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1.1 root 1: /*
2: * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
3: * All rights reserved.
4: *
5: * Redistribution is only permitted until one year after the first shipment
6: * of 4.4BSD by the Regents. Otherwise, redistribution and use in source and
7: * binary forms are permitted provided that: (1) source distributions retain
8: * this entire copyright notice and comment, and (2) distributions including
9: * binaries display the following acknowledgement: This product includes
10: * software developed by the University of California, Berkeley and its
11: * contributors'' in the documentation or other materials provided with the
12: * distribution and in all advertising materials mentioning features or use
13: * of this software. Neither the name of the University nor the names of
14: * its contributors may be used to endorse or promote products derived from
15: * this software without specific prior written permission.
16: * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
17: * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
18: * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19: *
20: * @(#)vfs_lookup.c 7.22 (Berkeley) 6/28/90
21: */
22:
23: #include "param.h"
24: #include "time.h"
25: #include "namei.h"
26: #include "vnode.h"
27: #include "mount.h"
28: #include "errno.h"
29: #include "malloc.h"
30:
31: #ifdef KTRACE
32: #include "user.h"
33: #include "proc.h"
34: #include "ktrace.h"
35: #endif
36:
37: /*
38: * Convert a pathname into a pointer to a locked inode.
39: * This is a very central and rather complicated routine.
40: *
41: * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
42: * whether the name is to be looked up, created, renamed, or deleted.
43: * When CREATE, RENAME, or DELETE is specified, information usable in
44: * creating, renaming, or deleting a directory entry may be calculated.
45: * If flag has LOCKPARENT or'ed into it and the target of the pathname
46: * exists, namei returns both the target and its parent directory locked.
47: * When creating or renaming and LOCKPARENT is specified, the target may not
48: * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
49: *
50: * The FOLLOW flag is set when symbolic links are to be followed
51: * when they occur at the end of the name translation process.
52: * Symbolic links are always followed for all other pathname
53: * components other than the last.
54: *
55: * The segflg defines whether the name is to be copied from user
56: * space or kernel space.
57: *
58: * Overall outline of namei:
59: *
60: * copy in name
61: * get starting directory
62: * dirloop:
63: * copy next component of name to ndp->ni_dent
64: * handle degenerate case where name is null string
65: * if .. and on mounted filesys, find parent
66: * call lookup routine for next component name
67: * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
68: * component vnode returned in ni_vp (if it exists), locked.
69: * if symbolic link, massage name in buffer and continue at dirloop
70: * if result inode is mounted on, find mounted on vnode
71: * if more components of name, do next level at dirloop
72: * return the answer in ni_vp as locked vnode;
73: * if LOCKPARENT set, return locked parent in ni_dvp
74: *
75: * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent vnode unlocked.
76: */
77: namei(ndp)
78: register struct nameidata *ndp;
79: {
80: register char *cp; /* pointer into pathname argument */
81: register struct vnode *dp = 0; /* the directory we are searching */
82: register int i; /* Temp counter */
83: struct vnode *tdp; /* saved dp */
84: struct mount *mp; /* mount table entry */
85: int docache; /* == 0 do not cache last component */
86: int flag; /* LOOKUP, CREATE, RENAME or DELETE */
87: int wantparent; /* 1 => wantparent or lockparent flag */
88: int lockparent; /* 1 => lockparent flag */
89: int getbuf; /* 1 => Malloc a pathname buffer */
90: int rdonly; /* mounted read-only flag bit(s) */
91: int error = 0;
92:
93: /*
94: * Setup: break out flag bits into variables.
95: */
96: ndp->ni_dvp = NULL;
97: flag = ndp->ni_nameiop & OPFLAG;
98: wantparent = ndp->ni_nameiop & (LOCKPARENT|WANTPARENT);
99: lockparent = ndp->ni_nameiop & LOCKPARENT;
100: docache = (ndp->ni_nameiop & NOCACHE) ^ NOCACHE;
101: getbuf = (ndp->ni_nameiop & HASBUF) ^ HASBUF;
102: if (flag == DELETE || wantparent)
103: docache = 0;
104: rdonly = MNT_RDONLY;
105: if (ndp->ni_nameiop & REMOTE)
106: rdonly |= MNT_EXRDONLY;
107: /*
108: * Get a buffer for the name to be translated, and copy the
109: * name into the buffer.
110: */
111: if (getbuf) {
112: MALLOC(ndp->ni_pnbuf, caddr_t, MAXPATHLEN, M_NAMEI, M_WAITOK);
113: if (ndp->ni_segflg == UIO_SYSSPACE)
114: error = copystr(ndp->ni_dirp, ndp->ni_pnbuf,
115: MAXPATHLEN, &ndp->ni_pathlen);
116: else
117: error = copyinstr(ndp->ni_dirp, ndp->ni_pnbuf,
118: MAXPATHLEN, &ndp->ni_pathlen);
119: if (error) {
120: free(ndp->ni_pnbuf, M_NAMEI);
121: ndp->ni_vp = NULL;
122: return (error);
123: }
124: ndp->ni_ptr = ndp->ni_pnbuf;
125: }
126: ndp->ni_loopcnt = 0;
127: dp = ndp->ni_cdir;
128: VREF(dp);
129: #ifdef KTRACE
130: if (KTRPOINT(u.u_procp, KTR_NAMEI))
131: ktrnamei(u.u_procp->p_tracep, ndp->ni_pnbuf);
132: #endif
133:
134: start:
135: /*
136: * Get starting directory.
