| 1 | /* ----------------------------------------------------------------------- * |
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| 2 | * |
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| 3 | * Copyright 2009 Pierre-Alexandre Meyer |
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| 4 | * |
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| 5 | * Some parts borrowed from chain.c32: |
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| 6 | * |
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| 7 | * Copyright 2003-2009 H. Peter Anvin - All Rights Reserved |
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| 8 | * Copyright 2009 Intel Corporation; author: H. Peter Anvin |
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| 9 | * |
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| 10 | * This file is part of Syslinux, and is made available under |
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| 11 | * the terms of the GNU General Public License version 2. |
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| 12 | * |
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| 13 | * ----------------------------------------------------------------------- */ |
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| 14 | |
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| 15 | #include <com32.h> |
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| 16 | #include <stdlib.h> |
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| 17 | #include <string.h> |
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| 18 | |
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| 19 | #include <disk/errno_disk.h> |
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| 20 | #include <disk/geom.h> |
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| 21 | #include <disk/read.h> |
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| 22 | #include <disk/util.h> |
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| 23 | #include <disk/common.h> |
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| 24 | |
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| 25 | /* |
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| 26 | * TODO: implement file descriptors to cache metadata (geometry, ...) |
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| 27 | */ |
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| 28 | |
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| 29 | /** |
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| 30 | * read_mbr - return a pointer to a malloced buffer containing the mbr |
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| 31 | * @drive: Drive number |
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| 32 | * @buf: Pre-allocated buffer for output |
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| 33 | * |
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| 34 | * Return the number of sectors read on success or -1 on failure. |
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| 35 | * errno_disk contains the error number. |
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| 36 | **/ |
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| 37 | int read_mbr(int drive, void *buf) |
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| 38 | { |
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| 39 | struct driveinfo drive_info; |
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| 40 | drive_info.disk = drive; |
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| 41 | |
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| 42 | /* MBR: lba = 0, 1 sector */ |
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| 43 | return read_sectors(&drive_info, buf, 0, 1); |
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| 44 | } |
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| 45 | |
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| 46 | /** |
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| 47 | * dev_read - read from a drive |
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| 48 | * @drive: Drive number |
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| 49 | * @buf: Pre-allocated buffer for output |
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| 50 | * @lba: Position to start reading from |
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| 51 | * @sectors: Number of sectors to read |
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| 52 | * |
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| 53 | * High-level routine to read from a hard drive. |
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| 54 | * Return the number of sectors read on success or -1 on failure. |
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| 55 | * errno_disk contains the error number. |
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| 56 | **/ |
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| 57 | int dev_read(int drive, void *buf, unsigned int lba, int sectors) |
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| 58 | { |
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| 59 | struct driveinfo drive_info; |
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| 60 | drive_info.disk = drive; |
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| 61 | |
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| 62 | return read_sectors(&drive_info, buf, lba, sectors); |
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| 63 | } |
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| 64 | |
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| 65 | /** |
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| 66 | * read_sectors - read several sectors from disk |
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| 67 | * @drive_info: driveinfo struct describing the disk |
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| 68 | * @data: Pre-allocated buffer for output |
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| 69 | * @lba: Position to read |
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| 70 | * @sectors: Number of sectors to read |
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| 71 | * |
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| 72 | * Return the number of sectors read on success or -1 on failure. |
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| 73 | * errno_disk contains the error number. |
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| 74 | **/ |
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| 75 | int read_sectors(struct driveinfo *drive_info, void *data, |
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| 76 | const unsigned int lba, const int sectors) |
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| 77 | { |
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| 78 | com32sys_t inreg, outreg; |
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| 79 | struct ebios_dapa *dapa; |
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| 80 | void *buf; |
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| 81 | char *bufp = data; |
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| 82 | int rv = -1; |
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| 83 | |
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| 84 | if (get_drive_parameters(drive_info) == -1) |
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| 85 | return -1; |
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| 86 | |
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| 87 | buf = lmalloc(sectors * SECTOR); |
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| 88 | if (!buf) |
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| 89 | return -1; |
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| 90 | |
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| 91 | dapa = lmalloc(sizeof(*dapa)); |
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| 92 | if (!dapa) |
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| 93 | goto fail; |
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| 94 | |
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| 95 | memset(&inreg, 0, sizeof inreg); |
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| 96 | |
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| 97 | if (drive_info->ebios) { |
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| 98 | dapa->len = sizeof(*dapa); |
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| 99 | dapa->count = sectors; |
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| 100 | dapa->off = OFFS(buf); |
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| 101 | dapa->seg = SEG(buf); |
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| 102 | dapa->lba = lba; |
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| 103 | |
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| 104 | inreg.esi.w[0] = OFFS(dapa); |
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| 105 | inreg.ds = SEG(dapa); |
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| 106 | inreg.edx.b[0] = drive_info->disk; |
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| 107 | inreg.eax.b[1] = 0x42; /* Extended read */ |
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| 108 | } else { |
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| 109 | unsigned int c, h, s; |
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| 110 | |
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| 111 | if (!drive_info->cbios) { // XXX errno |
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| 112 | /* We failed to get the geometry */ |
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| 113 | if (lba) |
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| 114 | goto fail; /* Can only read MBR */ |
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| 115 | |
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| 116 | s = 1; |
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| 117 | h = 0; |
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| 118 | c = 0; |
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| 119 | } else |
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| 120 | lba_to_chs(drive_info, lba, &s, &h, &c); |
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| 121 | |
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| 122 | // XXX errno |
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| 123 | if (s > 63 || h > 256 || c > 1023) |
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| 124 | goto fail; |
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| 125 | |
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| 126 | inreg.eax.w[0] = 0x0201; /* Read one sector */ |
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| 127 | inreg.ecx.b[1] = c & 0xff; |
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| 128 | inreg.ecx.b[0] = s + (c >> 6); |
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| 129 | inreg.edx.b[1] = h; |
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| 130 | inreg.edx.b[0] = drive_info->disk; |
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| 131 | inreg.ebx.w[0] = OFFS(buf); |
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| 132 | inreg.es = SEG(buf); |
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| 133 | } |
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| 134 | |
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| 135 | /* Perform the read */ |
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| 136 | if (int13_retry(&inreg, &outreg)) { |
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| 137 | errno_disk = outreg.eax.b[1]; |
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| 138 | goto fail; /* Give up */ |
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| 139 | } |
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| 140 | |
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| 141 | memcpy(bufp, buf, sectors * SECTOR); |
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| 142 | rv = sectors; |
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| 143 | |
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| 144 | fail: |
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| 145 | lfree(dapa); |
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| 146 | lfree(buf); |
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| 147 | return rv; |
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| 148 | } |
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