/*-
 * 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.
 */

#include <sys/cdefs.h>
#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
        /*
         * 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 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 == NULL ? -1 : td->td_proc->p_pid,
             td->td_proc == NULL ? "" : 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]);
}