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MBRInfo.c
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/****
* MBRInfo - IPL を除く MBR の情報を表示する。
* Copyright (C) 2020-2022 Takym.
*
* distributed under the MIT License.
****/
// 実行方法：wsl gcc MBRInfo.c -o MBRInfo.elf; ./MBRInfo.elf "ディスクイメージ"
// 参考
// http://elm-chan.org/docs/fat.html
// https://ja.wikipedia.org/wiki/%E3%83%9E%E3%82%B9%E3%82%BF%E3%83%BC%E3%83%96%E3%83%BC%E3%83%88%E3%83%AC%E3%82%B3%E3%83%BC%E3%83%89
// https://en.wikipedia.org/wiki/Master_boot_record
// https://uefi.org/specifications
// https://uefi.org/sites/default/files/resources/UEFI_Spec_2_9_2021_03_18.pdf
#ifdef __GNUC__
#define PACKED __attribute__((packed))
#else
#define PACKED
#endif
typedef unsigned char int8_t;
typedef unsigned short int16_t;
typedef unsigned int int32_t;
typedef struct _FAT_HEADER_ {
int8_t BS_JmpBoot[3];
int8_t BS_OEMName[8];
int16_t BPB_BytsPerSec;
int8_t BPB_SecPerClus;
int16_t BPB_RsvdSecCnt;
int8_t BPB_NumFATs;
int16_t BPB_RootEntCnt;
int16_t BPB_TotSec16;
int8_t BPB_Media;
int16_t BPB_FATSz16;
int16_t BPB_SecPerTrk;
int16_t BPB_NumHeads;
int32_t BPB_HiddSec;
int32_t BPB_TotSec32;
} PACKED FATHeader;
typedef struct _FAT_HEADER_12_16_ {
int8_t BS_DrvNum;
int8_t BS_Reserved;
int8_t BS_BootSig;
int32_t BS_VolID;
int8_t BS_VolLab[11];
int8_t BS_FilSysType[8];
} PACKED FATHeader1216;
typedef struct _FAT_HEADER_32_ {
int32_t BPB_FATSz32;
int16_t BPB_ExtFlags;
int8_t BPB_FSVer[2];
int32_t BPB_RootClus;
int16_t BPB_FSInfo;
int16_t BPB_BkBootSec;
int8_t BPB_Reserved[12];
int8_t BS_DrvNum;
int8_t BS_Reserved;
int8_t BS_BootSig;
int32_t BS_VolID;
int8_t BS_VolLab[11];
int8_t BS_FilSysType[8];
} PACKED FATHeader32;
typedef struct _PARTITION_RECORD_ {
int8_t BootIndicator;
int8_t StartingCHS[3];
int8_t OSType;
int8_t EndingCHS[3];
int32_t StartingLBA;
int32_t SizeInLBA;
} PACKED PartitionRecord;
typedef struct _PARTITION_TABLE_ {
PartitionRecord PartitionRecords[4];
} PACKED PartitionTable;
typedef struct _CHS_ {
int32_t Head;
int32_t Cylinder;
int32_t Sector;
} CHS;
CHS decodeCHS(int8_t chsData[3])
{
CHS chs;
chs.Head = chsData[0];
chs.Cylinder = chsData[2]
| ((chsData[1] & 0b11000000) << 2);
chs.Sector = chsData[1] & 0b00111111;
return chs;
}
#include <stdio.h>
#include <string.h>
#define MBR_SIZE 512
int main(int argc, char *argv[])
{
FILE *fp;
size_t sz;
char buf[MBR_SIZE];
char tmp[12];
int i;
FATHeader *fh;
FATHeader1216 *fh1216;
FATHeader32 *fh32;
PartitionTable *pt;
PartitionRecord *pr;
int8_t *bootSig;
CHS chs;
if (argc != 2) {
printf("Usage> %s <disk image file>\r\n", argv[0]);
return 1;
}
fp = fopen(argv[1], "rb");
if (fp == NULL) {
printf("Error: could not open the file \"%s\"\r\n", argv[1]);
return 1;
}
sz = fread(buf, 1, MBR_SIZE, fp);
if (sz != MBR_SIZE) {
printf("Error: could not read the file \"%s\"\r\n", argv[1]);
fclose(fp);
return 1;
}
fclose(fp);
fh = ((FATHeader *)(&buf[ 0]));
fh1216 = ((FATHeader1216 *)(&buf[ 36]));
fh32 = ((FATHeader32 *)(&buf[ 36]));
pt = ((PartitionTable *)(&buf[446]));
bootSig = ((int8_t *)(&buf[510]));
printf("FATHeader\r\n");
printf("---------\r\n");
printf(
"BS_JmpBoot : %02X %02X %02X\r\n",
((int32_t)(fh->BS_JmpBoot[0])),
((int32_t)(fh->BS_JmpBoot[1])),
((int32_t)(fh->BS_JmpBoot[2]))
);
