kill tsol ("Trusted Solaris") aka TX ("Trusted Extensions")

[unleashed.git] / kernel / os / fork.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2013, Joyent, Inc. All rights reserved.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/signal.h>
#include <sys/cred.h>
#include <sys/policy.h>
#include <sys/user.h>
#include <sys/systm.h>
#include <sys/cpuvar.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/cmn_err.h>
#include <sys/acct.h>
#include <sys/tuneable.h>
#include <sys/class.h>
#include <sys/kmem.h>
#include <sys/session.h>
#include <sys/ucontext.h>
#include <sys/stack.h>
#include <sys/procfs.h>
#include <sys/prsystm.h>
#include <sys/vmsystm.h>
#include <sys/vtrace.h>
#include <sys/debug.h>
#include <sys/shm_impl.h>
#include <sys/door_data.h>
#include <vm/as.h>
#include <vm/rm.h>
#include <c2/audit.h>
#include <sys/var.h>
#include <sys/schedctl.h>
#include <sys/utrap.h>
#include <sys/task.h>
#include <sys/resource.h>
#include <sys/cyclic.h>
#include <sys/lgrp.h>
#include <sys/rctl.h>
#include <sys/contract_impl.h>
#include <sys/contract/process_impl.h>
#include <sys/list.h>
#include <sys/dtrace.h>
#include <sys/pool.h>
#include <sys/zone.h>
#include <sys/sdt.h>
#include <sys/class.h>
#include <sys/corectl.h>
#include <sys/brand.h>
#include <sys/fork.h>

static int64_t cfork(int, int, int);
static int getproc(proc_t **, pid_t, uint_t);
#define GETPROC_USER    0x0
#define GETPROC_KERNEL  0x1

static void fork_fail(proc_t *);
static void forklwp_fail(proc_t *);

int fork_fail_pending;

extern struct kmem_cache *process_cache;

/*
 * The vfork() system call trap is no longer invoked by libc.
 * It is retained only for the benefit of applications running
 * within a solaris10 branded zone.  It should be eliminated
 * when we no longer support solaris10 branded zones.
 */
int64_t
vfork(void)
{
        curthread->t_post_sys = 1;      /* so vfwait() will be called */
        return (cfork(1, 1, 0));
}

/*
 * forksys system call - forkx, forkallx, vforkx.  This is the
 * interface invoked by libc for fork1(), forkall(), and vfork()
 */
int64_t
forksys(int subcode, int flags)
{
        switch (subcode) {
        case 0:
                return (cfork(0, 1, flags));    /* forkx(flags) */
        case 1:
                return (cfork(0, 0, flags));    /* forkallx(flags) */
        case 2:
                curthread->t_post_sys = 1;      /* so vfwait() will be called */
                return (cfork(1, 1, flags));    /* vforkx(flags) */
        default:
                return ((int64_t)set_errno(EINVAL));
        }
}

/*
 * Remove the associations of a child process from its parent and siblings.
 */
static void
disown_proc(proc_t *pp, proc_t *cp)
{
        proc_t **orphpp;

        ASSERT(MUTEX_HELD(&pidlock));

        orphpp = &pp->p_orphan;
        while (*orphpp != cp)
                orphpp = &(*orphpp)->p_nextorph;
        *orphpp = cp->p_nextorph;

        if (pp->p_child == cp)
                pp->p_child = cp->p_sibling;
        if (cp->p_sibling)
                cp->p_sibling->p_psibling = cp->p_psibling;
        if (cp->p_psibling)
                cp->p_psibling->p_sibling = cp->p_sibling;
}

/* ARGSUSED */
static int64_t
cfork(int isvfork, int isfork1, int flags)
{
        proc_t *p = ttoproc(curthread);
        struct as *as;
        proc_t *cp;
        klwp_t *clone;
        kthread_t *t;
        task_t *tk;
        rval_t  r;
        int error;
        int i;
        rctl_set_t *dup_set;
        rctl_alloc_gp_t *dup_gp;
        rctl_entity_p_t e;
        lwpdir_t *ldp;
        lwpent_t *lep;
        lwpent_t *clep;

        /*
         * Allow only these two flags.
         */
        if ((flags & ~(FORK_NOSIGCHLD | FORK_WAITPID)) != 0) {
                error = EINVAL;
                atomic_inc_32(&curproc->p_zone->zone_ffmisc);
                goto forkerr;
        }

        /*
         * fork is not supported for the /proc agent lwp.
         */
        if (curthread == p->p_agenttp) {
                error = ENOTSUP;
                atomic_inc_32(&curproc->p_zone->zone_ffmisc);
                goto forkerr;
        }

        if ((error = secpolicy_basic_fork(CRED())) != 0) {
                atomic_inc_32(&p->p_zone->zone_ffmisc);
                goto forkerr;
        }

        /*
         * If the calling lwp is doing a fork1() then the
         * other lwps in this process are not duplicated and
         * don't need to be held where their kernel stacks can be
         * cloned.  If doing forkall(), the process is held with
         * SHOLDFORK, so that the lwps are at a point where their
         * stacks can be copied which is on entry or exit from
         * the kernel.
         */
        if (!holdlwps(isfork1 ? SHOLDFORK1 : SHOLDFORK)) {
                aston(curthread);
                error = EINTR;
                atomic_inc_32(&p->p_zone->zone_ffmisc);
                goto forkerr;
        }

#if defined(__sparc)
        /*
         * Ensure that the user stack is fully constructed
         * before creating the child process structure.
         */
        (void) flush_user_windows_to_stack(NULL);
#endif

        mutex_enter(&p->p_lock);
        /*
         * If this is vfork(), cancel any suspend request we might
         * have gotten from some other thread via lwp_suspend().
         * Otherwise we could end up with a deadlock on return
         * from the vfork() in both the parent and the child.
         */
        if (isvfork)
                curthread->t_proc_flag &= ~TP_HOLDLWP;
        /*
         * Prevent our resource set associations from being changed during fork.
         */
        pool_barrier_enter();
        mutex_exit(&p->p_lock);

