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 /* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
    2 /* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
    3 /*-
    4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * This code is derived from software contributed to The NetBSD Foundation
    8  * by Bill Sommerfeld.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. All advertising materials mentioning features or use of this software
   19  *    must display the following acknowledgement:
   20  *        This product includes software developed by the NetBSD
   21  *        Foundation, Inc. and its contributors.
   22  * 4. Neither the name of The NetBSD Foundation nor the names of its
   23  *    contributors may be used to endorse or promote products derived
   24  *    from this software without specific prior written permission.
   25  *
   26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   36  * POSSIBILITY OF SUCH DAMAGE.
   37  */
   38 
   39 #include <sys/cdefs.h>
   40 __FBSDID("$FreeBSD: releng/8.0/sys/compat/linux/linux_getcwd.c 193511 2009-06-05 14:55:22Z rwatson $");
   41 
   42 #include "opt_compat.h"
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/namei.h>
   47 #include <sys/filedesc.h>
   48 #include <sys/kernel.h>
   49 #include <sys/file.h>
   50 #include <sys/stat.h>
   51 #include <sys/syscallsubr.h>
   52 #include <sys/vnode.h>
   53 #include <sys/mount.h>
   54 #include <sys/proc.h>
   55 #include <sys/uio.h>
   56 #include <sys/malloc.h>
   57 #include <sys/dirent.h>
   58 #include <ufs/ufs/dir.h>        /* XXX only for DIRBLKSIZ */
   59 
   60 #ifdef COMPAT_LINUX32
   61 #include <machine/../linux32/linux.h>
   62 #include <machine/../linux32/linux32_proto.h>
   63 #else
   64 #include <machine/../linux/linux.h>
   65 #include <machine/../linux/linux_proto.h>
   66 #endif
   67 #include <compat/linux/linux_util.h>
   68 
   69 #include <security/mac/mac_framework.h>
   70 
   71 static int
   72 linux_getcwd_scandir(struct vnode **, struct vnode **,
   73     char **, char *, struct thread *);
   74 static int
   75 linux_getcwd_common(struct vnode *, struct vnode *,
   76                    char **, char *, int, int, struct thread *);
   77 
   78 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
   79 
   80 /*
   81  * Vnode variable naming conventions in this file:
   82  *
   83  * rvp: the current root we're aiming towards.
   84  * lvp, *lvpp: the "lower" vnode
   85  * uvp, *uvpp: the "upper" vnode.
   86  *
   87  * Since all the vnodes we're dealing with are directories, and the
   88  * lookups are going *up* in the filesystem rather than *down*, the
   89  * usual "pvp" (parent) or "dvp" (directory) naming conventions are
   90  * too confusing.
   91  */
   92 
   93 /*
   94  * XXX Will infinite loop in certain cases if a directory read reliably
   95  *      returns EINVAL on last block.
   96  * XXX is EINVAL the right thing to return if a directory is malformed?
   97  */
   98 
   99 /*
  100  * XXX Untested vs. mount -o union; probably does the wrong thing.
  101  */
  102 
  103 /*
  104  * Find parent vnode of *lvpp, return in *uvpp
  105  *
  106  * If we care about the name, scan it looking for name of directory
  107  * entry pointing at lvp.
  108  *
  109  * Place the name in the buffer which starts at bufp, immediately
  110  * before *bpp, and move bpp backwards to point at the start of it.
  111  *
  112  * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
  113  * On exit, *uvpp is either NULL or is a locked vnode reference.
  114  */
  115 static int
  116 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
  117         struct vnode **lvpp;
  118         struct vnode **uvpp;
  119         char **bpp;
  120         char *bufp;
  121         struct thread *td;
  122 {
  123         int     error = 0;
  124         int     eofflag;
  125         off_t   off;
  126         int     tries;
  127         struct uio uio;
  128         struct iovec iov;
  129         char   *dirbuf = NULL;
  130         int     dirbuflen;
  131         ino_t   fileno;
  132         struct vattr va;
  133         struct vnode *uvp = NULL;
  134         struct vnode *lvp = *lvpp;      
  135         struct componentname cn;
  136         int len, reclen;
  137         tries = 0;
  138 
  139         /*
  140          * If we want the filename, get some info we need while the
  141          * current directory is still locked.
  142          */
  143         if (bufp != NULL) {
  144                 error = VOP_GETATTR(lvp, &va, td->td_ucred);
  145                 if (error) {
  146                         vput(lvp);
  147                         *lvpp = NULL;
  148                         *uvpp = NULL;
  149                         return error;
  150                 }
  151         }
  152 
  153         /*
  154          * Ok, we have to do it the hard way..
  155          * Next, get parent vnode using lookup of ..
  156          */
  157         cn.cn_nameiop = LOOKUP;
  158         cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
  159         cn.cn_thread = td;
  160         cn.cn_cred = td->td_ucred;
  161         cn.cn_pnbuf = NULL;
  162         cn.cn_nameptr = "..";
  163         cn.cn_namelen = 2;
  164         cn.cn_consume = 0;
  165         cn.cn_lkflags = LK_SHARED;
  166         
  167         /*
  168          * At this point, lvp is locked and will be unlocked by the lookup.
