init_main.c

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/*-
 * Copyright (c) 1995 Terrence R. Lambert
 * All rights reserved.
 *
 * Copyright (c) 1982, 1986, 1989, 1991, 1992, 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.
 *
 * 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.
 *
 *      @(#)init_main.c 8.9 (Berkeley) 1/21/94
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include "opt_ddb.h"
#include "opt_init_path.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/exec.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/loginclass.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/proc.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/systm.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/sysent.h>
#include <sys/reboot.h>
#include <sys/sched.h>
#include <sys/sx.h>
#include <sys/sysproto.h>
#include <sys/vmmeter.h>
#include <sys/unistd.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/cpuset.h>

#include <machine/cpu.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <sys/copyright.h>

#include <ddb/ddb.h>
#include <ddb/db_sym.h>

void mi_startup(void);                          /* Should be elsewhere */

/* Components of the first process -- never freed. */
static struct session session0;
static struct pgrp pgrp0;
struct  proc proc0;
struct  thread thread0 __aligned(16);
struct  vmspace vmspace0;
struct  proc *initproc;

int     boothowto = 0;          /* initialized so that it can be patched */
SYSCTL_INT(_debug, OID_AUTO, boothowto, CTLFLAG_RD, &boothowto, 0,
        "Boot control flags, passed from loader");
int     bootverbose;
SYSCTL_INT(_debug, OID_AUTO, bootverbose, CTLFLAG_RW, &bootverbose, 0,
        "Control the output of verbose kernel messages");

/*
 * This ensures that there is at least one entry so that the sysinit_set
 * symbol is not undefined.  A sybsystem ID of SI_SUB_DUMMY is never
 * executed.
 */
SYSINIT(placeholder, SI_SUB_DUMMY, SI_ORDER_ANY, NULL, NULL);

/*
 * The sysinit table itself.  Items are checked off as the are run.
 * If we want to register new sysinit types, add them to newsysinit.
 */
SET_DECLARE(sysinit_set, struct sysinit);
struct sysinit **sysinit, **sysinit_end;
struct sysinit **newsysinit, **newsysinit_end;

/*
 * Merge a new sysinit set into the current set, reallocating it if
 * necessary.  This can only be called after malloc is running.
 */
void
sysinit_add(struct sysinit **set, struct sysinit **set_end)
{
        struct sysinit **newset;
        struct sysinit **sipp;
        struct sysinit **xipp;
        int count;

        count = set_end - set;
        if (newsysinit)
                count += newsysinit_end - newsysinit;
        else
                count += sysinit_end - sysinit;
        newset = malloc(count * sizeof(*sipp), M_TEMP, M_NOWAIT);
        if (newset == NULL)
                panic("cannot malloc for sysinit");
        xipp = newset;
        if (newsysinit)
                for (sipp = newsysinit; sipp < newsysinit_end; sipp++)
                        *xipp++ = *sipp;
        else
                for (sipp = sysinit; sipp < sysinit_end; sipp++)
                        *xipp++ = *sipp;
        for (sipp = set; sipp < set_end; sipp++)
                *xipp++ = *sipp;
        if (newsysinit)
                free(newsysinit, M_TEMP);
        newsysinit = newset;
        newsysinit_end = newset + count;
}

#if defined (DDB) && defined(VERBOSE_SYSINIT)
static const char *
symbol_name(vm_offset_t va, db_strategy_t strategy)
{
        const char *name;
        c_db_sym_t sym;
        db_expr_t  offset;

        if (va == 0)
                return (NULL);
        sym = db_search_symbol(va, strategy, &offset);
        if (offset != 0)
                return (NULL);
        db_symbol_values(sym, &name, NULL);
        return (name);
}
#endif