        /*
         * Create a child proc struct. Place a VN_HOLD on appropriate vnodes.
         */
        if (getproc(&cp, 0, GETPROC_USER) < 0) {
                mutex_enter(&p->p_lock);
                pool_barrier_exit();
                continuelwps(p);
                mutex_exit(&p->p_lock);
                error = EAGAIN;
                goto forkerr;
        }

        TRACE_2(TR_FAC_PROC, TR_PROC_FORK, "proc_fork:cp %p p %p", cp, p);

        /*
         * Assign an address space to child
         */
        if (isvfork) {
                /*
                 * Clear any watched areas and remember the
                 * watched pages for restoring in vfwait().
                 */
                as = p->p_as;
                if (avl_numnodes(&as->a_wpage) != 0) {
                        AS_LOCK_ENTER(as, RW_WRITER);
                        as_clearwatch(as);
                        p->p_wpage = as->a_wpage;
                        avl_create(&as->a_wpage, wp_compare,
                            sizeof (struct watched_page),
                            offsetof(struct watched_page, wp_link));
                        AS_LOCK_EXIT(as);
                }
                cp->p_as = as;
                cp->p_flag |= SVFORK;

                /*
                 * Use the parent's shm segment list information for
                 * the child as it uses its address space till it execs.
                 */
                cp->p_segacct = p->p_segacct;
        } else {
                /*
                 * We need to hold P_PR_LOCK until the address space has
                 * been duplicated and we've had a chance to remove from the
                 * child any DTrace probes that were in the parent. Holding
                 * P_PR_LOCK prevents any new probes from being added and any
                 * extant probes from being removed.
                 */
                mutex_enter(&p->p_lock);
                sprlock_proc(p);
                p->p_flag |= SFORKING;
                mutex_exit(&p->p_lock);

                error = as_dup(p->p_as, cp);
                if (error != 0) {
                        mutex_enter(&p->p_lock);
                        sprunlock(p);
                        fork_fail(cp);
                        mutex_enter(&pidlock);
                        disown_proc(p, cp);
                        mutex_enter(&cp->p_lock);
                        tk = cp->p_task;
                        task_detach(cp);
                        ASSERT(cp->p_pool->pool_ref > 0);
                        atomic_dec_32(&cp->p_pool->pool_ref);
                        mutex_exit(&cp->p_lock);
                        pid_exit(cp, tk);
                        mutex_exit(&pidlock);
                        task_rele(tk);

                        mutex_enter(&p->p_lock);
                        p->p_flag &= ~SFORKING;
                        pool_barrier_exit();
                        continuelwps(p);
                        mutex_exit(&p->p_lock);
                        /*
                         * Preserve ENOMEM error condition but
                         * map all others to EAGAIN.
                         */
                        error = (error == ENOMEM) ? ENOMEM : EAGAIN;
                        atomic_inc_32(&p->p_zone->zone_ffnomem);
                        goto forkerr;
                }

                /*
                 * Remove all DTrace tracepoints from the child process. We
                 * need to do this _before_ duplicating USDT providers since
                 * any associated probes may be immediately enabled.
                 */
                if (p->p_dtrace_count > 0)
                        dtrace_fasttrap_fork(p, cp);

                mutex_enter(&p->p_lock);
                sprunlock(p);

                /* Duplicate parent's shared memory */
                if (p->p_segacct)
                        shmfork(p, cp);

                /*
                 * Duplicate any helper actions and providers. The SFORKING
                 * we set above informs the code to enable USDT probes that
                 * sprlock() may fail because the child is being forked.
                 */
                if (p->p_dtrace_helpers != NULL) {
                        ASSERT(dtrace_helpers_fork != NULL);
                        (*dtrace_helpers_fork)(p, cp);
                }

                mutex_enter(&p->p_lock);
                p->p_flag &= ~SFORKING;
                mutex_exit(&p->p_lock);
        }

        /*
         * Duplicate parent's resource controls.
         */
        dup_set = rctl_set_create();
        for (;;) {
                dup_gp = rctl_set_dup_prealloc(p->p_rctls);
                mutex_enter(&p->p_rctls->rcs_lock);
                if (rctl_set_dup_ready(p->p_rctls, dup_gp))
                        break;
                mutex_exit(&p->p_rctls->rcs_lock);
                rctl_prealloc_destroy(dup_gp);
        }
        e.rcep_p.proc = cp;
        e.rcep_t = RCENTITY_PROCESS;
        cp->p_rctls = rctl_set_dup(p->p_rctls, p, cp, &e, dup_set, dup_gp,
            RCD_DUP | RCD_CALLBACK);
        mutex_exit(&p->p_rctls->rcs_lock);

        rctl_prealloc_destroy(dup_gp);

        /*
         * Allocate the child's lwp directory and lwpid hash table.
         */
        if (isfork1)
                cp->p_lwpdir_sz = 2;
        else
                cp->p_lwpdir_sz = p->p_lwpdir_sz;
        cp->p_lwpdir = cp->p_lwpfree = ldp =
            kmem_zalloc(cp->p_lwpdir_sz * sizeof (lwpdir_t), KM_SLEEP);
        for (i = 1; i < cp->p_lwpdir_sz; i++, ldp++)
                ldp->ld_next = ldp + 1;
        cp->p_tidhash_sz = (cp->p_lwpdir_sz + 2) / 2;
        cp->p_tidhash =
            kmem_zalloc(cp->p_tidhash_sz * sizeof (tidhash_t), KM_SLEEP);

        /*
         * Duplicate parent's lwps.
         * Mutual exclusion is not needed because the process is
         * in the hold state and only the current lwp is running.
         */
        klgrpset_clear(cp->p_lgrpset);
        if (isfork1) {
                clone = forklwp(ttolwp(curthread), cp, curthread->t_tid);
                if (clone == NULL)
                        goto forklwperr;
                /*
                 * Inherit only the lwp_wait()able flag,
                 * Daemon threads should not call fork1(), but oh well...
                 */
                lwptot(clone)->t_proc_flag |=
                    (curthread->t_proc_flag & TP_TWAIT);
        } else {
                /* this is forkall(), no one can be in lwp_wait() */
                ASSERT(p->p_lwpwait == 0 && p->p_lwpdwait == 0);
                /* for each entry in the parent's lwp directory... */
                for (i = 0, ldp = p->p_lwpdir; i < p->p_lwpdir_sz; i++, ldp++) {
                        klwp_t *clwp;
                        kthread_t *ct;

