qbootctl/gpt-utils.c

/*
 * Copyright (c) 2013, The Linux Foundation. All rights reserved.
 * Copyright (C) 2021-2022 Caleb Connolly <caleb@connolly.tech>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *     * Neither the name of The Linux Foundation nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#define _LARGEFILE64_SOURCE /* enable lseek64() */

#include <assert.h>
#include <asm/byteorder.h>
#include <ctype.h>
#include <stdlib.h>
#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <unistd.h>

#include "gpt-utils.h"
#include "utils.h"
#include "crc32.h"

/* list the names of the backed-up partitions to be swapped */
/* extension used for the backup partitions - tzbak, abootbak, etc. */
#define BAK_PTN_NAME_EXT "bak"
#define XBL_PRIMARY	 "/dev/disk/by-partlabel/xbl_a" // FIXME
#define XBL_BACKUP	 "/dev/disk/by-partlabel/xblbak"
#define XBL_AB_PRIMARY	 "/dev/disk/by-partlabel/xbl_a"
#define XBL_AB_SECONDARY "/dev/disk/by-partlabel/xbl_b"
/* GPT defines */
#define MAX_LUNS 26
// Size of the buffer that needs to be passed to the UFS ioctl
#define UFS_ATTR_DATA_SIZE 32
// This will allow us to get the root lun path from the path to the partition.
// i.e: from /dev/disk/sdaXXX get /dev/disk/sda. The assumption here is that
// the boot critical luns lie between sda to sdz which is acceptable because
// only user added external disks,etc would lie beyond that limit which do not
// contain partitions that interest us here.
#define PATH_TRUNCATE_LOC (sizeof("/dev/sda") - 1)

// From /dev/disk/sda get just sda
#define LUN_NAME_START_LOC (sizeof("/dev/") - 1)
#define BOOT_LUN_A_ID	   1
#define BOOT_LUN_B_ID	   2

#define GET_4_BYTES(ptr)                                                                           \
	((uint32_t) * ((uint8_t *)(ptr)) | ((uint32_t) * ((uint8_t *)(ptr) + 1) << 8) |            \
	 ((uint32_t) * ((uint8_t *)(ptr) + 2) << 16) | ((uint32_t) * ((uint8_t *)(ptr) + 3) << 24))

#define GET_8_BYTES(ptr)                                                                           \
	((uint64_t) * ((uint8_t *)(ptr)) | ((uint64_t) * ((uint8_t *)(ptr) + 1) << 8) |            \
	 ((uint64_t) * ((uint8_t *)(ptr) + 2) << 16) |                                             \
	 ((uint64_t) * ((uint8_t *)(ptr) + 3) << 24) |                                             \
	 ((uint64_t) * ((uint8_t *)(ptr) + 4) << 32) |                                             \
	 ((uint64_t) * ((uint8_t *)(ptr) + 5) << 40) |                                             \
	 ((uint64_t) * ((uint8_t *)(ptr) + 6) << 48) | ((uint64_t) * ((uint8_t *)(ptr) + 7) << 56))

#define PUT_4_BYTES(ptr, y)                                                                        \
	*((uint8_t *)(ptr)) = (y)&0xff;                                                            \
	*((uint8_t *)(ptr) + 1) = ((y) >> 8) & 0xff;                                               \
	*((uint8_t *)(ptr) + 2) = ((y) >> 16) & 0xff;                                              \
	*((uint8_t *)(ptr) + 3) = ((y) >> 24) & 0xff;

enum gpt_state { GPT_OK = 0, GPT_BAD_SIGNATURE, GPT_BAD_CRC };
// List of LUN's containing boot critical images.
// Required in the case of UFS devices
struct update_data {
	char lun_list[MAX_LUNS][GPT_PTN_PATH_MAX];
	uint32_t num_valid_entries;
};

void DumpHex(const void *data, size_t size)
{
	char ascii[17];
	size_t i, j;
	ascii[16] = '\0';
	for (i = 0; i < size; ++i) {
		printf("%02X ", ((unsigned char *)data)[i]);
		if (((unsigned char *)data)[i] >= ' ' && ((unsigned char *)data)[i] <= '~') {
			ascii[i % 16] = ((unsigned char *)data)[i];
		} else {
			ascii[i % 16] = '.';
		}
		if ((i + 1) % 8 == 0 || i + 1 == size) {
			printf(" ");
			if ((i + 1) % 16 == 0) {
				printf("|  %s \n", ascii);
			} else if (i + 1 == size) {
				ascii[(i + 1) % 16] = '\0';
				if ((i + 1) % 16 <= 8) {
					printf(" ");
				}
				for (j = (i + 1) % 16; j < 16; ++j) {
					printf("   ");
				}
				printf("|  %s \n", ascii);
			}
		}
	}
}

