sys/kern/kern_fork.c

   1 /*
   2  * Copyright (c) 1982, 1986, 1989, 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * (c) UNIX System Laboratories, Inc.
   5  * All or some portions of this file are derived from material licensed
   6  * to the University of California by American Telephone and Telegraph
   7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   8  * the permission of UNIX System Laboratories, Inc.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  *      @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
  35  * $FreeBSD: src/sys/kern/kern_fork.c,v 1.72.2.14 2003/06/26 04:15:10 silby Exp $
  36  */
  37
  38 #include "opt_ktrace.h"
  39
  40 #include <sys/param.h>
  41 #include <sys/systm.h>
  42 #include <sys/sysproto.h>
  43 #include <sys/filedesc.h>
  44 #include <sys/kernel.h>
  45 #include <sys/sysctl.h>
  46 #include <sys/malloc.h>
  47 #include <sys/proc.h>
  48 #include <sys/resourcevar.h>
  49 #include <sys/vnode.h>
  50 #include <sys/acct.h>
  51 #include <sys/ktrace.h>
  52 #include <sys/unistd.h>
  53 #include <sys/jail.h>
  54 #include <sys/lwp.h>
  55
  56 #include <vm/vm.h>
  57 #include <sys/lock.h>
  58 #include <vm/pmap.h>
  59 #include <vm/vm_map.h>
  60 #include <vm/vm_extern.h>
  61
  62 #include <sys/vmmeter.h>
  63 #include <sys/refcount.h>
  64 #include <sys/thread2.h>
  65 #include <sys/signal2.h>
  66 #include <sys/spinlock2.h>
  67
  68 #include <sys/dsched.h>
  69
  70 static MALLOC_DEFINE(M_ATFORK, "atfork", "atfork callback");
  71 static MALLOC_DEFINE(M_REAPER, "reaper", "process reapers");
  72
  73 /*
  74  * These are the stuctures used to create a callout list for things to do
  75  * when forking a process
  76  */
  77 struct forklist {
  78         forklist_fn function;
  79         TAILQ_ENTRY(forklist) next;
  80 };
  81
  82 TAILQ_HEAD(forklist_head, forklist);
  83 static struct forklist_head fork_list = TAILQ_HEAD_INITIALIZER(fork_list);
  84
  85 static struct lwp       *lwp_fork(struct lwp *, struct proc *, int flags,
  86                             const cpumask_t *mask);
  87 static int              lwp_create1(struct lwp_params *params,
  88                             const cpumask_t *mask);
  89 static struct lock reaper_lock = LOCK_INITIALIZER("reapgl", 0, 0);
  90
  91 int forksleep; /* Place for fork1() to sleep on. */
  92
  93 /*
  94  * Red-Black tree support for LWPs
  95  */
  96
  97 static int
  98 rb_lwp_compare(struct lwp *lp1, struct lwp *lp2)
  99 {
 100         if (lp1->lwp_tid < lp2->lwp_tid)
 101                 return(-1);
 102         if (lp1->lwp_tid > lp2->lwp_tid)
 103                 return(1);
 104         return(0);
 105 }
 106
 107 RB_GENERATE2(lwp_rb_tree, lwp, u.lwp_rbnode, rb_lwp_compare, lwpid_t, lwp_tid);
 108
 109 /*
 110  * When forking, memory underpinning umtx-supported mutexes may be set
 111  * COW causing the physical address to change.  We must wakeup any threads
 112  * blocked on the physical address to allow them to re-resolve their VM.
 113  *
 114  * (caller is holding p->p_token)
 115  */
 116 static void
 117 wake_umtx_threads(struct proc *p1)
 118 {
 119         struct lwp *lp;
 120         struct thread *td;
 121
 122         RB_FOREACH(lp, lwp_rb_tree, &p1->p_lwp_tree) {
 123                 td = lp->lwp_thread;
 124                 if (td && (td->td_flags & TDF_TSLEEPQ) &&
 125                     (td->td_wdomain & PDOMAIN_MASK) == PDOMAIN_UMTX) {
 126                         wakeup_domain(td->td_wchan, PDOMAIN_UMTX);
 127                 }
 128         }
 129 }
 130
 131 /*
 132  * fork() system call
 133  */
 134 int
 135 sys_fork(struct fork_args *uap)
 136 {
 137         struct lwp *lp = curthread->td_lwp;
 138         struct proc *p2;
 139         int error;
 140
 141         error = fork1(lp, RFFDG | RFPROC | RFPGLOCK, &p2);
 142         if (error == 0) {
 143                 PHOLD(p2);
 144                 start_forked_proc(lp, p2);
 145                 uap->sysmsg_fds[0] = p2->p_pid;
 146                 uap->sysmsg_fds[1] = 0;
 147                 PRELE(p2);
 148         }
 149         return error;
 150 }
 151
 152 /*
 153  * vfork() system call
 154  */
 155 int
 156 sys_vfork(struct vfork_args *uap)
 157 {
 158         struct lwp *lp = curthread->td_lwp;
 159         struct proc *p2;
 160         int error;
 161
 162         error = fork1(lp, RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK, &p2);
 163         if (error == 0) {
 164                 PHOLD(p2);
 165                 start_forked_proc(lp, p2);
 166                 uap->sysmsg_fds[0] = p2->p_pid;
 167                 uap->sysmsg_fds[1] = 0;
 168                 PRELE(p2);
 169         }
 170         return error;
 171 }
 172
 173 /*
 174  * Handle rforks.  An rfork may (1) operate on the current process without
 175  * creating a new, (2) create a new process that shared the current process's
 176  * vmspace, signals, and/or descriptors, or (3) create a new process that does
 177  * not share these things (normal fork).
