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scoutos / prex-0.9.0 / usr / server / proc / proc_fork.c @ 03e9c04a

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/*
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 * Copyright (c) 2005-2006, 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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/*
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 * fork.c - fork() support
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 */
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#include <sys/prex.h>
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#include <ipc/proc.h>
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#include <sys/list.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include "proc.h"
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static int vfork_start(struct proc *);
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/*
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 * PID previously allocated.
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 *
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 * Note: The following pids are reserved by default.
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 *   pid = 0: Process server
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 *   pid = 1: Init process
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 */
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static pid_t last_pid = 1;
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/*
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 * Assign new pid.
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 * Returns pid on sucess, or 0 on failure.
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 */
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static pid_t
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pid_alloc(void)
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{
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        pid_t pid;
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        pid = last_pid + 1;
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        if (pid >= PID_MAX)
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                pid = 1;
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        while (pid != last_pid) {
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                if (p_find(pid) == NULL)
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                        break;
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                if (++pid >= PID_MAX)
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                        pid = 1;
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        }
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        if (pid == last_pid)
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                return 0;
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        last_pid = pid;
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        return pid;
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}
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/*
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 * Create a new process.
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 */
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int
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newproc(struct proc *p, pid_t pid, task_t task)
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{
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        struct pgrp *pg;
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        pg = curproc->p_pgrp;
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        if (pid == 0) {
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                pid = pid_alloc();
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                if (pid == 0) {
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                        /* Too many processes */
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                        return EAGAIN;
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                }
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        }
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        /*
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         * make proc entry for new proc
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         */
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        p->p_parent = curproc;
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        p->p_pgrp = pg;
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        p->p_stat = SRUN;
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        p->p_exitcode = 0;
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        p->p_pid = pid;
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        p->p_task = task;
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        p->p_vforked = 0;
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        p->p_invfork = 0;
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        list_init(&p->p_children);
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        p_add(p);
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        list_insert(&curproc->p_children, &p->p_sibling);
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        list_insert(&pg->pg_members, &p->p_pgrp_link);
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        list_insert(&allproc, &p->p_link);
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        return 0;
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}
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/*
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 * fork() support.
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 *
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 * It creates new process data and update all process relations.
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 * The task creation and the thread creation are done by the
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 * fork() library stub.
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 */
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int
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sys_fork(task_t child, int vfork, pid_t *retval)
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{
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        struct proc *p;
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        int error;
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        DPRINTF(("proc: fork child=%x vfork=%d\n", child, vfork));
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        if (vfork && curproc->p_invfork) {
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                DPRINTF(("proc: vfork under vfork!\n"));
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                return EINVAL;
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        }
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        if (task_to_proc(child) != NULL) {
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                DPRINTF(("proc: process already exists\n"));
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                return EINVAL;
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        }
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        if ((p = malloc(sizeof(struct proc))) == NULL)
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                return ENOMEM;
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        memset(p, 0, sizeof(*p));
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        error = newproc(p, 0, child);
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        if (error)
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                return error;
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        if (vfork) {
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                vfork_start(curproc);
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                p->p_invfork = 1;
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        }
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        DPRINTF(("proc: fork newpid=%d\n", p->p_pid));
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        *retval = p->p_pid;
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        return 0;
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}
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/*
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 * Clean up all resource created by fork().
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 */
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void
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cleanup(struct proc *p)
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{
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        struct proc *pp;
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        DPRINTF(("proc: cleanup pid=%d\n", p->p_pid));
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        pp = p->p_parent;
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        list_remove(&p->p_sibling);
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        list_remove(&p->p_pgrp_link);
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        list_remove(&p->p_link);
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        free(p);
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}
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static int
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vfork_start(struct proc *p)
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{
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        void *stack;
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        /*
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         * Save parent's stack
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         */
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        DPRINTF(("proc: vfork_start stack=%x\n", p->p_stackbase));
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        if (vm_allocate(p->p_task, &stack, DFLSTKSZ, 1) != 0) {
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                DPRINTF(("proc: failed to allocate save stack\n"));
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                return ENOMEM;
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        }
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        memcpy(stack, p->p_stackbase, DFLSTKSZ);
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        p->p_stacksaved = stack;
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        p->p_vforked = 1;
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        return 0;
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}
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void
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vfork_end(struct proc *p)
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{
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        DPRINTF(("proc: vfork_end org=%x saved=%x\n", p->p_stackbase,
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                 p->p_stacksaved));
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        /*
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         * Restore parent's stack
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         */
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        memcpy(p->p_stackbase, p->p_stacksaved, DFLSTKSZ);
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        vm_free(p->p_task, p->p_stacksaved);
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        /*
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         * Resume parent
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         */
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        p->p_vforked = 0;
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        task_resume(p->p_task);
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}