/**
 *  ==========================================================================
 *
 *  \brief  Read/Write len bytes from/to block dev
 *
 *  \param [in] fd      block dev file descriptor (returned from open)
 *  \param [in] rw      RW flag: 0 - read, != 0; - write
 *  \param [in] offset  block dev offset [bytes] - RW start position
 *  \param [in] buf     Pointer to the buffer containing the data
 *  \param [in] len     RW size in bytes. Buf must be at least that big
 *
 *  \return  0 on success
 *
 *  ==========================================================================
 */
static int blk_rw(int fd, int rw, uint64_t offset, uint8_t *buf, unsigned len)
{
	int r;

	if (lseek64(fd, offset, SEEK_SET) < 0) {
		fprintf(stderr, "block dev lseek64 %" PRIu64 " failed: %s\n", offset,
			strerror(errno));
		return -1;
	}

	if (rw)
		r = write(fd, buf, len);
	else
		r = read(fd, buf, len);

	if (r < 0) {
		fprintf(stderr, "block dev %s failed: %s\n", rw ? "write" : "read\n",
			strerror(errno));
	} else {
		if (rw) {
			r = fsync(fd);
			if (r < 0)
				fprintf(stderr, "fsync failed: %s\n", strerror(errno));
		} else {
			r = 0;
		}
	}

	return r;
}

/**
 *  ==========================================================================
 *
 *  \brief  Search within GPT for partition entry with the given name
 *  or it's backup twin (name-bak).
 *
 *  \param [in] ptn_name        Partition name to seek
 *  \param [in] pentries_start  Partition entries array start pointer
 *  \param [in] pentries_end    Partition entries array end pointer
 *  \param [in] pentry_size     Single partition entry size [bytes]
 *
 *  \return  First partition entry pointer that matches the name or null
 *
 *  ==========================================================================
 */
static uint8_t *gpt_pentry_seek(const char *ptn_name, const uint8_t *pentries_start,
				const uint8_t *pentries_end, uint32_t pentry_size)
{
	char *pentry_name;
	unsigned len = strlen(ptn_name);

	for (pentry_name = (char *)(pentries_start + PARTITION_NAME_OFFSET);
	     pentry_name < (char *)pentries_end; pentry_name += pentry_size) {
		char name8[MAX_GPT_NAME_SIZE / 2];
		unsigned i;

		/* Partition names in GPT are UTF-16 - ignoring UTF-16 2nd byte */
		for (i = 0; i < sizeof(name8); i++)
			name8[i] = pentry_name[i * 2];
		if (!strncmp(ptn_name, name8, len))
			if (name8[len] == 0 || !strcmp(&name8[len], BAK_PTN_NAME_EXT))
				return (uint8_t *)(pentry_name - PARTITION_NAME_OFFSET);
	}

	return NULL;
}

// Defined in ufs-bsg.cpp
int32_t set_boot_lun(uint8_t lun_id);

	// Swtich betwieen using either the primary or the backup
// boot LUN for boot. This is required since UFS boot partitions
// cannot have a backup GPT which is what we use for failsafe
// updates of the other 'critical' partitions. This function will
// not be invoked for emmc targets and on UFS targets is only required
// to be invoked for XBL.
//
// The algorithm to do this is as follows:
//- Find the real block device(eg: /dev/disk/sdb) that corresponds
//  to the /dev/disk/bootdevice/by-name/xbl(bak) symlink
//
//- Once we have the block device 'node' name(sdb in the above example)
//  use this node to to locate the scsi generic device that represents
//  it by checking the file /sys/block/sdb/device/scsi_generic/sgY
//
//- Once we locate sgY we call the query ioctl on /dev/sgy to switch
// the boot lun to either LUNA or LUNB
int gpt_utils_set_xbl_boot_partition(enum boot_chain chain)
{
	struct stat st;
	uint8_t boot_lun_id = 0;
	const char *boot_dev = NULL;

