Bug Summary

File:msdosfs/msdosfs_fat.c
Warning:line 236, column 9
Access to field 'b_data' results in a dereference of a null pointer (loaded from variable 'bp')

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name msdosfs_fat.c -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model static -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -ffreestanding -mcmodel=kernel -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -target-feature -sse2 -target-feature -sse -target-feature -3dnow -target-feature -mmx -target-feature +save-args -disable-red-zone -no-implicit-float -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/sys/arch/amd64/compile/GENERIC.MP/obj -nostdsysteminc -nobuiltininc -resource-dir /usr/local/lib/clang/13.0.0 -I /usr/src/sys -I /usr/src/sys/arch/amd64/compile/GENERIC.MP/obj -I /usr/src/sys/arch -I /usr/src/sys/dev/pci/drm/include -I /usr/src/sys/dev/pci/drm/include/uapi -I /usr/src/sys/dev/pci/drm/amd/include/asic_reg -I /usr/src/sys/dev/pci/drm/amd/include -I /usr/src/sys/dev/pci/drm/amd/amdgpu -I /usr/src/sys/dev/pci/drm/amd/display -I /usr/src/sys/dev/pci/drm/amd/display/include -I /usr/src/sys/dev/pci/drm/amd/display/dc -I /usr/src/sys/dev/pci/drm/amd/display/amdgpu_dm -I /usr/src/sys/dev/pci/drm/amd/pm/inc -I /usr/src/sys/dev/pci/drm/amd/pm/swsmu -I /usr/src/sys/dev/pci/drm/amd/pm/swsmu/smu11 -I /usr/src/sys/dev/pci/drm/amd/pm/swsmu/smu12 -I /usr/src/sys/dev/pci/drm/amd/pm/powerplay -I /usr/src/sys/dev/pci/drm/amd/pm/powerplay/hwmgr -I /usr/src/sys/dev/pci/drm/amd/pm/powerplay/smumgr -I /usr/src/sys/dev/pci/drm/amd/display/dc/inc -I /usr/src/sys/dev/pci/drm/amd/display/dc/inc/hw -I /usr/src/sys/dev/pci/drm/amd/display/dc/clk_mgr -I /usr/src/sys/dev/pci/drm/amd/display/modules/inc -I /usr/src/sys/dev/pci/drm/amd/display/modules/hdcp -I /usr/src/sys/dev/pci/drm/amd/display/dmub/inc -I /usr/src/sys/dev/pci/drm/i915 -D DDB -D DIAGNOSTIC -D KTRACE -D ACCOUNTING -D KMEMSTATS -D PTRACE -D POOL_DEBUG -D CRYPTO -D SYSVMSG -D SYSVSEM -D SYSVSHM -D UVM_SWAP_ENCRYPT -D FFS -D FFS2 -D FFS_SOFTUPDATES -D UFS_DIRHASH -D QUOTA -D EXT2FS -D MFS -D NFSCLIENT -D NFSSERVER -D CD9660 -D UDF -D MSDOSFS -D FIFO -D FUSE -D SOCKET_SPLICE -D TCP_ECN -D TCP_SIGNATURE -D INET6 -D IPSEC -D PPP_BSDCOMP -D PPP_DEFLATE -D PIPEX -D MROUTING -D MPLS -D BOOT_CONFIG -D USER_PCICONF -D APERTURE -D MTRR -D NTFS -D HIBERNATE -D PCIVERBOSE -D USBVERBOSE -D WSDISPLAY_COMPAT_USL -D WSDISPLAY_COMPAT_RAWKBD -D WSDISPLAY_DEFAULTSCREENS=6 -D X86EMU -D ONEWIREVERBOSE -D MULTIPROCESSOR -D MAXUSERS=80 -D _KERNEL -D CONFIG_DRM_AMD_DC_DCN3_0 -O2 -Wno-pointer-sign -Wno-address-of-packed-member -Wno-constant-conversion -Wno-unused-but-set-variable -Wno-gnu-folding-constant -fdebug-compilation-dir=/usr/src/sys/arch/amd64/compile/GENERIC.MP/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -o /usr/obj/sys/arch/amd64/compile/GENERIC.MP/scan-build/2022-01-12-131800-47421-1 -x c /usr/src/sys/msdosfs/msdosfs_fat.c
1/* $OpenBSD: msdosfs_fat.c,v 1.34 2021/03/11 13:31:35 jsg Exp $ */
2/* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 ws Exp $ */
3
4/*-
5 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
6 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
7 * All rights reserved.
8 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
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 TooLs GmbH.
21 * 4. The name of TooLs GmbH may not be used to endorse or promote products
22 * derived from this software without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
29 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
30 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
31 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
32 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
33 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35/*
36 * Written by Paul Popelka (paulp@uts.amdahl.com)
37 *
38 * You can do anything you want with this software, just don't say you wrote
39 * it, and don't remove this notice.
40 *
41 * This software is provided "as is".
42 *
43 * The author supplies this software to be publicly redistributed on the
44 * understanding that the author is not responsible for the correct
45 * functioning of this software in any circumstances and is not liable for
46 * any damages caused by this software.
47 *
48 * October 1992
49 */
50
51/*
52 * kernel include files.
53 */
54#include <sys/param.h>
55#include <sys/systm.h>
56#include <sys/buf.h>
57#include <sys/namei.h>
58#include <sys/mount.h> /* to define statfs structure */
59#include <sys/vnode.h> /* to define vattr structure */
60#include <sys/lock.h>
61#include <sys/errno.h>
62#include <sys/dirent.h>
63
64/*
65 * msdosfs include files.
