Re: [PATCH v2 2/2] gpt: create empty disklabels

[Petr Uzel <petr.uzel@suse.cz>]

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On Sat, Oct 27, 2012 at 07:23:47PM +0200, Davidlohr Bueso wrote:
> This patch enables creating a new, empty, GPT disklabel from either
> an empty disk or one that already has a disklabel. For this
> purpose, a 'g' option is added to the main menu and is visible to all
> labels. Here's an example for a scsi_debug device (/dev/sdb):
> 
> ...
> Device does not contain a recognized partition table
> Building a new DOS disklabel with disk identifier 0x20a614c8.
> 3696: fdisk:  CONTEXT: zeroize in-memory first sector buffer
> 
> Command (m for help): g
> 3696: fdisk:    LABEL: changing to gpt label
> 
> 3696: fdisk:  CONTEXT: zeroize in-memory first sector buffer
> 3696: fdisk:    LABEL: created new empty GPT disklabel (GUID: D4EA0706-F011-46DC-B7DE-6A72C7090AF8)
> 
> Command (m for help): w
> The partition table has been altered!
> ...
> 
> Signed-off-by: Davidlohr Bueso <dave@gnu.org>

Looks good to me and it also survived my testing.

Reviewed-and-tested-by: Petr Uzel <petr.uzel@suse.cz>


> ---
>  fdisks/fdisk.c |    4 ++
>  fdisks/gpt.c   |  202 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 200 insertions(+), 6 deletions(-)
> 
> diff --git a/fdisks/fdisk.c b/fdisks/fdisk.c
> index e271ea1..a3ac087 100644
> --- a/fdisks/fdisk.c
> +++ b/fdisks/fdisk.c
> @@ -90,6 +90,7 @@ static const struct menulist_descr menulist[] = {
>  	{'e', N_("edit drive data"), {OSF_LABEL, 0}},
>  	{'f', N_("fix partition order"), {0, DOS_LABEL}},
>  	{'g', N_("create an IRIX (SGI) partition table"), {0, ANY_LABEL}},
> +	{'g', N_("create a new empty GPT partition table"), {ANY_LABEL, 0}},
>  	{'h', N_("change number of heads"), {0, DOS_LABEL | SUN_LABEL}},
>  	{'i', N_("change interleave factor"), {0, SUN_LABEL}},
>  	{'i', N_("change the disk identifier"), {0, DOS_LABEL}},
> @@ -1694,6 +1695,9 @@ static void command_prompt(struct fdisk_context *cxt)
>  		case 'd':
>  			delete_partition(cxt, get_existing_partition(cxt, 1, partitions));
>  			break;
> +		case 'g':
> +			fdisk_create_disklabel(cxt, "gpt");
> +			break;
>  		case 'i':
>  			if (disklabel == SGI_LABEL)
>  				create_sgiinfo(cxt);
> diff --git a/fdisks/gpt.c b/fdisks/gpt.c
> index 48397f3..843dc44 100644
> --- a/fdisks/gpt.c
> +++ b/fdisks/gpt.c
> @@ -19,7 +19,6 @@
>   * 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
> - *
>   */
>  
>  #include <stdio.h>
> @@ -59,7 +58,8 @@
>  
>  #define EFI_PMBR_OSTYPE     0xEE
>  #define MSDOS_MBR_SIGNATURE 0xAA55
> -#define GPT_PART_NAME_LEN 72 / sizeof(uint16_t)
> +#define GPT_PART_NAME_LEN   72 / sizeof(uint16_t)
> +#define GPT_NPARTITIONS     128
>  
>  /* Globally unique identifier */
>  struct gpt_guid {
> @@ -96,8 +96,8 @@ struct gpt_attr {
>  
>  /* The GPT Partition entry array contains an array of GPT entries. */
>  struct gpt_entry {
> -	struct gpt_guid   partition_type_guid; /* purpose and type of the partition */
> -	struct gpt_guid   unique_partition_guid;
> +	struct gpt_guid     partition_type_guid; /* purpose and type of the partition */
> +	struct gpt_guid     unique_partition_guid;
>  	uint64_t            lba_start;
>  	uint64_t            lba_end;
>  	struct gpt_attr     attr;
> @@ -115,7 +115,7 @@ struct gpt_header {
>  	uint64_t            alternative_lba; /* backup GPT header */
>  	uint64_t            first_usable_lba; /* first usable logical block for partitions */
>  	uint64_t            last_usable_lba; /* last usable logical block for partitions */
> -	struct gpt_guid   disk_guid; /* unique disk identifier */
> +	struct gpt_guid     disk_guid; /* unique disk identifier */
>  	uint64_t            partition_entry_lba; /* stat LBA of the partition entry array */
>  	uint32_t            npartition_entries; /* total partition entries - normally 128 */
>  	uint32_t            sizeof_partition_entry; /* bytes for each GUID pt */