	(void)st;
	(void)boot_dev;

	if (chain == BACKUP_BOOT) {
		boot_lun_id = BOOT_LUN_B_ID;
		if (!stat(XBL_BACKUP, &st))
			boot_dev = XBL_BACKUP;
		else if (!stat(XBL_AB_SECONDARY, &st))
			boot_dev = XBL_AB_SECONDARY;
		else {
			fprintf(stderr, "%s: Failed to locate secondary xbl\n", __func__);
			goto error;
		}
	} else if (chain == NORMAL_BOOT) {
		boot_lun_id = BOOT_LUN_A_ID;
		if (!stat(XBL_PRIMARY, &st))
			boot_dev = XBL_PRIMARY;
		else if (!stat(XBL_AB_PRIMARY, &st))
			boot_dev = XBL_AB_PRIMARY;
		else {
			fprintf(stderr, "%s: Failed to locate primary xbl\n", __func__);
			goto error;
		}
	} else {
		fprintf(stderr, "%s: Invalid boot chain id\n", __func__);
		goto error;
	}
	// We need either both xbl and xblbak or both xbl_a and xbl_b to exist at
	// the same time. If not the current configuration is invalid.
	if ((stat(XBL_PRIMARY, &st) || stat(XBL_BACKUP, &st)) &&
	    (stat(XBL_AB_PRIMARY, &st) || stat(XBL_AB_SECONDARY, &st))) {
		fprintf(stderr, "%s:primary/secondary XBL prt not found(%s)\n", __func__,
			strerror(errno));
		goto error;
	}
	LOGD("%s: setting %s lun as boot lun\n", __func__, boot_dev);

	if (set_boot_lun(boot_lun_id)) {
		goto error;
	}
	return 0;
error:
	return -1;
}

// Given a parttion name(eg: rpm) get the path to the block device that
// represents the GPT disk the partition resides on. In the case of emmc it
// would be the default emmc dev(/dev/mmcblk0). In the case of UFS we look
// through the /dev/disk/bootdevice/by-name/ tree for partname, and resolve
// the path to the LUN from there.
static int get_dev_path_from_partition_name(const char *partname, char *buf, size_t buflen)
{
	char path[GPT_PTN_PATH_MAX] = { 0 };
	int i;

	if (!partname || !buf || buflen < ((PATH_TRUNCATE_LOC) + 1)) {
		fprintf(stderr, "%s: Invalid argument\n", __func__);
		return -1;
	}

	// Need to find the lun that holds partition partname
	snprintf(path, sizeof(path), "%s/%s", BOOT_DEV_DIR, partname);


	buf = realpath(path, buf);
	if (!buf) {
		return -1;
	} else {
		for (i = strlen(buf); i > 0; i--)
			if (!isdigit(buf[i - 1]))
				break;

		if (i >= 2 && buf[i - 1] == 'p' && isdigit(buf[i - 2]))
			i--;

		buf[i] = 0;
	}

	return 0;
}

// Get the block size of the disk represented by decsriptor fd
static uint32_t gpt_get_block_size(int fd)
{
	uint32_t block_size = 0;

	if (fd < 0) {
		fprintf(stderr, "%s: invalid descriptor\n", __func__);
		goto error;
	}

	if (ioctl(fd, BLKSSZGET, &block_size) != 0) {
		fprintf(stderr, "%s: Failed to get GPT dev block size : %s\n", __func__,
			strerror(errno));
		goto error;
	}

	return block_size;
error:
	return 0;
}

// Write the GPT header present in the passed in buffer back to the
// disk represented by fd
static int gpt_set_header(uint8_t *gpt_header, int fd, enum gpt_instance instance)
{
	uint32_t block_size = 0;
	off_t gpt_header_offset = 0;

	if (!gpt_header || fd < 0) {
		fprintf(stderr, "%s: Invalid arguments\n", __func__);
		goto error;
	}

	block_size = gpt_get_block_size(fd);
	LOGD("%s: Block size is : %d\n", __func__, block_size);
	if (block_size == 0) {
		fprintf(stderr, "%s: Failed to get block size\n", __func__);
		goto error;
	}

	if (instance == PRIMARY_GPT)
		gpt_header_offset = block_size;
	else
		gpt_header_offset = lseek64(fd, 0, SEEK_END) - block_size;
	if (gpt_header_offset <= 0) {
		fprintf(stderr, "%s: Failed to get gpt header offset\n", __func__);
		goto error;
	}

