The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c

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    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  * 4. 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  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: releng/10.2/sys/kern/kern_fork.c 284343 2015-06-13 16:15:43Z jhb $");
   39 
   40 #include "opt_kdtrace.h"
   41 #include "opt_ktrace.h"
   42 #include "opt_kstack_pages.h"
   43 #include "opt_procdesc.h"
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/sysproto.h>
   48 #include <sys/eventhandler.h>
   49 #include <sys/fcntl.h>
   50 #include <sys/filedesc.h>
   51 #include <sys/jail.h>
   52 #include <sys/kernel.h>
   53 #include <sys/kthread.h>
   54 #include <sys/sysctl.h>
   55 #include <sys/lock.h>
   56 #include <sys/malloc.h>
   57 #include <sys/mutex.h>
   58 #include <sys/priv.h>
   59 #include <sys/proc.h>
   60 #include <sys/procdesc.h>
   61 #include <sys/pioctl.h>
   62 #include <sys/racct.h>
   63 #include <sys/resourcevar.h>
   64 #include <sys/sched.h>
   65 #include <sys/syscall.h>
   66 #include <sys/vmmeter.h>
   67 #include <sys/vnode.h>
   68 #include <sys/acct.h>
   69 #include <sys/ktr.h>
   70 #include <sys/ktrace.h>
   71 #include <sys/unistd.h> 
   72 #include <sys/sdt.h>
   73 #include <sys/sx.h>
   74 #include <sys/sysent.h>
   75 #include <sys/signalvar.h>
   76 
   77 #include <security/audit/audit.h>
   78 #include <security/mac/mac_framework.h>
   79 
   80 #include <vm/vm.h>
   81 #include <vm/pmap.h>
   82 #include <vm/vm_map.h>
   83 #include <vm/vm_extern.h>
   84 #include <vm/uma.h>
   85 
   86 #ifdef KDTRACE_HOOKS
   87 #include <sys/dtrace_bsd.h>
   88 dtrace_fork_func_t      dtrace_fasttrap_fork;
   89 #endif
   90 
   91 SDT_PROVIDER_DECLARE(proc);
   92 SDT_PROBE_DEFINE3(proc, kernel, , create, "struct proc *",
   93     "struct proc *", "int");
   94 
   95 #ifndef _SYS_SYSPROTO_H_
   96 struct fork_args {
   97         int     dummy;
   98 };
   99 #endif
  100 
  101 /* ARGSUSED */
  102 int
  103 sys_fork(struct thread *td, struct fork_args *uap)
  104 {
  105         int error;
  106         struct proc *p2;
  107 
  108         error = fork1(td, RFFDG | RFPROC, 0, &p2, NULL, 0);
  109         if (error == 0) {
  110                 td->td_retval[0] = p2->p_pid;
  111                 td->td_retval[1] = 0;
  112         }
  113         return (error);
  114 }
  115 
  116 /* ARGUSED */
  117 int
  118 sys_pdfork(td, uap)
  119         struct thread *td;
  120         struct pdfork_args *uap;
  121 {
  122 #ifdef PROCDESC
  123         int error, fd;
  124         struct proc *p2;
  125 
  126         /*
  127          * It is necessary to return fd by reference because 0 is a valid file
  128          * descriptor number, and the child needs to be able to distinguish
  129          * itself from the parent using the return value.
  130          */
  131         error = fork1(td, RFFDG | RFPROC | RFPROCDESC, 0, &p2,
  132             &fd, uap->flags);
  133         if (error == 0) {
  134                 td->td_retval[0] = p2->p_pid;
  135                 td->td_retval[1] = 0;
  136                 error = copyout(&fd, uap->fdp, sizeof(fd));
  137         }
  138         return (error);
  139 #else
  140         return (ENOSYS);
  141 #endif
  142 }
  143 
  144 /* ARGSUSED */
  145 int
  146 sys_vfork(struct thread *td, struct vfork_args *uap)
  147 {
  148         int error, flags;
  149         struct proc *p2;
  150 
  151         flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
  152         error = fork1(td, flags, 0, &p2, NULL, 0);
  153         if (error == 0) {
  154                 td->td_retval[0] = p2->p_pid;
  155                 td->td_retval[1] = 0;
  156         }
  157         return (error);
  158 }
  159 
  160 int
  161 sys_rfork(struct thread *td, struct rfork_args *uap)
  162 {
  163         struct proc *p2;
  164         int error;
  165 
  166         /* Don't allow kernel-only flags. */
  167         if ((uap->flags & RFKERNELONLY) != 0)
  168                 return (EINVAL);
  169 
  170         AUDIT_ARG_FFLAGS(uap->flags);
  171         error = fork1(td, uap->flags, 0, &p2, NULL, 0);
  172         if (error == 0) {
  173                 td->td_retval[0] = p2 ? p2->p_pid : 0;
  174                 td->td_retval[1] = 0;
  175         }
  176         return (error);
  177 }
  178 
  179 int     nprocs = 1;             /* process 0 */
  180 int     lastpid = 0;
  181 SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0, 
  182     "Last used PID");
  183 
  184 /*
  185  * Random component to lastpid generation.  We mix in a random factor to make
  186  * it a little harder to predict.  We sanity check the modulus value to avoid
  187  * doing it in critical paths.  Don't let it be too small or we pointlessly
  188  * waste randomness entropy, and don't let it be impossibly large.  Using a
  189  * modulus that is too big causes a LOT more process table scans and slows
  190  * down fork processing as the pidchecked caching is defeated.
