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: releng/5.1/sys/compat/linux/linux_getcwd.c 112430 2003-03-20 10:40:45Z phk $ */
    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 #include "opt_mac.h"
   42 
   43 #include <sys/param.h>
   44 #include <sys/systm.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/syscallsubr.h>
   51 #include <sys/vnode.h>
   52 #include <sys/mount.h>
   53 #include <sys/proc.h>
   54 #include <sys/uio.h>
   55 #include <sys/mac.h>
   56 #include <sys/malloc.h>
   57 #include <sys/dirent.h>
   58 #include <ufs/ufs/dir.h>        /* XXX only for DIRBLKSIZ */
   59 
   60 #include <machine/../linux/linux.h>
   61 #include <machine/../linux/linux_proto.h>
   62 #include <compat/linux/linux_util.h>
   63 
   64 static int
   65 linux_getcwd_scandir(struct vnode **, struct vnode **,
   66     char **, char *, struct thread *);
   67 static int
   68 linux_getcwd_common(struct vnode *, struct vnode *,
   69                    char **, char *, int, int, struct thread *);
   70 
   71 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
   72 
   73 /*
   74  * Vnode variable naming conventions in this file:
   75  *
   76  * rvp: the current root we're aiming towards.
   77  * lvp, *lvpp: the "lower" vnode
   78  * uvp, *uvpp: the "upper" vnode.
   79  *
   80  * Since all the vnodes we're dealing with are directories, and the
   81  * lookups are going *up* in the filesystem rather than *down*, the
   82  * usual "pvp" (parent) or "dvp" (directory) naming conventions are
   83  * too confusing.
   84  */
   85 
   86 /*
   87  * XXX Will infinite loop in certain cases if a directory read reliably
   88  *      returns EINVAL on last block.
   89  * XXX is EINVAL the right thing to return if a directory is malformed?
   90  */
   91 
   92 /*
   93  * XXX Untested vs. mount -o union; probably does the wrong thing.
   94  */
   95 
   96 /*
   97  * Find parent vnode of *lvpp, return in *uvpp
   98  *
   99  * If we care about the name, scan it looking for name of directory
  100  * entry pointing at lvp.
  101  *
  102  * Place the name in the buffer which starts at bufp, immediately
  103  * before *bpp, and move bpp backwards to point at the start of it.
  104  *
  105  * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
  106  * On exit, *uvpp is either NULL or is a locked vnode reference.
  107  */
  108 static int
  109 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
  110         struct vnode **lvpp;
  111         struct vnode **uvpp;
  112         char **bpp;
  113         char *bufp;
  114         struct thread *td;
  115 {
  116         int     error = 0;
  117         int     eofflag;
  118         off_t   off;
  119         int     tries;
  120         struct uio uio;
  121         struct iovec iov;
  122         char   *dirbuf = NULL;
  123         int     dirbuflen;
  124         ino_t   fileno;
  125         struct vattr va;
  126         struct vnode *uvp = NULL;
  127         struct vnode *lvp = *lvpp;      
  128         struct componentname cn;
  129         int len, reclen;
  130         tries = 0;
  131 
  132         /*
  133          * If we want the filename, get some info we need while the
  134          * current directory is still locked.
  135          */
  136         if (bufp != NULL) {
  137                 error = VOP_GETATTR(lvp, &va, td->td_ucred, td);
  138                 if (error) {
  139                         vput(lvp);
  140                         *lvpp = NULL;
  141                         *uvpp = NULL;
  142                         return error;
  143                 }
  144         }
  145 
  146         /*
  147          * Ok, we have to do it the hard way..
  148          * Next, get parent vnode using lookup of ..
  149          */
  150         cn.cn_nameiop = LOOKUP;
  151         cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
  152         cn.cn_thread = td;
  153         cn.cn_cred = td->td_ucred;
  154         cn.cn_pnbuf = NULL;
  155         cn.cn_nameptr = "..";
  156         cn.cn_namelen = 2;
  157         cn.cn_consume = 0;
  158         
  159         /*
  160          * At this point, lvp is locked and will be unlocked by the lookup.
