More -Wwrite-strings cleanup and make sure you can actually play it.

[dragonfly.git] / sys / kern / kern_fork.c

/*
 * Copyright (c) 1982, 1986, 1989, 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.
 *
 * 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.
 *
 *      @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
 * $FreeBSD: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $
 * $DragonFly: src/sys/kern/kern_fork.c,v 1.32 2005/01/31 22:29:59 joerg Exp $
 */

#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/unistd.h>
#include <sys/jail.h>
#include <sys/caps.h>

#include <vm/vm.h>
#include <sys/lock.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>

#include <sys/vmmeter.h>
#include <sys/user.h>

static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");

/*
 * These are the stuctures used to create a callout list for things to do
 * when forking a process
 */
struct forklist {
        forklist_fn function;
        TAILQ_ENTRY(forklist) next;
};

TAILQ_HEAD(forklist_head, forklist);
static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);

int forksleep; /* Place for fork1() to sleep on. */

/* ARGSUSED */
int
fork(struct fork_args *uap)
{
        struct proc *p = curproc;
        struct proc *p2;
        int error;

        error = fork1(p, RFFDG | RFPROC, &p2);
        if (error == 0) {
                start_forked_proc(p, p2);
                uap->sysmsg_fds[0] = p2->p_pid;
                uap->sysmsg_fds[1] = 0;
        }
        return error;
}

/* ARGSUSED */
int
vfork(struct vfork_args *uap)
{
        struct proc *p = curproc;
        struct proc *p2;
        int error;

        error = fork1(p, RFFDG | RFPROC | RFPPWAIT | RFMEM, &p2);
        if (error == 0) {
                start_forked_proc(p, p2);
                uap->sysmsg_fds[0] = p2->p_pid;
                uap->sysmsg_fds[1] = 0;
        }
        return error;
}

/*
 * Handle rforks.  An rfork may (1) operate on the current process without
 * creating a new, (2) create a new process that shared the current process's
 * vmspace, signals, and/or descriptors, or (3) create a new process that does
 * not share these things (normal fork).
 *
 * Note that we only call start_forked_proc() if a new process is actually
 * created.
 *
 * rfork { int flags }
 */
int
rfork(struct rfork_args *uap)
{
        struct proc *p = curproc;
        struct proc *p2;
        int error;

        if ((uap->flags & RFKERNELONLY) != 0)
                return (EINVAL);

        error = fork1(p, uap->flags, &p2);
        if (error == 0) {
                if (p2)
                        start_forked_proc(p, p2);
                uap->sysmsg_fds[0] = p2 ? p2->p_pid : 0;
                uap->sysmsg_fds[1] = 0;
        }
        return error;
}


int     nprocs = 1;             /* process 0 */
static int nextpid = 0;

/*
 * Random component to nextpid generation.  We mix in a random factor to make
 * it a little harder to predict.  We sanity check the modulus value to avoid
 * doing it in critical paths.  Don't let it be too small or we pointlessly
 * waste randomness entropy, and don't let it be impossibly large.  Using a
 * modulus that is too big causes a LOT more process table scans and slows
 * down fork processing as the pidchecked caching is defeated.
 */
static int randompid = 0;

static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
{
                int error, pid;

                pid = randompid;
                error = sysctl_handle_int(oidp, &pid, 0, req);
                if (error || !req->newptr)
                        return (error);
                if (pid < 0 || pid > PID_MAX - 100)     /* out of range */
                        pid = PID_MAX - 100;
                else if (pid < 2)                       /* NOP */
                        pid = 0;
                else if (pid < 100)                     /* Make it reasonable */
                        pid = 100;
                randompid = pid;
                return (error);
}

SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
    0, 0, sysctl_kern_randompid, "I", "Random PID modulus");

int
fork1(struct proc *p1, int flags, struct proc **procp)
{
        struct proc *p2, *pptr;
        uid_t uid;
        struct proc *newproc;
        int ok;
        static int curfail = 0, pidchecked = 0;
        static struct timeval lastfail;
        struct forklist *ep;
        struct filedesc_to_leader *fdtol;

        if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
                return (EINVAL);

        /*
         * Here we don't create a new process, but we divorce
         * certain parts of a process from itself.
         */
        if ((flags & RFPROC) == 0) {

                vm_fork(p1, 0, flags);

                /*
                 * Close all file descriptors.
                 */
                if (flags & RFCFDG) {
                        struct filedesc *fdtmp;
                        fdtmp = fdinit(p1);
                        fdfree(p1);
                        p1->p_fd = fdtmp;
                }