66 */
67#include <msdosfs/bpb.h>
68#include <msdosfs/msdosfsmount.h>
69#include <msdosfs/direntry.h>
70#include <msdosfs/denode.h>
71#include <msdosfs/fat.h>
72
73/*
74 * Fat cache stats.
75 */
76int fc_fileextends; /* # of file extends */
77int fc_lfcempty; /* # of time last file cluster cache entry
78 * was empty */
79int fc_bmapcalls; /* # of times pcbmap was called */
80
81#define LMMAX20 20
82int fc_lmdistance[LMMAX20]; /* counters for how far off the last
83 * cluster mapped entry was. */
84int fc_largedistance; /* off by more than LMMAX */
85
86static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *,
87 uint32_t *);
88void updatefats(struct msdosfsmount *, struct buf *, uint32_t);
89static __inline void usemap_free(struct msdosfsmount *, uint32_t);
90static __inline void usemap_alloc(struct msdosfsmount *, uint32_t);
91static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t);
92int chainlength(struct msdosfsmount *, uint32_t, uint32_t);
93int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *,
94 uint32_t *);
95
96static void
97fatblock(struct msdosfsmount *pmp, uint32_t ofs, uint32_t *bnp, uint32_t *sizep,
98 uint32_t *bop)
99{
100 uint32_t bn, size;
101
102 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
103 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE(1 << 9);
104 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
105
106 if (bnp)
107 *bnp = bn;
108 if (sizep)
109 *sizep = size;
110 if (bop)
111 *bop = ofs % pmp->pm_fatblocksize;
112}
113
114/*
115 * Map the logical cluster number of a file into a physical disk sector
116 * that is filesystem relative.
117 *
118 * dep - address of denode representing the file of interest
119 * findcn - file relative cluster whose filesystem relative cluster number
120 * and/or block number are/is to be found
121 * bnp - address of where to place the file system relative block number.
122 * If this pointer is null then don't return this quantity.
123 * cnp - address of where to place the file system relative cluster number.
124 * If this pointer is null then don't return this quantity.
125 * sp - address of where to place the block size for the file/dir
126 * If this pointer is null then don't return this quantity.
127 *
128 * NOTE: Either bnp or cnp must be non-null.
129 * This function has one side effect. If the requested file relative cluster
130 * is beyond the end of file, then the actual number of clusters in the file
131 * is returned in *cnp. This is useful for determining how long a directory is.
132 * If cnp is null, nothing is returned.
133 */
134int
135pcbmap(struct denode *dep, uint32_t findcn, daddr_t *bnp, uint32_t *cnp,
136 int *sp)
137{
138 int error;
139 uint32_t i;
140 uint32_t cn;
141 uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */
142 uint32_t byteoffset;
143 uint32_t bn;
144 uint32_t bo;
145 struct buf *bp = NULL((void *)0);
5
←
'bp' initialized to a null pointer value
→
146 uint32_t bp_bn = -1;
147 struct msdosfsmount *pmp = dep->de_pmp;
148 uint32_t bsize;
149
150 fc_bmapcalls++;
151
152 /*
153 * If they don't give us someplace to return a value then don't
154 * bother doing anything.
155 */
156 if (bnp
5.1
'bnp' is equal to NULL
 == NULL((void *)0) && cnp
5.2
'cnp' is not equal to NULL
 == NULL((void *)0) && sp == NULL((void *)0))
157 return (0);
158
159 cn = dep->de_StartCluster;
160 /*
161 * The "file" that makes up the root directory is contiguous,
162 * permanently allocated, of fixed size, and is not made up of
163 * clusters. If the cluster number is beyond the end of the root
164 * directory, then return the number of clusters in the file.
165 */
166 if (cn
5.3
'cn' is not equal to MSDOSFSROOT
 == MSDOSFSROOT0) {
6
←
Taking false branch
→
167 if (dep->de_Attributes & ATTR_DIRECTORY0x10) {
168 if (de_cn2off(pmp, findcn)((findcn) << (pmp)->pm_cnshift) >= dep->de_FileSize) {
169 if (cnp)
170 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize)((pmp->pm_rootdirsize) >> ((pmp)->pm_cnshift - (pmp
)->pm_bnshift));
171 return (E2BIG7);
172 }
173 if (bnp)
174 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn)((findcn) << ((pmp)->pm_cnshift - (pmp)->pm_bnshift
));
175 if (cnp)
176 *cnp = MSDOSFSROOT0;
177 if (sp)
178 *sp = min(pmp->pm_bpcluster,
179 dep->de_FileSize - de_cn2off(pmp, findcn)((findcn) << (pmp)->pm_cnshift));
180 return (0);
181 } else { /* just an empty file */
182 if (cnp)
183 *cnp = 0;
184 return (E2BIG7);
185 }
186 }
187
188 /*
189 * All other files do I/O in cluster sized blocks
190 */
191 if (sp
6.1
'sp' is null
)
7
←
Taking false branch
→
192 *sp = pmp->pm_bpcluster;
193
194 /*
195 * Rummage around in the fat cache, maybe we can avoid tromping
196 * thru every fat entry for the file. And, keep track of how far
197 * off the cache was from where we wanted to be.