  169          * On successful return, *uvpp will be locked
  170          */
  171 #ifdef MAC
  172         error = mac_vnode_check_lookup(td->td_ucred, lvp, &cn);
  173         if (error == 0)
  174 #endif
  175                 error = VOP_LOOKUP(lvp, uvpp, &cn);
  176         if (error) {
  177                 vput(lvp);
  178                 *lvpp = NULL;
  179                 *uvpp = NULL;
  180                 return error;
  181         }
  182         uvp = *uvpp;
  183 
  184         /* If we don't care about the pathname, we're done */
  185         if (bufp == NULL) {
  186                 vput(lvp);
  187                 *lvpp = NULL;
  188                 return 0;
  189         }
  190         
  191         fileno = va.va_fileid;
  192 
  193         dirbuflen = DIRBLKSIZ;
  194         if (dirbuflen < va.va_blocksize)
  195                 dirbuflen = va.va_blocksize;
  196         dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  197 
  198 #if 0
  199 unionread:
  200 #endif
  201         off = 0;
  202         do {
  203                 /* call VOP_READDIR of parent */
  204                 iov.iov_base = dirbuf;
  205                 iov.iov_len = dirbuflen;
  206 
  207                 uio.uio_iov = &iov;
  208                 uio.uio_iovcnt = 1;
  209                 uio.uio_offset = off;
  210                 uio.uio_resid = dirbuflen;
  211                 uio.uio_segflg = UIO_SYSSPACE;
  212                 uio.uio_rw = UIO_READ;
  213                 uio.uio_td = td;
  214 
  215                 eofflag = 0;
  216 
  217 #ifdef MAC
  218                 error = mac_vnode_check_readdir(td->td_ucred, uvp);
  219                 if (error == 0)
  220 #endif /* MAC */
  221                         error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
  222                             0, 0);
  223 
  224                 off = uio.uio_offset;
  225 
  226                 /*
  227                  * Try again if NFS tosses its cookies.
  228                  * XXX this can still loop forever if the directory is busted
  229                  * such that the second or subsequent page of it always
  230                  * returns EINVAL
  231                  */
  232                 if ((error == EINVAL) && (tries < 3)) {
  233                         off = 0;
  234                         tries++;
  235                         continue;       /* once more, with feeling */
  236                 }
  237 
  238                 if (!error) {
  239                         char   *cpos;
  240                         struct dirent *dp;
  241                         
  242                         cpos = dirbuf;
  243                         tries = 0;
  244                                 
  245                         /* scan directory page looking for matching vnode */ 
  246                         for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
  247                                 dp = (struct dirent *) cpos;
  248                                 reclen = dp->d_reclen;
  249 
  250                                 /* check for malformed directory.. */
  251                                 if (reclen < DIRENT_MINSIZE) {
  252                                         error = EINVAL;
  253                                         goto out;
  254                                 }
  255                                 /*
  256                                  * XXX should perhaps do VOP_LOOKUP to
  257                                  * check that we got back to the right place,
  258                                  * but getting the locking games for that
  259                                  * right would be heinous.
  260                                  */
  261                                 if ((dp->d_type != DT_WHT) &&
  262                                     (dp->d_fileno == fileno)) {
  263                                         char *bp = *bpp;
  264                                         bp -= dp->d_namlen;
  265                                         
  266                                         if (bp <= bufp) {
  267                                                 error = ERANGE;
  268                                                 goto out;
  269                                         }
  270                                         bcopy(dp->d_name, bp, dp->d_namlen);
  271                                         error = 0;
  272                                         *bpp = bp;
  273                                         goto out;
  274                                 }
  275                                 cpos += reclen;
  276                         }
  277                 }
  278         } while (!eofflag);
  279         error = ENOENT;
  280                 
  281 out:
  282         vput(lvp);
  283         *lvpp = NULL;
  284         free(dirbuf, M_TEMP);
  285         return error;
  286 }
  287 
  288 
  289 /*
  290  * common routine shared by sys___getcwd() and linux_vn_isunder()
  291  */
  292 
  293 #define GETCWD_CHECK_ACCESS 0x0001
  294 
  295 static int
  296 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
  297         struct vnode *lvp;
  298         struct vnode *rvp;
  299         char **bpp;
  300         char *bufp;
  301         int limit;
  302         int flags;
  303         struct thread *td;
  304 {
  305         struct filedesc *fdp = td->td_proc->p_fd;
  306         struct vnode *uvp = NULL;
  307         char *bp = NULL;
  308         int error;
  309         accmode_t accmode = VEXEC;
  310 
  311         if (rvp == NULL) {
  312                 rvp = fdp->fd_rdir;
  313                 if (rvp == NULL)
  314                         rvp = rootvnode;
  315         }
  316         
  317         VREF(rvp);
  318         VREF(lvp);
  319 
  320         /*
  321          * Error handling invariant:
  322          * Before a `goto out':
  323          *      lvp is either NULL, or locked and held.