                /*
                 * Unshare file descriptors (from parent.)
                 */
                if (flags & RFFDG) {
                        if (p1->p_fd->fd_refcnt > 1) {
                                struct filedesc *newfd;
                                newfd = fdcopy(p1);
                                fdfree(p1);
                                p1->p_fd = newfd;
                        }
                }
                *procp = NULL;
                return (0);
        }

        /*
         * Although process entries are dynamically created, we still keep
         * a global limit on the maximum number we will create.  Don't allow
         * a nonprivileged user to use the last ten processes; don't let root
         * exceed the limit. The variable nprocs is the current number of
         * processes, maxproc is the limit.
         */
        uid = p1->p_ucred->cr_ruid;
        if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
                if (ppsratecheck(&lastfail, &curfail, 1))
                        printf("maxproc limit exceeded by uid %d, please "
                               "see tuning(7) and login.conf(5).\n", uid);
                tsleep(&forksleep, 0, "fork", hz / 2);
                return (EAGAIN);
        }
        /*
         * Increment the nprocs resource before blocking can occur.  There
         * are hard-limits as to the number of processes that can run.
         */
        nprocs++;

        /*
         * Increment the count of procs running with this uid. Don't allow
         * a nonprivileged user to exceed their current limit.
         */
        ok = chgproccnt(p1->p_ucred->cr_ruidinfo, 1,
                (uid != 0) ? p1->p_rlimit[RLIMIT_NPROC].rlim_cur : 0);
        if (!ok) {
                /*
                 * Back out the process count
                 */
                nprocs--;
                if (ppsratecheck(&lastfail, &curfail, 1))
                        printf("maxproc limit exceeded by uid %d, please "
                               "see tuning(7) and login.conf(5).\n", uid);
                tsleep(&forksleep, 0, "fork", hz / 2);
                return (EAGAIN);
        }

        /* Allocate new proc. */
        newproc = zalloc(proc_zone);

        /*
         * Setup linkage for kernel based threading
         */
        if ((flags & RFTHREAD) != 0) {
                newproc->p_peers = p1->p_peers;
                p1->p_peers = newproc;
                newproc->p_leader = p1->p_leader;
        } else {
                newproc->p_peers = 0;
                newproc->p_leader = newproc;
        }

        newproc->p_wakeup = 0;
        newproc->p_vmspace = NULL;
        TAILQ_INIT(&newproc->p_sysmsgq);

        /*
         * Find an unused process ID.  We remember a range of unused IDs
         * ready to use (from nextpid+1 through pidchecked-1).
         */
        nextpid++;
        if (randompid)
                nextpid += arc4random() % randompid;
retry:
        /*
         * If the process ID prototype has wrapped around,
         * restart somewhat above 0, as the low-numbered procs
         * tend to include daemons that don't exit.
         */
        if (nextpid >= PID_MAX) {
                nextpid = nextpid % PID_MAX;
                if (nextpid < 100)
                        nextpid += 100;
                pidchecked = 0;
        }
        if (nextpid >= pidchecked) {
                int doingzomb = 0;

                pidchecked = PID_MAX;
                /*
                 * Scan the active and zombie procs to check whether this pid
                 * is in use.  Remember the lowest pid that's greater
                 * than nextpid, so we can avoid checking for a while.
                 */
                p2 = LIST_FIRST(&allproc);
again:
                for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
                        while (p2->p_pid == nextpid ||
                            p2->p_pgrp->pg_id == nextpid ||
                            p2->p_session->s_sid == nextpid) {
                                nextpid++;
                                if (nextpid >= pidchecked)
                                        goto retry;
                        }
                        if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
                                pidchecked = p2->p_pid;
                        if (p2->p_pgrp->pg_id > nextpid &&
                            pidchecked > p2->p_pgrp->pg_id)
                                pidchecked = p2->p_pgrp->pg_id;
                        if (p2->p_session->s_sid > nextpid &&
                            pidchecked > p2->p_session->s_sid)
                                pidchecked = p2->p_session->s_sid;
                }
                if (!doingzomb) {
                        doingzomb = 1;
                        p2 = LIST_FIRST(&zombproc);
                        goto again;
                }
        }

        p2 = newproc;
        p2->p_stat = SIDL;                      /* protect against others */
        p2->p_pid = nextpid;
        LIST_INSERT_HEAD(&allproc, p2, p_list);
        LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);

        /*
         * Make a proc table entry for the new process.
         * Start by zeroing the section of proc that is zero-initialized,
         * then copy the section that is copied directly from the parent.
         */
        bzero(&p2->p_startzero,
            (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
        bcopy(&p1->p_startcopy, &p2->p_startcopy,
            (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));

        p2->p_aioinfo = NULL;