198 */
199 i = 0;
200 fc_lookup(dep, findcn, &i, &cn);
201 if ((bn = findcn - i) >= LMMAX20)
8
←
Taking true branch
→
202 fc_largedistance++;
203 else
204 fc_lmdistance[bn]++;
205
206 /*
207 * Handle all other files or directories the normal way.
208 */
209 for (; i < findcn; i++) {
9
←
Loop condition is true. Entering loop body
→
210 /*
211 * Stop with all reserved clusters, not just with EOF.
212 */
213 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD0xfffffff6)
10
←
Assuming the condition is false
→
11
←
Taking false branch
→
214 goto hiteof;
215 byteoffset = FATOFS(pmp, cn)((cn) * (pmp)->pm_fatmult / (pmp)->pm_fatdiv);
216 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
217 if (bn != bp_bn) {
12
←
Assuming 'bn' is equal to 'bp_bn'
→
13
←
Taking false branch
→
218 if (bp)
219 brelse(bp);
220 error = bread(pmp->pm_devvp, bn, bsize, &bp);
221 if (error) {
222 brelse(bp);
223 return (error);
224 }
225 bp_bn = bn;
226 }
227 prevcn = cn;
228 if (bo >= bsize) {
14
←
Assuming 'bo' is < 'bsize'
→
15
←
Taking false branch
→
229 if (bp)
230 brelse(bp);
231 return (EIO5);
232 }
233 if (FAT32(pmp)(pmp->pm_fatmask == 0x0fffffff))
16
←
Assuming field 'pm_fatmask' is not equal to 268435455
→
17
←
Taking false branch
→
234 cn = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
235 else
236 cn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
18
←
Access to field 'b_data' results in a dereference of a null pointer (loaded from variable 'bp')
237 if (FAT12(pmp)(pmp->pm_fatmask == 0x00000fff) && (prevcn & 1))
238 cn >>= 4;
239 cn &= pmp->pm_fatmask;
240
241 /*
242 * Force the special cluster numbers
243 * to be the same for all cluster sizes
244 * to let the rest of msdosfs handle
245 * all cases the same.
246 */
247 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD0xfffffff6)
248 cn |= ~pmp->pm_fatmask;
249 }
250
251 if (!MSDOSFSEOF(pmp, cn)((((cn) | ~(pmp)->pm_fatmask) & 0xfffffff8) == 0xfffffff8
)) {
252 if (bp)
253 brelse(bp);
254 if (bnp)
255 *bnp = cntobn(pmp, cn)((((cn)-2) << (((pmp))->pm_cnshift - ((pmp))->pm_bnshift
)) + (pmp)->pm_firstcluster);
256 if (cnp)
257 *cnp = cn;
258 fc_setcache(dep, FC_LASTMAP, i, cn)(dep)->de_fc[0].fc_frcn = i; (dep)->de_fc[0].fc_fsrcn =
cn;;
259 return (0);
260 }
261
262hiteof:
263 if (cnp)
264 *cnp = i;
265 if (bp)
266 brelse(bp);
267 /* update last file cluster entry in the fat cache */
268 fc_setcache(dep, FC_LASTFC, i - 1, prevcn)(dep)->de_fc[1].fc_frcn = i - 1; (dep)->de_fc[1].fc_fsrcn
= prevcn;;
269 return (E2BIG7);
270}
271
272/*
273 * Find the closest entry in the fat cache to the cluster we are looking
274 * for.
275 */
276void
277fc_lookup(struct denode *dep, uint32_t findcn, uint32_t *frcnp, uint32_t *fsrcnp)
278{
279 int i;
280 uint32_t cn;
281 struct fatcache *closest = 0;
282
283 for (i = 0; i < FC_SIZE3; i++) {
284 cn = dep->de_fc[i].fc_frcn;
285 if (cn != FCE_EMPTY0xffffffff && cn <= findcn) {
286 if (closest == 0 || cn > closest->fc_frcn)
287 closest = &dep->de_fc[i];
288 }
289 }
290 if (closest) {
291 *frcnp = closest->fc_frcn;
292 *fsrcnp = closest->fc_fsrcn;
293 }
294}
295
296/*
297 * Purge the fat cache in denode dep of all entries relating to file
298 * relative cluster frcn and beyond.
299 */
300void
301fc_purge(struct denode *dep, u_int frcn)
302{
303 int i;
304 struct fatcache *fcp;
305
306 fcp = dep->de_fc;
307 for (i = 0; i < FC_SIZE3; i++, fcp++) {
308 if (fcp->fc_frcn >= frcn)
309 fcp->fc_frcn = FCE_EMPTY0xffffffff;
310 }
311}
312
313/*
314 * Update the fat.
315 * If mirroring the fat, update all copies, with the first copy as last.
316 * Else update only the current fat (ignoring the others).
317 *
318 * pmp - msdosfsmount structure for filesystem to update
319 * bp - addr of modified fat block
320 * fatbn - block number relative to begin of filesystem of the modified fat block.
321 */
322void
323updatefats(struct msdosfsmount *pmp, struct buf *bp, uint32_t fatbn)
324{
325 int i;
326 struct buf *bpn;
327
328#ifdef MSDOSFS_DEBUG
329 printf("updatefats(pmp %p, buf %p, fatbn %d)\n", pmp, bp, fatbn);
330#endif
331
332 /*
333 * If we have an FSInfo block, update it.
