EFI_ALLOC_AND_INIT(3EXT) Extended Library Functions EFI_ALLOC_AND_INIT(3EXT)

efi_alloc_and_init, efi_alloc_and_read, efi_free, efi_write, efi_use_whole_disk, efi_reserved_sectors - manipulate a disk's EFI Partition Table

cc [ flag ... ] file... -lefi [ library ... ]
#include <sys/vtoc.h>
#include <sys/efi_partition.h>
int efi_alloc_and_init(int fd, uint32_t nparts, dk_gpt_t **vtoc);

int efi_alloc_and_read(int fd, dk_gpt_t **vtoc);

void efi_free(dk_gpt_t *vtoc);

int efi_write(int fd, dk_gpt_t *vtoc);

int efi_use_whole_disk(int fd);

uint_t efi_reserved_sectors(dk_gpt_t *vtoc);

The efi_alloc_and_init() function initializes the dk_gpt_t structure specified by vtoc in preparation for a call to efi_write(). It calculates and initializes the efi_version, efi_lbasize, efi_nparts, efi_first_u_lba, efi_last_lba, and efi_last_u_lba members of this structure. The caller can then set the efi_nparts member.

The efi_alloc_and_read() function allocates memory and returns the partition table.

The efi_free() function frees the memory allocated by efi_alloc_and_init() and efi_alloc_and_read().

The efi_write() function writes the EFI partition table and creates a Protective Master Boot Record (PMBR); see below.

The efi_use_whole_disk() function takes any space that is not contained in the disk label and adds it to the last physically non-zero area before the reserved slice (from slice 0 to slice 6 or unallocated space).

The efi_reserved_sectors() function calculates number of sectors needed to create the reserved partition. The reserved partition is used by the operating system for internal purposes. The sector size used is based on the device and is recorded in the efi_lbasize member of the dkgpt_t structure indicated by the vtoc argument. A full description of the dk_gpt_t structure appears later in the manual.

The fd argument refers to any slice on a raw disk, opened with O_NDELAY. See open(2).

The nparts argument specifies the number of desired partitions.

The vtoc argument is a dk_gpt_t structure that describes an EFI partition table and contains at least the following members:


uint_t          efi_version;     /* set to EFI_VERSION_CURRENT */
uint_t          efi_nparts;      /* no. of partitions in efi_parts */
uint_t          efi_lbasize;     /* size of block in bytes */
diskaddr_t      efi_last_lba;    /* last block on the disk */
diskaddr_t      efi_first_u_lba; /* first block after labels */
diskaddr_t      efi_last_u_lba;  /* last block before backup labels */
struct dk_part  efi_parts[];     /* array of partitions */

When a disk receives an EFI label, a protective MBR (PMBR) is also written containing a single partition of type EEh and spanning the entire disk (up to the limit of what can be represented in an MBR). By default that partition is placed in slot 0 of the PMBR and not marked as active. Some BIOS implementations contain bugs that require the entry to be placed into a different slot or to be made active in order for the system to boot successfully. The default behaviour is modified for systems with known firmware bugs, refer to /usr/share/hwdata/efi.fixes for more information.

Upon successful completion, efi_alloc_and_init() returns 0. Otherwise it returns VT_EIO if an I/O operation to the disk fails.

Upon successful completion, efi_alloc_and_read() returns a positive integer indicating the slice index associated with the open file descriptor. Otherwise, it returns a negative integer to indicate one of the following:

VT_EIO

An I/O error occurred.

VT_ERROR

An unknown error occurred.

VT_EINVAL

An EFI label was not found.

The efi_reserved_sectors() function always returns the number of reserved sectors required. It will always succeed.

Upon successful completion, efi_write() returns 0. Otherwise, it returns a negative integer to indicate one of the following:

VT_EIO

An I/O error occurred.

VT_ERROR

An unknown error occurred.

VT_EINVAL

The label contains incorrect data.

Upon successfully completion, efi_use_whole_disk() returns 0. Otherwise, it returns a negative integer to indicate one of the following:

VT_EIO

An I/O error occurred.

VT_ERROR

An unknown error occurred.

VT_EINVAL

The label contains incorrect data.

VT_ENOSPC

Space out of label was not found.

The EFI label is used on disks with more than 1^32-1 blocks. For compatibility reasons, the read_vtoc(3EXT) and write_vtoc() functions should be used on smaller disks. The application should attempt the read_vtoc() or write_vtoc() call, check for an error of VT_ENOTSUP, then call the analogous EFI function.

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Committed
MT-Level Unsafe

fmthard(1M), format(1M), prtvtoc(1M), ioctl(2), open(2), libefi(3LIB), read_vtoc(3EXT), attributes(5), dkio(7I)
May 16, 2020 OmniOS