        /*
         * Duplicate sub-structures as needed.
         * Increase reference counts on shared objects.
         * The p_stats and p_sigacts substructs are set in vm_fork.
         */
        p2->p_flag = P_INMEM;
        if (p1->p_flag & P_PROFIL)
                startprofclock(p2);
        p2->p_ucred = crhold(p1->p_ucred);

        if (jailed(p2->p_ucred))
                p2->p_flag |= P_JAILED;

        if (p2->p_args)
                p2->p_args->ar_ref++;

        if (flags & RFSIGSHARE) {
                p2->p_procsig = p1->p_procsig;
                p2->p_procsig->ps_refcnt++;
                if (p1->p_sigacts == &p1->p_addr->u_sigacts) {
                        struct sigacts *newsigacts;
                        int s;

                        /* Create the shared sigacts structure */
                        MALLOC(newsigacts, struct sigacts *,
                            sizeof(struct sigacts), M_SUBPROC, M_WAITOK);
                        s = splhigh();
                        /*
                         * Set p_sigacts to the new shared structure.
                         * Note that this is updating p1->p_sigacts at the
                         * same time, since p_sigacts is just a pointer to
                         * the shared p_procsig->ps_sigacts.
                         */
                        p2->p_sigacts  = newsigacts;
                        bcopy(&p1->p_addr->u_sigacts, p2->p_sigacts,
                            sizeof(*p2->p_sigacts));
                        *p2->p_sigacts = p1->p_addr->u_sigacts;
                        splx(s);
                }
        } else {
                MALLOC(p2->p_procsig, struct procsig *, sizeof(struct procsig),
                    M_SUBPROC, M_WAITOK);
                bcopy(p1->p_procsig, p2->p_procsig, sizeof(*p2->p_procsig));
                p2->p_procsig->ps_refcnt = 1;
                p2->p_sigacts = NULL;   /* finished in vm_fork() */
        }
        if (flags & RFLINUXTHPN) 
                p2->p_sigparent = SIGUSR1;
        else
                p2->p_sigparent = SIGCHLD;

        /* bump references to the text vnode (for procfs) */
        p2->p_textvp = p1->p_textvp;
        if (p2->p_textvp)
                vref(p2->p_textvp);

        if (flags & RFCFDG) {
                p2->p_fd = fdinit(p1);
                fdtol = NULL;
        } else if (flags & RFFDG) {
                p2->p_fd = fdcopy(p1);
                fdtol = NULL;
        } else {
                p2->p_fd = fdshare(p1);
                if (p1->p_fdtol == NULL)
                        p1->p_fdtol =
                                filedesc_to_leader_alloc(NULL,
                                                         p1->p_leader);
                if ((flags & RFTHREAD) != 0) {
                        /*
                         * Shared file descriptor table and
                         * shared process leaders.
                         */
                        fdtol = p1->p_fdtol;
                        fdtol->fdl_refcount++;
                } else {
                        /* 
                         * Shared file descriptor table, and
                         * different process leaders 
                         */
                        fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
                }
        }
        p2->p_fdtol = fdtol;

        /*
         * If p_limit is still copy-on-write, bump refcnt,
         * otherwise get a copy that won't be modified.
         * (If PL_SHAREMOD is clear, the structure is shared
         * copy-on-write.)
         */
        if (p1->p_limit->p_lflags & PL_SHAREMOD) {
                p2->p_limit = limcopy(p1->p_limit);
        } else {
                p2->p_limit = p1->p_limit;
                p2->p_limit->p_refcnt++;
        }

        /*
         * Preserve some more flags in subprocess.  P_PROFIL has already
         * been preserved.
         */
        p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
        if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
                p2->p_flag |= P_CONTROLT;
        if (flags & RFPPWAIT)
                p2->p_flag |= P_PPWAIT;

        /*
         * Once we are on a pglist we may receive signals.  XXX we might
         * race a ^C being sent to the process group by not receiving it
         * at all prior to this line.
         */
        LIST_INSERT_AFTER(p1, p2, p_pglist);

        /*
         * Attach the new process to its parent.
         *
         * If RFNOWAIT is set, the newly created process becomes a child
         * of init.  This effectively disassociates the child from the
         * parent.
         */
        if (flags & RFNOWAIT)
                pptr = initproc;
        else
                pptr = p1;
        p2->p_pptr = pptr;
        LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
        LIST_INIT(&p2->p_children);
        varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
        callout_init(&p2->p_ithandle);

