addargs.c

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#include <xinu.h>
#include "shprototypes.h"

status addargs(pid32 pid, int32 ntok, int32 tok[], int32 tlen, char *tokbuf, void *dummy)
{
    intmask mask;          /* Saved interrupt mask      */
    struct procent *prptr; /* Ptr to process' table entry   */
    uint32 aloc;           /* Argument location in process stack as an integer  */
    uint32 *argloc;        /* Location in process's stack to place args vector  */
    char *argstr;          /* Location in process's stack to place arg strings  */
    uint32 *search;        /* pointer that searches for dummy argument on stack */
    uint32 *aptr;          /* Walks through args array  */
    int32 i;               /* Index into tok array      */

    mask = disable();

    /* Check argument count and data length */

    if ((ntok <= 0) || (tlen < 0))
    {
        restore(mask);
        return SYSERR;
    }

    prptr = &proctab[pid];

    /* Compute lowest location in the process stack where the   */
    /*  args array will be stored followed by the argument  */
    /*  strings                         */

    aloc = (uint32)(prptr->prstkbase - prptr->prstklen + sizeof(uint32));
    argloc = (uint32 *)((aloc + 3) & ~0x3); /* round multiple of 4  */

    /* Compute the first location beyond args array for the strings */

    argstr = (char *)(argloc + (ntok + 1)); /* +1 for a null ptr    */

    /* Set each location in the args vector to be the address of    */
    /*  string area plus the offset of this argument        */

    for (aptr = argloc, i = 0; i < ntok; i++)
    {
        *aptr++ = (uint32)(argstr + tok[i]);
    }

    /* Add a null pointer to the args array */

    *aptr++ = (uint32)NULL;

    /* Copy the argument strings from tokbuf into process's stack   */
    /*  just beyond the args vector             */

    memcpy(aptr, tokbuf, tlen);

    /* Find the second argument in process's stack */

    for (search = (uint32 *)prptr->prstkptr;
         search < (uint32 *)prptr->prstkbase; search++)
    {

        /* If found, replace with the address of the args vector*/

        if (*search == (uint32)dummy)
        {
            *search = (uint32)argloc;
            restore(mask);
            return OK;
        }
    }

    /* Argument value not found on the stack - report an error */

    restore(mask);
    return SYSERR;
}