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/7.3/sys/compat/linux/linux_getcwd.c 189991 2009-03-18 21:51:02Z jhb $");
   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/malloc.h>
   58 #include <sys/dirent.h>
   59 #include <ufs/ufs/dir.h>        /* XXX only for DIRBLKSIZ */
   60 
   61 #ifdef COMPAT_LINUX32
   62 #include <machine/../linux32/linux.h>
   63 #include <machine/../linux32/linux32_proto.h>
   64 #else
   65 #include <machine/../linux/linux.h>
   66 #include <machine/../linux/linux_proto.h>
   67 #endif
   68 #include <compat/linux/linux_util.h>
   69 
   70 #include <security/mac/mac_framework.h>
   71 
   72 static int
   73 linux_getcwd_scandir(struct vnode **, struct vnode **,
   74     char **, char *, struct thread *);
   75 static int
   76 linux_getcwd_common(struct vnode *, struct vnode *,
   77                    char **, char *, int, int, struct thread *);
   78 
   79 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
   80 
   81 /*
   82  * Vnode variable naming conventions in this file:
   83  *
   84  * rvp: the current root we're aiming towards.
   85  * lvp, *lvpp: the "lower" vnode
   86  * uvp, *uvpp: the "upper" vnode.
   87  *
   88  * Since all the vnodes we're dealing with are directories, and the
   89  * lookups are going *up* in the filesystem rather than *down*, the
   90  * usual "pvp" (parent) or "dvp" (directory) naming conventions are
   91  * too confusing.
   92  */
   93 
   94 /*
   95  * XXX Will infinite loop in certain cases if a directory read reliably
   96  *      returns EINVAL on last block.
   97  * XXX is EINVAL the right thing to return if a directory is malformed?
   98  */
   99 
  100 /*
  101  * XXX Untested vs. mount -o union; probably does the wrong thing.
  102  */
  103 
  104 /*
  105  * Find parent vnode of *lvpp, return in *uvpp
  106  *
  107  * If we care about the name, scan it looking for name of directory
  108  * entry pointing at lvp.
  109  *
  110  * Place the name in the buffer which starts at bufp, immediately
  111  * before *bpp, and move bpp backwards to point at the start of it.
  112  *
  113  * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
  114  * On exit, *uvpp is either NULL or is a locked vnode reference.
  115  */
  116 static int
  117 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
  118         struct vnode **lvpp;
  119         struct vnode **uvpp;
  120         char **bpp;
  121         char *bufp;
  122         struct thread *td;
  123 {
  124         int     error = 0;
  125         int     eofflag;
  126         off_t   off;
  127         int     tries;
  128         struct uio uio;
  129         struct iovec iov;
  130         char   *dirbuf = NULL;
  131         int     dirbuflen;
  132         ino_t   fileno;
  133         struct vattr va;
  134         struct vnode *uvp = NULL;
  135         struct vnode *lvp = *lvpp;      
  136         struct componentname cn;
  137         int len, reclen;
  138         tries = 0;
  139 
  140         /*
  141          * If we want the filename, get some info we need while the
  142          * current directory is still locked.
  143          */
  144         if (bufp != NULL) {
  145                 error = VOP_GETATTR(lvp, &va, td->td_ucred, td);
  146                 if (error) {
  147                         vput(lvp);
  148                         *lvpp = NULL;
  149                         *uvpp = NULL;
  150                         return error;
  151                 }
  152         }
  153 
  154         /*
  155          * Ok, we have to do it the hard way..
  156          * Next, get parent vnode using lookup of ..
  157          */
  158         cn.cn_nameiop = LOOKUP;
  159         cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
  160         cn.cn_thread = td;
  161         cn.cn_cred = td->td_ucred;
  162         cn.cn_pnbuf = NULL;
  163         cn.cn_nameptr = "..";
  164         cn.cn_namelen = 2;
  165         cn.cn_consume = 0;
  166         cn.cn_lkflags = LK_SHARED;
  167         
  168         /*
  169          * At this point, lvp is locked and will be unlocked by the lookup.
