The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /* $FreeBSD: stable/4/sys/compat/linux/linux_getcwd.c 86095 2001-11-05 19:08:24Z marcel $ */
    2 /* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
    3 /* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
    4 
    5 /*-
    6  * Copyright (c) 1999 The NetBSD Foundation, Inc.
    7  * All rights reserved.
    8  *
    9  * This code is derived from software contributed to The NetBSD Foundation
   10  * by Bill Sommerfeld.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. All advertising materials mentioning features or use of this software
   21  *    must display the following acknowledgement:
   22  *        This product includes software developed by the NetBSD
   23  *        Foundation, Inc. and its contributors.
   24  * 4. Neither the name of The NetBSD Foundation nor the names of its
   25  *    contributors may be used to endorse or promote products derived
   26  *    from this software without specific prior written permission.
   27  *
   28  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   29  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   30  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   31  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   32  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   33  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   34  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   35  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   36  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   37  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   38  * POSSIBILITY OF SUCH DAMAGE.
   39  */
   40 #include "opt_compat.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/sysproto.h>
   45 #include <sys/namei.h>
   46 #include <sys/filedesc.h>
   47 #include <sys/kernel.h>
   48 #include <sys/file.h>
   49 #include <sys/stat.h>
   50 #include <sys/vnode.h>
   51 #include <sys/mount.h>
   52 #include <sys/proc.h>
   53 #include <sys/uio.h>
   54 #include <sys/malloc.h>
   55 #include <sys/dirent.h>
   56 #include <ufs/ufs/dir.h>        /* XXX only for DIRBLKSIZ */
   57 
   58 #include <machine/../linux/linux.h>
   59 #include <machine/../linux/linux_proto.h>
   60 #include <compat/linux/linux_util.h>
   61 
   62 static int
   63 linux_getcwd_scandir __P((struct vnode **, struct vnode **,
   64     char **, char *, struct proc *));
   65 static int
   66 linux_getcwd_common __P((struct vnode *, struct vnode *,
   67                    char **, char *, int, int, struct proc *));
   68 
   69 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
   70 
   71 /*
   72  * Vnode variable naming conventions in this file:
   73  *
   74  * rvp: the current root we're aiming towards.
   75  * lvp, *lvpp: the "lower" vnode
   76  * uvp, *uvpp: the "upper" vnode.
   77  *
   78  * Since all the vnodes we're dealing with are directories, and the
   79  * lookups are going *up* in the filesystem rather than *down*, the
   80  * usual "pvp" (parent) or "dvp" (directory) naming conventions are
   81  * too confusing.
   82  */
   83 
   84 /*
   85  * XXX Will infinite loop in certain cases if a directory read reliably
   86  *      returns EINVAL on last block.
   87  * XXX is EINVAL the right thing to return if a directory is malformed?
   88  */
   89 
   90 /*
   91  * XXX Untested vs. mount -o union; probably does the wrong thing.
   92  */
   93 
   94 /*
   95  * Find parent vnode of *lvpp, return in *uvpp
   96  *
   97  * If we care about the name, scan it looking for name of directory
   98  * entry pointing at lvp.
   99  *
  100  * Place the name in the buffer which starts at bufp, immediately
  101  * before *bpp, and move bpp backwards to point at the start of it.
  102  *
  103  * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
  104  * On exit, *uvpp is either NULL or is a locked vnode reference.
  105  */
  106 static int
  107 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, p)
  108         struct vnode **lvpp;
  109         struct vnode **uvpp;
  110         char **bpp;
  111         char *bufp;
  112         struct proc *p;
  113 {
  114         int     error = 0;
  115         int     eofflag;
  116         off_t   off;
  117         int     tries;
  118         struct uio uio;
  119         struct iovec iov;
  120         char   *dirbuf = NULL;
  121         int     dirbuflen;
  122         ino_t   fileno;
  123         struct vattr va;
  124         struct vnode *uvp = NULL;
  125         struct vnode *lvp = *lvpp;      
  126         struct componentname cn;
  127         int len, reclen;
  128         tries = 0;
  129 
  130         /*
  131          * If we want the filename, get some info we need while the
  132          * current directory is still locked.
  133          */
  134         if (bufp != NULL) {
  135                 error = VOP_GETATTR(lvp, &va, p->p_ucred, p);
  136                 if (error) {
  137                         vput(lvp);
  138                         *lvpp = NULL;
  139                         *uvpp = NULL;
  140                         return error;
  141                 }
  142         }
  143 
  144         /*
  145          * Ok, we have to do it the hard way..
  146          * Next, get parent vnode using lookup of ..
  147          */
  148         cn.cn_nameiop = LOOKUP;
  149         cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
  150         cn.cn_proc = p;
  151         cn.cn_cred = p->p_ucred;
  152         cn.cn_pnbuf = NULL;
  153         cn.cn_nameptr = "..";
  154         cn.cn_namelen = 2;
  155         cn.cn_consume = 0;
  156         
  157         /*
  158          * At this point, lvp is locked and will be unlocked by the lookup.