334 */
335 if (pmp->pm_fsinfo) {
336 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp)(1024 << ((pmp)->pm_BlkPerSec >> 2)),
337 &bpn) != 0) {
338 /*
339 * Ignore the error, but turn off FSInfo update for the future.
340 */
341 pmp->pm_fsinfo = 0;
342 brelse(bpn);
343 } else {
344 struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
345
346 putulong(fp->fsinfree, pmp->pm_freeclustercount)(*((u_int32_t *)(fp->fsinfree)) = (pmp->pm_freeclustercount
));
347 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT0x40000000)
348 bwrite(bpn);
349 else
350 bdwrite(bpn);
351 }
352 }
353
354 if (pmp->pm_flags & MSDOSFS_FATMIRROR0x20000000) {
355 /*
356 * Now copy the block(s) of the modified fat to the other copies of
357 * the fat and write them out. This is faster than reading in the
358 * other fats and then writing them back out. This could tie up
359 * the fat for quite a while. Preventing others from accessing it.
360 * To prevent us from going after the fat quite so much we use
361 * delayed writes, unless they specified "synchronous" when the
362 * filesystem was mounted. If synch is asked for then use
363 * bwrite()'s and really slow things down.
364 */
365 for (i = 1; i < pmp->pm_FATspm_bpb.bpbFATs; i++) {
366 fatbn += pmp->pm_FATsecs;
367 /* getblk() never fails */
368 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0,
369 INFSLP0xffffffffffffffffULL);
370 bcopy(bp->b_data, bpn->b_data, bp->b_bcount);
371 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT0x40000000)
372 bwrite(bpn);
373 else
374 bdwrite(bpn);
375 }
376 }
377
378 /*
379 * Write out the first (or current) fat last.
380 */
381 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT0x40000000)
382 bwrite(bp);
383 else
384 bdwrite(bp);
385 /*
386 * Maybe update fsinfo sector here?
387 */
388}
389
390/*
391 * Updating entries in 12 bit fats is a pain in the butt.
392 *
393 * The following picture shows where nibbles go when moving from a 12 bit
394 * cluster number into the appropriate bytes in the FAT.
395 *
396 * byte m byte m+1 byte m+2
397 * +----+----+ +----+----+ +----+----+
398 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
399 * +----+----+ +----+----+ +----+----+
400 *
401 * +----+----+----+ +----+----+----+
402 * | 3 0 1 | | 4 5 2 |
403 * +----+----+----+ +----+----+----+
404 * cluster n cluster n+1
405 *
406 * Where n is even. m = n + (n >> 2)
407 *
408 */
409static __inline void
410usemap_alloc(struct msdosfsmount *pmp, uint32_t cn)
411{
412
413 pmp->pm_inusemap[cn / N_INUSEBITS(8 * sizeof(u_int))] |= 1 << (cn % N_INUSEBITS(8 * sizeof(u_int)));
414 pmp->pm_freeclustercount--;
415}
416
417static __inline void
418usemap_free(struct msdosfsmount *pmp, uint32_t cn)
419{
420
421 pmp->pm_freeclustercount++;
422 pmp->pm_inusemap[cn / N_INUSEBITS(8 * sizeof(u_int))] &= ~(1 << (cn % N_INUSEBITS(8 * sizeof(u_int))));
423}
424
425int
426clusterfree(struct msdosfsmount *pmp, uint32_t cluster, uint32_t *oldcnp)
427{
428 int error;
429 uint32_t oldcn;
430
431 usemap_free(pmp, cluster);
432 error = fatentry(FAT_GET_AND_SET(0x0001 | 0x0002), pmp, cluster, &oldcn, MSDOSFSFREE0);
433 if (error) {
434 usemap_alloc(pmp, cluster);
435 return (error);
436 }
437 /*
438 * If the cluster was successfully marked free, then update
439 * the count of free clusters, and turn off the "allocated"
440 * bit in the "in use" cluster bit map.
441 */
442 if (oldcnp)
443 *oldcnp = oldcn;
444 return (0);
445}
446
447/*
448 * Get or Set or 'Get and Set' the cluster'th entry in the fat.
449 *
450 * function - whether to get or set a fat entry
451 * pmp - address of the msdosfsmount structure for the filesystem
452 * whose fat is to be manipulated.
453 * cn - which cluster is of interest
454 * oldcontents - address of a word that is to receive the contents of the
455 * cluster'th entry if this is a get function
456 * newcontents - the new value to be written into the cluster'th element of
457 * the fat if this is a set function.
458 *
459 * This function can also be used to free a cluster by setting the fat entry
460 * for a cluster to 0.
461 *
462 * All copies of the fat are updated if this is a set function. NOTE: If
463 * fatentry() marks a cluster as free it does not update the inusemap in
464 * the msdosfsmount structure. This is left to the caller.
465 */
466int
467fatentry(int function, struct msdosfsmount *pmp, uint32_t cn, uint32_t *oldcontents,
468 uint32_t newcontents)
469{
470 int error;
471 uint32_t readcn;
472 uint32_t bn, bo, bsize, byteoffset;
473 struct buf *bp;
474
475#ifdef MSDOSFS_DEBUG
476 printf("fatentry(func %d, pmp %p, clust %d, oldcon %p, "
477 "newcon %d)\n", function, pmp, cn, oldcontents, newcontents);
478#endif
479
480#ifdef DIAGNOSTIC1
481 /*
482 * Be sure they asked us to do something.