  161          * On successful return, *uvpp will be locked
  162          */
  163         error = VOP_LOOKUP(lvp, uvpp, &cn);
  164         if (error) {
  165                 vput(lvp);
  166                 *lvpp = NULL;
  167                 *uvpp = NULL;
  168                 return error;
  169         }
  170         uvp = *uvpp;
  171 
  172         /* If we don't care about the pathname, we're done */
  173         if (bufp == NULL) {
  174                 vrele(lvp);
  175                 *lvpp = NULL;
  176                 return 0;
  177         }
  178         
  179         fileno = va.va_fileid;
  180 
  181         dirbuflen = DIRBLKSIZ;
  182         if (dirbuflen < va.va_blocksize)
  183                 dirbuflen = va.va_blocksize;
  184         dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  185 
  186 #if 0
  187 unionread:
  188 #endif
  189         off = 0;
  190         do {
  191                 /* call VOP_READDIR of parent */
  192                 iov.iov_base = dirbuf;
  193                 iov.iov_len = dirbuflen;
  194 
  195                 uio.uio_iov = &iov;
  196                 uio.uio_iovcnt = 1;
  197                 uio.uio_offset = off;
  198                 uio.uio_resid = dirbuflen;
  199                 uio.uio_segflg = UIO_SYSSPACE;
  200                 uio.uio_rw = UIO_READ;
  201                 uio.uio_td = td;
  202 
  203                 eofflag = 0;
  204 
  205 #ifdef MAC
  206                 error = mac_check_vnode_readdir(td->td_ucred, uvp);
  207                 if (error == 0)
  208 #endif /* MAC */
  209                         error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
  210                             0, 0);
  211 
  212                 off = uio.uio_offset;
  213 
  214                 /*
  215                  * Try again if NFS tosses its cookies.
  216                  * XXX this can still loop forever if the directory is busted
  217                  * such that the second or subsequent page of it always
  218                  * returns EINVAL
  219                  */
  220                 if ((error == EINVAL) && (tries < 3)) {
  221                         off = 0;
  222                         tries++;
  223                         continue;       /* once more, with feeling */
  224                 }
  225 
  226                 if (!error) {
  227                         char   *cpos;
  228                         struct dirent *dp;
  229                         
  230                         cpos = dirbuf;
  231                         tries = 0;
  232                                 
  233                         /* scan directory page looking for matching vnode */ 
  234                         for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
  235                                 dp = (struct dirent *) cpos;
  236                                 reclen = dp->d_reclen;
  237 
  238                                 /* check for malformed directory.. */
  239                                 if (reclen < DIRENT_MINSIZE) {
  240                                         error = EINVAL;
  241                                         goto out;
  242                                 }
  243                                 /*
  244                                  * XXX should perhaps do VOP_LOOKUP to
  245                                  * check that we got back to the right place,
  246                                  * but getting the locking games for that
  247                                  * right would be heinous.
  248                                  */
  249                                 if ((dp->d_type != DT_WHT) &&
  250                                     (dp->d_fileno == fileno)) {
  251                                         char *bp = *bpp;
  252                                         bp -= dp->d_namlen;
  253                                         
  254                                         if (bp <= bufp) {
  255                                                 error = ERANGE;
  256                                                 goto out;
  257                                         }
  258                                         bcopy(dp->d_name, bp, dp->d_namlen);
  259                                         error = 0;
  260                                         *bpp = bp;
  261                                         goto out;
  262                                 }
  263                                 cpos += reclen;
  264                         }
  265                 }
  266         } while (!eofflag);
  267         error = ENOENT;
  268                 
  269 out:
  270         vrele(lvp);
  271         *lvpp = NULL;
  272         free(dirbuf, M_TEMP);
  273         return error;
  274 }
  275 
  276 
  277 /*
  278  * common routine shared by sys___getcwd() and linux_vn_isunder()
  279  */
  280 
  281 #define GETCWD_CHECK_ACCESS 0x0001
  282 
  283 static int
  284 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
  285         struct vnode *lvp;
  286         struct vnode *rvp;
  287         char **bpp;
  288         char *bufp;
  289         int limit;
  290         int flags;
  291         struct thread *td;
  292 {
  293         struct filedesc *fdp = td->td_proc->p_fd;
  294         struct vnode *uvp = NULL;
  295         char *bp = NULL;
  296         int error;
  297         int perms = VEXEC;
  298 
  299         if (rvp == NULL) {
  300                 rvp = fdp->fd_rdir;
  301                 if (rvp == NULL)
  302                         rvp = rootvnode;
  303         }
  304         
  305         VREF(rvp);
  306         VREF(lvp);
  307 
  308         /*
  309          * Error handling invariant:
  310          * Before a `goto out':
  311          *      lvp is either NULL, or locked and held.
  312          *      uvp is either NULL, or locked and held.