  191  */
  192 static int randompid = 0;
  193 
  194 static int
  195 sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
  196 {
  197         int error, pid;
  198 
  199         error = sysctl_wire_old_buffer(req, sizeof(int));
  200         if (error != 0)
  201                 return(error);
  202         sx_xlock(&allproc_lock);
  203         pid = randompid;
  204         error = sysctl_handle_int(oidp, &pid, 0, req);
  205         if (error == 0 && req->newptr != NULL) {
  206                 if (pid < 0 || pid > pid_max - 100)     /* out of range */
  207                         pid = pid_max - 100;
  208                 else if (pid < 2)                       /* NOP */
  209                         pid = 0;
  210                 else if (pid < 100)                     /* Make it reasonable */
  211                         pid = 100;
  212                 randompid = pid;
  213         }
  214         sx_xunlock(&allproc_lock);
  215         return (error);
  216 }
  217 
  218 SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
  219     0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
  220 
  221 static int
  222 fork_findpid(int flags)
  223 {
  224         struct proc *p;
  225         int trypid;
  226         static int pidchecked = 0;
  227 
  228         /*
  229          * Requires allproc_lock in order to iterate over the list
  230          * of processes, and proctree_lock to access p_pgrp.
  231          */
  232         sx_assert(&allproc_lock, SX_LOCKED);
  233         sx_assert(&proctree_lock, SX_LOCKED);
  234 
  235         /*
  236          * Find an unused process ID.  We remember a range of unused IDs
  237          * ready to use (from lastpid+1 through pidchecked-1).
  238          *
  239          * If RFHIGHPID is set (used during system boot), do not allocate
  240          * low-numbered pids.
  241          */
  242         trypid = lastpid + 1;
  243         if (flags & RFHIGHPID) {
  244                 if (trypid < 10)
  245                         trypid = 10;
  246         } else {
  247                 if (randompid)
  248                         trypid += arc4random() % randompid;
  249         }
  250 retry:
  251         /*
  252          * If the process ID prototype has wrapped around,
  253          * restart somewhat above 0, as the low-numbered procs
  254          * tend to include daemons that don't exit.
  255          */
  256         if (trypid >= pid_max) {
  257                 trypid = trypid % pid_max;
  258                 if (trypid < 100)
  259                         trypid += 100;
  260                 pidchecked = 0;
  261         }
  262         if (trypid >= pidchecked) {
  263                 int doingzomb = 0;
  264 
  265                 pidchecked = PID_MAX;
  266                 /*
  267                  * Scan the active and zombie procs to check whether this pid
  268                  * is in use.  Remember the lowest pid that's greater
  269                  * than trypid, so we can avoid checking for a while.
  270                  *
  271                  * Avoid reuse of the process group id, session id or
  272                  * the reaper subtree id.  Note that for process group
  273                  * and sessions, the amount of reserved pids is
  274                  * limited by process limit.  For the subtree ids, the
  275                  * id is kept reserved only while there is a
  276                  * non-reaped process in the subtree, so amount of
  277                  * reserved pids is limited by process limit times
  278                  * two.
  279                  */
  280                 p = LIST_FIRST(&allproc);
  281 again:
  282                 for (; p != NULL; p = LIST_NEXT(p, p_list)) {
  283                         while (p->p_pid == trypid ||
  284                             p->p_reapsubtree == trypid ||
  285                             (p->p_pgrp != NULL &&
  286                             (p->p_pgrp->pg_id == trypid ||
  287                             (p->p_session != NULL &&
  288                             p->p_session->s_sid == trypid)))) {
  289                                 trypid++;
  290                                 if (trypid >= pidchecked)
  291                                         goto retry;
  292                         }
  293                         if (p->p_pid > trypid && pidchecked > p->p_pid)
  294                                 pidchecked = p->p_pid;
  295                         if (p->p_pgrp != NULL) {
  296                                 if (p->p_pgrp->pg_id > trypid &&
  297                                     pidchecked > p->p_pgrp->pg_id)
  298                                         pidchecked = p->p_pgrp->pg_id;
  299                                 if (p->p_session != NULL &&
  300                                     p->p_session->s_sid > trypid &&
  301                                     pidchecked > p->p_session->s_sid)
  302                                         pidchecked = p->p_session->s_sid;
  303                         }
  304                 }
  305                 if (!doingzomb) {
  306                         doingzomb = 1;
  307                         p = LIST_FIRST(&zombproc);
  308                         goto again;
  309                 }
  310         }
  311 
  312         /*
  313          * RFHIGHPID does not mess with the lastpid counter during boot.
