ref: a3f2d6d23ed1be69fee607bdedadc0438fd01305
dir: /sys/src/cmd/ext4srv/ext4_mbr.c/
#include "ext4_config.h" #include "ext4_types.h" #include "ext4_misc.h" #include "ext4_debug.h" #include "ext4_mbr.h" #define MBR_SIGNATURE 0xAA55 #pragma pack on struct ext4_part_entry { u8int status; u8int chs1[3]; u8int type; u8int chs2[3]; u32int first_lba; u32int sectors; }; struct ext4_mbr { u8int bootstrap[442]; u32int disk_id; struct ext4_part_entry part_entry[4]; u16int signature; }; #pragma pack off int ext4_mbr_scan(struct ext4_blockdev *parent, struct ext4_mbr_bdevs *bdevs) { int r; usize i; ext4_dbg(DEBUG_MBR, DBG_INFO "ext4_mbr_scan\n"); memset(bdevs, 0, sizeof(struct ext4_mbr_bdevs)); r = ext4_block_init(parent); if (r != 0) return r; r = ext4_block_readbytes(parent, 0, parent->bdif->ph_bbuf, 512); if (r != 0) { goto blockdev_fini; } const struct ext4_mbr *mbr = (void *)parent->bdif->ph_bbuf; if (to_le16(mbr->signature) != MBR_SIGNATURE) { ext4_dbg(DEBUG_MBR, DBG_ERROR "ext4_mbr_scan: unknown " "signature: 0x%x\n", to_le16(mbr->signature)); werrstr(Enotfound); r = -1; goto blockdev_fini; } /*Show bootstrap code*/ ext4_dbg(DEBUG_MBR, "mbr_part: bootstrap:"); for (i = 0; i < sizeof(mbr->bootstrap); ++i) { if (!(i & 0xF)) ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n"); ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "%02x, ", mbr->bootstrap[i]); } ext4_dbg(DEBUG_MBR | DEBUG_NOPREFIX, "\n\n"); for (i = 0; i < 4; ++i) { const struct ext4_part_entry *pe = &mbr->part_entry[i]; ext4_dbg(DEBUG_MBR, "mbr_part: %d\n", (int)i); ext4_dbg(DEBUG_MBR, "\tstatus: 0x%x\n", pe->status); ext4_dbg(DEBUG_MBR, "\ttype 0x%x:\n", pe->type); ext4_dbg(DEBUG_MBR, "\tfirst_lba: 0x%ux\n", pe->first_lba); ext4_dbg(DEBUG_MBR, "\tsectors: 0x%ux\n", pe->sectors); if (!pe->sectors) continue; /*Empty entry*/ if (pe->type != 0x83) continue; /*Unsupported entry. 0x83 - linux native*/ bdevs->partitions[i].bdif = parent->bdif; bdevs->partitions[i].part_offset = (u64int)pe->first_lba * parent->bdif->ph_bsize; bdevs->partitions[i].part_size = (u64int)pe->sectors * parent->bdif->ph_bsize; } blockdev_fini: ext4_block_fini(parent); return r; } int ext4_mbr_write(struct ext4_blockdev *parent, struct ext4_mbr_parts *parts, u32int disk_id) { int r; u64int disk_size; u32int division_sum = parts->division[0] + parts->division[1] + parts->division[2] + parts->division[3]; if (division_sum > 100) { werrstr(Einval); return -1; } ext4_dbg(DEBUG_MBR, DBG_INFO "ext4_mbr_write\n"); r = ext4_block_init(parent); if (r != 0) return r; disk_size = parent->part_size; /*Calculate CHS*/ u32int k = 16; while ((k < 256) && ((disk_size / parent->bdif->ph_bsize / k / 63) > 1024)) k *= 2; if (k == 256) --k; const u32int cyl_size = parent->bdif->ph_bsize * 63 * k; const u32int cyl_count = disk_size / cyl_size; struct ext4_mbr *mbr = (void *)parent->bdif->ph_bbuf; memset(mbr, 0, sizeof(struct ext4_mbr)); mbr->disk_id = disk_id; u32int cyl_it = 0; for (int i = 0; i < 4; ++i) { u32int cyl_part = cyl_count * parts->division[i] / 100; if (!cyl_part) continue; u32int part_start = cyl_it * cyl_size; u32int part_size = cyl_part * cyl_size; if (i == 0) { part_start += 63; part_size -= 63 * parent->bdif->ph_bsize; } u32int cyl_end = cyl_part + cyl_it - 1; mbr->part_entry[i].status = 0; mbr->part_entry[i].chs1[0] = i ? 0 : 1;; mbr->part_entry[i].chs1[1] = ((cyl_it >> 2) & 0xC0) + 1; mbr->part_entry[i].chs1[2] = cyl_it & 0xFF; mbr->part_entry[i].type = 0x83; mbr->part_entry[i].chs2[0] = k - 1; mbr->part_entry[i].chs2[1] = ((cyl_end >> 2) & 0xC0) + 63; mbr->part_entry[i].chs2[2] = cyl_end & 0xFF; mbr->part_entry[i].first_lba = part_start; mbr->part_entry[i].sectors = part_size / parent->bdif->ph_bsize; cyl_it += cyl_part; } mbr->signature = MBR_SIGNATURE; r = ext4_block_writebytes(parent, 0, parent->bdif->ph_bbuf, 512); if (r != 0) goto blockdev_fini; blockdev_fini: ext4_block_fini(parent); return r; }