  313          */
  314 
  315         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  316         if (error) {
  317                 vrele(lvp);
  318                 lvp = NULL;
  319                 goto out;
  320         }
  321         if (bufp)
  322                 bp = *bpp;
  323         /*
  324          * this loop will terminate when one of the following happens:
  325          *      - we hit the root
  326          *      - getdirentries or lookup fails
  327          *      - we run out of space in the buffer.
  328          */
  329         if (lvp == rvp) {
  330                 if (bp)
  331                         *(--bp) = '/';
  332                 goto out;
  333         }
  334         do {
  335                 if (lvp->v_type != VDIR) {
  336                         error = ENOTDIR;
  337                         goto out;
  338                 }
  339                 
  340                 /*
  341                  * access check here is optional, depending on
  342                  * whether or not caller cares.
  343                  */
  344                 if (flags & GETCWD_CHECK_ACCESS) {
  345                         error = VOP_ACCESS(lvp, perms, td->td_ucred, td);
  346                         if (error)
  347                                 goto out;
  348                         perms = VEXEC|VREAD;
  349                 }
  350                 
  351                 /*
  352                  * step up if we're a covered vnode..
  353                  */
  354                 while (lvp->v_vflag & VV_ROOT) {
  355                         struct vnode *tvp;
  356 
  357                         if (lvp == rvp)
  358                                 goto out;
  359                         
  360                         tvp = lvp;
  361                         lvp = lvp->v_mount->mnt_vnodecovered;
  362                         vput(tvp);
  363                         /*
  364                          * hodie natus est radici frater
  365                          */
  366                         if (lvp == NULL) {
  367                                 error = ENOENT;
  368                                 goto out;
  369                         }
  370                         VREF(lvp);
  371                         error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
  372                         if (error != 0) {
  373                                 vrele(lvp);
  374                                 lvp = NULL;
  375                                 goto out;
  376                         }
  377                 }
  378                 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
  379                 if (error)
  380                         goto out;
  381 #if DIAGNOSTIC          
  382                 if (lvp != NULL)
  383                         panic("getcwd: oops, forgot to null lvp");
  384                 if (bufp && (bp <= bufp)) {
  385                         panic("getcwd: oops, went back too far");
  386                 }
  387 #endif          
  388                 if (bp) 
  389                         *(--bp) = '/';
  390                 lvp = uvp;
  391                 uvp = NULL;
  392                 limit--;
  393         } while ((lvp != rvp) && (limit > 0)); 
  394 
  395 out:
  396         if (bpp)
  397                 *bpp = bp;
  398         if (uvp)
  399                 vput(uvp);
  400         if (lvp)
  401                 vput(lvp);
  402         vrele(rvp);
  403         return error;
  404 }
  405 
  406 
  407 /*
  408  * Find pathname of process's current directory.
  409  *
  410  * Use vfs vnode-to-name reverse cache; if that fails, fall back
  411  * to reading directory contents.
  412  */
  413 
  414 int
  415 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
  416 {
  417         caddr_t bp, bend, path;
  418         int error, len, lenused;
  419 
  420 #ifdef DEBUG
  421         printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)td->td_proc->p_pid,
  422                args->buf, (long)args->bufsize);
  423 #endif
  424 
  425         len = args->bufsize;
  426 
  427         if (len > MAXPATHLEN*4)
  428                 len = MAXPATHLEN*4;
  429         else if (len < 2)
  430                 return ERANGE;
  431 
  432         path = (char *)malloc(len, M_TEMP, M_WAITOK);
  433 
  434         error = kern___getcwd(td, path, UIO_SYSSPACE, len);
  435         if (!error) {
  436                 lenused = strlen(path) + 1;
  437                 if (lenused <= args->bufsize) {
  438                         td->td_retval[0] = lenused;
  439                         error = copyout(path, args->buf, lenused);
  440                 }
  441                 else
  442                         error = ERANGE;
  443         } else {
  444                 bp = &path[len];
  445                 bend = bp;
  446                 *(--bp) = '\0';
  447 
  448                 /*
  449                  * 5th argument here is "max number of vnodes to traverse".
  450                  * Since each entry takes up at least 2 bytes in the output buffer,
  451                  * limit it to N/2 vnodes for an N byte buffer.
  452                  */
  453 
  454                 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
  455                     &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
  456 
  457                 if (error)
  458                         goto out;
  459                 lenused = bend - bp;
  460                 td->td_retval[0] = lenused;
  461                 /* put the result into user buffer */
  462                 error = copyout(bp, args->buf, lenused);
  463         }
  464 out:
  465         free(path, M_TEMP);
  466         return (error);
  467 }
  468 

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