AOS开发 02 - FAT32的世界

alias hexdump='echo "---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------" && hexdump -C'

# akvicor @ office in ~ [0:43:45] 
$ sudo mkfs.vfat /dev/sda
mkfs.fat 4.2 (2021-01-31)

# akvicor @ office in ~ [0:45:01] 
$ hexdump -n 512 /dev/sda
---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
00000000  eb 58 90 6d 6b 66 73 2e  66 61 74 00 02 20 20 00  |.X.mkfs.fat..  .|
00000010  02 00 00 00 00 f8 00 00  20 00 40 00 00 00 00 00  |........ .@.....|
00000020  e0 51 b8 03 80 3b 00 00  00 00 00 00 02 00 00 00  |.Q...;..........|
00000030  01 00 06 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  80 00 29 3d ec 7d d6 4e  4f 20 4e 41 4d 45 20 20  |..)=.}.NO NAME  |
00000050  20 20 46 41 54 33 32 20  20 20 0e 1f be 77 7c ac  |  FAT32   ...w|.|
00000060  22 c0 74 0b 56 b4 0e bb  07 00 cd 10 5e eb f0 32  |".t.V.......^..2|
00000070  e4 cd 16 cd 19 eb fe 54  68 69 73 20 69 73 20 6e  |.......This is n|
00000080  6f 74 20 61 20 62 6f 6f  74 61 62 6c 65 20 64 69  |ot a bootable di|
00000090  73 6b 2e 20 20 50 6c 65  61 73 65 20 69 6e 73 65  |sk.  Please inse|
000000a0  72 74 20 61 20 62 6f 6f  74 61 62 6c 65 20 66 6c  |rt a bootable fl|
000000b0  6f 70 70 79 20 61 6e 64  0d 0a 70 72 65 73 73 20  |oppy and..press |
000000c0  61 6e 79 20 6b 65 79 20  74 6f 20 74 72 79 20 61  |any key to try a|
000000d0  67 61 69 6e 20 2e 2e 2e  20 0d 0a 00 00 00 00 00  |gain ... .......|
000000e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200

# akvicor @ office in ~/workspace/test [0:55:07] 
$ cat boot.asm 
[bits 16]
org 0x7c00

jmp short 0x7c04


# akvicor @ office in ~/workspace/test [0:55:10] 
$ nasm boot.asm

# akvicor @ office in ~/workspace/test [0:55:11] 
$ hexdump boot
---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
00000000  eb 02                                             |..|
00000002

---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
00000000           6d 6b 66 73 2e  66 61 74 00 02 20 20 00  |   mkfs.fat..  .|
00000010  02 00 00 00 00 f8 00 00  20 00 40 00 00 00 00 00  |........ .@.....|
00000020  e0 51 b8 03 80 3b 00 00  00 00 00 00 02 00 00 00  |.Q...;..........|
00000030  01 00 06 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  80 00 29 3d ec 7d d6 4e  4f 20 4e 41 4d 45 20 20  |..)=.}.NO NAME  |
00000050  20 20 46 41 54 33 32 20  20 20                    |  FAT32         |

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda           8:0    1 29.8G  0 disk 
└─sda1        8:1    1 29.8G  0 part 

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda           8:0    1 29.8G  0 disk 

$ hexdump -s 512 -n 512 /dev/sda
---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F--------------------
00000200  52 52 61 41 00 00 00 00  00 00 00 00 00 00 00 00  |RRaA............|
00000210  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000003e0  00 00 00 00 72 72 41 61  d5 be 1d 00 02 00 00 00  |....rrAa........|
000003f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000400

---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
00004000  f8 ff ff 0f ff ff ff 0f  f8 ff ff 0f ff ff ff 0f  |................|
00004010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
0074a000  41 6c 00 6f 00 61 00 64  00 65 00 0f 00 ab 72 00  |Al.o.a.d.e....r.|
0074a010  2e 00 62 00 69 00 6e 00  00 00 00 00 ff ff ff ff  |..b.i.n.........|
0074a020  4c 4f 41 44 45 52 20 20  42 49 4e 20 00 00 e3 61  |LOADER  BIN ...a|
0074a030  8a 52 8a 52 00 00 e3 61  8a 52 03 00 11 00 00 00  |.R.R...a.R......|
0074a040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

---------- 0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F -------------------
0074b000  54 68 69 73 20 69 73 20  6c 6f 61 64 65 72 2e 73  |This is loader.s|
0074b010  0a 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0074b020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

// @Author : Akvicor
// @Created Time : 2021-08-09 10:46:34
// @Description : generate fat32.inc