 178  *
 179  * Note that we only call start_forked_proc() if a new process is actually
 180  * created.
 181  *
 182  * rfork { int flags }
 183  */
 184 int
 185 sys_rfork(struct rfork_args *uap)
 186 {
 187         struct lwp *lp = curthread->td_lwp;
 188         struct proc *p2;
 189         int error;
 190
 191         if ((uap->flags & RFKERNELONLY) != 0)
 192                 return (EINVAL);
 193
 194         error = fork1(lp, uap->flags | RFPGLOCK, &p2);
 195         if (error == 0) {
 196                 if (p2) {
 197                         PHOLD(p2);
 198                         start_forked_proc(lp, p2);
 199                         uap->sysmsg_fds[0] = p2->p_pid;
 200                         uap->sysmsg_fds[1] = 0;
 201                         PRELE(p2);
 202                 } else {
 203                         uap->sysmsg_fds[0] = 0;
 204                         uap->sysmsg_fds[1] = 0;
 205                 }
 206         }
 207         return error;
 208 }
 209
 210 static int
 211 lwp_create1(struct lwp_params *uprm, const cpumask_t *umask)
 212 {
 213         struct proc *p = curproc;
 214         struct lwp *lp;
 215         struct lwp_params params;
 216         cpumask_t *mask = NULL, mask0;
 217         int error;
 218
 219         error = copyin(uprm, &params, sizeof(params));
 220         if (error)
 221                 goto fail2;
 222
 223         if (umask != NULL) {
 224                 error = copyin(umask, &mask0, sizeof(mask0));
 225                 if (error)
 226                         goto fail2;
 227                 CPUMASK_ANDMASK(mask0, smp_active_mask);
 228                 if (CPUMASK_TESTNZERO(mask0))
 229                         mask = &mask0;
 230         }
 231
 232         lwkt_gettoken(&p->p_token);
 233         plimit_lwp_fork(p);     /* force exclusive access */
 234         lp = lwp_fork(curthread->td_lwp, p, RFPROC | RFMEM, mask);
 235         error = cpu_prepare_lwp(lp, &params);
 236         if (error)
 237                 goto fail;
 238         if (params.lwp_tid1 != NULL &&
 239             (error = copyout(&lp->lwp_tid, params.lwp_tid1, sizeof(lp->lwp_tid))))
 240                 goto fail;
 241         if (params.lwp_tid2 != NULL &&
 242             (error = copyout(&lp->lwp_tid, params.lwp_tid2, sizeof(lp->lwp_tid))))
 243                 goto fail;
 244
 245         /*
 246          * Now schedule the new lwp.
 247          */
 248         p->p_usched->resetpriority(lp);
 249         crit_enter();
 250         lp->lwp_stat = LSRUN;
 251         p->p_usched->setrunqueue(lp);
 252         crit_exit();
 253         lwkt_reltoken(&p->p_token);
 254
 255         return (0);
 256
 257 fail:
 258         /*
 259          * Make sure no one is using this lwp, before it is removed from
 260          * the tree.  If we didn't wait it here, lwp tree iteration with
 261          * blocking operation would be broken.
 262          */
 263         while (lp->lwp_lock > 0)
 264                 tsleep(lp, 0, "lwpfail", 1);
 265         lwp_rb_tree_RB_REMOVE(&p->p_lwp_tree, lp);
 266         --p->p_nthreads;
 267         /* lwp_dispose expects an exited lwp, and a held proc */
 268         atomic_set_int(&lp->lwp_mpflags, LWP_MP_WEXIT);
 269         lp->lwp_thread->td_flags |= TDF_EXITING;
 270         lwkt_remove_tdallq(lp->lwp_thread);
 271         PHOLD(p);
 272         biosched_done(lp->lwp_thread);
 273         dsched_exit_thread(lp->lwp_thread);
 274         lwp_dispose(lp);
 275         lwkt_reltoken(&p->p_token);
 276 fail2:
 277         return (error);
 278 }
 279
 280 /*
 281  * Low level thread create used by pthreads.
 282  */
 283 int
 284 sys_lwp_create(struct lwp_create_args *uap)
 285 {
 286
 287         return (lwp_create1(uap->params, NULL));
 288 }
 289
 290 int
 291 sys_lwp_create2(struct lwp_create2_args *uap)
 292 {
 293
 294         return (lwp_create1(uap->params, uap->mask));
 295 }
 296
 297 int     nprocs = 1;             /* process 0 */
 298
 299 int
 300 fork1(struct lwp *lp1, int flags, struct proc **procp)
 301 {
 302         struct proc *p1 = lp1->lwp_proc;
 303         struct proc *p2;
 304         struct proc *pptr;
 305         struct pgrp *p1grp;
 306         struct pgrp *plkgrp;
 307         struct sysreaper *reap;
 308         uid_t uid;
 309         int ok, error;
 310         static int curfail = 0;
 311         static struct timeval lastfail;
 312         struct forklist *ep;
 313         struct filedesc_to_leader *fdtol;
 314
 315         if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
 316                 return (EINVAL);
 317
 318         lwkt_gettoken(&p1->p_token);
 319         plkgrp = NULL;
 320         p2 = NULL;
 321
 322         /*
 323          * Here we don't create a new process, but we divorce
 324          * certain parts of a process from itself.
