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_emul.c

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    1 /*-
    2  * Copyright (c) 2006 Roman Divacky
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer
   10  *    in this position and unchanged.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. The name of the author may not be used to endorse or promote products
   15  *    derived from this software without specific prior written permission
   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/8.2/sys/compat/linux/linux_emul.c 191269 2009-04-19 13:48:42Z dchagin $");
   31 
   32 #include "opt_compat.h"
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/imgact.h>
   37 #include <sys/kernel.h>
   38 #include <sys/lock.h>
   39 #include <sys/malloc.h>
   40 #include <sys/mutex.h>
   41 #include <sys/sx.h>
   42 #include <sys/proc.h>
   43 #include <sys/syscallsubr.h>
   44 #include <sys/sysproto.h>
   45 #include <sys/unistd.h>
   46 
   47 #ifdef COMPAT_LINUX32
   48 #include <machine/../linux32/linux.h>
   49 #include <machine/../linux32/linux32_proto.h>
   50 #else
   51 #include <machine/../linux/linux.h>
   52 #include <machine/../linux/linux_proto.h>
   53 #endif
   54 
   55 #include <compat/linux/linux_emul.h>
   56 #include <compat/linux/linux_futex.h>
   57 
   58 struct sx       emul_shared_lock;
   59 struct mtx      emul_lock;
   60 
   61 /* this returns locked reference to the emuldata entry (if found) */
   62 struct linux_emuldata *
   63 em_find(struct proc *p, int locked)
   64 {
   65         struct linux_emuldata *em;
   66 
   67         if (locked == EMUL_DOLOCK)
   68                 EMUL_LOCK(&emul_lock);
   69 
   70         em = p->p_emuldata;
   71 
   72         if (em == NULL && locked == EMUL_DOLOCK)
   73                 EMUL_UNLOCK(&emul_lock);
   74 
   75         return (em);
   76 }
   77 
   78 int
   79 linux_proc_init(struct thread *td, pid_t child, int flags)
   80 {
   81         struct linux_emuldata *em, *p_em;
   82         struct proc *p;
   83 
   84         if (child != 0) {
   85                 /* non-exec call */
   86                 em = malloc(sizeof *em, M_LINUX, M_WAITOK | M_ZERO);
   87                 em->pid = child;
   88                 em->pdeath_signal = 0;
   89                 em->used_requeue = 0;
   90                 em->robust_futexes = NULL;
   91                 if (flags & LINUX_CLONE_THREAD) {
   92                         /* handled later in the code */
   93                 } else {
   94                         struct linux_emuldata_shared *s;
   95 
   96                         s = malloc(sizeof *s, M_LINUX, M_WAITOK | M_ZERO);
   97                         s->refs = 1;
   98                         s->group_pid = child;
   99 
  100                         LIST_INIT(&s->threads);
  101                         em->shared = s;
  102                 }
  103         } else {
  104                 /* lookup the old one */
  105                 em = em_find(td->td_proc, EMUL_DOLOCK);
  106                 KASSERT(em != NULL, ("proc_init: emuldata not found in exec case.\n"));
  107         }
  108 
  109         em->child_clear_tid = NULL;
  110         em->child_set_tid = NULL;
  111 
  112         /*
  113          * allocate the shared struct only in clone()/fork cases in the case
  114          * of clone() td = calling proc and child = pid of the newly created
  115          * proc
  116          */
  117         if (child != 0) {
  118                 if (flags & LINUX_CLONE_THREAD) {
  119                         /* lookup the parent */
  120                         /* 
  121                          * we dont have to lock the p_em because
  122                          * its waiting for us in linux_clone so
  123                          * there is no chance of it changing the
  124                          * p_em->shared address
  125                          */
  126                         p_em = em_find(td->td_proc, EMUL_DONTLOCK);
  127                         KASSERT(p_em != NULL, ("proc_init: parent emuldata not found for CLONE_THREAD\n"));
  128                         em->shared = p_em->shared;
  129                         EMUL_SHARED_WLOCK(&emul_shared_lock);
  130                         em->shared->refs++;
  131                         EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  132                 } else {
  133                         /*
  134                          * handled earlier to avoid malloc(M_WAITOK) with
  135                          * rwlock held
  136                          */
  137                 }
  138         }
