/* pi_begin() - validate and and get proper iterator for a disk described by di */
struct part_iter *pi_begin(const struct disk_info *di, int flags)
{
int gptprot, ret = -1;
struct part_iter *iter;
struct disk_dos_mbr *mbr = NULL;
struct disk_gpt_header *gpth = NULL;
struct disk_gpt_part_entry *gptl = NULL;
/* Preallocate iterator */
if (!(iter = pi_alloc()))
goto bail;
/* Read MBR */
if (!(mbr = disk_read_sectors(di, 0, 1))) {
error("Couldn't read the first disk sector.");
goto bail;
}
/* Check for MBR magic */
if (mbr->sig != disk_mbr_sig_magic) {
warn("No MBR magic, treating disk as raw.");
/* looks like RAW */
ret = pi_ctor(iter, di, flags);
goto bail;
}
/* Check for GPT protective MBR */
gptprot = 0;
for (size_t i = 0; i < 4; i++)
gptprot |= (mbr->table[i].ostype == 0xEE);
if (gptprot && !(flags & PIF_PREFMBR)) {
if (!(gpth = disk_read_sectors(di, 1, 1))) {
error("Couldn't read potential GPT header.");
goto bail;
}
}
if (gpth && gpth->rev.uint32 == 0x00010000 &&
!memcmp(gpth->sig, disk_gpt_sig_magic, sizeof gpth->sig)) {
/* looks like GPT v1.0 */
uint64_t gpt_loff; /* offset to GPT partition list in sectors */
uint64_t gpt_lsiz; /* size of GPT partition list in bytes */
uint64_t gpt_lcnt; /* size of GPT partition in sectors */
#ifdef DEBUG
dprintf("Looks like a GPT v1.0 disk.\n");
disk_gpt_header_dump(gpth);
#endif
/* Verify checksum, fallback to backup, then bail if invalid */
if (gpt_check_hdr_crc(di, &gpth))
goto bail;
gpt_loff = gpth->lba_table;
gpt_lsiz = (uint64_t)gpth->part_size * gpth->part_count;
gpt_lcnt = (gpt_lsiz + di->bps - 1) / di->bps;
/*
* disk_read_sectors allows reading of max 255 sectors, so we use
* it as a sanity check base. EFI doesn't specify max (AFAIK).
* Apart from that, some extensive sanity checks.
*/
if (!(flags & PIF_RELAX) && (
!gpt_loff || !gpt_lsiz || gpt_lcnt > 255u ||
gpth->lba_first_usable > gpth->lba_last_usable ||
!sane(gpt_loff, gpt_lcnt) ||
gpt_loff + gpt_lcnt > gpth->lba_first_usable ||
!sane(gpth->lba_last_usable, gpt_lcnt) ||
gpth->lba_last_usable + gpt_lcnt >= gpth->lba_alt ||
gpth->lba_alt >= di->lbacnt ||
gpth->part_size < sizeof *gptl)) {
error("Invalid GPT header's values.");
goto bail;
}
if (!(gptl = disk_read_sectors(di, gpt_loff, gpt_lcnt))) {
error("Couldn't read GPT partition list.");
goto bail;
}
/* Check array checksum(s). */
if (!valid_crc(gpth->table_chksum, (const uint8_t *)gptl, (unsigned int)gpt_lsiz)) {
warn("Checksum of the main GPT partition list is invalid, trying backup.");
free(gptl);
/* secondary array directly precedes secondary header */
if (!(gptl = disk_read_sectors(di, gpth->lba_alt - gpt_lcnt, gpt_lcnt))) {
error("Couldn't read backup GPT partition list.");
goto bail;
}
if (!valid_crc(gpth->table_chksum, (const uint8_t *)gptl, gpt_lsiz)) {
error("Checksum of the backup GPT partition list is invalid, giving up.");
goto bail;
}
}
/* looks like GPT */
ret = pi_gpt_ctor(iter, di, flags, gpth, gptl);
} else {
/* looks like MBR */
ret = pi_dos_ctor(iter, di, flags, mbr);
}
bail:
if (ret < 0)
free(iter);
free(mbr);
free(gpth);
free(gptl);
return iter;
}
/* pi_begin() - validate and and get proper iterator for a disk described by di */
struct part_iter *pi_begin(const struct disk_info *di, int flags)
{
int isgpt = 0, ret = -1;
struct part_iter *iter;
struct disk_dos_mbr *mbr = NULL;
struct disk_gpt_header *gpth = NULL;
struct disk_gpt_part_entry *gptl = NULL;
/* Preallocate iterator */
if (!(iter = pi_alloc()))
goto out;
/* Read MBR */
if (!(mbr = disk_read_sectors(di, 0, 1))) {
error("Unable to read the first disk sector.");
goto out;
}
/* Check for MBR magic */
if (mbr->sig != disk_mbr_sig_magic) {
warn("No MBR magic, treating disk as raw.");
/* looks like RAW */
ret = pi_ctor(iter, di, flags);
goto out;
}
/* Check for GPT protective MBR */
for (size_t i = 0; i < 4; i++)
isgpt |= (mbr->table[i].ostype == 0xEE);
isgpt = isgpt && !(flags & PIF_PREFMBR);
/* Try to read GPT header */
if (isgpt) {
gpth = try_gpt_hdr(di, 0);
if (!gpth)
/*
* this read might fail if bios reports different disk size (different vm/pc)
* not much we can do here to avoid it
*/
gpth = try_gpt_hdr(di, 1);
if (!gpth)
goto out;
}
if (gpth && gpth->rev.uint32 == 0x00010000 &&
!memcmp(gpth->sig, disk_gpt_sig_magic, sizeof gpth->sig)) {
/* looks like GPT v1.0 */
#ifdef DEBUG
dprintf("Looks like a GPT v1.0 disk.\n");
disk_gpt_header_dump(gpth);
#endif
if (notsane_gpt_hdr(di, gpth, flags)) {
error("GPT header values are corrupted.");
goto out;
}
gptl = try_gpt_list(di, gpth, 0);
if (!gptl)
gptl = try_gpt_list(di, gpth, 1);
if (!gptl)
goto out;
/* looks like GPT */
ret = pi_gpt_ctor(iter, di, flags, gpth, gptl);
} else {
/* looks like MBR */
ret = pi_dos_ctor(iter, di, flags, mbr);
}
out:
if (ret < 0) {
free(iter);
iter = NULL;
}
free(mbr);
free(gpth);
free(gptl);
return iter;
}