	LOGD("%s: Writing back header to offset %ld\n", __func__, gpt_header_offset);
	if (blk_rw(fd, 1, gpt_header_offset, gpt_header, block_size)) {
		fprintf(stderr, "%s: Failed to write back GPT header\n", __func__);
		goto error;
	}

	return 0;

error:
	return -1;
}

// Read out the GPT headers for the disk that contains the partition partname
static int gpt_get_headers(const char *partname, uint8_t **primary, uint8_t **backup)
{
	uint8_t *hdr = NULL;
	char devpath[GPT_PTN_PATH_MAX] = { 0 };
	off_t hdr_offset = 0;
	uint32_t block_size = 0;
	int instance;
	int fd = -1;

	if (!partname) {
		fprintf(stderr, "%s: Invalid partition name\n", __func__);
		goto error;
	}

	if (get_dev_path_from_partition_name(partname, devpath, sizeof(devpath)) != 0) {
		fprintf(stderr, "%s: Failed to resolve path for %s\n", __func__, partname);
		goto error;
	}

	fd = open(devpath, O_RDWR);
	if (fd < 0) {
		fprintf(stderr, "%s: Failed to open %s : %s\n", __func__, devpath, strerror(errno));
		return -1;
	}

	block_size = gpt_get_block_size(fd);
	if (block_size == 0) {
		fprintf(stderr, "%s: Failed to get gpt block size for %s\n", __func__, partname);
		goto error;
	}

	for (instance = PRIMARY_GPT; instance <= SECONDARY_GPT; instance++) {
		hdr = (uint8_t *)calloc(block_size, 1);
		if (!hdr) {
			fprintf(stderr, "%s: Failed to allocate memory for gpt header\n", __func__);
		}
		if (instance == PRIMARY_GPT)
			hdr_offset = block_size;
		else {
			hdr_offset = lseek64(fd, 0, SEEK_END) - block_size;
		}
		if (hdr_offset < 0) {
			fprintf(stderr, "%s: Failed to get gpt header offset\n", __func__);
			goto error;
		}
		if (blk_rw(fd, 0, hdr_offset, hdr, block_size)) {
			fprintf(stderr, "%s: Failed to read GPT header from device\n", __func__);
			goto error;
		}
		if (instance == PRIMARY_GPT)
			*primary = hdr;
		else
			*backup = hdr;
	}

	close(fd);
	return 0;

error:
	close(fd);
	if (hdr)
		free(hdr);
	return -1;
}

// Returns the partition entry array based on the
// passed in buffer which contains the gpt header.
// The fd here is the descriptor for the 'disk' which
// holds the partition
static uint8_t *gpt_get_pentry_arr(uint8_t *hdr, int fd)
{
	uint64_t pentries_start = 0;
	uint32_t pentry_size = 0;
	uint32_t block_size = 0;
	uint32_t pentries_arr_size = 0;
	uint8_t *pentry_arr = NULL;
	int rc = 0;
	if (!hdr) {
		fprintf(stderr, "%s: Invalid header\n", __func__);
		goto error;
	}
	if (fd < 0) {
		fprintf(stderr, "%s: Invalid fd\n", __func__);
		goto error;
	}
	block_size = gpt_get_block_size(fd);
	if (!block_size) {
		fprintf(stderr, "%s: Failed to get gpt block size for\n", __func__);
		goto error;
	}
	pentries_start = GET_8_BYTES(hdr + PENTRIES_OFFSET) * block_size;
	pentry_size = GET_4_BYTES(hdr + PENTRY_SIZE_OFFSET);
	pentries_arr_size = GET_4_BYTES(hdr + PARTITION_COUNT_OFFSET) * pentry_size;
	pentry_arr = (uint8_t *)calloc(1, pentries_arr_size);
	if (!pentry_arr) {
		fprintf(stderr, "%s: Failed to allocate memory for partition array\n", __func__);
		goto error;
	}
	rc = blk_rw(fd, 0, pentries_start, pentry_arr, pentries_arr_size);
	if (rc) {
		fprintf(stderr, "%s: Failed to read partition entry array\n", __func__);
		goto error;
	}
	return pentry_arr;
error:
	if (pentry_arr)
		free(pentry_arr);
	return NULL;
}