 325          */
 326         if ((flags & RFPROC) == 0) {
 327                 /*
 328                  * This kind of stunt does not work anymore if
 329                  * there are native threads (lwps) running
 330                  */
 331                 if (p1->p_nthreads != 1) {
 332                         error = EINVAL;
 333                         goto done;
 334                 }
 335
 336                 vm_fork(p1, 0, flags);
 337                 if ((flags & RFMEM) == 0)
 338                         wake_umtx_threads(p1);
 339
 340                 /*
 341                  * Close all file descriptors.
 342                  */
 343                 if (flags & RFCFDG) {
 344                         struct filedesc *fdtmp;
 345                         fdtmp = fdinit(p1);
 346                         fdfree(p1, fdtmp);
 347                 }
 348
 349                 /*
 350                  * Unshare file descriptors (from parent.)
 351                  */
 352                 if (flags & RFFDG) {
 353                         if (p1->p_fd->fd_refcnt > 1) {
 354                                 struct filedesc *newfd;
 355                                 error = fdcopy(p1, &newfd);
 356                                 if (error != 0) {
 357                                         error = ENOMEM;
 358                                         goto done;
 359                                 }
 360                                 fdfree(p1, newfd);
 361                         }
 362                 }
 363                 *procp = NULL;
 364                 error = 0;
 365                 goto done;
 366         }
 367
 368         /*
 369          * Interlock against process group signal delivery.  If signals
 370          * are pending after the interlock is obtained we have to restart
 371          * the system call to process the signals.  If we don't the child
 372          * can miss a pgsignal (such as ^C) sent during the fork.
 373          *
 374          * We can't use CURSIG() here because it will process any STOPs
 375          * and cause the process group lock to be held indefinitely.  If
 376          * a STOP occurs, the fork will be restarted after the CONT.
 377          */
 378         p1grp = p1->p_pgrp;
 379         if ((flags & RFPGLOCK) && (plkgrp = p1->p_pgrp) != NULL) {
 380                 pgref(plkgrp);
 381                 lockmgr(&plkgrp->pg_lock, LK_SHARED);
 382                 if (CURSIG_NOBLOCK(lp1)) {
 383                         error = ERESTART;
 384                         goto done;
 385                 }
 386         }
 387
 388         /*
 389          * Although process entries are dynamically created, we still keep
 390          * a global limit on the maximum number we will create.  Don't allow
 391          * a nonprivileged user to use the last ten processes; don't let root
 392          * exceed the limit. The variable nprocs is the current number of
 393          * processes, maxproc is the limit.
 394          */
 395         uid = lp1->lwp_thread->td_ucred->cr_ruid;
 396         if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) {
 397                 if (ppsratecheck(&lastfail, &curfail, 1))
 398                         kprintf("maxproc limit exceeded by uid %d, please "
 399                                "see tuning(7) and login.conf(5).\n", uid);
 400                 tsleep(&forksleep, 0, "fork", hz / 2);
 401                 error = EAGAIN;
 402                 goto done;
 403         }
 404
 405         /*
 406          * Increment the nprocs resource before blocking can occur.  There
 407          * are hard-limits as to the number of processes that can run.
 408          */
 409         atomic_add_int(&nprocs, 1);
 410
 411         /*
 412          * Increment the count of procs running with this uid.  This also
 413          * applies to root.
 414          */
 415         ok = chgproccnt(lp1->lwp_thread->td_ucred->cr_ruidinfo, 1,
 416                         plimit_getadjvalue(RLIMIT_NPROC));
 417         if (!ok) {
 418                 /*
 419                  * Back out the process count
 420                  */
 421                 atomic_add_int(&nprocs, -1);
 422                 if (ppsratecheck(&lastfail, &curfail, 1)) {
 423                         kprintf("maxproc limit of %jd "
 424                                 "exceeded by \"%s\" uid %d, "
 425                                 "please see tuning(7) and login.conf(5).\n",
 426                                 plimit_getadjvalue(RLIMIT_NPROC),
 427                                 p1->p_comm,
 428                                 uid);
 429                 }
 430                 tsleep(&forksleep, 0, "fork", hz / 2);
 431                 error = EAGAIN;
 432                 goto done;
 433         }
 434
 435         /*
 436          * Allocate a new process, don't get fancy: zero the structure.
 437          */
 438         p2 = kmalloc(sizeof(struct proc), M_PROC, M_WAITOK|M_ZERO);
 439
 440         /*
 441          * Core initialization.  SIDL is a safety state that protects the
 442          * partially initialized process once it starts getting hooked
 443          * into system structures and becomes addressable.
 444          *
 445          * We must be sure to acquire p2->p_token as well, we must hold it
 446          * once the process is on the allproc list to avoid things such
 447          * as competing modifications to p_flags.
 448          */
 449         mycpu->gd_forkid += ncpus;
 450         p2->p_forkid = mycpu->gd_forkid + mycpu->gd_cpuid;
 451         p2->p_lasttid = 0;      /* first tid will be 1 */
 452         p2->p_stat = SIDL;
 453
 454         /*
 455          * NOTE: Process 0 will not have a reaper, but process 1 (init) and
 456          *       all other processes always will.
 457          */
 458         if ((reap = p1->p_reaper) != NULL) {
 459                 reaper_hold(reap);
 460                 p2->p_reaper = reap;
 461         } else {
 462                 p2->p_reaper = NULL;
 463         }
 464
 465         RB_INIT(&p2->p_lwp_tree);
 466         spin_init(&p2->p_spin, "procfork1");
 467         lwkt_token_init(&p2->p_token, "proc");
 468         lwkt_gettoken(&p2->p_token);
 469         p2->p_uidpcpu = kmalloc(sizeof(*p2->p_uidpcpu) * ncpus,
 470                                 M_SUBPROC, M_WAITOK | M_ZERO);
 471
 472         /*
 473          * Setup linkage for kernel based threading XXX lwp.  Also add the
 474          * process to the allproclist.
