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/6.3/sys/compat/linux/linux_getcwd.c 171299 2007-07-08 08:41:09Z netchild $");
   41 
   42 #include "opt_compat.h"
   43 #include "opt_mac.h"
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/namei.h>
   48 #include <sys/filedesc.h>
   49 #include <sys/kernel.h>
   50 #include <sys/file.h>
   51 #include <sys/stat.h>
   52 #include <sys/syscallsubr.h>
   53 #include <sys/vnode.h>
   54 #include <sys/mount.h>
   55 #include <sys/proc.h>
   56 #include <sys/uio.h>
   57 #include <sys/mac.h>
   58 #include <sys/malloc.h>
   59 #include <sys/dirent.h>
   60 #include <ufs/ufs/dir.h>        /* XXX only for DIRBLKSIZ */
   61 
   62 #include "opt_compat.h"
   63 
   64 #ifdef COMPAT_LINUX32
   65 #include <machine/../linux32/linux.h>
   66 #include <machine/../linux32/linux32_proto.h>
   67 #else
   68 #include <machine/../linux/linux.h>
   69 #include <machine/../linux/linux_proto.h>
   70 #endif
   71 #include <compat/linux/linux_util.h>
   72 
   73 static int
   74 linux_getcwd_scandir(struct vnode **, struct vnode **,
   75     char **, char *, struct thread *);
   76 static int
   77 linux_getcwd_common(struct vnode *, struct vnode *,
   78                    char **, char *, int, int, struct thread *);
   79 
   80 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
   81 
   82 /*
   83  * Vnode variable naming conventions in this file:
   84  *
   85  * rvp: the current root we're aiming towards.
   86  * lvp, *lvpp: the "lower" vnode
   87  * uvp, *uvpp: the "upper" vnode.
   88  *
   89  * Since all the vnodes we're dealing with are directories, and the
   90  * lookups are going *up* in the filesystem rather than *down*, the
   91  * usual "pvp" (parent) or "dvp" (directory) naming conventions are
   92  * too confusing.
   93  */
   94 
   95 /*
   96  * XXX Will infinite loop in certain cases if a directory read reliably
   97  *      returns EINVAL on last block.
   98  * XXX is EINVAL the right thing to return if a directory is malformed?
   99  */
  100 
  101 /*
  102  * XXX Untested vs. mount -o union; probably does the wrong thing.
  103  */
  104 
  105 /*
  106  * Find parent vnode of *lvpp, return in *uvpp
  107  *
  108  * If we care about the name, scan it looking for name of directory
  109  * entry pointing at lvp.
  110  *
  111  * Place the name in the buffer which starts at bufp, immediately
  112  * before *bpp, and move bpp backwards to point at the start of it.
  113  *
  114  * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
  115  * On exit, *uvpp is either NULL or is a locked vnode reference.
  116  */
  117 static int
  118 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
  119         struct vnode **lvpp;
  120         struct vnode **uvpp;
  121         char **bpp;
  122         char *bufp;
  123         struct thread *td;
  124 {
  125         int     error = 0;
  126         int     eofflag;
  127         off_t   off;
  128         int     tries;
  129         struct uio uio;
  130         struct iovec iov;
  131         char   *dirbuf = NULL;
  132         int     dirbuflen;
  133         ino_t   fileno;
  134         struct vattr va;
  135         struct vnode *uvp = NULL;
  136         struct vnode *lvp = *lvpp;      
  137         struct componentname cn;
  138         int len, reclen;
  139         tries = 0;
  140 
  141         /*
  142          * If we want the filename, get some info we need while the
  143          * current directory is still locked.
  144          */
  145         if (bufp != NULL) {
  146                 error = VOP_GETATTR(lvp, &va, td->td_ucred, td);
  147                 if (error) {
  148                         vput(lvp);
  149                         *lvpp = NULL;
  150                         *uvpp = NULL;
  151                         return error;
  152                 }
  153         }
  154 
  155         /*
  156          * Ok, we have to do it the hard way..
  157          * Next, get parent vnode using lookup of ..
  158          */
  159         cn.cn_nameiop = LOOKUP;
  160         cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
  161         cn.cn_thread = td;
  162         cn.cn_cred = td->td_ucred;
  163         cn.cn_pnbuf = NULL;
  164         cn.cn_nameptr = "..";
  165         cn.cn_namelen = 2;
  166         cn.cn_consume = 0;
  167         cn.cn_lkflags = LK_EXCLUSIVE;
  168         
  169         /*
  170          * At this point, lvp is locked and will be unlocked by the lookup.