> @@ -298,6 +298,125 @@ static inline int partition_unused(struct gpt_entry e)
>  }
>  
>  /*
> + * Builds a clean new valid protective MBR - will wipe out any existing data.
> + * Returns 0 on success, otherwise < 0 on error.
> + */
> +static int gpt_mknew_pmbr(struct fdisk_context *cxt)
> +{
> +	struct gpt_legacy_mbr *pmbr = NULL;
> +
> +	if (!cxt || !cxt->firstsector)
> +		return -ENOSYS;
> +
> +	fdisk_zeroize_firstsector(cxt);
> +
> +	pmbr = (struct gpt_legacy_mbr *) cxt->firstsector;
> +
> +	pmbr->signature = cpu_to_le16(MSDOS_MBR_SIGNATURE);
> +	pmbr->partition_record[0].os_type      = EFI_PMBR_OSTYPE;
> +	pmbr->partition_record[0].start_sector = 1;
> +	pmbr->partition_record[0].end_head     = 0xFE;
> +	pmbr->partition_record[0].end_sector   = 0xFF;
> +	pmbr->partition_record[0].end_track    = 0xFF;
> +	pmbr->partition_record[0].starting_lba = cpu_to_le32(1);
> +	pmbr->partition_record[0].size_in_lba  =
> +		cpu_to_le32(min((uint32_t) cxt->total_sectors - 1, 0xFFFFFFFF));
> +
> +	return 0;
> +}
> +
> +/* some universal differences between the headers */
> +static void gpt_mknew_header_common(struct fdisk_context *cxt,
> +				    struct gpt_header *header, uint64_t lba)
> +{
> +	if (!cxt || !header)
> +		return;
> +
> +	header->my_lba = cpu_to_le64(lba);
> +
> +	if (lba == GPT_PRIMARY_PARTITION_TABLE_LBA) { /* primary */
> +		header->alternative_lba = cpu_to_le64(cxt->total_sectors - 1);
> +		header->partition_entry_lba = cpu_to_le64(2);
> +	} else { /* backup */
> +		uint64_t esz = le32_to_cpu(header->npartition_entries) * sizeof(struct gpt_entry);
> +		uint64_t esects = (esz + cxt->sector_size - 1) / cxt->sector_size;
> +
> +		header->alternative_lba = cpu_to_le64(GPT_PRIMARY_PARTITION_TABLE_LBA);
> +		header->partition_entry_lba = cpu_to_le64(cxt->total_sectors - 1 - esects);
> +       	}
> +}
> +
> +/*
> + * Builds a new GPT header (at sector lba) from a backup header2.
> + * If building a primary header, then backup is the secondary, and vice versa.
> + *
> + * Always pass a new (zeroized) header to build upon as we don't
> + * explicitly zero-set some values such as CRCs and reserved.
> + *
> + * Returns 0 on success, otherwise < 0 on error.
> + */
> +static int gpt_mknew_header_from_bkp(struct fdisk_context *cxt,
> +				     struct gpt_header *header,
> +				     uint64_t lba,
> +				     struct gpt_header *header2)
> +{
> +	if (!cxt || !header || !header2)
> +		return -ENOSYS;
> +
> +	header->signature              = header2->signature;
> +	header->revision               = header2->revision;
> +	header->size                   = header2->size;
> +	header->npartition_entries     = header2->npartition_entries;
> +	header->sizeof_partition_entry = header2->sizeof_partition_entry;
> +	header->first_usable_lba       = header2->first_usable_lba;
> +	header->last_usable_lba        = header2->last_usable_lba;
> +
> +	memcpy(&header->disk_guid,
> +	       &header2->disk_guid, sizeof(header2->disk_guid));
> +	gpt_mknew_header_common(cxt, header, lba);
> +
> +	return 0;
> +}
> +
> +/*
> + * Builds a clean new GPT header (currently under revision 1.0).
> + *
> + * Always pass a new (zeroized) header to build upon as we don't
> + * explicitly zero-set some values such as CRCs and reserved.
> + *
> + * Returns 0 on success, otherwise < 0 on error.
> + */
> +static int gpt_mknew_header(struct fdisk_context *cxt,
> +			    struct gpt_header *header, uint64_t lba)
> +{
> +	uint64_t esz = 0;
> +
> +	if (!cxt || !header)
> +		return -ENOSYS;
> +
> +	esz = sizeof(struct gpt_entry) * GPT_NPARTITIONS / cxt->sector_size;
> +
> +	header->signature = cpu_to_le64(GPT_HEADER_SIGNATURE);
> +	header->revision  = cpu_to_le32(GPT_HEADER_REVISION_V1_00);
> +	header->size      = cpu_to_le32(sizeof(struct gpt_header));
> +
> +	/*
> +	 * 128 partitions is the default. It can go behond this, however,
> +	 * we're creating a de facto header here, so no funny business.
> +	 */
> +	header->npartition_entries     = cpu_to_le32(GPT_NPARTITIONS);