483 */
484 if ((function & (FAT_SET0x0002 | FAT_GET0x0001)) == 0) {
485 printf("fatentry(): function code doesn't specify get or set\n");
486 return (EINVAL22);
487 }
488
489 /*
490 * If they asked us to return a cluster number but didn't tell us
491 * where to put it, give them an error.
492 */
493 if ((function & FAT_GET0x0001) && oldcontents == NULL((void *)0)) {
494 printf("fatentry(): get function with no place to put result\n");
495 return (EINVAL22);
496 }
497#endif
498
499 /*
500 * Be sure the requested cluster is in the filesystem.
501 */
502 if (cn < CLUST_FIRST2 || cn > pmp->pm_maxcluster)
503 return (EINVAL22);
504
505 byteoffset = FATOFS(pmp, cn)((cn) * (pmp)->pm_fatmult / (pmp)->pm_fatdiv);
506 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
507 if ((error = bread(pmp->pm_devvp, bn, bsize, &bp)) != 0) {
508 brelse(bp);
509 return (error);
510 }
511
512 if (function & FAT_GET0x0001) {
513 if (FAT32(pmp)(pmp->pm_fatmask == 0x0fffffff))
514 readcn = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
515 else
516 readcn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
517 if (FAT12(pmp)(pmp->pm_fatmask == 0x00000fff) && (cn & 1))
518 readcn >>= 4;
519 readcn &= pmp->pm_fatmask;
520 /* map reserved fat entries to same values for all fats */
521 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD0xfffffff6)
522 readcn |= ~pmp->pm_fatmask;
523 *oldcontents = readcn;
524 }
525 if (function & FAT_SET0x0002) {
526 switch (pmp->pm_fatmask) {
527 case FAT12_MASK0x00000fff:
528 readcn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
529 if (cn & 1) {
530 readcn &= 0x000f;
531 readcn |= newcontents << 4;
532 } else {
533 readcn &= 0xf000;
534 readcn |= newcontents & 0xfff;
535 }
536 putushort(&bp->b_data[bo], readcn)(*((u_int16_t *)(&bp->b_data[bo])) = (readcn));
537 break;
538 case FAT16_MASK0x0000ffff:
539 putushort(&bp->b_data[bo], newcontents)(*((u_int16_t *)(&bp->b_data[bo])) = (newcontents));
540 break;
541 case FAT32_MASK0x0fffffff:
542 /*
543 * According to spec we have to retain the
544 * high order bits of the fat entry.
545 */
546 readcn = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
547 readcn &= ~FAT32_MASK0x0fffffff;
548 readcn |= newcontents & FAT32_MASK0x0fffffff;
549 putulong(&bp->b_data[bo], readcn)(*((u_int32_t *)(&bp->b_data[bo])) = (readcn));
550 break;
551 }
552 updatefats(pmp, bp, bn);
553 bp = NULL((void *)0);
554 pmp->pm_fmod = 1;
555 }
556 if (bp)
557 brelse(bp);
558 return (0);
559}
560
561/*
562 * Update a contiguous cluster chain
563 *
564 * pmp - mount point
565 * start - first cluster of chain
566 * count - number of clusters in chain
567 * fillwith - what to write into fat entry of last cluster
568 */
569static int
570fatchain(struct msdosfsmount *pmp, uint32_t start, uint32_t count, uint32_t fillwith)
571{
572 int error;
573 uint32_t bn, bo, bsize, byteoffset, readcn, newc;
574 struct buf *bp;
575
576#ifdef MSDOSFS_DEBUG
577 printf("fatchain(pmp %p, start %d, count %d, fillwith %d)\n",
578 pmp, start, count, fillwith);
579#endif
580 /*
581 * Be sure the clusters are in the filesystem.
582 */
583 if (start < CLUST_FIRST2 || start + count - 1 > pmp->pm_maxcluster)
584 return (EINVAL22);
585
586 while (count > 0) {
587 byteoffset = FATOFS(pmp, start)((start) * (pmp)->pm_fatmult / (pmp)->pm_fatdiv);
588 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
589 error = bread(pmp->pm_devvp, bn, bsize, &bp);
590 if (error) {
591 brelse(bp);
592 return (error);
593 }
594 while (count > 0) {
595 start++;
596 newc = --count > 0 ? start : fillwith;
597 switch (pmp->pm_fatmask) {
598 case FAT12_MASK0x00000fff:
599 readcn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
600 if (start & 1) {
601 readcn &= 0xf000;
602 readcn |= newc & 0xfff;
603 } else {
604 readcn &= 0x000f;
605 readcn |= newc << 4;
606 }
607 putushort(&bp->b_data[bo], readcn)(*((u_int16_t *)(&bp->b_data[bo])) = (readcn));
608 bo++;
609 if (!(start & 1))
610 bo++;
611 break;
612 case FAT16_MASK0x0000ffff:
613 putushort(&bp->b_data[bo], newc)(*((u_int16_t *)(&bp->b_data[bo])) = (newc));
614 bo += 2;
615 break;
616 case FAT32_MASK0x0fffffff:
617 readcn = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
618 readcn &= ~pmp->pm_fatmask;
619 readcn |= newc & pmp->pm_fatmask;
620 putulong(&bp->b_data[bo], readcn)(*((u_int32_t *)(&bp->b_data[bo])) = (readcn));
621 bo += 4;
622 break;
623 }
624 if (bo >= bsize)
625 break;
626 }
627 updatefats(pmp, bp, bn);
628 }
629 pmp->pm_fmod = 1;
630 return (0);
631}
632
633/*
634 * Check the length of a free cluster chain starting at start.