  314          */
  315         if (flags & RFHIGHPID)
  316                 pidchecked = 0;
  317         else
  318                 lastpid = trypid;
  319 
  320         return (trypid);
  321 }
  322 
  323 static int
  324 fork_norfproc(struct thread *td, int flags)
  325 {
  326         int error;
  327         struct proc *p1;
  328 
  329         KASSERT((flags & RFPROC) == 0,
  330             ("fork_norfproc called with RFPROC set"));
  331         p1 = td->td_proc;
  332 
  333         if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
  334             (flags & (RFCFDG | RFFDG))) {
  335                 PROC_LOCK(p1);
  336                 if (thread_single(p1, SINGLE_BOUNDARY)) {
  337                         PROC_UNLOCK(p1);
  338                         return (ERESTART);
  339                 }
  340                 PROC_UNLOCK(p1);
  341         }
  342 
  343         error = vm_forkproc(td, NULL, NULL, NULL, flags);
  344         if (error)
  345                 goto fail;
  346 
  347         /*
  348          * Close all file descriptors.
  349          */
  350         if (flags & RFCFDG) {
  351                 struct filedesc *fdtmp;
  352                 fdtmp = fdinit(td->td_proc->p_fd);
  353                 fdescfree(td);
  354                 p1->p_fd = fdtmp;
  355         }
  356 
  357         /*
  358          * Unshare file descriptors (from parent).
  359          */
  360         if (flags & RFFDG)
  361                 fdunshare(td);
  362 
  363 fail:
  364         if (((p1->p_flag & (P_HADTHREADS|P_SYSTEM)) == P_HADTHREADS) &&
  365             (flags & (RFCFDG | RFFDG))) {
  366                 PROC_LOCK(p1);
  367                 thread_single_end(p1, SINGLE_BOUNDARY);
  368                 PROC_UNLOCK(p1);
  369         }
  370         return (error);
  371 }
  372 
  373 static void
  374 do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
  375     struct vmspace *vm2, int pdflags)
  376 {
  377         struct proc *p1, *pptr;
  378         int p2_held, trypid;
  379         struct filedesc *fd;
  380         struct filedesc_to_leader *fdtol;
  381         struct sigacts *newsigacts;
  382 
  383         sx_assert(&proctree_lock, SX_SLOCKED);
  384         sx_assert(&allproc_lock, SX_XLOCKED);
  385 
  386         p2_held = 0;
  387         p1 = td->td_proc;
  388 
  389         /*
  390          * Increment the nprocs resource before blocking can occur.  There
  391          * are hard-limits as to the number of processes that can run.
  392          */
  393         nprocs++;
  394 
  395         trypid = fork_findpid(flags);
  396 
  397         sx_sunlock(&proctree_lock);
  398 
  399         p2->p_state = PRS_NEW;          /* protect against others */
  400         p2->p_pid = trypid;
  401         AUDIT_ARG_PID(p2->p_pid);
  402         LIST_INSERT_HEAD(&allproc, p2, p_list);
  403         allproc_gen++;
  404         LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
  405         tidhash_add(td2);
  406         PROC_LOCK(p2);
  407         PROC_LOCK(p1);
  408 
  409         sx_xunlock(&allproc_lock);
  410 
  411         bcopy(&p1->p_startcopy, &p2->p_startcopy,
  412             __rangeof(struct proc, p_startcopy, p_endcopy));
  413         pargs_hold(p2->p_args);
  414         PROC_UNLOCK(p1);
  415 
  416         bzero(&p2->p_startzero,
  417             __rangeof(struct proc, p_startzero, p_endzero));
  418         p2->p_treeflag = 0;
  419 
  420         p2->p_ucred = crhold(td->td_ucred);
  421 
  422         /* Tell the prison that we exist. */
  423         prison_proc_hold(p2->p_ucred->cr_prison);
  424 
  425         PROC_UNLOCK(p2);
  426 
  427         /*
  428          * Malloc things while we don't hold any locks.
  429          */
  430         if (flags & RFSIGSHARE)
  431                 newsigacts = NULL;
  432         else
  433                 newsigacts = sigacts_alloc();
  434 
  435         /*
  436          * Copy filedesc.
  437          */
  438         if (flags & RFCFDG) {
  439                 fd = fdinit(p1->p_fd);
  440                 fdtol = NULL;
  441         } else if (flags & RFFDG) {
  442                 fd = fdcopy(p1->p_fd);
  443                 fdtol = NULL;
  444         } else {
  445                 fd = fdshare(p1->p_fd);
  446                 if (p1->p_fdtol == NULL)
  447                         p1->p_fdtol = filedesc_to_leader_alloc(NULL, NULL,
  448                             p1->p_leader);
  449                 if ((flags & RFTHREAD) != 0) {
  450                         /*
  451                          * Shared file descriptor table, and shared
  452                          * process leaders.
