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/*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*
*
* GPT (GUID Partition Table) signature detection. Based on libparted and
* util-linux/partx.
*
* Warning: this code doesn't do all GPT checks (CRC32, Protective MBR, ..).
* It's really GPT signature detection only.
*
* Copyright (C) 2007 Karel Zak <kzak@redhat.com>
*
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <sys/stat.h>
#include <sys/utsname.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include "gpt.h"
#include "blkdev.h"
#include "bitops.h"
#define GPT_HEADER_SIGNATURE 0x5452415020494645LL
#define GPT_PRIMARY_PARTITION_TABLE_LBA 1
typedef struct {
uint32_t time_low;
uint16_t time_mid;
uint16_t time_hi_and_version;
uint8_t clock_seq_hi_and_reserved;
uint8_t clock_seq_low;
uint8_t node[6];
} /* __attribute__ ((packed)) */ efi_guid_t;
/* commented out "__attribute__ ((packed))" to work around gcc bug (fixed
* in gcc3.1): __attribute__ ((packed)) breaks addressing on initialized
* data. It turns out we don't need it in this case, so it doesn't break
* anything :)
*/
typedef struct _GuidPartitionTableHeader_t {
uint64_t Signature;
uint32_t Revision;
uint32_t HeaderSize;
uint32_t HeaderCRC32;
uint32_t Reserved1;
uint64_t MyLBA;
uint64_t AlternateLBA;
uint64_t FirstUsableLBA;
uint64_t LastUsableLBA;
efi_guid_t DiskGUID;
uint64_t PartitionEntryLBA;
uint32_t NumberOfPartitionEntries;
uint32_t SizeOfPartitionEntry;
uint32_t PartitionEntryArrayCRC32;
uint8_t Reserved2[512 - 92];
} __attribute__ ((packed)) GuidPartitionTableHeader_t;
static int
_get_sector_size (int fd)
{
int sector_size;
if (blkdev_get_sector_size(fd, §or_size) == -1)
return DEFAULT_SECTOR_SIZE;
return sector_size;
}
static uint64_t
_get_num_sectors(int fd)
{
unsigned long long bytes=0;
if (blkdev_get_size(fd, &bytes) == -1)
return 0;
return bytes / _get_sector_size(fd);
}
static uint64_t
last_lba(int fd)
{
int rc;
uint64_t sectors = 0;
struct stat s;
memset(&s, 0, sizeof (s));
rc = fstat(fd, &s);
if (rc == -1)
{
fprintf(stderr, "last_lba() could not stat: %s\n",
strerror(errno));
return 0;
}
if (S_ISBLK(s.st_mode))
sectors = _get_num_sectors(fd);
else if (S_ISREG(s.st_mode))
sectors = s.st_size >> _get_sector_size(fd);
else
{
fprintf(stderr,
"last_lba(): I don't know how to handle files with mode %o\n",
s.st_mode);
sectors = 1;
}
return sectors - 1;
}
static ssize_t
read_lba(int fd, uint64_t lba, void *buffer, size_t bytes)
{
int sector_size = _get_sector_size(fd);
off_t offset = lba * sector_size;
lseek(fd, offset, SEEK_SET);
return read(fd, buffer, bytes);
}
static GuidPartitionTableHeader_t *
alloc_read_gpt_header(int fd, uint64_t lba)
{
GuidPartitionTableHeader_t *gpt =
(GuidPartitionTableHeader_t *) malloc(sizeof (GuidPartitionTableHeader_t));
if (!gpt)
return NULL;
memset(gpt, 0, sizeof (*gpt));
if (!read_lba(fd, lba, gpt, sizeof (GuidPartitionTableHeader_t)))
{
free(gpt);
return NULL;
}
return gpt;
}
static int
gpt_check_signature(int fd, uint64_t lba)
{
GuidPartitionTableHeader_t *gpt;
int res=0;
if ((gpt = alloc_read_gpt_header(fd, lba)))
{
if (gpt->Signature == cpu_to_le64(GPT_HEADER_SIGNATURE))
res = 1;
free(gpt);
}
return res;
}
/* returns:
* 0 not found GPT
* 1 for valid primary GPT header
* 2 for valid alternative GPT header
*/
int
gpt_probe_signature_fd(int fd)
{
int res = 0;
/* check primary GPT header */
if (gpt_check_signature(fd, GPT_PRIMARY_PARTITION_TABLE_LBA))
res = 1;
else
{
/* check alternative GPT header */
uint64_t lastlba = last_lba(fd);
if (gpt_check_signature(fd, lastlba))
res = 2;
}
return res;
}
int
gpt_probe_signature_devname(char *devname)
{
int res, fd;
if ((fd = open(devname, O_RDONLY)) < 0)
return 0;
res = gpt_probe_signature_fd(fd);
close(fd);
return res;
}
#ifdef GPT_TEST_MAIN
int
main(int argc, char **argv)
{
if (argc!=2)
{
fprintf(stderr, "usage: %s <dev>\n", argv[0]);
exit(EXIT_FAILURE);
}
if (gpt_probe_signature_devname(argv[1]))
printf("GPT (GUID Partition Table) detected on %s\n", argv[1]);
exit(EXIT_SUCCESS);
}
#endif
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