                        if ((lep = ldp->ld_entry) == NULL)
                                continue;

                        if ((t = lep->le_thread) != NULL) {
                                clwp = forklwp(ttolwp(t), cp, t->t_tid);
                                if (clwp == NULL)
                                        goto forklwperr;
                                ct = lwptot(clwp);
                                /*
                                 * Inherit lwp_wait()able and daemon flags.
                                 */
                                ct->t_proc_flag |=
                                    (t->t_proc_flag & (TP_TWAIT|TP_DAEMON));
                                /*
                                 * Keep track of the clone of curthread to
                                 * post return values through lwp_setrval().
                                 * Mark other threads for special treatment
                                 * by lwp_rtt() / post_syscall().
                                 */
                                if (t == curthread)
                                        clone = clwp;
                                else
                                        ct->t_flag |= T_FORKALL;
                        } else {
                                /*
                                 * Replicate zombie lwps in the child.
                                 */
                                clep = kmem_zalloc(sizeof (*clep), KM_SLEEP);
                                clep->le_lwpid = lep->le_lwpid;
                                clep->le_start = lep->le_start;
                                lwp_hash_in(cp, clep,
                                    cp->p_tidhash, cp->p_tidhash_sz, 0);
                        }
                }
        }

        /*
         * Put new process in the parent's process contract, or put it
         * in a new one if there is an active process template.  Send a
         * fork event (if requested) to whatever contract the child is
         * a member of.  Fails if the parent has been SIGKILLed.
         */
        if (contract_process_fork(NULL, cp, p, B_TRUE) == NULL) {
                atomic_inc_32(&p->p_zone->zone_ffmisc);
                goto forklwperr;
        }

        /*
         * No fork failures occur beyond this point.
         */

        cp->p_lwpid = p->p_lwpid;
        if (!isfork1) {
                cp->p_lwpdaemon = p->p_lwpdaemon;
                cp->p_zombcnt = p->p_zombcnt;
                /*
                 * If the parent's lwp ids have wrapped around, so have the
                 * child's.
                 */
                cp->p_flag |= p->p_flag & SLWPWRAP;
        }

        mutex_enter(&p->p_lock);
        corectl_path_hold(cp->p_corefile = p->p_corefile);
        corectl_content_hold(cp->p_content = p->p_content);
        mutex_exit(&p->p_lock);

        /*
         * Duplicate process context ops, if any.
         */
        if (p->p_pctx)
                forkpctx(p, cp);

#ifdef __sparc
        utrap_dup(p, cp);
#endif
        /*
         * If the child process has been marked to stop on exit
         * from this fork, arrange for all other lwps to stop in
         * sympathy with the active lwp.
         */
        if (PTOU(cp)->u_systrap &&
            prismember(&PTOU(cp)->u_exitmask, curthread->t_sysnum)) {
                mutex_enter(&cp->p_lock);
                t = cp->p_tlist;
                do {
                        t->t_proc_flag |= TP_PRSTOP;
                        aston(t);       /* so TP_PRSTOP will be seen */
                } while ((t = t->t_forw) != cp->p_tlist);
                mutex_exit(&cp->p_lock);
        }
        /*
         * If the parent process has been marked to stop on exit
         * from this fork, and its asynchronous-stop flag has not
         * been set, arrange for all other lwps to stop before
         * they return back to user level.
         */
        if (!(p->p_proc_flag & P_PR_ASYNC) && PTOU(p)->u_systrap &&
            prismember(&PTOU(p)->u_exitmask, curthread->t_sysnum)) {
                mutex_enter(&p->p_lock);
                t = p->p_tlist;
                do {
                        t->t_proc_flag |= TP_PRSTOP;
                        aston(t);       /* so TP_PRSTOP will be seen */
                } while ((t = t->t_forw) != p->p_tlist);
                mutex_exit(&p->p_lock);
        }

        if (PROC_IS_BRANDED(p))
                BROP(p)->b_lwp_setrval(clone, p->p_pid, 1);
        else
                lwp_setrval(clone, p->p_pid, 1);

        /* set return values for parent */
        r.r_val1 = (int)cp->p_pid;
        r.r_val2 = 0;

        /*
         * pool_barrier_exit() can now be called because the child process has:
         * - all identifying features cloned or set (p_pid, p_task, p_pool)
         * - all resource sets associated (p_tlist->*->t_cpupart, p_as->a_mset)
         * - any other fields set which are used in resource set binding.
         */
        mutex_enter(&p->p_lock);
        pool_barrier_exit();
        mutex_exit(&p->p_lock);

        mutex_enter(&pidlock);
        mutex_enter(&cp->p_lock);

        /*
         * Set flags telling the child what (not) to do on exit.
         */
        if (flags & FORK_NOSIGCHLD)
                cp->p_pidflag |= CLDNOSIGCHLD;
        if (flags & FORK_WAITPID)
                cp->p_pidflag |= CLDWAITPID;

        /*
         * Now that there are lwps and threads attached, add the new
         * process to the process group.
         */
        pgjoin(cp, p->p_pgidp);
        cp->p_stat = SRUN;
        /*
         * We are now done with all the lwps in the child process.
         */
        t = cp->p_tlist;
        do {
                /*
                 * Set the lwp_suspend()ed lwps running.
                 * They will suspend properly at syscall exit.
                 */
                if (t->t_proc_flag & TP_HOLDLWP)
                        lwp_create_done(t);
                else {
                        /* set TS_CREATE to allow continuelwps() to work */
                        thread_lock(t);
                        ASSERT(t->t_state == TS_STOPPED &&
                            !(t->t_schedflag & (TS_CREATE|TS_CSTART)));
                        t->t_schedflag |= TS_CREATE;
                        thread_unlock(t);
                }
        } while ((t = t->t_forw) != cp->p_tlist);
        mutex_exit(&cp->p_lock);

