linux_util.c

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    1 /*
    2  * Copyright (c) 1994 Christos Zoulas
    3  * Copyright (c) 1995 Frank van der Linden
    4  * Copyright (c) 1995 Scott Bartram
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. The name of the author may not be used to endorse or promote products
   16  *    derived from this software without specific prior written permission
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   28  *
   29  *      from: svr4_util.c,v 1.5 1995/01/22 23:44:50 christos Exp
   30  * $FreeBSD: releng/5.0/sys/compat/linux/linux_util.c 102803 2002-09-01 21:15:37Z iedowse $
   31  */
   32 
   33 #include <sys/param.h>
   34 #include <sys/systm.h>
   35 #include <sys/namei.h>
   36 #include <sys/proc.h>
   37 #include <sys/malloc.h>
   38 #include <sys/vnode.h>
   39 
   40 #include <compat/linux/linux_util.h>
   41 
   42 const char      linux_emul_path[] = "/compat/linux";
   43 
   44 /*
   45  * Search an alternate path before passing pathname arguments on
   46  * to system calls. Useful for keeping a separate 'emulation tree'.
   47  *
   48  * If cflag is set, we check if an attempt can be made to create
   49  * the named file, i.e. we check if the directory it should
   50  * be in exists.
   51  */
   52 int
   53 linux_emul_find(td, sgp, path, pbuf, cflag)
   54         struct thread    *td;
   55         caddr_t          *sgp;          /* Pointer to stackgap memory */
   56         char             *path;
   57         char            **pbuf;
   58         int               cflag;
   59 {
   60         char *newpath;
   61         size_t sz;
   62         int error;
   63 
   64         error = linux_emul_convpath(td, path, (sgp == NULL) ? UIO_SYSSPACE :
   65             UIO_USERSPACE, &newpath, cflag);
   66         if (newpath == NULL)
   67                 return (error);
   68 
   69         if (sgp == NULL) {
   70                 *pbuf = newpath;
   71                 return (error);
   72         }
   73 
   74         sz = strlen(newpath);
   75         *pbuf = stackgap_alloc(sgp, sz + 1);
   76         if (*pbuf != NULL)
   77                 error = copyout(newpath, *pbuf, sz + 1);
   78         else
   79                 error = ENAMETOOLONG;
   80         free(newpath, M_TEMP);
   81 
   82         return (error);
   83 }
   84 
   85 int
   86 linux_emul_convpath(td, path, pathseg, pbuf, cflag)
   87         struct thread    *td;
   88         char             *path;
   89         enum uio_seg      pathseg;
   90         char            **pbuf;
   91         int               cflag;
   92 {
   93         struct nameidata         nd;
   94         struct nameidata         ndroot;
   95         struct vattr             vat;
   96         struct vattr             vatroot;
   97         int                      error;
   98         const char              *prefix;
   99         char                    *ptr, *buf, *cp;
  100         size_t                   len, sz;
  101 
  102         buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
  103         *pbuf = buf;
  104 
  105         prefix = linux_emul_path;
  106         for (ptr = buf; (*ptr = *prefix) != '\0'; ptr++, prefix++)
  107                 continue;
  108         sz = MAXPATHLEN - (ptr - buf);
  109 
  110         if (pathseg == UIO_SYSSPACE)
  111                 error = copystr(path, ptr, sz, &len);
  112         else
  113                 error = copyinstr(path, ptr, sz, &len);
  114 
  115         if (error) {
  116                 *pbuf = NULL;
  117                 free(buf, M_TEMP);
  118                 return error;
  119         }
  120 
  121         if (*ptr != '/') {
  122                 error = EINVAL;
  123                 goto keeporig;
  124         }
  125 
  126         /*
  127          * We know that there is a / somewhere in this pathname.
  128          * Search backwards for it, to find the file's parent dir
  129          * to see if it exists in the alternate tree. If it does,
  130          * and we want to create a file (cflag is set). We don't
  131          * need to worry about the root comparison in this case.
  132          */
  133 
  134         if (cflag) {
  135                 for (cp = &ptr[len] - 1; *cp != '/'; cp--);
  136                 *cp = '\0';
  137 
  138                 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, td);
  139                 error = namei(&nd);
  140                 *cp = '/';
  141                 if (error != 0)
  142                         goto keeporig;
  143         }
  144         else {
  145                 NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, td);
  146 
  147                 if ((error = namei(&nd)) != 0)
  148                         goto keeporig;
  149 
  150                 /*
  151                  * We now compare the vnode of the linux_root to the one
  152                  * vnode asked. If they resolve to be the same, then we
  153                  * ignore the match so that the real root gets used.
  154                  * This avoids the problem of traversing "../.." to find the
  155                  * root directory and never finding it, because "/" resolves
  156                  * to the emulation root directory. This is expensive :-(
  157                  */
  158                 NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, linux_emul_path,
  159                        td);
  160 
  161                 if ((error = namei(&ndroot)) != 0) {
  162                         /* Cannot happen! */
  163                         NDFREE(&nd, NDF_ONLY_PNBUF);
  164                         vrele(nd.ni_vp);
  165                         goto keeporig;
  166                 }
  167 
  168                 if ((error = VOP_GETATTR(nd.ni_vp, &vat, td->td_ucred, td)) != 0) {
  169                         goto bad;
  170                 }
  171 
  172                 if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, td->td_ucred, td))
  173                     != 0) {
  174                         goto bad;
  175                 }
  176 
  177                 if (vat.va_fsid == vatroot.va_fsid &&
  178                     vat.va_fileid == vatroot.va_fileid) {
  179                         error = ENOENT;
  180                         goto bad;
  181                 }
  182 
  183         }
  184 
  185         NDFREE(&nd, NDF_ONLY_PNBUF);
  186         vrele(nd.ni_vp);
  187         if (!cflag) {
  188                 NDFREE(&ndroot, NDF_ONLY_PNBUF);
  189                 vrele(ndroot.ni_vp);
  190         }
  191         return error;
  192 
  193 bad:
  194         NDFREE(&ndroot, NDF_ONLY_PNBUF);
  195         vrele(ndroot.ni_vp);
  196         NDFREE(&nd, NDF_ONLY_PNBUF);
  197         vrele(nd.ni_vp);
  198 keeporig:
  199         /* Keep the original path; copy it back to the start of the buffer. */
  200         bcopy(ptr, buf, len);
  201         return error;
  202 }

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FreeBSD/Linux Kernel Cross Reference sys/compat/linux/linux_util.c

FreeBSD/Linux Kernel Cross Reference
sys/compat/linux/linux_util.c