4.3BSD-Reno/src/sys/kern/vfs_lookup.c
/*
* Copyright (c) 1982, 1986, 1989 Regents of the University of California.
* All rights reserved.
*
* Redistribution is only permitted until one year after the first shipment
* of 4.4BSD by the Regents. Otherwise, redistribution and use in source and
* binary forms are permitted provided that: (1) source distributions retain
* this entire copyright notice and comment, and (2) distributions including
* binaries display the following acknowledgement: This product includes
* software developed by the University of California, Berkeley and its
* contributors'' in the documentation or other materials provided with the
* distribution and in all advertising materials mentioning features or use
* of this software. Neither the name of the University nor the names of
* its contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* @(#)vfs_lookup.c 7.22 (Berkeley) 6/28/90
*/
#include "param.h"
#include "time.h"
#include "namei.h"
#include "vnode.h"
#include "mount.h"
#include "errno.h"
#include "malloc.h"
#ifdef KTRACE
#include "user.h"
#include "proc.h"
#include "ktrace.h"
#endif
/*
* Convert a pathname into a pointer to a locked inode.
* This is a very central and rather complicated routine.
*
* The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
* whether the name is to be looked up, created, renamed, or deleted.
* When CREATE, RENAME, or DELETE is specified, information usable in
* creating, renaming, or deleting a directory entry may be calculated.
* If flag has LOCKPARENT or'ed into it and the target of the pathname
* exists, namei returns both the target and its parent directory locked.
* When creating or renaming and LOCKPARENT is specified, the target may not
* be ".". When deleting and LOCKPARENT is specified, the target may be ".".
*
* The FOLLOW flag is set when symbolic links are to be followed
* when they occur at the end of the name translation process.
* Symbolic links are always followed for all other pathname
* components other than the last.
*
* The segflg defines whether the name is to be copied from user
* space or kernel space.
*
* Overall outline of namei:
*
* copy in name
* get starting directory
* dirloop:
* copy next component of name to ndp->ni_dent
* handle degenerate case where name is null string
* if .. and on mounted filesys, find parent
* call lookup routine for next component name
* directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
* component vnode returned in ni_vp (if it exists), locked.
* if symbolic link, massage name in buffer and continue at dirloop
* if result inode is mounted on, find mounted on vnode
* if more components of name, do next level at dirloop
* return the answer in ni_vp as locked vnode;
* if LOCKPARENT set, return locked parent in ni_dvp
*
* NOTE: (LOOKUP | LOCKPARENT) currently returns the parent vnode unlocked.
*/
namei(ndp)
register struct nameidata *ndp;
{
register char *cp; /* pointer into pathname argument */
register struct vnode *dp = 0; /* the directory we are searching */
register int i; /* Temp counter */
struct vnode *tdp; /* saved dp */
struct mount *mp; /* mount table entry */
int docache; /* == 0 do not cache last component */
int flag; /* LOOKUP, CREATE, RENAME or DELETE */
int wantparent; /* 1 => wantparent or lockparent flag */
int lockparent; /* 1 => lockparent flag */
int getbuf; /* 1 => Malloc a pathname buffer */
int rdonly; /* mounted read-only flag bit(s) */
int error = 0;
/*
* Setup: break out flag bits into variables.
*/
ndp->ni_dvp = NULL;
flag = ndp->ni_nameiop & OPFLAG;
wantparent = ndp->ni_nameiop & (LOCKPARENT|WANTPARENT);
lockparent = ndp->ni_nameiop & LOCKPARENT;
docache = (ndp->ni_nameiop & NOCACHE) ^ NOCACHE;
getbuf = (ndp->ni_nameiop & HASBUF) ^ HASBUF;
if (flag == DELETE || wantparent)
docache = 0;
rdonly = MNT_RDONLY;
if (ndp->ni_nameiop & REMOTE)
rdonly |= MNT_EXRDONLY;
/*
* Get a buffer for the name to be translated, and copy the
* name into the buffer.
