/* ----------------------------------------------------------------------- *
*
* Copyright 2009 Pierre-Alexandre Meyer
*
* Some parts borrowed from chain.c32:
*
* Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
* Copyright 2009 Intel Corporation; author: H. Peter Anvin
*
* This file is part of Syslinux, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
#include <stdlib.h>
#include <disk/common.h>
#include <disk/geom.h>
#include <disk/msdos.h>
#include <disk/partition.h>
#include <disk/read.h>
static inline int is_extended_partition(struct part_entry *ptab)
{
return (ptab->ostype == 0x05 ||
ptab->ostype == 0x0f || ptab->ostype == 0x85);
}
static inline int msdos_magic_present(const char *ptab)
{
return (*(uint16_t *) (ptab + 0x1fe) == 0xaa55);
}
/**
* process_extended_partition - execute a callback for each partition contained listed in an ebr
* @drive_info: driveinfo struct describing the drive
* @partition_offset: Absolute start (lba) of the extended partition
* @ebr_offset: Relative start (lba) of the current ebr processed within
* the extended partition
* @callback: Callback to execute
* @error: Buffer for I/O errors
* @nb_part_seen: Number of partitions found on the disk so far
**/
static int process_extended_partition(struct driveinfo *drive_info,
const int partition_offset,
const int ebr_offset,
p_callback callback, int nb_part_seen)
{
int status = 0;
/* The ebr is located at the first sector of the extended partition */
char *ebr = malloc(SECTOR * sizeof(char));
if (read_sectors(drive_info, ebr, partition_offset + ebr_offset, 1) == -1)
goto abort;
/* Check msdos magic signature */
if (!msdos_magic_present(ebr))
goto abort;
struct part_entry *ptab =
(struct part_entry *)(ebr + PARTITION_TABLES_OFFSET);
for (int i = 0; i < 4; i++) {
if (status == -1)
goto abort;
if (!is_extended_partition(&ptab[i])) {
/*
* This EBR partition table entry points to the
* logical partition associated to that EBR
*/
int logical_partition_start = ebr_offset + ptab[i].start_lba;
/* Last EBR in the extended partition? */
if (!logical_partition_start)
continue;
/*
* Check for garbage:
* 3rd and 4th entries in an EBR should be zero
* Some (malformed) partitioning software still add some
* data partitions there.
*/
if (ptab[i].start_lba <= 0 || ptab[i].length <= 0)
continue;
nb_part_seen++;
callback(drive_info,
&ptab[i],
partition_offset + logical_partition_start, nb_part_seen);
} else
status = process_extended_partition(drive_info,
partition_offset,
ptab[i].start_lba,
callback, nb_part_seen);
}
free(ebr);
return 0;
abort:
free(ebr);
return -1;
}
/**
* process_mbr - execute a callback for each partition contained in an {m,e}br
* @drive_info: driveinfo struct describing the drive
* @ptab: Pointer to the partition table
* @callback: Callback to execute
**/
static int process_mbr(struct driveinfo *drive_info, struct part_entry *ptab,
p_callback callback)
{
int status = 0;
for (int i = 0; i < 4; i++) {
if (status == -1)
return -1;
if (ptab[i].start_sect > 0) {
if (is_extended_partition(&ptab[i])) {
callback(drive_info, &ptab[i], ptab[i].start_lba, i + 1);
status =
process_extended_partition(drive_info, ptab[i].start_lba, 0,
callback, 4);
} else
callback(drive_info, &ptab[i], ptab[i].start_lba, i + 1);
}
}
return 0;
}
/**
* parse_partition_table - execute a callback for each partition entry
* @d: driveinfo struct describing the drive
* @callback: Callback to execute
*
* The signature of the callback should be the following:
*
* void callback(struct driveinfo *drive_info,
* struct part_entry *ptab,
* int offset_root,
* int nb_part_seen)
**/
int parse_partition_table(struct driveinfo *d, p_callback callback)
{
char *mbr = malloc(SECTOR * sizeof(char));
if (read_mbr(d->disk, mbr) == -1)
return -1;
else {
/* Check msdos magic signature */
if (!msdos_magic_present(mbr))
return -1;
struct part_entry *ptab =
(struct part_entry *)(mbr + PARTITION_TABLES_OFFSET);
return process_mbr(d, ptab, callback);
}
}