static int gpt_set_pentry_arr(uint8_t *hdr, int fd, uint8_t *arr)
{
	uint32_t block_size = 0;
	uint64_t pentries_start = 0;
	uint32_t pentry_size = 0;
	uint32_t pentries_arr_size = 0;
	int rc = 0;
	if (!hdr || fd < 0 || !arr) {
		fprintf(stderr, "%s: Invalid argument\n", __func__);
		goto error;
	}
	block_size = gpt_get_block_size(fd);
	if (!block_size) {
		fprintf(stderr, "%s: Failed to get gpt block size for\n", __func__);
		goto error;
	}
	LOGD("%s : Block size is %d\n", __func__, block_size);
	pentries_start = GET_8_BYTES(hdr + PENTRIES_OFFSET) * block_size;
	pentry_size = GET_4_BYTES(hdr + PENTRY_SIZE_OFFSET);
	pentries_arr_size = GET_4_BYTES(hdr + PARTITION_COUNT_OFFSET) * pentry_size;
	LOGD("%s: Writing partition entry array of size %d to offset %" PRIu64 "\n", __func__,
	     pentries_arr_size, pentries_start);
	LOGD("pentries_start: %lu\n", pentries_start);
	rc = blk_rw(fd, 1, pentries_start, arr, pentries_arr_size);
	if (rc) {
		fprintf(stderr, "%s: Failed to read partition entry array\n", __func__);
		goto error;
	}
	return 0;
error:
	return -1;
}

/*
 * Free previously allocated/initialized handle
 * This function is always safe and must be called
 * before discarding the handle.
 * it is called automatically by gpt_disk_get_disk_info()
 */
void gpt_disk_free(struct gpt_disk *disk)
{
	if (!disk)
		return;

	if (disk->hdr) {
		free(disk->hdr);
		disk->hdr = NULL;
	}
	if (disk->hdr_bak) {
		free(disk->hdr_bak);
		disk->hdr_bak = NULL;
	}
	if (disk->pentry_arr) {
		free(disk->pentry_arr);
		disk->pentry_arr = NULL;
	}
	if (disk->pentry_arr_bak) {
		free(disk->pentry_arr_bak);
		disk->pentry_arr_bak = NULL;
	}

	disk->is_initialized = 0;

	return;
}

bool gpt_disk_is_valid(struct gpt_disk *disk)
{
	return disk->is_initialized == GPT_DISK_INIT_MAGIC;
}

/*
 * Check if a partition by-path is for the disk we have info for
 * and populate the blockdev path.
 * e.g. for /dev/disk/by-partlabel/system_a blockdev would be /dev/sda
 */
int partition_is_for_disk(const struct gpt_disk *disk, const char *part, char *blockdev, int blockdev_len)
{
	int ret;

	ret = get_dev_path_from_partition_name(part, blockdev, blockdev_len);
	if (ret) {
		fprintf(stderr, "%s: Failed to resolve path for %s\n", __func__, part);
		return -1;
	}

	if (!strcmp(blockdev, disk->devpath)) {
		return true;
	}

	return false;
}

/*
 * fills up the passed in gpt_disk struct with information about the
 * disk represented by path dev. Returns 0 on success and -1 on error.
 */
int gpt_disk_get_disk_info(const char *dev, struct gpt_disk *disk)
{
	int fd = -1, rc;
	uint32_t gpt_header_size = 0;
	char devpath[GPT_PTN_PATH_MAX] = { 0 };

	if (!disk || !dev) {
		fprintf(stderr, "%s: Invalid arguments\n", __func__);
		goto error;
	}

	rc = partition_is_for_disk(disk, dev, devpath, sizeof(devpath));

	if (rc > 0)
		return 0;

	if (rc < 0) {
		fprintf(stderr, "%s: Failed to resolve path for %s\n", __func__, dev);
		return -1;
	}

	if (disk->is_initialized == GPT_DISK_INIT_MAGIC) {
		// We already have a valid disk handle. Free it.
		LOGD("%s: Freeing disk handle for %s... -> %s\n", __func__, disk->devpath, devpath);
		gpt_disk_free(disk);
	}