/*
 * System startup; initialize the world, create process 0, mount root
 * filesystem, and fork to create init and pagedaemon.  Most of the
 * hard work is done in the lower-level initialization routines including
 * startup(), which does memory initialization and autoconfiguration.
 *
 * This allows simple addition of new kernel subsystems that require
 * boot time initialization.  It also allows substitution of subsystem
 * (for instance, a scheduler, kernel profiler, or VM system) by object
 * module.  Finally, it allows for optional "kernel threads".
 */
void
mi_startup(void)
{

        register struct sysinit **sipp;         /* system initialization*/
        register struct sysinit **xipp;         /* interior loop of sort*/
        register struct sysinit *save;          /* bubble*/

#if defined(VERBOSE_SYSINIT)
        int last;
        int verbose;
#endif

        if (boothowto & RB_VERBOSE)
                bootverbose++;

        if (sysinit == NULL) {
                sysinit = SET_BEGIN(sysinit_set);
                sysinit_end = SET_LIMIT(sysinit_set);
        }

restart:
        /*
         * Perform a bubble sort of the system initialization objects by
         * their subsystem (primary key) and order (secondary key).
         */
        for (sipp = sysinit; sipp < sysinit_end; sipp++) {
                for (xipp = sipp + 1; xipp < sysinit_end; xipp++) {
                        if ((*sipp)->subsystem < (*xipp)->subsystem ||
                             ((*sipp)->subsystem == (*xipp)->subsystem &&
                              (*sipp)->order <= (*xipp)->order))
                                continue;       /* skip*/
                        save = *sipp;
                        *sipp = *xipp;
                        *xipp = save;
                }
        }

#if defined(VERBOSE_SYSINIT)
        last = SI_SUB_COPYRIGHT;
        verbose = 0;
#if !defined(DDB)
        printf("VERBOSE_SYSINIT: DDB not enabled, symbol lookups disabled.\n");
#endif
#endif

        /*
         * Traverse the (now) ordered list of system initialization tasks.
         * Perform each task, and continue on to the next task.
         */
        for (sipp = sysinit; sipp < sysinit_end; sipp++) {

                if ((*sipp)->subsystem == SI_SUB_DUMMY)
                        continue;       /* skip dummy task(s)*/

                if ((*sipp)->subsystem == SI_SUB_DONE)
                        continue;

#if defined(VERBOSE_SYSINIT)
                if ((*sipp)->subsystem > last) {
                        verbose = 1;
                        last = (*sipp)->subsystem;
                        printf("subsystem %x\n", last);
                }
                if (verbose) {
#if defined(DDB)
                        const char *func, *data;

                        func = symbol_name((vm_offset_t)(*sipp)->func,
                            DB_STGY_PROC);
                        data = symbol_name((vm_offset_t)(*sipp)->udata,
                            DB_STGY_ANY);
                        if (func != NULL && data != NULL)
                                printf("   %s(&%s)... ", func, data);
                        else if (func != NULL)
                                printf("   %s(%p)... ", func, (*sipp)->udata);
                        else
#endif
                                printf("   %p(%p)... ", (*sipp)->func,
                                    (*sipp)->udata);
                }
#endif

                /* Call function */
                (*((*sipp)->func))((*sipp)->udata);

#if defined(VERBOSE_SYSINIT)
                if (verbose)
                        printf("done.\n");
#endif

                /* Check off the one we're just done */
                (*sipp)->subsystem = SI_SUB_DONE;

                /* Check if we've installed more sysinit items via KLD */
                if (newsysinit != NULL) {
                        if (sysinit != SET_BEGIN(sysinit_set))
                                free(sysinit, M_TEMP);
                        sysinit = newsysinit;
                        sysinit_end = newsysinit_end;
                        newsysinit = NULL;
                        newsysinit_end = NULL;
                        goto restart;
                }
        }

        mtx_assert(&Giant, MA_OWNED | MA_NOTRECURSED);
        mtx_unlock(&Giant);

        /*
         * Now hand over this thread to swapper.
         */
        swapper();
        /* NOTREACHED*/
}