  139         if (child != 0) {
  140                 EMUL_SHARED_WLOCK(&emul_shared_lock);
  141                 LIST_INSERT_HEAD(&em->shared->threads, em, threads);
  142                 EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  143 
  144                 p = pfind(child);
  145                 KASSERT(p != NULL, ("process not found in proc_init\n"));
  146                 p->p_emuldata = em;
  147                 PROC_UNLOCK(p);
  148         } else
  149                 EMUL_UNLOCK(&emul_lock);
  150 
  151         return (0);
  152 }
  153 
  154 void
  155 linux_proc_exit(void *arg __unused, struct proc *p)
  156 {
  157         struct linux_emuldata *em;
  158         int error;
  159         struct thread *td = FIRST_THREAD_IN_PROC(p);
  160         int *child_clear_tid;
  161         struct proc *q, *nq;
  162 
  163         if (__predict_true(p->p_sysent != &elf_linux_sysvec))
  164                 return;
  165 
  166         release_futexes(p);
  167 
  168         /* find the emuldata */
  169         em = em_find(p, EMUL_DOLOCK);
  170 
  171         KASSERT(em != NULL, ("proc_exit: emuldata not found.\n"));
  172 
  173         /* reparent all procs that are not a thread leader to initproc */
  174         if (em->shared->group_pid != p->p_pid) {
  175                 child_clear_tid = em->child_clear_tid;
  176                 EMUL_UNLOCK(&emul_lock);
  177                 sx_xlock(&proctree_lock);
  178                 wakeup(initproc);
  179                 PROC_LOCK(p);
  180                 proc_reparent(p, initproc);
  181                 p->p_sigparent = SIGCHLD;
  182                 PROC_UNLOCK(p);
  183                 sx_xunlock(&proctree_lock);
  184         } else {
  185                 child_clear_tid = em->child_clear_tid;
  186                 EMUL_UNLOCK(&emul_lock);        
  187         }
  188 
  189         EMUL_SHARED_WLOCK(&emul_shared_lock);
  190         LIST_REMOVE(em, threads);
  191 
  192         em->shared->refs--;
  193         if (em->shared->refs == 0) {
  194                 EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  195                 free(em->shared, M_LINUX);
  196         } else  
  197                 EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  198 
  199         if (child_clear_tid != NULL) {
  200                 struct linux_sys_futex_args cup;
  201                 int null = 0;
  202 
  203                 error = copyout(&null, child_clear_tid, sizeof(null));
  204                 if (error) {
  205                         free(em, M_LINUX);
  206                         return;
  207                 }
  208 
  209                 /* futexes stuff */
  210                 cup.uaddr = child_clear_tid;
  211                 cup.op = LINUX_FUTEX_WAKE;
  212                 cup.val = 0x7fffffff;   /* Awake everyone */
  213                 cup.timeout = NULL;
  214                 cup.uaddr2 = NULL;
  215                 cup.val3 = 0;
  216                 error = linux_sys_futex(FIRST_THREAD_IN_PROC(p), &cup);
  217                 /*
  218                  * this cannot happen at the moment and if this happens it
  219                  * probably means there is a user space bug
  220                  */
  221                 if (error)
  222                         printf(LMSG("futex stuff in proc_exit failed.\n"));
  223         }
  224 
  225         /* clean the stuff up */
  226         free(em, M_LINUX);
  227 
  228         /* this is a little weird but rewritten from exit1() */
  229         sx_xlock(&proctree_lock);
  230         q = LIST_FIRST(&p->p_children);
  231         for (; q != NULL; q = nq) {
  232                 nq = LIST_NEXT(q, p_sibling);
  233                 if (q->p_flag & P_WEXIT)
  234                         continue;
  235                 if (__predict_false(q->p_sysent != &elf_linux_sysvec))
  236                         continue;
  237                 em = em_find(q, EMUL_DOLOCK);
  238                 KASSERT(em != NULL, ("linux_reparent: emuldata not found: %i\n", q->p_pid));
  239                 PROC_LOCK(q);
  240                 if ((q->p_flag & P_WEXIT) == 0 && em->pdeath_signal != 0) {
  241                         psignal(q, em->pdeath_signal);
  242                 }
  243                 PROC_UNLOCK(q);
  244                 EMUL_UNLOCK(&emul_lock);
  245         }
  246         sx_xunlock(&proctree_lock);
  247 }
  248 
  249 /*
  250  * This is used in a case of transition from FreeBSD binary execing to linux binary
  251  * in this case we create linux emuldata proc entry with the pid of the currently running
  252  * process.