  159          * On successful return, *uvpp will be locked
  160          */
  161         error = VOP_LOOKUP(lvp, uvpp, &cn);
  162         if (error) {
  163                 vput(lvp);
  164                 *lvpp = NULL;
  165                 *uvpp = NULL;
  166                 return error;
  167         }
  168         uvp = *uvpp;
  169 
  170         /* If we don't care about the pathname, we're done */
  171         if (bufp == NULL) {
  172                 vrele(lvp);
  173                 *lvpp = NULL;
  174                 return 0;
  175         }
  176         
  177         fileno = va.va_fileid;
  178 
  179         dirbuflen = DIRBLKSIZ;
  180         if (dirbuflen < va.va_blocksize)
  181                 dirbuflen = va.va_blocksize;
  182         dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  183 
  184 #if 0
  185 unionread:
  186 #endif
  187         off = 0;
  188         do {
  189                 /* call VOP_READDIR of parent */
  190                 iov.iov_base = dirbuf;
  191                 iov.iov_len = dirbuflen;
  192 
  193                 uio.uio_iov = &iov;
  194                 uio.uio_iovcnt = 1;
  195                 uio.uio_offset = off;
  196                 uio.uio_resid = dirbuflen;
  197                 uio.uio_segflg = UIO_SYSSPACE;
  198                 uio.uio_rw = UIO_READ;
  199                 uio.uio_procp = p;
  200 
  201                 eofflag = 0;
  202 
  203                 error = VOP_READDIR(uvp, &uio, p->p_ucred, &eofflag, 0, 0);
  204 
  205                 off = uio.uio_offset;
  206 
  207                 /*
  208                  * Try again if NFS tosses its cookies.
  209                  * XXX this can still loop forever if the directory is busted
  210                  * such that the second or subsequent page of it always
  211                  * returns EINVAL
  212                  */
  213                 if ((error == EINVAL) && (tries < 3)) {
  214                         off = 0;
  215                         tries++;
  216                         continue;       /* once more, with feeling */
  217                 }
  218 
  219                 if (!error) {
  220                         char   *cpos;
  221                         struct dirent *dp;
  222                         
  223                         cpos = dirbuf;
  224                         tries = 0;
  225                                 
  226                         /* scan directory page looking for matching vnode */ 
  227                         for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
  228                                 dp = (struct dirent *) cpos;
  229                                 reclen = dp->d_reclen;
  230 
  231                                 /* check for malformed directory.. */
  232                                 if (reclen < DIRENT_MINSIZE) {
  233                                         error = EINVAL;
  234                                         goto out;
  235                                 }
  236                                 /*
  237                                  * XXX should perhaps do VOP_LOOKUP to
  238                                  * check that we got back to the right place,
  239                                  * but getting the locking games for that
  240                                  * right would be heinous.
  241                                  */
  242                                 if ((dp->d_type != DT_WHT) &&
  243                                     (dp->d_fileno == fileno)) {
  244                                         char *bp = *bpp;
  245                                         bp -= dp->d_namlen;
  246                                         
  247                                         if (bp <= bufp) {
  248                                                 error = ERANGE;
  249                                                 goto out;
  250                                         }
  251                                         bcopy(dp->d_name, bp, dp->d_namlen);
  252                                         error = 0;
  253                                         *bpp = bp;
  254                                         goto out;
  255                                 }
  256                                 cpos += reclen;
  257                         }
  258                 }
  259         } while (!eofflag);
  260         error = ENOENT;
  261                 
  262 out:
  263         vrele(lvp);
  264         *lvpp = NULL;
  265         free(dirbuf, M_TEMP);
  266         return error;
  267 }
  268 
  269 
  270 /*
  271  * common routine shared by sys___getcwd() and linux_vn_isunder()
  272  */
  273 
  274 #define GETCWD_CHECK_ACCESS 0x0001
  275 
  276 static int
  277 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, p)
  278         struct vnode *lvp;
  279         struct vnode *rvp;
  280         char **bpp;
  281         char *bufp;
  282         int limit;
  283         int flags;
  284         struct proc *p;
  285 {
  286         struct filedesc *fdp = p->p_fd;
  287         struct vnode *uvp = NULL;
  288         char *bp = NULL;
  289         int error;
  290         int perms = VEXEC;
  291 
  292         if (rvp == NULL) {
  293                 rvp = fdp->fd_rdir;
  294                 if (rvp == NULL)
  295                         rvp = rootvnode;
  296         }
  297         
  298         VREF(rvp);
  299         VREF(lvp);
  300 
  301         /*
  302          * Error handling invariant:
  303          * Before a `goto out':
  304          *      lvp is either NULL, or locked and held.
  305          *      uvp is either NULL, or locked and held.
