/*
* EFI GPT partition parsing code
*
* Copyright (C) 2009 Karel Zak <kzak@redhat.com>
*
* This file may be redistributed under the terms of the
* GNU Lesser General Public License.
*
* This code is not copy & past from any other implementation.
*
* For more information about GPT start your study at:
* http://en.wikipedia.org/wiki/GUID_Partition_Table
* http://technet.microsoft.com/en-us/library/cc739412(WS.10).aspx
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include "partitions.h"
#include "crc32.h"
#include "dos.h"
#define GPT_PRIMARY_LBA 1
/* Signature - “EFI PART” */
#define GPT_HEADER_SIGNATURE 0x5452415020494645ULL
#define GPT_HEADER_SIGNATURE_STR "EFI PART"
/* basic types */
typedef uint16_t efi_char16_t;
/* UUID */
typedef struct {
uint32_t time_low;
uint16_t time_mid;
uint16_t time_hi_and_version;
uint8_t clock_seq_hi;
uint8_t clock_seq_low;
uint8_t node[6];
} efi_guid_t;
#define GPT_UNUSED_ENTRY_GUID \
((efi_guid_t) { 0x00000000, 0x0000, 0x0000, 0x00, 0x00, \
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }})
struct gpt_header {
uint64_t signature; /* "EFI PART" */
uint32_t revision;
uint32_t header_size; /* usually 92 bytes */
uint32_t header_crc32; /* checksum of header with this
* field zeroed during calculation */
uint32_t reserved1;
uint64_t my_lba; /* location of this header copy */
uint64_t alternate_lba; /* location of the other header copy */
uint64_t first_usable_lba; /* lirst usable LBA for partitions */
uint64_t last_usable_lba; /* last usable LBA for partitions */
efi_guid_t disk_guid; /* disk UUID */
uint64_t partition_entries_lba; /* always 2 in primary header copy */
uint32_t num_partition_entries;
uint32_t sizeof_partition_entry;
uint32_t partition_entry_array_crc32;
/*
* The rest of the block is reserved by UEFI and must be zero. EFI
* standard handles this by:
*
* uint8_t reserved2[ BLKSSZGET - 92 ];
*
* This definition is useless in practice. It is necessary to read
* whole block from the device rather than sizeof(struct gpt_header)
* only.
*/
} __attribute__ ((packed));
/*** not used
struct gpt_entry_attributes {
uint64_t required_to_function:1;
uint64_t reserved:47;
uint64_t type_guid_specific:16;
} __attribute__ ((packed));
***/
struct gpt_entry {
efi_guid_t partition_type_guid; /* type UUID */
efi_guid_t unique_partition_guid; /* partition UUID */
uint64_t starting_lba;
uint64_t ending_lba;
/*struct gpt_entry_attributes attributes;*/
uint64_t attributes;
efi_char16_t partition_name[72 / sizeof(efi_char16_t)]; /* UTF-16LE string*/
} __attribute__ ((packed));
/*
* EFI uses crc32 with ~0 seed and xor's with ~0 at the end.
*/
static inline uint32_t count_crc32(const unsigned char *buf, size_t len)
{
return (crc32(~0L, buf, len) ^ ~0L);
}
static inline unsigned char *get_lba_buffer(blkid_probe pr,
uint64_t lba, size_t bytes)
{
return blkid_probe_get_buffer(pr,
blkid_probe_get_sectorsize(pr) * lba, bytes);
}
static inline int guidcmp(efi_guid_t left, efi_guid_t right)
{
return memcmp(&left, &right, sizeof (efi_guid_t));
}
/*
* UUID is traditionally 16 byte big-endian array, except Intel EFI
* specification where the UUID is a structure of little-endian fields.
*/
static void swap_efi_guid(efi_guid_t *uid)
{
uid->time_low = swab32(uid->time_low);
uid->time_mid = swab16(uid->time_mid);
uid->time_hi_and_version = swab16(uid->time_hi_and_version);
}
static int last_lba(blkid_probe pr, uint64_t *lba)
{
blkid_loff_t sz = blkid_probe_get_size(pr);
unsigned int ssz = blkid_probe_get_sectorsize(pr);
if (sz < ssz)
return -1;
*lba = (sz / ssz) - 1ULL;
return 0;
}
/*
* Protective (legacy) MBR.
