readmbr.c

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


typedef struct {
  char data[446];
} mbr_bootstrap_loader_t;

typedef struct {
  char header;
  char cy_h_and_sector;
  char cy_t;
} chs_t;

typedef unsigned int uint32;

typedef struct {
  char flag;
  chs_t first_sector;
  char type;
  chs_t last_sector;
  uint32 first_sector_lba;
  uint32 sector_num;
} mbr_partition_entry_t;

typedef unsigned short mbr_boot_signiture_t;


int dump(char *buf, int size)
{
  int i, line, flag;

  if(size < 0)
    return -1;

  for(i=0, line=0, flag=1; i < size; i++){
    if(flag){
      printf("%04d: ", ++line);
      flag = 0;
    }

    printf("%02X", buf[i] & 0xFF);

    if((i & 0xf) == 15){
      printf("\n");
      flag = 1;
    }else{
      if((i & 0xf) == 7) printf(" ");
      printf(" ");
    }
  }

  printf("\n");

  return 0;
}


int main(void)
{
  FILE *fp;
  int size;

  if((fp = fopen("/dev/sda", "r")) == NULL){
    printf("file open failed.\n");
    exit(EXIT_FAILURE);
  }

  mbr_bootstrap_loader_t mbr_bootstrap_loader;
  mbr_partition_entry_t mbr_partition_entry[4];
  mbr_boot_signiture_t mbr_boot_signiture;

  size = fread(&mbr_bootstrap_loader, sizeof(mbr_bootstrap_loader_t), 1, fp);
  size = fread(mbr_partition_entry, sizeof(mbr_partition_entry_t), 4, fp);
  size = fread(&mbr_boot_signiture, sizeof(mbr_boot_signiture_t), 1, fp);

  fclose(fp);


  printf("\n");
  printf("Boot strap loader\n");
  dump(mbr_bootstrap_loader.data, sizeof(mbr_bootstrap_loader_t));
  printf("\n");

  int i;
  mbr_partition_entry_t entry;
  for(i=0; i<4; i++){
    entry = mbr_partition_entry[i];
    printf("Partition table entry [%u]\n", i);
    printf("  Flag: %02X\n", entry.flag & 0xFF);
    printf("  First sector(CHS): Cylinder=%u,Head=%u,Sector=%u\n",
        ((entry.first_sector.cy_h_and_sector & 0xC0) << 2) | (entry.first_sector.cy_t & 0xFF),
        entry.first_sector.header & 0xFF,
        entry.first_sector.cy_h_and_sector & 0x3F);
    printf("  Type: %02X\n", entry.type & 0xFF);
    printf("  Last sector(CHS): Cylinder=%u,Head=%u,Sector=%u\n",
        ((entry.last_sector.cy_h_and_sector & 0xC0) << 2) | (entry.last_sector.cy_t & 0xFF),
        entry.last_sector.header & 0xFF,
        entry.last_sector.cy_h_and_sector & 0x3F);
    printf("  First sector(LBA): %u\n", entry.first_sector_lba);
    printf("  Sector num: %u\n", entry.sector_num);
    printf("\n");
  }

  printf("Boot signiture: %02X\n", mbr_boot_signiture);
  printf("\n");

  return EXIT_SUCCESS;
}