FreeBSD/Linux Kernel Cross Reference
sys/i386/linux/linux_util.c

     /*
      * Copyright (c) 1994 Christos Zoulas
      * Copyright (c) 1995 Frank van der Linden
      * Copyright (c) 1995 Scott Bartram
      * 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.
     *
     *      from: svr4_util.c,v 1.5 1995/01/22 23:44:50 christos Exp
     * $FreeBSD: src/sys/i386/linux/linux_util.c,v 1.3.2.1 1999/09/05 08:14:20 peter Exp $
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/namei.h>
    #include <sys/proc.h>
    #include <sys/file.h>
    #include <sys/stat.h>
    #include <sys/filedesc.h>
    #include <sys/ioctl.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/vnode.h>
    
    #include <i386/linux/linux_util.h>
    
    const char      linux_emul_path[] = "/compat/linux";
    
    /*
     * Search an alternate path before passing pathname arguments on
     * to system calls. Useful for keeping a seperate 'emulation tree'.
     *
     * If cflag is set, we check if an attempt can be made to create
     * the named file, i.e. we check if the directory it should
     * be in exists.
     */
    int
    linux_emul_find(p, sgp, prefix, path, pbuf, cflag)
            struct proc      *p;
            caddr_t          *sgp;          /* Pointer to stackgap memory */
            const char       *prefix;
            char             *path;
            char            **pbuf;
            int               cflag;
    {
            struct nameidata         nd;
            struct nameidata         ndroot;
            struct vattr             vat;
            struct vattr             vatroot;
            int                      error;
            char                    *ptr, *buf, *cp;
            size_t                   sz, len;
    
            buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
            *pbuf = path;
    
            for (ptr = buf; (*ptr = *prefix) != '\0'; ptr++, prefix++)
                    continue;
    
            sz = MAXPATHLEN - (ptr - buf);
    
            /* 
             * If sgp is not given then the path is already in kernel space
             */
            if (sgp == NULL)
                    error = copystr(path, ptr, sz, &len);
            else
                    error = copyinstr(path, ptr, sz, &len);
    
            if (error) {
                    free(buf, M_TEMP);
                    return error;
            }
    
            if (*ptr != '/') {
                    free(buf, M_TEMP);
                    return EINVAL;
            }
    
           /*
            * We know that there is a / somewhere in this pathname.
            * Search backwards for it, to find the file's parent dir
            * to see if it exists in the alternate tree. If it does,
            * and we want to create a file (cflag is set). We don't
            * need to worry about the root comparison in this case.
            */
   
           if (cflag) {
                   for (cp = &ptr[len] - 1; *cp != '/'; cp--);
                   *cp = '\0';
   
                   NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
   
                   if ((error = namei(&nd)) != 0) {
                           free(buf, M_TEMP);
                           return error;
                   }
   
                   *cp = '/';
           }
           else {
                   NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, buf, p);
   
                   if ((error = namei(&nd)) != 0) {
                           free(buf, M_TEMP);
                           return error;
                   }
   
                   /*
                    * We now compare the vnode of the linux_root to the one
                    * vnode asked. If they resolve to be the same, then we
                    * ignore the match so that the real root gets used.
                    * This avoids the problem of traversing "../.." to find the
                    * root directory and never finding it, because "/" resolves
                    * to the emulation root directory. This is expensive :-(
                    */
                   NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, linux_emul_path,
                          p);
   
                   if ((error = namei(&ndroot)) != 0) {
                           /* Cannot happen! */
                           free(buf, M_TEMP);
                           vrele(nd.ni_vp);
                           return error;
                   }
   
                   if ((error = VOP_GETATTR(nd.ni_vp, &vat, p->p_ucred, p)) != 0) {
                           goto bad;
                   }
   
                   if ((error = VOP_GETATTR(ndroot.ni_vp, &vatroot, p->p_ucred, p))
                       != 0) {
                           goto bad;
                   }
   
                   if (vat.va_fsid == vatroot.va_fsid &&
                       vat.va_fileid == vatroot.va_fileid) {
                           error = ENOENT;
                           goto bad;
                   }
   
           }
           if (sgp == NULL)
                   *pbuf = buf;
           else {
                   sz = &ptr[len] - buf;
                   *pbuf = stackgap_alloc(sgp, sz + 1);
                   error = copyout(buf, *pbuf, sz);
                   free(buf, M_TEMP);
           }
   
           vrele(nd.ni_vp);
           if (!cflag)
                   vrele(ndroot.ni_vp);
           return error;
   
   bad:
           vrele(ndroot.ni_vp);
           vrele(nd.ni_vp);
           free(buf, M_TEMP);
           return error;
   }

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