  306          */
  307 
  308         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
  309         if (error) {
  310                 vrele(lvp);
  311                 lvp = NULL;
  312                 goto out;
  313         }
  314         if (bufp)
  315                 bp = *bpp;
  316         /*
  317          * this loop will terminate when one of the following happens:
  318          *      - we hit the root
  319          *      - getdirentries or lookup fails
  320          *      - we run out of space in the buffer.
  321          */
  322         if (lvp == rvp) {
  323                 if (bp)
  324                         *(--bp) = '/';
  325                 goto out;
  326         }
  327         do {
  328                 if (lvp->v_type != VDIR) {
  329                         error = ENOTDIR;
  330                         goto out;
  331                 }
  332                 
  333                 /*
  334                  * access check here is optional, depending on
  335                  * whether or not caller cares.
  336                  */
  337                 if (flags & GETCWD_CHECK_ACCESS) {
  338                         error = VOP_ACCESS(lvp, perms, p->p_ucred, p);
  339                         if (error)
  340                                 goto out;
  341                         perms = VEXEC|VREAD;
  342                 }
  343                 
  344                 /*
  345                  * step up if we're a covered vnode..
  346                  */
  347                 while (lvp->v_flag & VROOT) {
  348                         struct vnode *tvp;
  349 
  350                         if (lvp == rvp)
  351                                 goto out;
  352                         
  353                         tvp = lvp;
  354                         lvp = lvp->v_mount->mnt_vnodecovered;
  355                         vput(tvp);
  356                         /*
  357                          * hodie natus est radici frater
  358                          */
  359                         if (lvp == NULL) {
  360                                 error = ENOENT;
  361                                 goto out;
  362                         }
  363                         VREF(lvp);
  364                         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
  365                         if (error != 0) {
  366                                 vrele(lvp);
  367                                 lvp = NULL;
  368                                 goto out;
  369                         }
  370                 }
  371                 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, p);
  372                 if (error)
  373                         goto out;
  374 #if DIAGNOSTIC          
  375                 if (lvp != NULL)
  376                         panic("getcwd: oops, forgot to null lvp");
  377                 if (bufp && (bp <= bufp)) {
  378                         panic("getcwd: oops, went back too far");
  379                 }
  380 #endif          
  381                 if (bp) 
  382                         *(--bp) = '/';
  383                 lvp = uvp;
  384                 uvp = NULL;
  385                 limit--;
  386         } while ((lvp != rvp) && (limit > 0)); 
  387 
  388 out:
  389         if (bpp)
  390                 *bpp = bp;
  391         if (uvp)
  392                 vput(uvp);
  393         if (lvp)
  394                 vput(lvp);
  395         vrele(rvp);
  396         return error;
  397 }
  398 
  399 
  400 /*
  401  * Find pathname of process's current directory.
  402  *
  403  * Use vfs vnode-to-name reverse cache; if that fails, fall back
  404  * to reading directory contents.
  405  */
  406 
  407 int
  408 linux_getcwd(struct proc *p, struct linux_getcwd_args *args)
  409 {
  410         struct __getcwd_args bsd;
  411         caddr_t sg, bp, bend, path;
  412         int error, len, lenused;
  413 
  414 #ifdef DEBUG
  415         printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)p->p_pid,
  416                args->buf, args->bufsize);
  417 #endif
  418 
  419         sg = stackgap_init();
  420         bsd.buf = stackgap_alloc(&sg, SPARE_USRSPACE);
  421         bsd.buflen = SPARE_USRSPACE;
  422         error = __getcwd(p, &bsd);
  423         if (!error) {
  424                 lenused = strlen(bsd.buf) + 1;
  425                 if (lenused <= args->bufsize) {
  426                         p->p_retval[0] = lenused;
  427                         error = copyout(bsd.buf, args->buf, lenused);
  428                 }
  429                 else
  430                         error = ERANGE;
  431         } else {
  432                 len = args->bufsize;
  433 
  434                 if (len > MAXPATHLEN*4)
  435                         len = MAXPATHLEN*4;
  436                 else if (len < 2)
  437                         return ERANGE;
  438 
  439                 path = (char *)malloc(len, M_TEMP, M_WAITOK);
  440 
  441                 bp = &path[len];
  442                 bend = bp;
  443                 *(--bp) = '\0';
  444 
  445                 /*
  446                  * 5th argument here is "max number of vnodes to traverse".
  447                  * Since each entry takes up at least 2 bytes in the output buffer,
  448                  * limit it to N/2 vnodes for an N byte buffer.
  449                  */
  450 
  451                 error = linux_getcwd_common (p->p_fd->fd_cdir, NULL,
  452                     &bp, path, len/2, GETCWD_CHECK_ACCESS, p);
  453 
  454                 if (error)
  455                         goto out;
  456                 lenused = bend - bp;
  457                 p->p_retval[0] = lenused;
  458                 /* put the result into user buffer */
  459                 error = copyout(bp, args->buf, lenused);
  460 
  461 out:
  462                 free(path, M_TEMP);     
  463         }
  464         return (error);
  465 }
  466 

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