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/compat/linux/linux_fork.c

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    1 /*-
    2  * Copyright (c) 2004 Tim J. Robbins
    3  * Copyright (c) 2002 Doug Rabson
    4  * Copyright (c) 2000 Marcel Moolenaar
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer
   12  *    in this position and unchanged.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: releng/10.2/sys/compat/linux/linux_fork.c 246085 2013-01-29 18:41:30Z jhb $");
   31 
   32 #include "opt_compat.h"
   33 #include "opt_kdtrace.h"
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/imgact.h>
   38 #include <sys/lock.h>
   39 #include <sys/mutex.h>
   40 #include <sys/proc.h>
   41 #include <sys/sched.h>
   42 #include <sys/sdt.h>
   43 #include <sys/sx.h>
   44 #include <sys/unistd.h>
   45 
   46 #ifdef COMPAT_LINUX32
   47 #include <machine/../linux32/linux.h>
   48 #include <machine/../linux32/linux32_proto.h>
   49 #else
   50 #include <machine/../linux/linux.h>
   51 #include <machine/../linux/linux_proto.h>
   52 #endif
   53 #include <compat/linux/linux_dtrace.h>
   54 #include <compat/linux/linux_signal.h>
   55 #include <compat/linux/linux_emul.h>
   56 #include <compat/linux/linux_misc.h>
   57 
   58 /* DTrace init */
   59 LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE);
   60 
   61 /* Linuxulator-global DTrace probes */
   62 LIN_SDT_PROBE_DECLARE(locks, emul_lock, locked);
   63 LIN_SDT_PROBE_DECLARE(locks, emul_lock, unlock);
   64 
   65 
   66 int
   67 linux_fork(struct thread *td, struct linux_fork_args *args)
   68 {
   69         int error;
   70         struct proc *p2;
   71         struct thread *td2;
   72 
   73 #ifdef DEBUG
   74         if (ldebug(fork))
   75                 printf(ARGS(fork, ""));
   76 #endif
   77 
   78         if ((error = fork1(td, RFFDG | RFPROC | RFSTOPPED, 0, &p2, NULL, 0))
   79             != 0)
   80                 return (error);
   81 
   82         td->td_retval[0] = p2->p_pid;
   83         td->td_retval[1] = 0;
   84 
   85         error = linux_proc_init(td, td->td_retval[0], 0);
   86         if (error)
   87                 return (error);
   88 
   89         td2 = FIRST_THREAD_IN_PROC(p2);
   90 
   91         /*
   92          * Make this runnable after we are finished with it.
   93          */
   94         thread_lock(td2);
   95         TD_SET_CAN_RUN(td2);
   96         sched_add(td2, SRQ_BORING);
   97         thread_unlock(td2);
   98 
   99         return (0);
  100 }
  101 
  102 int
  103 linux_vfork(struct thread *td, struct linux_vfork_args *args)
  104 {
  105         int error;
  106         struct proc *p2;
  107         struct thread *td2;
  108 
  109 #ifdef DEBUG
  110         if (ldebug(vfork))
  111                 printf(ARGS(vfork, ""));
  112 #endif
  113 
  114         /* Exclude RFPPWAIT */
  115         if ((error = fork1(td, RFFDG | RFPROC | RFMEM | RFSTOPPED, 0, &p2,
  116             NULL, 0)) != 0)
  117                 return (error);
  118 
  119         td->td_retval[0] = p2->p_pid;
  120 
  121         error = linux_proc_init(td, td->td_retval[0], 0);
  122         if (error)
  123                 return (error);
  124 
  125         PROC_LOCK(p2);
  126         p2->p_flag |= P_PPWAIT;
  127         PROC_UNLOCK(p2);
  128 
  129         td2 = FIRST_THREAD_IN_PROC(p2);
  130 
  131         /*
  132          * Make this runnable after we are finished with it.
  133          */
  134         thread_lock(td2);
  135         TD_SET_CAN_RUN(td2);
  136         sched_add(td2, SRQ_BORING);
  137         thread_unlock(td2);
  138 
  139         /* wait for the children to exit, ie. emulate vfork */
  140         PROC_LOCK(p2);
  141         while (p2->p_flag & P_PPWAIT)
  142                 cv_wait(&p2->p_pwait, &p2->p_mtx);
  143         PROC_UNLOCK(p2);
  144 
  145         return (0);
  146 }
  147 
  148 int
  149 linux_clone(struct thread *td, struct linux_clone_args *args)
  150 {
  151         int error, ff = RFPROC | RFSTOPPED;
  152         struct proc *p2;
  153         struct thread *td2;
  154         int exit_signal;
  155         struct linux_emuldata *em;
  156 
  157 #ifdef DEBUG
  158         if (ldebug(clone)) {
  159                 printf(ARGS(clone, "flags %x, stack %p, parent tid: %p, "
  160                     "child tid: %p"), (unsigned)args->flags,
  161                     args->stack, args->parent_tidptr, args->child_tidptr);
  162         }
  163 #endif
  164 
  165         exit_signal = args->flags & 0x000000ff;
  166         if (LINUX_SIG_VALID(exit_signal)) {
  167                 if (exit_signal <= LINUX_SIGTBLSZ)
  168                         exit_signal =
  169                             linux_to_bsd_signal[_SIG_IDX(exit_signal)];
  170         } else if (exit_signal != 0)
  171                 return (EINVAL);
  172 
  173         if (args->flags & LINUX_CLONE_VM)
  174                 ff |= RFMEM;
  175         if (args->flags & LINUX_CLONE_SIGHAND)
  176                 ff |= RFSIGSHARE;
  177         /*
  178          * XXX: In Linux, sharing of fs info (chroot/cwd/umask)
  179          * and open files is independant.  In FreeBSD, its in one
  180          * structure but in reality it does not cause any problems
  181          * because both of these flags are usually set together.
