1 /* 2 * Hard disk geometry utilities 3 * 4 * Copyright (C) 2012 Red Hat, Inc. 5 * 6 * This work is licensed under the terms of the GNU GPL, version 2 or later. 7 * See the COPYING file in the top-level directory. 8 * 9 * This file incorporates work covered by the following copyright and 10 * permission notice: 11 * 12 * Copyright (c) 2003 Fabrice Bellard 13 * 14 * Permission is hereby granted, free of charge, to any person obtaining a copy 15 * of this software and associated documentation files (the "Software"), to deal 16 * in the Software without restriction, including without limitation the rights 17 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 18 * copies of the Software, and to permit persons to whom the Software is 19 * furnished to do so, subject to the following conditions: 20 * 21 * The above copyright notice and this permission notice shall be included in 22 * all copies or substantial portions of the Software. 23 * 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 27 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 29 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 30 * THE SOFTWARE. 31 */ 32 33 #include "qemu/osdep.h" 34 #include "sysemu/block-backend.h" 35 #include "qapi/qapi-types-block.h" 36 #include "qemu/bswap.h" 37 #include "hw/block/block.h" 38 #include "trace.h" 39 40 struct partition { 41 uint8_t boot_ind; /* 0x80 - active */ 42 uint8_t head; /* starting head */ 43 uint8_t sector; /* starting sector */ 44 uint8_t cyl; /* starting cylinder */ 45 uint8_t sys_ind; /* What partition type */ 46 uint8_t end_head; /* end head */ 47 uint8_t end_sector; /* end sector */ 48 uint8_t end_cyl; /* end cylinder */ 49 uint32_t start_sect; /* starting sector counting from 0 */ 50 uint32_t nr_sects; /* nr of sectors in partition */ 51 } QEMU_PACKED; 52 53 /* try to guess the disk logical geometry from the MSDOS partition table. 54 Return 0 if OK, -1 if could not guess */ 55 static int guess_disk_lchs(BlockBackend *blk, 56 int *pcylinders, int *pheads, int *psectors) 57 { 58 uint8_t buf[BDRV_SECTOR_SIZE]; 59 int i, heads, sectors, cylinders; 60 struct partition *p; 61 uint32_t nr_sects; 62 uint64_t nb_sectors; 63 64 blk_get_geometry(blk, &nb_sectors); 65 66 if (blk_pread(blk, 0, buf, BDRV_SECTOR_SIZE) < 0) { 67 return -1; 68 } 69 /* test msdos magic */ 70 if (buf[510] != 0x55 || buf[511] != 0xaa) { 71 return -1; 72 } 73 for (i = 0; i < 4; i++) { 74 p = ((struct partition *)(buf + 0x1be)) + i; 75 nr_sects = le32_to_cpu(p->nr_sects); 76 if (nr_sects && p->end_head) { 77 /* We make the assumption that the partition terminates on 78 a cylinder boundary */ 79 heads = p->end_head + 1; 80 sectors = p->end_sector & 63; 81 if (sectors == 0) { 82 continue; 83 } 84 cylinders = nb_sectors / (heads * sectors); 85 if (cylinders < 1 || cylinders > 16383) { 86 continue; 87 } 88 *pheads = heads; 89 *psectors = sectors; 90 *pcylinders = cylinders; 91 trace_hd_geometry_lchs_guess(blk, cylinders, heads, sectors); 92 return 0; 93 } 94 } 95 return -1; 96 } 97 98 static void guess_chs_for_size(BlockBackend *blk, 99 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs) 100 { 101 uint64_t nb_sectors; 102 int cylinders; 103 104 blk_get_geometry(blk, &nb_sectors); 105 106 cylinders = nb_sectors / (16 * 63); 107 if (cylinders > 16383) { 108 cylinders = 16383; 109 } else if (cylinders < 2) { 110 cylinders = 2; 111 } 112 *pcyls = cylinders; 113 *pheads = 16; 114 *psecs = 63; 115 } 116 117 void hd_geometry_guess(BlockBackend *blk, 118 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs, 119 int *ptrans) 120 { 121 int cylinders, heads, secs, translation; 122 HDGeometry geo; 123 124 /* Try to probe the backing device geometry, otherwise fallback 125 to the old logic. (as of 12/2014 probing only succeeds on DASDs) */ 126 if (blk_probe_geometry(blk, &geo) == 0) { 127 *pcyls = geo.cylinders; 128 *psecs = geo.sectors; 129 *pheads = geo.heads; 130 translation = BIOS_ATA_TRANSLATION_NONE; 131 } else if (guess_disk_lchs(blk, &cylinders, &heads, &secs) < 0) { 132 /* no LCHS guess: use a standard physical disk geometry */ 133 guess_chs_for_size(blk, pcyls, pheads, psecs); 134 translation = hd_bios_chs_auto_trans(*pcyls, *pheads, *psecs); 135 } else if (heads > 16) { 136 /* LCHS guess with heads > 16 means that a BIOS LBA 137 translation was active, so a standard physical disk 138 geometry is OK */ 139 guess_chs_for_size(blk, pcyls, pheads, psecs); 140 translation = *pcyls * *pheads <= 131072 141 ? BIOS_ATA_TRANSLATION_LARGE 142 : BIOS_ATA_TRANSLATION_LBA; 143 } else { 144 /* LCHS guess with heads <= 16: use as physical geometry */ 145 *pcyls = cylinders; 146 *pheads = heads; 147 *psecs = secs; 148 /* disable any translation to be in sync with 149 the logical geometry */ 150 translation = BIOS_ATA_TRANSLATION_NONE; 151 } 152 if (ptrans) { 153 *ptrans = translation; 154 } 155 trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation); 156 } 157 158 int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs) 159 { 160 return cyls <= 1024 && heads <= 16 && secs <= 63 161 ? BIOS_ATA_TRANSLATION_NONE 162 : BIOS_ATA_TRANSLATION_LBA; 163 } 164