*/
if (getbuf) {
MALLOC(ndp->ni_pnbuf, caddr_t, MAXPATHLEN, M_NAMEI, M_WAITOK);
if (ndp->ni_segflg == UIO_SYSSPACE)
error = copystr(ndp->ni_dirp, ndp->ni_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
else
error = copyinstr(ndp->ni_dirp, ndp->ni_pnbuf,
MAXPATHLEN, &ndp->ni_pathlen);
if (error) {
free(ndp->ni_pnbuf, M_NAMEI);
ndp->ni_vp = NULL;
return (error);
}
ndp->ni_ptr = ndp->ni_pnbuf;
}
ndp->ni_loopcnt = 0;
dp = ndp->ni_cdir;
VREF(dp);
#ifdef KTRACE
if (KTRPOINT(u.u_procp, KTR_NAMEI))
ktrnamei(u.u_procp->p_tracep, ndp->ni_pnbuf);
#endif
start:
/*
* Get starting directory.
* Done at start of translation and after symbolic link.
*/
if (*ndp->ni_ptr == '/') {
vrele(dp);
while (*ndp->ni_ptr == '/') {
ndp->ni_ptr++;
ndp->ni_pathlen--;
}
if ((dp = ndp->ni_rdir) == NULL)
dp = rootdir;
VREF(dp);
}
VOP_LOCK(dp);
ndp->ni_endoff = 0;
/*
* We come to dirloop to search a new directory.
*/
dirloop:
/*
* Copy next component of name to ndp->ni_dent.
* XXX kern_exec looks at d_name
* ??? The ni_hash value may be useful for vfs_cache
* XXX There must be the last component of the filename left
* somewhere accessible via. ndp for NFS (and any other stateless file
* systems) in case they are doing a CREATE. The "Towards a..." noted
* that ni_ptr would be left pointing to the last component, but since
* the ni_pnbuf gets free'd, that is not a good idea.
*/
if (getbuf) {
ndp->ni_hash = 0;
for (cp = ndp->ni_ptr, i = 0; *cp != 0 && *cp != '/'; cp++) {
if (i >= MAXNAMLEN) {
error = ENAMETOOLONG;
goto bad;
}
if (*cp & 0200)
if ((*cp&0377) == ('/'|0200) ||
flag != DELETE) {
error = EINVAL;
goto bad;
}
ndp->ni_dent.d_name[i++] = *cp;
ndp->ni_hash += (unsigned char)*cp * i;
}
ndp->ni_namelen = i;
ndp->ni_dent.d_namlen = i;
ndp->ni_dent.d_name[i] = '\0';
ndp->ni_pathlen -= i;
ndp->ni_next = cp;
#ifdef NAMEI_DIAGNOSTIC
printf("{%s}: ", ndp->ni_dent.d_name);
#endif
}
cp = ndp->ni_next;
ndp->ni_makeentry = 1;
if (*cp == '\0' && docache == 0)
ndp->ni_makeentry = 0;
ndp->ni_isdotdot = (ndp->ni_namelen == 2 &&
ndp->ni_dent.d_name[1] == '.' && ndp->ni_dent.d_name[0] == '.');
/*
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*/
if (ndp->ni_ptr[0] == '\0') {
if (flag != LOOKUP || wantparent) {
error = EISDIR;
goto bad;
}
if (getbuf)
free(ndp->ni_pnbuf, M_NAMEI);
if (!(ndp->ni_nameiop & LOCKLEAF))
VOP_UNLOCK(dp);
ndp->ni_vp = dp;
return (0);
}
/*
* Handle "..": two special cases.
* 1. If at root directory (e.g. after chroot)
* then ignore it so can't get out.
* 2. If this vnode is the root of a mounted
* file system, then replace it with the
* vnode which was mounted on so we take the
* .. in the other file system.
*/
if (ndp->ni_isdotdot) {
for (;;) {
if (dp == ndp->ni_rdir || dp == rootdir) {
ndp->ni_dvp = dp;
ndp->ni_vp = dp;
VREF(dp);
goto nextname;
}
if ((dp->v_flag & VROOT) == 0 ||
(ndp->ni_nameiop & NOCROSSMOUNT))
break;
tdp = dp;
dp = dp->v_mount->mnt_vnodecovered;
vput(tdp);
VREF(dp);
VOP_LOCK(dp);
}
}
/*
* We now have a segment name to search for, and a directory to search.
*/
if (error = VOP_LOOKUP(dp, ndp)) {
if (ndp->ni_vp != NULL)
panic("leaf should be empty");
#ifdef NAMEI_DIAGNOSTIC
printf("not found\n");
#endif
if (flag == LOOKUP || flag == DELETE ||
error != ENOENT || *cp != 0)
goto bad;
/*
* If creating and at end of pathname, then can consider
* allowing file to be created.
