/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1990, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Copyright (c) 2002 Networks Associates Technologies, Inc.
 * All rights reserved.
 *
 * Portions of this software were developed for the FreeBSD Project by
 * ThinkSec AS and NAI Labs, the Security Research Division of Network
 * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * 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. 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_stack.h"

#include <sys/param.h>
#include <sys/cons.h>
#include <sys/kdb.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/stack.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/tty.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>

/*
 * Returns 1 if p2 is "better" than p1
 *
 * The algorithm for picking the "interesting" process is thus:
 *
 *      1) Only foreground processes are eligible - implied.
 *      2) Runnable processes are favored over anything else.  The runner
 *         with the highest cpu utilization is picked (p_estcpu).  Ties are
 *         broken by picking the highest pid.
 *      3) The sleeper with the shortest sleep time is next.  With ties,
 *         we pick out just "short-term" sleepers (P_SINTR == 0).
 *      4) Further ties are broken by picking the highest pid.
 */

#define TESTAB(a, b)    ((a)<<1 | (b))
#define ONLYA   2
#define ONLYB   1
#define BOTH    3

static int
proc_sum(struct proc *p, fixpt_t *estcpup)
{
        struct thread *td;
        int estcpu;
        int val;

        val = 0;
        estcpu = 0;
        FOREACH_THREAD_IN_PROC(p, td) {
                thread_lock(td);
                if (TD_ON_RUNQ(td) ||
                    TD_IS_RUNNING(td))
                        val = 1;
                estcpu += sched_pctcpu(td);
                thread_unlock(td);
        }
        *estcpup = estcpu;

        return (val);
}

static int
thread_compare(struct thread *td, struct thread *td2)
{
        int runa, runb;
        int slpa, slpb;
        fixpt_t esta, estb;

        if (td == NULL)
                return (1);

        /*
         * Fetch running stats, pctcpu usage, and interruptable flag.
         */
        thread_lock(td);
        runa = TD_IS_RUNNING(td) || TD_ON_RUNQ(td);
        slpa = td->td_flags & TDF_SINTR;
        esta = sched_pctcpu(td);
        thread_unlock(td);
        thread_lock(td2);
        runb = TD_IS_RUNNING(td2) || TD_ON_RUNQ(td2);
        estb = sched_pctcpu(td2);
        slpb = td2->td_flags & TDF_SINTR;
        thread_unlock(td2);
        /*
         * see if at least one of them is runnable
         */
        switch (TESTAB(runa, runb)) {
        case ONLYA:
                return (0);
        case ONLYB:
                return (1);
        case BOTH:
                break;
        }
        /*
         *  favor one with highest recent cpu utilization
         */
        if (estb > esta)
                return (1);
        if (esta > estb)
                return (0);
        /*
         * favor one sleeping in a non-interruptible sleep
         */
        switch (TESTAB(slpa, slpb)) {
        case ONLYA:
                return (0);
        case ONLYB:
                return (1);
        case BOTH:
                break;
        }

        return (td < td2);
}

static int
proc_compare(struct proc *p1, struct proc *p2)
{

        int runa, runb;
        fixpt_t esta, estb;

        if (p1 == NULL)
                return (1);

        /*
         * Fetch various stats about these processes.  After we drop the
         * lock the information could be stale but the race is unimportant.
         */
        PROC_LOCK(p1);
        runa = proc_sum(p1, &esta);
        PROC_UNLOCK(p1);
        PROC_LOCK(p2);
        runb = proc_sum(p2, &estb);
        PROC_UNLOCK(p2);

        /*
         * see if at least one of them is runnable
         */
        switch (TESTAB(runa, runb)) {
        case ONLYA:
                return (0);
        case ONLYB:
                return (1);
        case BOTH:
                break;
        }
        /*
         *  favor one with highest recent cpu utilization
         */
        if (estb > esta)
                return (1);
        if (esta > estb)
                return (0);
        /*
         * weed out zombies
         */
        switch (TESTAB(p1->p_state == PRS_ZOMBIE, p2->p_state == PRS_ZOMBIE)) {
        case ONLYA:
                return (1);
        case ONLYB:
                return (0);
        case BOTH:
                break;
        }

        return (p2->p_pid > p1->p_pid);         /* tie - return highest pid */
}

static int
sbuf_tty_drain(void *a, const char *d, int len)
{
        struct tty *tp;
        int rc;

        tp = a;

        if (kdb_active) {
                cnputsn(d, len);
                return (len);
        }
        if (tp != NULL && !KERNEL_PANICKED()) {
                rc = tty_putstrn(tp, d, len);
                if (rc != 0)
                        return (-ENXIO);
                return (len);
        }
        return (-ENXIO);
}

#ifdef STACK
#ifdef INVARIANTS
static int tty_info_kstacks = STACK_SBUF_FMT_COMPACT;
#else
static int tty_info_kstacks = STACK_SBUF_FMT_NONE;
#endif

static int
sysctl_tty_info_kstacks(SYSCTL_HANDLER_ARGS)
{
        enum stack_sbuf_fmt val;
        int error;

        val = tty_info_kstacks;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);

        switch (val) {
        case STACK_SBUF_FMT_NONE:
        case STACK_SBUF_FMT_LONG:
        case STACK_SBUF_FMT_COMPACT:
                tty_info_kstacks = val;
                break;
        default:
                error = EINVAL;
        }

        return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, tty_info_kstacks,
    CTLFLAG_RWTUN | CTLFLAG_MPSAFE | CTLTYPE_INT, NULL, 0,
    sysctl_tty_info_kstacks, "I",
    "Adjust format of kernel stack(9) traces on ^T (tty info): "
    "0 - disabled; 1 - long; 2 - compact");
#endif