> +	header->sizeof_partition_entry = cpu_to_le32(sizeof(struct gpt_entry));
> +	header->first_usable_lba       = cpu_to_le64(esz + 2);
> +	header->last_usable_lba        = cpu_to_le64(cxt->total_sectors - 2 - esz);
> +
> +	gpt_mknew_header_common(cxt, header, lba);
> +	uuid_generate_random((unsigned char *) &header->disk_guid);
> +	swap_efi_guid(&header->disk_guid);
> +
> +	return 0;
> +}
> +
> +/*
>   * Checks if there is a valid protective MBR partition table.
>   * Returns 0 if it is invalid or failure. Otherwise, return
>   * GPT_MBR_PROTECTIVE or GPT_MBR_HYBRID, depeding on the detection.
> @@ -850,6 +969,22 @@ static void gpt_init(void)
>  	partitions = le32_to_cpu(pheader->npartition_entries);
>  }
>  
> +/*
> + * Deinitialize fdisk-specific variables
> + */
> +static void gpt_deinit(void)
> +{
> +	free(ents);
> +	free(pheader);
> +	free(bheader);
> +	ents = NULL;
> +	pheader = NULL;
> +	bheader = NULL;
> +
> +	disklabel = ANY_LABEL;
> +	partitions = 0;
> +}
> +
>  static int gpt_probe_label(struct fdisk_context *cxt)
>  {
>  	int mbr_type;
> @@ -899,6 +1034,7 @@ static char *encode_to_utf8(unsigned char *src, size_t count)
>  	uint16_t c;
>  	char *dest = xmalloc(count * sizeof(char));
>  	size_t i, j, len = count;
> +
>  	memset(dest, 0, sizeof(char) * count);
>  
>  	for (j = i = 0; i + 2 <= count; i += 2) {
> @@ -1363,6 +1499,60 @@ static void gpt_add_partition(struct fdisk_context *cxt, int partnum,
>  		printf(_("Created partition %d\n"), partnum + 1);
>  }
>  
> +/*
> + * Create a new GPT disklabel - destroys any previous data.
> + */
> +static int gpt_create_disklabel(struct fdisk_context *cxt)
> +{
> +	int rc = 0;
> +	ssize_t entry_sz = 0;
> +
> +	/*
> +	 * Reset space or clear data from headers, pt entries and
> +	 * protective MBR. Big fat warning: any previous content is
> +	 * overwritten, so ask users to be sure!.
> +	 *
> +	 * When no header, entries or pmbr is set, we're probably
> +	 * dealing with a new, empty disk - so always allocate memory
> +	 * to deal with the data structures whatever the case is.
> +	 */
> +	gpt_deinit();
> +
> +	rc = gpt_mknew_pmbr(cxt);
> +	if (rc < 0)
> +		goto done;
> +
> +	pheader = xcalloc(1, sizeof(*pheader));
> +       	rc = gpt_mknew_header(cxt, pheader, GPT_PRIMARY_PARTITION_TABLE_LBA);
> +	if (rc < 0)
> +		goto done;
> +
> +	bheader = xcalloc(1, sizeof(*bheader));
> +	rc = gpt_mknew_header_from_bkp(cxt, bheader, last_lba(cxt), pheader);
> +	if (rc < 0)
> +		goto done;
> +
> +	entry_sz = le32_to_cpu(pheader->npartition_entries) *
> +		le32_to_cpu(pheader->sizeof_partition_entry);
> +	ents = xcalloc(1, sizeof(*ents) * entry_sz);
> +
> +	gpt_recompute_crc(pheader, ents);
> +	gpt_recompute_crc(bheader, ents);
> +
> +	gpt_init();
> +	DBG(LABEL, dbgprint("created new empty GPT disklabel "
> +			    "(GUID: %08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X)",
> +			    pheader->disk_guid.time_low, pheader->disk_guid.time_mid,
> +			    pheader->disk_guid.time_hi_and_version,
> +			    pheader->disk_guid.clock_seq_hi,
> +			    pheader->disk_guid.clock_seq_low,
> +			    pheader->disk_guid.node[0], pheader->disk_guid.node[1],
> +			    pheader->disk_guid.node[2], pheader->disk_guid.node[3],
> +			    pheader->disk_guid.node[4], pheader->disk_guid.node[5]));
> +done:
> +	return rc;
> +}
> +
>  static struct fdisk_parttype *gpt_get_partition_type(struct fdisk_context *cxt,
>  						     int i)
>  {
> @@ -1409,7 +1599,7 @@ const struct fdisk_label gpt_label =
>  	.probe = gpt_probe_label,
>  	.write = gpt_write_disklabel,
>  	.verify = gpt_verify_disklabel,
> -	.create = NULL,
> +	.create = gpt_create_disklabel,
>  	.part_add = gpt_add_partition,
>  	.part_delete = gpt_delete_partition,
>  	.part_get_type = gpt_get_partition_type,
> -- 
> 1.7.9.5
> 
> 
> 
> 
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Petr

-- 
Petr Uzel
IRC: ptr_uzl @ freenode

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