  170          * On successful return, *uvpp will be locked
  171          */
  172 #ifdef MAC
  173         error = mac_check_vnode_lookup(td->td_ucred, lvp, &cn);
  174         if (error == 0)
  175 #endif
  176                 error = VOP_LOOKUP(lvp, uvpp, &cn);
  177         if (error) {
  178                 vput(lvp);
  179                 *lvpp = NULL;
  180                 *uvpp = NULL;
  181                 return error;
  182         }
  183         uvp = *uvpp;
  184 
  185         /* If we don't care about the pathname, we're done */
  186         if (bufp == NULL) {
  187                 vput(lvp);
  188                 *lvpp = NULL;
  189                 return 0;
  190         }
  191         
  192         fileno = va.va_fileid;
  193 
  194         dirbuflen = DIRBLKSIZ;
  195         if (dirbuflen < va.va_blocksize)
  196                 dirbuflen = va.va_blocksize;
  197         dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  198 
  199 #if 0
  200 unionread:
  201 #endif
  202         off = 0;
  203         do {
  204                 /* call VOP_READDIR of parent */
  205                 iov.iov_base = dirbuf;
  206                 iov.iov_len = dirbuflen;
  207 
  208                 uio.uio_iov = &iov;
  209                 uio.uio_iovcnt = 1;
  210                 uio.uio_offset = off;
  211                 uio.uio_resid = dirbuflen;
  212                 uio.uio_segflg = UIO_SYSSPACE;
  213                 uio.uio_rw = UIO_READ;
  214                 uio.uio_td = td;
  215 
  216                 eofflag = 0;
  217 
  218 #ifdef MAC
  219                 error = mac_check_vnode_readdir(td->td_ucred, uvp);
  220                 if (error == 0)
  221 #endif /* MAC */
  222                         error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
  223                             0, 0);
  224 
  225                 off = uio.uio_offset;
  226 
  227                 /*
  228                  * Try again if NFS tosses its cookies.
  229                  * XXX this can still loop forever if the directory is busted
  230                  * such that the second or subsequent page of it always
  231                  * returns EINVAL
  232                  */
  233                 if ((error == EINVAL) && (tries < 3)) {
  234                         off = 0;
  235                         tries++;
  236                         continue;       /* once more, with feeling */
  237                 }
  238 
  239                 if (!error) {
  240                         char   *cpos;
  241                         struct dirent *dp;
  242                         
  243                         cpos = dirbuf;
  244                         tries = 0;
  245                                 
  246                         /* scan directory page looking for matching vnode */ 
  247                         for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
  248                                 dp = (struct dirent *) cpos;
  249                                 reclen = dp->d_reclen;
  250 
  251                                 /* check for malformed directory.. */
  252                                 if (reclen < DIRENT_MINSIZE) {
  253                                         error = EINVAL;
  254                                         goto out;
  255                                 }
  256                                 /*
  257                                  * XXX should perhaps do VOP_LOOKUP to
  258                                  * check that we got back to the right place,
  259                                  * but getting the locking games for that
  260                                  * right would be heinous.
  261                                  */
  262                                 if ((dp->d_type != DT_WHT) &&
  263                                     (dp->d_fileno == fileno)) {
  264                                         char *bp = *bpp;
  265                                         bp -= dp->d_namlen;
  266                                         
  267                                         if (bp <= bufp) {
  268                                                 error = ERANGE;
  269                                                 goto out;
  270                                         }
  271                                         bcopy(dp->d_name, bp, dp->d_namlen);
  272                                         error = 0;
  273                                         *bpp = bp;
  274                                         goto out;
  275                                 }
  276                                 cpos += reclen;
  277                         }
  278                 }
  279         } while (!eofflag);
  280         error = ENOENT;
  281                 
  282 out:
  283         vput(lvp);
  284         *lvpp = NULL;
  285         free(dirbuf, M_TEMP);
  286         return error;
  287 }
  288 
  289 
  290 /*
  291  * common routine shared by sys___getcwd() and linux_vn_isunder()
  292  */
  293 
  294 #define GETCWD_CHECK_ACCESS 0x0001
  295 
  296 static int
  297 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
  298         struct vnode *lvp;
  299         struct vnode *rvp;
  300         char **bpp;
  301         char *bufp;
  302         int limit;
  303         int flags;
  304         struct thread *td;
  305 {
  306         struct filedesc *fdp = td->td_proc->p_fd;
  307         struct vnode *uvp = NULL;
  308         char *bp = NULL;
  309         int error;
  310         int perms = VEXEC;
  311 
  312         if (rvp == NULL) {
  313                 rvp = fdp->fd_rdir;
  314                 if (rvp == NULL)
  315                         rvp = rootvnode;
  316         }
  317         
  318         VREF(rvp);
  319         VREF(lvp);
  320 
  321         /*
  322          * Error handling invariant:
  323          * Before a `goto out':
  324          *      lvp is either NULL, or locked and held.
