--- /dev/null
+/*
+ *
+ * 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/ioctl.h>
+#include <sys/utsname.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "gpt.h"
+
+#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
+#define SECTOR_SIZE 512 /* default */
+
+#define _GET_BYTE(x, n) ( ((x) >> (8 * (n))) & 0xff )
+
+#define _PED_SWAP64(x) ( (_GET_BYTE(x, 0) << 56) \
+ + (_GET_BYTE(x, 1) << 48) \
+ + (_GET_BYTE(x, 2) << 40) \
+ + (_GET_BYTE(x, 3) << 32) \
+ + (_GET_BYTE(x, 4) << 24) \
+ + (_GET_BYTE(x, 5) << 16) \
+ + (_GET_BYTE(x, 6) << 8) \
+ + (_GET_BYTE(x, 7) << 0) )
+
+#define PED_SWAP64(x) ((uint64_t) _PED_SWAP64( (uint64_t) (x) ))
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+# define CPU_TO_LE64(x) (x)
+#else
+# define CPU_TO_LE64(x) PED_SWAP64(x)
+#endif
+
+#define BLKSSZGET _IO(0x12,104) /* get block device sector size */
+#define BLKGETLASTSECT _IO(0x12,108) /* get last sector of block device */
+#define BLKGETSIZE _IO(0x12,96) /* return device size */
+#define BLKGETSIZE64 _IOR(0x12,114,size_t) /* return device size in bytes (u64 *arg) */
+
+#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;
+
+struct blkdev_ioctl_param {
+ unsigned int block;
+ size_t content_length;
+ char * block_contents;
+};
+
+static int
+_get_linux_version (void)
+{
+ static int kver = -1;
+ struct utsname uts;
+ int major;
+ int minor;
+ int teeny;
+
+ if (kver != -1)
+ return kver;
+ if (uname (&uts))
+ return kver = 0;
+ if (sscanf (uts.release, "%u.%u.%u", &major, &minor, &teeny) != 3)
+ return kver = 0;
+ return kver = KERNEL_VERSION (major, minor, teeny);
+}
+
+static unsigned int
+_get_sector_size (int fd)
+{
+ unsigned int sector_size;
+
+ if (_get_linux_version() < KERNEL_VERSION (2,3,0))
+ return SECTOR_SIZE;
+ if (ioctl (fd, BLKSSZGET, §or_size))
+ return SECTOR_SIZE;
+ return sector_size;
+}
+
+static uint64_t
+_get_num_sectors(int fd)
+{
+ int version = _get_linux_version();
+ unsigned long size;
+ uint64_t bytes=0;
+
+ if (version >= KERNEL_VERSION(2,5,4) ||
+ (version < KERNEL_VERSION(2,5,0) &&
+ version >= KERNEL_VERSION (2,4,18)))
+ {
+ if (ioctl(fd, BLKGETSIZE64, &bytes) == 0)
+ return bytes / _get_sector_size(fd);
+ }
+ if (ioctl (fd, BLKGETSIZE, &size))
+ return 0;
+ return size;
+}
+
+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
+ {
+ fprintf(stderr,
+ "last_lba(): I don't know how to handle files with mode %x\n",
+ s.st_mode);
+ sectors = 1;
+ }
+ return sectors - 1;
+}
+
+static ssize_t
+read_lastoddsector(int fd, uint64_t lba, void *buffer, size_t count)
+{
+ int rc;
+ struct blkdev_ioctl_param ioctl_param;
+
+ if (!buffer) return 0;
+
+ ioctl_param.block = 0; /* read the last sector */
+ ioctl_param.content_length = count;
+ ioctl_param.block_contents = buffer;
+
+ rc = ioctl(fd, BLKGETLASTSECT, &ioctl_param);
+ if (rc == -1) perror("read failed");
+
+ return !rc;
+}
+
+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;
+ ssize_t bytesread;
+
+ lseek(fd, offset, SEEK_SET);
+ bytesread = read(fd, buffer, bytes);
+
+ /* Kludge. This is necessary to read/write the last
+ block of an odd-sized disk, until Linux 2.5.x kernel fixes.
+ This is only used by gpt.c, and only to read
+ one sector, so we don't have to be fancy.
+ */
+ if (!bytesread && !(last_lba(fd) & 1) && lba == last_lba(fd))
+ bytesread = read_lastoddsector(fd, lba, buffer, bytes);
+ return bytesread;
+}
+
+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
projects / util-linux / commitdiff