/*
 ***************************************************************************
 ****
 **** The following SYSINIT's belong elsewhere, but have not yet
 **** been moved.
 ****
 ***************************************************************************
 */
static void
print_caddr_t(void *data)
{
        printf("%s", (char *)data);
}

static void
print_version(void *data __unused)
{
        int len;

        /* Strip a trailing newline from version. */
        len = strlen(version);
        while (len > 0 && version[len - 1] == '\n')
                len--;
        printf("%.*s %s\n", len, version, machine);
        printf("%s\n", compiler_version);
}

SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t,
    copyright);
SYSINIT(trademark, SI_SUB_COPYRIGHT, SI_ORDER_SECOND, print_caddr_t,
    trademark);
SYSINIT(version, SI_SUB_COPYRIGHT, SI_ORDER_THIRD, print_version, NULL);

#ifdef WITNESS
static char wit_warn[] =
     "WARNING: WITNESS option enabled, expect reduced performance.\n";
SYSINIT(witwarn, SI_SUB_COPYRIGHT, SI_ORDER_THIRD + 1,
   print_caddr_t, wit_warn);
SYSINIT(witwarn2, SI_SUB_LAST, SI_ORDER_THIRD + 1,
   print_caddr_t, wit_warn);
#endif

#ifdef DIAGNOSTIC
static char diag_warn[] =
     "WARNING: DIAGNOSTIC option enabled, expect reduced performance.\n";
SYSINIT(diagwarn, SI_SUB_COPYRIGHT, SI_ORDER_THIRD + 2,
    print_caddr_t, diag_warn);
SYSINIT(diagwarn2, SI_SUB_LAST, SI_ORDER_THIRD + 2,
    print_caddr_t, diag_warn);
#endif

static int
null_fetch_syscall_args(struct thread *td __unused,
    struct syscall_args *sa __unused)
{

        panic("null_fetch_syscall_args");
}

static void
null_set_syscall_retval(struct thread *td __unused, int error __unused)
{

        panic("null_set_syscall_retval");
}

struct sysentvec null_sysvec = {
        .sv_size        = 0,
        .sv_table       = NULL,
        .sv_mask        = 0,
        .sv_sigsize     = 0,
        .sv_sigtbl      = NULL,
        .sv_errsize     = 0,
        .sv_errtbl      = NULL,
        .sv_transtrap   = NULL,
        .sv_fixup       = NULL,
        .sv_sendsig     = NULL,
        .sv_sigcode     = NULL,
        .sv_szsigcode   = NULL,
        .sv_prepsyscall = NULL,
        .sv_name        = "null",
        .sv_coredump    = NULL,
        .sv_imgact_try  = NULL,
        .sv_minsigstksz = 0,
        .sv_pagesize    = PAGE_SIZE,
        .sv_minuser     = VM_MIN_ADDRESS,
        .sv_maxuser     = VM_MAXUSER_ADDRESS,
        .sv_usrstack    = USRSTACK,
        .sv_psstrings   = PS_STRINGS,
        .sv_stackprot   = VM_PROT_ALL,
        .sv_copyout_strings     = NULL,
        .sv_setregs     = NULL,
        .sv_fixlimit    = NULL,
        .sv_maxssiz     = NULL,
        .sv_flags       = 0,
        .sv_set_syscall_retval = null_set_syscall_retval,
        .sv_fetch_syscall_args = null_fetch_syscall_args,
        .sv_syscallnames = NULL,
        .sv_schedtail   = NULL,
};

/*
 ***************************************************************************
 ****
 **** The two following SYSINIT's are proc0 specific glue code.  I am not
 **** convinced that they can not be safely combined, but their order of
 **** operation has been maintained as the same as the original init_main.c
 **** for right now.
 ****
 **** These probably belong in init_proc.c or kern_proc.c, since they
 **** deal with proc0 (the fork template process).
 ****
 ***************************************************************************
 */
/* ARGSUSED*/
static void
proc0_init(void *dummy __unused)
{
        struct proc *p;
        struct thread *td;
        vm_paddr_t pageablemem;
        int i;