*
* This MBR contains standard DOS partition table with a single partition, type
* of 0xEE. The partition usually encompassing the entire GPT drive - or 2TiB
* for large disks.
*
* Note that Apple uses GPT/MBR hybrid disks, where the DOS partition table is
* synchronized with GPT. This synchronization has many restriction of course
* (due DOS PT limitations).
*
* Note that the PMBR detection is optional (enabled by default) and could be
* disabled by BLKID_PARTS_FOPCE_GPT flag (see also blkid_paertitions_set_flags()).
*/
static int is_pmbr_valid(blkid_probe pr)
{
int flags = blkid_partitions_get_flags(pr);
unsigned char *data;
struct dos_partition *p;
int i;
if (flags & BLKID_PARTS_FORCE_GPT)
goto ok; /* skip PMBR check */
data = blkid_probe_get_sector(pr, 0);
if (!data)
goto failed;
if (!is_valid_mbr_signature(data))
goto failed;
p = (struct dos_partition *) (data + BLKID_MSDOS_PT_OFFSET);
for (i = 0; i < 4; i++, p++) {
if (p->sys_type == BLKID_GPT_PARTITION)
goto ok;
}
failed:
return 0;
ok:
return 1;
}
/*
* Reads GPT header to @hdr and returns a pointer to @hdr or NULL in case of
* error. The function also returns GPT entries in @ents.
*
* Note, this function does not allocate any memory. The GPT header has fixed
* size so we use stack, and @ents returns memory from libblkid buffer (so the
* next blkid_probe_get_buffer() will overwrite this buffer).
*
* This function checks validity of header and entries array. A corrupted
* header is not returned.
*/
static struct gpt_header *get_gpt_header(
blkid_probe pr, struct gpt_header *hdr,
struct gpt_entry **ents, uint64_t lba,
uint64_t lastlba)
{
struct gpt_header *h;
uint32_t crc, orgcrc;
uint64_t lu, fu;
size_t esz;
uint32_t hsz, ssz;
ssz = blkid_probe_get_sectorsize(pr);
/* whole sector is allocated for GPT header */
h = (struct gpt_header *) get_lba_buffer(pr, lba, ssz);
if (!h)
return NULL;
if (le64_to_cpu(h->signature) != GPT_HEADER_SIGNATURE)
return NULL;
hsz = le32_to_cpu(h->header_size);
/* EFI: The HeaderSize must be greater than 92 and must be less
* than or equal to the logical block size.
*/
if (hsz > ssz || hsz < sizeof(*h))
return NULL;
/* Header has to be verified when header_crc32 is zero */
orgcrc = h->header_crc32;
h->header_crc32 = 0;
crc = count_crc32((unsigned char *) h, hsz);
h->header_crc32 = orgcrc;
if (crc != le32_to_cpu(orgcrc)) {
DBG(DEBUG_LOWPROBE, printf("GPT header corrupted\n"));
return NULL;
}
/* Valid header has to be at MyLBA */
if (le64_to_cpu(h->my_lba) != lba) {
DBG(DEBUG_LOWPROBE, printf(
"GPT->MyLBA mismatch with real position\n"));
return NULL;
}
fu = le64_to_cpu(h->first_usable_lba);
lu = le64_to_cpu(h->last_usable_lba);
/* Check if First and Last usable LBA makes sense */
if (lu < fu || fu > lastlba || lu > lastlba) {
DBG(DEBUG_LOWPROBE, printf(
"GPT->{First,Last}UsableLBA out of range\n"));
return NULL;
}
/* The header has to be outside usable range */
if (fu < lba && lba < lu) {
DBG(DEBUG_LOWPROBE, printf("GPT header is inside usable area\n"));
return NULL;
}
/* Size of blocks with GPT entries */
esz = le32_to_cpu(h->num_partition_entries) *
le32_to_cpu(h->sizeof_partition_entry);
if (!esz) {
DBG(DEBUG_LOWPROBE, printf("GPT entries undefined\n"));
return NULL;
}
/* The header seems valid, save it