  453                          */
  454                         fdtol = p1->p_fdtol;
  455                         FILEDESC_XLOCK(p1->p_fd);
  456                         fdtol->fdl_refcount++;
  457                         FILEDESC_XUNLOCK(p1->p_fd);
  458                 } else {
  459                         /* 
  460                          * Shared file descriptor table, and different
  461                          * process leaders.
  462                          */
  463                         fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
  464                             p1->p_fd, p2);
  465                 }
  466         }
  467         /*
  468          * Make a proc table entry for the new process.
  469          * Start by zeroing the section of proc that is zero-initialized,
  470          * then copy the section that is copied directly from the parent.
  471          */
  472 
  473         PROC_LOCK(p2);
  474         PROC_LOCK(p1);
  475 
  476         bzero(&td2->td_startzero,
  477             __rangeof(struct thread, td_startzero, td_endzero));
  478         td2->td_su = NULL;
  479 
  480         bcopy(&td->td_startcopy, &td2->td_startcopy,
  481             __rangeof(struct thread, td_startcopy, td_endcopy));
  482 
  483         bcopy(&p2->p_comm, &td2->td_name, sizeof(td2->td_name));
  484         td2->td_sigstk = td->td_sigstk;
  485         td2->td_flags = TDF_INMEM;
  486         td2->td_lend_user_pri = PRI_MAX;
  487 
  488 #ifdef VIMAGE
  489         td2->td_vnet = NULL;
  490         td2->td_vnet_lpush = NULL;
  491 #endif
  492 
  493         /*
  494          * Allow the scheduler to initialize the child.
  495          */
  496         thread_lock(td);
  497         sched_fork(td, td2);
  498         thread_unlock(td);
  499 
  500         /*
  501          * Duplicate sub-structures as needed.
  502          * Increase reference counts on shared objects.
  503          */
  504         p2->p_flag = P_INMEM;
  505         p2->p_flag2 = p1->p_flag2 & (P2_NOTRACE | P2_NOTRACE_EXEC);
  506         p2->p_swtick = ticks;
  507         if (p1->p_flag & P_PROFIL)
  508                 startprofclock(p2);
  509         td2->td_ucred = crhold(p2->p_ucred);
  510 
  511         if (flags & RFSIGSHARE) {
  512                 p2->p_sigacts = sigacts_hold(p1->p_sigacts);
  513         } else {
  514                 sigacts_copy(newsigacts, p1->p_sigacts);
  515                 p2->p_sigacts = newsigacts;
  516         }
  517 
  518         if (flags & RFTSIGZMB)
  519                 p2->p_sigparent = RFTSIGNUM(flags);
  520         else if (flags & RFLINUXTHPN)
  521                 p2->p_sigparent = SIGUSR1;
  522         else
  523                 p2->p_sigparent = SIGCHLD;
  524 
  525         p2->p_textvp = p1->p_textvp;
  526         p2->p_fd = fd;
  527         p2->p_fdtol = fdtol;
  528 
  529         if (p1->p_flag2 & P2_INHERIT_PROTECTED) {
  530                 p2->p_flag |= P_PROTECTED;
  531                 p2->p_flag2 |= P2_INHERIT_PROTECTED;
  532         }
  533 
  534         /*
  535          * p_limit is copy-on-write.  Bump its refcount.
  536          */
  537         lim_fork(p1, p2);
  538 
  539         pstats_fork(p1->p_stats, p2->p_stats);
  540 
  541         PROC_UNLOCK(p1);
  542         PROC_UNLOCK(p2);
  543 
  544         /* Bump references to the text vnode (for procfs). */
  545         if (p2->p_textvp)
  546                 vref(p2->p_textvp);
  547 
  548         /*
  549          * Set up linkage for kernel based threading.
  550          */
  551         if ((flags & RFTHREAD) != 0) {
  552                 mtx_lock(&ppeers_lock);
  553                 p2->p_peers = p1->p_peers;
  554                 p1->p_peers = p2;
  555                 p2->p_leader = p1->p_leader;
  556                 mtx_unlock(&ppeers_lock);
  557                 PROC_LOCK(p1->p_leader);
  558                 if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
  559                         PROC_UNLOCK(p1->p_leader);
  560                         /*
  561                          * The task leader is exiting, so process p1 is
  562                          * going to be killed shortly.  Since p1 obviously
  563                          * isn't dead yet, we know that the leader is either
  564                          * sending SIGKILL's to all the processes in this
  565                          * task or is sleeping waiting for all the peers to
  566                          * exit.  We let p1 complete the fork, but we need
  567                          * to go ahead and kill the new process p2 since
  568                          * the task leader may not get a chance to send
  569                          * SIGKILL to it.  We leave it on the list so that
  570                          * the task leader will wait for this new process
  571                          * to commit suicide.
