae;
   
           MPASS(ast < TDA_MAX);
           MPASS((flags & ASTR_TDP) == 0 || ((flags & ASTR_ASTF_REQUIRED) != 0
               && __bitcount(tdp) == 1));
           ae = &ast_entries[ast];
           MPASS(ae->ae_f == NULL);
           ae->ae_flags = flags;
           ae->ae_tdp = tdp;
           atomic_interrupt_fence();
           ae->ae_f = f;
   }
   
   /*
    * XXXKIB Note that the deregistration of an AST handler does not
    * drain threads possibly executing it, which affects unloadable
    * modules.  The issue is either handled by the subsystem using
    * handlers, or simply ignored.  Fixing the problem is considered not
    * worth the overhead.
    */
   void
   ast_deregister(int ast)
   {
           struct ast_entry *ae;
   
           MPASS(ast < TDA_MAX);
           ae = &ast_entries[ast];
           MPASS(ae->ae_f != NULL);
           ae->ae_f = NULL;
           atomic_interrupt_fence();
           ae->ae_flags = 0;
           ae->ae_tdp = 0;
   }
   
   void
   ast_sched_locked(struct thread *td, int tda)
   {
           THREAD_LOCK_ASSERT(td, MA_OWNED);
           MPASS(tda < TDA_MAX);
   
           td->td_ast |= TDAI(tda);
   }
   
   void
   ast_unsched_locked(struct thread *td, int tda)
   {
           THREAD_LOCK_ASSERT(td, MA_OWNED);
           MPASS(tda < TDA_MAX);
   
           td->td_ast &= ~TDAI(tda);
   }
   
   void
   ast_sched(struct thread *td, int tda)
   {
           thread_lock(td);
           ast_sched_locked(td, tda);
           thread_unlock(td);
   }
   
   void
   ast_sched_mask(struct thread *td, int ast)
   {
           thread_lock(td);
           td->td_ast |= ast;
           thread_unlock(td);
   }
   
   static bool
   ast_handler_calc_tdp_run(struct thread *td, const struct ast_entry *ae)
   {
           return ((ae->ae_flags & ASTR_TDP) == 0 ||
               (td->td_pflags & ae->ae_tdp) != 0);
   }
   
   /*
    * Process an asynchronous software trap.
    */
   static void
   ast_handler(struct thread *td, struct trapframe *framep, bool dtor)
   {
           struct ast_entry *ae;
           void (*f)(struct thread *td, int asts);
           int a, td_ast;
           bool run;
   
           if (framep != NULL) {
                   kmsan_mark(framep, sizeof(*framep), KMSAN_STATE_INITED);
                   td->td_frame = framep;
           }
   
           if (__predict_true(!dtor)) {
                   WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
                   mtx_assert(&Giant, MA_NOTOWNED);
                   THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
   
                   /*
                    * This updates the td_ast for the checks below in one
                    * atomic operation with turning off all scheduled AST's.
                    * If another AST is triggered while we are handling the
                    * AST's saved in td_ast, the td_ast is again non-zero and
                    * ast() will be called again.
                    */
                   thread_lock(td);
                   td_ast = td->td_ast;
                   td->td_ast = 0;
                   thread_unlock(td);
           } else {
                   /*
                    * The td thread's td_lock is not guaranteed to exist,
                    * the thread might be not initialized enough when it's
                    * destructor is called.  It is safe to read and
                    * update td_ast without locking since the thread is
                    * not runnable or visible to other threads.
                    */
                   td_ast = td->td_ast;
                   td->td_ast = 0;
           }
   
           CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, td->td_proc->p_pid,
               td->td_proc->p_comm);
           KASSERT(framep == NULL || TRAPF_USERMODE(framep),
               ("ast in kernel mode"));
   
           for (a = 0; a < nitems(ast_entries); a++) {
                   ae = &ast_entries[a];
                   f = ae->ae_f;
                   if (f == NULL)
                           continue;
                   atomic_interrupt_fence();
   
                   run = false;
                   if (__predict_false(framep == NULL)) {
                           if ((ae->ae_flags & ASTR_KCLEAR) != 0)
                                   run = ast_handler_calc_tdp_run(td, ae);
                   } else {
                           if ((ae->ae_flags & ASTR_UNCOND) != 0)
                                   run = true;
                           else if ((ae->ae_flags & ASTR_ASTF_REQUIRED) != 0 &&
                               (td_ast & TDAI(a)) != 0)
                                   run = ast_handler_calc_tdp_run(td, ae);
                   }
                   if (run)
                           f(td, td_ast);
           }
   }
   
   void
   ast(struct trapframe *framep)
   {
           struct thread *td;
   
           td = curthread;
           ast_handler(td, framep, false);
           userret(td, framep);
   }
   
   void
   ast_kclear(struct thread *td)
   {
           ast_handler(td, NULL, td != curthread);
   }
   
   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]);
   }

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