635 *
636 * pmp - mount point
637 * start - start of chain
638 * count - maximum interesting length
639 */
640int
641chainlength(struct msdosfsmount *pmp, uint32_t start, uint32_t count)
642{
643 uint32_t idx, max_idx;
644 u_int map;
645 uint32_t len;
646
647 max_idx = pmp->pm_maxcluster / N_INUSEBITS(8 * sizeof(u_int));
648 idx = start / N_INUSEBITS(8 * sizeof(u_int));
649 start %= N_INUSEBITS(8 * sizeof(u_int));
650 map = pmp->pm_inusemap[idx];
651 map &= ~((1 << start) - 1);
652 if (map) {
653 len = ffs(map) - 1 - start;
654 return (len > count ? count : len);
655 }
656 len = N_INUSEBITS(8 * sizeof(u_int)) - start;
657 if (len >= count)
658 return (count);
659 while (++idx <= max_idx) {
660 if (len >= count)
661 break;
662 if ((map = pmp->pm_inusemap[idx]) != 0) {
663 len += ffs(map) - 1;
664 break;
665 }
666 len += N_INUSEBITS(8 * sizeof(u_int));
667 }
668 return (len > count ? count : len);
669}
670
671/*
672 * Allocate contiguous free clusters.
673 *
674 * pmp - mount point.
675 * start - start of cluster chain.
676 * count - number of clusters to allocate.
677 * fillwith - put this value into the fat entry for the
678 * last allocated cluster.
679 * retcluster - put the first allocated cluster's number here.
680 * got - how many clusters were actually allocated.
681 */
682int
683chainalloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count,
684 uint32_t fillwith, uint32_t *retcluster, uint32_t *got)
685{
686 int error;
687 uint32_t cl, n;
688
689 for (cl = start, n = count; n-- > 0;)
690 usemap_alloc(pmp, cl++);
691 if ((error = fatchain(pmp, start, count, fillwith)) != 0)
692 return (error);
693#ifdef MSDOSFS_DEBUG
694 printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n",
695 start, count);
696#endif
697 if (retcluster)
698 *retcluster = start;
699 if (got)
700 *got = count;
701 return (0);
702}
703
704/*
705 * Allocate contiguous free clusters.
706 *
707 * pmp - mount point.
708 * start - preferred start of cluster chain.
709 * count - number of clusters requested.
710 * fillwith - put this value into the fat entry for the
711 * last allocated cluster.
712 * retcluster - put the first allocated cluster's number here.
713 * got - how many clusters were actually allocated.
714 */
715int
716clusteralloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count,
717 uint32_t *retcluster, uint32_t *got)
718{
719 uint32_t idx;
720 uint32_t len, newst, foundl, cn, l;
721 uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */
722 uint32_t fillwith = CLUST_EOFE0xffffffff;
723 u_int map;
724
725#ifdef MSDOSFS_DEBUG
726 printf("clusteralloc(): find %d clusters\n",count);
727#endif
728 if (start) {
729 if ((len = chainlength(pmp, start, count)) >= count)
730 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
731 } else {
732 /*
733 * This is a new file, initialize start
734 */
735 struct timeval tv;
736
737 microtime(&tv);
738 start = (tv.tv_usec >> 10) | tv.tv_usec;
739 len = 0;
740 }
741
742 /*
743 * Start at a (pseudo) random place to maximize cluster runs
744 * under multiple writers.
745 */
746 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
747 foundl = 0;
748
749 for (cn = newst; cn <= pmp->pm_maxcluster;) {
750 idx = cn / N_INUSEBITS(8 * sizeof(u_int));
751 map = pmp->pm_inusemap[idx];
752 map |= (1 << (cn % N_INUSEBITS(8 * sizeof(u_int)))) - 1;
753 if (map != (u_int)-1) {
754 cn = idx * N_INUSEBITS(8 * sizeof(u_int)) + ffs(map^(u_int)-1) - 1;
755 if ((l = chainlength(pmp, cn, count)) >= count)
756 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
757 if (l > foundl) {
758 foundcn = cn;
759 foundl = l;
760 }
761 cn += l + 1;
762 continue;
763 }
764 cn += N_INUSEBITS(8 * sizeof(u_int)) - cn % N_INUSEBITS(8 * sizeof(u_int));
765 }
766 for (cn = 0; cn < newst;) {
767 idx = cn / N_INUSEBITS(8 * sizeof(u_int));
768 map = pmp->pm_inusemap[idx];
769 map |= (1 << (cn % N_INUSEBITS(8 * sizeof(u_int)))) - 1;
770 if (map != (u_int)-1) {
771 cn = idx * N_INUSEBITS(8 * sizeof(u_int)) + ffs(map^(u_int)-1) - 1;
772 if ((l = chainlength(pmp, cn, count)) >= count)
773 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
774 if (l > foundl) {
775 foundcn = cn;
776 foundl = l;
777 }
778 cn += l + 1;
779 continue;
780 }
781 cn += N_INUSEBITS(8 * sizeof(u_int)) - cn % N_INUSEBITS(8 * sizeof(u_int));
782 }
783
784 if (!foundl)
785 return (ENOSPC28);
786
787 if (len)
788 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
789 else
790 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
791}
792
793
794/*
795 * Free a chain of clusters.