        if (isvfork) {
                CPU_STATS_ADDQ(CPU, sys, sysvfork, 1);
                mutex_enter(&p->p_lock);
                p->p_flag |= SVFWAIT;
                curthread->t_flag |= T_VFPARENT;
                DTRACE_PROC1(create, proc_t *, cp);
                cv_broadcast(&pr_pid_cv[p->p_slot]);    /* inform /proc */
                mutex_exit(&p->p_lock);
                /*
                 * Grab child's p_lock before dropping pidlock to ensure
                 * the process will not disappear before we set it running.
                 */
                mutex_enter(&cp->p_lock);
                mutex_exit(&pidlock);
                sigdefault(cp);
                continuelwps(cp);
                mutex_exit(&cp->p_lock);
        } else {
                CPU_STATS_ADDQ(CPU, sys, sysfork, 1);
                DTRACE_PROC1(create, proc_t *, cp);
                /*
                 * It is CL_FORKRET's job to drop pidlock.
                 * If we do it here, the process could be set running
                 * and disappear before CL_FORKRET() is called.
                 */
                CL_FORKRET(curthread, cp->p_tlist);
                schedctl_set_cidpri(curthread);
                ASSERT(MUTEX_NOT_HELD(&pidlock));
        }

        return (r.r_vals);

forklwperr:
        if (isvfork) {
                if (avl_numnodes(&p->p_wpage) != 0) {
                        /* restore watchpoints to parent */
                        as = p->p_as;
                        AS_LOCK_ENTER(as, RW_WRITER);
                        as->a_wpage = p->p_wpage;
                        avl_create(&p->p_wpage, wp_compare,
                            sizeof (struct watched_page),
                            offsetof(struct watched_page, wp_link));
                        as_setwatch(as);
                        AS_LOCK_EXIT(as);
                }
        } else {
                if (cp->p_segacct)
                        shmexit(cp);
                as = cp->p_as;
                cp->p_as = &kas;
                as_free(as);
        }

        if (cp->p_lwpdir) {
                for (i = 0, ldp = cp->p_lwpdir; i < cp->p_lwpdir_sz; i++, ldp++)
                        if ((lep = ldp->ld_entry) != NULL)
                                kmem_free(lep, sizeof (*lep));
                kmem_free(cp->p_lwpdir,
                    cp->p_lwpdir_sz * sizeof (*cp->p_lwpdir));
        }
        cp->p_lwpdir = NULL;
        cp->p_lwpfree = NULL;
        cp->p_lwpdir_sz = 0;

        if (cp->p_tidhash)
                kmem_free(cp->p_tidhash,
                    cp->p_tidhash_sz * sizeof (*cp->p_tidhash));
        cp->p_tidhash = NULL;
        cp->p_tidhash_sz = 0;

        forklwp_fail(cp);
        fork_fail(cp);
        if (cp->p_dtrace_helpers != NULL) {
                ASSERT(dtrace_helpers_cleanup != NULL);
                (*dtrace_helpers_cleanup)(cp);
        }
        rctl_set_free(cp->p_rctls);
        mutex_enter(&pidlock);

        /*
         * Detach failed child from task.
         */
        mutex_enter(&cp->p_lock);
        tk = cp->p_task;
        task_detach(cp);
        ASSERT(cp->p_pool->pool_ref > 0);
        atomic_dec_32(&cp->p_pool->pool_ref);
        mutex_exit(&cp->p_lock);

        disown_proc(p, cp);
        pid_exit(cp, tk);
        mutex_exit(&pidlock);

        task_rele(tk);

        mutex_enter(&p->p_lock);
        pool_barrier_exit();
        continuelwps(p);
        mutex_exit(&p->p_lock);
        error = EAGAIN;
forkerr:
        return ((int64_t)set_errno(error));
}

/*
 * Free allocated resources from getproc() if a fork failed.
 */
static void
fork_fail(proc_t *cp)
{
        uf_info_t *fip = P_FINFO(cp);

        fcnt_add(fip, -1);
        sigdelq(cp, NULL, 0);

        mutex_enter(&pidlock);
        upcount_dec(crgetruid(cp->p_cred), crgetzoneid(cp->p_cred));
        mutex_exit(&pidlock);

        /*
         * single threaded, so no locking needed here
         */
        crfree(cp->p_cred);

        kmem_free(fip->fi_list, fip->fi_nfiles * sizeof (uf_entry_t));

        VN_RELE(PTOU(curproc)->u_cdir);
        if (PTOU(curproc)->u_rdir)
                VN_RELE(PTOU(curproc)->u_rdir);
        if (cp->p_exec)
                VN_RELE(cp->p_exec);
        if (cp->p_execdir)
                VN_RELE(cp->p_execdir);
        if (PTOU(curproc)->u_cwd)
                refstr_rele(PTOU(curproc)->u_cwd);
        if (PROC_IS_BRANDED(cp)) {
                brand_clearbrand(cp, B_TRUE);
        }
}

/*
 * Clean up the lwps already created for this child process.
 * The fork failed while duplicating all the lwps of the parent
 * and those lwps already created must be freed.
 * This process is invisible to the rest of the system,
 * so we don't need to hold p->p_lock to protect the list.
 */
static void
forklwp_fail(proc_t *p)
{
        kthread_t *t;
        task_t *tk;
        int branded = 0;

        if (PROC_IS_BRANDED(p))
                branded = 1;

        while ((t = p->p_tlist) != NULL) {
                /*
                 * First remove the lwp from the process's p_tlist.
                 */
                if (t != t->t_forw)
                        p->p_tlist = t->t_forw;
                else
                        p->p_tlist = NULL;
                p->p_lwpcnt--;
                t->t_forw->t_back = t->t_back;
                t->t_back->t_forw = t->t_forw;

                tk = p->p_task;
                mutex_enter(&p->p_zone->zone_nlwps_lock);
                tk->tk_nlwps--;
                tk->tk_proj->kpj_nlwps--;
                p->p_zone->zone_nlwps--;
                mutex_exit(&p->p_zone->zone_nlwps_lock);

                ASSERT(t->t_schedctl == NULL);

                if (branded)
                        BROP(p)->b_freelwp(ttolwp(t));

                if (t->t_door != NULL) {
                        kmem_free(t->t_door, sizeof (door_data_t));
                        t->t_door = NULL;
                }
                lwp_ctmpl_clear(ttolwp(t));