137: * Done at start of translation and after symbolic link.
138: */
139: if (*ndp->ni_ptr == '/') {
140: vrele(dp);
141: while (*ndp->ni_ptr == '/') {
142: ndp->ni_ptr++;
143: ndp->ni_pathlen--;
144: }
145: if ((dp = ndp->ni_rdir) == NULL)
146: dp = rootdir;
147: VREF(dp);
148: }
149: VOP_LOCK(dp);
150: ndp->ni_endoff = 0;
151:
152: /*
153: * We come to dirloop to search a new directory.
154: */
155: dirloop:
156: /*
157: * Copy next component of name to ndp->ni_dent.
158: * XXX kern_exec looks at d_name
159: * ??? The ni_hash value may be useful for vfs_cache
160: * XXX There must be the last component of the filename left
161: * somewhere accessible via. ndp for NFS (and any other stateless file
162: * systems) in case they are doing a CREATE. The "Towards a..." noted
163: * that ni_ptr would be left pointing to the last component, but since
164: * the ni_pnbuf gets free'd, that is not a good idea.
165: */
166: if (getbuf) {
167: ndp->ni_hash = 0;
168: for (cp = ndp->ni_ptr, i = 0; *cp != 0 && *cp != '/'; cp++) {
169: if (i >= MAXNAMLEN) {
170: error = ENAMETOOLONG;
171: goto bad;
172: }
173: if (*cp & 0200)
174: if ((*cp&0377) == ('/'|0200) ||
175: flag != DELETE) {
176: error = EINVAL;
177: goto bad;
178: }
179: ndp->ni_dent.d_name[i++] = *cp;
180: ndp->ni_hash += (unsigned char)*cp * i;
181: }
182: ndp->ni_namelen = i;
183: ndp->ni_dent.d_namlen = i;
184: ndp->ni_dent.d_name[i] = '\0';
185: ndp->ni_pathlen -= i;
186: ndp->ni_next = cp;
187: #ifdef NAMEI_DIAGNOSTIC
188: printf("{%s}: ", ndp->ni_dent.d_name);
189: #endif
190: }
191: cp = ndp->ni_next;
192: ndp->ni_makeentry = 1;
193: if (*cp == '\0' && docache == 0)
194: ndp->ni_makeentry = 0;
195: ndp->ni_isdotdot = (ndp->ni_namelen == 2 &&
196: ndp->ni_dent.d_name[1] == '.' && ndp->ni_dent.d_name[0] == '.');
197:
198: /*
199: * Check for degenerate name (e.g. / or "")
200: * which is a way of talking about a directory,
201: * e.g. like "/." or ".".
202: */
203: if (ndp->ni_ptr[0] == '\0') {
204: if (flag != LOOKUP || wantparent) {
205: error = EISDIR;
206: goto bad;
207: }
208: if (getbuf)
209: free(ndp->ni_pnbuf, M_NAMEI);
210: if (!(ndp->ni_nameiop & LOCKLEAF))
211: VOP_UNLOCK(dp);
212: ndp->ni_vp = dp;
213: return (0);
214: }
215:
216: /*
217: * Handle "..": two special cases.
218: * 1. If at root directory (e.g. after chroot)
219: * then ignore it so can't get out.
220: * 2. If this vnode is the root of a mounted
221: * file system, then replace it with the
222: * vnode which was mounted on so we take the
223: * .. in the other file system.
224: */
225: if (ndp->ni_isdotdot) {
226: for (;;) {
227: if (dp == ndp->ni_rdir || dp == rootdir) {
228: ndp->ni_dvp = dp;
229: ndp->ni_vp = dp;
230: VREF(dp);
231: goto nextname;
232: }
233: if ((dp->v_flag & VROOT) == 0 ||
234: (ndp->ni_nameiop & NOCROSSMOUNT))
235: break;
236: tdp = dp;
237: dp = dp->v_mount->mnt_vnodecovered;
238: vput(tdp);
239: VREF(dp);
240: VOP_LOCK(dp);
241: }
242: }
243:
244: /*
245: * We now have a segment name to search for, and a directory to search.
246: */
247: if (error = VOP_LOOKUP(dp, ndp)) {
248: if (ndp->ni_vp != NULL)
249: panic("leaf should be empty");
250: #ifdef NAMEI_DIAGNOSTIC
251: printf("not found\n");
252: #endif
253: if (flag == LOOKUP || flag == DELETE ||
254: error != ENOENT || *cp != 0)
255: goto bad;
256: /*
257: * If creating and at end of pathname, then can consider
258: * allowing file to be created.
