bootsector.h

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/*
    libparted
    Copyright (C) 1998-2000, 2007, 2009-2014, 2019-2023, 2026 Free Software
    Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#ifndef PED_FAT_BOOTSECTOR_H
#define PED_FAT_BOOTSECTOR_H
 
typedef struct _FatBootSector   FatBootSector;
typedef struct _FatInfoSector   FatInfoSector;
 
#include "fat.h"
 
#define FAT32_INFO_MAGIC1       0x41615252
#define FAT32_INFO_MAGIC2       0x61417272
#define FAT32_INFO_MAGIC3       0xaa55
 
/* stolen from mkdosfs, by Dave Hudson */
 
#define FAT_BOOT_MESSAGE        \
"This partition does not have an operating system loader installed on it.\n\r"\
"Press a key to reboot..."
 
#define FAT_BOOT_JUMP   "\xeb\x58\x90"          /* jmp  +5a */
 
#define FAT_BOOT_CODE   "\x0e"                  /* push cs */           \
                        "\x1f"                  /* pop ds */            \
                        "\xbe\x74\x7e"          /* mov si, offset message */ \
                                        /* write_msg_loop: */           \
                        "\xac"                  /* lodsb */             \
                        "\x22\xc0"              /* and al, al */        \
                        "\x74\x06"              /* jz done (+8) */      \
                        "\xb4\x0e"              /* mov ah, 0x0e */      \
                        "\xcd\x10"              /* int 0x10 */          \
                        "\xeb\xf5"              /* jmp write_msg_loop */ \
                                        /* done: */                     \
                        "\xb4\x00"              /* mov ah, 0x00 */      \
                        "\xcd\x16"              /* int 0x16 */          \
                        "\xb4\x00"              /* mov ah, 0x00 */      \
                        "\xcd\x19"              /* int 0x19 */          \
                        "\xeb\xfe"              /* jmp +0 - in case int 0x19 */ \
                                                /* doesn't work */      \
                                        /* message: */                  \
                        FAT_BOOT_MESSAGE
 
struct __attribute__ ((packed)) _FatBootSector {
        uint8_t         boot_jump[3];   /* 00: Boot strap short or near jump */
        uint8_t         system_id[8];   /* 03: system name */
        uint16_t        sector_size;    /* 0b: bytes per logical sector */
        uint8_t         cluster_size;   /* 0d: sectors/cluster */
        uint16_t        reserved;       /* 0e: reserved sectors */
        uint8_t         fats;           /* 10: number of FATs */
        uint16_t        dir_entries;    /* 11: number of root directory entries */
        uint16_t        sectors;        /* 13: if 0, total_sect supersedes */
        uint8_t         media;          /* 15: media code */
        uint16_t        fat_length;     /* 16: sectors/FAT for FAT12/16 */
        uint16_t        secs_track;     /* 18: sectors per track */
        uint16_t        heads;          /* 1a: number of heads */
        uint32_t        hidden;         /* 1c: hidden sectors (partition start) */
        uint32_t        sector_count;   /* 20: no. of sectors (if sectors == 0) */
 
        union __attribute__ ((packed)) {
                /* FAT16 fields */
                struct __attribute__ ((packed)) {
                        uint8_t         drive_num;      /* 24: */
                        uint8_t         empty_1;        /* 25: */
                        uint8_t         ext_signature;  /* 26: always 0x29 */
                        uint32_t        serial_number;  /* 27: */
                        uint8_t         volume_name [11];       /* 2b: */
                        uint8_t         fat_name [8];   /* 36: */
                        uint8_t         boot_code[448]; /* 3f: Boot code (or message) */
                } fat16;
                /* FAT32 fields */
                struct __attribute__ ((packed)) {
                        uint32_t        fat_length;     /* 24: size of FAT in sectors */
                        uint16_t        flags;          /* 28: bit8: fat mirroring, low4: active fat */
                        uint16_t        version;        /* 2a: minor * 256 + major */
                        uint32_t        root_dir_cluster;       /* 2c: */
                        uint16_t        info_sector;    /* 30: */
                        uint16_t        backup_sector;  /* 32: */
                        uint8_t         empty_1 [12];   /* 34: */
                        uint16_t        drive_num;      /* 40: */
                        uint8_t         ext_signature;  /* 42: always 0x29 */
                        uint32_t        serial_number;  /* 43: */
                        uint8_t         volume_name [11];       /* 47: */
                        uint8_t         fat_name [8];   /* 52: */
                        uint8_t         boot_code[420]; /* 5a: Boot code (or message) */
                } fat32;
        } u;
 
        uint16_t        boot_sign;      /* 1fe: always 0xAA55 */
};
 
struct __attribute__ ((packed)) _FatInfoSector {
        uint32_t        signature_1;    /* should be 0x41615252 */
        uint8_t         unused [480];
        uint32_t        signature_2;    /* should be 0x61417272 */
        uint32_t        free_clusters;
        uint32_t        next_cluster;   /* most recently allocated cluster */
        uint8_t         unused2 [0xe];
        uint16_t        signature_3;    /* should be 0xaa55 */
};
 
int fat_boot_sector_read (FatBootSector** bs, const PedGeometry* geom);
FatType fat_boot_sector_probe_type (const FatBootSector* bs,
                                    const PedGeometry* geom);
int fat_boot_sector_analyse (FatBootSector* bs, PedFileSystem* fs);
int fat_boot_sector_set_boot_code (FatBootSector** bs, const PedFileSystem* fs);
int fat_boot_sector_generate (FatBootSector** bs, const PedFileSystem* fs);
int fat_boot_sector_write (const FatBootSector* bs, PedFileSystem* fs);
 
int fat_info_sector_read (FatInfoSector** is, const PedFileSystem* fs);
int fat_info_sector_generate (FatInfoSector** is, const PedFileSystem* fs);
int fat_info_sector_write (const FatInfoSector* is, PedFileSystem* fs);
 
#endif /* PED_FAT_BOOTSECTOR_H */