uapp/fsck-msdosfs/boot.c

35 readboot(int dosfs, struct bootblock *boot)
44 		perr("could not read boot block");
49 		pfatal("Invalid signature in boot block: %02x%02x",
54 	memset(boot, 0, sizeof *boot);
55 	boot->ValidFat = -1;
58 	boot->bpbBytesPerSec = block[11] + (block[12] << 8);
59 	boot->bpbSecPerClust = block[13];
60 	boot->bpbResSectors = block[14] + (block[15] << 8);
61 	boot->bpbFATs = block[16];
62 	boot->bpbRootDirEnts = block[17] + (block[18] << 8);
63 	boot->bpbSectors = block[19] + (block[20] << 8);
64 	boot->bpbMedia = block[21];
65 	boot->bpbFATsmall = block[22] + (block[23] << 8);
66 	boot->SecPerTrack = block[24] + (block[25] << 8);
67 	boot->bpbHeads = block[26] + (block[27] << 8);
68 	boot->bpbHiddenSecs = block[28] + (block[29] << 8) +
70 	boot->bpbHugeSectors = block[32] + (block[33] << 8) +
73 	boot->FATsecs = boot->bpbFATsmall;
75 	if (!boot->bpbRootDirEnts)
76 		boot->flags |= FAT32;
77 	if (boot->flags & FAT32) {
78 		boot->FATsecs = block[36] + (block[37] << 8)
81 			boot->ValidFat = block[40] & 0x0f;
90 		boot->bpbRootClust = block[44] + (block[45] << 8)
92 		boot->bpbFSInfo = block[48] + (block[49] << 8);
93 		boot->bpbBackup = block[50] + (block[51] << 8);
95 		if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec,
96 		    SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec
121 				if (lseek(dosfs, boot->bpbFSInfo *
122 				    boot->bpbBytesPerSec, SEEK_SET)
123 				    != boot->bpbFSInfo * boot->bpbBytesPerSec
131 				boot->bpbFSInfo = 0;
133 		if (boot->bpbFSInfo) {
134 			boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8)
137 			boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8)
142 		if (lseek(dosfs, boot->bpbBackup * boot->bpbBytesPerSec,
144 		    != boot->bpbBackup * boot->bpbBytesPerSec
161 			        boot->bpbBackup);
171 	boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
172 	    boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
173 	    boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
174 	    CLUST_FIRST * boot->bpbSecPerClust;
176 	if (boot->bpbBytesPerSec % DOSBOOTBLOCKSIZE_REAL != 0) {
177 		pfatal("Invalid sector size: %u", boot->bpbBytesPerSec);
180 	if (boot->bpbSecPerClust == 0) {
181 		pfatal("Invalid cluster size: %u", boot->bpbSecPerClust);
184 	if (boot->bpbSectors) {
185 		boot->bpbHugeSectors = 0;
186 		boot->NumSectors = boot->bpbSectors;
188 		boot->NumSectors = boot->bpbHugeSectors;
189 	boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
190 	    boot->bpbSecPerClust;
192 	if (boot->flags&FAT32)
193 		boot->ClustMask = CLUST32_MASK;
194 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK))
195 		boot->ClustMask = CLUST12_MASK;
196 	else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK))
197 		boot->ClustMask = CLUST16_MASK;
200 		       boot->NumClusters);
204 	switch (boot->ClustMask) {
206 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4;
209 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2;
212 		boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3;
216 	if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) {
218 		       boot->NumClusters, boot->FATsecs);
221 	boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
223 	boot->NumFiles = 1;
224 	boot->NumFree = 0;
228 	// exactly. The Linux FAT driver, however, marks a bit in the boot sector as
232 	int dirtybyte = boot->flags&FAT32 ? 0x41 : 0x25;
242 			perr("could not write boot block");
252 writefsinfo(int dosfs, struct bootblock *boot)
256 	if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
257 	    != boot->bpbFSInfo * boot->bpbBytesPerSec
262 	fsinfo[0x1e8] = (u_char)boot->FSFree;
263 	fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8);
264 	fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16);
265 	fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24);
266 	fsinfo[0x1ec] = (u_char)boot->FSNext;
267 	fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8);
268 	fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16);
269 	fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24);
270 	if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET)
271 	    != boot->bpbFSInfo * boot->bpbBytesPerSec