/*      $NetBSD: subr_emul.c,v 1.4 2026/01/04 03:17:08 riastradh Exp $  */

/*-
 * Copyright (c) 1994, 2000, 2005, 2015 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Christos Zoulas and Maxime Villard.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Copyright (c) 1996 Christopher G. Demetriou
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(1, "$NetBSD: subr_emul.c,v 1.4 2026/01/04 03:17:08 riastradh Exp $");

#ifdef _KERNEL_OPT
#include "opt_pax.h"
#endif /* _KERNEL_OPT */

#include <sys/param.h>

#include <sys/exec.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/sdt.h>
#include <sys/vnode.h>

#include <compat/common/compat_util.h>

void
emul_find_root(struct lwp *l, struct exec_package *epp)
{
        struct vnode *vp;
        const char *emul_path;

        if (epp->ep_emul_root != NULL)
                /* We've already found it */
                return;

        emul_path = epp->ep_esch->es_emul->e_path;
        if (emul_path == NULL)
                /* Emulation doesn't have a root */
                return;

        if (namei_simple_kernel(emul_path, NSM_FOLLOW_NOEMULROOT, &vp) != 0)
                /* emulation root doesn't exist */
                return;

        epp->ep_emul_root = vp;
}

/*
 * Search the alternate path for dynamic binary interpreter. If not found
 * there, check if the interpreter exists in within 'proper' tree.
 */
int
emul_find_interp(struct lwp *l, struct exec_package *epp, const char *itp)
{
        int error;
        struct pathbuf *pb;
        struct nameidata nd;
        unsigned int flags;

        pb = pathbuf_create(itp);
        if (pb == NULL) {
                return SET_ERROR(ENOMEM);
        }

        /* If we haven't found the emulation root already, do so now */
        /* Maybe we should remember failures somehow ? */
        if (epp->ep_esch->es_emul->e_path != 0 && epp->ep_emul_root == NULL)
                emul_find_root(l, epp);

        if (epp->ep_interp != NULL)
                vrele(epp->ep_interp);

        /* We need to use the emulation root for the new program,
         * not the one for the current process. */
        if (epp->ep_emul_root == NULL)
                flags = FOLLOW;
        else {
                nd.ni_erootdir = epp->ep_emul_root;
                /* hack: Pass in the emulation path for ktrace calls */
                nd.ni_next = epp->ep_esch->es_emul->e_path;
                flags = FOLLOW | TRYEMULROOT | EMULROOTSET;
        }

        NDINIT(&nd, LOOKUP, flags, pb);
        error = namei(&nd);
        if (error != 0) {
                epp->ep_interp = NULL;
                pathbuf_destroy(pb);
                return error;
        }

        /* Save interpreter in case we actually need to load it */
        epp->ep_interp = nd.ni_vp;

        pathbuf_destroy(pb);

        return 0;
}