                /*
                 * Remove the thread from the all threads list.
                 * We need to hold pidlock for this.
                 */
                mutex_enter(&pidlock);
                t->t_next->t_prev = t->t_prev;
                t->t_prev->t_next = t->t_next;
                CL_EXIT(t);     /* tell the scheduler that we're exiting */
                cv_broadcast(&t->t_joincv);     /* tell anyone in thread_join */
                mutex_exit(&pidlock);

                /*
                 * Let the lgroup load averages know that this thread isn't
                 * going to show up (i.e. un-do what was done on behalf of
                 * this thread by the earlier lgrp_move_thread()).
                 */
                kpreempt_disable();
                lgrp_move_thread(t, NULL, 1);
                kpreempt_enable();

                /*
                 * The thread was created TS_STOPPED.
                 * We change it to TS_FREE to avoid an
                 * ASSERT() panic in thread_free().
                 */
                t->t_state = TS_FREE;
                thread_rele(t);
                thread_free(t);
        }
}

extern struct as kas;

/*
 * fork a kernel process.
 */
int
newproc(void (*pc)(), caddr_t arg, id_t cid, int pri, struct contract **ct,
    pid_t pid)
{
        proc_t *p;
        struct user *up;
        kthread_t *t;
        cont_process_t *ctp = NULL;
        rctl_entity_p_t e;

        ASSERT(cid != sysdccid);
        ASSERT(cid != syscid || ct == NULL);
        if (CLASS_KERNEL(cid)) {
                rctl_alloc_gp_t *init_gp;
                rctl_set_t *init_set;

                ASSERT(pid != 1);

                if (getproc(&p, pid, GETPROC_KERNEL) < 0)
                        return (EAGAIN);

                /*
                 * Release the hold on the p_exec and p_execdir, these
                 * were acquired in getproc()
                 */
                if (p->p_execdir != NULL)
                        VN_RELE(p->p_execdir);
                if (p->p_exec != NULL)
                        VN_RELE(p->p_exec);
                p->p_flag |= SNOWAIT;
                p->p_exec = NULL;
                p->p_execdir = NULL;

                init_set = rctl_set_create();
                init_gp = rctl_set_init_prealloc(RCENTITY_PROCESS);

                /*
                 * kernel processes do not inherit /proc tracing flags.
                 */
                sigemptyset(&p->p_sigmask);
                premptyset(&p->p_fltmask);
                up = PTOU(p);
                up->u_systrap = 0;
                premptyset(&(up->u_entrymask));
                premptyset(&(up->u_exitmask));
                mutex_enter(&p->p_lock);
                e.rcep_p.proc = p;
                e.rcep_t = RCENTITY_PROCESS;
                p->p_rctls = rctl_set_init(RCENTITY_PROCESS, p, &e, init_set,
                    init_gp);
                mutex_exit(&p->p_lock);

                rctl_prealloc_destroy(init_gp);

                t = lwp_kernel_create(p, pc, arg, TS_STOPPED, pri);
        } else {
                rctl_alloc_gp_t *init_gp, *default_gp;
                rctl_set_t *init_set;
                task_t *tk, *tk_old;
                klwp_t *lwp;

                if (getproc(&p, pid, GETPROC_USER) < 0)
                        return (EAGAIN);
                /*
                 * init creates a new task, distinct from the task
                 * containing kernel "processes".
                 */
                tk = task_create(0, p->p_zone);
                mutex_enter(&tk->tk_zone->zone_nlwps_lock);
                tk->tk_proj->kpj_ntasks++;
                tk->tk_nprocs++;
                mutex_exit(&tk->tk_zone->zone_nlwps_lock);

                default_gp = rctl_rlimit_set_prealloc(RLIM_NLIMITS);
                init_gp = rctl_set_init_prealloc(RCENTITY_PROCESS);
                init_set = rctl_set_create();

                mutex_enter(&pidlock);
                mutex_enter(&p->p_lock);
                tk_old = p->p_task;     /* switch to new task */

                task_detach(p);
                task_begin(tk, p);
                mutex_exit(&pidlock);

                mutex_enter(&tk_old->tk_zone->zone_nlwps_lock);
                tk_old->tk_nprocs--;
                mutex_exit(&tk_old->tk_zone->zone_nlwps_lock);

                e.rcep_p.proc = p;
                e.rcep_t = RCENTITY_PROCESS;
                p->p_rctls = rctl_set_init(RCENTITY_PROCESS, p, &e, init_set,
                    init_gp);
                rctlproc_default_init(p, default_gp);
                mutex_exit(&p->p_lock);

                task_rele(tk_old);
                rctl_prealloc_destroy(default_gp);
                rctl_prealloc_destroy(init_gp);

                if ((lwp = lwp_create(pc, arg, 0, p, TS_STOPPED, pri,
                    &curthread->t_hold, cid, 1)) == NULL) {
                        task_t *tk;

                        fork_fail(p);
                        mutex_enter(&pidlock);
                        disown_proc(p->p_parent, p);

                        mutex_enter(&p->p_lock);
                        tk = p->p_task;
                        task_detach(p);
                        ASSERT(p->p_pool->pool_ref > 0);
                        atomic_add_32(&p->p_pool->pool_ref, -1);
                        mutex_exit(&p->p_lock);

                        pid_exit(p, tk);
                        mutex_exit(&pidlock);
                        task_rele(tk);
                        return (EAGAIN);
                }
                t = lwptot(lwp);

                ctp = contract_process_fork(sys_process_tmpl, p, curproc,
                    B_FALSE);
                ASSERT(ctp != NULL);
                if (ct != NULL)
                        *ct = &ctp->conp_contract;
        }

        ASSERT3U(t->t_tid, ==, 1);
        p->p_lwpid = 1;
        mutex_enter(&pidlock);
        pgjoin(p, p->p_parent->p_pgidp);
        p->p_stat = SRUN;
        mutex_enter(&p->p_lock);
        t->t_proc_flag &= ~TP_HOLDLWP;
        lwp_create_done(t);
        mutex_exit(&p->p_lock);
        mutex_exit(&pidlock);
        return (0);
}