  572                          */
  573                         PROC_LOCK(p2);
  574                         kern_psignal(p2, SIGKILL);
  575                         PROC_UNLOCK(p2);
  576                 } else
  577                         PROC_UNLOCK(p1->p_leader);
  578         } else {
  579                 p2->p_peers = NULL;
  580                 p2->p_leader = p2;
  581         }
  582 
  583         sx_xlock(&proctree_lock);
  584         PGRP_LOCK(p1->p_pgrp);
  585         PROC_LOCK(p2);
  586         PROC_LOCK(p1);
  587 
  588         /*
  589          * Preserve some more flags in subprocess.  P_PROFIL has already
  590          * been preserved.
  591          */
  592         p2->p_flag |= p1->p_flag & P_SUGID;
  593         td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
  594         SESS_LOCK(p1->p_session);
  595         if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
  596                 p2->p_flag |= P_CONTROLT;
  597         SESS_UNLOCK(p1->p_session);
  598         if (flags & RFPPWAIT)
  599                 p2->p_flag |= P_PPWAIT;
  600 
  601         p2->p_pgrp = p1->p_pgrp;
  602         LIST_INSERT_AFTER(p1, p2, p_pglist);
  603         PGRP_UNLOCK(p1->p_pgrp);
  604         LIST_INIT(&p2->p_children);
  605         LIST_INIT(&p2->p_orphans);
  606 
  607         callout_init_mtx(&p2->p_itcallout, &p2->p_mtx, 0);
  608 
  609         /*
  610          * If PF_FORK is set, the child process inherits the
  611          * procfs ioctl flags from its parent.
  612          */
  613         if (p1->p_pfsflags & PF_FORK) {
  614                 p2->p_stops = p1->p_stops;
  615                 p2->p_pfsflags = p1->p_pfsflags;
  616         }
  617 
  618         /*
  619          * This begins the section where we must prevent the parent
  620          * from being swapped.
  621          */
  622         _PHOLD(p1);
  623         PROC_UNLOCK(p1);
  624 
  625         /*
  626          * Attach the new process to its parent.
  627          *
  628          * If RFNOWAIT is set, the newly created process becomes a child
  629          * of init.  This effectively disassociates the child from the
  630          * parent.
  631          */
  632         if ((flags & RFNOWAIT) != 0) {
  633                 pptr = p1->p_reaper;
  634                 p2->p_reaper = pptr;
  635         } else {
  636                 p2->p_reaper = (p1->p_treeflag & P_TREE_REAPER) != 0 ?
  637                     p1 : p1->p_reaper;
  638                 pptr = p1;
  639         }
  640         p2->p_pptr = pptr;
  641         LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
  642         LIST_INIT(&p2->p_reaplist);
  643         LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
  644         if (p2->p_reaper == p1)
  645                 p2->p_reapsubtree = p2->p_pid;
  646         else
  647                 p2->p_reapsubtree = p1->p_reapsubtree;          
  648         sx_xunlock(&proctree_lock);
  649 
  650         /* Inform accounting that we have forked. */
  651         p2->p_acflag = AFORK;
  652         PROC_UNLOCK(p2);
  653 
  654 #ifdef KTRACE
  655         ktrprocfork(p1, p2);
  656 #endif
  657 
  658         /*
  659          * Finish creating the child process.  It will return via a different
  660          * execution path later.  (ie: directly into user mode)
  661          */
  662         vm_forkproc(td, p2, td2, vm2, flags);
  663 
  664         if (flags == (RFFDG | RFPROC)) {
  665                 PCPU_INC(cnt.v_forks);
  666                 PCPU_ADD(cnt.v_forkpages, p2->p_vmspace->vm_dsize +
  667                     p2->p_vmspace->vm_ssize);
  668         } else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
  669                 PCPU_INC(cnt.v_vforks);
  670                 PCPU_ADD(cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
  671                     p2->p_vmspace->vm_ssize);
  672         } else if (p1 == &proc0) {
  673                 PCPU_INC(cnt.v_kthreads);
  674                 PCPU_ADD(cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
  675                     p2->p_vmspace->vm_ssize);
  676         } else {
  677                 PCPU_INC(cnt.v_rforks);
  678                 PCPU_ADD(cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
  679                     p2->p_vmspace->vm_ssize);
  680         }
  681 
  682 #ifdef PROCDESC
  683         /*
  684          * Associate the process descriptor with the process before anything
  685          * can happen that might cause that process to need the descriptor.
  686          * However, don't do this until after fork(2) can no longer fail.
  687          */
  688         if (flags & RFPROCDESC)
  689                 procdesc_new(p2, pdflags);
  690 #endif
  691 
  692         /*
  693          * Both processes are set up, now check if any loadable modules want
  694          * to adjust anything.
  695          */
  696         EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
  697 
  698         /*
  699          * Set the child start time and mark the process as being complete.