 475          *
 476          * The process structure is addressable after this point.
 477          */
 478         if (flags & RFTHREAD) {
 479                 p2->p_peers = p1->p_peers;
 480                 p1->p_peers = p2;
 481                 p2->p_leader = p1->p_leader;
 482         } else {
 483                 p2->p_leader = p2;
 484         }
 485         proc_add_allproc(p2);
 486
 487         /*
 488          * Initialize the section which is copied verbatim from the parent.
 489          */
 490         bcopy(&p1->p_startcopy, &p2->p_startcopy,
 491               ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
 492
 493         /*
 494          * Duplicate sub-structures as needed.  Increase reference counts
 495          * on shared objects.
 496          *
 497          * NOTE: because we are now on the allproc list it is possible for
 498          *       other consumers to gain temporary references to p2
 499          *       (p2->p_lock can change).
 500          */
 501         if (p1->p_flags & P_PROFIL)
 502                 startprofclock(p2);
 503         p2->p_ucred = crhold(lp1->lwp_thread->td_ucred);
 504
 505         if (jailed(p2->p_ucred))
 506                 p2->p_flags |= P_JAILED;
 507
 508         if (p2->p_args)
 509                 refcount_acquire(&p2->p_args->ar_ref);
 510
 511         p2->p_usched = p1->p_usched;
 512         /* XXX: verify copy of the secondary iosched stuff */
 513         dsched_enter_proc(p2);
 514
 515         if (flags & RFSIGSHARE) {
 516                 p2->p_sigacts = p1->p_sigacts;
 517                 refcount_acquire(&p2->p_sigacts->ps_refcnt);
 518         } else {
 519                 p2->p_sigacts = kmalloc(sizeof(*p2->p_sigacts),
 520                                         M_SUBPROC, M_WAITOK);
 521                 bcopy(p1->p_sigacts, p2->p_sigacts, sizeof(*p2->p_sigacts));
 522                 refcount_init(&p2->p_sigacts->ps_refcnt, 1);
 523         }
 524         if (flags & RFLINUXTHPN)
 525                 p2->p_sigparent = SIGUSR1;
 526         else
 527                 p2->p_sigparent = SIGCHLD;
 528
 529         /* bump references to the text vnode (for procfs) */
 530         p2->p_textvp = p1->p_textvp;
 531         if (p2->p_textvp)
 532                 vref(p2->p_textvp);
 533
 534         /* copy namecache handle to the text file */
 535         if (p1->p_textnch.mount)
 536                 cache_copy(&p1->p_textnch, &p2->p_textnch);
 537
 538         /*
 539          * Handle file descriptors
 540          */
 541         if (flags & RFCFDG) {
 542                 p2->p_fd = fdinit(p1);
 543                 fdtol = NULL;
 544         } else if (flags & RFFDG) {
 545                 error = fdcopy(p1, &p2->p_fd);
 546                 if (error != 0) {
 547                         error = ENOMEM;
 548                         goto done;
 549                 }
 550                 fdtol = NULL;
 551         } else {
 552                 p2->p_fd = fdshare(p1);
 553                 if (p1->p_fdtol == NULL) {
 554                         p1->p_fdtol = filedesc_to_leader_alloc(NULL,
 555                                                                p1->p_leader);
 556                 }
 557                 if ((flags & RFTHREAD) != 0) {
 558                         /*
 559                          * Shared file descriptor table and
 560                          * shared process leaders.
 561                          */
 562                         fdtol = p1->p_fdtol;
 563                         fdtol->fdl_refcount++;
 564                 } else {
 565                         /*
 566                          * Shared file descriptor table, and
 567                          * different process leaders
 568                          */
 569                         fdtol = filedesc_to_leader_alloc(p1->p_fdtol, p2);
 570                 }
 571         }
 572         p2->p_fdtol = fdtol;
 573         p2->p_limit = plimit_fork(p1);
 574
 575         /*
 576          * Adjust depth for resource downscaling
 577          */
 578         if ((p2->p_depth & 31) != 31)
 579                 ++p2->p_depth;
 580
 581         /*
 582          * Preserve some more flags in subprocess.  P_PROFIL has already
 583          * been preserved.
 584          */
 585         p2->p_flags |= p1->p_flags & P_SUGID;
 586         if (p1->p_session->s_ttyvp != NULL && (p1->p_flags & P_CONTROLT))
 587                 p2->p_flags |= P_CONTROLT;
 588         if (flags & RFPPWAIT) {
 589                 p2->p_flags |= P_PPWAIT;
 590                 if (p1->p_upmap)
 591                         atomic_add_int(&p1->p_upmap->invfork, 1);
 592         }
 593
 594         /*
 595          * Inherit the virtual kernel structure (allows a virtual kernel
 596          * to fork to simulate multiple cpus).
 597          */
 598         if (p1->p_vkernel)
 599                 vkernel_inherit(p1, p2);
 600
 601         /*
 602          * Once we are on a pglist we may receive signals.  XXX we might
 603          * race a ^C being sent to the process group by not receiving it
 604          * at all prior to this line.
 605          */
 606         pgref(p1grp);
 607         lwkt_gettoken(&p1grp->pg_token);
 608         LIST_INSERT_AFTER(p1, p2, p_pglist);
 609         lwkt_reltoken(&p1grp->pg_token);
 610
 611         /*
 612          * Attach the new process to its parent.
 613          *
 614          * If RFNOWAIT is set, the newly created process becomes a child
 615          * of the reaper (typically init).  This effectively disassociates
 616          * the child from the parent.
