xref: /titanic_52/usr/src/grub/grub-0.97/stage2/fat.h (revision 1b8adde7ba7d5e04395c141c5400dc2cffd7d809)
1 /*
2  *  GRUB  --  GRand Unified Bootloader
3  *  Copyright (C) 2001  Free Software Foundation, Inc.
4  *
5  *  This program is free software; you can redistribute it and/or modify
6  *  it under the terms of the GNU General Public License as published by
7  *  the Free Software Foundation; either version 2 of the License, or
8  *  (at your option) any later version.
9  *
10  *  This program is distributed in the hope that it will be useful,
11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  *  GNU General Public License for more details.
14  *
15  *  You should have received a copy of the GNU General Public License
16  *  along with this program; if not, write to the Free Software
17  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18  */
19 
20 
21 /*
22  *  Defines for the FAT BIOS Parameter Block (embedded in the first block
23  *  of the partition.
24  */
25 
26 typedef __signed__ char __s8;
27 typedef unsigned char __u8;
28 typedef __signed__ short __s16;
29 typedef unsigned short __u16;
30 typedef __signed__ int __s32;
31 typedef unsigned int __u32;
32 
33 /* Note that some shorts are not aligned, and must therefore
34  * be declared as array of two bytes.
35  */
36 struct fat_bpb {
37 	__s8	ignored[3];	/* Boot strap short or near jump */
38 	__s8	system_id[8];	/* Name - can be used to special case
39 				   partition manager volumes */
40 	__u8	bytes_per_sect[2];	/* bytes per logical sector */
41 	__u8	sects_per_clust;/* sectors/cluster */
42 	__u8	reserved_sects[2];	/* reserved sectors */
43 	__u8	num_fats;	/* number of FATs */
44 	__u8	dir_entries[2];	/* root directory entries */
45 	__u8	short_sectors[2];	/* number of sectors */
46 	__u8	media;		/* media code (unused) */
47 	__u16	fat_length;	/* sectors/FAT */
48 	__u16	secs_track;	/* sectors per track */
49 	__u16	heads;		/* number of heads */
50 	__u32	hidden;		/* hidden sectors (unused) */
51 	__u32	long_sectors;	/* number of sectors (if short_sectors == 0) */
52 
53 	/* The following fields are only used by FAT32 */
54 	__u32	fat32_length;	/* sectors/FAT */
55 	__u16	flags;		/* bit 8: fat mirroring, low 4: active fat */
56 	__u8	version[2];	/* major, minor filesystem version */
57 	__u32	root_cluster;	/* first cluster in root directory */
58 	__u16	info_sector;	/* filesystem info sector */
59 	__u16	backup_boot;	/* backup boot sector */
60 	__u16	reserved2[6];	/* Unused */
61 };
62 
63 #define FAT_CVT_U16(bytarr) (* (__u16*)(bytarr))
64 
65 /*
66  *  Defines how to differentiate a 12-bit and 16-bit FAT.
67  */
68 
69 #define FAT_MAX_12BIT_CLUST       4087	/* 4085 + 2 */
70 
71 /*
72  *  Defines for the file "attribute" byte
73  */
74 
75 #define FAT_ATTRIB_OK_MASK        0x37
76 #define FAT_ATTRIB_NOT_OK_MASK    0xC8
77 #define FAT_ATTRIB_DIR            0x10
78 #define FAT_ATTRIB_LONGNAME       0x0F
79 
80 /*
81  *  Defines for FAT directory entries
82  */
83 
84 #define FAT_DIRENTRY_LENGTH       32
85 
86 #define FAT_DIRENTRY_ATTRIB(entry) \
87   (*((unsigned char *) (entry+11)))
88 #define FAT_DIRENTRY_VALID(entry) \
89   ( ((*((unsigned char *) entry)) != 0) \
90     && ((*((unsigned char *) entry)) != 0xE5) \
91     && !(FAT_DIRENTRY_ATTRIB(entry) & FAT_ATTRIB_NOT_OK_MASK) )
92 #define FAT_DIRENTRY_FIRST_CLUSTER(entry) \
93   ((*((unsigned short *) (entry+26)))+(*((unsigned short *) (entry+20)) << 16))
94 #define FAT_DIRENTRY_FILELENGTH(entry) \
95   (*((unsigned long *) (entry+28)))
96 
97 #define FAT_LONGDIR_ID(entry) \
98   (*((unsigned char *) (entry)))
99 #define FAT_LONGDIR_ALIASCHECKSUM(entry) \
100   (*((unsigned char *) (entry+13)))
101