#include <stdio.h>
#include <stdlib.h>

unsigned char * buffer = NULL;

char * template =
";----------------------------------------------- [DEF]\n"
"\n"
"%%define FAT32_BYTES_PER_SECTOR     0x%08X\n"
"%%define FAT32_SECTORS_PER_CLUSTER  0x%08X\n"
"%%define FAT32_BYTES_PER_CLUSTER    0x%08X\n"
"%%define FAT32_FAT_REGION           0x%08X\n"
"%%define FAT32_ROOT_REGION          0x%08X\n"
"\n"
";----------------------------------------------- [OEM Manufacturer; offset: 0x03; length: 8 Bytes]\n"
"\n"
"BPB_OEMName               DB    \"AKVICOR \"              ; 8 Bytes\n"
"\n"
";----------------------------------------------- [BIOS Parameter Block; offset: 0x0b; length: 25 Bytes]\n"
"\n"
"; The number of bytes, in little-endian\n"
"BPB_BytesPerSec           DW    0x%04X                  ; offset: 0x0b[11]; length: 2  Bytes\n"
"; Number of Sectors per Cluster\n"
"BPB_SecPerClus            DB    0x%02X                    ; offset: 0x0d[13]; length: 1  Bytes\n"
"; Number of Reserved Sectors\n"
"BPB_RsvdSecCnt            DW    0x%04X                  ; offset: 0x0e[14]; length: 2  Bytes\n"
"; Number of File Allocation Tables\n"
"BPB_NumFATs               DB    0x%02X                    ; offset: 0x10[16]; length: 1  Bytes\n"
"; Root Entries. The total number file name\n"
"; entires than can be store in the root folder\n"
"; of the volume.\n"
"; For FAT32 volumes, this number is set to zero\n"
"BPB_RootEntCnt            DW    0x%04X                  ; offset: 0x11[17]; length: 2  Bytes\n"
"; 0 For FAT32\n"
"BPB_TotSec16              DW    0x%04X                  ; offset: 0x13[19]; length: 2  Bytes\n"
"; Media Type: F0 removable,\n"
"; F8 fixed media, i.e. hard disk\n"
"BPB_Media                 DB    0x%02X                    ; offset: 0x15[21]; length: 1  Bytes\n"
"; For FAT32, this field should be zero\n"
"BPB_FATSz16               DW    0x%04X                  ; offset: 0x16[22]; length: 2  Bytes\n"
"; Sectors per track\n"
"BPB_SecPerTrk             DW    0x%04X                  ; offset: 0x18[24]; length: 2  Bytes\n"
"; Number of heads\n"
"BPB_NumHeads              DW    0x%04X                  ; offset: 0x1A[26]; length: 2  Bytes\n"
"; Count of hidden sectors preceeding the\n"
"; partition that contains the FAT volume\n"
"BPB_HiddSec               DD    0x%08X              ; offset: 0x1C[28]; length: 4  Bytes\n"
"; Total count of sectors\n"
"BPB_TotSec32              DD    0x%08X              ; offset: 0x20[32]; length: 4  Bytes\n"
"\n"
";----------------------------------------------- [Extended BIOS Parameter Block; offset: 0x24; length: 54 Bytes]\n"
"\n"
"; 32-bit count of sectors occupied by one FAT\n"
"BPB_FATSz32               DD    0x%08X               ; offset: 0x24[36]; length: 4  Bytes\n"
"; Bits [0-3 ]: Zero based number of active FAT\n"
"; Bits [4-6 ]: Reserved\n"
"; Bits [7   ]:\n"
";  0: The FAT is mirrored at runtime into all FATs\n"
";  1: Only one FAT is active\n"
"; Bits [8-15]: Reserved\n"
"BPB_ExtFlags              DW    0x%04X                   ; offset: 0x28[40]; length: 2  Bytes\n"
"; High Byte: Major revision number\n"
"; The sample value prevents windows\n"
"; from loading this FAT partition\n"
"BPB_FSVer                 DW    0x%04X                   ; offset: 0x2A[42]; length: 2  Bytes\n"
"; Cluster number of the first cluster\n"
"; of the root directory\n"
"BPB_RootClus              DD    0x%08X               ; offset: 0x2C[44]; length: 4  Bytes\n"
"; File system info. Usually 1\n"
"BPB_FSInfo                DW    0x%04X                   ; offset: 0x30[48]; length: 2  Bytes\n"
"; If not zero, indicates the sector number\n"
"; in the reserved area of the volume of a\n"
"; copy of the boot record\n"
"BPB_BkBootSec             DW    0x%04X                   ; offset: 0x32[50]; length: 2  Bytes\n"
"; Reserved\n"
"BPB_Reserved              TIMES 12 DB 0                  ; offset: 0x34[52]; length: 12 Bytes\n"
"; Drive Number\n"
"BS_DrvNum                 DB    0x%02X                     ; offset: 0x40[64]; length: 1  Bytes\n"
"; Reserved\n"
"BS_Reserved1              DB    0x%02X                     ; offset: 0x41[65]; length: 1  Bytes\n"
"; Boot signature\n"
"BS_BootSig                DB    0x%02X                     ; offset: 0x42[66]; length: 1  Bytes\n"
"; Volume ID\n"
"BS_VolID                  DD    0x%08X               ; offset: 0x43[67]; length: 4  Bytes\n"
"; Volume Label\n"
"BS_VolLab                 DB    \"AOS    BOOT\"            ; offset: 0x47[71]; length: 11 Bytes\n"
"; Volume ID\n"
"BS_FilSysType             DB    \"FAT32   \"               ; offset: 0x52[82]; length: 8  Bytes\n"
"\n"
";----------------------------------------------- [Bootstrap Code; offset: 0x5A[90]; length: 420 Bytes]\n"
;