796 *
797 * pmp - address of the msdosfs mount structure for the filesystem
798 * containing the cluster chain to be freed.
799 * startcluster - number of the 1st cluster in the chain of clusters to be
800 * freed.
801 */
802int
803freeclusterchain(struct msdosfsmount *pmp, uint32_t cluster)
804{
805 int error;
806 struct buf *bp = NULL((void *)0);
807 uint32_t bn, bo, bsize, byteoffset;
808 uint32_t readcn, lbn = -1;
809
810 while (cluster >= CLUST_FIRST2 && cluster <= pmp->pm_maxcluster) {
811 byteoffset = FATOFS(pmp, cluster)((cluster) * (pmp)->pm_fatmult / (pmp)->pm_fatdiv);
812 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
813 if (lbn != bn) {
814 if (bp)
815 updatefats(pmp, bp, lbn);
816 error = bread(pmp->pm_devvp, bn, bsize, &bp);
817 if (error) {
818 brelse(bp);
819 return (error);
820 }
821 lbn = bn;
822 }
823 usemap_free(pmp, cluster);
824 switch (pmp->pm_fatmask) {
825 case FAT12_MASK0x00000fff:
826 readcn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
827 if (cluster & 1) {
828 cluster = readcn >> 4;
829 readcn &= 0x000f;
830 readcn |= MSDOSFSFREE0 << 4;
831 } else {
832 cluster = readcn;
833 readcn &= 0xf000;
834 readcn |= MSDOSFSFREE0 & 0xfff;
835 }
836 putushort(&bp->b_data[bo], readcn)(*((u_int16_t *)(&bp->b_data[bo])) = (readcn));
837 break;
838 case FAT16_MASK0x0000ffff:
839 cluster = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
840 putushort(&bp->b_data[bo], MSDOSFSFREE)(*((u_int16_t *)(&bp->b_data[bo])) = (0));
841 break;
842 case FAT32_MASK0x0fffffff:
843 cluster = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
844 putulong(&bp->b_data[bo],(*((u_int32_t *)(&bp->b_data[bo])) = ((0 & 0x0fffffff
) | (cluster & ~0x0fffffff)))
845 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK))(*((u_int32_t *)(&bp->b_data[bo])) = ((0 & 0x0fffffff
) | (cluster & ~0x0fffffff)));
846 break;
847 }
848 cluster &= pmp->pm_fatmask;
849 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD0xfffffff6)
850 cluster |= pmp->pm_fatmask;
851 }
852 if (bp)
853 updatefats(pmp, bp, bn);
854 return (0);
855}
856
857/*
858 * Read in fat blocks looking for free clusters. For every free cluster
859 * found turn off its corresponding bit in the pm_inusemap.
860 */
861int
862fillinusemap(struct msdosfsmount *pmp)
863{
864 struct buf *bp = NULL((void *)0);
865 uint32_t cn, readcn;
866 int error;
867 uint32_t bn, bo, bsize, byteoffset;
868
869 /*
870 * Mark all clusters in use, we mark the free ones in the fat scan
871 * loop further down.
872 */
873 for (cn = 0; cn < howmany(pmp->pm_maxcluster + 1, N_INUSEBITS)(((pmp->pm_maxcluster + 1) + (((8 * sizeof(u_int))) - 1)) /
((8 * sizeof(u_int)))); cn++)
874 pmp->pm_inusemap[cn] = (u_int)-1;
875
876 /*
877 * Figure how many free clusters are in the filesystem by ripping
878 * through the fat counting the number of entries whose content is
879 * zero. These represent free clusters.
880 */
881 pmp->pm_freeclustercount = 0;
882 for (cn = CLUST_FIRST2; cn <= pmp->pm_maxcluster; cn++) {
883 byteoffset = FATOFS(pmp, cn)((cn) * (pmp)->pm_fatmult / (pmp)->pm_fatdiv);
884 bo = byteoffset % pmp->pm_fatblocksize;
885 if (!bo || !bp) {
886 /* Read new FAT block */
887 if (bp)
888 brelse(bp);
889 fatblock(pmp, byteoffset, &bn, &bsize, NULL((void *)0));
890 error = bread(pmp->pm_devvp, bn, bsize, &bp);
891 if (error) {
892 brelse(bp);
893 return (error);
894 }
895 }
896 if (FAT32(pmp)(pmp->pm_fatmask == 0x0fffffff))
897 readcn = getulong(&bp->b_data[bo])*((u_int32_t *)(&bp->b_data[bo]));
898 else
899 readcn = getushort(&bp->b_data[bo])*((u_int16_t *)(&bp->b_data[bo]));
900 if (FAT12(pmp)(pmp->pm_fatmask == 0x00000fff) && (cn & 1))
901 readcn >>= 4;
902 readcn &= pmp->pm_fatmask;
903
904 if (readcn == 0)
905 usemap_free(pmp, cn);
906 }
907 brelse(bp);
908 return (0);
909}
910
911/*
912 * Allocate a new cluster and chain it onto the end of the file.
913 *
914 * dep - the file to extend
915 * count - number of clusters to allocate
916 * bpp - where to return the address of the buf header for the first new
917 * file block
918 * ncp - where to put cluster number of the first newly allocated cluster
919 * If this pointer is 0, do not return the cluster number.