*/
if (ndp->ni_dvp->v_mount->mnt_flag & rdonly) {
error = EROFS;
goto bad;
}
/*
* We return with ni_vp NULL to indicate that the entry
* doesn't currently exist, leaving a pointer to the
* (possibly locked) directory inode in ndp->ni_dvp.
*/
if (getbuf)
FREE(ndp->ni_pnbuf, M_NAMEI);
return (0); /* should this be ENOENT? */
}
#ifdef NAMEI_DIAGNOSTIC
printf("found\n");
#endif
/*
* Check for symbolic link
*/
dp = ndp->ni_vp;
if ((dp->v_type == VLNK) &&
((ndp->ni_nameiop & FOLLOW) || *ndp->ni_next == '/')) {
struct iovec aiov;
struct uio auio;
int linklen;
if (!getbuf)
panic("namei: unexpected symlink");
if (++ndp->ni_loopcnt > MAXSYMLINKS) {
error = ELOOP;
goto bad2;
}
if (ndp->ni_pathlen > 1)
MALLOC(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK);
else
cp = ndp->ni_pnbuf;
aiov.iov_base = cp;
aiov.iov_len = MAXPATHLEN;
auio.uio_iov = &aiov;
auio.uio_iovcnt = 1;
auio.uio_offset = 0;
auio.uio_rw = UIO_READ;
auio.uio_segflg = UIO_SYSSPACE;
auio.uio_resid = MAXPATHLEN;
if (error = VOP_READLINK(dp, &auio, ndp->ni_cred)) {
if (ndp->ni_pathlen > 1)
free(cp, M_NAMEI);
goto bad2;
}
linklen = MAXPATHLEN - auio.uio_resid;
if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
if (ndp->ni_pathlen > 1)
free(cp, M_NAMEI);
error = ENAMETOOLONG;
goto bad2;
}
if (ndp->ni_pathlen > 1) {
bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
FREE(ndp->ni_pnbuf, M_NAMEI);
ndp->ni_pnbuf = cp;
} else
ndp->ni_pnbuf[linklen] = '\0';
ndp->ni_ptr = cp;
vput(dp);
dp = ndp->ni_dvp;
if (lockparent && ndp->ni_pathlen == 1)
VOP_UNLOCK(dp);
ndp->ni_pathlen += linklen;
goto start;
}
/*
* Check to see if the vnode has been mounted on;
* if so find the root of the mounted file system.
*/
mntloop:
while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
(ndp->ni_nameiop & NOCROSSMOUNT) == 0) {
while(mp->mnt_flag & MNT_MLOCK) {
mp->mnt_flag |= MNT_MWAIT;
sleep((caddr_t)mp, PVFS);
goto mntloop;
}
error = VFS_ROOT(dp->v_mountedhere, &tdp);
if (error)
goto bad2;
vput(dp);
ndp->ni_vp = dp = tdp;
}
nextname:
/*
* Not a symbolic link. If more pathname,
* continue at next component, else return.
*/
ndp->ni_ptr = ndp->ni_next;
if (*ndp->ni_ptr == '/') {
while (*ndp->ni_ptr == '/') {
ndp->ni_ptr++;
ndp->ni_pathlen--;
}
vrele(ndp->ni_dvp);
goto dirloop;
}
/*
* Check for read-only file systems.
*/
if (flag == DELETE || flag == RENAME) {
/*
* Disallow directory write attempts on read-only
* file systems.
*/
if ((dp->v_mount->mnt_flag & rdonly) ||
(wantparent && (ndp->ni_dvp->v_mount->mnt_flag & rdonly))) {
error = EROFS;
goto bad2;
}
}
if (!wantparent)
vrele(ndp->ni_dvp);
if ((ndp->ni_nameiop & LOCKLEAF) == 0)
VOP_UNLOCK(dp);
if (getbuf)
FREE(ndp->ni_pnbuf, M_NAMEI);
return (0);
bad2:
if (lockparent && *ndp->ni_next == '\0')
VOP_UNLOCK(ndp->ni_dvp);
vrele(ndp->ni_dvp);
bad:
vput(dp);
ndp->ni_vp = NULL;
if (getbuf)
FREE(ndp->ni_pnbuf, M_NAMEI);
return (error);
}