#ifdef KTRACE
        /*
         * Copy traceflag and tracefile if enabled.  If not inherited,
         * these were zeroed above but we still could have a trace race
         * so make sure p2's p_tracep is NULL.
         */
        if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) {
                p2->p_traceflag = p1->p_traceflag;
                if ((p2->p_tracep = p1->p_tracep) != NULL)
                        vref(p2->p_tracep);
        }
#endif

        /*
         * Give the child process an estcpu skewed towards the batch side
         * of the parent.  This prevents batch programs from glitching 
         * interactive programs when they are first started.  If the child
         * is not a batch program it's priority will be corrected by the
         * scheduler.
         *
         * The interactivity model always starts at 0 (par value).
         */
        p2->p_estcpu_fork = p2->p_estcpu = 
                ESTCPULIM(p1->p_estcpu + ESTCPURAMP);
        p2->p_interactive = 0;

        /*
         * This begins the section where we must prevent the parent
         * from being swapped.
         */
        PHOLD(p1);

        /*
         * Finish creating the child process.  It will return via a different
         * execution path later.  (ie: directly into user mode)
         */
        vm_fork(p1, p2, flags);
        caps_fork(p1, p2, flags);

        if (flags == (RFFDG | RFPROC)) {
                mycpu->gd_cnt.v_forks++;
                mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
        } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
                mycpu->gd_cnt.v_vforks++;
                mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
        } else if (p1 == &proc0) {
                mycpu->gd_cnt.v_kthreads++;
                mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
        } else {
                mycpu->gd_cnt.v_rforks++;
                mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize + p2->p_vmspace->vm_ssize;
        }

        /*
         * Both processes are set up, now check if any loadable modules want
         * to adjust anything.
         *   What if they have an error? XXX
         */
        TAILQ_FOREACH(ep, &fork_list, next) {
                (*ep->function)(p1, p2, flags);
        }

        /*
         * Make child runnable and add to run queue.
         */
        microtime(&p2->p_thread->td_start);
        p2->p_acflag = AFORK;

        /*
         * tell any interested parties about the new process
         */
        KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);

        /*
         * Return child proc pointer to parent.
         */
        *procp = p2;
        return (0);
}

/*
 * The next two functionms are general routines to handle adding/deleting
 * items on the fork callout list.
 *
 * at_fork():
 * Take the arguments given and put them onto the fork callout list,
 * However first make sure that it's not already there.
 * Returns 0 on success or a standard error number.
 */
int
at_fork(forklist_fn function)
{
        struct forklist *ep;

#ifdef INVARIANTS
        /* let the programmer know if he's been stupid */
        if (rm_at_fork(function)) {
                printf("WARNING: fork callout entry (%p) already present\n",
                    function);
        }
#endif
        ep = malloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
        ep->function = function;
        TAILQ_INSERT_TAIL(&fork_list, ep, next);
        return (0);
}

/*
 * Scan the exit callout list for the given item and remove it..
 * Returns the number of items removed (0 or 1)
 */
int
rm_at_fork(forklist_fn function)
{
        struct forklist *ep;

        TAILQ_FOREACH(ep, &fork_list, next) {
                if (ep->function == function) {
                        TAILQ_REMOVE(&fork_list, ep, next);
                        free(ep, M_ATFORK);
                        return(1);
                }
        }       
        return (0);
}

/*
 * Add a forked process to the run queue after any remaining setup, such
 * as setting the fork handler, has been completed.
 */
void
start_forked_proc(struct proc *p1, struct proc *p2)
{
        /*
         * Move from SIDL to RUN queue, and activate the process's thread.
         * Activation of the thread effectively makes the process "a"
         * current process, so we do not setrunqueue().
         *
         * YYY setrunqueue works here but we should clean up the trampoline
         * code so we just schedule the LWKT thread and let the trampoline
         * deal with the userland scheduler on return to userland.
         */
        KASSERT(p2 && p2->p_stat == SIDL,
            ("cannot start forked process, bad status: %p", p2));
        resetpriority(p2);
        (void) splhigh();
        p2->p_stat = SRUN;
        setrunqueue(p2);
        (void) spl0();

        /*
         * Now can be swapped.
         */
        PRELE(p1);

        /*
         * Preserve synchronization semantics of vfork.  If waiting for
         * child to exec or exit, set P_PPWAIT on child, and sleep on our
         * proc (in case of exit).
         */
        while (p2->p_flag & P_PPWAIT)
                tsleep(p1, 0, "ppwait", 0);
}