	LOGD("%s: Initializing disk handle for %s... -> %s\n", __func__, disk->devpath, devpath);

	// devpath popualted by partition_is_for_disk
	strncpy(disk->devpath, devpath, sizeof(disk->devpath));

	if (gpt_get_headers(dev, &disk->hdr, &disk->hdr_bak)) {
		fprintf(stderr, "%s: Failed to get GPT headers\n", __func__);
		goto error;
	}

	assert(disk->hdr != NULL);
	assert(disk->hdr_bak != NULL);

	gpt_header_size = GET_4_BYTES(disk->hdr + HEADER_SIZE_OFFSET);

	// FIXME: pointer offsets crc bleh
	disk->hdr_crc = efi_crc32(disk->hdr, gpt_header_size);

	disk->hdr_bak_crc = efi_crc32(disk->hdr_bak, gpt_header_size);

	fd = open(disk->devpath, O_RDWR);
	if (fd < 0) {
		fprintf(stderr, "%s: Failed to open %s: %s\n", __func__, disk->devpath,
			strerror(errno));
		goto error;
	}

	assert(disk->pentry_arr == NULL);
	disk->pentry_arr = gpt_get_pentry_arr(disk->hdr, fd);
	if (!disk->pentry_arr) {
		fprintf(stderr, "%s: Failed to obtain partition entry array\n", __func__);
		goto error;
	}

	assert(disk->pentry_arr_bak == NULL);
	disk->pentry_arr_bak = gpt_get_pentry_arr(disk->hdr_bak, fd);
	if (!disk->pentry_arr_bak) {
		fprintf(stderr, "%s: Failed to obtain backup partition entry array\n", __func__);
		goto error;
	}

	disk->pentry_size = GET_4_BYTES(disk->hdr + PENTRY_SIZE_OFFSET);
	disk->pentry_arr_size = GET_4_BYTES(disk->hdr + PARTITION_COUNT_OFFSET) * disk->pentry_size;
	disk->pentry_arr_crc = GET_4_BYTES(disk->hdr + PARTITION_CRC_OFFSET);
	disk->pentry_arr_bak_crc = GET_4_BYTES(disk->hdr_bak + PARTITION_CRC_OFFSET);
	disk->block_size = gpt_get_block_size(fd);
	close(fd);
	disk->is_initialized = GPT_DISK_INIT_MAGIC;
	return 0;
error:
	if (fd >= 0)
		close(fd);
	return -1;
}

// Get pointer to partition entry from a allocated gpt_disk structure
uint8_t *gpt_disk_get_pentry(struct gpt_disk *disk, const char *partname, enum gpt_instance instance)
{
	uint8_t *ptn_arr = NULL;
	if (!disk || !partname || disk->is_initialized != GPT_DISK_INIT_MAGIC) {
		fprintf(stderr, "%s: disk handle not initialised\n", __func__);
		return NULL;
	}
	ptn_arr = (instance == PRIMARY_GPT) ? disk->pentry_arr : disk->pentry_arr_bak;
	return (gpt_pentry_seek(partname, ptn_arr, ptn_arr + disk->pentry_arr_size,
				disk->pentry_size));
}

// Update CRC values for the various components of the gpt_disk
// structure. This function should be called after any of the fields
// have been updated before the structure contents are written back to
// disk.
static int gpt_disk_update_crc(struct gpt_disk *disk)
{
	uint32_t gpt_header_size = 0;
	if (!disk || (disk->is_initialized != GPT_DISK_INIT_MAGIC)) {
		fprintf(stderr, "%s: disk not initialised!\n", __func__);
		return -1;
	}

#ifdef DEBUG
	uint32_t old_crc = disk->pentry_arr_crc;
#endif
	// Recalculate the CRC of the primary partiton array
	disk->pentry_arr_crc = efi_crc32(disk->pentry_arr, disk->pentry_arr_size);
	LOGD("%s() disk %8s GPT pentry len %u crc: %08x -> %08x\n", __func__, disk->devpath,
	     disk->pentry_arr_size, old_crc, disk->pentry_arr_crc);

	// DumpHex(disk->pentry_arr, disk->pentry_arr_size);