        GIANT_REQUIRED;
        p = &proc0;
        td = &thread0;
        
        /*
         * Initialize magic number and osrel.
         */
        p->p_magic = P_MAGIC;
        p->p_osrel = osreldate;

        /*
         * Initialize thread and process structures.
         */
        procinit();     /* set up proc zone */
        threadinit();   /* set up UMA zones */

        /*
         * Initialise scheduler resources.
         * Add scheduler specific parts to proc, thread as needed.
         */
        schedinit();    /* scheduler gets its house in order */
        /*
         * Initialize sleep queue hash table
         */
        sleepinit();

        /*
         * additional VM structures
         */
        vm_init2();

        /*
         * Create process 0 (the swapper).
         */
        LIST_INSERT_HEAD(&allproc, p, p_list);
        LIST_INSERT_HEAD(PIDHASH(0), p, p_hash);
        mtx_init(&pgrp0.pg_mtx, "process group", NULL, MTX_DEF | MTX_DUPOK);
        p->p_pgrp = &pgrp0;
        LIST_INSERT_HEAD(PGRPHASH(0), &pgrp0, pg_hash);
        LIST_INIT(&pgrp0.pg_members);
        LIST_INSERT_HEAD(&pgrp0.pg_members, p, p_pglist);

        pgrp0.pg_session = &session0;
        mtx_init(&session0.s_mtx, "session", NULL, MTX_DEF);
        refcount_init(&session0.s_count, 1);
        session0.s_leader = p;

        p->p_sysent = &null_sysvec;
        p->p_flag = P_SYSTEM | P_INMEM | P_KTHREAD;
        p->p_flag2 = 0;
        p->p_state = PRS_NORMAL;
        knlist_init_mtx(&p->p_klist, &p->p_mtx);
        STAILQ_INIT(&p->p_ktr);
        p->p_nice = NZERO;
        /* pid_max cannot be greater than PID_MAX */
        td->td_tid = PID_MAX + 1;
        LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
        td->td_state = TDS_RUNNING;
        td->td_pri_class = PRI_TIMESHARE;
        td->td_user_pri = PUSER;
        td->td_base_user_pri = PUSER;
        td->td_lend_user_pri = PRI_MAX;
        td->td_priority = PVM;
        td->td_base_pri = PVM;
        td->td_oncpu = 0;
        td->td_flags = TDF_INMEM|TDP_KTHREAD;
        td->td_cpuset = cpuset_thread0();
        prison0.pr_cpuset = cpuset_ref(td->td_cpuset);
        p->p_peers = 0;
        p->p_leader = p;


        strncpy(p->p_comm, "kernel", sizeof (p->p_comm));
        strncpy(td->td_name, "swapper", sizeof (td->td_name));

        callout_init_mtx(&p->p_itcallout, &p->p_mtx, 0);
        callout_init_mtx(&p->p_limco, &p->p_mtx, 0);
        callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);

        /* Create credentials. */
        p->p_ucred = crget();
        p->p_ucred->cr_ngroups = 1;     /* group 0 */
        p->p_ucred->cr_uidinfo = uifind(0);
        p->p_ucred->cr_ruidinfo = uifind(0);
        p->p_ucred->cr_prison = &prison0;
        p->p_ucred->cr_loginclass = loginclass_find("default");
#ifdef AUDIT
        audit_cred_kproc0(p->p_ucred);
#endif
#ifdef MAC
        mac_cred_create_swapper(p->p_ucred);
#endif
        td->td_ucred = crhold(p->p_ucred);

        /* Create sigacts. */
        p->p_sigacts = sigacts_alloc();

        /* Initialize signal state for process 0. */
        siginit(&proc0);

        /* Create the file descriptor table. */
        p->p_fd = fdinit(NULL);
        p->p_fdtol = NULL;

