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Improve support for older BPB based volumes lacking extended fields.

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Based on lpproj's nec98:Fix for DOS 3.x partitions
5fab40fc63
On loading BPB check signature if extended fields (serial#, volume, and fstype) are available, use dummy values if not.
Return error if attempt to set BPB serial# and not part of BPB.
This commit is contained in:
KJD 2015-05-27 23:54:29 -04:00
parent 6e1274b1b3
commit 234ed1181f
1 changed files with 34 additions and 3 deletions
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37
kernel/dsk.c
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@ -413,16 +413,37 @@ STATIC WORD getbpb(ddt * pddt)
*/ */
{ {
struct FS_info *fs = (struct FS_info *)&DiskTransferBuffer[0x27]; struct FS_info *fs = (struct FS_info *)&DiskTransferBuffer[0x27];
register BYTE extended_BPB_signature;
#ifdef WITHFAT32 #ifdef WITHFAT32
if (pbpbarray->bpb_nfsect == 0) if (pbpbarray->bpb_nfsect == 0)
{ {
/* FAT32 boot sector */ /* FAT32 boot sector */
fs = (struct FS_info *)&DiskTransferBuffer[0x43]; fs = (struct FS_info *)&DiskTransferBuffer[0x43];
/* Extended BPB signature, offset differs for FAT32 vs FAT12/16 */
extended_BPB_signature = DiskTransferBuffer[0x42];
} }
else
#endif #endif
pddt->ddt_serialno = getlong(&fs->serialno); extended_BPB_signature = DiskTransferBuffer[0x26];
memcpy(pddt->ddt_volume, fs->volume, sizeof fs->volume);
memcpy(pddt->ddt_fstype, fs->fstype, sizeof fs->fstype); /* 0x29 is usual signature value for serial#,vol label,& fstype;
0x28 older EBPB signature indicating only serial# is valid */
if ((extended_BPB_signature == 0x29) || (extended_BPB_signature == 0x28))
{
pddt->ddt_serialno = getlong(&fs->serialno);
} else {
/* short BPB, no serial # available */
pddt->ddt_serialno = 0;
}
if (extended_BPB_signature == 0x29)
{
fmemcpy(pddt->ddt_volume, fs->volume, sizeof fs->volume);
fmemcpy(pddt->ddt_fstype, fs->fstype, sizeof fs->fstype);
} else {
/* earlier extended BPB or short BPB, fields not available */
fmemcpy(pddt->ddt_volume, "NO NAME ", 11);
fmemcpy(pddt->ddt_fstype, "FAT?? ", 8);
}
} }
#ifdef DSK_DEBUG #ifdef DSK_DEBUG
@ -693,6 +714,15 @@ STATIC WORD Genblkdev(rqptr rp, ddt * pddt)
if (ret != 0) if (ret != 0)
return (ret); return (ret);
/* return error if media lacks extended BPB with serial # */
{
register BYTE extended_BPB_signature =
DiskTransferBuffer[(pddt->ddt_bpb.bpb_nfsect != 0 ? 0x26 : 0x42)];
if ((extended_BPB_signature != 0x29) || (extended_BPB_signature != 0x28))
return failure(E_MEDIA);
}
/* otherwise, store serial # in extended BPB */
fs = (struct FS_info *)&DiskTransferBuffer fs = (struct FS_info *)&DiskTransferBuffer
[(pddt->ddt_bpb.bpb_nfsect != 0 ? 0x27 : 0x43)]; [(pddt->ddt_bpb.bpb_nfsect != 0 ? 0x27 : 0x43)];
fs->serialno = gioc->ioc_serialno; fs->serialno = gioc->ioc_serialno;
@ -750,6 +780,7 @@ STATIC WORD Genblkdev(rqptr rp, ddt * pddt)
if (ret != 0) if (ret != 0)
return (ret); return (ret);
/* Note: getbpb() will initialize extended BPB fields with default values */
gioc->ioc_serialno = pddt->ddt_serialno; gioc->ioc_serialno = pddt->ddt_serialno;
fmemcpy(gioc->ioc_volume, pddt->ddt_volume, 11); fmemcpy(gioc->ioc_volume, pddt->ddt_volume, 11);
fmemcpy(gioc->ioc_fstype, pddt->ddt_fstype, 8); fmemcpy(gioc->ioc_fstype, pddt->ddt_fstype, 8);