  182          */
  183         if (!(args->flags & (LINUX_CLONE_FILES | LINUX_CLONE_FS)))
  184                 ff |= RFFDG;
  185 
  186         /*
  187          * Attempt to detect when linux_clone(2) is used for creating
  188          * kernel threads. Unfortunately despite the existence of the
  189          * CLONE_THREAD flag, version of linuxthreads package used in
  190          * most popular distros as of beginning of 2005 doesn't make
  191          * any use of it. Therefore, this detection relies on
  192          * empirical observation that linuxthreads sets certain
  193          * combination of flags, so that we can make more or less
  194          * precise detection and notify the FreeBSD kernel that several
  195          * processes are in fact part of the same threading group, so
  196          * that special treatment is necessary for signal delivery
  197          * between those processes and fd locking.
  198          */
  199         if ((args->flags & 0xffffff00) == LINUX_THREADING_FLAGS)
  200                 ff |= RFTHREAD;
  201 
  202         if (args->flags & LINUX_CLONE_PARENT_SETTID)
  203                 if (args->parent_tidptr == NULL)
  204                         return (EINVAL);
  205 
  206         error = fork1(td, ff, 0, &p2, NULL, 0);
  207         if (error)
  208                 return (error);
  209 
  210         if (args->flags & (LINUX_CLONE_PARENT | LINUX_CLONE_THREAD)) {
  211                 sx_xlock(&proctree_lock);
  212                 PROC_LOCK(p2);
  213                 proc_reparent(p2, td->td_proc->p_pptr);
  214                 PROC_UNLOCK(p2);
  215                 sx_xunlock(&proctree_lock);
  216         }
  217 
  218         /* create the emuldata */
  219         error = linux_proc_init(td, p2->p_pid, args->flags);
  220         /* reference it - no need to check this */
  221         em = em_find(p2, EMUL_DOLOCK);
  222         KASSERT(em != NULL, ("clone: emuldata not found."));
  223         /* and adjust it */
  224 
  225         if (args->flags & LINUX_CLONE_THREAD) {
  226 #ifdef notyet
  227                 PROC_LOCK(p2);
  228                 p2->p_pgrp = td->td_proc->p_pgrp;
  229                 PROC_UNLOCK(p2);
  230 #endif
  231                 exit_signal = 0;
  232         }
  233 
  234         if (args->flags & LINUX_CLONE_CHILD_SETTID)
  235                 em->child_set_tid = args->child_tidptr;
  236         else
  237                 em->child_set_tid = NULL;
  238 
  239         if (args->flags & LINUX_CLONE_CHILD_CLEARTID)
  240                 em->child_clear_tid = args->child_tidptr;
  241         else
  242                 em->child_clear_tid = NULL;
  243 
  244         EMUL_UNLOCK(&emul_lock);
  245 
  246         if (args->flags & LINUX_CLONE_PARENT_SETTID) {
  247                 error = copyout(&p2->p_pid, args->parent_tidptr,
  248                     sizeof(p2->p_pid));
  249                 if (error)
  250                         printf(LMSG("copyout failed!"));
  251         }
  252 
  253         PROC_LOCK(p2);
  254         p2->p_sigparent = exit_signal;
  255         PROC_UNLOCK(p2);
  256         td2 = FIRST_THREAD_IN_PROC(p2);
  257         /*
  258          * In a case of stack = NULL, we are supposed to COW calling process
  259          * stack. This is what normal fork() does, so we just keep tf_rsp arg
  260          * intact.
  261          */
  262         if (args->stack)
  263                 linux_set_upcall_kse(td2, PTROUT(args->stack));
  264 
  265         if (args->flags & LINUX_CLONE_SETTLS)
  266                 linux_set_cloned_tls(td2, args->tls);
  267 
  268 #ifdef DEBUG
  269         if (ldebug(clone))
  270                 printf(LMSG("clone: successful rfork to %d, "
  271                     "stack %p sig = %d"), (int)p2->p_pid, args->stack,
  272                     exit_signal);
  273 #endif
  274         if (args->flags & LINUX_CLONE_VFORK) {
  275                 PROC_LOCK(p2);
  276                 p2->p_flag |= P_PPWAIT;
  277                 PROC_UNLOCK(p2);
  278         }
  279 
  280         /*
  281          * Make this runnable after we are finished with it.
  282          */
  283         thread_lock(td2);
  284         TD_SET_CAN_RUN(td2);
  285         sched_add(td2, SRQ_BORING);
  286         thread_unlock(td2);
  287 
  288         td->td_retval[0] = p2->p_pid;
  289         td->td_retval[1] = 0;
  290 
  291         if (args->flags & LINUX_CLONE_VFORK) {
  292                 /* wait for the children to exit, ie. emulate vfork */
  293                 PROC_LOCK(p2);
  294                 while (p2->p_flag & P_PPWAIT)
  295                         cv_wait(&p2->p_pwait, &p2->p_mtx);
  296                 PROC_UNLOCK(p2);
  297         }
  298 
  299         return (0);
  300 }

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