        /* Create the limits structures. */
        p->p_limit = lim_alloc();
        for (i = 0; i < RLIM_NLIMITS; i++)
                p->p_limit->pl_rlimit[i].rlim_cur =
                    p->p_limit->pl_rlimit[i].rlim_max = RLIM_INFINITY;
        p->p_limit->pl_rlimit[RLIMIT_NOFILE].rlim_cur =
            p->p_limit->pl_rlimit[RLIMIT_NOFILE].rlim_max = maxfiles;
        p->p_limit->pl_rlimit[RLIMIT_NPROC].rlim_cur =
            p->p_limit->pl_rlimit[RLIMIT_NPROC].rlim_max = maxproc;
        p->p_limit->pl_rlimit[RLIMIT_DATA].rlim_cur = dfldsiz;
        p->p_limit->pl_rlimit[RLIMIT_DATA].rlim_max = maxdsiz;
        p->p_limit->pl_rlimit[RLIMIT_STACK].rlim_cur = dflssiz;
        p->p_limit->pl_rlimit[RLIMIT_STACK].rlim_max = maxssiz;
        /* Cast to avoid overflow on i386/PAE. */
        pageablemem = ptoa((vm_paddr_t)cnt.v_free_count);
        p->p_limit->pl_rlimit[RLIMIT_RSS].rlim_cur =
            p->p_limit->pl_rlimit[RLIMIT_RSS].rlim_max = pageablemem;
        p->p_limit->pl_rlimit[RLIMIT_MEMLOCK].rlim_cur = pageablemem / 3;
        p->p_limit->pl_rlimit[RLIMIT_MEMLOCK].rlim_max = pageablemem;
        p->p_cpulimit = RLIM_INFINITY;

        /* Initialize resource accounting structures. */
        racct_create(&p->p_racct);

        p->p_stats = pstats_alloc();

        /* Allocate a prototype map so we have something to fork. */
        pmap_pinit0(vmspace_pmap(&vmspace0));
        p->p_vmspace = &vmspace0;
        vmspace0.vm_refcnt = 1;

        /*
         * proc0 is not expected to enter usermode, so there is no special
         * handling for sv_minuser here, like is done for exec_new_vmspace().
         */
        vm_map_init(&vmspace0.vm_map, vmspace_pmap(&vmspace0),
            p->p_sysent->sv_minuser, p->p_sysent->sv_maxuser);

        /*
         * Call the init and ctor for the new thread and proc.  We wait
         * to do this until all other structures are fairly sane.
         */
        EVENTHANDLER_INVOKE(process_init, p);
        EVENTHANDLER_INVOKE(thread_init, td);
        EVENTHANDLER_INVOKE(process_ctor, p);
        EVENTHANDLER_INVOKE(thread_ctor, td);

        /*
         * Charge root for one process.
         */
        (void)chgproccnt(p->p_ucred->cr_ruidinfo, 1, 0);
        PROC_LOCK(p);
        racct_add_force(p, RACCT_NPROC, 1);
        PROC_UNLOCK(p);
}
SYSINIT(p0init, SI_SUB_INTRINSIC, SI_ORDER_FIRST, proc0_init, NULL);

/* ARGSUSED*/
static void
proc0_post(void *dummy __unused)
{
        struct timespec ts;
        struct proc *p;
        struct rusage ru;
        struct thread *td;

        /*
         * Now we can look at the time, having had a chance to verify the
         * time from the filesystem.  Pretend that proc0 started now.
         */
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                microuptime(&p->p_stats->p_start);
                PROC_SLOCK(p);
                rufetch(p, &ru);        /* Clears thread stats */
                PROC_SUNLOCK(p);
                p->p_rux.rux_runtime = 0;
                p->p_rux.rux_uticks = 0;
                p->p_rux.rux_sticks = 0;
                p->p_rux.rux_iticks = 0;
                FOREACH_THREAD_IN_PROC(p, td) {
                        td->td_runtime = 0;
                }
        }
        sx_sunlock(&allproc_lock);
        PCPU_SET(switchtime, cpu_ticks());
        PCPU_SET(switchticks, ticks);

