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root/usr/lib/posix/process/fork_nommu.c

DEFINITIONS

1. vfork
2. __parent_entry
3. __child_entry
4. fork

   1 /*
   2  * Copyright (c) 2006, Kohsuke Ohtani
   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  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  30 #include <sys/prex.h>
  31 #include <sys/posix.h>
  32 #include <sys/signal.h>
  33 #include <ipc/proc.h>
  34 #include <ipc/fs.h>
  35 #include <ipc/ipc.h>
  37 #include <stddef.h>
  38 #include <setjmp.h>
  39 #include <errno.h>
  41 static void __parent_entry(void);
  42 static void __child_entry(void);
  44 static jmp_buf __fork_env;
  45 static pid_t __child_pid;
  46 static thread_t __parent_thread;
  48 /*
  49  * vfork() - vfork for No-MMU system.
  50  *
  51  * RETURN VALUE:
  52  *
  53  *  vfork() returns 0 to the child process and return the process
  54  *  ID of the child process to the parent process. Or, -1 will be
  55  *  returned to the parent process if error.
  56  *
  57  * ERRORS:
  58  *
  59  *  EAGAIN
  60  *  ENOMEM
  61  *
  62  * NOTE:
  63  *
  64  *  Since no thread is created by task_create(), thread_create()
  65  *  must be called follwing task_crate(). But, when new thread is
  66  *  created by thread_create(), the stack pointer of new thread is
  67  *  used at thread_create() although the stack image is copied at
  68  *  task_create(). So, the stack pointer must be reset to same
  69  *  address of thread_create() before calling task_create();
  70  *  This is a little tricky...
  71  *
  72  * The new process is an exact copy of the calling process
  73  * except as detailed below:
  74  * - Process IDs are different.
  75  * - tms_* is set to 0.
  76  * - Alarm clock is set to 0.
  77  * - Opend semaphore is inherited.
  78  * - Pending signals are cleared.
  79  *
  80  * - File lock is not inherited.
  81  * - File descriptor is shared.
  82  * - Directory stream is shared.
  83  */
pid_t
vfork(void)
  86 {
  87         struct msg m;
task_t tsk;
thread_t t;
  90         int error, sts, pri;
  92         /* Save current stack pointer */
sts = setjmp(__fork_env);
  94         if (sts == 0) {
  95                 /*
  96                  * Create new task
  97                  */
  98                 if ((error = task_create(task_self(), VM_SHARE, &tsk)) != 0) {
errno = error;
 100                         return -1;
 101                 }
 102                 if ((error = thread_create(tsk, &t)) != 0) {
task_terminate(tsk);
errno = error;
 105                         return -1;
 106                 }
 107                 /*
 108                  * Notify to file system server
 109                  */
m.hdr.code = FS_FORK;
m.data[0] = tsk;                /* child task */
 112                 if (__posix_call(__fs_obj, &m, sizeof(m), 1) != 0)
 113                         return -1;
 115                 /*
 116                  * Notify to process server
 117                  */
m.hdr.code = PS_FORK;
m.data[0] = tsk;                /* child task */
m.data[1] = 1;                  /* fork type */
 121                 if (__posix_call(__proc_obj, &m, sizeof(m), 1) != 0)
 122                         return -1;
__child_pid = m.data[0];
 125                 /*
 126                  * Start child task.
 127                  *
 128                  * TODO:
 129                  * In order to synchronize the execution, we change
 130                  * the child's priority to lower value. This ugly hack
 131                  * will be replaced by some other methods...
 132                  */
thread_load(t, __child_entry, NULL);
thread_getpri(t, &pri);
thread_setpri(t, pri + 1);
thread_resume(t);
 138                 /*
 139                  * Suspend until child process calls exec() or exit()
 140                  */
__parent_thread = thread_self();
task_suspend(task_self());
 144         } else if (sts == 1) {
 145                 /*
 146                  * Child task
 147                  */
thread_load(__parent_thread, __parent_entry, NULL);
t = thread_self();
thread_getpri(t, &pri);
thread_setpri(t, pri - 1);
 153 #ifdef _REENTRANT
error = mutex_init(&__sig_lock);
 155 #endif
__sig_pending = 0;
thread_yield();
 158                 return 0;
 159         }
 160         return __child_pid;
 161 }
 163 static void
__parent_entry(void)
 165 {
longjmp(__fork_env, 2);
 168         /* NOTREACHED */
 169 }
 171 static void
__child_entry(void)
 173 {
longjmp(__fork_env, 1);
 176         /* NOTREACHED */
 177 }
 179 /*
 180  * fork() is not supported on NOMMU system.
 181  */
pid_t
fork(void)
 184 {
 186         return ENOSYS;
 187 }