76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
/*
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* This file contains two functions that can be used to perform
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* an EXEC call without the need for a "big" stack of MAX_ARG
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* bytes. It is primarily used by the INIT module of the system.
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*/
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#include <lib.h>
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#include <sys/types.h>
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#include <unistd.h>
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#define MAXSTK 256 /* maximum EXEC stack size */
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#define PTRSIZE sizeof(char *)
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_PROTOTYPE(int _execn,(char *name));
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_PROTOTYPE(int _execnl,(char *name, char *arg0));
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PRIVATE _PROTOTYPE(int _nexec,(char *name, char *argv[]));
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PUBLIC int _execn(name)
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char *name; /* pointer to file to be exec'd */
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{
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/* This funcion uses no arguments at all. */
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PRIVATE char stack[3 * PTRSIZE];
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return(_callm1(MM, EXEC, _len(name), sizeof(stack), 0, name, stack, NIL_PTR));
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}
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PUBLIC int _execnl(name, arg0)
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char *name;
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char *arg0;
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{
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/* This function resembles execl(2). */
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return(_nexec(name, &arg0));
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}
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PRIVATE int _nexec(name, argv)
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char *name; /* pointer to name of file to be executed */
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char *argv[]; /* pointer to argument array */
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{
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char stack[MAXSTK];
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char **argorg, *hp, **ap, *p;
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int i, nargs, stackbytes, offset;
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/* Count the argument pointers. */
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nargs = 0;
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argorg = argv;
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while (*argorg++ != NIL_PTR) nargs++;
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/* Prepare to set up the initial stack. */
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hp = &stack[(nargs + 3) * PTRSIZE];
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if (hp + nargs >= &stack[MAXSTK]) {
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errno = E2BIG;
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return(-1);
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}
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ap = (char **) stack;
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*ap++ = (char *) nargs;
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/* Prepare the argument pointers and strings. */
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for (i = 0; i < nargs; i++) {
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offset = hp - stack;
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*ap++ = (char *) offset;
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p = *argv++;
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while (*p) {
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*hp++ = *p++;
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if (hp >= &stack[MAXSTK]) {
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errno = E2BIG;
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return(-1);
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}
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}
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*hp++ = (char) 0;
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}
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*ap++ = NIL_PTR;
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stackbytes = (((int) (hp - stack) + PTRSIZE - 1) / PTRSIZE) * PTRSIZE;
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return(_callm1(MM, EXEC, _len(name), stackbytes, 0, name, stack, NIL_PTR));
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}
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