* (we don't care about zeros in hdr->reserved2 area) */
memcpy(hdr, h, sizeof(*h));
h = hdr;
/* Read GPT entries */
*ents = (struct gpt_entry *) get_lba_buffer(pr,
le64_to_cpu(h->partition_entries_lba), esz);
if (!*ents) {
DBG(DEBUG_LOWPROBE, printf("GPT entries unreadable\n"));
return NULL;
}
/* Validate entries */
crc = count_crc32((unsigned char *) *ents, esz);
if (crc != le32_to_cpu(h->partition_entry_array_crc32)) {
DBG(DEBUG_LOWPROBE, printf("GPT entries corrupted\n"));
return NULL;
}
return h;
}
static int probe_gpt_pt(blkid_probe pr,
const struct blkid_idmag *mag __attribute__((__unused__)))
{
uint64_t lastlba = 0, lba;
struct gpt_header hdr, *h;
struct gpt_entry *e;
blkid_parttable tab = NULL;
blkid_partlist ls;
uint64_t fu, lu;
uint32_t ssf, i;
efi_guid_t guid;
if (last_lba(pr, &lastlba))
goto nothing;
if (!is_pmbr_valid(pr))
goto nothing;
h = get_gpt_header(pr, &hdr, &e, (lba = GPT_PRIMARY_LBA), lastlba);
if (!h)
h = get_gpt_header(pr, &hdr, &e, (lba = lastlba), lastlba);
if (!h)
goto nothing;
blkid_probe_use_wiper(pr, lba * blkid_probe_get_size(pr), 8);
if (blkid_probe_set_magic(pr, lba << 9,
sizeof(GPT_HEADER_SIGNATURE_STR) - 1,
(unsigned char *) GPT_HEADER_SIGNATURE_STR))
goto err;
if (blkid_partitions_need_typeonly(pr))
/* caller does not ask for details about partitions */
return 0;
ls = blkid_probe_get_partlist(pr);
if (!ls)
goto err;
tab = blkid_partlist_new_parttable(ls, "gpt", lba << 9);
if (!tab)
goto err;
guid = h->disk_guid;
swap_efi_guid(&guid);
blkid_parttable_set_id(tab, (const unsigned char *) &guid);
ssf = blkid_probe_get_sectorsize(pr) / 512;
fu = le64_to_cpu(h->first_usable_lba);
lu = le64_to_cpu(h->last_usable_lba);
for (i = 0; i < le32_to_cpu(h->num_partition_entries); i++, e++) {
blkid_partition par;
uint64_t start = le64_to_cpu(e->starting_lba);
uint64_t size = le64_to_cpu(e->ending_lba) -
le64_to_cpu(e->starting_lba) + 1ULL;
/* 00000000-0000-0000-0000-000000000000 entry */
if (!guidcmp(e->partition_type_guid, GPT_UNUSED_ENTRY_GUID)) {
blkid_partlist_increment_partno(ls);
continue;
}
/* the partition has to inside usable range */
if (start < fu || start + size - 1 > lu) {
DBG(DEBUG_LOWPROBE, printf(
"GPT entry[%d] overflows usable area - ignore\n",
i));
blkid_partlist_increment_partno(ls);
continue;
}
par = blkid_partlist_add_partition(ls, tab,
start * ssf, size * ssf);
if (!par)
goto err;
blkid_partition_set_utf8name(par,
(unsigned char *) e->partition_name,
sizeof(e->partition_name), BLKID_ENC_UTF16LE);
guid = e->unique_partition_guid;
swap_efi_guid(&guid);
blkid_partition_set_uuid(par, (const unsigned char *) &guid);
guid = e->partition_type_guid;
swap_efi_guid(&guid);
blkid_partition_set_type_uuid(par, (const unsigned char *) &guid);
blkid_partition_set_flags(par, e->attributes);
}
return 0;
nothing:
return 1;
err:
return -1;
}
const struct blkid_idinfo gpt_pt_idinfo =
{
.name = "gpt",
.probefunc = probe_gpt_pt,
.minsz = 1024 * 1440 + 1, /* ignore floppies */
/*
* It would be possible to check for DOS signature (0xAA55), but
* unfortunately almost all EFI GPT implemenations allow to optionaly
* skip the legacy MBR. We follows this behavior and MBR is optional.
* See is_valid_pmbr().
*
* It means we have to always call probe_gpt_pt().
*/
.magics = BLKID_NONE_MAGIC
};