259: */
260: if (ndp->ni_dvp->v_mount->mnt_flag & rdonly) {
261: error = EROFS;
262: goto bad;
263: }
264: /*
265: * We return with ni_vp NULL to indicate that the entry
266: * doesn't currently exist, leaving a pointer to the
267: * (possibly locked) directory inode in ndp->ni_dvp.
268: */
269: if (getbuf)
270: FREE(ndp->ni_pnbuf, M_NAMEI);
271: return (0); /* should this be ENOENT? */
272: }
273: #ifdef NAMEI_DIAGNOSTIC
274: printf("found\n");
275: #endif
276:
277: /*
278: * Check for symbolic link
279: */
280: dp = ndp->ni_vp;
281: if ((dp->v_type == VLNK) &&
282: ((ndp->ni_nameiop & FOLLOW) || *ndp->ni_next == '/')) {
283: struct iovec aiov;
284: struct uio auio;
285: int linklen;
286:
287: if (!getbuf)
288: panic("namei: unexpected symlink");
289: if (++ndp->ni_loopcnt > MAXSYMLINKS) {
290: error = ELOOP;
291: goto bad2;
292: }
293: if (ndp->ni_pathlen > 1)
294: MALLOC(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK);
295: else
296: cp = ndp->ni_pnbuf;
297: aiov.iov_base = cp;
298: aiov.iov_len = MAXPATHLEN;
299: auio.uio_iov = &aiov;
300: auio.uio_iovcnt = 1;
301: auio.uio_offset = 0;
302: auio.uio_rw = UIO_READ;
303: auio.uio_segflg = UIO_SYSSPACE;
304: auio.uio_resid = MAXPATHLEN;
305: if (error = VOP_READLINK(dp, &auio, ndp->ni_cred)) {
306: if (ndp->ni_pathlen > 1)
307: free(cp, M_NAMEI);
308: goto bad2;
309: }
310: linklen = MAXPATHLEN - auio.uio_resid;
311: if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
312: if (ndp->ni_pathlen > 1)
313: free(cp, M_NAMEI);
314: error = ENAMETOOLONG;
315: goto bad2;
316: }
317: if (ndp->ni_pathlen > 1) {
318: bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
319: FREE(ndp->ni_pnbuf, M_NAMEI);
320: ndp->ni_pnbuf = cp;
321: } else
322: ndp->ni_pnbuf[linklen] = '\0';
323: ndp->ni_ptr = cp;
324: vput(dp);
325: dp = ndp->ni_dvp;
326: if (lockparent && ndp->ni_pathlen == 1)
327: VOP_UNLOCK(dp);
328: ndp->ni_pathlen += linklen;
329: goto start;
330: }
331:
332: /*
333: * Check to see if the vnode has been mounted on;
334: * if so find the root of the mounted file system.
335: */
336: mntloop:
337: while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
338: (ndp->ni_nameiop & NOCROSSMOUNT) == 0) {
339: while(mp->mnt_flag & MNT_MLOCK) {
340: mp->mnt_flag |= MNT_MWAIT;
341: sleep((caddr_t)mp, PVFS);
342: goto mntloop;
343: }
344: error = VFS_ROOT(dp->v_mountedhere, &tdp);
345: if (error)
346: goto bad2;
347: vput(dp);
348: ndp->ni_vp = dp = tdp;
349: }
350:
351: nextname:
352: /*
353: * Not a symbolic link. If more pathname,
354: * continue at next component, else return.
355: */
356: ndp->ni_ptr = ndp->ni_next;
357: if (*ndp->ni_ptr == '/') {
358: while (*ndp->ni_ptr == '/') {
359: ndp->ni_ptr++;
360: ndp->ni_pathlen--;
361: }
362: vrele(ndp->ni_dvp);
363: goto dirloop;
364: }
365: /*
366: * Check for read-only file systems.
367: */
368: if (flag == DELETE || flag == RENAME) {
369: /*
370: * Disallow directory write attempts on read-only
371: * file systems.
372: */
373: if ((dp->v_mount->mnt_flag & rdonly) ||
374: (wantparent && (ndp->ni_dvp->v_mount->mnt_flag & rdonly))) {
375: error = EROFS;
376: goto bad2;
377: }
378: }
379: if (!wantparent)
380: vrele(ndp->ni_dvp);
381: if ((ndp->ni_nameiop & LOCKLEAF) == 0)
382: VOP_UNLOCK(dp);
383: if (getbuf)
384: FREE(ndp->ni_pnbuf, M_NAMEI);
385: return (0);
386:
387: bad2:
388: if (lockparent && *ndp->ni_next == '\0')
389: VOP_UNLOCK(ndp->ni_dvp);
390: vrele(ndp->ni_dvp);
391: bad:
392: vput(dp);
393: ndp->ni_vp = NULL;
394: if (getbuf)
395: FREE(ndp->ni_pnbuf, M_NAMEI);
396: return (error);
397: }
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