 617          *
 618          * Temporarily hold pptr for the RFNOWAIT case to avoid ripouts.
 619          */
 620         if (flags & RFNOWAIT) {
 621                 pptr = reaper_get(reap);
 622                 if (pptr == NULL) {
 623                         pptr = initproc;
 624                         PHOLD(pptr);
 625                 }
 626         } else {
 627                 pptr = p1;
 628         }
 629         p2->p_pptr = pptr;
 630         p2->p_ppid = pptr->p_pid;
 631         LIST_INIT(&p2->p_children);
 632
 633         lwkt_gettoken(&pptr->p_token);
 634         LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
 635         lwkt_reltoken(&pptr->p_token);
 636
 637         if (flags & RFNOWAIT)
 638                 PRELE(pptr);
 639
 640         varsymset_init(&p2->p_varsymset, &p1->p_varsymset);
 641         callout_init_mp(&p2->p_ithandle);
 642
 643 #ifdef KTRACE
 644         /*
 645          * Copy traceflag and tracefile if enabled.  If not inherited,
 646          * these were zeroed above but we still could have a trace race
 647          * so make sure p2's p_tracenode is NULL.
 648          */
 649         if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracenode == NULL) {
 650                 p2->p_traceflag = p1->p_traceflag;
 651                 p2->p_tracenode = ktrinherit(p1->p_tracenode);
 652         }
 653 #endif
 654
 655         /*
 656          * This begins the section where we must prevent the parent
 657          * from being swapped.
 658          *
 659          * Gets PRELE'd in the caller in start_forked_proc().
 660          */
 661         PHOLD(p1);
 662
 663         vm_fork(p1, p2, flags);
 664         if ((flags & RFMEM) == 0)
 665                 wake_umtx_threads(p1);
 666
 667         /*
 668          * Create the first lwp associated with the new proc.
 669          * It will return via a different execution path later, directly
 670          * into userland, after it was put on the runq by
 671          * start_forked_proc().
 672          */
 673         lwp_fork(lp1, p2, flags, NULL);
 674
 675         if (flags == (RFFDG | RFPROC | RFPGLOCK)) {
 676                 mycpu->gd_cnt.v_forks++;
 677                 mycpu->gd_cnt.v_forkpages += p2->p_vmspace->vm_dsize +
 678                                              p2->p_vmspace->vm_ssize;
 679         } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM | RFPGLOCK)) {
 680                 mycpu->gd_cnt.v_vforks++;
 681                 mycpu->gd_cnt.v_vforkpages += p2->p_vmspace->vm_dsize +
 682                                               p2->p_vmspace->vm_ssize;
 683         } else if (p1 == &proc0) {
 684                 mycpu->gd_cnt.v_kthreads++;
 685                 mycpu->gd_cnt.v_kthreadpages += p2->p_vmspace->vm_dsize +
 686                                                 p2->p_vmspace->vm_ssize;
 687         } else {
 688                 mycpu->gd_cnt.v_rforks++;
 689                 mycpu->gd_cnt.v_rforkpages += p2->p_vmspace->vm_dsize +
 690                                               p2->p_vmspace->vm_ssize;
 691         }
 692
 693         /*
 694          * Both processes are set up, now check if any loadable modules want
 695          * to adjust anything.
 696          *   What if they have an error? XXX
 697          */
 698         TAILQ_FOREACH(ep, &fork_list, next) {
 699                 (*ep->function)(p1, p2, flags);
 700         }
 701
 702         /*
 703          * Set the start time.  Note that the process is not runnable.  The
 704          * caller is responsible for making it runnable.
 705          */
 706         microtime(&p2->p_start);
 707         p2->p_acflag = AFORK;
 708
 709         /*
 710          * tell any interested parties about the new process
 711          */
 712         KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);
 713
 714         /*
 715          * Return child proc pointer to parent.
 716          */
 717         *procp = p2;
 718         error = 0;
 719 done:
 720         if (p2)
 721                 lwkt_reltoken(&p2->p_token);
 722         lwkt_reltoken(&p1->p_token);
 723         if (plkgrp) {
 724                 lockmgr(&plkgrp->pg_lock, LK_RELEASE);
 725                 pgrel(plkgrp);
 726         }
 727         return (error);
 728 }
 729
 730 static struct lwp *
 731 lwp_fork(struct lwp *origlp, struct proc *destproc, int flags,
 732     const cpumask_t *mask)
 733 {
 734         globaldata_t gd = mycpu;
 735         struct lwp *lp;
 736         struct thread *td;
 737
 738         lp = kmalloc(sizeof(struct lwp), M_LWP, M_WAITOK|M_ZERO);
 739
 740         lp->lwp_proc = destproc;
 741         lp->lwp_vmspace = destproc->p_vmspace;
 742         lp->lwp_stat = LSRUN;
 743         bcopy(&origlp->lwp_startcopy, &lp->lwp_startcopy,
 744             (unsigned) ((caddr_t)&lp->lwp_endcopy -
 745                         (caddr_t)&lp->lwp_startcopy));
 746         if (mask != NULL)
 747                 lp->lwp_cpumask = *mask;
 748
 749         /*
 750          * Reset the sigaltstack if memory is shared, otherwise inherit
 751          * it.
 752          */
 753         if (flags & RFMEM) {
 754                 lp->lwp_sigstk.ss_flags = SS_DISABLE;
 755                 lp->lwp_sigstk.ss_size = 0;
 756                 lp->lwp_sigstk.ss_sp = NULL;
 757                 lp->lwp_flags &= ~LWP_ALTSTACK;
 758         } else {
 759                 lp->lwp_flags |= origlp->lwp_flags & LWP_ALTSTACK;
 760         }
 761
 762         /*
 763          * Set cpbase to the last timeout that occured (not the upcoming
 764          * timeout).