  700          */
  701         PROC_LOCK(p2);
  702         PROC_LOCK(p1);
  703         microuptime(&p2->p_stats->p_start);
  704         PROC_SLOCK(p2);
  705         p2->p_state = PRS_NORMAL;
  706         PROC_SUNLOCK(p2);
  707 
  708 #ifdef KDTRACE_HOOKS
  709         /*
  710          * Tell the DTrace fasttrap provider about the new process so that any
  711          * tracepoints inherited from the parent can be removed. We have to do
  712          * this only after p_state is PRS_NORMAL since the fasttrap module will
  713          * use pfind() later on.
  714          */
  715         if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
  716                 dtrace_fasttrap_fork(p1, p2);
  717 #endif
  718         if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
  719             P_FOLLOWFORK)) {
  720                 /*
  721                  * Arrange for debugger to receive the fork event.
  722                  *
  723                  * We can report PL_FLAG_FORKED regardless of
  724                  * P_FOLLOWFORK settings, but it does not make a sense
  725                  * for runaway child.
  726                  */
  727                 td->td_dbgflags |= TDB_FORK;
  728                 td->td_dbg_forked = p2->p_pid;
  729                 td2->td_dbgflags |= TDB_STOPATFORK;
  730                 _PHOLD(p2);
  731                 p2_held = 1;
  732         }
  733         if (flags & RFPPWAIT) {
  734                 td->td_pflags |= TDP_RFPPWAIT;
  735                 td->td_rfppwait_p = p2;
  736         }
  737         PROC_UNLOCK(p2);
  738         if ((flags & RFSTOPPED) == 0) {
  739                 /*
  740                  * If RFSTOPPED not requested, make child runnable and
  741                  * add to run queue.
  742                  */
  743                 thread_lock(td2);
  744                 TD_SET_CAN_RUN(td2);
  745                 sched_add(td2, SRQ_BORING);
  746                 thread_unlock(td2);
  747         }
  748 
  749         /*
  750          * Now can be swapped.
  751          */
  752         _PRELE(p1);
  753         PROC_UNLOCK(p1);
  754 
  755         /*
  756          * Tell any interested parties about the new process.
  757          */
  758         knote_fork(&p1->p_klist, p2->p_pid);
  759         SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0);
  760 
  761         /*
  762          * Wait until debugger is attached to child.
  763          */
  764         PROC_LOCK(p2);
  765         while ((td2->td_dbgflags & TDB_STOPATFORK) != 0)
  766                 cv_wait(&p2->p_dbgwait, &p2->p_mtx);
  767         if (p2_held)
  768                 _PRELE(p2);
  769         PROC_UNLOCK(p2);
  770 }
  771 
  772 int
  773 fork1(struct thread *td, int flags, int pages, struct proc **procp,
  774     int *procdescp, int pdflags)
  775 {
  776         struct proc *p1;
  777         struct proc *newproc;
  778         int ok;
  779         struct thread *td2;
  780         struct vmspace *vm2;
  781         vm_ooffset_t mem_charged;
  782         int error;
  783         static int curfail;
  784         static struct timeval lastfail;
  785 #ifdef PROCDESC
  786         struct file *fp_procdesc = NULL;
  787 #endif
  788 
  789         /* Check for the undefined or unimplemented flags. */
  790         if ((flags & ~(RFFLAGS | RFTSIGFLAGS(RFTSIGMASK))) != 0)
  791                 return (EINVAL);
  792 
  793         /* Signal value requires RFTSIGZMB. */
  794         if ((flags & RFTSIGFLAGS(RFTSIGMASK)) != 0 && (flags & RFTSIGZMB) == 0)
  795                 return (EINVAL);
  796 
  797         /* Can't copy and clear. */
  798         if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
  799                 return (EINVAL);
  800 
  801         /* Check the validity of the signal number. */
  802         if ((flags & RFTSIGZMB) != 0 && (u_int)RFTSIGNUM(flags) > _SIG_MAXSIG)
  803                 return (EINVAL);
  804 
  805 #ifdef PROCDESC
  806         if ((flags & RFPROCDESC) != 0) {
  807                 /* Can't not create a process yet get a process descriptor. */
  808                 if ((flags & RFPROC) == 0)
  809                         return (EINVAL);
  810 
  811                 /* Must provide a place to put a procdesc if creating one. */
  812                 if (procdescp == NULL)
  813                         return (EINVAL);
  814         }
  815 #endif
  816 
  817         p1 = td->td_proc;
  818 
  819         /*
  820          * Here we don't create a new process, but we divorce
  821          * certain parts of a process from itself.
  822          */
  823         if ((flags & RFPROC) == 0) {
  824                 *procp = NULL;
  825                 return (fork_norfproc(td, flags));
  826         }
  827 
  828 #ifdef PROCDESC
  829         /*
  830          * If required, create a process descriptor in the parent first; we
  831          * will abandon it if something goes wrong. We don't finit() until
  832          * later.
