1 /* $NetBSD: riscospart.c,v 1.3 2010/11/25 13:45:17 skrll Exp $ */ 2 3 /*- 4 * Copyright (c) 2006 Ben Harris 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 /* 31 * Copyright (c) 1995 Mark Brinicombe 32 * All rights reserved. 33 * 34 * Redistribution and use in source and binary forms, with or without 35 * modification, are permitted provided that the following conditions 36 * are met: 37 * 1. Redistributions of source code must retain the above copyright 38 * notice, this list of conditions and the following disclaimer. 39 * 2. Redistributions in binary form must reproduce the above copyright 40 * notice, this list of conditions and the following disclaimer in the 41 * documentation and/or other materials provided with the distribution. 42 * 3. All advertising materials mentioning features or use of this software 43 * must display the following acknowledgement: 44 * This product includes software developed by the University of 45 * California, Berkeley and its contributors. 46 * 4. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 */ 62 63 #include <sys/types.h> 64 #include <sys/param.h> 65 #include <sys/disklabel.h> 66 #include <sys/disklabel_acorn.h> 67 68 #include <lib/libsa/stand.h> 69 70 #include "riscospart.h" 71 72 /* 73 * This function should be shared between here, 74 * sys/arch/arm/arm/disksubr_acorn.c, and 75 * sys/fs/filecorefs/filecore_utils.c, rather than being copied. 76 */ 77 /* 78 * static int filecore_checksum(u_char *bootblock) 79 * 80 * Calculates the filecore boot block checksum. This is used to validate 81 * a filecore boot block on the disk. If a boot block is validated then 82 * it is used to locate the partition table. If the boot block is not 83 * validated, it is assumed that the whole disk is NetBSD. 84 * 85 * The basic algorithm is: 86 * 87 * for (each byte in block, excluding checksum) { 88 * sum += byte; 89 * if (sum > 255) 90 * sum -= 255; 91 * } 92 * 93 * That's equivalent to summing all of the bytes in the block 94 * (excluding the checksum byte, of course), then calculating the 95 * checksum as "cksum = sum - ((sum - 1) / 255) * 255)". That 96 * expression may or may not yield a faster checksum function, 97 * but it's easier to reason about. 98 * 99 * Note that if you have a block filled with bytes of a single 100 * value "X" (regardless of that value!) and calculate the cksum 101 * of the block (excluding the checksum byte), you will _always_ 102 * end up with a checksum of X. (Do the math; that can be derived 103 * from the checksum calculation function!) That means that 104 * blocks which contain bytes which all have the same value will 105 * always checksum properly. That's a _very_ unlikely occurence 106 * (probably impossible, actually) for a valid filecore boot block, 107 * so we treat such blocks as invalid. 108 */ 109 static int 110 filecore_checksum(u_char *bootblock) 111 { 112 u_char byte0, accum_diff; 113 u_int sum; 114 int i; 115 116 sum = 0; 117 accum_diff = 0; 118 byte0 = bootblock[0]; 119 120 /* 121 * Sum the contents of the block, keeping track of whether 122 * or not all bytes are the same. If 'accum_diff' ends up 123 * being zero, all of the bytes are, in fact, the same. 124 */ 125 for (i = 0; i < 511; ++i) { 126 sum += bootblock[i]; 127 accum_diff |= bootblock[i] ^ byte0; 128 } 129 130 /* 131 * Check to see if the checksum byte is the same as the 132 * rest of the bytes, too. (Note that if all of the bytes 133 * are the same except the checksum, a checksum compare 134 * won't succeed, but that's not our problem.) 135 */ 136 accum_diff |= bootblock[i] ^ byte0; 137 138 /* All bytes in block are the same; call it invalid. */ 139 if (accum_diff == 0) 140 return (-1); 141 142 return (sum - ((sum - 1) / 255) * 255); 143 } 144 145 146 int 147 getdisklabel_acorn(struct open_file *f, struct disklabel *lp) 148 { 149 size_t rsize; 150 int err; 151 char *buf; 152 struct filecore_bootblock *bb; 153 daddr_t labelsect; 154 char *msg; 155 156 buf = alloc(DEV_BSIZE); 157 err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ, 158 FILECORE_BOOT_SECTOR, DEV_BSIZE, buf, &rsize); 159 if (err != 0) goto out; 160 bb = (struct filecore_bootblock *) buf; 161 if (bb->checksum == filecore_checksum((u_char *)bb)) { 162 if (bb->partition_type == PARTITION_FORMAT_RISCBSD) 163 labelsect = ((bb->partition_cyl_high << 8) + bb->partition_cyl_low) * 164 bb->heads * bb->secspertrack + LABELSECTOR; 165 else { 166 err = EUNLAB; 167 goto out; 168 } 169 } else 170 labelsect = LABELSECTOR; 171 err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ, 172 labelsect, DEV_BSIZE, buf, &rsize); 173 if (err != 0) goto out; 174 msg = getdisklabel(buf, lp); 175 if (msg) { 176 printf("%s\n", msg); 177 err = ERDLAB; 178 } 179 out: 180 dealloc(buf, DEV_BSIZE); 181 return err; 182 } 183