/*
 * Report on state of foreground process group.
 */
void
tty_info(struct tty *tp)
{
        struct timeval rtime, utime, stime;
#ifdef STACK
        struct stack stack;
        int sterr, kstacks_val;
        bool print_kstacks;
#endif
        struct proc *p, *ppick;
        struct thread *td, *tdpick;
        const char *stateprefix, *state;
        struct sbuf sb;
        long rss;
        int load, pctcpu;
        pid_t pid;
        char comm[MAXCOMLEN + 1];
        struct rusage ru;

        tty_assert_locked(tp);

        if (tty_checkoutq(tp) == 0)
                return;

        (void)sbuf_new(&sb, tp->t_prbuf, tp->t_prbufsz, SBUF_FIXEDLEN);
        sbuf_set_drain(&sb, sbuf_tty_drain, tp);

        /* Print load average. */
        load = ((int64_t)averunnable.ldavg[0] * 100 + FSCALE / 2) >> FSHIFT;
        sbuf_printf(&sb, "%sload: %d.%02d ", tp->t_column == 0 ? "" : "\n",
            load / 100, load % 100);

        if (tp->t_session == NULL) {
                sbuf_cat(&sb, "not a controlling terminal\n");
                goto out;
        }
        if (tp->t_pgrp == NULL) {
                sbuf_cat(&sb, "no foreground process group\n");
                goto out;
        }
        PGRP_LOCK(tp->t_pgrp);
        if (LIST_EMPTY(&tp->t_pgrp->pg_members)) {
                PGRP_UNLOCK(tp->t_pgrp);
                sbuf_cat(&sb, "empty foreground process group\n");
                goto out;
        }

        /*
         * Pick the most interesting process and copy some of its
         * state for printing later.  This operation could rely on stale
         * data as we can't hold the proc slock or thread locks over the
         * whole list. However, we're guaranteed not to reference an exited
         * thread or proc since we hold the tty locked.
         */
        p = NULL;
        LIST_FOREACH(ppick, &tp->t_pgrp->pg_members, p_pglist)
                if (proc_compare(p, ppick))
                        p = ppick;

        PROC_LOCK(p);
        PGRP_UNLOCK(tp->t_pgrp);
        td = NULL;
        FOREACH_THREAD_IN_PROC(p, tdpick)
                if (thread_compare(td, tdpick))
                        td = tdpick;
        stateprefix = "";
        thread_lock(td);
        if (TD_IS_RUNNING(td))
                state = "running";
        else if (TD_ON_RUNQ(td) || TD_CAN_RUN(td))
                state = "runnable";
        else if (TD_IS_SLEEPING(td)) {
                /* XXX: If we're sleeping, are we ever not in a queue? */
                if (TD_ON_SLEEPQ(td))
                        state = td->td_wmesg;
                else
                        state = "sleeping without queue";
        } else if (TD_ON_LOCK(td)) {
                state = td->td_lockname;
                stateprefix = "*";
        } else if (TD_IS_SUSPENDED(td))
                state = "suspended";
        else if (TD_AWAITING_INTR(td))
                state = "intrwait";
        else if (p->p_state == PRS_ZOMBIE)
                state = "zombie";
        else
                state = "unknown";
        pctcpu = (sched_pctcpu(td) * 10000 + FSCALE / 2) >> FSHIFT;
#ifdef STACK
        kstacks_val = atomic_load_int(&tty_info_kstacks);
        print_kstacks = (kstacks_val != STACK_SBUF_FMT_NONE);

        if (print_kstacks)
                sterr = stack_save_td(&stack, td);
#endif
        thread_unlock(td);
        if (p->p_state == PRS_NEW || p->p_state == PRS_ZOMBIE)
                rss = 0;
        else
                rss = pgtok(vmspace_resident_count(p->p_vmspace));
        microuptime(&rtime);
        timevalsub(&rtime, &p->p_stats->p_start);
        rufetchcalc(p, &ru, &utime, &stime);
        pid = p->p_pid;
        strlcpy(comm, p->p_comm, sizeof comm);
        PROC_UNLOCK(p);

        /* Print command, pid, state, rtime, utime, stime, %cpu, and rss. */
        sbuf_printf(&sb,
            " cmd: %s %d [%s%s] %ld.%02ldr %ld.%02ldu %ld.%02lds %d%% %ldk\n",
            comm, pid, stateprefix, state,
            (long)rtime.tv_sec, rtime.tv_usec / 10000,
            (long)utime.tv_sec, utime.tv_usec / 10000,
            (long)stime.tv_sec, stime.tv_usec / 10000,
            pctcpu / 100, rss);

#ifdef STACK
        if (print_kstacks && sterr == 0)
                stack_sbuf_print_flags(&sb, &stack, M_NOWAIT, kstacks_val);
#endif

out:
        sbuf_finish(&sb);
        sbuf_delete(&sb);
}