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1/* $OpenBSD: bootsect.h,v 1.8 2025/08/01 13:00:18 jsg Exp $ */
2/* $NetBSD: bootsect.h,v 1.8 1997/10/17 11:23:29 ws Exp $ */
3
4/*
5 * Written by Paul Popelka (paulp@uts.amdahl.com)
6 *
7 * You can do anything you want with this software, just don't say you wrote
8 * it, and don't remove this notice.
9 *
10 * This software is provided "as is".
11 *
12 * The author supplies this software to be publicly redistributed on the
13 * understanding that the author is not responsible for the correct
14 * functioning of this software in any circumstances and is not liable for
15 * any damages caused by this software.
16 *
17 * October 1992
18 */
19
20/*
21 * Format of a boot sector. This is the first sector on a DOS floppy disk
22 * or the first sector of a partition on a hard disk. But, it is not the
23 * first sector of a partitioned hard disk.
24 */
25struct bootsector33 {
26 u_int8_t bsJump[3]; /* jump inst E9xxxx or EBxx90 */
27 int8_t bsOemName[8]; /* OEM name and version */
28 int8_t bsBPB[19]; /* BIOS parameter block */
29 int8_t bsDriveNumber; /* drive number (0x80) */
30 int8_t bsBootCode[479]; /* pad so struct is 512b */
31 u_int8_t bsBootSectSig0;
32 u_int8_t bsBootSectSig1;
33#define BOOTSIG0 0x55
34#define BOOTSIG1 0xaa
35};
36
37struct extboot {
38 int8_t exDriveNumber; /* drive number (0x80) */
39 int8_t exReserved1; /* reserved */
40 int8_t exBootSignature; /* ext. boot signature (0x29) */
41#define EXBOOTSIG 0x29
42 int8_t exVolumeID[4]; /* volume ID number */
43 int8_t exVolumeLabel[11]; /* volume label */
44 int8_t exFileSysType[8]; /* fs type (FAT12 or FAT16) */
45};
46
47struct bootsector50 {
48 u_int8_t bsJump[3]; /* jump inst E9xxxx or EBxx90 */
49 int8_t bsOemName[8]; /* OEM name and version */
50 int8_t bsBPB[25]; /* BIOS parameter block */
51 int8_t bsExt[26]; /* Bootsector Extension */
52 int8_t bsBootCode[448]; /* pad so structure is 512b */
53 u_int8_t bsBootSectSig0;
54 u_int8_t bsBootSectSig1;
55#define BOOTSIG0 0x55
56#define BOOTSIG1 0xaa
57};
58
59struct bootsector710 {
60 u_int8_t bsJump[3]; /* jump inst E9xxxx or EBxx90 */
61 int8_t bsOEMName[8]; /* OEM name and version */
62 int8_t bsBPB[53]; /* BIOS parameter block */
63 int8_t bsExt[26]; /* Bootsector Extension */
64 int8_t bsBootCode[418]; /* pad so structure is 512b */
65 u_int8_t bsBootSectSig2; /* 2 & 3 are only defined for FAT32? */
66 u_int8_t bsBootSectSig3;
67 u_int8_t bsBootSectSig0;
68 u_int8_t bsBootSectSig1;
69#define BOOTSIG0 0x55
70#define BOOTSIG1 0xaa
71#define BOOTSIG2 0
72#define BOOTSIG3 0
73};
74
75union bootsector {
76 struct bootsector33 bs33;
77 struct bootsector50 bs50;
78 struct bootsector710 bs710;
79};
80
81#if 0
82/*
83 * Shorthand for fields in the bpb.
84 */
85#define bsBytesPerSec bsBPB.bpbBytesPerSec
86#define bsSectPerClust bsBPB.bpbSectPerClust
87#define bsResSectors bsBPB.bpbResSectors
88#define bsFATS bsBPB.bpbFATS
89#define bsRootDirEnts bsBPB.bpbRootDirEnts
90#define bsSectors bsBPB.bpbSectors
91#define bsMedia bsBPB.bpbMedia
92#define bsFATsecs bsBPB.bpbFATsecs
93#define bsSectPerTrack bsBPB.bpbSectPerTrack
94#define bsHeads bsBPB.bpbHeads
95#define bsHiddenSecs bsBPB.bpbHiddenSecs
96#define bsHugeSectors bsBPB.bpbHugeSectors
97#endif