/*
 * create a child proc struct.
 */
static int
getproc(proc_t **cpp, pid_t pid, uint_t flags)
{
        proc_t          *pp, *cp;
        pid_t           newpid;
        struct user     *uarea;
        extern uint_t   nproc;
        struct cred     *cr;
        uid_t           ruid;
        zoneid_t        zoneid;
        task_t          *task;
        kproject_t      *proj;
        zone_t          *zone;
        int             rctlfail = 0;

        if (zone_status_get(curproc->p_zone) >= ZONE_IS_SHUTTING_DOWN)
                return (-1);    /* no point in starting new processes */

        pp = (flags & GETPROC_KERNEL) ? &p0 : curproc;
        task = pp->p_task;
        proj = task->tk_proj;
        zone = pp->p_zone;

        mutex_enter(&pp->p_lock);
        mutex_enter(&zone->zone_nlwps_lock);
        if (proj != proj0p) {
                if (task->tk_nprocs >= task->tk_nprocs_ctl)
                        if (rctl_test(rc_task_nprocs, task->tk_rctls,
                            pp, 1, 0) & RCT_DENY)
                                rctlfail = 1;

                if (proj->kpj_nprocs >= proj->kpj_nprocs_ctl)
                        if (rctl_test(rc_project_nprocs, proj->kpj_rctls,
                            pp, 1, 0) & RCT_DENY)
                                rctlfail = 1;

                if (zone->zone_nprocs >= zone->zone_nprocs_ctl)
                        if (rctl_test(rc_zone_nprocs, zone->zone_rctls,
                            pp, 1, 0) & RCT_DENY)
                                rctlfail = 1;

                if (rctlfail) {
                        mutex_exit(&zone->zone_nlwps_lock);
                        mutex_exit(&pp->p_lock);
                        atomic_inc_32(&zone->zone_ffcap);
                        goto punish;
                }
        }
        task->tk_nprocs++;
        proj->kpj_nprocs++;
        zone->zone_nprocs++;
        mutex_exit(&zone->zone_nlwps_lock);
        mutex_exit(&pp->p_lock);

        cp = kmem_cache_alloc(process_cache, KM_SLEEP);
        bzero(cp, sizeof (proc_t));

        /*
         * Make proc entry for child process
         */
        mutex_init(&cp->p_splock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&cp->p_crlock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&cp->p_pflock, NULL, MUTEX_DEFAULT, NULL);
#if defined(__x86)
        mutex_init(&cp->p_ldtlock, NULL, MUTEX_DEFAULT, NULL);
#endif
        mutex_init(&cp->p_maplock, NULL, MUTEX_DEFAULT, NULL);
        cp->p_stat = SIDL;
        cp->p_mstart = gethrtime();
        cp->p_as = &kas;
        /*
         * p_zone must be set before we call pid_allocate since the process
         * will be visible after that and code such as prfind_zone will
         * look at the p_zone field.
         */
        cp->p_zone = pp->p_zone;
        cp->p_t1_lgrpid = LGRP_NONE;
        cp->p_tr_lgrpid = LGRP_NONE;

        if ((newpid = pid_allocate(cp, pid, PID_ALLOC_PROC)) == -1) {
                if (nproc == v.v_proc) {
                        CPU_STATS_ADDQ(CPU, sys, procovf, 1);
                        cmn_err(CE_WARN, "out of processes");
                }
                goto bad;
        }

        mutex_enter(&pp->p_lock);
        cp->p_exec = pp->p_exec;
        cp->p_execdir = pp->p_execdir;
        mutex_exit(&pp->p_lock);

        if (cp->p_exec) {
                VN_HOLD(cp->p_exec);
                /*
                 * Each VOP_OPEN() must be paired with a corresponding
                 * VOP_CLOSE(). In this case, the executable will be
                 * closed for the child in either proc_exit() or gexec().
                 */
                if (VOP_OPEN(&cp->p_exec, FREAD, CRED(), NULL) != 0) {
                        VN_RELE(cp->p_exec);
                        cp->p_exec = NULLVP;
                        cp->p_execdir = NULLVP;
                        goto bad;
                }
        }
        if (cp->p_execdir)
                VN_HOLD(cp->p_execdir);

        /*
         * If not privileged make sure that this user hasn't exceeded
         * v.v_maxup processes, and that users collectively haven't
         * exceeded v.v_maxupttl processes.
         */
        mutex_enter(&pidlock);
        ASSERT(nproc < v.v_proc);       /* otherwise how'd we get our pid? */
        cr = CRED();
        ruid = crgetruid(cr);
        zoneid = crgetzoneid(cr);
        if (nproc >= v.v_maxup &&       /* short-circuit; usually false */
            (nproc >= v.v_maxupttl ||
            upcount_get(ruid, zoneid) >= v.v_maxup) &&
            secpolicy_newproc(cr) != 0) {
                mutex_exit(&pidlock);
                zcmn_err(zoneid, CE_NOTE,
                    "out of per-user processes for uid %d", ruid);
                goto bad;
        }

        /*
         * Everything is cool, put the new proc on the active process list.
         * It is already on the pid list and in /proc.
         * Increment the per uid process count (upcount).
         */
        nproc++;
        upcount_inc(ruid, zoneid);

        cp->p_next = practive;
        practive->p_prev = cp;
        practive = cp;

        cp->p_ignore = pp->p_ignore;
        cp->p_siginfo = pp->p_siginfo;
        cp->p_flag = pp->p_flag & (SJCTL|SNOWAIT|SNOCD);
        cp->p_sessp = pp->p_sessp;
        sess_hold(pp);
        cp->p_brand = pp->p_brand;
        if (PROC_IS_BRANDED(pp))
                BROP(pp)->b_copy_procdata(cp, pp);
        cp->p_bssbase = pp->p_bssbase;
        cp->p_brkbase = pp->p_brkbase;
        cp->p_brksize = pp->p_brksize;
        cp->p_brkpageszc = pp->p_brkpageszc;
        cp->p_stksize = pp->p_stksize;
        cp->p_stkpageszc = pp->p_stkpageszc;
        cp->p_stkprot = pp->p_stkprot;
        cp->p_datprot = pp->p_datprot;
        cp->p_usrstack = pp->p_usrstack;
        cp->p_model = pp->p_model;
        cp->p_ppid = pp->p_pid;
        cp->p_ancpid = pp->p_pid;
        cp->p_portcnt = pp->p_portcnt;
        /*
         * Security flags are preserved on fork, the inherited copy come into
         * effect on exec
         */
        cp->p_secflags = pp->p_secflags;