int read_file(char * filename, unsigned char * buffer, unsigned int size) {
  if(buffer == NULL) {
    printf("buffer is NULL!\n");
    return -1;
  }
  FILE *file = fopen(filename, "r");
  if(file == NULL) {
    printf("open file failed!\n");
    return -2;
  }
  fread(buffer, size, 1, file);
  fclose(file);
}

int convert_to_fat32(unsigned char * buffer) {
  if(buffer == NULL) {
    printf("buffer is NULL!\n");
    return -1;
  }

  // Bytes per Cluster
  unsigned int bytes_per_sector = *(unsigned short*)(buffer+0x0b);
  unsigned int sectors_per_cluster = *(unsigned char*)(buffer+0x0d);
  unsigned int bytes_per_cluster = bytes_per_sector * sectors_per_cluster;

  // FAT Region
  unsigned int reserved_sectors_num = *(unsigned short*)(buffer+0x0e);
  unsigned int fat_region = reserved_sectors_num;

  // Root Directory Region
  unsigned int fat_size = *(unsigned int*)(buffer+0x24);
  unsigned int fat_num = *(unsigned char*)(buffer+0x10);
  unsigned int total_fat_sectors = fat_size * fat_num;
  unsigned int root_directory_region = reserved_sectors_num + total_fat_sectors;

  printf(template,
      bytes_per_sector,
      sectors_per_cluster,
      bytes_per_cluster,
      fat_region,
      root_directory_region,
      *(unsigned short*)(buffer+0x0b),
      *(unsigned char*)(buffer+0x0d),
      *(unsigned short*)(buffer+0x0e),
      *(unsigned char*)(buffer+0x10),
      *(unsigned short*)(buffer+0x11),
      *(unsigned short*)(buffer+0x13),
      *(unsigned char*)(buffer+0x15),
      *(unsigned short*)(buffer+0x16),
      *(unsigned short*)(buffer+0x18),
      *(unsigned short*)(buffer+0x1a),
      *(unsigned int*)(buffer+0x1c),
      *(unsigned int*)(buffer+0x20),
      *(unsigned int*)(buffer+0x24),
      *(unsigned short*)(buffer+0x28),
      *(unsigned short*)(buffer+0x2a),
      *(unsigned int*)(buffer+0x2c),
      *(unsigned short*)(buffer+0x30),
      *(unsigned short*)(buffer+0x32),
      *(unsigned char*)(buffer+0x40),
      *(unsigned char*)(buffer+0x41),
      *(unsigned char*)(buffer+0x42),
      *(unsigned int*)(buffer+0x43)
    );
}

int main(int argc, char *argv[]){
  if (argc < 2) {
    printf("用法: %s <设备路径>\n", argv[0]);
    printf("例如: %s /dev/sdb\n", argv[0]);
    return 1;
  }

  buffer = (unsigned char *)calloc(512, sizeof(unsigned char));
  if (buffer == NULL) {
    printf("内存分配失败\n");
    return 1;
  }

  read_file(argv[1], buffer, 512);

  convert_to_fat32(buffer);

  free(buffer);
  return 0;
}

gcc gen_fat32_inc.c -o gen_fat32_inc
sudo ./gen_fat32_inc /dev/sda > fat32.inc