strncpy(tmp, ((char *)(fh->BS_OEMName)), 8);
tmp[8] = '\0';
printf("BS_OEMName : %s\r\n", tmp);
printf("BPB_BytsPerSec : %d\r\n", ((int32_t)(fh->BPB_BytsPerSec)));
printf("BPB_SecPerClus : %d\r\n", ((int32_t)(fh->BPB_SecPerClus)));
printf("BPB_RsvdSecCnt : %d\r\n", ((int32_t)(fh->BPB_RsvdSecCnt)));
printf("BPB_NumFATs : %d\r\n", ((int32_t)(fh->BPB_NumFATs)));
printf("BPB_RootEntCnt : %d\r\n", ((int32_t)(fh->BPB_RootEntCnt)));
printf("BPB_TotSec16 : %d\r\n", ((int32_t)(fh->BPB_TotSec16)));
printf("BPB_Media : 0x%02X\r\n", ((int32_t)(fh->BPB_Media)));
printf("BPB_FATSz16 : %d\r\n", ((int32_t)(fh->BPB_FATSz16)));
printf("BPB_SecPerTrk : %d\r\n", ((int32_t)(fh->BPB_SecPerTrk)));
printf("BPB_NumHeads : %d\r\n", ((int32_t)(fh->BPB_NumHeads)));
printf("BPB_HiddSec : %d\r\n", ((int32_t)(fh->BPB_HiddSec)));
printf("BPB_TotSec32 : %d\r\n", ((int32_t)(fh->BPB_TotSec32)));
printf("\r\n\r\n");
printf("FATHeader1216\r\n");
printf("-------------\r\n");
printf("BS_DrvNum : 0x%02X\r\n", ((int32_t)(fh1216->BS_DrvNum)));
printf("BS_Reserved : 0x%02X\r\n", ((int32_t)(fh1216->BS_Reserved)));
printf("BS_BootSig : 0x%02X\r\n", ((int32_t)(fh1216->BS_BootSig)));
printf("BS_VolID : 0x%08X\r\n", ((int32_t)(fh1216->BS_VolID)));
strncpy(tmp, ((char *)(fh1216->BS_VolLab)), 11);
tmp[11] = '\0';
printf("BS_VolLab : %s\r\n", tmp);
strncpy(tmp, ((char *)(fh1216->BS_FilSysType)), 8);
tmp[8] = '\0';
printf("BS_FilSysType : %s\r\n", tmp);
printf("\r\n\r\n");
printf("FATHeader32\r\n");
printf("-----------\r\n");
printf("BPB_FATSz32 : %d\r\n", ((int32_t)(fh32->BPB_FATSz32)));
printf("BPB_ExtFlags : 0x%04X\r\n", ((int32_t)(fh32->BPB_ExtFlags)));
printf("BPB_FSVer : %d.%d\r\n", ((int32_t)(fh32->BPB_FSVer[0])), ((int32_t)(fh32->BPB_FSVer[1])));
printf("BPB_RootClus : %d\r\n", ((int32_t)(fh32->BPB_RootClus)));
printf("BPB_FSInfo : %d\r\n", ((int32_t)(fh32->BPB_FSInfo)));
printf("BPB_BkBootSec : %d\r\n", ((int32_t)(fh32->BPB_BkBootSec)));
printf("BPB_Reserved : ");
for (i = 0; i < 12; ++i) {
printf("0x%02X ", fh32->BPB_Reserved[i]);
}
printf("\r\n");
printf("BS_DrvNum : 0x%02X\r\n", ((int32_t)(fh32->BS_DrvNum)));
printf("BS_Reserved : 0x%02X\r\n", ((int32_t)(fh32->BS_Reserved)));
printf("BS_BootSig : 0x%02X\r\n", ((int32_t)(fh32->BS_BootSig)));
printf("BS_VolID : 0x%08X\r\n", ((int32_t)(fh32->BS_VolID)));
strncpy(tmp, ((char *)(fh32->BS_VolLab)), 11);
tmp[11] = '\0';
printf("BS_VolLab : %s\r\n", tmp);
strncpy(tmp, ((char *)(fh32->BS_FilSysType)), 8);
tmp[8] = '\0';
printf("BS_FilSysType : %s\r\n", tmp);
for (i = 0; i < 4; ++i) {
pr = &pt->PartitionRecords[i];
printf("\r\n\r\n");
printf("PartitionEntry #%d\r\n", i);
printf("------------------\r\n");
printf("BootIndicator : 0x%02X\r\n", ((int32_t)(pr->BootIndicator)));
chs = decodeCHS(pr->StartingCHS);
printf("StartingCHS : C = %d; H = %d; S = %d\r\n", chs.Cylinder, chs.Head, chs.Sector);
printf("OSType : 0x%02X\r\n", pr->OSType);
chs = decodeCHS(pr->EndingCHS);
printf("EndingCHS : C = %d; H = %d; S = %d\r\n", chs.Cylinder, chs.Head, chs.Sector);
printf("StartingLBA : 0x%08X\r\n", ((int32_t)(pr->StartingLBA)));
printf("SizeInLBA : %d\r\n", ((int32_t)(pr->SizeInLBA)));
}
printf("\r\n\r\n");
printf("Boot Signature = 0x%02X, 0x%02X\r\n", ((int32_t)(bootSig[0])), ((int32_t)(bootSig[1])));
return 0;
}