 765          *
 766          * A critical section is required since a timer IPI can update
 767          * scheduler specific data.
 768          */
 769         crit_enter();
 770         lp->lwp_cpbase = gd->gd_schedclock.time - gd->gd_schedclock.periodic;
 771         destproc->p_usched->heuristic_forking(origlp, lp);
 772         crit_exit();
 773         CPUMASK_ANDMASK(lp->lwp_cpumask, usched_mastermask);
 774         lwkt_token_init(&lp->lwp_token, "lwp_token");
 775         spin_init(&lp->lwp_spin, "lwptoken");
 776
 777         /*
 778          * Assign the thread to the current cpu to begin with so we
 779          * can manipulate it.
 780          */
 781         td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, gd->gd_cpuid, 0);
 782         lp->lwp_thread = td;
 783         td->td_ucred = crhold(destproc->p_ucred);
 784         td->td_proc = destproc;
 785         td->td_lwp = lp;
 786         td->td_switch = cpu_heavy_switch;
 787 #ifdef NO_LWKT_SPLIT_USERPRI
 788         lwkt_setpri(td, TDPRI_USER_NORM);
 789 #else
 790         lwkt_setpri(td, TDPRI_KERN_USER);
 791 #endif
 792         lwkt_set_comm(td, "%s", destproc->p_comm);
 793
 794         /*
 795          * cpu_fork will copy and update the pcb, set up the kernel stack,
 796          * and make the child ready to run.
 797          */
 798         cpu_fork(origlp, lp, flags);
 799         kqueue_init(&lp->lwp_kqueue, destproc->p_fd);
 800
 801         /*
 802          * Assign a TID to the lp.  Loop until the insert succeeds (returns
 803          * NULL).
 804          *
 805          * If we are in a vfork assign the same TID as the lwp that did the
 806          * vfork().  This way if the user program messes around with
 807          * pthread calls inside the vfork(), it will operate like an
 808          * extension of the (blocked) parent.  Also note that since the
 809          * address space is being shared, insofar as pthreads is concerned,
 810          * the code running in the vfork() is part of the original process.
 811          */
 812         if (flags & RFPPWAIT) {
 813                 lp->lwp_tid = origlp->lwp_tid - 1;
 814         } else {
 815                 lp->lwp_tid = destproc->p_lasttid;
 816         }
 817
 818         do {
 819                 if (++lp->lwp_tid <= 0)
 820                         lp->lwp_tid = 1;
 821         } while (lwp_rb_tree_RB_INSERT(&destproc->p_lwp_tree, lp) != NULL);
 822
 823         destproc->p_lasttid = lp->lwp_tid;
 824         destproc->p_nthreads++;
 825
 826         /*
 827          * This flag is set and never cleared.  It means that the process
 828          * was threaded at some point.  Used to improve exit performance.
 829          */
 830         destproc->p_flags |= P_MAYBETHREADED;
 831
 832         return (lp);
 833 }
 834
 835 /*
 836  * The next two functionms are general routines to handle adding/deleting
 837  * items on the fork callout list.
 838  *
 839  * at_fork():
 840  * Take the arguments given and put them onto the fork callout list,
 841  * However first make sure that it's not already there.
 842  * Returns 0 on success or a standard error number.
 843  */
 844 int
 845 at_fork(forklist_fn function)
 846 {
 847         struct forklist *ep;
 848
 849 #ifdef INVARIANTS
 850         /* let the programmer know if he's been stupid */
 851         if (rm_at_fork(function)) {
 852                 kprintf("WARNING: fork callout entry (%p) already present\n",
 853                     function);
 854         }
 855 #endif
 856         ep = kmalloc(sizeof(*ep), M_ATFORK, M_WAITOK|M_ZERO);
 857         ep->function = function;
 858         TAILQ_INSERT_TAIL(&fork_list, ep, next);
 859         return (0);
 860 }
 861
 862 /*
 863  * Scan the exit callout list for the given item and remove it..
 864  * Returns the number of items removed (0 or 1)
 865  */
 866 int
 867 rm_at_fork(forklist_fn function)
 868 {
 869         struct forklist *ep;
 870
 871         TAILQ_FOREACH(ep, &fork_list, next) {
 872                 if (ep->function == function) {
 873                         TAILQ_REMOVE(&fork_list, ep, next);
 874                         kfree(ep, M_ATFORK);
 875                         return(1);
 876                 }
 877         }
 878         return (0);
 879 }
 880
 881 /*
 882  * Add a forked process to the run queue after any remaining setup, such
 883  * as setting the fork handler, has been completed.
 884  *
 885  * p2 is held by the caller.
 886  */
 887 void
 888 start_forked_proc(struct lwp *lp1, struct proc *p2)
 889 {
 890         struct lwp *lp2 = ONLY_LWP_IN_PROC(p2);
 891         int pflags;
 892
 893         /*
 894          * Move from SIDL to RUN queue, and activate the process's thread.
 895          * Activation of the thread effectively makes the process "a"
 896          * current process, so we do not setrunqueue().
 897          *
 898          * YYY setrunqueue works here but we should clean up the trampoline
 899          * code so we just schedule the LWKT thread and let the trampoline
 900          * deal with the userland scheduler on return to userland.