        /*
         * Give the ``random'' number generator a thump.
         */
        nanotime(&ts);
        srandom(ts.tv_sec ^ ts.tv_nsec);
}
SYSINIT(p0post, SI_SUB_INTRINSIC_POST, SI_ORDER_FIRST, proc0_post, NULL);

static void
random_init(void *dummy __unused)
{

        /*
         * After CPU has been started we have some randomness on most
         * platforms via get_cyclecount().  For platforms that don't
         * we will reseed random(9) in proc0_post() as well.
         */
        srandom(get_cyclecount());
}
SYSINIT(random, SI_SUB_RANDOM, SI_ORDER_FIRST, random_init, NULL);

/*
 ***************************************************************************
 ****
 **** The following SYSINIT's and glue code should be moved to the
 **** respective files on a per subsystem basis.
 ****
 ***************************************************************************
 */


/*
 ***************************************************************************
 ****
 **** The following code probably belongs in another file, like
 **** kern/init_init.c.
 ****
 ***************************************************************************
 */

/*
 * List of paths to try when searching for "init".
 */
static char init_path[MAXPATHLEN] =
#ifdef  INIT_PATH
    __XSTRING(INIT_PATH);
#else
    "/sbin/init:/sbin/oinit:/sbin/init.bak:/rescue/init:/stand/sysinstall";
#endif
SYSCTL_STRING(_kern, OID_AUTO, init_path, CTLFLAG_RD, init_path, 0,
        "Path used to search the init process");

/*
 * Shutdown timeout of init(8).
 * Unused within kernel, but used to control init(8), hence do not remove.
 */
#ifndef INIT_SHUTDOWN_TIMEOUT
#define INIT_SHUTDOWN_TIMEOUT 120
#endif
static int init_shutdown_timeout = INIT_SHUTDOWN_TIMEOUT;
SYSCTL_INT(_kern, OID_AUTO, init_shutdown_timeout,
        CTLFLAG_RW, &init_shutdown_timeout, 0, "Shutdown timeout of init(8). "
        "Unused within kernel, but used to control init(8)");

/*
 * Start the initial user process; try exec'ing each pathname in init_path.
 * The program is invoked with one argument containing the boot flags.
 */
static void
start_init(void *dummy)
{
        vm_offset_t addr;
        struct execve_args args;
        int options, error;
        char *var, *path, *next, *s;
        char *ucp, **uap, *arg0, *arg1;
        struct thread *td;
        struct proc *p;

        mtx_lock(&Giant);

        GIANT_REQUIRED;

        td = curthread;
        p = td->td_proc;

        vfs_mountroot();

        /*
         * Need just enough stack to hold the faked-up "execve()" arguments.
         */
        addr = p->p_sysent->sv_usrstack - PAGE_SIZE;
        if (vm_map_find(&p->p_vmspace->vm_map, NULL, 0, &addr, PAGE_SIZE,
                        FALSE, VM_PROT_ALL, VM_PROT_ALL, 0) != 0)
                panic("init: couldn't allocate argument space");
        p->p_vmspace->vm_maxsaddr = (caddr_t)addr;
        p->p_vmspace->vm_ssize = 1;

        if ((var = getenv("init_path")) != NULL) {
                strlcpy(init_path, var, sizeof(init_path));
                freeenv(var);
        }
        
        for (path = init_path; *path != '\0'; path = next) {
                while (*path == ':')
                        path++;
                if (*path == '\0')
                        break;
                for (next = path; *next != '\0' && *next != ':'; next++)
                        /* nothing */ ;
                if (bootverbose)
                        printf("start_init: trying %.*s\n", (int)(next - path),
                            path);
                        