        /*
         * Initialize watchpoint structures
         */
        avl_create(&cp->p_warea, wa_compare, sizeof (struct watched_area),
            offsetof(struct watched_area, wa_link));

        /*
         * Initialize immediate resource control values.
         */
        cp->p_stk_ctl = pp->p_stk_ctl;
        cp->p_fsz_ctl = pp->p_fsz_ctl;
        cp->p_vmem_ctl = pp->p_vmem_ctl;
        cp->p_fno_ctl = pp->p_fno_ctl;

        /*
         * Link up to parent-child-sibling chain.  No need to lock
         * in general since only a call to freeproc() (done by the
         * same parent as newproc()) diddles with the child chain.
         */
        cp->p_sibling = pp->p_child;
        if (pp->p_child)
                pp->p_child->p_psibling = cp;

        cp->p_parent = pp;
        pp->p_child = cp;

        cp->p_child_ns = NULL;
        cp->p_sibling_ns = NULL;

        cp->p_nextorph = pp->p_orphan;
        cp->p_nextofkin = pp;
        pp->p_orphan = cp;

        /*
         * Inherit profiling state; do not inherit REALPROF profiling state.
         */
        cp->p_prof = pp->p_prof;
        cp->p_rprof_cyclic = CYCLIC_NONE;

        /*
         * Inherit pool pointer from the parent.  Kernel processes are
         * always bound to the default pool.
         */
        mutex_enter(&pp->p_lock);
        if (flags & GETPROC_KERNEL) {
                cp->p_pool = pool_default;
                cp->p_flag |= SSYS;
        } else {
                cp->p_pool = pp->p_pool;
        }
        atomic_inc_32(&cp->p_pool->pool_ref);
        mutex_exit(&pp->p_lock);

        /*
         * Add the child process to the current task.  Kernel processes
         * are always attached to task0.
         */
        mutex_enter(&cp->p_lock);
        if (flags & GETPROC_KERNEL)
                task_attach(task0p, cp);
        else
                task_attach(pp->p_task, cp);
        mutex_exit(&cp->p_lock);
        mutex_exit(&pidlock);

        avl_create(&cp->p_ct_held, contract_compar, sizeof (contract_t),
            offsetof(contract_t, ct_ctlist));

        /*
         * Duplicate any audit information kept in the process table
         */
        if (audit_active)       /* copy audit data to cp */
                audit_newproc(cp);

        crhold(cp->p_cred = cr);

        /*
         * Bump up the counts on the file structures pointed at by the
         * parent's file table since the child will point at them too.
         */
        fcnt_add(P_FINFO(pp), 1);

        if (PTOU(pp)->u_cdir) {
                VN_HOLD(PTOU(pp)->u_cdir);
        } else {
                ASSERT(pp == &p0);
                /*
                 * We must be at or before vfs_mountroot(); it will take care of
                 * assigning our current directory.
                 */
        }
        if (PTOU(pp)->u_rdir)
                VN_HOLD(PTOU(pp)->u_rdir);
        if (PTOU(pp)->u_cwd)
                refstr_hold(PTOU(pp)->u_cwd);

        /*
         * copy the parent's uarea.
         */
        uarea = PTOU(cp);
        bcopy(PTOU(pp), uarea, sizeof (*uarea));
        flist_fork(P_FINFO(pp), P_FINFO(cp));

        gethrestime(&uarea->u_start);
        uarea->u_ticks = ddi_get_lbolt();
        uarea->u_mem = rm_asrss(pp->p_as);
        uarea->u_acflag = AFORK;

        /*
         * If inherit-on-fork, copy /proc tracing flags to child.
         */
        if ((pp->p_proc_flag & P_PR_FORK) != 0) {
                cp->p_proc_flag |= pp->p_proc_flag & (P_PR_TRACE|P_PR_FORK);
                cp->p_sigmask = pp->p_sigmask;
                cp->p_fltmask = pp->p_fltmask;
        } else {
                sigemptyset(&cp->p_sigmask);
                premptyset(&cp->p_fltmask);
                uarea->u_systrap = 0;
                premptyset(&uarea->u_entrymask);
                premptyset(&uarea->u_exitmask);
        }
        /*
         * If microstate accounting is being inherited, mark child
         */
        if ((pp->p_flag & SMSFORK) != 0)
                cp->p_flag |= pp->p_flag & (SMSFORK|SMSACCT);

        /*
         * Inherit fixalignment flag from the parent
         */
        cp->p_fixalignment = pp->p_fixalignment;

        *cpp = cp;
        return (0);

bad:
        ASSERT(MUTEX_NOT_HELD(&pidlock));

        mutex_destroy(&cp->p_crlock);
        mutex_destroy(&cp->p_pflock);
#if defined(__x86)
        mutex_destroy(&cp->p_ldtlock);
#endif
        if (newpid != -1) {
                proc_entry_free(cp->p_pidp);
                (void) pid_rele(cp->p_pidp);
        }
        kmem_cache_free(process_cache, cp);

        mutex_enter(&zone->zone_nlwps_lock);
        task->tk_nprocs--;
        proj->kpj_nprocs--;
        zone->zone_nprocs--;
        mutex_exit(&zone->zone_nlwps_lock);
        atomic_inc_32(&zone->zone_ffnoproc);

punish:
        /*
         * We most likely got into this situation because some process is
         * forking out of control.  As punishment, put it to sleep for a
         * bit so it can't eat the machine alive.  Sleep interval is chosen
         * to allow no more than one fork failure per cpu per clock tick
         * on average (yes, I just made this up).  This has two desirable
         * properties: (1) it sets a constant limit on the fork failure
         * rate, and (2) the busier the system is, the harsher the penalty
         * for abusing it becomes.
         */
        INCR_COUNT(&fork_fail_pending, &pidlock);
        delay(fork_fail_pending / ncpus + 1);
        DECR_COUNT(&fork_fail_pending, &pidlock);

        return (-1); /* out of memory or proc slots */
}

/*
 * Release virtual memory.
 * In the case of vfork(), the child was given exclusive access to its
 * parent's address space.  The parent is waiting in vfwait() for the
 * child to release its exclusive claim via relvm().
 */
void
relvm()
{
        proc_t *p = curproc;