  171          * On successful return, *uvpp will be locked
  172          */
  173 #ifdef MAC
  174         error = mac_check_vnode_lookup(td->td_ucred, lvp, &cn);
  175         if (error == 0)
  176 #endif
  177                 error = VOP_LOOKUP(lvp, uvpp, &cn);
  178         if (error) {
  179                 vput(lvp);
  180                 *lvpp = NULL;
  181                 *uvpp = NULL;
  182                 return error;
  183         }
  184         uvp = *uvpp;
  185 
  186         /* If we don't care about the pathname, we're done */
  187         if (bufp == NULL) {
  188                 vput(lvp);
  189                 *lvpp = NULL;
  190                 return 0;
  191         }
  192         
  193         fileno = va.va_fileid;
  194 
  195         dirbuflen = DIRBLKSIZ;
  196         if (dirbuflen < va.va_blocksize)
  197                 dirbuflen = va.va_blocksize;
  198         dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  199 
  200 #if 0
  201 unionread:
  202 #endif
  203         off = 0;
  204         do {
  205                 /* call VOP_READDIR of parent */
  206                 iov.iov_base = dirbuf;
  207                 iov.iov_len = dirbuflen;
  208 
  209                 uio.uio_iov = &iov;
  210                 uio.uio_iovcnt = 1;
  211                 uio.uio_offset = off;
  212                 uio.uio_resid = dirbuflen;
  213                 uio.uio_segflg = UIO_SYSSPACE;
  214                 uio.uio_rw = UIO_READ;
  215                 uio.uio_td = td;
  216 
  217                 eofflag = 0;
  218 
  219 #ifdef MAC
  220                 error = mac_check_vnode_readdir(td->td_ucred, uvp);
  221                 if (error == 0)
  222 #endif /* MAC */
  223                         error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
  224                             0, 0);
  225 
  226                 off = uio.uio_offset;
  227 
  228                 /*
  229                  * Try again if NFS tosses its cookies.
  230                  * XXX this can still loop forever if the directory is busted
  231                  * such that the second or subsequent page of it always
  232                  * returns EINVAL
  233                  */
  234                 if ((error == EINVAL) && (tries < 3)) {
  235                         off = 0;
  236                         tries++;
  237                         continue;       /* once more, with feeling */
  238                 }
  239 
  240                 if (!error) {
  241                         char   *cpos;
  242                         struct dirent *dp;
  243                         
  244                         cpos = dirbuf;
  245                         tries = 0;
  246                                 
  247                         /* scan directory page looking for matching vnode */ 
  248                         for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
  249                                 dp = (struct dirent *) cpos;
  250                                 reclen = dp->d_reclen;
  251 
  252                                 /* check for malformed directory.. */
  253                                 if (reclen < DIRENT_MINSIZE) {
  254                                         error = EINVAL;
  255                                         goto out;
  256                                 }
  257                                 /*
  258                                  * XXX should perhaps do VOP_LOOKUP to
  259                                  * check that we got back to the right place,
  260                                  * but getting the locking games for that
  261                                  * right would be heinous.
  262                                  */
  263                                 if ((dp->d_type != DT_WHT) &&
  264                                     (dp->d_fileno == fileno)) {
  265                                         char *bp = *bpp;
  266                                         bp -= dp->d_namlen;
  267                                         
  268                                         if (bp <= bufp) {
  269                                                 error = ERANGE;
  270                                                 goto out;
  271                                         }
  272                                         bcopy(dp->d_name, bp, dp->d_namlen);
  273                                         error = 0;
  274                                         *bpp = bp;
  275                                         goto out;
  276                                 }
  277                                 cpos += reclen;
  278                         }
  279                 }
  280         } while (!eofflag);
  281         error = ENOENT;
  282                 
  283 out:
  284         vput(lvp);
  285         *lvpp = NULL;
  286         free(dirbuf, M_TEMP);
  287         return error;
  288 }
  289 
  290 
  291 /*
  292  * common routine shared by sys___getcwd() and linux_vn_isunder()
  293  */
  294 
  295 #define GETCWD_CHECK_ACCESS 0x0001
  296 
  297 static int
  298 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
  299         struct vnode *lvp;
  300         struct vnode *rvp;
  301         char **bpp;
  302         char *bufp;
  303         int limit;
  304         int flags;
  305         struct thread *td;
  306 {
  307         struct filedesc *fdp = td->td_proc->p_fd;
  308         struct vnode *uvp = NULL;
  309         char *bp = NULL;
  310         int error;
  311         int perms = VEXEC;
  312 
  313         if (rvp == NULL) {
  314                 rvp = fdp->fd_rdir;
  315                 if (rvp == NULL)
  316                         rvp = rootvnode;
  317         }
  318         
  319         VREF(rvp);
  320         VREF(lvp);
  321 
  322         /*
  323          * Error handling invariant:
  324          * Before a `goto out':
  325          *      lvp is either NULL, or locked and held.