	// Recalculate the CRC of the backup partition array
	disk->pentry_arr_bak_crc = efi_crc32(disk->pentry_arr_bak, disk->pentry_arr_size);
	LOGD("%s() disk %8s GPT pentry_bak len %u crc: %08x -> %08x\n", __func__, disk->devpath,
	     disk->pentry_arr_size, old_crc, disk->pentry_arr_crc);

	// Update the partition CRC value in the primary GPT header
	PUT_4_BYTES(disk->hdr + PARTITION_CRC_OFFSET, disk->pentry_arr_crc);

	// Update the partition CRC value in the backup GPT header
	PUT_4_BYTES(disk->hdr_bak + PARTITION_CRC_OFFSET, disk->pentry_arr_bak_crc);

	// Update the CRC value of the primary header
	gpt_header_size = GET_4_BYTES(disk->hdr + HEADER_SIZE_OFFSET);

	// Header CRC is calculated with its own CRC field set to 0
	PUT_4_BYTES(disk->hdr + HEADER_CRC_OFFSET, 0);
	PUT_4_BYTES(disk->hdr_bak + HEADER_CRC_OFFSET, 0);
	disk->hdr_crc = efi_crc32(disk->hdr, gpt_header_size);
	disk->hdr_bak_crc = efi_crc32(disk->hdr_bak, gpt_header_size);
	PUT_4_BYTES(disk->hdr + HEADER_CRC_OFFSET, disk->hdr_crc);
	PUT_4_BYTES(disk->hdr_bak + HEADER_CRC_OFFSET, disk->hdr_bak_crc);
	return 0;
}

// Write the contents of struct gpt_disk back to the actual disk
int gpt_disk_commit(struct gpt_disk *disk)
{
	int fd = -1;

	if (!disk || (disk->is_initialized != GPT_DISK_INIT_MAGIC)) {
		fprintf(stderr, "%s: Invalid args\n", __func__);
		goto error;
	}

	if (gpt_disk_update_crc(disk)) {
		fprintf(stderr, "%s: Failed to update CRC values\n", __func__);
		goto error;
	}

	fd = open(disk->devpath, O_RDWR);
	if (fd < 0) {
		fprintf(stderr, "%s: Failed to open %s: %s\n", __func__, disk->devpath,
			strerror(errno));
		goto error;
	}

	LOGD("%s: Writing back primary GPT header\n", __func__);

	// Write the primary header
	if (gpt_set_header(disk->hdr, fd, PRIMARY_GPT) != 0) {
		fprintf(stderr, "%s: Failed to update primary GPT header\n", __func__);
		goto error;
	}
	LOGD("%s: Writing back primary partition array\n", __func__);

	// Write back the primary partition array
	if (gpt_set_pentry_arr(disk->hdr, fd, disk->pentry_arr)) {
		fprintf(stderr, "%s: Failed to write primary GPT partition arr\n", __func__);
		goto error;
	}

	// Write the backup header
	if (gpt_set_header(disk->hdr_bak, fd, SECONDARY_GPT) != 0) {
		fprintf(stderr, "%s: Failed to update backup GPT header\n", __func__);
		goto error;
	}
	LOGD("%s: Writing back backup partition array\n", __func__);

	// Write back the backup partition array
	if (gpt_set_pentry_arr(disk->hdr_bak, fd, disk->pentry_arr_bak)) {
		fprintf(stderr, "%s: Failed to write backup GPT partition arr\n", __func__);
		goto error;
	}

	LOGD("%s: Done\n", __func__);

	fsync(fd);
	close(fd);
	return 0;

error:
	if (fd >= 0)
		close(fd);
	return -1;
}

// Determine whether to handle the given partition as eMMC or UFS, using the
// name of the backing device.
//
// Note: In undefined cases (i.e. /dev/mmcblk1 and unresolvable), this function
// will tend to prefer UFS behavior. If it incorrectly reports this, then the
// program should exit (e.g. by failing) before making any changes.
bool gpt_utils_is_partition_backed_by_emmc(const char *part)
{
	char devpath[GPT_PTN_PATH_MAX] = { '\0' };

	if (get_dev_path_from_partition_name(part, devpath, sizeof(devpath)))
		return false;

	return !strcmp(devpath, EMMC_DEVICE);
}