920 * flags - see fat.h
921 *
922 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
923 * the de_flag field of the denode and it does not change the de_FileSize
924 * field. This is left for the caller to do.
925 */
926int
927extendfile(struct denode *dep, uint32_t count, struct buf **bpp, uint32_t *ncp,
928 int flags)
929{
930 int error;
931 uint32_t frcn;
932 uint32_t cn, got;
933 struct msdosfsmount *pmp = dep->de_pmp;
934 struct buf *bp;
935
936 /*
937 * Don't try to extend the root directory
938 */
939 if (dep->de_StartCluster == MSDOSFSROOT0
1
Assuming field 'de_StartCluster' is not equal to MSDOSFSROOT
→
940 && (dep->de_Attributes & ATTR_DIRECTORY0x10)) {
941 printf("extendfile(): attempt to extend root directory\n");
942 return (ENOSPC28);
943 }
944
945 /*
946 * If the "file's last cluster" cache entry is empty, and the file
947 * is not empty, then fill the cache entry by calling pcbmap().
948 */
949 fc_fileextends++;
950 if (dep->de_fc[FC_LASTFC1].fc_frcn == FCE_EMPTY0xffffffff &&
2
←
Assuming field 'fc_frcn' is equal to FCE_EMPTY
→
3
←
Taking true branch
→
951 dep->de_StartCluster
2.1
Field 'de_StartCluster' is not equal to 0
 != 0) {
952 fc_lfcempty++;
953 error = pcbmap(dep, CLUST_END0xffffffff, 0, &cn, 0);
4
←
Calling 'pcbmap'
→
954 /* we expect it to return E2BIG */
955 if (error != E2BIG7)
956 return (error);
957 }
958
959 /*
960 * Preserve value for the last cluster before extending the file
961 * to speed up further lookups.
962 */
963 fc_setcache(dep, FC_OLASTFC, dep->de_fc[FC_LASTFC].fc_frcn,(dep)->de_fc[2].fc_frcn = dep->de_fc[1].fc_frcn; (dep)->
de_fc[2].fc_fsrcn = dep->de_fc[1].fc_fsrcn;
964 dep->de_fc[FC_LASTFC].fc_fsrcn)(dep)->de_fc[2].fc_frcn = dep->de_fc[1].fc_frcn; (dep)->
de_fc[2].fc_fsrcn = dep->de_fc[1].fc_fsrcn;;
965
966 while (count > 0) {
967 /*
968 * Allocate a new cluster chain and cat onto the end of the
969 * file. * If the file is empty we make de_StartCluster point
970 * to the new block. Note that de_StartCluster being 0 is
971 * sufficient to be sure the file is empty since we exclude
972 * attempts to extend the root directory above, and the root
973 * dir is the only file with a startcluster of 0 that has
974 * blocks allocated (sort of).
975 */
976 if (dep->de_StartCluster == 0)
977 cn = 0;
978 else
979 cn = dep->de_fc[FC_LASTFC1].fc_fsrcn + 1;
980 error = clusteralloc(pmp, cn, count, &cn, &got);
981 if (error)
982 return (error);
983
984 count -= got;
985
986 /*
987 * Give them the filesystem relative cluster number if they want
988 * it.
989 */
990 if (ncp) {
991 *ncp = cn;
992 ncp = NULL((void *)0);
993 }
994
995 if (dep->de_StartCluster == 0) {
996 dep->de_StartCluster = cn;
997 frcn = 0;
998 } else {
999 error = fatentry(FAT_SET0x0002, pmp,
1000 dep->de_fc[FC_LASTFC1].fc_fsrcn,
1001 0, cn);
1002 if (error) {
1003 clusterfree(pmp, cn, NULL((void *)0));
1004 return (error);
1005 }
1006 frcn = dep->de_fc[FC_LASTFC1].fc_frcn + 1;
1007 }
1008
1009 /*
1010 * Update the "last cluster of the file" entry in the denode's fat
1011 * cache.
1012 */
1013 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1)(dep)->de_fc[1].fc_frcn = frcn + got - 1; (dep)->de_fc[
1].fc_fsrcn = cn + got - 1;;
1014
1015 if (flags & DE_CLEAR1) {
1016 while (got-- > 0) {
1017 /*
1018 * Get the buf header for the new block of the file.
1019 */
1020 if (dep->de_Attributes & ATTR_DIRECTORY0x10)
1021 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++)((((cn++)-2) << (((pmp))->pm_cnshift - ((pmp))->pm_bnshift
)) + (pmp)->pm_firstcluster),
1022 pmp->pm_bpcluster, 0, INFSLP0xffffffffffffffffULL);
1023 else {
1024 bp = getblk(DETOV(dep)((dep)->de_vnode), frcn++,
1025 pmp->pm_bpcluster, 0, INFSLP0xffffffffffffffffULL);
1026 /*
1027 * Do the bmap now, as in msdosfs_write
1028 */
1029 if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0, 0))
1030 bp->b_blkno = -1;
1031 if (bp->b_blkno == -1)
1032 panic("extendfile: pcbmap");
1033 }
1034 clrbuf(bp){ __builtin_bzero(((bp)->b_data), ((bp)->b_bcount)); (bp
)->b_resid = 0; };
1035 if (bpp) {
1036 *bpp = bp;
1037 bpp = NULL((void *)0);
1038 } else
1039 bdwrite(bp);
1040 }
1041 }
1042 }
1043
1044 return (0);
1045}