#include "param.h"
#include "inode.h"
#include "dir.h"
#include "namei.h"
#include "exec.h"
#include "user.h"
#include "systm.h"

int
exec_script_check(struct exec_params *epp)
{
	char *cp;
	struct nameidata nd;
	struct nameidata *ndp;
	int error;
	struct inode *ip = 0;

	/*
	 * We come here with the first line of the executable
	 * script file.
	 * Check is to see if it starts with the magic marker:  #!
	 */
	if (epp->hdr.sh[0] != '#' || epp->hdr.sh[1] != '!' || epp->sh.interpreted)
		return ENOEXEC;
	epp->sh.interpreted = 1;

	/*
	 * If setuid/gid scripts were to be disallowed this is where it would
	 * have to be done.
	 * u.u_uid = uid;
	 * u.u_gid = u_groups[0];
	 */

	/*
	 * The first line of the text file
	 * should be one line on the format:
	 * #! <interpreter-name> <interpreter-argument>\n
	 */
	cp = &epp->hdr.sh[2];
	while (cp < &epp->hdr.sh[MIN(epp->hdr_len, SHSIZE)]) {
		if (*cp == '\t')
			*cp = ' ';
		else if (*cp == '\n') {
			*cp = '\0';
			break;
		}
		cp++;
	}
	if (cp == &epp->hdr.sh[MIN(epp->hdr_len, SHSIZE)])
		return ENOEXEC;

	/*
	 * Pick up script interpreter file name
	 */
	cp = &epp->hdr.sh[2];
	while (*cp == ' ')
		cp++;
	if (!*cp)
		return ENOEXEC;
	bzero(&nd, sizeof nd);
	ndp = &nd;
	ndp->ni_dirp = cp;
	while (*cp && *cp != ' ')
		cp++;
	if (*cp != '\0') {
		*cp++ = 0;
		while (*cp && *cp == ' ')
			cp++;
		if (*cp) {
			if ((error = copystr(cp, epp->sh.interparg, sizeof epp->sh.interparg, NULL)))
				goto done;
		}
	}

	/*
	 * the interpreter is the new file to exec
	 */
	ndp->ni_nameiop = LOOKUP | FOLLOW;
	ip = namei (ndp);
	if (ip == NULL)
		return u.u_error;
	if ((error = copystr(ndp->ni_dent.d_name, epp->sh.interpname, sizeof epp->sh.interpname, NULL)))
		goto done;

	/*
	 * Everything set up, do the recursive exec()
	 */
	if (epp->ip)
		iput(epp->ip);
	epp->ip = ip;
	error = exec_check(epp);
done:
	if (ip)
		iput(ip);
	return error;
}