create.c

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#include <xinu.h>

local int newpid();

#define roundew(x) ((x + 3) & ~0x3)

pid32 create(void *procaddr, uint32 ssize, pri16 priority, char *name, uint32 nargs, ...)
{
    intmask mask;          /* interrupt mask        */
    pid32 pid;             /* stores new process id */
    struct procent *prptr; /* pointer to proc. table entry */
    int32 i;
    uint32 *a;     /* points to list of args    */
    uint32 *saddr; /* stack address     */

    mask = disable();
    if (ssize < MINSTK)
        ssize = MINSTK;
    ssize = (uint32)roundew(ssize);
    if (((saddr = (uint32 *)getstk(ssize)) ==
         (uint32 *)SYSERR) ||
        (pid = newpid()) == SYSERR || priority < 1)
    {
        restore(mask);
        return SYSERR;
    }

    prcount++;
    prptr = &proctab[pid];

    /* initialize process table entry for new process */
    prptr->prstate = PR_SUSP; /* initial state is suspended */
    prptr->prprio = priority;
    prptr->prstkbase = (char *)saddr;
    prptr->prstklen = ssize;
    prptr->prname[PNMLEN - 1] = NULLCH;
    for (i = 0; i < PNMLEN - 1 && (prptr->prname[i] = name[i]) != NULLCH; i++)
        ;
    prptr->prsem = -1;
    prptr->prparent = (pid32)getpid();
    prptr->prhasmsg = FALSE;

    /* set up initial device descriptors for the shell      */
    prptr->prdesc[0] = CONSOLE; /* stdin  is CONSOLE device */
    prptr->prdesc[1] = CONSOLE; /* stdout is CONSOLE device */
    prptr->prdesc[2] = CONSOLE; /* stderr is CONSOLE device */

    /* Initialize stack as if the process was called        */

    *saddr = STACKMAGIC;

    /* push arguments */
    a = (uint32 *)(&nargs + 1); /* start of args        */
    a += nargs - 1;             /* last argument        */
    for (; nargs > 4; nargs--)  /* machine dependent; copy args */
        *--saddr = *a--;        /* onto created process's stack */
    *--saddr = (long)procaddr;
    for (i = 11; i >= 4; i--)
        *--saddr = 0;
    for (i = 4; i > 0; i--)
    {
        if (i <= nargs)
            *--saddr = *a--;
        else
            *--saddr = 0;
    }
    *--saddr = (long)INITRET;    /* push on return address  */
    *--saddr = (long)0x00000053; /* CPSR F bit set,     */
    /* Supervisor mode      */
    prptr->prstkptr = (char *)saddr;
    restore(mask);
    return pid;
}

local pid32 newpid(void)
{
    uint32 i;                 /* iterate through all processes*/
    static pid32 nextpid = 1; /* position in table to try or    */
    /*  one beyond end of table */

    /* check all NPROC slots */

    for (i = 0; i < NPROC; i++)
    {
        nextpid %= NPROC; /* wrap around to beginning */
        if (proctab[nextpid].prstate == PR_FREE)
        {
            return nextpid++;
        }
        else
        {
            nextpid++;
        }
    }
    return (pid32)SYSERR;
}