| 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 "qemu/bswap.h" |
| 35 | #include "system/block-backend.h" |
| 36 | #include "qapi/qapi-types-block.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 MS-DOS 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, BDRV_SECTOR_SIZE, buf, 0) < 0) { |
| 67 | return -1; |
| 68 | } |
| 69 | /* test MS-DOS 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 | if (*ptrans == BIOS_ATA_TRANSLATION_AUTO) { |
| 154 | *ptrans = translation; |
| 155 | } else { |
| 156 | /* Defer to the translation specified by the user. */ |
| 157 | translation = *ptrans; |
| 158 | } |
| 159 | } |
| 160 | trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation); |
| 161 | } |
| 162 | |
| 163 | int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs) |
| 164 | { |
| 165 | return cyls <= 1024 && heads <= 16 && secs <= 63 |
| 166 | ? BIOS_ATA_TRANSLATION_NONE |
| 167 | : BIOS_ATA_TRANSLATION_LBA; |
| 168 | } |