                /*
                 * Move out the boot flag argument.
                 */
                options = 0;
                ucp = (char *)p->p_sysent->sv_usrstack;
                (void)subyte(--ucp, 0);         /* trailing zero */
                if (boothowto & RB_SINGLE) {
                        (void)subyte(--ucp, 's');
                        options = 1;
                }
#ifdef notyet
                if (boothowto & RB_FASTBOOT) {
                        (void)subyte(--ucp, 'f');
                        options = 1;
                }
#endif

#ifdef BOOTCDROM
                (void)subyte(--ucp, 'C');
                options = 1;
#endif

                if (options == 0)
                        (void)subyte(--ucp, '-');
                (void)subyte(--ucp, '-');               /* leading hyphen */
                arg1 = ucp;

                /*
                 * Move out the file name (also arg 0).
                 */
                (void)subyte(--ucp, 0);
                for (s = next - 1; s >= path; s--)
                        (void)subyte(--ucp, *s);
                arg0 = ucp;

                /*
                 * Move out the arg pointers.
                 */
                uap = (char **)((intptr_t)ucp & ~(sizeof(intptr_t)-1));
                (void)suword((caddr_t)--uap, (long)0);  /* terminator */
                (void)suword((caddr_t)--uap, (long)(intptr_t)arg1);
                (void)suword((caddr_t)--uap, (long)(intptr_t)arg0);

                /*
                 * Point at the arguments.
                 */
                args.fname = arg0;
                args.argv = uap;
                args.envv = NULL;

                /*
                 * Now try to exec the program.  If can't for any reason
                 * other than it doesn't exist, complain.
                 *
                 * Otherwise, return via fork_trampoline() all the way
                 * to user mode as init!
                 */
                if ((error = sys_execve(td, &args)) == 0) {
                        mtx_unlock(&Giant);
                        return;
                }
                if (error != ENOENT)
                        printf("exec %.*s: error %d\n", (int)(next - path), 
                            path, error);
        }
        printf("init: not found in path %s\n", init_path);
        panic("no init");
}

/*
 * Like kproc_create(), but runs in it's own address space.
 * We do this early to reserve pid 1.
 *
 * Note special case - do not make it runnable yet.  Other work
 * in progress will change this more.
 */
static void
create_init(const void *udata __unused)
{
        struct ucred *newcred, *oldcred;
        int error;

        error = fork1(&thread0, RFFDG | RFPROC | RFSTOPPED, 0, &initproc,
            NULL, 0);
        if (error)
                panic("cannot fork init: %d\n", error);
        KASSERT(initproc->p_pid == 1, ("create_init: initproc->p_pid != 1"));
        /* divorce init's credentials from the kernel's */
        newcred = crget();
        PROC_LOCK(initproc);
        initproc->p_flag |= P_SYSTEM | P_INMEM;
        oldcred = initproc->p_ucred;
        crcopy(newcred, oldcred);
#ifdef MAC
        mac_cred_create_init(newcred);
#endif
#ifdef AUDIT
        audit_cred_proc1(newcred);
#endif
        initproc->p_ucred = newcred;
        PROC_UNLOCK(initproc);
        crfree(oldcred);
        cred_update_thread(FIRST_THREAD_IN_PROC(initproc));
        cpu_set_fork_handler(FIRST_THREAD_IN_PROC(initproc), start_init, NULL);
}
SYSINIT(init, SI_SUB_CREATE_INIT, SI_ORDER_FIRST, create_init, NULL);

/*
 * Make it runnable now.
 */
static void
kick_init(const void *udata __unused)
{
        struct thread *td;

        td = FIRST_THREAD_IN_PROC(initproc);
        thread_lock(td);
        TD_SET_CAN_RUN(td);
        sched_add(td, SRQ_BORING);
        thread_unlock(td);
}
SYSINIT(kickinit, SI_SUB_KTHREAD_INIT, SI_ORDER_FIRST, kick_init, NULL);