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Diffstat (limited to '')
| -rw-r--r-- | libblkid/gpt.c | 412 |
1 files changed, 412 insertions, 0 deletions
diff --git a/libblkid/gpt.c b/libblkid/gpt.c new file mode 100644 index 000000000..7288d683e --- /dev/null +++ b/libblkid/gpt.c @@ -0,0 +1,412 @@ +/* + * 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 +}; + |