 901          */
 902         KASSERT(p2->p_stat == SIDL,
 903             ("cannot start forked process, bad status: %p", p2));
 904         p2->p_usched->resetpriority(lp2);
 905         crit_enter();
 906         p2->p_stat = SACTIVE;
 907         lp2->lwp_stat = LSRUN;
 908         p2->p_usched->setrunqueue(lp2);
 909         crit_exit();
 910
 911         /*
 912          * Now can be swapped.
 913          */
 914         PRELE(lp1->lwp_proc);
 915
 916         /*
 917          * Preserve synchronization semantics of vfork.  P_PPWAIT is set in
 918          * the child until it has retired the parent's resources.  The parent
 919          * must wait for the flag to be cleared by the child.
 920          *
 921          * Interlock the flag/tsleep with atomic ops to avoid unnecessary
 922          * p_token conflicts.
 923          *
 924          * XXX Is this use of an atomic op on a field that is not normally
 925          *     manipulated with atomic ops ok?
 926          */
 927         while ((pflags = p2->p_flags) & P_PPWAIT) {
 928                 cpu_ccfence();
 929                 tsleep_interlock(lp1->lwp_proc, 0);
 930                 if (atomic_cmpset_int(&p2->p_flags, pflags, pflags))
 931                         tsleep(lp1->lwp_proc, PINTERLOCKED, "ppwait", 0);
 932         }
 933 }
 934
 935 /*
 936  * procctl (idtype_t idtype, id_t id, int cmd, void *arg)
 937  */
 938 int
 939 sys_procctl(struct procctl_args *uap)
 940 {
 941         struct proc *p = curproc;
 942         struct proc *p2;
 943         struct sysreaper *reap;
 944         union reaper_info udata;
 945         int error;
 946
 947         if (uap->idtype != P_PID || uap->id != (id_t)p->p_pid)
 948                 return EINVAL;
 949
 950         switch(uap->cmd) {
 951         case PROC_REAP_ACQUIRE:
 952                 lwkt_gettoken(&p->p_token);
 953                 reap = kmalloc(sizeof(*reap), M_REAPER, M_WAITOK|M_ZERO);
 954                 if (p->p_reaper == NULL || p->p_reaper->p != p) {
 955                         reaper_init(p, reap);
 956                         error = 0;
 957                 } else {
 958                         kfree(reap, M_REAPER);
 959                         error = EALREADY;
 960                 }
 961                 lwkt_reltoken(&p->p_token);
 962                 break;
 963         case PROC_REAP_RELEASE:
 964                 lwkt_gettoken(&p->p_token);
 965 release_again:
 966                 reap = p->p_reaper;
 967                 KKASSERT(reap != NULL);
 968                 if (reap->p == p) {
 969                         reaper_hold(reap);      /* in case of thread race */
 970                         lockmgr(&reap->lock, LK_EXCLUSIVE);
 971                         if (reap->p != p) {
 972                                 lockmgr(&reap->lock, LK_RELEASE);
 973                                 reaper_drop(reap);
 974                                 goto release_again;
 975                         }
 976                         reap->p = NULL;
 977                         p->p_reaper = reap->parent;
 978                         if (p->p_reaper)
 979                                 reaper_hold(p->p_reaper);
 980                         lockmgr(&reap->lock, LK_RELEASE);
 981                         reaper_drop(reap);      /* our ref */
 982                         reaper_drop(reap);      /* old p_reaper ref */
 983                         error = 0;
 984                 } else {
 985                         error = ENOTCONN;
 986                 }
 987                 lwkt_reltoken(&p->p_token);
 988                 break;
 989         case PROC_REAP_STATUS:
 990                 bzero(&udata, sizeof(udata));
 991                 lwkt_gettoken_shared(&p->p_token);
 992                 if ((reap = p->p_reaper) != NULL && reap->p == p) {
 993                         udata.status.flags = reap->flags;
 994                         udata.status.refs = reap->refs - 1; /* minus ours */
 995                 }
 996                 p2 = LIST_FIRST(&p->p_children);
 997                 udata.status.pid_head = p2 ? p2->p_pid : -1;
 998                 lwkt_reltoken(&p->p_token);
 999
1000                 if (uap->data) {
1001                         error = copyout(&udata, uap->data,
1002                                         sizeof(udata.status));
1003                 } else {
1004                         error = 0;
1005                 }
1006                 break;
1007         default:
1008                 error = EINVAL;
1009                 break;
1010         }
1011         return error;
1012 }
1013
1014 /*
1015  * Bump ref on reaper, preventing destruction
1016  */
1017 void
1018 reaper_hold(struct sysreaper *reap)
1019 {
1020         KKASSERT(reap->refs > 0);
1021         refcount_acquire(&reap->refs);
1022 }
1023
1024 /*
1025  * Drop ref on reaper, destroy the structure on the 1->0
1026  * transition and loop on the parent.
1027  */
1028 void
1029 reaper_drop(struct sysreaper *next)
1030 {
1031         struct sysreaper *reap;
1032
1033         while ((reap = next) != NULL) {
1034                 if (refcount_release(&reap->refs)) {
1035                         next = reap->parent;
1036                         KKASSERT(reap->p == NULL);
1037                         lockmgr(&reaper_lock, LK_EXCLUSIVE);
1038                         reap->parent = NULL;
1039                         kfree(reap, M_REAPER);
1040                         lockmgr(&reaper_lock, LK_RELEASE);
1041                 } else {
1042                         next = NULL;
1043                 }
1044         }
1045 }
1046
1047 /*
1048  * Initialize a static or newly allocated reaper structure
1049  */
1050 void
1051 reaper_init(struct proc *p, struct sysreaper *reap)
1052 {
1053         reap->parent = p->p_reaper;
1054         reap->p = p;
1055         if (p == initproc) {
1056                 reap->flags = REAPER_STAT_OWNED | REAPER_STAT_REALINIT;
1057                 reap->refs = 2;
1058         } else {
1059                 reap->flags = REAPER_STAT_OWNED;
1060                 reap->refs = 1;
1061         }
1062         lockinit(&reap->lock, "subrp", 0, 0);
1063         cpu_sfence();
1064         p->p_reaper = reap;
1065 }
1066
1067 /*
1068  * Called with p->p_token held during exit.