  324          *      uvp is either NULL, or locked and held.
  325          */
  326 
  327         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
  328         if (error != 0)
  329                 panic("vn_lock LK_RETRY returned error %d", error);
  330         if (bufp)
  331                 bp = *bpp;
  332         /*
  333          * this loop will terminate when one of the following happens:
  334          *      - we hit the root
  335          *      - getdirentries or lookup fails
  336          *      - we run out of space in the buffer.
  337          */
  338         if (lvp == rvp) {
  339                 if (bp)
  340                         *(--bp) = '/';
  341                 goto out;
  342         }
  343         do {
  344                 if (lvp->v_type != VDIR) {
  345                         error = ENOTDIR;
  346                         goto out;
  347                 }
  348                 
  349                 /*
  350                  * access check here is optional, depending on
  351                  * whether or not caller cares.
  352                  */
  353                 if (flags & GETCWD_CHECK_ACCESS) {
  354                         error = VOP_ACCESS(lvp, accmode, td->td_ucred, td);
  355                         if (error)
  356                                 goto out;
  357                         accmode = VEXEC|VREAD;
  358                 }
  359                 
  360                 /*
  361                  * step up if we're a covered vnode..
  362                  */
  363                 while (lvp->v_vflag & VV_ROOT) {
  364                         struct vnode *tvp;
  365 
  366                         if (lvp == rvp)
  367                                 goto out;
  368                         
  369                         tvp = lvp;
  370                         lvp = lvp->v_mount->mnt_vnodecovered;
  371                         vput(tvp);
  372                         /*
  373                          * hodie natus est radici frater
  374                          */
  375                         if (lvp == NULL) {
  376                                 error = ENOENT;
  377                                 goto out;
  378                         }
  379                         VREF(lvp);
  380                         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY);
  381                         if (error != 0)
  382                                 panic("vn_lock LK_RETRY returned %d", error);
  383                 }
  384                 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
  385                 if (error)
  386                         goto out;
  387 #ifdef DIAGNOSTIC               
  388                 if (lvp != NULL)
  389                         panic("getcwd: oops, forgot to null lvp");
  390                 if (bufp && (bp <= bufp)) {
  391                         panic("getcwd: oops, went back too far");
  392                 }
  393 #endif          
  394                 if (bp) 
  395                         *(--bp) = '/';
  396                 lvp = uvp;
  397                 uvp = NULL;
  398                 limit--;
  399         } while ((lvp != rvp) && (limit > 0)); 
  400 
  401 out:
  402         if (bpp)
  403                 *bpp = bp;
  404         if (uvp)
  405                 vput(uvp);
  406         if (lvp)
  407                 vput(lvp);
  408         vrele(rvp);
  409         return error;
  410 }
  411 
  412 
  413 /*
  414  * Find pathname of process's current directory.
  415  *
  416  * Use vfs vnode-to-name reverse cache; if that fails, fall back
  417  * to reading directory contents.
  418  */
  419 
  420 int
  421 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
  422 {
  423         caddr_t bp, bend, path;
  424         int error, len, lenused;
  425 
  426 #ifdef DEBUG
  427         if (ldebug(getcwd))
  428                 printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
  429 #endif
  430 
  431         len = args->bufsize;
  432 
  433         if (len > MAXPATHLEN*4)
  434                 len = MAXPATHLEN*4;
  435         else if (len < 2)
  436                 return ERANGE;
  437 
  438         path = (char *)malloc(len, M_TEMP, M_WAITOK);
  439 
  440         error = kern___getcwd(td, path, UIO_SYSSPACE, len);
  441         if (!error) {
  442                 lenused = strlen(path) + 1;
  443                 if (lenused <= args->bufsize) {
  444                         td->td_retval[0] = lenused;
  445                         error = copyout(path, args->buf, lenused);
  446                 }
  447                 else
  448                         error = ERANGE;
  449         } else {
  450                 bp = &path[len];
  451                 bend = bp;
  452                 *(--bp) = '\0';
  453 
  454                 /*
  455                  * 5th argument here is "max number of vnodes to traverse".
  456                  * Since each entry takes up at least 2 bytes in the output buffer,
  457                  * limit it to N/2 vnodes for an N byte buffer.
  458                  */
  459 
  460                 mtx_lock(&Giant);
  461                 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
  462                     &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
  463                 mtx_unlock(&Giant);
  464 
  465                 if (error)
  466                         goto out;
  467                 lenused = bend - bp;
  468                 td->td_retval[0] = lenused;
  469                 /* put the result into user buffer */
  470                 error = copyout(bp, args->buf, lenused);
  471         }
  472 out:
  473         free(path, M_TEMP);
  474         return (error);
  475 }
  476 

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