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scoutos / prex-0.9.0 / usr / lib / posix / process / fork_nommu.c @ 03e9c04a

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/*
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 * Copyright (c) 2006, Kohsuke Ohtani
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the author nor the names of any co-contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/prex.h>
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#include <sys/posix.h>
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#include <sys/signal.h>
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#include <ipc/proc.h>
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#include <ipc/fs.h>
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#include <ipc/ipc.h>
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#include <stddef.h>
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#include <setjmp.h>
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#include <errno.h>
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static void __parent_entry(void);
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static void __child_entry(void);
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static jmp_buf __fork_env;
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static pid_t __child_pid;
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static thread_t __parent_thread;
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/*
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 * vfork() - vfork for No-MMU system.
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 *
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 * RETURN VALUE:
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 *
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 *  vfork() returns 0 to the child process and return the process
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 *  ID of the child process to the parent process. Or, -1 will be
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 *  returned to the parent process if error.
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 *
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 * ERRORS:
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 *
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 *  EAGAIN
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 *  ENOMEM
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 *
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 * NOTE:
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 *
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 *  Since no thread is created by task_create(), thread_create()
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 *  must be called follwing task_crate(). But, when new thread is
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 *  created by thread_create(), the stack pointer of new thread is
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 *  used at thread_create() although the stack image is copied at
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 *  task_create(). So, the stack pointer must be reset to same
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 *  address of thread_create() before calling task_create();
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 *  This is a little tricky...
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 *
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 * The new process is an exact copy of the calling process
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 * except as detailed below:
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 * - Process IDs are different.
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 * - tms_* is set to 0.
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 * - Alarm clock is set to 0.
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 * - Opend semaphore is inherited.
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 * - Pending signals are cleared.
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 *
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 * - File lock is not inherited.
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 * - File descriptor is shared.
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 * - Directory stream is shared.
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 */
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pid_t
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vfork(void)
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{
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        struct msg m;
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        task_t tsk;
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        thread_t t;
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        int error, sts, pri;
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        /* Save current stack pointer */
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        sts = setjmp(__fork_env);
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        if (sts == 0) {
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                /*
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                 * Create new task
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                 */
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                if ((error = task_create(task_self(), VM_SHARE, &tsk)) != 0) {
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                        errno = error;
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                        return -1;
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                }
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                if ((error = thread_create(tsk, &t)) != 0) {
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                        task_terminate(tsk);
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                        errno = error;
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                        return -1;
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                }
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                /*
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                 * Notify to file system server
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                 */
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                m.hdr.code = FS_FORK;
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                m.data[0] = tsk;                /* child task */
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                if (__posix_call(__fs_obj, &m, sizeof(m), 1) != 0)
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                        return -1;
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                /*
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                 * Notify to process server
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                 */
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                m.hdr.code = PS_FORK;
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                m.data[0] = tsk;                /* child task */
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                m.data[1] = 1;                        /* fork type */
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                if (__posix_call(__proc_obj, &m, sizeof(m), 1) != 0)
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                        return -1;
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                __child_pid = m.data[0];
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                /*
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                 * Start child task.
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                 *
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                 * TODO:
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                 * In order to synchronize the execution, we change
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                 * the child's priority to lower value. This ugly hack
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                 * will be replaced by some other methods...
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                 */
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                thread_load(t, __child_entry, NULL);
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                thread_getpri(t, &pri);
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                thread_setpri(t, pri + 1);
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                thread_resume(t);
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                /*
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                 * Suspend until child process calls exec() or exit()
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                 */
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                __parent_thread = thread_self();
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                task_suspend(task_self());
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        } else if (sts == 1) {
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                /*
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                 * Child task
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                 */
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                thread_load(__parent_thread, __parent_entry, NULL);
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                t = thread_self();
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                thread_getpri(t, &pri);
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                thread_setpri(t, pri - 1);
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#ifdef _REENTRANT
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                error = mutex_init(&__sig_lock);
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#endif
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                __sig_pending = 0;
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                thread_yield();
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                return 0;
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        }
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        return __child_pid;
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}
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static void
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__parent_entry(void)
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{
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        longjmp(__fork_env, 2);
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        /* NOTREACHED */
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}
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static void
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__child_entry(void)
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{
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        longjmp(__fork_env, 1);
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        /* NOTREACHED */
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}
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/*
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 * fork() is not supported on NOMMU system.
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 */
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pid_t
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fork(void)
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{
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        return ENOSYS;
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}