New option: -s
. Makes the 64-bit alpha checksum magically contain an embedded 16-bit Sun (NetBSD/sparc) compatible magic number and checksum. This is the last piece in the "boot one disk from alpha, sun, and i386" problem. . And for those who told me this had been done before, :-P. It turns out, it was only done in the collective sense by multi-disk distributions.
This commit is contained in:
ross
parent
33630db000
commit
9ff31ad0f5
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@ -1,4 +1,34 @@
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/* $NetBSD: installboot.c,v 1.16 1999/06/14 23:55:29 cgd Exp $ */
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/* $NetBSD: installboot.c,v 1.17 1999/09/19 03:19:00 ross Exp $ */
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/*
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* Copyright (c) 1999 Ross Harvey. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Ross Harvey
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* for the NetBSD Project.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1999 Christopher G. Demetriou. All rights reserved.
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@ -33,6 +63,7 @@
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#include <sys/param.h> /* XXX for roundup, howmany */
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#include <sys/stat.h>
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#include <sys/disklabel.h>
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#include <dev/sun/disklabel.h>
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#include <assert.h>
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#include <err.h>
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#include <fcntl.h>
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@ -43,11 +74,14 @@
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static void usage(void);
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static void clr_bootstrap(const char *disk);
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void check_sparc(const struct boot_block * const);
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static u_int16_t compute_sparc(const u_int16_t *);
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static void sun_bootstrap(struct boot_block * const);
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static void set_bootstrap(const char *disk, const char *bootstrap);
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extern char *__progname;
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int verbose, nowrite;
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int sunflag, verbose, nowrite;
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static void
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usage()
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@ -66,16 +100,24 @@ main(int argc, char **argv)
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clearflag = verbose = nowrite = 0;
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while ((c = getopt(argc, argv, "cnv")) != -1) {
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while ((c = getopt(argc, argv, "cnsv")) != -1) {
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switch (c) {
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case 'c':
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/* Clear any existing boot block */
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if (sunflag)
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goto argdeath;
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clearflag = 1;
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break;
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case 'n':
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/* Do not actually write the boot file */
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nowrite = 1;
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break;
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case 's':
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/* Magically arrange for the Sun checksum overlay */
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if (clearflag)
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goto argdeath;
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sunflag = 1;
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break;
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case 'v':
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/* Chat */
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verbose = 1;
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@ -109,6 +151,8 @@ main(int argc, char **argv)
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set_bootstrap(disk, bootstrap);
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exit(EXIT_SUCCESS);
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argdeath:
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errx(EXIT_FAILURE, "incompatible options");
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}
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static void
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@ -221,6 +265,9 @@ set_bootstrap(const char *disk, const char *bootstrap)
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else if (rv != sizeof bb)
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errx(EXIT_FAILURE, "read %s: short read", disk);
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if (sunflag)
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check_sparc(&bb);
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/* fill in the updated boot block fields, and checksum boot block */
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bb.bb_secsize = howmany(bootstrapsb.st_size, BOOT_BLOCK_BLOCKSIZE);
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bb.bb_secstart = 1;
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@ -236,6 +283,9 @@ set_bootstrap(const char *disk, const char *bootstrap)
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(unsigned long long)bb.bb_cksum);
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}
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if (sunflag)
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sun_bootstrap(&bb);
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if (nowrite) {
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if (verbose)
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fprintf(stderr, "not writing\n");
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@ -264,3 +314,97 @@ set_bootstrap(const char *disk, const char *bootstrap)
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done:
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(void)close(diskfd);
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}
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/*
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* The Sun and alpha checksums overlay, and the Sun magic number also
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* overlays the alpha checksum. Fortunately, there are a set of identity
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* transformations for the Sun checksum that can fit within bits of the
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* alpha checksum that are not overlayed. Add to the xor and algebra
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* magic a bit of carry-blocking magic, and everything Just Works.
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*
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* A: 511 510 509 508 507 506 505 504
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* S: 510 511 508 509 506 507 504 505
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* 63 : : : 32:31 : : : 0
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* | : : : \:| : : : |
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* 7654321076543210765432107654321076543210765432107654321076543210
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* |-- sparc --||-- sparc --|
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* |-- checksum --||-- magic --|
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* |----------------------- alpha checksum -----------------------|
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* 1011111011011010
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* b e d a
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*/
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static void
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sun_bootstrap(struct boot_block * const bb)
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{
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# define BB_ADJUST_OFFSET 64
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u_int16_t sunsum, old_3, bb16[256];
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/*
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* Theory: the alpha checksum is adjusted so bits 47:32 add up
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* to the Sun magic number. Then, another adjustment is computed
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* so bits 63:48 add up to the Sun checksum. This changes the Sun
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* checksum, however, so compensating entries are made in bits
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* 15:0 to restore the original Sun value. This changes the alpha
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* value, but only in bits that don't overlay.
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*
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* A new carry (or lost carry) out of bit 31 would break things,
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* so prearrange for the alpha 31:16 bits to be 01010101...
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*
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* Note: using memcpy(3) instead of a union as a strict c89/c9x
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* conformance experiment and to avoid a public interface delta.
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*/
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assert(sizeof bb16 == sizeof *bb);
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memcpy(bb16, bb, sizeof bb16);
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bb16[BB_ADJUST_OFFSET + 1] = 0x5555 - bb16[253]; /* carry trap */
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memcpy(bb, bb16, sizeof bb16);
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CHECKSUM_BOOT_BLOCK(bb, &bb->bb_cksum);
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memcpy(bb16, bb, sizeof bb16);
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/*
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* Make alpha checksum <47:32> come out to the sun magic.
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*/
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bb16[BB_ADJUST_OFFSET + 2] = htons(SUN_DKMAGIC) - bb16[254];
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memcpy(bb, bb16, sizeof bb16);
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CHECKSUM_BOOT_BLOCK(bb, &bb->bb_cksum);
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memcpy(bb16, bb, sizeof bb16);
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sunsum = compute_sparc(bb16); /* this is the final value */
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/*
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* Arrange to have alpha 63:48 add up to the sparc checksum.
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*/
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old_3 = bb16[BB_ADJUST_OFFSET + 3];
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bb16[BB_ADJUST_OFFSET + 3] = sunsum - bb16[255];
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/*
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* The sparc checksum has changed again to a third value. Modify
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* the alpha 15:0 bits to restore the previous sparc checksum
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* that we went to all the trouble to generate.
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*/
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bb16[BB_ADJUST_OFFSET + 0] ^= (old_3 ^ bb16[BB_ADJUST_OFFSET + 3]);
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memcpy(bb, bb16, sizeof bb16);
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CHECKSUM_BOOT_BLOCK(bb, &bb->bb_cksum);
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if (verbose)
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printf("final harmonized checksum: %016lx\n", bb->bb_cksum);
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}
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void
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check_sparc(const struct boot_block * const bb)
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{
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u_int16_t bb16[256];
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const char * const wmsg = "warning, initial sparc %s 0x%04x invalid,"
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" expected 0x%04x";
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memcpy(bb16, bb, sizeof bb16);
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if (compute_sparc(bb16) != bb16[255])
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warnx(wmsg, "checksum", bb16[255], compute_sparc(bb16));
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if (bb16[254] != htons(SUN_DKMAGIC))
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warnx(wmsg, "magic number", bb16[254], htons(SUN_DKMAGIC));
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}
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static u_int16_t
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compute_sparc(const u_int16_t *bb16)
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{
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u_int16_t i, s = 0;
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for (i = 0; i < 255; ++i)
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s ^= bb16[i];
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return s;
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}
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