  326          *      uvp is either NULL, or locked and held.
  327          */
  328 
  329         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  330         if (error != 0)
  331                 panic("vn_lock LK_RETRY returned error %d", error);
  332         if (bufp)
  333                 bp = *bpp;
  334         /*
  335          * this loop will terminate when one of the following happens:
  336          *      - we hit the root
  337          *      - getdirentries or lookup fails
  338          *      - we run out of space in the buffer.
  339          */
  340         if (lvp == rvp) {
  341                 if (bp)
  342                         *(--bp) = '/';
  343                 goto out;
  344         }
  345         do {
  346                 if (lvp->v_type != VDIR) {
  347                         error = ENOTDIR;
  348                         goto out;
  349                 }
  350                 
  351                 /*
  352                  * access check here is optional, depending on
  353                  * whether or not caller cares.
  354                  */
  355                 if (flags & GETCWD_CHECK_ACCESS) {
  356                         error = VOP_ACCESS(lvp, perms, td->td_ucred, td);
  357                         if (error)
  358                                 goto out;
  359                         perms = VEXEC|VREAD;
  360                 }
  361                 
  362                 /*
  363                  * step up if we're a covered vnode..
  364                  */
  365                 while (lvp->v_vflag & VV_ROOT) {
  366                         struct vnode *tvp;
  367 
  368                         if (lvp == rvp)
  369                                 goto out;
  370                         
  371                         tvp = lvp;
  372                         lvp = lvp->v_mount->mnt_vnodecovered;
  373                         vput(tvp);
  374                         /*
  375                          * hodie natus est radici frater
  376                          */
  377                         if (lvp == NULL) {
  378                                 error = ENOENT;
  379                                 goto out;
  380                         }
  381                         VREF(lvp);
  382                         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  383                         if (error != 0)
  384                                 panic("vn_lock LK_RETRY returned %d", error);
  385                 }
  386                 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
  387                 if (error)
  388                         goto out;
  389 #ifdef DIAGNOSTIC               
  390                 if (lvp != NULL)
  391                         panic("getcwd: oops, forgot to null lvp");
  392                 if (bufp && (bp <= bufp)) {
  393                         panic("getcwd: oops, went back too far");
  394                 }
  395 #endif          
  396                 if (bp) 
  397                         *(--bp) = '/';
  398                 lvp = uvp;
  399                 uvp = NULL;
  400                 limit--;
  401         } while ((lvp != rvp) && (limit > 0)); 
  402 
  403 out:
  404         if (bpp)
  405                 *bpp = bp;
  406         if (uvp)
  407                 vput(uvp);
  408         if (lvp)
  409                 vput(lvp);
  410         vrele(rvp);
  411         return error;
  412 }
  413 
  414 
  415 /*
  416  * Find pathname of process's current directory.
  417  *
  418  * Use vfs vnode-to-name reverse cache; if that fails, fall back
  419  * to reading directory contents.
  420  */
  421 
  422 int
  423 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
  424 {
  425         caddr_t bp, bend, path;
  426         int error, len, lenused;
  427 
  428 #ifdef DEBUG
  429         if (ldebug(getcwd))
  430                 printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
  431 #endif
  432 
  433         len = args->bufsize;
  434 
  435         if (len > MAXPATHLEN*4)
  436                 len = MAXPATHLEN*4;
  437         else if (len < 2)
  438                 return ERANGE;
  439 
  440         path = (char *)malloc(len, M_TEMP, M_WAITOK);
  441 
  442         error = kern___getcwd(td, path, UIO_SYSSPACE, len);
  443         if (!error) {
  444                 lenused = strlen(path) + 1;
  445                 if (lenused <= args->bufsize) {
  446                         td->td_retval[0] = lenused;
  447                         error = copyout(path, args->buf, lenused);
  448                 }
  449                 else
  450                         error = ERANGE;
  451         } else {
  452                 bp = &path[len];
  453                 bend = bp;
  454                 *(--bp) = '\0';
  455 
  456                 /*
  457                  * 5th argument here is "max number of vnodes to traverse".
  458                  * Since each entry takes up at least 2 bytes in the output buffer,
  459                  * limit it to N/2 vnodes for an N byte buffer.
  460                  */
  461 
  462                 mtx_lock(&Giant);
  463                 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
  464                     &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
  465                 mtx_unlock(&Giant);
  466 
  467                 if (error)
  468                         goto out;
  469                 lenused = bend - bp;
  470                 td->td_retval[0] = lenused;
  471                 /* put the result into user buffer */
  472                 error = copyout(bp, args->buf, lenused);
  473         }
  474 out:
  475         free(path, M_TEMP);
  476         return (error);
  477 }
  478 

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