Home | History | Annotate | Line # | Download | only in common
compat_util.c revision 1.3 
      1 /* 	$NetBSD: compat_util.c,v 1.3 1995/10/22 08:20:44 mycroft Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1994 Christos Zoulas
      5  * Copyright (c) 1995 Frank van der Linden
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. The name of the author may not be used to endorse or promote products
     17  *    derived from this software without specific prior written permission
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  *
     30  */
     31 
     32 #include <sys/param.h>
     33 #include <sys/systm.h>
     34 #include <sys/namei.h>
     35 #include <sys/proc.h>
     36 #include <sys/file.h>
     37 #include <sys/stat.h>
     38 #include <sys/filedesc.h>
     39 #include <sys/ioctl.h>
     40 #include <sys/kernel.h>
     41 #include <sys/malloc.h>
     42 #include <sys/vnode.h>
     43 
     44 #include <compat/common/compat_util.h>
     45 
     46 /*
     47  * Search an alternate path before passing pathname arguments on
     48  * to system calls. Useful for keeping a separate 'emulation tree'.
     49  *
     50  * If cflag is set, we check if an attempt can be made to create
     51  * the named file, i.e. we check if the directory it should
     52  * be in exists.
     53  */
     54 int
     55 emul_find(p, sgp, prefix, path, pbuf, cflag)
     56 	struct proc	 *p;
     57 	caddr_t		 *sgp;		/* Pointer to stackgap memory */
     58 	const char	 *prefix;
     59 	char		 *path;
     60 	char		**pbuf;
     61 	int		  cflag;
     62 {
     63 	struct nameidata	 nd;
     64 	struct nameidata	 ndroot;
     65 	struct vattr		 vat;
     66 	struct vattr		 vatroot;
     67 	int			 error;
     68 	char			*ptr, *buf, *cp;
     69 	const char		*pr;
     70 	size_t			 sz, len;
     71 
     72 	buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
     73 	*pbuf = path;
     74 
     75 	for (ptr = buf, pr = prefix; (*ptr = *pr) != '\0'; ptr++, pr++)
     76 		continue;
     77 
     78 	sz = MAXPATHLEN - (ptr - buf);
     79 
     80 	/*
     81 	 * If sgp is not given then the path is already in kernel space
     82 	 */
     83 	if (sgp == NULL)
     84 		error = copystr(path, ptr, sz, &len);
     85 	else
     86 		error = copyinstr(path, ptr, sz, &len);
     87 
     88 	if (error)
     89 		goto bad;
     90 
     91 	if (*ptr != '/') {
     92 		error = EINVAL;
     93 		goto bad;
     94 	}
     95 
     96 	/*
     97 	 * We know that there is a / somewhere in this pathname.
     98 	 * Search backwards for it, to find the file's parent dir
     99 	 * to see if it exists in the alternate tree. If it does,
    100 	 * and we want to create a file (cflag is set). We don't
    101 	 * need to worry about the root comparison in this case.
    102 	 */
    103 
    104 	if (cflag) {
    105 		for (cp = &ptr[len] - 1; *cp != '/'; cp--)
    106 			;
    107 		*cp = '\0';
    108 
    109 		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
    110 
    111 		if ((error = namei(&nd)) != 0)
    112 			goto bad;
    113 
    114 		*cp = '/';
    115 	}
    116 	else {
    117 		NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
    118 
    119 		if ((error = namei(&nd)) != 0)
    120 			goto bad;
    121 
    122 		/*
    123 		 * We now compare the vnode of the emulation root to the one
    124 		 * vnode asked. If they resolve to be the same, then we
    125 		 * ignore the match so that the real root gets used.
    126 		 * This avoids the problem of traversing "../.." to find the
    127 		 * root directory and never finding it, because "/" resolves
    128 		 * to the emulation root directory. This is expensive :-(
    129 		 */
    130 		/* XXX: prototype should have const here for NDINIT */
    131 		NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE,
    132 		       (char *) prefix, p);
    133 
    134 		if ((error = namei(&ndroot)) != 0)
    135 			goto bad2;
    136 
    137 		if ((error = VOP_GETATTR(nd.ni_vp, &vat, p->p_ucred, p)) != 0)
    138 			goto bad3;
    139 
    140 		if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, p->p_ucred, p))
    141 		    != 0)
    142 			goto bad3;
    143 
    144 		if (vat.va_fsid == vatroot.va_fsid &&
    145 		    vat.va_fileid == vatroot.va_fileid) {
    146 			error = ENOENT;
    147 			goto bad3;
    148 		}
    149 	}
    150 	if (sgp == NULL)
    151 		*pbuf = buf;
    152 	else {
    153 		sz = &ptr[len] - buf;
    154 		*pbuf = stackgap_alloc(sgp, sz + 1);
    155 		error = copyout(buf, *pbuf, sz);
    156 		free(buf, M_TEMP);
    157 	}
    158 
    159 done:
    160 	vrele(nd.ni_vp);
    161 	if (!cflag)
    162 		vrele(ndroot.ni_vp);
    163 	return error;
    164 
    165 bad3:
    166 	vrele(ndroot.ni_vp);
    167 bad2:
    168 	vrele(nd.ni_vp);
    169 bad:
    170 	free(buf, M_TEMP);
    171 	return error;
    172 }
    173