  325          *      uvp is either NULL, or locked and held.
  326          */
  327 
  328         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  329         if (error != 0)
  330                 panic("vn_lock LK_RETRY returned error %d", error);
  331         if (bufp)
  332                 bp = *bpp;
  333         /*
  334          * this loop will terminate when one of the following happens:
  335          *      - we hit the root
  336          *      - getdirentries or lookup fails
  337          *      - we run out of space in the buffer.
  338          */
  339         if (lvp == rvp) {
  340                 if (bp)
  341                         *(--bp) = '/';
  342                 goto out;
  343         }
  344         do {
  345                 if (lvp->v_type != VDIR) {
  346                         error = ENOTDIR;
  347                         goto out;
  348                 }
  349                 
  350                 /*
  351                  * access check here is optional, depending on
  352                  * whether or not caller cares.
  353                  */
  354                 if (flags & GETCWD_CHECK_ACCESS) {
  355                         error = VOP_ACCESS(lvp, perms, td->td_ucred, td);
  356                         if (error)
  357                                 goto out;
  358                         perms = VEXEC|VREAD;
  359                 }
  360                 
  361                 /*
  362                  * step up if we're a covered vnode..
  363                  */
  364                 while (lvp->v_vflag & VV_ROOT) {
  365                         struct vnode *tvp;
  366 
  367                         if (lvp == rvp)
  368                                 goto out;
  369                         
  370                         tvp = lvp;
  371                         lvp = lvp->v_mount->mnt_vnodecovered;
  372                         vput(tvp);
  373                         /*
  374                          * hodie natus est radici frater
  375                          */
  376                         if (lvp == NULL) {
  377                                 error = ENOENT;
  378                                 goto out;
  379                         }
  380                         VREF(lvp);
  381                         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  382                         if (error != 0)
  383                                 panic("vn_lock LK_RETRY returned %d", error);
  384                 }
  385                 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
  386                 if (error)
  387                         goto out;
  388 #ifdef DIAGNOSTIC               
  389                 if (lvp != NULL)
  390                         panic("getcwd: oops, forgot to null lvp");
  391                 if (bufp && (bp <= bufp)) {
  392                         panic("getcwd: oops, went back too far");
  393                 }
  394 #endif          
  395                 if (bp) 
  396                         *(--bp) = '/';
  397                 lvp = uvp;
  398                 uvp = NULL;
  399                 limit--;
  400         } while ((lvp != rvp) && (limit > 0)); 
  401 
  402 out:
  403         if (bpp)
  404                 *bpp = bp;
  405         if (uvp)
  406                 vput(uvp);
  407         if (lvp)
  408                 vput(lvp);
  409         vrele(rvp);
  410         return error;
  411 }
  412 
  413 
  414 /*
  415  * Find pathname of process's current directory.
  416  *
  417  * Use vfs vnode-to-name reverse cache; if that fails, fall back
  418  * to reading directory contents.
  419  */
  420 
  421 int
  422 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
  423 {
  424         caddr_t bp, bend, path;
  425         int error, len, lenused;
  426 
  427 #ifdef DEBUG
  428         if (ldebug(getcwd))
  429                 printf(ARGS(getcwd, "%p, %ld"), args->buf, (long)args->bufsize);
  430 #endif
  431 
  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         error = kern___getcwd(td, path, UIO_SYSSPACE, len);
  442         if (!error) {
  443                 lenused = strlen(path) + 1;
  444                 if (lenused <= args->bufsize) {
  445                         td->td_retval[0] = lenused;
  446                         error = copyout(path, args->buf, lenused);
  447                 }
  448                 else
  449                         error = ERANGE;
  450         } else {
  451                 bp = &path[len];
  452                 bend = bp;
  453                 *(--bp) = '\0';
  454 
  455                 /*
  456                  * 5th argument here is "max number of vnodes to traverse".
  457                  * Since each entry takes up at least 2 bytes in the output buffer,
  458                  * limit it to N/2 vnodes for an N byte buffer.
  459                  */
  460 
  461                 mtx_lock(&Giant);
  462                 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
  463                     &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
  464                 mtx_unlock(&Giant);
  465 
  466                 if (error)
  467                         goto out;
  468                 lenused = bend - bp;
  469                 td->td_retval[0] = lenused;
  470                 /* put the result into user buffer */
  471                 error = copyout(bp, args->buf, lenused);
  472         }
  473 out:
  474         free(path, M_TEMP);
  475         return (error);
  476 }
  477 

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