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done with readmbr tool

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mykola2312 2024-08-07 10:18:02 +03:00
parent 87a280ae0d
commit 9820f1e14b
1 changed files with 48 additions and 22 deletions
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70
src/readmbr.c
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@ -1,19 +1,14 @@
// program to read MBR and its partition table
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
typedef struct {
uint8_t cylinder;
uint8_t head;
uint8_t sector;
} __attribute__((packed)) chs_t;
typedef struct {
uint8_t attributes;
chs_t chs_first;
uint8_t chs_first[3];
uint8_t type;
chs_t chs_last;
uint8_t chs_last[3];
uint32_t lba_start;
uint32_t num_sectors;
} __attribute__((packed)) mbr_part_t;
@ -26,28 +21,59 @@ typedef struct {
uint16_t signature;
} __attribute__((packed)) mbr_t;
void decode_chs(const uint8_t* chs, uint16_t* cylinder, uint16_t* head, uint16_t* sector)
{
*head = chs[0];
*sector = chs[1] & 0x3F;
*cylinder = (((uint16_t)chs[1]) & 0xC0) << 2 | (uint16_t)chs[2];
}
int main(int argc, char** argv)
{
mbr_t mbr;
// if (argc < 2)
// {
// fputs("provide filename to disk image as first argument\n", stderr);
// return 1;
// }
if (argc < 2)
{
fputs("provide filename to disk image as first argument\n", stderr);
return 1;
}
// int fd = open(argv[1], O_RDONLY);
// if (fd < 0)
// {
// perror("failed to open disk image\n");
// return 1;
// }
int fd = open(argv[1], O_RDONLY);
if (fd < 0)
{
perror("failed to open disk image\n");
return 1;
}
if (read(fd, &mbr, sizeof(mbr_t)) < sizeof(mbr_t))
{
perror("failed to read MBR!\n");
close(fd);
return 1;
}
close(fd);
// close(fd);
printf("== Master Boot Record ==\n");
printf("Unique ID:\t%u\n", mbr.unique_id);
printf("Reserved:\t%u\n", (unsigned int)mbr.reserved);
for (unsigned i = 0; i < 4; i++)
{
const mbr_part_t* part = &mbr.part_table[i];
uint16_t cylinder, head, sector;
printf("%lu\n", sizeof(mbr_t));
printf("%lu\n", sizeof(mbr_part_t));
printf("Partition:\t%u\n", i);
printf("\tAttributes:\t%u (%s)\n", part->attributes, part->attributes & 0x80 ? "active" : "");
printf("\tType:%u\n", part->type);
decode_chs(part->chs_first, &cylinder, &head, &sector);
printf("\tCHS First:\tC %u\tH %u\tS %u\n", cylinder, head, sector);
decode_chs(part->chs_last, &cylinder, &head, &sector);
printf("\tCHS Last:\tC %u\tH %u\tS %u\n", cylinder, head, sector);
printf("\tLBA:\t%u\n", part->lba_start);
printf("\tTotal Sectors:\t%u\n", part->num_sectors);
}
return 0;
}