  833          */
  834         if (flags & RFPROCDESC) {
  835                 error = falloc(td, &fp_procdesc, procdescp, 0);
  836                 if (error != 0)
  837                         return (error);
  838         }
  839 #endif
  840 
  841         mem_charged = 0;
  842         vm2 = NULL;
  843         if (pages == 0)
  844                 pages = KSTACK_PAGES;
  845         /* Allocate new proc. */
  846         newproc = uma_zalloc(proc_zone, M_WAITOK);
  847         td2 = FIRST_THREAD_IN_PROC(newproc);
  848         if (td2 == NULL) {
  849                 td2 = thread_alloc(pages);
  850                 if (td2 == NULL) {
  851                         error = ENOMEM;
  852                         goto fail1;
  853                 }
  854                 proc_linkup(newproc, td2);
  855         } else {
  856                 if (td2->td_kstack == 0 || td2->td_kstack_pages != pages) {
  857                         if (td2->td_kstack != 0)
  858                                 vm_thread_dispose(td2);
  859                         if (!thread_alloc_stack(td2, pages)) {
  860                                 error = ENOMEM;
  861                                 goto fail1;
  862                         }
  863                 }
  864         }
  865 
  866         if ((flags & RFMEM) == 0) {
  867                 vm2 = vmspace_fork(p1->p_vmspace, &mem_charged);
  868                 if (vm2 == NULL) {
  869                         error = ENOMEM;
  870                         goto fail1;
  871                 }
  872                 if (!swap_reserve(mem_charged)) {
  873                         /*
  874                          * The swap reservation failed. The accounting
  875                          * from the entries of the copied vm2 will be
  876                          * substracted in vmspace_free(), so force the
  877                          * reservation there.
  878                          */
  879                         swap_reserve_force(mem_charged);
  880                         error = ENOMEM;
  881                         goto fail1;
  882                 }
  883         } else
  884                 vm2 = NULL;
  885 
  886         /*
  887          * XXX: This is ugly; when we copy resource usage, we need to bump
  888          *      per-cred resource counters.
  889          */
  890         newproc->p_ucred = p1->p_ucred;
  891 
  892         /*
  893          * Initialize resource accounting for the child process.
  894          */
  895         error = racct_proc_fork(p1, newproc);
  896         if (error != 0) {
  897                 error = EAGAIN;
  898                 goto fail1;
  899         }
  900 
  901 #ifdef MAC
  902         mac_proc_init(newproc);
  903 #endif
  904         knlist_init_mtx(&newproc->p_klist, &newproc->p_mtx);
  905         STAILQ_INIT(&newproc->p_ktr);
  906 
  907         /* We have to lock the process tree while we look for a pid. */
  908         sx_slock(&proctree_lock);
  909 
  910         /*
  911          * Although process entries are dynamically created, we still keep
  912          * a global limit on the maximum number we will create.  Don't allow
  913          * a nonprivileged user to use the last ten processes; don't let root
  914          * exceed the limit. The variable nprocs is the current number of
  915          * processes, maxproc is the limit.
  916          */
  917         sx_xlock(&allproc_lock);
  918         if ((nprocs >= maxproc - 10 && priv_check_cred(td->td_ucred,
  919             PRIV_MAXPROC, 0) != 0) || nprocs >= maxproc) {
  920                 error = EAGAIN;
  921                 goto fail;
  922         }
  923 
  924         /*
  925          * Increment the count of procs running with this uid. Don't allow
  926          * a nonprivileged user to exceed their current limit.
  927          *
  928          * XXXRW: Can we avoid privilege here if it's not needed?
  929          */
  930         error = priv_check_cred(td->td_ucred, PRIV_PROC_LIMIT, 0);
  931         if (error == 0)
  932                 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1, 0);
  933         else {
  934                 PROC_LOCK(p1);
  935                 ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
  936                     lim_cur(p1, RLIMIT_NPROC));
  937                 PROC_UNLOCK(p1);
  938         }
  939         if (ok) {
  940                 do_fork(td, flags, newproc, td2, vm2, pdflags);
  941 
  942                 /*
  943                  * Return child proc pointer to parent.
  944                  */
  945                 *procp = newproc;
  946 #ifdef PROCDESC
  947                 if (flags & RFPROCDESC) {
  948                         procdesc_finit(newproc->p_procdesc, fp_procdesc);
  949                         fdrop(fp_procdesc, td);
  950                 }
  951 #endif
  952                 racct_proc_fork_done(newproc);
  953                 return (0);
  954         }
  955 
  956         error = EAGAIN;
  957 fail:
  958         sx_sunlock(&proctree_lock);
  959         if (ppsratecheck(&lastfail, &curfail, 1))
  960                 printf("maxproc limit exceeded by uid %u (pid %d); see tuning(7) and login.conf(5)\n",
  961                     td->td_ucred->cr_ruid, p1->p_pid);
  962         sx_xunlock(&allproc_lock);
  963 #ifdef MAC
  964         mac_proc_destroy(newproc);
  965 #endif
  966         racct_proc_exit(newproc);
  967 fail1:
  968         if (vm2 != NULL)
  969                 vmspace_free(vm2);
  970         uma_zfree(proc_zone, newproc);
  971 #ifdef PROCDESC
  972         if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
  973                 fdclose(td->td_proc->p_fd, fp_procdesc, *procdescp, td);
  974                 fdrop(fp_procdesc, td);
  975         }
  976 #endif
  977         pause("fork", hz / 2);
  978         return (error);
  979 }
  980 
  981 /*
  982  * Handle the return of a child process from fork1().  This function
  983  * is called from the MD fork_trampoline() entry point.
