NetBSD-5.0.2/sys/arch/acorn32/stand/lib/riscospart.c
/* $NetBSD: riscospart.c,v 1.2 2006/06/25 21:32:41 christos Exp $ */
/*-
* Copyright (c) 2006 Ben Harris
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright (c) 1995 Mark Brinicombe
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/disklabel.h>
#include <sys/disklabel_acorn.h>
#include <lib/libsa/stand.h>
#include "riscospart.h"
/*
* This function should be shared between here,
* sys/arch/arm/arm/disksubr_acorn.c, and
* sys/fs/filecorefs/filecore_utils.c, rather than being copied.
*/
/*
* static int filecore_checksum(u_char *bootblock)
*
* Calculates the filecore boot block checksum. This is used to validate
* a filecore boot block on the disk. If a boot block is validated then
* it is used to locate the partition table. If the boot block is not
* validated, it is assumed that the whole disk is NetBSD.
*
* The basic algorithm is:
*
* for (each byte in block, excluding checksum) {
* sum += byte;
* if (sum > 255)
* sum -= 255;
* }
*
* That's equivalent to summing all of the bytes in the block
* (excluding the checksum byte, of course), then calculating the
* checksum as "cksum = sum - ((sum - 1) / 255) * 255)". That
* expression may or may not yield a faster checksum function,
* but it's easier to reason about.
*
* Note that if you have a block filled with bytes of a single
* value "X" (regardless of that value!) and calculate the cksum
* of the block (excluding the checksum byte), you will _always_
* end up with a checksum of X. (Do the math; that can be derived
* from the checksum calculation function!) That means that
* blocks which contain bytes which all have the same value will
* always checksum properly. That's a _very_ unlikely occurence
* (probably impossible, actually) for a valid filecore boot block,
* so we treat such blocks as invalid.
*/
static int
filecore_checksum(u_char *bootblock)
{
u_char byte0, accum_diff;
u_int sum;
int i;
sum = 0;
accum_diff = 0;
byte0 = bootblock[0];
/*
* Sum the contents of the block, keeping track of whether
* or not all bytes are the same. If 'accum_diff' ends up
* being zero, all of the bytes are, in fact, the same.
*/
for (i = 0; i < 511; ++i) {
sum += bootblock[i];
accum_diff |= bootblock[i] ^ byte0;
}
/*
* Check to see if the checksum byte is the same as the
* rest of the bytes, too. (Note that if all of the bytes
* are the same except the checksum, a checksum compare
* won't succeed, but that's not our problem.)
*/
accum_diff |= bootblock[i] ^ byte0;
/* All bytes in block are the same; call it invalid. */
if (accum_diff == 0)
return (-1);
return (sum - ((sum - 1) / 255) * 255);
}
int
getdisklabel_acorn(struct open_file *f, struct disklabel *lp)
{
size_t rsize;
int err;
char *buf;
struct filecore_bootblock *bb;
daddr_t labelsect;
char *msg;
buf = alloc(DEV_BSIZE);
err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ,
FILECORE_BOOT_SECTOR, DEV_BSIZE, buf, &rsize);
if (err != 0) goto out;
bb = (struct filecore_bootblock *) buf;
if (bb->checksum == filecore_checksum((u_char *)bb)) {
if (bb->partition_type == PARTITION_FORMAT_RISCBSD)
labelsect = (daddr_t)bb->partition_cyl_low *
bb->heads * bb->secspertrack + LABELSECTOR;
else {
err = EUNLAB;
goto out;
}
} else
labelsect = LABELSECTOR;
err = DEV_STRATEGY(f->f_dev)(f->f_devdata, F_READ,
labelsect, DEV_BSIZE, buf, &rsize);
if (err != 0) goto out;
msg = getdisklabel(buf, lp);
if (msg) {
printf("%s\n", msg);
err = ERDLAB;
}
out:
dealloc(buf, DEV_BSIZE);
return err;
}