1069  *
1070  * This is a bit simpler than RELEASE because there are no threads remaining
1071  * to race.  We only release if we own the reaper, the exit code will handle
1072  * the final p_reaper release.
1073  */
1074 struct sysreaper *
1075 reaper_exit(struct proc *p)
1076 {
1077         struct sysreaper *reap;
1078
1079         /*
1080          * Release acquired reaper
1081          */
1082         if ((reap = p->p_reaper) != NULL && reap->p == p) {
1083                 lockmgr(&reap->lock, LK_EXCLUSIVE);
1084                 p->p_reaper = reap->parent;
1085                 if (p->p_reaper)
1086                         reaper_hold(p->p_reaper);
1087                 reap->p = NULL;
1088                 lockmgr(&reap->lock, LK_RELEASE);
1089                 reaper_drop(reap);
1090         }
1091
1092         /*
1093          * Return and clear reaper (caller is holding p_token for us)
1094          * (reap->p does not equal p).  Caller must drop it.
1095          */
1096         if ((reap = p->p_reaper) != NULL) {
1097                 p->p_reaper = NULL;
1098         }
1099         return reap;
1100 }
1101
1102 /*
1103  * Return a held (PHOLD) process representing the reaper for process (p).
1104  * NULL should not normally be returned.  Caller should PRELE() the returned
1105  * reaper process when finished.
1106  *
1107  * Remove dead internal nodes while we are at it.
1108  *
1109  * Process (p)'s token must be held on call.
1110  * The returned process's token is NOT acquired by this routine.
1111  */
1112 struct proc *
1113 reaper_get(struct sysreaper *reap)
1114 {
1115         struct sysreaper *next;
1116         struct proc *reproc;
1117
1118         if (reap == NULL)
1119                 return NULL;
1120
1121         /*
1122          * Extra hold for loop
1123          */
1124         reaper_hold(reap);
1125
1126         while (reap) {
1127                 lockmgr(&reap->lock, LK_SHARED);
1128                 if (reap->p) {
1129                         /*
1130                          * Probable reaper
1131                          */
1132                         if (reap->p) {
1133                                 reproc = reap->p;
1134                                 PHOLD(reproc);
1135                                 lockmgr(&reap->lock, LK_RELEASE);
1136                                 reaper_drop(reap);
1137                                 return reproc;
1138                         }
1139
1140                         /*
1141                          * Raced, try again
1142                          */
1143                         lockmgr(&reap->lock, LK_RELEASE);
1144                         continue;
1145                 }
1146
1147                 /*
1148                  * Traverse upwards in the reaper topology, destroy
1149                  * dead internal nodes when possible.
1150                  *
1151                  * NOTE: Our ref on next means that a dead node should
1152                  *       have 2 (ours and reap->parent's).
1153                  */
1154                 next = reap->parent;
1155                 while (next) {
1156                         reaper_hold(next);
1157                         if (next->refs == 2 && next->p == NULL) {
1158                                 lockmgr(&reap->lock, LK_RELEASE);
1159                                 lockmgr(&reap->lock, LK_EXCLUSIVE);
1160                                 if (next->refs == 2 &&
1161                                     reap->parent == next &&
1162                                     next->p == NULL) {
1163                                         /*
1164                                          * reap->parent inherits ref from next.
1165                                          */
1166                                         reap->parent = next->parent;
1167                                         next->parent = NULL;
1168                                         reaper_drop(next);      /* ours */
1169                                         reaper_drop(next);      /* old parent */
1170                                         next = reap->parent;
1171                                         continue;       /* possible chain */
1172                                 }
1173                         }
1174                         break;
1175                 }
1176                 lockmgr(&reap->lock, LK_RELEASE);
1177                 reaper_drop(reap);
1178                 reap = next;
1179         }
1180         return NULL;
1181 }
1182
1183 /*
1184  * Test that the sender is allowed to send a signal to the target.
1185  * The sender process is assumed to have a stable reaper.  The
1186  * target can be e.g. from a scan callback.
1187  *
1188  * Target cannot be the reaper process itself unless reaper_ok is specified,
1189  * or sender == target.
1190  */
1191 int
1192 reaper_sigtest(struct proc *sender, struct proc *target, int reaper_ok)
1193 {
1194         struct sysreaper *sreap;
1195         struct sysreaper *reap;
1196         int r;
1197
1198         sreap = sender->p_reaper;
1199         if (sreap == NULL)
1200                 return 1;
1201
1202         if (sreap == target->p_reaper) {
1203                 if (sreap->p == target && sreap->p != sender && reaper_ok == 0)
1204                         return 0;
1205                 return 1;
1206         }
1207         lockmgr(&reaper_lock, LK_SHARED);
1208         r = 0;
1209         for (reap = target->p_reaper; reap; reap = reap->parent) {
1210                 if (sreap == reap) {
1211                         if (sreap->p != target || reaper_ok)
1212                                 r = 1;
1213                         break;
1214                 }
1215         }
1216         lockmgr(&reaper_lock, LK_RELEASE);
1217
1218         return r;
1219 }