Branch data     Line data    Source code

       1                 :             : #include <stdint.h>
       2                 :             : 
       3                 :             : #include "common.h"
       4                 :             : #include "mbr.h"
       5                 :             : 
       6                 :             : #define BOOT_SIGNATURE_OFFSET 0x1FE
       7                 :             : #define MBR_PT_OFFSET 0x1BE
       8                 :             : #define MBR_PT_SIZE 16
       9                 :             : #define MBR_TYPE_OFF 4
      10                 :             : #define MBR_LBA_OFF 8
      11                 :             : 
      12                 :           5 : w_status_t mbr_parse(uint8_t *first_sector, uint8_t partition_type, uint32_t *sector_lba) {
      13         [ +  + ]:           5 :         if (!first_sector || !sector_lba) {
      14                 :             :                 return W_INVALID_PARAM;
      15                 :             :         }
      16                 :             : 
      17                 :             :         // Boot signature starts at 0x01FE in the first sector
      18                 :             :         uint8_t *boot_signature = first_sector + BOOT_SIGNATURE_OFFSET;
      19                 :             :         // Boot signature check
      20   [ +  +  -  + ]:           3 :         if (boot_signature[0] != 0x55 || boot_signature[1] != 0xAA) {
      21                 :             :                 return W_FAILURE;
      22                 :             :         }
      23                 :             : 
      24                 :             :         // Set sector_lba to 0 as default
      25                 :           2 :         *sector_lba = 0;
      26                 :             : 
      27                 :             :         // First partition entry starts at 0x01BE in the first sector
      28                 :           2 :         uint8_t *entry = first_sector + MBR_PT_OFFSET;
      29                 :             : 
      30                 :             :         // Each partition entry has a size of 16 bytes
      31         [ +  + ]:           6 :         for (int i = 0; i < 4; i++, entry += MBR_PT_SIZE) {
      32                 :             :                 // Partition type locates at 0x04 in each partition
      33                 :           5 :                 uint8_t type = entry[MBR_TYPE_OFF];
      34         [ +  + ]:           5 :                 if (type == partition_type) {
      35                 :           1 :                         *sector_lba = (uint32_t)entry[MBR_LBA_OFF] | ((uint32_t)entry[MBR_LBA_OFF + 1] << 8) |
      36                 :           1 :                                                   ((uint32_t)entry[MBR_LBA_OFF + 2] << 16) |
      37                 :           1 :                                                   ((uint32_t)entry[MBR_LBA_OFF + 3] << 24);
      38                 :           1 :                         return W_SUCCESS;
      39                 :             :                 }
      40                 :             :         }
      41                 :             :         return W_FAILURE;
      42                 :             : }