        ASSERT((unsigned)p->p_lwpcnt <= 1);

        prrelvm();      /* inform /proc */

        if (p->p_flag & SVFORK) {
                proc_t *pp = p->p_parent;
                /*
                 * The child process is either exec'ing or exit'ing.
                 * The child is now separated from the parent's address
                 * space.  The parent process is made dispatchable.
                 *
                 * This is a delicate locking maneuver, involving
                 * both the parent's p_lock and the child's p_lock.
                 * As soon as the SVFORK flag is turned off, the
                 * parent is free to run, but it must not run until
                 * we wake it up using its p_cv because it might
                 * exit and we would be referencing invalid memory.
                 * Therefore, we hold the parent with its p_lock
                 * while protecting our p_flags with our own p_lock.
                 */
try_again:
                mutex_enter(&p->p_lock);        /* grab child's lock first */
                prbarrier(p);           /* make sure /proc is blocked out */
                mutex_enter(&pp->p_lock);

                /*
                 * Check if parent is locked by /proc.
                 */
                if (pp->p_proc_flag & P_PR_LOCK) {
                        /*
                         * Delay until /proc is done with the parent.
                         * We must drop our (the child's) p->p_lock, wait
                         * via prbarrier() on the parent, then start over.
                         */
                        mutex_exit(&p->p_lock);
                        prbarrier(pp);
                        mutex_exit(&pp->p_lock);
                        goto try_again;
                }
                p->p_flag &= ~SVFORK;
                kpreempt_disable();
                p->p_as = &kas;

                /*
                 * notify hat of change in thread's address space
                 */
                hat_thread_exit(curthread);
                kpreempt_enable();

                /*
                 * child sizes are copied back to parent because
                 * child may have grown.
                 */
                pp->p_brkbase = p->p_brkbase;
                pp->p_brksize = p->p_brksize;
                pp->p_stksize = p->p_stksize;

                /*
                 * Copy back the shm accounting information
                 * to the parent process.
                 */
                pp->p_segacct = p->p_segacct;
                p->p_segacct = NULL;

                /*
                 * The parent is no longer waiting for the vfork()d child.
                 * Restore the parent's watched pages, if any.  This is
                 * safe because we know the parent is not locked by /proc
                 */
                pp->p_flag &= ~SVFWAIT;
                if (avl_numnodes(&pp->p_wpage) != 0) {
                        pp->p_as->a_wpage = pp->p_wpage;
                        avl_create(&pp->p_wpage, wp_compare,
                            sizeof (struct watched_page),
                            offsetof(struct watched_page, wp_link));
                }
                cv_signal(&pp->p_cv);
                mutex_exit(&pp->p_lock);
                mutex_exit(&p->p_lock);
        } else {
                if (p->p_as != &kas) {
                        struct as *as;

                        if (p->p_segacct)
                                shmexit(p);

                        /*
                         * We grab p_lock for the benefit of /proc
                         */
                        kpreempt_disable();
                        mutex_enter(&p->p_lock);
                        prbarrier(p);   /* make sure /proc is blocked out */
                        as = p->p_as;
                        p->p_as = &kas;
                        mutex_exit(&p->p_lock);

                        /*
                         * notify hat of change in thread's address space
                         */
                        hat_thread_exit(curthread);
                        kpreempt_enable();

                        as_free(as);
                        p->p_tr_lgrpid = LGRP_NONE;
                }
        }
}

/*
 * Wait for child to exec or exit.
 * Called by parent of vfork'ed process.
 * See important comments in relvm(), above.
 */
void
vfwait(pid_t pid)
{
        int signalled = 0;
        proc_t *pp = ttoproc(curthread);
        proc_t *cp;

        /*
         * Wait for child to exec or exit.
         */
        for (;;) {
                mutex_enter(&pidlock);
                cp = prfind(pid);
                if (cp == NULL || cp->p_parent != pp) {
                        /*
                         * Child has exit()ed.
                         */
                        mutex_exit(&pidlock);
                        break;
                }
                /*
                 * Grab the child's p_lock before releasing pidlock.
                 * Otherwise, the child could exit and we would be
                 * referencing invalid memory.
                 */
                mutex_enter(&cp->p_lock);
                mutex_exit(&pidlock);
                if (!(cp->p_flag & SVFORK)) {
                        /*
                         * Child has exec()ed or is exit()ing.
                         */
                        mutex_exit(&cp->p_lock);
                        break;
                }
                mutex_enter(&pp->p_lock);
                mutex_exit(&cp->p_lock);
                /*
                 * We might be waked up spuriously from the cv_wait().
                 * We have to do the whole operation over again to be
                 * sure the child's SVFORK flag really is turned off.
                 * We cannot make reference to the child because it can
                 * exit before we return and we would be referencing
                 * invalid memory.
                 *
                 * Because this is potentially a very long-term wait,
                 * we call cv_wait_sig() (for its jobcontrol and /proc
                 * side-effects) unless there is a current signal, in
                 * which case we use cv_wait() because we cannot return
                 * from this function until the child has released the
                 * address space.  Calling cv_wait_sig() with a current
                 * signal would lead to an indefinite loop here because
                 * cv_wait_sig() returns immediately in this case.
                 */
                if (signalled)
                        cv_wait(&pp->p_cv, &pp->p_lock);
                else
                        signalled = !cv_wait_sig(&pp->p_cv, &pp->p_lock);
                mutex_exit(&pp->p_lock);
        }

        /* restore watchpoints to parent */
        if (pr_watch_active(pp)) {
                struct as *as = pp->p_as;
                AS_LOCK_ENTER(as, RW_WRITER);
                as_setwatch(as);
                AS_LOCK_EXIT(as);
        }

        mutex_enter(&pp->p_lock);
        prbarrier(pp);  /* barrier against /proc locking */
        continuelwps(pp);
        mutex_exit(&pp->p_lock);
}