  984  */
  985 void
  986 fork_exit(void (*callout)(void *, struct trapframe *), void *arg,
  987     struct trapframe *frame)
  988 {
  989         struct proc *p;
  990         struct thread *td;
  991         struct thread *dtd;
  992 
  993         td = curthread;
  994         p = td->td_proc;
  995         KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
  996 
  997         CTR4(KTR_PROC, "fork_exit: new thread %p (td_sched %p, pid %d, %s)",
  998                 td, td->td_sched, p->p_pid, td->td_name);
  999 
 1000         sched_fork_exit(td);
 1001         /*
 1002         * Processes normally resume in mi_switch() after being
 1003         * cpu_switch()'ed to, but when children start up they arrive here
 1004         * instead, so we must do much the same things as mi_switch() would.
 1005         */
 1006         if ((dtd = PCPU_GET(deadthread))) {
 1007                 PCPU_SET(deadthread, NULL);
 1008                 thread_stash(dtd);
 1009         }
 1010         thread_unlock(td);
 1011 
 1012         /*
 1013          * cpu_set_fork_handler intercepts this function call to
 1014          * have this call a non-return function to stay in kernel mode.
 1015          * initproc has its own fork handler, but it does return.
 1016          */
 1017         KASSERT(callout != NULL, ("NULL callout in fork_exit"));
 1018         callout(arg, frame);
 1019 
 1020         /*
 1021          * Check if a kernel thread misbehaved and returned from its main
 1022          * function.
 1023          */
 1024         if (p->p_flag & P_KTHREAD) {
 1025                 printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
 1026                     td->td_name, p->p_pid);
 1027                 kproc_exit(0);
 1028         }
 1029         mtx_assert(&Giant, MA_NOTOWNED);
 1030 
 1031         if (p->p_sysent->sv_schedtail != NULL)
 1032                 (p->p_sysent->sv_schedtail)(td);
 1033 }
 1034 
 1035 /*
 1036  * Simplified back end of syscall(), used when returning from fork()
 1037  * directly into user mode.  Giant is not held on entry, and must not
 1038  * be held on return.  This function is passed in to fork_exit() as the
 1039  * first parameter and is called when returning to a new userland process.
 1040  */
 1041 void
 1042 fork_return(struct thread *td, struct trapframe *frame)
 1043 {
 1044         struct proc *p, *dbg;
 1045 
 1046         if (td->td_dbgflags & TDB_STOPATFORK) {
 1047                 p = td->td_proc;
 1048                 sx_xlock(&proctree_lock);
 1049                 PROC_LOCK(p);
 1050                 if ((p->p_pptr->p_flag & (P_TRACED | P_FOLLOWFORK)) ==
 1051                     (P_TRACED | P_FOLLOWFORK)) {
 1052                         /*
 1053                          * If debugger still wants auto-attach for the
 1054                          * parent's children, do it now.
 1055                          */
 1056                         dbg = p->p_pptr->p_pptr;
 1057                         p->p_flag |= P_TRACED;
 1058                         p->p_oppid = p->p_pptr->p_pid;
 1059                         CTR2(KTR_PTRACE,
 1060                     "fork_return: attaching to new child pid %d: oppid %d",
 1061                             p->p_pid, p->p_oppid);
 1062                         proc_reparent(p, dbg);
 1063                         sx_xunlock(&proctree_lock);
 1064                         td->td_dbgflags |= TDB_CHILD;
 1065                         ptracestop(td, SIGSTOP);
 1066                         td->td_dbgflags &= ~TDB_CHILD;
 1067                 } else {
 1068                         /*
 1069                          * ... otherwise clear the request.
 1070                          */
 1071                         sx_xunlock(&proctree_lock);
 1072                         td->td_dbgflags &= ~TDB_STOPATFORK;
 1073                         cv_broadcast(&p->p_dbgwait);
 1074                 }
 1075                 PROC_UNLOCK(p);
 1076         }
 1077 
 1078         userret(td, frame);
 1079 
 1080 #ifdef KTRACE
 1081         if (KTRPOINT(td, KTR_SYSRET))
 1082                 ktrsysret(SYS_fork, 0, 0);
 1083 #endif
 1084 }

Cache object: 75c74d33db25fbce9383e66651d8fe27


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