  253  */
  254 void 
  255 linux_proc_exec(void *arg __unused, struct proc *p, struct image_params *imgp)
  256 {
  257         if (__predict_false(imgp->sysent == &elf_linux_sysvec
  258             && p->p_sysent != &elf_linux_sysvec))
  259                 linux_proc_init(FIRST_THREAD_IN_PROC(p), p->p_pid, 0);
  260         if (__predict_false(imgp->sysent != &elf_linux_sysvec
  261             && p->p_sysent == &elf_linux_sysvec)) {
  262                 struct linux_emuldata *em;
  263 
  264                 /* 
  265                  * XXX:There's a race because here we assign p->p_emuldata NULL
  266                  * but the process is still counted as linux one for a short
  267                  * time so some other process might reference it and try to
  268                  * access its p->p_emuldata and panicing on a NULL reference.
  269                  */
  270                 em = em_find(p, EMUL_DONTLOCK);
  271 
  272                 KASSERT(em != NULL, ("proc_exec: emuldata not found.\n"));
  273 
  274                 EMUL_SHARED_WLOCK(&emul_shared_lock);
  275                 LIST_REMOVE(em, threads);
  276 
  277                 PROC_LOCK(p);
  278                 p->p_emuldata = NULL;
  279                 PROC_UNLOCK(p);
  280 
  281                 em->shared->refs--;
  282                 if (em->shared->refs == 0) {
  283                         EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  284                         free(em->shared, M_LINUX);
  285                 } else
  286                         EMUL_SHARED_WUNLOCK(&emul_shared_lock);
  287 
  288                 free(em, M_LINUX);
  289         }
  290 }
  291 
  292 void
  293 linux_schedtail(void *arg __unused, struct proc *p)
  294 {
  295         struct linux_emuldata *em;
  296         int error = 0;
  297         int *child_set_tid;
  298 
  299         if (__predict_true(p->p_sysent != &elf_linux_sysvec))
  300                 return;
  301 
  302         /* find the emuldata */
  303         em = em_find(p, EMUL_DOLOCK);
  304 
  305         KASSERT(em != NULL, ("linux_schedtail: emuldata not found.\n"));
  306         child_set_tid = em->child_set_tid;
  307         EMUL_UNLOCK(&emul_lock);
  308 
  309         if (child_set_tid != NULL)
  310                 error = copyout(&p->p_pid, (int *)child_set_tid,
  311                     sizeof(p->p_pid));
  312 
  313         return;
  314 }
  315 
  316 int
  317 linux_set_tid_address(struct thread *td, struct linux_set_tid_address_args *args)
  318 {
  319         struct linux_emuldata *em;
  320 
  321 #ifdef DEBUG
  322         if (ldebug(set_tid_address))
  323                 printf(ARGS(set_tid_address, "%p"), args->tidptr);
  324 #endif
  325 
  326         /* find the emuldata */
  327         em = em_find(td->td_proc, EMUL_DOLOCK);
  328 
  329         KASSERT(em != NULL, ("set_tid_address: emuldata not found.\n"));
  330 
  331         em->child_clear_tid = args->tidptr;
  332         td->td_retval[0] = td->td_proc->p_pid;
  333 
  334         EMUL_UNLOCK(&emul_lock);
  335         return 0;
  336 }

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