sbin/fsck_msdosfs/boot.c

29 __RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp ");
43 readboot(int dosfs, struct bootblock *boot)
52 		perr("could not read boot block");
57 		pfatal("Invalid signature in boot block: %02x%02x",
62 	memset(boot, 0, sizeof *boot);
63 	boot->ValidFat = -1;
66 	boot->bpbBytesPerSec = block[11] + (block[12] << 8);
67 	boot->bpbSecPerClust = block[13];
68 	boot->bpbResSectors = block[14] + (block[15] << 8);
69 	boot->bpbFATs = block[16];
70 	boot->bpbRootDirEnts = block[17] + (block[18] << 8);
71 	boot->bpbSectors = block[19] + (block[20] << 8);
72 	boot->bpbMedia = block[21];
73 	boot->bpbFATsmall = block[22] + (block[23] << 8);
74 	boot->SecPerTrack = block[24] + (block[25] << 8);
75 	boot->bpbHeads = block[26] + (block[27] << 8);
76 	boot->bpbHiddenSecs = block[28] + (block[29] << 8) +
78 	boot->bpbHugeSectors = block[32] + (block[33] << 8) +
81 	boot->FATsecs = boot->bpbFATsmall;
83 	if (!boot->bpbRootDirEnts)
84 		boot->flags |= FAT32;
85 	if (boot->flags & FAT32) {
86 		boot->FATsecs = block[36] + (block[37] << 8)
89 			boot->ValidFat = block[40] & 0x0f;
98 		boot->bpbRootClust = block[44] + (block[45] << 8)
100 		boot->bpbFSInfo = block[48] + (block[49] << 8);
101 		boot->bpbBackup = block[50] + (block[51] << 8);
103 		if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
104 		    SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
129 				if (lseek(dosfs, boot->bpbFSInfo *
130 				    boot->bpbBytesPerSec, SEEK_SET)
131 				    != boot->bpbFSInfo * boot->bpbBytesPerSec
139 				boot->bpbFSInfo = 0;
141 		if (boot->bpbFSInfo) {
142 			boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
145 			boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
150 		if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec,
152 		    != boot->bpbBackup * boot->bpbBytesPerSec
169 			        boot->bpbBackup);
179 	boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
180 	    boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
181 	    boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
182 	    CLUST_FIRST * boot->bpbSecPerClust;
184 	if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE != 0) {
185 		pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
188 	if (boot->bpbSecPerClust == 0) {
189 		pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
192 	if (boot->bpbSectors) {
193 		boot->bpbHugeSectors = 0;
194 		boot->NumSectors = boot->bpbSectors;
196 		boot->NumSectors = boot->bpbHugeSectors;
197 	boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
198 	    boot->bpbSecPerClust;
200 	if (boot->flags&FAT32)
201 		boot->ClustMask = CLUST32_MASK;
202 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
203 		boot->ClustMask = CLUST12_MASK;
204 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
205 		boot->ClustMask = CLUST16_MASK;
208 		       boot->NumClusters);
212 	switch (boot->ClustMask) {
214 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
217 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
220 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
224 	if (boot->NumFatEntries < boot->NumClusters) {
226 		       boot->NumClusters, boot->FATsecs);
229 	boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
231 	boot->NumFiles = 1;
232 	boot->NumFree = 0;
238 writefsinfo(int dosfs, struct bootblock *boot)
242 	if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
243 	    != boot->bpbFSInfo * boot->bpbBytesPerSec
248 	fsinfo[0x1e8] = (u_char)boot->FSFree;
249 	fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
250 	fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
251 	fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
252 	fsinfo[0x1ec] = (u_char)boot->FSNext;
253 	fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
254 	fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
255 	fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
256 	if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
257 	    != boot->bpbFSInfo * boot->bpbBytesPerSec